badass99ss

iTrader: (17)

Had my car street tuned not to long ago and in the process we were seeing some crazy A/F ratios on part throttle. They were bouncing everywhere, from 11-16. We tried 2 A/F gauges and they both were giving us the same info. We tried turning the MAF on it's side and that made a big difference. I posted this in here cause im runing a Procharger now, and the MAF worked perfect with the stock set-up. Do you think my MAF is going out or do I need to reposition it else where? I tried moving it away from the TB and it seemed to help. I'm thinking that it is getting a bad reading from the turbulent/tumbling air between the procharger plenum and TB. Any suggestions would be appreciated.

Thanks
Troy

EPP

iTrader: (22)

We never have this trouble Troy. Does the guy who is tuning your car have experience with forced induction? What is the fuel pressure staying at? Bob

Slowhawk

iTrader: (12)

Sounds like your MAF is missing the screen. The screen helps a ton at smoothing the air flow for a FI car.

badass99ss

iTrader: (17)

The guy that did the tune is a sponsor on hear (Vince @ Trifecta Performance). The MAF still has the screen in it, I have done no mods to the MAF at all. I have sprayed the MAF with some electrical cleaner and thats it. My fuel pressure is at a rock steady 58-60. Every time I move the MAF it gets better or worse.

Troy

EPP

iTrader: (22)

What is the fuel pressure at wide open throttle? It will normally drop down to around 54 psi at wot on an oem style system with a good pump. Bob

VinceTrifecta

Hi all, I went out and tuned this car hands on about a week ago. We saw this strange behavior where the car would go super lean when the MAF frequency was in a certain range (usually during cruise). At high throttle or idle it would straighten out.

We rotated the MAF 90 degrees clockwise (if you're standing at the front of the car) and this resolved this "lean spot" in the MAF frequency range. The fuel mixture came in a bit rich vs commanded, but it was within a 2% or so.

At the time I was there the MAF and the TB weren't quite lined up. And the MAF was relatively close to the TB (compared to stock). Since then, badass99ss replaced the bellows between the MAF and the TB with a smoothed unit (it had the stock unit on it when I was out there).

He relocated the MAF further away from the TB and rotated it back to where we had it before and the problem was much less severe.

One of the first questions I had was whether the MAF was clean and had a screen, all is well there.

Badass99ss - if you are happy with your intake setup, and don't plan on changing it any further, we should schedule another tuning session and 1) Prove the MAF response is consistent, and 2) If it is, tune your MAF table for any unusual air flow characteristics. Sometimes this needs to be done on forced induction applications. We just did a turbo'd 2.4L Cobalt on the dyno last week and we saw similar behavior (fluctuations in commanded vs actual AFR in certain ranges in the MAF table).

white01ss

iTrader: (37)

My MAF has caused me nothing but grief while trying to get the trims in line. It was reading 5% too much air at 30 kPa or less, and 20-50% under at 35 kPa and greater. This is a stock, screened MAF and stock MAF table. It seems that a centri blower is just moving too much air around for the MAF to measure accurately. The bypass valve bleeds off most pressure while at idle/cruise, but there will still be some pressure build-up and release.

As soon as I disabled the MAF, my LTFT fell below 0 above 35kPa for the first since the blower was on. Right now, I'm looking for piece of pipe to put in it's place...

ZDOG

iTrader: (13)

would a larger bypass or vent to atmoshere setup help this?

VinceTrifecta

This sounds similar to what we saw - there was a discrete range in the MAF table where it would read 20% too low - above idle, usually during cruise. By rotating the MAF, the symptom was alleviated.

d1ws6

Hi Im new to this forum ,Im having a similar issue with my setup.I have an 02 ta with a
D1 kit and twin highflows. I have a stock MAF and ported stock TB. ECS blower cam and about 9 LBS boost. Car hesitates at very light throttle .But very strong WOT. If you give a few revs or feather the peddle it wants to slall after letting up. Is it possible that the MAF is too close to the TB?

VinceTrifecta

Could be a MAF issue. Even after we resolved the MAF issue by rotating it, we still had a hesitation issue at light throttle. We narrowed it down to cam surge, and resolved it by enabing lean cruise in the surge RPM zone (which forces open loop).

d1ws6

I rotated the MAF 90 and the drivablity improved greatly. I still have the issue with it accasionally stalling after feathering the peddle lightly. Just curiose , what did you do with the connection of the MAF since it sits tight against the radiator hose. I wrapped the sharp edges with rubber from a hose .Did you do something different? If so ,any pics.

PS havent tried the lean cruise in the surge RPM zone yet looking to see what that does for me.


Thanks again

badass99ss

iTrader: (17)

Mine also still had the stall when feathered even after I rotated the MAF. Vince tuned it out, hopefully he will jump in and help. I cant recall what he did. As far as the MAF plug go's, mine does not come in contact with anything.


Troy

d1ws6

Thanks for the pic . Mine is sandwiched between the a/c line and coolant hose .I wrapped the maf's plastic with rubber from a hose so it wont wear a hole in the coolant hose.


Thanks again for the quick response.

hymey

Have you modified the stock MAF tables vince?

Is there some type of airflow reversion going on?

Does the car still retain a 75mm MAF and if so, would changing to and 85mm MAF help at all?

cheers

hymey

VinceTrifecta

I suspect that was what was happening (airflow reversion or some other type of turbulence). There was a certain frequency range in the MAF calibration table where the LTFTs showed it super lean. Either side of it was within 5%. After we rotated the MAF, this behavior totally went away.

d1ws6

Doug from ECS recommended I put a stock unmodified tb in since I had a ported stock one in from Lingenfelter and that caused my throttle response to be very inconsistent and it had a dead spot . After I replaced it the car runs alot better with the hesitation almost gone. I also turned the idle screw up alittle to keep it from stalling after gassing it.

badass99ss

iTrader: (17)

Good to hear! Enjoy the

Troy