Crossfire Injectors - Different Flows
#1
Crossfire Injectors - Different Flows
1982 Corvette with the crossfire injection running off '7747 w/ Prominator Pro. I have made several modifications to the car including SY-1 intake, 2" throttle bodies, 228x228 roller cam w/ 1.6 ratio roller rockers, auto to manual conversion, sidepipes etc. Been reading and studying posts for about a year now trying to get ecm tuned - making slow progress. I am currently stumped and can't seem to find a post addressing this problem - maybe I'm searching for the wrong thing. Anyway, the front injector flows noticably more fuel than the rear injector. I have checked fuel pressure and the compensator and it seems to be working (not stuck). Even changed the injector. Any thoughts on what would cause front injector to dump fuel - causing the left bank of cylinders to run nasty rich?
Thanks in advance!
Gene
Thanks in advance!
Gene
#2
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Re: Crossfire Injectors - Different Flows
The injector flows are staggered from the factory. This was done due to the accumulator/FPR set up. Best thing to do is to parallel plumb the TBI units, block off the accumulator and AFR, and run an external FPR.
Then use two of the same injectors.
The injector connector on the rear TBI unit may be intermittent.
RBob.
Then use two of the same injectors.
The injector connector on the rear TBI unit may be intermittent.
RBob.
#3
Re: Crossfire Injectors - Different Flows
The injector flows are staggered from the factory. This was done due to the accumulator/FPR set up. Best thing to do is to parallel plumb the TBI units, block off the accumulator and AFR, and run an external FPR.
Then use two of the same injectors.
The injector connector on the rear TBI unit may be intermittent.
RBob.
Then use two of the same injectors.
The injector connector on the rear TBI unit may be intermittent.
RBob.
#5
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Re: Crossfire Injectors - Different Flows
Why not? The ECM doesn't care what the mechanicals are. There would be some tuning needed to make sure that fueling under different loads is correct.
If you're getting so much more fuel from one injector over the other that you have overfueling issues on one bank, there's a problem that needs to be fixed. Even if GM staggered the injector sizing (which is something I have not come across) they wouldn't be so drastically different that you could see the difference, let alone have actual fuel delivery issues.
The only time I've seen that so far with a Crossfire system is when the injector pods were reversed, so that the FPR was first inline. This also caused a no start condition, since the crossfire system was all stock sizing, and didn't deliver enough fuel to light the engine. I could see with larger than stock injectors that and engine could start even with the injector pods reversed.
If you're getting so much more fuel from one injector over the other that you have overfueling issues on one bank, there's a problem that needs to be fixed. Even if GM staggered the injector sizing (which is something I have not come across) they wouldn't be so drastically different that you could see the difference, let alone have actual fuel delivery issues.
The only time I've seen that so far with a Crossfire system is when the injector pods were reversed, so that the FPR was first inline. This also caused a no start condition, since the crossfire system was all stock sizing, and didn't deliver enough fuel to light the engine. I could see with larger than stock injectors that and engine could start even with the injector pods reversed.
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Re: Crossfire Injectors - Different Flows
It's far too much of a blanket statement saying that "it won't work", when it can work, with proper tuning and proper reasons (mechanicals) why it is used.
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Re: Crossfire Injectors - Different Flows
I used a Marine TBI regulator with vacuum reference years ago on a 230/230 roller cammed 305 vortec. Ran just fine with a VAFPR and 7747. It actually HELPS the limited VE table range by allowing a WOT fuel increase. With that much cam the restriction that needed to be added was in the MAP sensor vacuum line. The 7747 did not appreciate the erractic vacuum signal. What I used was a TCC delay valve from an earlier application. It slows the vacuum signal one direction, but has a check valve that allows a freer flow the other direction.
I ran a 350 TBI with a 204/214 cam and 081 TPI 305 heads on it as well with the marine regulator and a stock 350 chip for quite some time. 255 RWHP at the time and was running the STOCK 350 chip. Had the timing set at about 8-10*BTDC as well.
I ran a 350 TBI with a 204/214 cam and 081 TPI 305 heads on it as well with the marine regulator and a stock 350 chip for quite some time. 255 RWHP at the time and was running the STOCK 350 chip. Had the timing set at about 8-10*BTDC as well.
Last edited by Fast355; 08-04-2014 at 11:33 AM.
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Re: Crossfire Injectors - Different Flows
Fair enough, a VRFPR shouldn't be used with a '7747 ECM. It can work, but there are a lot of things that can be done that shouldn't be.
RBob.
RBob.
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Re: Crossfire Injectors - Different Flows
I agree with you on that. I have used both the 7747 and 7427 with boost, using a vacuum check valve to vent boost pressure above atmospheric away from the MAP and a FMU to increase fuel pressure at WOT. Used a split second auxiliary injector controller to add fuel via two additional 80 lb/hr injectors and a MSD 6BTM box to retard timing with boost. It sounds like alot, but it all worked fairly seamlessly when combined and properly dialed in.
#13
Re: Crossfire Injectors - Different Flows
As usual, the folks on thirdgen provide more that expected and I thank you for that. I may need to back up and reconsider the way ahead.
I'm going to list my mods to solicit advice to move forward;
'91 fuel pump
228x228 roller cam
Edelbrock Smokey Yunick cross flow intake with custom lid to accomodate a Crossfire Injection
2" throttle bodies
4sp manual trans
200cc Dart Pro1 aluminum heads
I would really like to get the car tuned and start enjoying it. Would you recommend a modern ecm and parallel plumbed injectors?
Thanks,
Gene
I'm going to list my mods to solicit advice to move forward;
'91 fuel pump
228x228 roller cam
Edelbrock Smokey Yunick cross flow intake with custom lid to accomodate a Crossfire Injection
2" throttle bodies
4sp manual trans
200cc Dart Pro1 aluminum heads
I would really like to get the car tuned and start enjoying it. Would you recommend a modern ecm and parallel plumbed injectors?
Thanks,
Gene
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