I went from a 3.7 pulley on my procharger to a 3.4 with a FMIC. I have only been cruising around with it, no WOT blasts, and I pulled my plugs today and they were white as the day I put them in. I always understood that you want your plugs tan in color and maybe a little darker considering FI engines are usually run rich. I was curious if it was normal to have this much of a change in A/F from the mods I did. I had the car dyno tuned with the 3.7 pulley and the twins so Im sure the a/f was okay before hand. Am I increasing the incoming air that much? My fuel pressure is 50 psi at static. Should I bump it up to 55 or 60 until I can get it retuned?? Thanks

 

wicked_95z,

A pulley and intercooler change should not affect anything when 'cruising around'. Your bypass (assuming you run one) is purging all of the time when the motor is not loaded so you are not increasing incoming air here. Are you sure your plug reading is acurate in measuring before and after results? What did your plugs look like before the pulley/cooler change? I guess what I'm getting at is that you may have assumed your tune was OK before the change.

-Scott.

 

Well, its kind of hard to tell because my methanol was coming on way to early, i.e. under vaccum, so it was running rich all the time. I am assuming since I sent the tuner datamaster files and he was making changes to the tune that everything was good.

 

reading plugs really only works right after you run em WOT because you run alot more lean cruising around at at idle.

 

I dont understand why it still wouldnt work at cruise. Can you explain? I understand you run more lean and I would like to richen up the cruise. Ive already lost one motor from running lean and Ive got a whole lot more money in this one.

 

If you are in closed loop and your O2 sensors are working and you are within the adjustment range of the computer, you are not lean. If you want to run at richer than 14.7, you will have to run open loop. You probably didn't ruin your last motor from cruising around lean, maybe from WOT lean or too hot of a plug or too hot of an intake charge or too advanced timing causing detonation.

Trying to read plugs on a modern car that runs unleaded to determine if you are a litlte lean is tough. The fuels all stain the plus differently due to the additives. If you have a leaky valve guide causing an obvious oil control problem or other gross problem, then you can get some data from the plugs, or if you need to look for signs of detonation or fouling from too cold plugs.

 

Thank you for explaining that for me. There is no way to tune richer than a 14.7 in closed loop??

 

It might be possible to do if you ran speed density or enabled enrichment at real low TPS, but I've never tried it. Maybe someone else will know. Otherwise, it is hardcoded and the computer will keep trying to correct to that value. Also, you could get an aftermarket ECU and then do what you wanted with the tune.

 

Why would you want to run richer than 14.7 in closed loop? AFAIK there would be no reason to.

Rich

 

I don't know Rich, but if he was in boost at a smaller throttle position where he wasn't in enrichment, would he need more fuel? I guess he could always try moving the TPS to WOT lower at a lower RPM or something. I'm just wondering about intermediate throttle positions fueling.

 

OK, I see what you mean. I was thinking about very light load. Mine is tuned to go into PE mode pretty early exactly for that reason. But for cruising, light load it seems fine in closed loop.

Rich

 

How early rich? I may even end up having similar issues.