Question for those of you who are turbo'd and have the maf on the pressurized side of the intake AND you have a narrowband a/f gauge.

I originally had the maf on the non pressurized side and had a ghetto rigged BOV recirc port. In an attempt to clean the engine bay up and give myself more options for pipe routing and bov options i put the maf on the pressurized side.

THe car is running fine, boosting strong, and i have no problems with the narrowband a/f guage any time at boost or cruising. Cruising it swings back and forth to 2 or 3 bars into rich, and boosting at wot i'm getting close to pegged rich due to the fmu. However, since i've put the maf on the pressurized side i'm getting a spot in the rpm band where it reads close to full lean. Its not in boost, about 30-40% throttle once the car swings into closed loop mode. It sits on that lean. I dont hear any pinging or anything, and i know a narrowband is useless for accurate AFRs, but dead lean scares me.

Its not in boost or anything, as soon as the boost hits the fmu turns on and i'm running nice and rich. I'm going to drive the rest of the week out and then pull my plugs and see what they look like. My wideband should be on the way soon so that will be another nice indicator but in the meantime i just wanted to see if anyone with the same setup got the same thing.

 

Anyone?

 

Had a thought. I'm using the stock evo blow off valve. It doesnt seat fully at idle and low throttle. Could the computer be learning the curves, subtracting fuel because it sees rich since some of the air is escaping at partial throttle and then when the bov finally seats shut its running too lean because it cut some fuel? I'm going to upgrade to an adjustable greddy knockoff to see if that solves some problems. Set it a little on the hard side so it seats at idle and partial throttle, but not hard enough that it wont open enough during shifts. We shall see. Ps i'm also getting a little minor stumbling at partial throttle, which might be related....

 

I used to have a narrowband air/fuel gauge in my turbo crx. I gotta tell you that thing was nothing more than a damn light show in my dash. It would give me readings all over the place. The car was professionally tuned and when hooked up to a wideband would never show anything out of the ordinary. But my a/f gauge would frequently say that I was running too lean or rich (that was also professionally installed by the shop that did the tuning). And I've also had friends who have experienced the same thing with their a/f gauges. So I wouldn't jump to any conclusions about your car's tuning until you get readings with a true wideband.

Also, in reference to the Greddy "knock-off" BOV you were talking about getting. I would not recommend it. I've heard a lot of stories from people who bought cheapo BOV's that had problems. They might work ok at first, but they aren't built to last and will fail rather quickly. You definitely don't want your BOV to stay shut and get compressor surge. Nor do you want it to leak and cause boosting/tuning issues. You've spent the extra $$ on a turbo, why not shed the extra few bucks to help protect that investment. Besides, you'll just end up replacing your knock-off in a month or so anyway, so you might as well save yourself the hassle and just go with a good brand from the beginning.

 

Good call on the worthless narrowbandness. I already ordered my wideband so it should be here soon. I took a long drive yesterday in the blistering heat and i pushed the car a little bit keeping it in the lean zone on the narrowband a little longer. Pulled the plugs last night and they looked fine. Looked like they were brand new out of the box with the exception of minor whiteness on the top of the plug, but no where near the whiteness you get when under a really lean condition.

I'm only getting the knockoff to use for a week or two to test out whether thats causing some problems or not. I just needed an adjustable BOV to seal it a little more at lower throttle. I have the air flow sensor pot bov before TB so it really should not be creating problems since the air count is taken after the bov, but i'm just going down the list of "what ifs" right here, hence why i'm only dropping 20 bucks on a BOV instead of 180 only to find out that wasnt the issue.

 

Got my wideband in today. Unfortunately the lean condition isnt just the narrowband being wrong, i am running really lean at 25-50% throttle. For a short amount of time it will dip down to 16 afr's and then sometimes it will pop back up to 14.7-15. Anything over 50% throttle and i'm running solid 12's afr throughout the entire powerband under boost.

I'm relocating the Maf to the intake side tomorrow. I'm just waiting for my jb welded recirc port to dry overnight before i paint it and put it on the car. Hopefully that will fix my lean issues and the car will be happy.

 

my narrow band reads that also and im with maf on pressure side to

 

Well next problem. I relocated the MAF to the intake side this morning after letting my PVC 1.25" fitting jbwelded into a piece of 2.25 metal pipe sit overnight and it ran perfect. No more lean spots, car ran strong, sounded good...........Until i went outside after letting the car cool down and the JB weld had cracked and came loose from the metal pipe. So now i'm recirc-fittingless. Any ideas how to make a recirculation port on a piece of pipe that will actually hold, short of having a piece welded on. Because if no one has any sure fire easy to make ideas i'm bringing it to a welder tomorrow and having them weld a piece of 1.25 pipe onto the top of the intake pipe.

 

Mods may want to make this a sticky for all the people building custom turbo kits. I'm ending this thread on this note because the problem has been fixed.....

PUTTING YOUR MAF ON THE PRESSURIZED SIDE OF YOUR INTACT TRACT DOES NOT WORK. IT WORKS ENOUGH TO KEEP YOUR CAR DRIVEABLE, BUT YOUR CAR WILL RUN SIGNIFICANTLY LEANER ON THE STOCK ECU MAPS UP TO HIGH THROTTLE OPEN LOOP MODE. EVERYTHING FROM 0 TO AROUND 50% THROTTLE WILL RUN IN THE 15-17:1 AFR DUE TO THE FACT THAT ONCE THE TURBO STARTS SPOOLING THE KARMAN VORTEX MASS AIR SYSTEM CANNOT ACCURATELY READ THE AIR SINCE IT IS PRESSURIZED AND NOT FLOWING IN A STRAIGHT THROUGH DESIGN ANYMORE. THE ECU WILL UNDERCOUNT THE AIR COMING THROUGH. IT IS FINE FOR OPEN LOOP FULL THROTTLE BECAUSE THE ECU JUST DUMPS FUEL IN ANYWAY, BUT FOR CRUISING YOU WILL BE RUNNING LEAN. YOU CAN DO IT WITH AN EMANAGE OR STANDALONE TO COMPENSATE WITH MORE FUEL BUT AT THAT POINT YOU MIGHT AS WELL CONVERT TO MAP OR NO MAF AT ALL. CHEERS!

 

damn man nice im about to the same