So, I'm swapping the a 3.4 engine from a '94 Camaro, with the 2.8 engine from my '85. I'm going to use the ECM and manifolds from the 85. I'm unsure now as to what fuel injectors to use.

I know the 2.8 ones are too small, but I don't know how the ECM pulses the injectors and if the 3.4 injectors would also be to small.... On some of the various websites describing such swaps, 4.3 injectors are mentioned, although that seems to be a bit too large..... What injector size would you folks recommend?

Thanks,
Dave

 

It really depend on what modifcations you plan on doing to the engine and what kinda power it's expected to make...stock for stock the 2.8 should have roughly 12lb/hr injectors and the 3.4 should have about 16. thats at stock power levels...120 for 2.8 and 160 for 3.4. And i don't see how 4.3 injectors would work...totally diffrent design induction system on all 4.3's from the multi port used on f-bodies

 

Use the stock 3.4 injectors if the engine stays stock.

 

onebad89RS and KrisW, thanks for the replies.

Apparently the internet articles that I was reading about the 2.8 to 3.4 swap were intended for the TBI Chevy Blazer, for which there apparently was some 4.3 setup, though that still sounds like too rich a fuel/air mixture.

My dad and I (we're doing this together) will go with your suggestion to use the stock 3.4 injectors, and have concocted a scheme, in case the computer is pulsing too lean, to correct air/fuel mixture-- We put a variable resistor on the O2 sensor, allowing us to, from within the car, dupe the computer into thinking that the car is running more rich or lean, and correct accordingly.

This would also allow me to, if I feel like a little extra power one day, turn up the resistance, make the computer think I'm running lean, and correct, which will make me run a little rich... When I'm done I can turn back to zero resistance. I figure we could put in some analog readout of the current actual fuel/air mixture to make sure we don't damage anything by accident.

Thanks again,
Dave

 

just use the injectors from the 3.4 Thats what I did and it works great. Also, try checking out the tech articles from the V-6 guys. Very good info there.

 

In theory it sounds like a good idea, but the o2 sends voltage not resistance to the ECM. You are not going to have any major gains by adjusting the o2, since the ECM will deliver enough fuel to keep as close to 14.7 AFR as possible.


Are you sure on those numbers for injectors? Stock 3.1 came with 17lb injectors, and the 2.8 MAF ECM will run fine with 19lb injectors with no problem (lots of guys do it when boosting).

 

I would install an adjustable fuel pressure regulator for a TPI car (yes, they work fine on the V6) if you need to make your car run a little richer...

 

Thanks again everyone for the replies.

It's very nice to know, 1989karr, that someone else, after this same swap got good results with the 3.4 injectors, that saves us about $300 in injectors.... And a whole lot of worry...

KrisW, AFAIK (and correct me if I'm wrong), the ECM measures the amount of O2 left in the exhaust (via the O2 sensor, of course) extrapolates a fuel/air mixture from that, and adjusts injector pulsewith accordingly. So, I don't see how raising fuel line pressure would cause a rich condition, the computer would simply correct for it, by shortening the pulsewidth.

firstfirebird, you're right, the ECM measures voltage, a voltage within 0.1-1V. I assumed that by sticking a variable, resistor in, I could scale up or down (well, not up... it's just a resistor...) the voltage, by changing the resistance.

The foolage, I believe, will allow the computer to believe it's mixing 14.7, when in fact, it's not. It's mixing what I want it to. Although it might be tricky to determine the true current A/F ratio. I don't know if they make analog voltmeters that fine.... Or how voltage corresponds to current A/F ratio....

Apparently a 12.1 A/F ratio is ideal for power, so if I could adjust between that, 14.7, and 15.4 (ideal for fuel economy), I'd be more than satisfied.

-Dave

 

lol yup. Saves a LOT of money....unfortunately for me, the injectors were bad as they were left to sit in the weather elements. But I figuered i might as well get new ones since i got the motor so cheap (that plus I had no other choice)

But if you got good ones all you have to do is change the O-rings, put them in and you're good to go! BTW, the 3.4 injectors will look a little different at the ends when compared to the 2.8 injectors but they work fine.

 

Well, apparently, according to Wikipedia, the O2 sensor on the Camaro is narrow band, so fine adjustments are quite worthless.... Oh, well.... So much for our clever O2 sensor adjusting scheme.......

 

The engine doesn't always run off of the O2 sensor. It has to go to closed loop mode for that. When you are accelerating or driving erratically, it doesn't do anything.

Try the difference driving it around with the O2 unplugged...