TBI to TPI on a STRICT budget

[ThatDude-98]

Hello, I have done some looking around and discovered you can splice the 8 inj for TPI into your existing tbi harness and make a tpi harness. I know you have to change knock sensor and lengthen TPS and IAC wires as well. This link: chrome-extension://bpmcpldpdmajfigpchkicefoigmkfalc/views/app.html talks about taking a MPFI v6 ECM and adding resistors and a jumper wire to make it work to run TPI v8. I am curious, I have a G10 tbi 350 parts van (unsure of exact year, ECM or mask) and a complete tpi assy (minus ECM and harness.) I plan to convert the TBI harness to a TPI harness. My question is can I mod the G10 van ECM as the link shows to run tpi? if so I will have a complete tpi setup (base, plenum, runners, tb, fuel rails, inj, harness), ecm, etc for peanuts. 3 more questions: will the tbi distributor work for tpi? in the link it talks about changing injector offset and things of the like..from what i gather I just have to add the resistors and jumper wire to the tbi ecm to make it work. right or wrong? IF I were to add bigger than stock tpi injectors then i would have to change bpw offset, etc. Last question, i will have to put a tpi bin on the tbi chip or find a tpi chip correct? I understand the tbi ecm is slow and the MPFI v6 ecm is probably way faster, but, again I want to do this as cheap as absolutely possible if i can. I am excited to hear input. Thanks- AJ

[dave w]

Very low cost option . . . Post #6 TPI to MPFI (aka TPI) http://www.gearhead-efi.com/Fuel-Inj...Information-0D Soldering Skills Required

dave w

[ThatDude-98]

Thanks dave- so if i were to solder the resistors and add the jumper and change constants, do i have to change anything else such as injector offset if i use oem tpi injectors? Also does it HAVE to be an 8625, 6395, 7427 or can I use whatever tbi ecm i have?

[dave w]

There is the option for converting TBI computer to TPI computer by re-pining the TBI computer to a TPI computer, but that adds the cost of a computer.

The link posted above has to be the 8625, 6395, or 7427

Basic tuning tip, factory this, factory that, factory everything . . . means no tuning.

Basic tuning tip, something not factory . . . tuning required.

dave w

[ThatDude-98]

Thanks for the heads up Dave. So say I was to have the soldering done, jumper done, switches set and now it’s time to change the injector offset. Is this how I’d do it?: Fuel Injector Constant
This constant (or table in some PCMs) tells the PCM how long to pulse the injectors at various airflow/MAP points. It should be adjusted for any fuel pressure changes compared to the rating at what the fuel injectors were flowed.
For example, if you have a 30# injector that was flow-tested @ 43.5 psi (standard GM rating), but your actual fuel pressure with no vacuum is 48 psi, that means that 30# injector will flow more than 30# in your vehicle (31.51# to be exact). To correct flow rates for fuel pressure changes, divide the new/current fuel pressure (48) by the injector's rated pressure (43.5) and then take the square root and multiply that by the injector's rated pressure. You'll see that higher fuel pressures will give you a larger constant (the PCM will then pulse a shorter time), and lower pressures will give a smaller constant (the PCM will pulse a longer time).

[Fast355]

Hello, I have done some looking around and discovered you can splice the 8 inj for TPI into your existing tbi harness and make a tpi harness. I know you have to change knock sensor and lengthen TPS and IAC wires as well. This link: chrome-extension://bpmcpldpdmajfigpchkicefoigmkfalc/views/app.html talks about taking a MPFI v6 ECM and adding resistors and a jumper wire to make it work to run TPI v8. I am curious, I have a G10 tbi 350 parts van (unsure of exact year, ECM or mask) and a complete tpi assy (minus ECM and harness.) I plan to convert the TBI harness to a TPI harness. My question is can I mod the G10 van ECM as the link shows to run tpi? if so I will have a complete tpi setup (base, plenum, runners, tb, fuel rails, inj, harness), ecm, etc for peanuts. 3 more questions: will the tbi distributor work for tpi? in the link it talks about changing injector offset and things of the like..from what i gather I just have to add the resistors and jumper wire to the tbi ecm to make it work. right or wrong? IF I were to add bigger than stock tpi injectors then i would have to change bpw offset, etc. Last question, i will have to put a tpi bin on the tbi chip or find a tpi chip correct? I understand the tbi ecm is slow and the MPFI v6 ecm is probably way faster, but, again I want to do this as cheap as absolutely possible if i can. I am excited to hear input. Thanks- AJ

You can and I have done it. I was less than thrilled with the TPI. Gave up off-idle torque and top-end horsepower for a little more torque in the midrange. From 1,000-5,000 the TBI had higher average tq and hp. TPI did not even break even with the TBI on a dual plane manifold until 2,700 rpm and then fell off drastically above 4,200. With a 4L60E and 3.08 gears the torque loss was noticeable 90% of the time.

[ThatDude-98]

You can and I have done it. I was less than thrilled with the TPI. Gave up off-idle torque and top-end horsepower for a little more torque in the midrange. From 1,000-5,000 the TBI had higher average tq and hp. TPI did not even break even with the TBI on a dual plane manifold until 2,700 rpm and then fell off drastically above 4,200. With a 4L60E and 3.08 gears the torque loss was noticeable 90% of the time.

@Fast 355 do you know how to calculate the injector offset? I have access to one of the correct tbi ecm for TPI conversion. If this is all more work than it’s worth I may just end up buying a 730 ecm and be done with it..use stock injectors then i won’t have to mess with BPW OR OFFSET thanks

[tayto]

Fast, if geared accordingly, would TPI be a more worth while swap? Or is it a better system for a smaller engine (305)?

[ThatDude-98]

found this 4 min video on youtube: https://www.youtube.com/watch?v=Id7zc4NjQfE from what I gathered, you can still run the engine just fine and tune it without touching the offset (aka lag aka deadtime) jjust the afr wont be as accurate. Can anyone confirm, is this correct?

Edit: can i just leave the TBI chip in my converted TBI ECM, then download a 165 or 730 bin and then the offset and pulsewidth would be correct? obviously I will be modding the engine so I'll tune the afr, spark, etc.

[tayto]

http://www.gearhead-efi.com/Fuel-Inj...oltage-Offsets

[ThatDude-98]

http://www.gearhead-efi.com/Fuel-Inj...oltage-Offsets

great read, thank you. So if I understand correctly in whatever editing program (TunerPro, Tunercats, etc) I use just zero the actual offset and add my estimate “offset” to the Base Pulse width, anyone correct me if I’m wrong. Sounds easy enough! Thanks Tayto

edit: I understand offset/ lag / dead time doesn’t need to be perfect just want to confirm this is how it’s done.^^

1-30-2022 Edit: If you use TunerPro, injector offset is set in the BPW table, select offset and either add or subtract offset. To whom it may concern, don't get caught up on offset, it isn't THAT big of a deal. You have a few choices for finding offset: your injector factory specs, or get the injectors 'tested', OR add rough estimates into the BPW table as I described at the beginning of this paragraph. Hope this helps someone.