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Thread: 383 tuning help

  1. #16
    Fuel Injected! dktool's Avatar
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    Quote Originally Posted by myburb View Post
    The prongs on the chips are very thin and I tended to get one bent trying to put it in. The zif allowes you to just drop the chip in and flip the lever and you are done. If you want to get the tune really good you will tweak and data log a LOTA LOTA times. The only problem with the zif is it makes the chip sit up higher. Moates does have a low profile zif. What some do is use the zif while you are tuning and when you get the tune done then you can carefully insert the chip without the zif and then the cover on the case will fit ok. That adapter you have looks like it does a similar job to the g1. With the g1 you retain your limp. Not sure if yours does.
    This ^^^

    I originally started with the low profile zif for the sake of the low profile and cover clearance, what I found was that I was R&R'ing the chip so much that the lesser quality and more difficult lever operation was causing some grief so I went with the higher profile / quality zif with the metal lever, sooooooo much better !
    With the taller zif the chip guides into place very easy and the large lever is easy to lock even with my gigantic fingers.
    I can reach down and remove the chip without leaving the captain's chair.

    I will someday put the low profile one back in and the cover on but I still find I like the ease of pulling / installing the chip and still play with the tune even after getting it REALLY good. (I never leave thing's "well enough", got to have tinker-time)

    1 year ago I didn't even know this tuning was possible, now I am comfortable with what I do. I will say that based on the steep learning curve I am glad I went simple and didn't go the APU1 route. For me, stopping and pulling the chip and re-burning a change is close enough to "on the fly real time tuning".
    Last edited by dktool; 2 Weeks Ago at 12:09 PM.
    Dean

  2. #17
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    Thanks for that experience with the zif guys. Dktool so what did you use for doing the re-burning?? I was going with APU1 cause it looks like its all there to do what I need to..
    I’m still trying to figure out turner pro..I don’t have it yet but doing a lot of reading and don’t understand all the symbols are with the $B or whatever $ that is....Thanks
    Last edited by C2500; 2 Weeks Ago at 12:26 PM.

  3. #18
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    The apu doesn't have to be used emulating. I just data log with mine, decide what I need to change and burn a chip with the apu.
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

  4. #19
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    In ref to tuner pro and the process, it is a litte steep on the learning curve at first. Then it is kind of "bingo" and it all starts to fall in place. With the $, they are the mask which is relevant to your vehicle. In your case it will be $OE or $OD depending on what transmission you have.
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

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  6. #21
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    while we are passing info to get you going, here is a pigtail extension I made so I could mount the pcm under the front seat but leaving the truck wiring intact.
    Attached Images Attached Images
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

  7. #22
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    Looks like a good idea thanks!!

  8. #23
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    C2500
    The computer tuner guys I think will have you covered.
    However lets look at the basics first.

    You are not getting what you expected to.
    First lets check the timing
    Are you running pump gas or REC90 race gas
    On modern pump gas up to 10% ethanol you can set your total advance to 38 manually by bringing the motor up to 3000 rpm for 30 seconds and then set timing to 38 degrees. Then disconnect the timing bypass under the dash and check timing at idle should be about 10-16 degrees. On race gas the same, on REC90 set it down to 35 and 10.
    Then check your vacuum on a 383 even with a medium cam the vacuum should be greater than 26 inch HG.
    If lower increase fuel pressure bit and check again you want to get the highest vacuum you can obtain at idle.
    Now if you put a vacuum pump on the EGR valve and pump it up the idle should get funky and vacuum go down release the vacuum pump and it should recover.
    If not then yank the EGR and replace, on the 2500 you need the EGR to protect your top ring lands.

    If the old motor was puking oil your cat and even the resonator can be clogged if the same pull the O2 sensor and put a adapter in with a 0-10psi gauge with a long hose take the truck out run it normal and look at the pressure gauge it should not exceed 2 psi if so replace exhaust before you ruin your new motor.

    Another issue that a lot of truck owners have is the lame fuel pump on the trucks since the stick motors were only 200 HP the bean counters put the cheap fuel pump in 36 dollars at GM dealers.
    I changed mine out to an AC Delco EP376 and set the fuel pressure at 18PSI.
    Now the truck is crisp and pulls all of its 200 HP working ;-)
    Before complete failure mine had no symptoms and the previous owner did not notice.
    When I changed mine the fuel pressure was below 1 psi I measured on a digital gauge so swap out the pump.

    Once all good then look into the tune.

    I have played with the 7.4L 2inch TBI unit no good for less than 400 CI it tends to dribble instead of squirt at idle and low rpm and you get a bad BOG even if you raise the enrich table all the way. The bigger TBI was designed for the BBC not the SBC and kind of sucks on a small block.
    The stock TBI unit with all of the Mods is good for 670CFM the 383 naturally aspirated is good for 450HP under 6000rpm.
    With 6lbs of boost easy 600hp.

    To get the 450HP hour available the intake and fuel system has to support 9.16Gallons of Gasohol per hour at 14.2:1 and 130 gallons of air per hour In and out.
    Full rich 110 Gallons per hour full lean 156.6 Gallons per hour.
    You need 55.62 PPH of gasohol to make 450HP.
    The stock injectors new flow 55PPH.
    Lots of guys are putting the 7.4L injectors (92PPH) in and trying to get an acceptable idle they dribble at low pulse width and actually are limited to about 5300 RPM until full open.
    They are quite a bit slower reacting and the minimum injector off time is relatively longer so poor economy slower throttle response.

    It reminds me of when the dominator carbs came out and a bunch of guys upgraded their 650 double pumpers on stock SBC to 1000 cfm Dominators because more was better. I actually got a couple of those pink slip titles back in the day.

    Remember Nascar makes 900 to 1100 HP on 104 octane pump gasoline from a mandated 348 cubic inches through a 13/16 throttle restrictor plate.
    Avatar is my motor 800 RPM 184ft Lbs Torque 18 inches x 18 inches x 9 inches thick external combustion engine.

    98 WS-6 full tube chassis rally car Aluminum Block LS2 (soon to be LSX 376)(in Storage)
    95 Suburban 6 inch drop, Zoomies, Tri-Y Headers, Pioneer DVD in Dash (Soon to Be LT-4).
    95 Caprice 9C1 Fleetwood Brougham Interior, LT-4 (retired)(Engine Donor for new truck)
    2002 Seville STS

  9. #24
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    Looks like I have some work to do..
    Old motor was good no oil issues it was just tired exhaust and converter are good as I had the Y pipe off and converter is clean..
    My Timing is set at 0* at idle with plug unplugged..
    It’s got the stock deco pump in it but it was replaced a year ago but I do have a New EP241 Delco pump. What’s the difference between that pump compared to the EP376 Pump?
    Other members said that the injectors are to small..
    So what should I change the stock 61PPH injectors to ?
    Last edited by C2500; 1 Week Ago at 06:09 AM.

  10. #25
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    First the base timing is way to low that will make exhaust manifolds glow.
    The manual says 0 and it will run like crap like I said set your timing at 3000 to 38 degrees the base timing will fall in about 10-16.
    With timing bypass connected.
    This is a big difference in power.


    If your single injectors are 61PPH thats well over the required 90 Gallons per hour to make 450hp.
    If thats the combined even its enough.
    I think you need a better fuel pump

    On PFI many guys fall into the bigger is better when often its just the access pump curve rather than the injector providing the gain.
    On the TBI it is much more like a carb
    Cold enrichment should be 10-20% higher than stock
    Accel should be 50-100% higher
    Avatar is my motor 800 RPM 184ft Lbs Torque 18 inches x 18 inches x 9 inches thick external combustion engine.

    98 WS-6 full tube chassis rally car Aluminum Block LS2 (soon to be LSX 376)(in Storage)
    95 Suburban 6 inch drop, Zoomies, Tri-Y Headers, Pioneer DVD in Dash (Soon to Be LT-4).
    95 Caprice 9C1 Fleetwood Brougham Interior, LT-4 (retired)(Engine Donor for new truck)
    2002 Seville STS

  11. #26
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    On the Timing when it’s running idling with spout connected with timing set on zero disconnected it’s running about 20 advanced at idle

  12. #27
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    A pair of 61 lb/hr TBI injectors are good for 205-210 hp @ 85% duty cycle at the stock 13 psi and if they were static, meaning on all the time, good for about 250 hp at most. Most engines run around 1/2 lb/per hr/per hp. 61 lb/hr x 2 injectors /.5 bsfc = 244 hp. Even if you were running a Vortec head and had a very good BSFC around .45 that is still only fuel for 270 hp.

    Simply advancing the base timing will also not work very well. The TPI heads you are running like about 34* of timing at WOT not the 38* mentioned above. 38* is for the older slow burning smog heads. With 20* of idle timing when you advance the timing to 12-16 as mentioned above you end up with 32-36* of idle timing which is too much for the mild cam you have. The advance curve is also slower in the ECM than what the TPI heads need. The TPI heads like about 16-20* of timing from 1,000 rpm through about 2,400, then up to about 30* from 3,000-4,600 and finally on to 34* above 4,600. The TBI heads have a substantially different timing advance requirement.

    I have been through converting a 305 HO with 14022601 heads to TBI and had to make massive changes to the chip in both timing advance and fueling to make it run correctly. To give the little 305 with the mild 204/214 @ .050 cam and headers enough to drink I had to run 350 injectors at 14 psi.

    Finally....I am not even going to get started on why someone would pull the 191/193/810 swirl port heads off and put even worse TPI heads on.
    Last edited by Fast355; 1 Week Ago at 12:04 PM.

  13. #28
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    Quote Originally Posted by Fast355 View Post
    A pair of 61 lb/hr TBI injectors are good for 205-210 hp @ 85% duty cycle at the stock 13 psi and if they were static, meaning on all the time, good for about 250 hp at most. Most engines run around 1/2 lb/per hr/per hp. 61 lb/hr x 2 injectors /.5 bsfc = 244 hp. Even if you were running a Vortec head and had a very good BSFC around .45 that is still only fuel for 270 hp.
    450 HP Hour requires 9.16 Gallons per hour of Gasohol.
    Mechanical efficiency of stock motor is 49% with new pistons rings increased compression and roller cam 76-80%

    At 6lbs per gallon thats 54.96 PPH

    The injectors will provide at stock fuel pressure 336HP no problem.
    At 18psi like I recommend they will flow reliably at 74-75PPH


    Quote Originally Posted by Fast355 View Post
    Simply advancing the base timing will also not work very well.
    I agree base timing is really not that important but the 0degrees as stated would cause the exhaust vales and pipes to over heat at idle.
    At 3000 RPM GM HEI will reach no knock retard maximum advance after 30 seconds.
    That has been the normal for all SBC since the beginning.
    Setting the timing to 38 degrees at this point sets the distributor phasing and the maximum no knock advance possible.
    At 4200 and up knock will retard the timing 4-5 degrees no problem.

    At 4200 shift point the roller rockers will make noise this is not knock but will retard the timing an additional 2-3 degrees.

    Quote Originally Posted by Fast355 View Post
    The TPI heads you are running like about 34* of timing at WOT not the 38* mentioned above. 38* is for the older slow burning smog heads. With 20* of idle timing when you advance the timing to 12-16 as mentioned above you end up with 32-36* of idle timing which is too much for the mild cam you have. The advance curve is also slower in the ECM than what the TPI heads need. The TPI heads like about 16-20* of timing from 1,000 rpm through about 2,400, then up to about 30* from 3,000-4,600 and finally on to 34* above 4,600. The TBI heads have a substantially different timing advance requirement.
    On this one I can authoritatively say that since I wrote the GM service bulletins on Corvette and Camero TPI ignition timing with aluminum heads.
    That the timing retard for these heads was solved in 1991 with the new knock sensors and EST modules.
    Yes there is a different module for the corvette and the sensors are different.
    This was not for the cast iron vortex heads only the aluminum.
    Same device was mirrored in 1996 with the different EST and Knock sensors on the LT-4 engines because of the roller rockers.

    As for the power available and RPM capabilities of the GEN1 and GEN1.5 TBI engines with stock injectors and HEI
    Here is a snap shot of a 1984 Corvette I am tuning tuning at @7400 RPM with no Knock and only a 4ms Pulse width on the Crossfire TBI injectors.
    There is no load attached to the motor so no HP rating.
    IMG_1401.JPG
    Avatar is my motor 800 RPM 184ft Lbs Torque 18 inches x 18 inches x 9 inches thick external combustion engine.

    98 WS-6 full tube chassis rally car Aluminum Block LS2 (soon to be LSX 376)(in Storage)
    95 Suburban 6 inch drop, Zoomies, Tri-Y Headers, Pioneer DVD in Dash (Soon to Be LT-4).
    95 Caprice 9C1 Fleetwood Brougham Interior, LT-4 (retired)(Engine Donor for new truck)
    2002 Seville STS

  14. #29
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    Quote Originally Posted by C2500 View Post
    On the Timing when it’s running idling with spout connected with timing set on zero disconnected it’s running about 20 advanced at idle

    Ok so with the timing bypass connector connected it is reading 0 degrees
    And with the connector disconnected it is reading 20 degrees
    If so than you have the timing set 20 Degrees AFTER TDC instead of before.

    To check disconnect the bypass connector under the dash.
    Start and idle the engine
    Check the timing with a dial light set on 0 the mark should be at the largest notch for 0 degrees and towards the water pump edge of the timing tab for 14-16 degrees.
    If it is at Zero or towards the water pump
    Shut off the engine and reconnect the timing bypass connector.
    Restart the engine
    Have a friend slowly raise RPM to 3000 RPM
    After 30 seconds have passed use the dial on the back of the timing light to align the timing mark to the largest notch.
    Read the dial indicator on the back of the timing light.
    Turn the distributor slowly checking again after each move.
    When complete the reading should be 38 degrees.

    Harbor freight has a dial timing light for 29USD that will work ok.
    Also I know it is scary with the stock cooling fan raging and laying over the fender to reach the distributor. A 3 foot by 3 foot piece of 3/4 ply wood laying on the air filter to the front grill makes setting the timing on a suburban actually comfortable. You can lay head towards the drivers side and reach around the edge of the plywood to see the timing marks and use your left hand to move the distributor.
    Thats KentMore tool 3x3x3/4-1 for medium duty service vehicles.
    Avatar is my motor 800 RPM 184ft Lbs Torque 18 inches x 18 inches x 9 inches thick external combustion engine.

    98 WS-6 full tube chassis rally car Aluminum Block LS2 (soon to be LSX 376)(in Storage)
    95 Suburban 6 inch drop, Zoomies, Tri-Y Headers, Pioneer DVD in Dash (Soon to Be LT-4).
    95 Caprice 9C1 Fleetwood Brougham Interior, LT-4 (retired)(Engine Donor for new truck)
    2002 Seville STS

  15. #30
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    Quote Originally Posted by daveosx View Post
    450 HP Hour requires 9.16 Gallons per hour of Gasohol.
    Mechanical efficiency of stock motor is 49% with new pistons rings increased compression and roller cam 76-80%

    At 6lbs per gallon thats 54.96 PPH

    The injectors will provide at stock fuel pressure 336HP no problem.
    At 18psi like I recommend they will flow reliably at 74-75PPH
    My experience and wideband both disagree with your HP potential of the TBI injectors.

    350 with TBI heads, stock TBI cam, 1.6 roller rockers, Edelbrock 3704 intake manifold bored to 2", 454 TBI unit with 350 injectors, doug thorley tri-y headers, dual 2.5" exhaust into a X-pipe in my 1983 G20 van put down right at 200 RWHP and 300 RWTQ. Stock injectors at 14 psi were insufficient over 4,000 rpm to feed the stock long block. They went static, duty cycle above 100% and the engine misfired terribly and fell flat on its face before 5,000 rpm. I swapped to a Marine regulator and injectors from a 405 HP Mercruiser 502. Those are high pressure 61s that deliver 105 lb/hr @ 32 psi. I could turn the engine 5,500 rpm after with no fuel issues. I put a Weiand 177 on the same engine and used a rising rate FMU. At 10 psi boost it took 50 PSI of fuel pressure to feed the engine. I went 13.7 @ 101 mph in a 5,300 lbs G20 van with the Weiand 177 on the stock longblock, 700r4 with stock 1,600 rpm converter, and 3.08 gears turning P295/50R17s.

    61# injectors are good for about 72 lb/hr @ 18 psi. I have once flowed one on an injector bench in 4 psi increments from 10 psi through 62 psi. The high pressure injectors will reliable open up to about 70 psi, however above about 50 psi the increased pressure does very little to increase flow.
    Last edited by Fast355; 1 Week Ago at 03:11 PM.

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