Air Fuel Ratio? 12.4 to 1 too rich?
12-21-2004, 08:37 AM
#1
Le Mans Master
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St. Jude Donor '03 & '05
Air Fuel Ratio? 12.4 to 1 too rich?
I have a 396 LT1 with 30# injectors, long tubes, Hot Cam (yes it is a little small for this motor)58mmT Body, MSD ignition. After getting it tuned, I had it dynoed, 400rwhp 428ft/lbs tq, but the fuel pressure had to be dropped to 36#'s(lowest I could get it before screw came out on F/P regulator) and the air fuel ratio on wideband was 12.4 to 1. Is there any power left if I get it recalibrated on the tune to where I can get the air fuel ratio leaner? or is this okay on a N/A motor, automatic etc?
ps 93 LT1 Speed Density motor
ps 93 LT1 Speed Density motor
12-21-2004, 09:49 AM
#4
Former Vendor
The 30# injectors are too large for your motor, which is why you had to have the pressure down so low to achieve a reasonable AF mixture. THe problems with droppping below 38psi are the injectors start not delivering the correct amount of fuel - they for a lack of better words, start to sputter the fuel, instead of atomizing it for a better more efficient mixture.
You are not alone - most people over inject their setups...which leaves them right where you are currently at.
Even my good flowing 434 is over injected with 30# injectors. 24-26# ers would have been a better choice for me, which would have allowed me to run 45-50 lbs pressure for a much better atomization of fuel.
Your tune can be programmed to allow for a higher pressure at WOT, but what your basically doing is turning the 30lb injectors into a smaller injector, so what most don't get is why not just get the smaller injector to begin with.
You are not alone - most people over inject their setups...which leaves them right where you are currently at.
Even my good flowing 434 is over injected with 30# injectors. 24-26# ers would have been a better choice for me, which would have allowed me to run 45-50 lbs pressure for a much better atomization of fuel.
Your tune can be programmed to allow for a higher pressure at WOT, but what your basically doing is turning the 30lb injectors into a smaller injector, so what most don't get is why not just get the smaller injector to begin with.
12-21-2004, 01:36 PM
#7
Former Vendor
Originally Posted by steve40th
Ski, Can I just install smaller injectors? Then raise the fuel pressure back up?
12-21-2004, 02:18 PM
#9
Race Director
Personally, I would just stick with the 30 lb injectors. I really doubt that the little if any gains you will see from the 24's would be worth the price of new injectors and a different tune.
12-21-2004, 02:24 PM
#10
Melting Slicks
Originally Posted by ski_dwn_it
The 30# injectors are too large for your motor, which is why you had to have the pressure down so low to achieve a reasonable AF mixture. THe problems with droppping below 38psi are the injectors start not delivering the correct amount of fuel - they for a lack of better words, start to sputter the fuel, instead of atomizing it for a better more efficient mixture.
You are not alone - most people over inject their setups...which leaves them right where you are currently at.
Even my good flowing 434 is over injected with 30# injectors. 24-26# ers would have been a better choice for me, which would have allowed me to run 45-50 lbs pressure for a much better atomization of fuel.
Your tune can be programmed to allow for a higher pressure at WOT, but what your basically doing is turning the 30lb injectors into a smaller injector, so what most don't get is why not just get the smaller injector to begin with.
You are not alone - most people over inject their setups...which leaves them right where you are currently at.
Even my good flowing 434 is over injected with 30# injectors. 24-26# ers would have been a better choice for me, which would have allowed me to run 45-50 lbs pressure for a much better atomization of fuel.
Your tune can be programmed to allow for a higher pressure at WOT, but what your basically doing is turning the 30lb injectors into a smaller injector, so what most don't get is why not just get the smaller injector to begin with.
Mike
12-21-2004, 02:29 PM
#11
Safety Car
What injector constants did the tuner try? I have 36# injectors and my tune was stupid lean at 50 PSI untill the tuner found a constant that matched up with my injectors and motor combo. I can asure you that 30# injectors on a LT1 396 are not to big and if properly tuned should alow you to run 41 PSI and be fine. Because of the wide opinions on injectors I decided it is best to use what ever injector your tuner is most comfortable with for your particular combo, in my case my tuner said he would like to see a 36-42# injector and I couldn't afford the FMS 42's (And did not feel I needed them) so I wen't with the 36's). In terms of the tuner I used I can only say that the twenty or so loacal people who used him all highly recomended him and that I gained 31 RWHP and perfect drivability, Zero cam surge, and a 900 RPM idle.
12-21-2004, 03:47 PM
#12
Le Mans Master
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St. Jude Donor '03 & '05
FD2BLK, who tuned your car in Charleston. I know Jamisons Custom Corvettes has PCM4LESS do it I believe, or More Performance? Other than jamisons, I dont know of any tuner in Charleston
Last edited by steve40th; 12-21-2004 at 04:04 PM.
12-21-2004, 05:24 PM
#15
Safety Car
Originally Posted by steve40th
FD2BLK, who tuned your car in Charleston. I know Jamisons Custom Corvettes has PCM4LESS do it I believe, or More Performance? Other than jamisons, I dont know of any tuner in Charleston
12-21-2004, 05:54 PM
#17
Safety Car
Originally Posted by steve40th
Thanks, When they dyno tuned your car, what software did CAM use to get data for tuning, ie Tuner cat, LT edit etc.?
