I have a 383(AFR 190's, superram, 36lb injectors, blower grind cam:220@50in, 224@50ex, 114lsa, 500lift in, 510lift ex) that used to have a paxton supercharger. I want to convert to a serpentine and run an ATI. I removed the blower and now anymore than 2/3's throttle the car bogs. It is in a 1987 trans am GTA. I am running a stock computer. Why would remove the blower cause this to happen? Can I tune it so that I can have some fun again? One person told me that the cam could be the cause since it is designed for a blower. This doesn't make any sense to me. I'm not getting any codes and the car seems to be running fine otherwise. What should I do?

 

I doubt it is related to the camshaft.
A guess would be this:
You said you are running 36 lb/hr injecters. You also said you are running a stock computer (I assume the 165 ECM). I don't know what Prom (custom or stock) you are using.
If the car was running correctly with the supercharger and you haven't recalibrated it (new prom), since removing the supercharger, It is probably running way too rich on the top end now, at least when in power enrichment mode or open loop mode.

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Tracy /AKA IROCKZ4me

• 355 cid
• AFR heads
• Arizona Speed & Marine hydraulic roller cam w/ AFR hydra-rev kit
• modified SLP runners
• TRW forged pistons/ceramic coated
• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
• Paxton supercharger
• Nitrous Express nitrous oxide

My IROC-Z
EFI Performance Club on Yahoo

[This message has been edited by IROCKZ4me (edited December 29, 2000).]

 

Are you saying just to reset the computer and the car should run right? I didn't think the computer would compensate that much for the blower.
-Matt

 

put back some smaller injectors and you should be fine. the car is bogging because of all the fuel that the 36lb injectors are supplying for a lot less airflow(no blower)so the smaller injectors should make the car much better. not perfect, but much better with the less fuel. also since you are all motor now, bump your timing a little that will help too

 

"resetting" the ECM won't help you here! You will need a custom prom for the bigger injecters, or you will need to install smaller injecters. You aren't flowing anywhere near as much air as you were, but you still have the same injecter flow and calibration as when the supercharger was on the car. I don't know that the air/fuel ratio was actually correct with the SC on, but it was closer if it didn't bog. Now that you have less airflow and you still are flowing the same amount of fuel it is probably way to rich to the point of bogging.
Air/fuel ratio tuning is in order here.
If you are going to put the ATI on soon you might want to just not drive the car at WOT until you get the install done. If it will be a while then a custom prom for 36 lbs/hr injecters will be easier than swapping injecters. If you have stock sized injecters laying around, swapping them in will be cheeper but more work.


PS if you would like more detailed information as to why the air/fuel ratio is so much richer without the supercharger let me know and I will explain it in detail.

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Tracy /AKA IROCKZ4me

• 355 cid
• AFR heads
• Arizona Speed & Marine hydraulic roller cam w/ AFR hydra-rev kit
• modified SLP runners
• TRW forged pistons/ceramic coated
• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
• Paxton supercharger
• Nitrous Express nitrous oxide

My IROC-Z
EFI Performance Club on Yahoo




[This message has been edited by IROCKZ4me (edited December 30, 2000).]

 

Can I just turn down the fuel pressure and bump up the timing? What's weird is that the blower only saw like 3-4psi. I really didn't think that it was going to make that big of a difference.
-Matt

 

It was maybe only 3-4 PSI but on a deep breathing 383 with aftermarket heads, cam, and intake, that is a good bit more airflow. Boost (PSI) is just backpressure. The more air the engine inhails, the less backpressure.
If it is bogging you won't have enough adjustment with fuel pressure to get it clean. A guy I know tried that once on a build with a stock ECM & prom and 30 lbs/hr injecters. To get the mixture close enough just to run without stumbling/bogging at WOT he had to run 20 PSI fuel pressure. His engine was hard to start when cold & ran like crap until it warmed up. It was lean at part throttle tip in, especially before it went into closed loop & backfired through the intake. His milage took a dive because of poor atomization. All part throttle drivabillity suffered. The idle wandered. The worst is it was still too rich at WOT! It was a mess.
The fix is one of three things.

• Increase airflow to match the fuel flow.
• Decrease fuel flow by installing stock or near stock size injectors.
• Decrease fuel flow by decreaseng injector pulse width with a custom PROM.

------------------

Tracy /AKA IROCKZ4me

• 355 cid
• AFR heads
• Arizona Speed & Marine hydraulic roller cam w/ AFR hydra-rev kit
• modified SLP runners
• TRW forged pistons/ceramic coated
• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
• Paxton supercharger
• Nitrous Express nitrous oxide

My IROC-Z
EFI Performance Club on Yahoo

 

Well I am installing the other blower once I can afford it. May be 2 months. I guess that it really shouldn't hurt anything except my pride in saying I have a 383 that can't even beat a stock 5.0.
-Matt