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TBI tp TPI Conversion - Is this possible
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Author:  tomj55 [ Sun Nov 18, 2007 8:55 pm ]
Post subject:  TBI tp TPI Conversion - Is this possible
I just picked up a 1990 D150 as spare parts for my 1987 D150. It has an unusable 318, but a functional 2-bbl TBI system. I am thinking about using the TBI system on my slant-6.

Question: Is it possible to convert the TBI system to a TPI system by replacing the 2 injectors with 6 lower capacity injectors? I know the electrical loading of 4 additional injectors might be one issue.

Thanks,

TJ
Author:  SlantSixDan [ Sun Nov 18, 2007 9:10 pm ]
Post subject: 
I have an '89 D100. Same 318 engine, same TBI system. It is a very poor system. Cruddy hardware driven by cruddy software. I have spent a great deal of time and effort getting to know this system, and while I have been able to tweak it a little to make it marginally less mediocre, it would definitely not be worth the effort, time, and cost to put this crapmess on a slant-6. And even if you were bound and determined to do it, you'd "want" the parts from a 3.9 V6...and even those would need heavy modification.

No, it is not possible to use any of the TBI parts to run a TPI system.
Author:  Sam Powell [ Mon Nov 19, 2007 4:29 am ]
Post subject: 
The fuel tank and pump might be worth using, as well as the fuel return lines. I have not seen this set up, so cannot speak to how well they are designed and executed, but the fuel tank and lines on a carbureted system represent a major investment of time and engineering to upgrade to EFI. Dan is more qualified to answer this question now that I have raised it.

Sam
Author:  tommj55 [ Mon Nov 19, 2007 6:46 am ]
Post subject:  Thanks for the input.
Dan/Sam:

I appreciate the input; although I was hoping for better news. I thought I may have found a relatively inexpensive way to get EFI for my slant-6. As Sam suggested, I will probably pull the tank, so I can use the pump and lines. It appears that I'm forced into a significant $$$ investment to set up any worthwhile EFI system.

Thanks,

TJ
Author:  sandy in BC [ Mon Nov 19, 2007 8:38 am ]
Post subject: 
If you were putting a slant six where the 318 was I would certainly consider going with the stock TBI....all the wiring , fuel lines....in place.

Our hated 88 Dakota loaner/yard truck has the same TBI and I have to say that it runs better than any carbed 3.9 v6 would.....
Author:  SlantSixDan [ Mon Nov 19, 2007 9:26 am ]
Post subject: 
Quote:
I have to say that it runs better than any carbed 3.9 v6 would.
That's certainly damning with faint praise! :lol:
Author:  Matt Cramer [ Mon Nov 19, 2007 4:45 pm ]
Post subject: 
Quote:
I have an '89 D100. Same 318 engine, same TBI system. It is a very poor system. Cruddy hardware driven by cruddy software. I have spent a great deal of time and effort getting to know this system, and while I have been able to tweak it a little to make it marginally less mediocre, it would definitely not be worth the effort, time, and cost to put this crapmess on a slant-6. And even if you were bound and determined to do it, you'd "want" the parts from a 3.9 V6...and even those would need heavy modification.

No, it is not possible to use any of the TBI parts to run a TPI system.
I've got a hard time figuring out which would be the bigger headache there. Unless you could burn a custom EPORM (routine with the GM guys, nearly impossible in Mopars from what I hear), the V8 ECU would think your RPM was 3/4 too low, while the 3.9 ECU would think it was hooked to an odd fire engine.

The fuel tank and fuel delivery system could probably be reused. Maybe you could graft the TBI on there and use Dan's injector mod too, even though a TBI isn't the greatest. I'd suggest a Megasquirt for the ECU, but I am a bit biased. :) The other cheap ECU alternative is a chipped GM ECU, although I got into Megasquirt because I found the homemade EPROM stuff too intimidating.

One tip if you're doing ECU transplants: Mopar Lean Burn and GM computer controlled HEI distributors use near-identical pickups.
Author:  tomj55 [ Mon Nov 19, 2007 6:28 pm ]
Post subject: 
I have been leaning toward an MS ECM kit, but I was also hoping to salvage a good portion of the D150 TBI system and avoid scouring the nearby junkyards for usable parts.

I'm still rebuilding the engine, so I have ample time to ponder my options before I settle on a fuel injection system. But, Keep your suggestions/advice coming. I appreciate the input!!!
Author:  Sam Powell [ Mon Nov 19, 2007 7:46 pm ]
Post subject: 
I think that TB could maybe be used with MS ECU. You likely would want to go with smaller injectors for idle quality.
Sam
Author:  tommj55 [ Tue Nov 20, 2007 6:31 am ]
Post subject: 
Hopefully, I can make it work. If not, I'll just need to spend additional $$$ that I would have had to spend in the first place.

I'll keep you all posted on my progress.

Like they say:"Half of the fun is the journey."
Author:  Twisted Sixer [ Thu Apr 10, 2008 12:29 am ]
Post subject: 
Quote:
No, it is not possible to use any of the TBI parts to run a TPI system.
This comment isn't entirely true the throttle body(as a throttle valve), map sensor, TPS, and idle air control motor would all work. The injector drivers in the computer would even run 2 batches of the right kind of port injectors.If you had a V6 computer it would run if the injectors were sized right but would stumble and belch black smoke every time you stepped on the gas because the accelerator pump values in a tbi computer are much more aggressive.(not a problem with megasquirt) Also the fuel pump may not put out enough pressure for port efi.

If you leave it throttle body and the injectors are too big they will tolerate the fuel pressure being turned down a little but I don't think it will be necessary with megasquirt its a faster computer running better resolution than the factory one.
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