Just finished the TPI swap on my '90 Formula yesterday and I'm a bit concerned about the injectors. Mine came with a set of practically new 22# injectors. I had Angel at TPIParts.com make an adapter for the PROM to correct for these and to disable the AIR. After testing and tuning most of the day yesterday I removed the adapter which solved almost all the bugs. Now, with no adapter I'm wondering if these injectors are too much for the 305 and if I'll have problems if I don't swap to smaller ones. Here's a list of what's on the car and you guys in the know let me know if I should switch to 19#. I'm thinking if I do I'll use the Ford 19# versions.
Stock TPI with Holley airfoil
Holley AFPR set at 44psi (34psi with vacuum at idle)
22# GM injectors
Stock '91 305 TPI PROM
MSD ignition
Edelbrock headers
No cat
Flowmaster 3" exhaust
180 degree thermostat
Engine itself is stock internals 305 E code TBI, stock cam,heads,etc.

 

So there is no memcal adjustment for the 22lb injectors and everything is running fine, right? I think you will notice your gas mileage decreasing as the computer still thinks it's running 19lbs buuuuuuuuut, maybe with the extra richness the the o2 will tell the computer to lean it out a bit to acceptable levels?

In a nut shell, I wouldn't even worry about anything until you get a real tuned memcal or even a 350 memcal.

 

What I'm thinking of doing is putting the prom adapter back in now that the car is running good and seeing what happens. We sort of didn't follow the "try one thing at a time" rule to get it running properly so there's no way of knowing if pulling the adapter was what really fixed it, we also made timing and idle adjustments as well. Ran it some today and the exhaust doesn't smell rich and everything is as yesterday with smooth idle and all. The A/F ratio gauge was dancing back and forth from lean to rich as always so who knows. Maybe with the open exhaust that TPIs supposedly don't like they will compliment each other?

 

I don't know my man. I'm the type of guy that says if it runs good and smooth, leave it alone. I would try the adaptor and if it runs better, good. If not, you at least know the car ran fine on the stock tune.

 

So we should all leave our cars 100% factory stock?

If you're going to be driving it on the factory prom, at least lower the fuel pressure a few PSI, to give it a better chance of correcting. But, full throttle will not correct at all in the leaner direction.

 

Your computer will be unable to properly compensate fo eh 3psi difference.

Even a 2psi difference puts it on the ragged borderline of correctability with stock programming.

Do it right or leave the 19#'s in.

Most cases its not worth it to lower the psi to atting the proper corrections and it affects other parameters and Redngold noted.

Info and know how is easy to come by one the PROM board here if you wish to learn further.

later
Jeremy

 

People say you get what you paid for - in this case I'd ask, "did I?" is the new chip actually programmed for what you wanted?

I don't want to make any assumptions so can I ask which settings you had changed, and to what?

TPIParts states; This adapter will bypass the factory settings, and the ECM will run on the programmed settings instead. Please note that the factory prom must be mounted on the adapter for proper operation Actually the adapter bypasses the entire chip.
I run my Moates Adapter without the factory EPROM. I cut the EPROM section off of the MEMCAL carrier so I'd still have the Limp Home Mode.

 

The TPI came with the 22# injectors so there are no 19# to go back to. I'm going to try the adapter again to see if anything happens. We were working on 3-4 problems at once Saturday so I have no way of knowing if the adapter was the problem or part of a combination. The only changes I asked for were correct for the 22# injectors, disable AIR and remove the speed and rpm limiters.

 

It's probably not a priority right now, but in stop & go traffic the 180° thermostat won't help much because the fan is still programmed for the 195°.

 

I actually had 24lb injectors in my car. Mods are in my sig. I had to increase my idle to make the car idle better.

I DID lose miles/per/gallon
I didn't lose driveability.

I did this swap to make sure that I would not lean out the motor on nitrous.

I ran the stock prom for a 305

I did run stock fuel pressure,too.

 

I do have 24# LT1 injectors in my car, It runs great. Although I did have it on the dyno and had it tuned. All my mods are in my sig.

 

The thing I'm noticing from all you with 305s and larger injectors is that you also have cams, larger rockers,etc. whereas I don't. Mine's an internally stock 305 TBI and with the mileage as high as it is I'll keep it that way. Later a 350 will go in so the 22s would be necessary, but for now would I be better off leaving them in or putting 19s in their place? Gas mileage is not a major issue as this is not a daily driver, but driveability and performance are. Would the 22s hurt either?

 

I have played around with that stuff quite a bit. I ran my 305 tpi with the LS1 injectors fine. I was using megasquirt at the time. I just played with the fuel pressure and changed the constant, no problems.

I did however put in a pair of stock 19 lb/hr injectors in it later though to see if I could tell a difference. No felt or even noticed difference there. Yes, I datalogg. However the person originally told me that they were 22 lb/hr injectors, so I was running 19's on a 22 constant for a week, till I found out what they were from part numbers. The drivability with that was not as good, I had to crank feul pressure way up. There was no smoothness in the throttle either.

 

19lb with 46-50psi is best for this combo.

22lb is a little on the big side, but ok if your ignition system and airflow are adequate.

24lb on this motor is way too much.