Dyno shows lean condition

[Lee]

Put the 2-top on the dyno and it ran 213.52 hp with 261.61 max torque. The interesting thing about the run was air/fuel was flat at 15! Pretty lean, all across the range. I've ordered an adjustable fuel pressure regulator from MM and when I install it I'll add 4 lbs and strap it to the dyno again. Any thoughts? I wondered why it would get 28 mpg running 80 mph down the highway. Now I know why, it's sipping fuel.

 

[Doug]

that's odd. I'd have the chip checked out or the wideband on the dyno...

 

[Lee]

Good point. Maybe I should just pull the chip and try again.

 

[Lee]

Went ahead and installed MM's adjustable fuel pressure regulator and added four pound of additional fuel pressure. I'll try the dyno again sometime and see if this helped.

 

[93Cobra#2771]

Lee - Sounds like your chip was burnt a little lean for you. The fuel pressure might work as a temporary fix, but the EEC will write long term fuel corrections to make up for the additional fuel pressure, and it applies those corrections to both part throttle and WOT runs (otherwise known as the "adaptive process"). 93 and older models apply adaptive fuel trims at WOT but do not write them. 94 and newer models apply adaptive fuel trims at WOT, and will also write adaptive fuel trims at high load/Closed loop operation.

My ultimate suggestion would be for you to get your chip reburnt, as you are flirting with blown head gasket territory...

One other thing to check for is if the dyno wideband is properly calibrated. Easiest way to test that is for them to do a wideband reading on your car at idle. It should read ~14.7:1...

 

[SnakeBite98]

when was the last time you changed you fuel filter? i was lean and changed it and my curve changed big time. just a thought.

 

[Lee]

Good question. I've owned the 95 for a year and I've not replaced the fuel filter.