Taking the PFI plunge soon

[PJG1173]

Just ordered the vortec v6 marine mpfi intake from flee bay http://www.ebay.com/itm/43L-Vortec-Marine-Intake-Manifold-GM-Volvo-MerCruiser-Marine-Intake-9608-New-/331490477322

I know a couple members here have successfully converted their 7427 to PFI but I cannot find the threads in where they did them. FAST355 comes to mind as one who did the marine intake conversion on a V8. I tried using the search feature and no luck, so if anyone has a link to the threads I would appreciate it.

Edit: I found this, but I am also looking for info specific to the marine intake as there is a lot of conflicting info on the interwebz.
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?303-16197427-PCM-Information-0D&p=2855&viewfull=1#post2855

[dave w]

I have not done a V6 MPFI conversion. I do wonder, would the stock CPI settings work? Attached are a couple $8C files I have from a 95 CPI 4.3 Liter V6. I opened the $8C .bin file using a $OD.xdf to figure out the .bin is actually $8C.

dave w

[brian617]

CPI .bin is a good idea. I've been thinking about using one of these intakes on a 4.3 with a turbo.

[PJG1173]

I have the computer from a 94 s10 blazer CPI in my other truck, not sure if I got the memcal with it or not. I'll have to dig around in my box of goodies. this brings up another question though. looking at the tbi - mpfi doc that 93s10v8 made a while back it shows having to solder a jumper onto the memcal. would that have to be done on the 4.3 cpi memcal or is it even required for a v6 conversion at all?

[dave w]

I have the computer from a 94 s10 blazer CPI in my other truck, not sure if I got the memcal with it or not. I'll have to dig around in my box of goodies. this brings up another question though. looking at the tbi - mpfi doc that 93s10v8 made a while back it shows having to solder a jumper onto the memcal. would that have to be done on the 4.3 cpi memcal or is it even required for a v6 conversion at all?

I'm not sure about the 4.3 CPI cylinder select voltage, that sets up the injector firing sequence. The V6 memcal modification might not be needed, depending on how the injector firing sequence is for CPI. I'm thinking the 4.3 CPI is a poppet valve EFI system that fires all poppet valves at the same time? I'm thinking the V8 memcal mod for MPFI sets up the cylinder select voltage / injector firing sequence for every 4th Distributor Reference Pulse (DRP). Maybe a V6 MPFI system needs the injector firing sequence every 3rd DRP? Maybe the CPI injector firing sequence is every 3rd DRP?

dave w

[PJG1173]

I'm not sure about the 4.3 CPI cylinder select voltage, that sets up the injector firing sequence. The V6 memcal modification might not be needed, depending on how the injector firing sequence is for CPI. I'm thinking the 4.3 CPI is a poppet valve EFI system that fires all poppet valves at the same time? I'm thinking the V8 memcal mod for MPFI sets up the cylinder select voltage / injector firing sequence for every 4th Distributor Reference Pulse (DRP). Maybe a V6 MPFI system needs the injector firing sequence every 3rd DRP? Maybe the CPI injector firing sequence is every 3rd DRP?

dave w

um wow. according to the doc I referenced you are correct its every 4th DRP. looks like I may have to do some more research on batch firing...

[PJG1173]

Ok so I looked a CPI injector up. looks like a single tbi injector with 6 poppet valves attached to it. http://www.oreillyauto.com/site/c/detail/BWD0/27096/02521.oap?year=1994&make=Chevrolet&model=S10%2BBlazer&vi=1060580&ck=Search_fuel+injector_1060580_2378&keyword=fuel+injector

[brian617]

According to ShopKey there is only one power and one ground command from PCM on the early CPI. Looks just like a TBI connector.

http://t3.gstatic.com/images?q=tbn:ANd9GcTj_T056UhgjsEg9FT_nZxdcThzqNhWE _hxuMZQjxaMaVvGchTHOQ

[PJG1173]

Yeah I also found this http://www.thirdgen.org/forums/diy-prom/270266-tbi-guys-its-time-9.html#post4033676

[dave w]

Ok, as a thought, would it be all bad if 6 MPFI injectors all fired at once? I'm not sure about injector impedance, 6 injectors in parallel compared to the single poppet impedance? If the impedance is close, maybe 6 MPFI injectors could be operated by a single CPI injector driver in the '7427 PCM?

6 MPFI injectors that individually measure 16 ohms impedance each, would be 2.67 ohms when connected in parallel. I wonder what the impedance of a 4.3 CPI poppet valve injector measures?

dave w

[PJG1173]

Ok, as a thought, would it be all bad if 6 MPFI injectors all fired at once? I'm not sure about injector impedance, 6 injectors in parallel compared to the single poppet impedance? If the impedance is close, maybe 6 MPFI injectors could be operated by a single CPI injector driver in the '7427 PCM?

6 MPFI injectors that individually measure 16 ohms impedance each, would be 2.67 ohms when connected in parallel. I wonder what the impedance of a 4.3 CPI poppet valve injector measures?

dave w

I would imagine the same as 1 tbi injector. From the pictures it looks like they just cramed a tbi injector in a fancy housing

[dave w]

I wish I had a CPI injector to measure. Maybe someone will help out?

dave w

[PJG1173]

I wish I had a CPI injector to measure. Maybe someone will help out?

dave w

Looks like the local parts store has one in stock. If I have time tomorrow I'll stop by and see if they will let me measure it.

[dave w]

There is the option of using a resistor box (math required) to keep the PCM injector driver happy, if the CPI injector has a different resistance than the 6 MPFI injectors in parallel.

dave w

[1project2many]

I have measured the resistance across the mode selection terminals on a 4.3 CPI memcal. The memcal is set to "6 cylinder PFI mode" which equates to 1.7V at the mode select pin. The 7727/7730 only has one injector driver so V6 apps with the 7727/7730 will fire all six injectors at once. I'll try and research the resistance of the injector today.

[brian617]

The 7727/7730 only has one injector driver so V6 apps with the 7727/7730 will fire all six injectors at once.

Shouldn't the original CPI 4.3 be $OD 7427,6395 etc?

[dave w]

Shouldn't the original CPI 4.3 be $OD 7427,6395 etc?

Yes, that is correct. The one exception I came across was a 4.3 CPI $8C / '7427 in a 1995 S-10 Blazer.

I think, using an unmodified factory (CPI) memcal and unmodified PCM ('7427) would be possible for a V6 MPFI conversion. The injector impedance of the 6 MPFI injectors will need to be selected very carefully.

dave w

[1project2many]

Check wiring diagrams. If the cpi injector wiring includes an "injector sense" loopback wire then the cpi injector impedance is low and the ecm operates in pNh mode.

[Fast355]

Yes, that is correct. The one exception I came across was a 4.3 CPI $8C / '7427 in a 1995 S-10 Blazer.

I think, using an unmodified factory (CPI) memcal and unmodified PCM ('7427) would be possible for a V6 MPFI conversion. The injector impedance of the 6 MPFI injectors will need to be selected very carefully.

dave w

There was actually an underhood flash style blackbox style PCM for the 1995 S-10s with the TBI and CPI 4.3. They used a crank sensor and vortec crab style distributor. There was also an early version in 1992 with an ECM that did not run the transmission.

[brian617]

1project2many, Internal or external of PCM?

[brian617]

There was actually an underhood flash style blackbox style PCM for the 1995 S-10s with the TBI and CPI 4.3. They used a crank sensor and vortec crab style distributor.

Wasn't that just the 95 model TBIs with manual transmission?

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?3922-My-elusively-clandestine-1995-TBI-VCM

[Fast355]

Wasn't that just the 95 model TBIs with manual transmission?

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?3922-My-elusively-clandestine-1995-TBI-VCM

Nope, CPI engines used them too. The first one I ran across was a CPI Oldsmobile Bravada IIRC.

[brian617]

Would have had to been a 96 model to be a Bravada, they didn't make a 95. 96 model uses the same black box PCM as the 96-up Vortec trucks.

[PJG1173]

There was actually an underhood flash style blackbox style PCM for the 1995 S-10s with the TBI and CPI 4.3. They used a crank sensor and vortec crab style distributor. There was also an early version in 1992 with an ECM that did not run the transmission.

I found one of these computers in the JY but from the research I have done I couldn't find any tuning support for them, so I dismissed trying to use one. the donor truck I took this motor out of was a 01 Jimmy, so it still has the crank sensor in it. not sure it the machine shop put the tone wheel on but that should be easy to check.

[PJG1173]

Would have had to been a 96 model to be a Bravada, they didn't make a 95. 96 model uses the same black box PCM as the 96-up Vortec trucks.

I have a digital instrument cluster from a 94 bravada in my 93 s10.

[Nasty-Z]

I have a digital instrument cluster from a 94 bravada in my 93 s10.

Yes , 1991-1994 , then 1996 to 2004 . No 1995 Bravada's.

I too have a Bravada digital cluster in my '92 S10 :happy:

TOM

[dave w]

Check wiring diagrams. If the cpi injector wiring includes an "injector sense" loopback wire then the cpi injector impedance is low and the ecm operates in pNh mode.

I'll check my schematics later today.

Mathematically it's possible to get 6 MPFI injectors to match the impedance of one CPI injector, see example below. By adding a 12 ohm resistor across both the terminals of 16 ohm MPFI injector yields an impedance of about 6.85 ohms. The second example shows the impedance of 6 MPFI injectors with an impedance of 6.85 ohms, yielding a parallel impedance of 1.14 ohms. Without an actual measurement of the impedance of a CPI injector / MPFI injector, I'm not sure what the actual resistor box values will be.

I think it is a good plan to build an MPFI system with abundant / affordable parts, and well documented .xdf / .adx files!:thumbsup:

dave w

[Fast355]

Would have had to been a 96 model to be a Bravada, they didn't make a 95. 96 model uses the same black box PCM as the 96-up Vortec trucks.

It was not a 96+, it was the older square body.

[Fast355]

It was not a 96+, it was the older square body.

This is a picture of one of those setups. Must have been a really late 94. I just had the timing cover off of a 1994 Blazer that had never been disturbed and had a block off plug in place of the crank sensor.

http://i407.photobucket.com/albums/pp153/AWD_V8/Jimmy/pcm-location.jpg (http://s407.photobucket.com/user/AWD_V8/media/Jimmy/pcm-location.jpg.html)

[1project2many]

Use 7427 application... 1993-94. 95 was last year for CPI, 96 introduced sequential version.

[brian617]

I'm betting it has to be the new body style 94-95 s10 pickups and the 95 blazer and jimmy. Forgot they put the CPI in the 94-95 s10 4x4s...

[brian617]

I think it is a good plan to build an MPFI system with abundant / affordable parts, and well documented .xdf / .adx files!:thumbsup:

dave w

I agree, $OD would be the best CPI .bin to start with.

[PJG1173]

I'll check my schematics later today.

Mathematically it's possible to get 6 MPFI injectors to match the impedance of one CPI injector, see example below. By adding a 12 ohm resistor across both the terminals of 16 ohm MPFI injector yields an impedance of about 6.85 ohms. The second example shows the impedance of 6 MPFI injectors with an impedance of 6.85 ohms, yielding a parallel impedance of 1.14 ohms. Without an actual measurement of the impedance of a CPI injector / MPFI injector, I'm not sure what the actual resistor box values will be.

I think it is a good plan to build an MPFI system with abundant / affordable parts, and well documented .xdf / .adx files!:thumbsup:

dave w

I agree totally. the more I think about it the CPI firing strategy is the way to go on this vise batch firing 2 banks of injectors. Obviously the CPI motors worked so no need to reinvent the wheel. this post by 1project2many indicates a variable tuning valve that could be an issue. http://www.gearhead-efi.com/Fuel-Injection/showthread.php?954-Newbie-question-re-mem-cal-compatability-TBI-to-MPFI&p=11352&viewfull=1#post11352

I was thinking along the lines of wiring them in a series/parallel circuit to match the resistance. It might be able to get it close to the correct impedance without using resistors.

[PJG1173]

I agree, $OD would be the best CPI .bin to start with.

I think I have a BBNT memcal at home. finding it may be a problem though I may have used it in by buddies CJ5 304 TBI conversion. might explain why I had to disable the flag for the knock sensor:mad1:

[PJG1173]

interesting reading. so if this article is correct:
-CPI fires injectors 3 times per crank revolution
-The injector driver circuit uses the peak-and-hold method, providing 4 amps to open the injector and about 1 amp to keep it open.
-The resistance specification is 1.9 to 2.1 ohms

http://www.tomorrowstechnician.com/living-under-the-hood-diagnosing-central-port-fuel-injection/

this article seems to support that
The assembly uses a single low impedance (1.5 ohms) "maxi injector"
http://www.automotiveforums.com/t462726-__92__95_cpi_engine_info__.html

and this CPI Vortec 4.3 liter 1.5 +/- .2 ohms
http://www.pirate4x4.com/tech/billavista/PDFs/Linder_Tech_Fuel_Injector_info.pdf

[brian617]

I think I have a BBNT memcal at home. finding it may be a problem though I may have used it in by buddies CJ5 304 TBI conversion. might explain why I had to disable the flag for the knock sensor:mad1:

BHRD is the one I've been looking through, it's on the $OD page.

[1project2many]

I lost track of some of this but the CPI valve does not need to be present. It was a feature on the early engines that allowed a broader power curve. It worked well. My '95 Blazer out-pulled the '96+ models when towing.

When putting high impedance injectors together in batch configuration it is possible to control them with either saturated mode drivers or peak and hold strategy. The equivalent resistance of six CSFI injectors at 13 ohms is 2.1 Ohms. This is close to the same value as (8) 16 Ohm injectors which is traditionally handled with saturated mode drivers. Choosing peak and hold mode works because the driver circuitry will never reach the current threshold to switch to "hold." The driver will stay in "peak" mode while the injector is commanded on and will not overheat. Injectors with resistance of 13 Ohms or higher would be perfect for this application.

[PJG1173]

I lost track of some of this but the CPI valve does not need to be present. It was a feature on the early engines that allowed a broader power curve. It worked well. My '95 Blazer out-pulled the '96+ models when towing.

When putting high impedance injectors together in batch configuration it is possible to control them with either saturated mode drivers or peak and hold strategy. The equivalent resistance of six CSFI injectors at 13 ohms is 2.1 Ohms. This is close to the same value as (8) 16 Ohm injectors which is traditionally handled with saturated mode drivers. Choosing peak and hold mode works because the driver circuitry will never reach the current threshold to switch to "hold." The driver will stay in "peak" mode while the injector is commanded on and will not overheat. Injectors with resistance of 13 Ohms or higher would be perfect for this application.

the intake should be here Monday at the earliest so I can measure the resistance to see what they are at. I have found conflicting info on the injectors included with this intake.

[PJG1173]

So the question remains batch fire 2 banks of 3 or fire all 6 at once like a CPI. I am leaning towards the CPI strategy, but have been unable to determine if just changing the bit in the bin to pfi/cpi will give me the correct 3 injector firings per crank revolution required. I have yet to find anything that says this strategy needs a physical mod/jumper on the memcal.

So I guess my real question is what are the pro's and con's to each?

[Fast355]

I lost track of some of this but the CPI valve does not need to be present. It was a feature on the early engines that allowed a broader power curve. It worked well. My '95 Blazer out-pulled the '96+ models when towing.

When putting high impedance injectors together in batch configuration it is possible to control them with either saturated mode drivers or peak and hold strategy. The equivalent resistance of six CSFI injectors at 13 ohms is 2.1 Ohms. This is close to the same value as (8) 16 Ohm injectors which is traditionally handled with saturated mode drivers. Choosing peak and hold mode works because the driver circuitry will never reach the current threshold to switch to "hold." The driver will stay in "peak" mode while the injector is commanded on and will not overheat. Injectors with resistance of 13 Ohms or higher would be perfect for this application.

Yea the older 92-95 CPI engines really do perform better than the 96+ vortecs. The cam is similar in specs to what came in a F/Y car LT1 and they have that much more open intake with the tuning valve. Combined with the factory high stall converter and 3.73s the little S10 Blazer I have worked on with the motor had a nice power curve from off-idle through redline. I kinda wish GM had made a V8 version of that intake with the hotter cam and offered it on the L31 trucks. If you scale the 3/4 350 up the 200 HP/260 TQ becomes ~265 HP and ~345 TQ and a table top flat power curve compared to what the L31 was.

[dave w]

The pro to CPI is it will be almost factory, which is a good plan. The con I see to using 6 saturated injectors instead of one peak-n-hold injector is possibly needing a resistor box. On a stock or nearly stock engine, the resistor box will not effect injector response time that would effect performance. There might be a need to tweak the "injector" bias or offset voltages, possibly a con? It might be a good plan to bench test the injectors with the resistor box, and verify the "electronics" with an oscilloscope. Maybe compare the "electronics" of a factory OBD1 V6 PFI system that used either 1227730 or 1227727 to compare injector response times. Measuring the "electronics" would be a good plan.:thumbsup:

dave w



Peak and Hold:

Peak/hold injectors are low impedence, usually in the 1-4 ohm range. When the ecu calls for fuel to be injected, it sends out voltage via the wire clips until a certain current level is reached (the peak part) (varies by injector size, company). For the duration of 1 pulse width, that current is slightly reduced and held (the hold part).

Advantages of this design:

minimizes the injectors "on" time, resulting in faster response

Disadvantages of this design:

increases coil heat, which can lead to failure over time



Saturated:

Saturated injectors are generally higher impedence than peak and hold, running in about the 10-15 ohms range. Unlike peak/hold, a saturated injector remains "on" for the entire pulse width.

Advantages of this design:

reduces heat

Disadvantages of this design:

slower response time
can't handle large CC or lb/hr styles due to limitations in its speed.

[PJG1173]

The pro to CPI is it will be almost factory, which is a good plan. The con I see to using 6 saturated injectors instead of one peak-n-hold injector is possibly needing a resistor box. On a stock or nearly stock engine, the resistor box will not effect injector response time that would effect performance. There might be a need to tweak the "injector" bias or offset voltages, possibly a con? It might be a good plan to bench test the injectors with the resistor box, and verify the "electronics" with an oscilloscope. Maybe compare the "electronics" of a factory OBD1 V6 PFI system that used either 1227730 or 1227727 to compare injector response times. Measuring the "electronics" would be a good plan.:thumbsup:

dave w



Peak and Hold:

Peak/hold injectors are low impedence, usually in the 1-4 ohm range. When the ecu calls for fuel to be injected, it sends out voltage via the wire clips until a certain current level is reached (the peak part) (varies by injector size, company). For the duration of 1 pulse width, that current is slightly reduced and held (the hold part).

Advantages of this design:

minimizes the injectors "on" time, resulting in faster response

Disadvantages of this design:

increases coil heat, which can lead to failure over time



Saturated:

Saturated injectors are generally higher impedence than peak and hold, running in about the 10-15 ohms range. Unlike peak/hold, a saturated injector remains "on" for the entire pulse width.

Advantages of this design:

reduces heat

Disadvantages of this design:

slower response time
can't handle large CC or lb/hr styles due to limitations in its speed.



If only I had the test equipment to do that

[brian617]

I kinda wish GM had made a V8 version of that intake with the hotter cam and offered it on the L31 trucks.

I wish they had made a small block version of the the Vin "L" L29 intake. That's a sweet intake setup.

[1project2many]

the intake should be here Monday at the earliest so I can measure the resistance to see what they are at. I have found conflicting info on the injectors included with this intake.

A former co-worker ordered one of these marine intakes. We decided he would be better off to use GM injectors. We could measure the resistance but could not find the voltage curves or flow rate. We also decided to forgo the TB. We made an adapter to use an L31 (IIRC) TB. Too bad he never finished the conversion. :(


I wish they had made a small block version of the the Vin "L" L29 intake. That's a sweet intake setup.
Heck, they should have continued it with the 96+ 4.3. The '95 cam with the csfi intake and Vortec heads is a strong performer. The dual runner intake would have really upped the ante.

[PJG1173]

A former co-worker ordered one of these marine intakes. We decided he would be better off to use GM injectors. We could measure the resistance but could not find the voltage curves or flow rate. We also decided to forgo the TB. We made an adapter to use an L31 (IIRC) TB. Too bad he never finished the conversion. :(


Heck, they should have continued it with the 96+ 4.3. The '95 cam with the csfi intake and Vortec heads is a strong performer. The dual runner intake would have really upped the ante.

http://www.pacificp.com/forum/viewtopic.php?t=317&postdays=0&postorder=asc&start=0 shows them as Delphi EV6 24lbs/hr. @ 43.5psi. units with USCAR connectors. hoping to find a part number I can research when it comes in. kind of doing this on a limited budget or I would just upgrade to a 98+ computer and get HPTuners or efilive. I do have a set of stock injectors LS injectors from an 02 Camaro. I also have a L31 and 454 TB if needed but I was going to compare them all to see which would work out the best or be made to work the best. this motor requires 600+ cfm I'm at 630cfm now so I'm looking to stay in that ball park. I have also read that the MAP sensor needs to be changed since it has an integrated IAT. not sure why that would be a problem if you are only wiring the MAP in it.

[PJG1173]

well according to ups.com my new intake is sitting on my front porch... :jfj:

[brian617]

. I have also read that the MAP sensor needs to be changed since it has an integrated IAT.

Does look like an awful big plug on that MAP, that would be an easy fix though.

[Fast355]

http://www.pacificp.com/forum/viewtopic.php?t=317&postdays=0&postorder=asc&start=0 shows them as Delphi EV6 24lbs/hr. @ 43.5psi. units with USCAR connectors. hoping to find a part number I can research when it comes in. kind of doing this on a limited budget or I would just upgrade to a 98+ computer and get HPTuners or efilive. I do have a set of stock injectors LS injectors from an 02 Camaro. I also have a L31 and 454 TB if needed but I was going to compare them all to see which would work out the best or be made to work the best. this motor requires 600+ cfm I'm at 630cfm now so I'm looking to stay in that ball park. I have also read that the MAP sensor needs to be changed since it has an integrated IAT. not sure why that would be a problem if you are only wiring the MAP in it.

I started out with 4.7 injectors in my Marine intake after selling the Marine injectors on Ebay (they bring good money). Then in search of better driveability I moved over to LS1 injectors.

[Fast355]

Does look like an awful big plug on that MAP, that would be an easy fix though.

I am running the marine map on my swap. Its just the normal GM 1-bar map with a MAT sensor. My intake came with a matching pigtail for it. The actual connector pins were the same as my factory L31 harness. No splicing necessary, just unpin and repin.

[PJG1173]

I started out with 4.7 injectors in my Marine intake after selling the Marine injectors on Ebay (they bring good money). Then in search of better driveability I moved over to LS1 injectors.

hmm a way to recoup some to spend on other upgrades. I did notice when looking up the suspected part number they were quite pricey on ebay. I have to txt the guy I got the LS injectors form to see what he originally had them in since his motor wasn't any where near stock.

[PJG1173]

I am running the marine map on my swap. Its just the normal GM 1-bar map with a MAT sensor. My intake came with a matching pigtail for it. The actual connector pins were the same as my factory L31 harness. No splicing necessary, just unpin and repin.

good to know thank you

[PJG1173]

here is the PN for the LS1 injectors I have 12555894 from what I can find on line they are 26.3 # @ 58psi. I'm thinking these may be the ticket

[dave w]

Have you measured the impedance of the 12555894 injectors?:popcorn:

dave w

[PJG1173]

Have you measured the impedance of the 12555894 injectors?:popcorn:

dave w

11.8 +/- .1 which are the same as the marine ones (this differs from what I have read about on the marine injectors). I haven't double checked the part numbers on those yet because they are too hard to read installed. I plan on taking the intake apart this week so I can port match them to the gaskets like the heads are.

[dave w]

With six 11.8 ohm resistors in parallel, that is about 2 ohms. I think that is close enough to work with the '7427 PCM without modification. I don't have experience actually running the setup like your going to do, the math looks close enough. If you want closer to 1.5 ohms, you would need to install a 38 ohm resistor across the two injector terminal of all six injectors and connect the injectors in parallel.

dave w

[PJG1173]

after reading this I think I still will have to do the driver mod.
http://www.dynamicefi.com/InjectorDriving.php

[dave w]

Maybe, maybe not? Typically Dynamic EFI does not list the 16197427 PCM.

I would completely agree with the specifications for the ECM's listed on the Dynamic EFI website.

1227137 '86 Safari, Astro
1226868 '85 MonteCarlo
1227429 '86-'88 S10 2.8l
1227746 Truck
1227747 Many Trucks & Vans
1228062 Blazer
1228063 '88 Camaro, Firebird
1228746 '89-'92 Camaro, Firebird, Caprice
1228747 Truck
1228838 '90 Lumina, 3.1l
16136965 '91-'94 Caprice, Roadmaster wagon
16144288 Blazer
16146299 Truck
16149405 '93 Trans Sport, Silhouette, Lumina: APV, 3.1l
16171199 '94-'95 trucks, MT
16196391 '95-'95 Lumina, Trans Sport, 3.1l
16196396 '94-'95 trucks, MT



dave w

[PJG1173]

will it hurt to put a jumper across the drivers?

[dave w]

will it hurt to put a jumper across the drivers?

I don't have experience with doing the 6 cylinder port injector modification, so I can't answer if the jumper is needed or not. I'm thinking no jumper.

I have experience with is electronics ... with the injectors configured with the correct impedance the injector driver will be happy.:thumbsup: I found 33 ohm 50 Watt resistors at Newark http://www.newark.com/te-connectivity-cgs/ths5033rj/wirewound-resistor-33-ohm-50w/dp/18R0442 ($2.39 each). I would use the 33 ohm resistors across each 11.8 ohm injector, then wire the injectors in parallel to equal 1.45 ohms impedance on the injector driver. In a perfect world 38 ohm 50 watt resistors would be available, I could not find them with Google. Using an unmodified computer / unmodified memcal means having all six injectors fire at once, which works good. Electronically, I think this is a good plan.

dave w

[PJG1173]

55 watt that thing looks bigger than the injectors. defiantly going to have to make a resistor box, I probably could use a handy box with a project board. I also have an additional computer I can mess with so it can be tested both ways.

[dave w]

Maybe you would like me to post a wiring schematic of the resistor box, or maybe build you a resistor box?

dave w

[PJG1173]

Yes a schematic would be nice. I was going to post up some scetches later tonight for you to look at. Thanks for the offer to make one, but I shoulg be able to come up with something. I need to make it water resistant, vibration proof, and mountable.

[dave w]

Yes a schematic would be nice.

See Pic. Any questions?

dave w

[1project2many]

Ok learning time for me.

Adding parallel resistance as above would cause the Peak and Hold injector driver circuitry to operate in both peak and hold modes, delivering about 4 Amps to the injectors initially then decreasing current to 1A after it believes the injectors are open. I know this circuit is an atypical solution. Resistor boxes are typically installed to allow low impedance peak and hold injectors to be used with a saturated driver, preventing the driver from overheating due to excessive current flow through the low impedance coils of the peak and hold injector. IIRC placing a resistor in parallel with an inductor results in changing current flow through the inductor lagging behind current through the resistor. As you have approximately 5 1/2 Ohms in parallel resistance, wouldn't triggering the injectors cause the injector driver to change very quickly from "peak" mode to "hold" mode, possibly preventing the injectors from reaching saturation within required time?

Thanks...

[PJG1173]

Ok learning time for me.

Adding parallel resistance as above would cause the Peak and Hold injector driver circuitry to operate in both peak and hold modes, delivering about 4 Amps to the injectors initially then decreasing current to 1A after it believes the injectors are open. I know this circuit is an atypical solution. Resistor boxes are typically installed to allow low impedance peak and hold injectors to be used with a saturated driver, preventing the driver from overheating due to excessive current flow through the low impedance coils of the peak and hold injector. IIRC placing a resistor in parallel with an inductor results in changing current flow through the inductor lagging behind current through the resistor. As you have approximately 5 1/2 Ohms in parallel resistance, wouldn't triggering the injectors cause the injector driver to change very quickly from "peak" mode to "hold" mode, possibly preventing the injectors from reaching saturation within required time?

Thanks...

Yep right over my head?

[PJG1173]

See Pic. Any questions?

dave w

That is what i had imagined it was going to look like very simple circuit. I need to find some weatherpack connectors at the JY and order the resistors.

[dave w]

Ok learning time for me.

Adding parallel resistance as above would cause the Peak and Hold injector driver circuitry to operate in both peak and hold modes, delivering about 4 Amps to the injectors initially then decreasing current to 1A after it believes the injectors are open. I know this circuit is an atypical solution. Resistor boxes are typically installed to allow low impedance peak and hold injectors to be used with a saturated driver, preventing the driver from overheating due to excessive current flow through the low impedance coils of the peak and hold injector. IIRC placing a resistor in parallel with an inductor results in changing current flow through the inductor lagging behind current through the resistor. As you have approximately 5 1/2 Ohms in parallel resistance, wouldn't triggering the injectors cause the injector driver to change very quickly from "peak" mode to "hold" mode, possibly preventing the injectors from reaching saturation within required time?

Thanks...

The approximate parallel resistance of the 11.8 injector with the 33 ohm resistor is 8.7 ohms. The approximate parallel resistance of 6 individual 8.7 ohm resistors in parallel is about 1.45 ohms. This is very close to the resistance of the single CPI injector.

When the injector driver turns ON the resistor box, the injectors will immediately fire. When the injector driver turns OFF the resistor box, there will be a very slight amount of lag time before the injector fully turns off. The lag time is because the 33 ohm resistor will very briefly hold some current in the injector.

It's not a perfect solution. I'm thinking it's an acceptable solution. We will need an oscilloscope to measure the lag time.

dave w

[brian617]

I need to make it water resistant, vibration proof, and mountable.

The way I had imagined it was to use the resistor across the terminals at the injector plug itself much like an AC diode on the mide 90's GMs.

http://t1.gstatic.com/images?q=tbn:ANd9GcQRihRGuNW2eIWh-kXktUl8w4EBTMAVpuXLVWnFLuCVEiqDqrIB

[dave w]

The way I had imagined it was to use the resistor across the terminals at the injector plug itself much like an AC diode on the mide 90's GMs.

http://t1.gstatic.com/images?q=tbn:ANd9GcQRihRGuNW2eIWh-kXktUl8w4EBTMAVpuXLVWnFLuCVEiqDqrIB

I considered the same concept using a 5 watt wire wound resistor. It appears most resistor boxes use the 50 watt resistors, I followed the trend.

dave w

[brian617]

I considered the same concept using a 5 watt wire wound resistor. It appears most resistor boxes use the 50 watt resistors, I followed the trend.

dave w

Is this what you had in mind?

http://i133.photobucket.com/albums/q71/GhostAccord/Odds-n-sodds/ResistorBoxWiring2.jpg

[dave w]

Is this what you had in mind?

http://i133.photobucket.com/albums/q71/GhostAccord/Odds-n-sodds/ResistorBoxWiring2.jpg

No, not really. The picture posted above is the typical application of a resistor box.

The resistor box I've proposed, is not the typical resistor box. It's somewhat the electronic opposite of the resistor box posted above.

I am going to use the LCR meter at work to determine the actual inductance of the injector, then crunch some math to see what the RPM limit of the "Impedance Matched" resistor box might provide. Having a slight lag with "Injector Off" could limit the RPM range of the injector driver, or "Saturate" the injector driver (not a good thing to have happen). As long as the injector is completely "Off", before the next injector "On" is triggered by the injector driver the impedance match resistor box will work. The higher the engine RPM is, the less time there is between injector "On" and injector "Off".

dave w

[brian617]

After a little digging I noticed the early Hondas and Toyotas use a resistor box. Went out in the yard and scrounged up a resistor box off a 95 4 cly Accord and got 6 ohms between 12v input and one of the 4 B+ out to injectors.

[PJG1173]

the first diagram puts the resistors in series. this is what I was thinking physically where I could mount it on the intake behind the TB or something.8799

[PJG1173]

This is why I need water and shock resistant. Hopefully a resistor box won't generate too much heat.

[dave w]

the first diagram puts the resistors in series. this is what I was thinking physically where I could mount it on the intake behind the TB or something.8799

Electrically, it look like the posted schematic is equivalent to the circuit I posted.

Impedance matching (resistor box) might not be everything that is needed. I'm doing more homework on the injector driver, http://automotivetestsolutions.com/understanding-fuel-injector-waveforms.html

dave w

[PJG1173]

Electrically, it look like the posted schematic is equivalent to the circuit I posted.

Impedance matching (resistor box) might not be everything that is needed. I'm doing more homework on the injector driver, http://automotivetestsolutions.com/understanding-fuel-injector-waveforms.html

dave w

wow, lots of info on that page. may have to look at that tonight before I go to bed. also trying to track down an OScope and an operator for said scope. One of my friends says he has one of these but he's not sure how to use it as a scope, and its been 25 years since I touched one and it sure wasn't that small.

[dave w]

My O'scope is old ... see close up of an injector (inductor) discharging after injector turning off. Adding a resistor will effect how an injector discharges after the injector is turned off.

As a thought, this kind of "Homework" verges on "Product Development".

I recently received an order for several custom wire harnesses ... I'll be extremely busy the remainder of April. I'm going to have table any further "Homework" on this project until the harnesses ship, due date 30 April.

dave w

[brian617]

Dave, not being an electrical engineer help me understand the difference between your diagram and the one I posted assuming all the control side wires were connected to a single injector driver, rather than the four separate in the picture. I see your method puts the resistor between the control and the B+ and mine shows the resistors inline with the B+.

[dave w]

I see your method puts the resistor between the control and the B+ and mine shows the resistors inline with the B+. That is correct. With resistors inline (series) the resistance of the resistors will add. With the resistor between the control and the B+ (parallel) the resistance is reduced. There are algebraic equations that determine how much the resistance is reduced in parallel.

Normally resistor boxes are used to increase the resistance to an injector. (resistors in series)

I'm thinking just the opposite, use a resistor box to decrease resistance to an injector. (resistors in parallel)

dave w

[PJG1173]

My O'scope is old ... see close up of an injector (inductor) discharging after injector turning off. Adding a resistor will effect how an injector discharges after the injector is turned off.

As a thought, this kind of "Homework" verges on "Product Development".

I recently received an order for several custom wire harnesses ... I'll be extremely busy the remainder of April. I'm going to have table any further "Homework" on this project until the harnesses ship, due date 30 April.

dave w

I see this is a little more in depth and complex than I thought it was originally going to be. since we are in race season there is no window for me to get this in until June. I started this thread for information gathering and decision making. after many hours of searching I have yet to dig up any threads of people going from TBI to CPI with out using the factory CPI unit, nor can I find where any one has done a marine intake conversion on a v6 using an odb1 computer. I would love to make the jump to odb2 and make this a lot easier but funds dictate I work with what I have. on another note I found my CPI MEMCAL BSWW which looks like it was superseded by BSWX only difference is idle speed. I believe its out of an Astro van so if there is any CPI specific to the MEMCAL I am covered there.

[whatif3387]

I've only read through part of this thread i'm not sure if this has been mentioned or not but I'm pretty sure an EBL from dynamicefi will do what your trying to do for rather cheap. Not as cheap as burning chips but for what you can do with the EBL I think it's definitely worth what it cost.

[PJG1173]

The EBL won't support my 4l60E, at least last I checked. If I swap out computers I will step up to ODB2 and go sequential PFI. the issue here is that I am looking to make the 8625/7427 fire 6 injectors like the old v6 central port injected (CPI) did with the same computer.

[1project2many]

the issue here is that I am looking to make the 8625/7427 fire 6 injectors like the old v6 central port injected (CPI) did with the same computer.

I realize this is probably obvious but electrically speaking the 8625/7427 never fired six central port injectors. The 8625/7427 triggered one injector which delivered fuel to six poppet nozzles simultaneously. The CPI injector was treated like a single TBI injector and was driven in peak and hold mode. Trying to operate six PFI injectors is somewhat different.

[dave w]

The EBL won't support my 4l60E, at least last I checked. If I swap out computers I will step up to ODB2 and go sequential PFI. the issue here is that I am looking to make the 8625/7427 fire 6 injectors like the old v6 central port injected (CPI) did with the same computer.

Use two computers, EBL for injection / '7427 for 4L60E. The '7427 will need power, ground, TPS, VSS, and DRP's to operate a 4L60E. Check with EBL, I'm sure they have a solution, maybe in your budget?

dave w

[whatif3387]

Use two computers, EBL for injection / '7427 for 4L60E. The '7427 will need power, ground, TPS, VSS, and DRP's to operate a 4L60E. Check with EBL, I'm sure they have a solution, maybe in your budget?

dave w

This is exactly what I'm running except with TBI. I'm running the EBL piggy backed with my original 7427 to control my 4l60e and it works great. Bob from dynamicefi was able to provide me with a very straight forward and easy to follow wiring guide for wiring up this setup. To wire both of them together took me about 30 mins to an hour it was alot easier then I thought and prior to this had zero experience with ecu wiring and tuning in general.

[PJG1173]

Use two computers, EBL for injection / '7427 for 4L60E. The '7427 will need power, ground, TPS, VSS, and DRP's to operate a 4L60E. Check with EBL, I'm sure they have a solution, maybe in your budget?

dave w

I have read about this before but, I prefer not to go that route. the 7427 can be made to run PFI on a V8 so there should be no reason it won't work on a v6 maybe not in the way I first envisioned.

[dave w]

I have read about this before but, I prefer not to go that route. the 7427 can be made to run PFI on a V8 so there should be no reason it won't work on a v6 maybe not in the way I first envisioned.

Maybe so? I should try an experiment using a MPFI V8 setup with 6 injectors when I setup the O'Scope.

There is the option of using a 1227730 (low cost ECM option that the factory used in many FWD V6 MPFI vehicles from 1989 ~ 1992) to operate the 6 injectors and have the '7427 operate the 4L60E. This might be the best option for time and money? Using the 1227730 eliminates the need for the EBL system. The 1227730 would work with a V6 distributor, instead of a coil pack typically seen with the FWD V6.

dave w

[brian617]

If you can make a V8 TBI .bin into a batch fire PFI .bin by doing the hard ware and software changes, stands to reason that you could do the same for a V6 TBI .bin right?

[PJG1173]

looking at the wire diagram for the 1227730 it looks like it is batch firing 2 sets of 3 injectors in parallel, so it shouldn't be any different with the 7427 should it?
http://www.gearhead-efi.com/Fuel-Injection/attachment.php?attachmentid=1915&d=1331409468

[dave w]

There are different injector firing patterns for batch fire. I'm thinking once every 4th DRP for V8. I don't know if the V6 will work correctly if its injectors are fired once every 4th DRP. I'm thinking the V6 batch fire is once every 3rd DRP?

dave w

[brian617]

This page shows 6 PFI every 3rd DRP and the proper voltage across the memcal mode selection. However it lists the ECM as a 16174470.

https://web.archive.org/web/20030216033345/http://www.fortunecity.com/rivendell/oddworld/24/ECM/inj_op.htm#close

[1project2many]

The CPI memcal is configured the same as a "Six Cylinder PFI" memcal.

[brian617]

So what what does this mean for fueling requirements if the CPI injector fired all six injectors every third DRP, compared to a PFI modded TBI .bin alternating bank firing every third DRP?

[PJG1173]

So what what does this mean for fueling requirements if the CPI injector fired all six injectors every third DRP, compared to a PFI modded TBI .bin alternating bank firing every third DRP?

good question

[PJG1173]

This page shows 6 PFI every 3rd DRP and the proper voltage across the memcal mode selection. However it lists the ECM as a 16174470.

https://web.archive.org/web/20030216033345/http://www.fortunecity.com/rivendell/oddworld/24/ECM/inj_op.htm#close

very informative mostly Greek to me

[1project2many]

So what what does this mean for fueling requirements if the CPI injector fired all six injectors every third DRP, compared to a PFI modded TBI .bin alternating bank firing every third DRP?

Total fuel delivered needs to be correct. If injectors are triggered more often then maximum on time for each event must be smaller. It could be possible to run into situation where injector commanded on time is below minimum threshold to deliver correct fuel, but it's not likely with properly sized injectors.


very informative mostly Geek to me

Fixed it for ya. ;)

[brian617]

very informative mostly Greek to me

Hurts my brain too lol.

[PJG1173]

Total fuel delivered needs to be correct. If injectors are triggered more often then maximum on time for each event must be smaller. It could be possible to run into situation where injector commanded on time is below minimum threshold to deliver correct fuel, but it's not likely with properly sized injectors.

this is the issue I am running into with the TBI. I am running 65# cop car injectors at 21 psi in order to keep my afr and DC within acceptable limits at WOT. I had to cut my minimum pulse width setting in half to keep it from overloading at idle. low throttle driving is poor to say the least.



Fixed it for ya. ;)

I can speak geek just not that much at one time.

[1project2many]

Some of the TBI code, at least $58, is able to deliver fuel in semi-synchronous mode. The injectors are pulsed 1/2 as many times for 2x as long. Maybe this is possible in the code you're using? It took some time to get the transitions smoothed out when I used it in the Cavalier but ultimately it worked well.

[dave w]

Here is what I'm thinking ... Maybe I should use the O'Scope Memcal BHRJ (hopefully BHRJ is a 4.3 CPI Memcal?) with the sense resistors shorted (same modification as the V8 MPFI), using 2 banks (3 injectors each bank)? I'll have the test harness finished this weekend. I hope to test both V8 and V6 configurations. I'm hoping the cylinder select voltage is correct with the BHRJ Memcal for firing the injectors every 3rd DRP?

dave w

[PJG1173]

I was thinking along the same lines. I was trying to see if I could hook up some noid lights to my injector wires and put that the BSWW memcal I have in and see what it did while cranking. I have read the chip and it is defiantly a CPI/4l60e. I wish I had a test bench but I don't do enough of this stuff to warrant getting the stuff to do it. I downloaded the $OD hack and tried to read through it. I need to brush up on my Greek/Geek. I do believe I saw a reference to every 3rd DRP, but could not understand heads or tails of what it meant.

[PJG1173]

I finally got time to start working on this again. I was real busy at work doing a couple of major projects. I managed to get the intake installed on the motor. there was a couple of clearance problems with the accessory brackets but nothing a little trimming couldn't fix. I ended up having to use the "O" rings off the marine injectors on the LS injectors to make them fit tighter to the intake. I am getting ready to start extending the wires so they reach the TB and switch out the connector for the IAC. Since the vortec IAC looks the same as the one on the TBI 454 do I need to transpose the two wires like if I was switching to the 454 TBI?

[PJG1173]

Looking at the wiring diagrams for a 97 vortec truck it appears the colors match and no need to cross the wires. The IAC is also a different P/N than the 454 TBI. now I have to get a new fuel pump as the one I have is stalling at 45 psi which is about 13 psi below what the regulator is.:mad1:

[PJG1173]

OK so I got everything buttoned up tonight and tried to start it. the first thing it did was kick back on the starter and ripped it right off the block... after cleaning out the threads on the block and putting studs in the block I put it back to TDC on the compression stroke and checked the distributor and it was right on the leading edge of the #1 terminal. disconnected the esc wire and tried to start again it kicked a little so I retarded the distributor so it wouldn't kick back. I was able to start it but my timing light was showing that it was running a steady 10* retarded and running very lean. my tuner pro dash was showing the timing jumping all over the place. as soon as I tried to rotate the distributor back to 0* it cut off. I backed the distributor off and started it again and captured a log. bad.xdl was taken with the computer I did the injector driver mod on and bad2.xdl was taken with the original computer that I have been running in this truck since I had it. I since I hadn't removed the prom from the memcal I took it off the g1 adapter and plugged it in the computer there was no change with either way I tried. I am running a CPI memcal so I assume it doesn't need to be modified for mpfi. I used a 94 s10 cpi bin and copied my spark and ve tables into it with the efan code. while it was running I could feel all 6 injectors firing. looking at the log file I am getting erratic DRP's. I am leaning towards the distributor being bad, but I am having a hard time believing its bad since it was running fine before I pulled the intake. can someone please take a look at my log files and see if there is something I'm missing?

[PJG1173]

ugh the balancer was 90* off. :mad1: guess I need a new one of those now too. I'll add that to the list of things to do along with put helicoils in the block for the starter bolts. but hey it runs :rockon: had to increase my idle VE to get it to idle. once I get it so where the starter don't sound like its going to fly off when I crank it I can start tuning!

[ony]

have you got one of them timming gears that has 3 woulddrift key holes on the timming gear that goes on the crankshaft?

[PJG1173]

No, not many timing chain options for a balance shaft motor. I think the problem is that is a 93 crank with a 01 balancer and cover. It is exactly 90* off. I need to talk to the machinest that assembled it. The machine shop dropped the distributor in and marked it when they built it. The timing tape has long since come off

[brian617]

Glad to hear it runs! Need pictures.

[PJG1173]

not much to look at. Just finished up the CAI the other night
http://i1129.photobucket.com/albums/m515/pjg1173/20150707_2156091_zpsfeks0uw8.jpg (http://s1129.photobucket.com/user/pjg1173/media/20150707_2156091_zpsfeks0uw8.jpg.html)

I need to find some sort of insulation tape to help keep heat from transferring to the metal.
http://i1129.photobucket.com/albums/m515/pjg1173/20150707_2155081_zpsmsz4n8op.jpg (http://s1129.photobucket.com/user/pjg1173/media/20150707_2155081_zpsmsz4n8op.jpg.html)
I also need to wire in the IAT sensor. I have only got a couple 20 min tuning sessions with it this week and wow what a difference. even sounds different. I have found that for some reason it needs ALOT more AE than what the stock CPI tune has.

[brian617]

Did you have to file the holes in the bracket to fit that alternator? Wanted to use that style alt, but not much meat on those style brackets.

[PJG1173]

To be honest its been so long since I put that on I cant remember. I think I used smaller diameter bolts with a little filing. Its been on there at least 3 years. 145 amp from a 05 chevy 2500 duramax. I have it hooked to a 120 amp battery isolator running to two 900 CCA batteries.