To make a long story short, my tpi vette used to have a blower on it. When I got it, it was gone and I returned it to to a naturally aspirated setup. While my chip is out for reprogramming, Ive discovered the car has a few other mods, full roller rockers, adjustable FP regulator, big fuel pump maybe a 52mm TB, and 30lb injectors- possibly even a cam swap.

My question is, I want to run the car as close to stock as possible with what I have on hand. Is it possible to tune the prom properly to run the motor leaving the 30lb injectors in? I have everything back together, no stock injectors available and just want to run the motor to make sure its healthy before I get too far.

Can this be done? Can a decent tuner account for the larger injectors, Or should I start disassembling it all and put my projection setup on, or easier yet- just carb it. Thanks in advance.

 

Since you dont really know whats in it, I'd try it with the 30s. A simple datalog will go a long way in finding out what it needs.

 

Its a used car, I know the 30s will be on the large side for a N/A stock 5.7 but is there a chance it will run OK with them in there?

 

Its podddible. Speed density or MAF ?? You really need to run some datalogs and go from there.

 

Its converted to SD. I know what your saying about datalogging, but Im not even near that point yet, I just wanna get it to run half decent. Im not even sure the motors ok. Tuning later.

 

You're missing the point.

To get it to run decent, the tune has to be correct for the engine combination, one of the large parts of getting that to work is through datalogging, even if it just for starting.

To answer your original question, tuning for larger injectors is one of the easier things to do in most cases (IMO), since there are usually constants or basic tables available to adjust for this.

 

Thanks six shooter, I know what you are saying- but I think you are missing the point. I bought the car(cheap) only taking the POs word that the motor was ok. I just want to see if it runs without knocking or anything catastrophic. I have no reason not to believe him, as everything seems to done properly, but now that its back together 100%, Id like to try to start it. The memcal was rewrote for the blower, so its out to be recalibrated for stock. The tuner wants all the info I can give him.

I just wanted to know if it was do-able, and you did answer that it is. After I find out its OK, then we can perfect the tune. If not- Im making serious changes to the setup and that TPI is history.
Thanks.

 

Use a stock calibration as a starting point and just set the injector constant and injector offset to what they should be for your injectors. Turn the key, and see what happens. If its close to stock, and has a stock calibration updated with the info for your injectors, then you should be good to go. The PW at idle may be a little short, but it will probably still work good enough just to see what your dealing with. The worst that will happen is that it wont run well if it has a large cam. But, at part throttle, it should be good enough to at least make sure the engine works.

 

That's like saying "I'm starving but I'm not ready to eat yet."

 

Thanx Dimented24x7, we'll give that a go.
Kevin, I guess what I meant to say was we can attempt to datalog it IF it runs at all.

Thank you all for the help.

 

Yes, you can easily account for the larger injectors. All we do is bring BLM's as close to 0% O2 correction as possible, and the ECM handles the rest. The adjustable fuel pressure regulator will help you dial it in even further when you have a load behind the engine. Even with the supercharger formerly being equipped, idle characteristics should already be close in the chip, so have your tuner focus his or her attention mainly on part throttle, as well as wide open throttle. Good luck....

 

Thanks Street Lethal. Its all new to me, but Im willing to learn. I actually got a holley projection4, with the car, and since then scored a Haltech ecu for it if I actually want to start make changes away from the stock setup. Im willing to learn, but would just like to hear it at least idle, with the GM ecm, then I will go from there.

 

So, its relatively easy to adjust for the 30lb ers even on a near stock engine from what you are all saying. I just hope it runs. I should have the chip back this week...

 

It'll be fine. 30-lb injectors is maybe a tad more than 6% of fuel compared to stock, and believe it or not the ECM can almost correct for that much all on it's own, but it shouldn't have to. All the tuner is really doing is decreasing injector pulse width to get your air/fuel ratio back to where it needs to be throughout the RPM band. Meaning, he or she will pull 6% of fuel from the stock tune to compensate for the higher flowing injectors, but then they will have to take into account the possibility of an aftermarket camshaft, and will start increasing it again in incriments until the engine is happy. It will be trial and error because the cam specs are essentially unknown, but if a wideband is being used, it shouldn't take too long. We're looking for as close to 0% correction as possible when we tune....

 

Thank you guys.