using the TBI ECM for spark only and bypassing the TBI itself-- without SES light

ok, how do i do it?


here are my thoughts on it.


i can set some resistors to simulate the injectors being there
i can either set the O2 to a resistance, or use a simulator, or disable ti somehow
i have no idea how to set the TPS on this thing







ideally, heres what i want:

i want to retain my stock wiring, still use the computer controlled distrib and just burn chips for my spark table.

then i can plop a carb on top for now.


i do not want to set the SES light...

how do i do it?

 

Pablo's the man you're looking for. He is currently doing the same thing and can probably help you out.

 

It is rather easy. On the diy-efi site (which is still down) there is a paper that goes into detail on this. Basically it goes like this:

No need to use resistors to fake injectors.
If the O2 sensor is no longer present disable the error codes for it (13, 44 & 45).
Disable the following error codes: MAP high, TPS hi, TPS lo, EGR.
Disable the EGR.

I think that is about it. Still need the MAP sensor. Do not need the TPS (can leave it plugged in and laying on intake). Long term it would be better to graft it onto the carb.

RBob.

 

this may be a stupid question...but why would you do that??? I am not sayign it becuase I question it....I am just clueless.

 

One reason is that it makes it easier when retro fitting a TBI system to a vehicle that didn't come with one. Get it up and running with SA control then add in/on the fuel control.

Another reason is so that one may switch between TBI & carb for comparison purposes.

Even if staying with carb (such as track usage only), using the ECM as a timing computer makes it real easy to setup the SA curve. No more mechanical gizmos to depend on.

RBob.

 

AHHHH....Now I see said the blind man...thanks!

 

If you dont have all the chip burning stuff already it might be better to just go with a mech. dist. the only way i see it being cost effective is if someone will mail you out a chip with all that dissabled and a good spark curve for you carb. Even though all the chip burning stuff can be had it is only 150 for a mech dist..


i just bought all new parts for my dist and would love to keep my efi dist. but the chip seems like a hassle to do it.


Is there even anyone that would help people out and send them a chip like that??

Shawn

 

$150 buys you the equipment to program your timing tables .... and still keep a rev limiter, detonation protection, tcc lockup, the list goes on and on.

 

i am not knocking the idea.. hell we seen pablo do it and now we notice it can be done pretty easy..

i am very interested also but i wonder how hard it would be to learn how to burn and all..

Shawn

 

rbob covered it

its super easy to do


is it worth getting the chip burning equipment to do it? well, depends on what you are doing. If you are the type of person that is into testing and tuning and such then yeah definately. If you are the type of person just throwing a carb on there to simplify things to avoid the complex computer mumbo jumbo then no, get a mechanical dist. Its going to cost you a little more to do the chip burning thing than to get a mech. dist. Not a whole lot though.

 

Heres a pretty stupid question.....you can use the in tank fuel pump, right? I'm thinking about doing what you did pablo, just to get peak performance and to compare what the 4bbl carb runs compared to the 4bbl TBI(when I get it that is).

 

Just need a bypass style regulator to drop the fuel pressure (a dead head regulator will kill the pump).

RBob.

 

mmk, so you can just disable the error codes that it would set... cool.

anyone have the in depth paper that used to be up on the site?

 

Site's back up, note that this paper is in particular for the'7747. Also note that the '8746 is the car version of the truck ('747) ECM:

http://www.diy-efi.org/gmecm/ecm_inf.../747_ignition/

There are differences, but no show stoppers.

RBob.

 

thank you VERY much.