Tuning question
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Race Director
Joined: Oct 2000
Posts: 16,477
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Tuning question
Background: I have an adjustable fuel pressure regulator, 24 lb injectors, ported plenum, polished intake, long tube headers and a single cat in the exhaust, and a fairly large cam. I'm running 47 psi of fuel pressure.
My air/fuel guage is showing the car running slightly rich while idling and normal cruising. when I am cruising at 75 it is on the first bar of stoich, sometime showing a little lean. This is perfect I think, giving me the best fuel economy.
However, going up hills it pegs on the lowest bar of lean, I'm not sure what the bars equate to, but judging from everything else, I'd say I'm at about 16-17:1 Air/Fuel.
I really need to get a chip burned for it, but I am short on cash since tourism has really dropped off since September.
My question, is should I adjust the fuel pressure to be stoich(close to 14.7) around town and let the ratio be around 16:1 cruising on the highway, or should I adjust and run rich around town and closer to 14.7 on the highway?
I think going up hills isn't going to be fixed until I get a chip. :( I need to get an exhaust temperature guage to make sure I'm not doing irrepairable damage when its that lean.
Thanks for any feedback.
My air/fuel guage is showing the car running slightly rich while idling and normal cruising. when I am cruising at 75 it is on the first bar of stoich, sometime showing a little lean. This is perfect I think, giving me the best fuel economy.
However, going up hills it pegs on the lowest bar of lean, I'm not sure what the bars equate to, but judging from everything else, I'd say I'm at about 16-17:1 Air/Fuel.
I really need to get a chip burned for it, but I am short on cash since tourism has really dropped off since September.
My question, is should I adjust the fuel pressure to be stoich(close to 14.7) around town and let the ratio be around 16:1 cruising on the highway, or should I adjust and run rich around town and closer to 14.7 on the highway?
I think going up hills isn't going to be fixed until I get a chip. :( I need to get an exhaust temperature guage to make sure I'm not doing irrepairable damage when its that lean.
Thanks for any feedback.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Tuning question (NoWorries)
At part throttle in closed loop mode the ECM & O2 sensor should keep things at/near stoch.
You might want to put a scanner onto it to see what the BLM cell values. Unless the injector pulse width is at max, things should be ok. However, a vacuum leak in the intake or in front of the O2 sensor could fool the ECM into running too lean.
You might want to put a scanner onto it to see what the BLM cell values. Unless the injector pulse width is at max, things should be ok. However, a vacuum leak in the intake or in front of the O2 sensor could fool the ECM into running too lean.
