'93-'95 TPI Conversion - Not what you think!

[HaulnA$$]

As some of you know, I have been working on a TPI conversion for my '94 TBI truck for some time now. At this point, you're probably telling yourself, big deal, a bunch of people have done a TPI on a '94. This is true but up until now it involved a piggyback ECM in addition to the factory PCM but how many have done it using only the original TBI PCM. I have. I successfully converted a TBI PCM to run a port injected setup, any port injected setup although I chose TPI for this project just to make sure everything would work properly. Again, some of you are saying to yourself, Edelbrock did this years ago. True, but the Edelbrock setup is a hack job hybrid P.O.S. as many who own one will attest to. I did it right. Instead of using port injectors with a TBI PCM using a TBI injector firing strategy (TBI PCM's fire each injector alternately every other distributor reference pulse), I modified the PCM and Memcal to fire the injectors in a port batch fire strategy (batch fire fires all 8 injectors once every crankshaft revolution or every 4th distributor reference pulse). I used saturated injectors so I also modified the peak and hold TBI injector drivers to run port saturated injectors although port peak and hold injectors will work with an external driver box. I considered using P & H injectors so I also designed a driver box to drive them but I never used it. For reference, this is on my '94 ECSB TBI truck with the original 305 which my son now drives. I removed the 383 stroker that I was running when I drove the truck which I built a few years ago and was putting out just over 500 HP at 5500 RPM and 510 FT/LB of torque at 4500 RPM because I just couldn't let my son drive with that much power. I was running the stroker with the original PCM but I had a 900 CFM 4BBL Holley TBI with a 2 channel 4 driver external P & H driver box similar to the one I came up with for the TPI. I worked long and hard on this project to make sure that it was done right. I won't go into all the details but I put more time into this than I am willing to admit. I am considering making kits for sale depending on how many people are interested. I did not enter this project with the intent of making money on it. EFI is my hobby. I am an electrical engineer and have been a gearhead all my life. I rebuilt my first engine at the age of 14. I just believe that if I make all the info public, some jerk will step in and steal it for profit so if there is to be any profit to be made, it may as well be made by the person who did all the work. I have attached some before and after pics.

[HaulnA$$]

Oh Yeah, just in case there are any nay sayers out there. Here are some pics from my oscilloscope of the pertinant waveforms. The first pic is of the DRP's on the top and the injector pulses on the bottom. As you can see, the injectors fire every 4th DRP. The second pic is of the two injector drivers in the PCM. They both are firing at the same time. A.K.A. batch fire mode. HTH

[airdeano]

'grats!
your ECM mods was using the injector driver switch? soldering
the resister to the drivers?
again congrats!!

airdeano

[HaulnA$$]

Originally Posted by airdeano

'grats!
your ECM mods was using the injector driver switch? soldering
the resister to the drivers?
again congrats!!

airdeano

aireano, it figures you'd be the first one to reply.

[airdeano]

im a recovering auto perv....
seein' a nekkid nitrided, knife-edged crankshft... mmmmmm
important information deserves replies and engaging
banter....

airdeano

[HaulnA$$]

Originally Posted by airdeano

im a recovering auto perv....
seein' a nekkid nitrided, knife-edged crankshft... mmmmmm
important information deserves replies and engaging
banter....

airdeano

Believe it or not, I will be in AK next month, over July 4th weekend, at Lake Catherine, maybe we can chew the perverbial fat? LMK.

[chevyz71man]

That makes me want to do my lt1 intake conversion even more.

[Beau Burnett]

Wow. Congrats. That is astounding.

With your TBI knowledge, can you assess how difficult it would be to modify a stock GM TBI/module so that the computer and sensors would operate two TBIs running on something like an C-26 dual quad intake, rather than a single TBI? I believe Holley's projection does that, but at approx. $3K.

[pb_]

Nice job. Something else for me to think about :)

[YenkoST]

Awesome....nice conversion. When I did my conversion, I used the '730 ECM and converted the wiring harness over. Again...good looking TPI system you got there!!

[1Bad454]

Any suggestions on upgrading the Edel MPFI as far as injector firing goes? I will be stepping up to 44# injectors in the near future and a dyno tune as well.

[HaulnA$$]

Originally Posted by Beau Burnett

Wow. Congrats. That is astounding.

With your TBI knowledge, can you assess how difficult it would be to modify a stock GM TBI/module so that the computer and sensors would operate two TBIs running on something like an C-26 dual quad intake, rather than a single TBI? I believe Holley's projection does that, but at approx. $3K.

That would not be hard at all. There is a guy I know who is using this PCM to run two truck TBI's on a Corvette crossfire intake. All you need is an external driver to drive the extra 2 injectors. The box I used on my 4BBL Holley would do the trick. It goes between the PCM and injectors and has 4 P & H drivers in it. As far as sensors go, you would only use the Throttle position sensor from one of the two TBI's. Everything else would be fine. HTH

[HaulnA$$]

Originally Posted by 1Bad454

Any suggestions on upgrading the Edel MPFI as far as injector firing goes? I will be stepping up to 44# injectors in the near future and a dyno tune as well.

Whay year is your truck? If it is not a '93-'95, I can't help you.

[1Bad454]

It's a "90". The last three digits on my ECM are 747. I have a few other routes that I'm looking at but if I could utilize the stock ECM that would be nice too.

[Red94Chev]

Nice job!! I think you should write a tech article on your TPI swap on how to do it right the first time. Might drum up some business for your EFI tuning project. Do you think you could help me tune my 94 with the Edel MPFI, cam, heads, etc.?

[jeep45238]

Very perty. Your engine bay is immaculate also, by the way.

[HaulnA$$]

Originally Posted by Red94Chev

Nice job!! I think you should write a tech article on your TPI swap on how to do it right the first time. Might drum up some business for your EFI tuning project. Do you think you could help me tune my 94 with the Edel MPFI, cam, heads, etc.?

Thanks to all for the kudos. I have considered doing a tech article, maybe later. As for tuning your ride, no problem. I can even convert your PCM. Do you have any tuning experience? If so, which tuner software are you using? Which datalogger? If you want, you can contact me offline. HTH

[airdeano]

Originally Posted by HaulnA$$

Believe it or not, I will be in AR next month, over July 4th weekend, at Lake Catherine, maybe we can chew the perverbial fat?

yeah, c'mon up.. ill give ya a nickel tour with a brewski.
state your flavor...
304 smokey lane, north little rock, arkansas 72117

airdeano

[airdeano]

Originally Posted by 1Bad454

Any suggestions on upgrading the Edel MPFI as far as injector firing goes? I will be stepping up to 44# injectors in the near future and a dyno tune as well.
It's a "90". The last three digits on my ECM are 747. I have a few other routes that I'm looking at but if I could utilize the stock ECM that would be nice too.

haulin' this is possible as to use the 95 c/k2500-3500 7.4L
manual trans ECM/EPROM. since hes a th400 the trans side is
omitted and the tuning still is a 95 7.4 on a red/blue
computer. simply repin and tune with the P/H box.
the th400 kick down will have to plumbed to a microswitch on
the pedal or throttle (neat 3-holes to fashion a bracket and
switch)

airdeano

[HaulnA$$]

Originally Posted by airdeano

yeah, c'mon up.. ill give ya a nickel tour with a brewski.
state your flavor...
304 smokey lane, north little rock, arkansas 72117

airdeano

Cool, I'll be there Thur. July 6 in the afternoon. As for the brew, anything will do as long as it is not light beer.

Originally Posted by airdeano

haulin' this is possible as to use the 95 c/k2500-3500 7.4L
manual trans ECM/EPROM. since hes a th400 the trans side is
omitted and the tuning still is a 95 7.4 on a red/blue
computer. simply repin and tune with the P/H box.
the th400 kick down will have to plumbed to a microswitch on
the pedal or throttle (neat 3-holes to fashion a bracket and
switch)

If I'm not mistaken, the manual tranny PCM's use a 160 baud ALDL datastream. It would work but a port setup is a PITA to tune with only 160 baud data. I'm pretty sure I can make an auto tranny computer work with a TH400. The code is there, it is just not used. I'll have to check it out on my PCM simulator bench. Another project added to the already growing list. HTH