Ok, just wondering how many of you guys out there run quicker a little on the lean side? I always thought lean was mean! Basically on my car i run 24lb injectors, timing is set to the max just at the brink of detonation and my fuel pressure is as low as i could get it without stalling at idle. The car is zippier and much easier to drive this way around town and at part throttle. Not to mention, sooo much better on gas.However, i just replaced my muffler with a much better flowing one and sometimes the car feels lean now, feels like it is going to blow up sometimes.LOL Has anyone experienced their car feeling lean from an exhaust leak too? Just wondering.Anyway, just wondering who thinks richer may be better? I really don't want to move my fuel pressure setting cause it such a pain to get right.

 

Sounds like you need to do some tuning (prom burning). Around town, for best economy, tuning the ECM and closed loop calibration to give around 14.7-15:1 will usually give teh best fuel economy. At WOT, 12.5-13:1 gives the best power. If your using your stock 91 TPI ECM, than that goes a long way to explaining why you need to mess with the fuel pressure to get it to run better. A better way to do it, is to recalibrate the ECM with the correct VE and timing tables for your engine. That will get the same results without risking cracking a piston, or blowing a head gasket from going into detonation all the time.

 

You are saying that too low of fuel pressure can cause detenation too? So, basically,if i raise my pressure up,i may be able to run more timing?

 

UPDATE** I just went outside and kicked the pressure uo from 42.75 to right about 43.75 lbs. Hard to tell cause its wet out, but it feels like i gained a lot more midrange/upper end power and gave up some low end torque. I have not adjusted pressure in over a year,but this year i have added headers, muffler,throttle body by-pass. Maybe the mods needed a little more fuel?

 

The chemistry side of it is that you want all of the oxygen to be consumed. It's less of a drain on power to have a little excess fuel than not to have enough. The point where too much fuel begins to rob power is where the excess liquid fuel prevents the effective production of heat. Heat is power.

At the other end of the spectrum, where you are not providing sufficient fuel to consume all the oxygen in the cylinder, the remaining oxygen combines with the nitrogen produced by the combustion event and creates oxides of nitrgen(NOX), a harmful pollutant gas. The lack of liquid fuel added to the cylinder also causes excessive combustion temperatures which can cause severe damage.

I run 24 lb/hr injectors at 70psi. This is not a widely accepted method for fueling a high performance engine but it has infact been proven many times to work quite well. The higher pressure produces improved atomization, creating more effective combustion. I find that my power level suffers if pressure drops to 60psi. My wide band O2 sensor reads 12.5-13:1 AFR at full throttle when the engine is running it's best.

 

Do you think that the car just felt faster lean? it actually feels like a bigger engine now,but it is not zippy down low anymore.LOL What do you think?

 

dimented mentioned PROM tuning. It sounds like you have some work to do on your base fuel map. The higher pressure is correcting for a lean area in the BFM at higher engine speeds. At the same time it's over fueling at lower revs. Follow dimented's advice and address your tuning.

 

Not really sure if i am running rich or lean at this point. Remember , i have 24lb injectors instead of the stock 22 lbers. I then lowered my fuel pressure from the 45 i had originally down to 42.5 That seems like the sweet spot. Not too lean though. So, do you think i am still running rich ,seeing as i have 24 lb injectors in there? even with the fuel pressure backed off a few lbs?

 

The easiest way for you to check AFR is with a wideband O2 and AFR gauge. Otherwise you can learn to read plugs. The performance of your car is a good indicator of what it needs. If it runs better with more fuel pressure, then it was running lean. The opposite is also true.

I dont know what your mods are. If the engine is stock, there is no reason for it to have larger than stock injectors.