TBI-to-Vortec conversion

[General Stalin]

First I want to say hi all.

http://www.cardomain.com/ride/3004759

There is my truck. 1995 Tahoe 4x4 4-door in the midst of being tranformed into a rubber-burning monster.

If you read the bottom of the page you'll see I am doing a 350 rebuild at the moment. Originally I was going to buy new Vortec heads for it and keep it throttle body injection... but then I found a blessing...

I went to the boneyard today to find a set of lugnuts and a new center-cap for my wheel (been missing one for months) and to my suprise they had a new turkc there. a 1996 Suburban with all the engine components still intact. So, not one to pass up an awesome oppurtunity (luckily I had my tools with me), I went to town with the socket wrench and yanked the Vortec multi-port injection manifold and both Vortec heads.

In a perfect world, I wanted my rebuild to be multi-port injection, but buying the kit to convert TBI 350's to multi-port is just a big investment. Now I was able to get a full multiport manifold WITH a pair of Vortec heads for like $170.


My question for all of you is this: is there a way to get the stock 1996 Vortec fuel injection system to work with my 1995 Tahoe WITHOUT buying a Vortec wiring harness and buying an OBD2 computer? I'm guessing not, but I am really trying to avoid throwing a bunch of money at this conversion as I am not loaded and am trying to get the best bang for my buck. There is an assload of snesors involved and it seems like a huge pain.

It just seems real complicated and potentially costly. I guess if it came down to it, I could go back to the junk yard later this week and get the wiring harness and computer chip out of that Suburban. Just hoping maybe some of you had tricks, solutions, or suggestions to give me.

 

[treepete]

95TwinTT should be able to offer you some advice.

I think youll need the rest of the components and junk from that suburban, or a whole new computer setup.

good find at the junkyard though.
and welcome.

 

[General Stalin]

Ugh, yeah you're probably right... I just wish there was a way to get around some of the sensors. The Vortec setup uses something like 4 O2 sensors... that's retarded. 2 on each pipe before the cats and 2 after the cats. Problem there is that I plan on getting true duals with NO cats, and having to route thread a handful of sensors into my exhaust system does not sound very appealing. I think 95TwinTT uses a Edelbrock Pro-Flo system or something of the like, which is a straight conversion from TBI to MPI. It costs some money, but I believe that route you can use most of the stock sensors in the TBI setup with a couple addons or something.

 

[GMCYukalade]

why not just use the wiring from that burb? - and when it comes to the back two o2 sensors since your tbi doesn't use them - put in some o2 Simulator's
http://www.afterthoughtsauto.com/o2sim.html

 

[General Stalin]

Wow, those O2-simulators are a really handy and an awesome idea. thanks for the info man. As far as the wiring harness... I went to the junkyard today to see if I could pull the wiring out of that Suburban, and I think I decided I would rather just throw down the money on the painless harness. I DID save my self a boatload of money by taking the computer out of the Suburban, so now I have OBD2 without having to spend hundreds of dollars. But again, I decided against pulling the harness because after a little inspection I realized it would be a terribly grueling task, especially where all the electronics for the entire engine compartment and dash are all intertwined together and it would take a lifetime to follow the computer wires through the harness so I can JUST pull the wires I need, plus fuse boxes and a relay box etc.. Plus The entire dash needs to come apart and the whole driver's side corner of the engine compartment... on top of that, I'm pretty sure it was missing a few plugs and wires anyway. There were some cut ends (not all my fault) and such.

 

[95TwinTT]

The Painless wiring harness is definitely the way to go. You will have to do a little research to make sure the other pin out’s for the body and trans, are compatible on the OBD2 computer. It looks like the Painless only uses two of the four plugs on the ECM.

OBD 1 & 2 are different enough you will have to do some home work. I stepped off of the OEM platform, because it was impossible to deal with OBD-1 with “forced inductionâ€.

It is for that reason, I’m not much help for your project, other than to caution you to pay attention to the details. Maybe Painless has other harness application beyond the engine. I use separate computers for both the engine and the trans. My stock computer is still in play for dashboard and other odds and ends.

I share your enthusiasm for this version of the Tahoes. I wouldn’t trade mine for a new corvette. They aren’t fast enough. Lol Good luck with your project.

 

[General Stalin]

Well, I believe that Painless harness covers all the computer wiring (also, the harness in question is specificially made to work with the factory 1996-1999 OBD2 computer... which I took of that 'burb). It covers the injection system, transmission (including the tach), ignition timing, dashboard diagnoistics, brakes... am I missing anything?

I know relatively nothing of my current OBD1 computer, so there would be no "difference" in the case of learning the OBD2 computer. I know OBD2 is a lot better and it's very programmable, so that is awesome. If the problem comes up... is it actually possible and easy to run my OBD1 computer chip for certain controls, and my OBD2 computer to run the rest?

Thanks again for all the help. TwinTT, I have been drooling over your truck on Cardomain since like a month ago. That thing must be ridiculous, very awesome man. I tried commenting on it and rating it... but it won't let me? There is no option to comment or rate it, did you disable it for that vehicle? Either way, very awesome. I could only dream to have the knowledge (and money...) to do to mine what you did to yours.

 

[95TwinTT]

Hey thanks for the kind words, I have the comments part turned off at cardomain. I just use it for a place to hold some pictures.

Here is the Painless picture of the wiring harness. From what I can see, they only have two of the four ECM, plugs on the new engine harness, unless that is a third one sideways, in the upper left hand corner. The things that will be plugging into the other ECM ports, will be things like cruise control, brakes, 4 wheel drive controls, etc.

I just took a look at the installation manual and from what they are saying, everything is there. The other plugs must be in the picture, but I can't spot them. They do mention that the computer should be reprogrammed to eliminate any features not being used.

There are a few different connections on the 4L80e trans that are not used on the 4L60e. It would be good if they had a universal harness that covers them both, in case you decide to move up to a 4L80e in the future.

I have heard nothing but good things about the Painless products. I'm sure they have it covered. The installation manual looks very detailed. You might want to go through it before ordering the harness. It will be great to have nice new, OEM connectors on everything.


Did you say this was your daily driver? :cool2

 

[General Stalin]

Well, that is also the picture of the "Extra Long" harness, if you check out the photograph of the standard size one (the wires are layed out differently in that picture) it seems that there are four visible wide plugs. Also, if you read that insturction manual .pdf file, there are provisions for 4l60e AND 4l80e. The 4l80e uses some kind of speed input sensor or something, but the harness does have that from what I understand, so this just may be the way to go. Maybe if I'm lucky then I can get the tranny off of that 'burb too, because it is a 3/4 ton 2500 model. I was going to get the rear-end the other day, but it's not posi so meh. Just a large open gear. Your welcoem for the compliments by the way, your hard work and effort deserves it at least hehe.

 

[95TwinTT]

That must be the 4L80e in that 3/4 ton Suburban. That would be great if you can get the trans and all the goodies connected to it. I think even the flex plate is different from the 60. If it's a 4x4, the transfer case could be traded for the 2x4 tail section parts of the trans.

Great find, and it sounds like you are well on your way to having a bullet proof drive train. Keep us posted on your progress.......... :thumbsup:

 

[General Stalin]

Bah, ideas are being tossed back and forth way too much in my head. After looking what's on my plate if I want to convert to Vortec, I almost want to stick to my original plan:

Holley 670 CFM TBI unit, and the GM Vortec TBI manifold.

It's really quite a pickle. I could use some helpful opinions/suggestions on this.

I know what heads and what cam/lifter/rocker setup I want. The fuel delivery is what is difficult to decide on. I know I DON'T want carbureted; I definitely want fuel injection. It is more reliable and more efficient.

On the one hand: I could buy a Holley 670 CFM throttle body, and the GM Performance parts throttle body injection manifold for Vortec heads. That is like ~$780 all together. I could use my stock wiring harness and computer system, I would just need a custom burned chip when all is said and done.

On the other hand: I got myself a Vortec central multiport fuel injection manifold, fully intact, and an OBD2 computer. The manifold was only $16 (they messed up and entered "exhaust manifold" instead of "intake manifold" so it was cheaper than it was supposed to be) and the computer was $27. To adopt that into my setup I will need a $700 wiring harness, and I will need to go BACK to the junkyard because I need the vortec intake assmebly because it needs the mass air flow sensors that are in it. Either that, or buy some kind of aftermarket K&N cold-air setup, but those are a few hundred bucks. I am also going to need to get a computer adjustable distributor. It seems like a big hassle and probably more money, but OBD2 us much better to work with, and Mass Air Flow is a MUCH more accurate way to determine fuel mixture than Manifold Absolute Pressure (which TBI uses).

What should I doooo? I'm assuming there is no way to get my OBD2 computer to work with throttle body injection? I'm also guessing there is no way to get throttle body injection to utilize a MAF sensoring technique? Or maybe I'm wrong on both these counts? I don't know. I'm real torn, guys.

 

[95TwinTT]

There is also the issue of cam sensor and crankshaft sensor, that are needed for full sequential injection.

I assume the cam sensor is part of the distributor and the crank sensor should be in the bottom of the timing cover.

I use a modified 96 timing cover on my 95 engine to read a custom chopper wheel inside the cover. The 96 cover has the sensor on the bottom. It is hard to see from above with the harmonic balancer in place.

I think you can get everything you need from the two injectors, and it would take a lot less effort.

I put my first supercharger onto a stock 95, throttle body engine, and it was fantastic. :cool2:

 

[General Stalin]

Well, the 96 models are not "full sequential" injection. It is just one huge injector with 8 passages to direct the fuel to each cylinder. I believe the injector fires twice per full engine revolution. I DOES have a cam sensor, which is where the computer-adjustable distributor comes in... and it may even have the crank sensor too as far as I know. I just new the earlier Vortecs are not TRUE sequential injection.

 

[95TwinTT]

Well, the 96 models are not "full sequential" injection. It is just one huge injector with 8 passages to direct the fuel to each cylinder. I believe the injector fires twice per full engine revolution. I DOES have a cam sensor, which is where the computer-adjustable distributor comes in... and it may even have the crank sensor too as far as I know. I just new the earlier Vortecs are not TRUE sequential injection.

Seems to me if they are just the tubes being fed with "two" injectors, it would not make much sense to waste any time screwing around with it.

I have never looked at one of those setup's but it must have had some drawbacks, since they abandoned that idea quickly.

Kind of like the "cross fire" injection. Looks good on the drawing board, but not much good in reality. I owned one of those proto types for a while.


EDIT //

OOps, it does have eight injectors on that "Central SFI" They claim it is Sequential, with 8 injectors feeding those tubes. Looks like they had them for at least two years. The manual is a little fuzzy on when they went to Port Injection. The 7.4L V8 used Port Injection from 96 and later.

It still sounds like these Central SFI units would be more difficult to modify. I don't know of anyone that has used them to go above a stock application. The manual talks about the injectors being together between the upper and lower intake manifold and feeding the fuel through a tube to a "poppet valve", located in each cylinder port. Sounds like both Rube and Goldberg, were in on this design.

I have changed injector sizes so many times, I would want to know how accessable these injectors are and if they can be modified down the road.

I'm kind of on the fence on this one. Mostly because I don't know anything about these central SFI systems. Sorry I can't be more help on this one. Good luck either way..........

 

[General Stalin]

Well, I think I decided that the multi-port injection from the Vortec engine is probably going to be a waste of time and money. It would probably give me hardly any power gains for the amount of hassle and money it will cost. The Vortec heads are where all the power comes from in those Vortec engines anyway.

The '87-'95 models advertised 200 hp, and the '96-'99 models advertised 255. That 55 hp is probably almost all contributed by the new Vortec cylinder heads; hardly by the new fuel injection system. Besides, it probably wouldn't even make much of a difference in fuel economy, because the EPA estimated fuel mileage on the Vortec engine vehicles is like 1 mpg better than the older models.

As far as being customizeable, I know you can probably change injectors and such to get more pressure, and I also know you can buy a new injection "spider" unit (which is probably really expensive) that has control modules wired onto each of the 8 injectors, and with a little computer editing, you can get TRUE sequential injection out of these "CSFI" unites. As in, each injector fires independantly at the beginning of the intake stroke for it's correspending cylinder.

The more I think about it, the more it doesn't seem worth it. The only thing that is a little lame about staying with TBI is deal with OBD1. I would probably want to ship my computer chip out to a programmer company or something and give them my setup information to have them custom edit/burn a new chip for me.