Hmm.. strange problem.
Keep in mind my car has an N/A control system... (with S-AFC)
Ever since my engine got ported, my check engine light will OCCASIONALLY (only cold weather, cold engine) go on while accelerating- found out it was the pressure sensor.
Well it hasn't done it since I put the turbo on, but now it's back.
Ever since I relocated my AFM to AFTER the turbo (right at the intake elbow) it does it, but ONLY under boost.

Whenever boost hits 2-3 psi, the light goes on, and power definately goes down.
It's strange, because doesn't the N/A pressure sensor supposed to have the same value under pressure as it does at atm. pressure?? I thought it only measured vacuum??

Any ideas??

I could always just disconnect the press. sensor hose, might loos mileage though- I could just tune down the LO throttle map....

 

The ECU might be throwing a code because the sensor is reaching the maximum pressure it can read. Given that it wouldn't normally be reading pressures as high as it is now, the ECU might be interpreting the readings as a faulty sensor. Just a guess.

 

the na pressure sensor tops out at 1 psig i think... u need a TII pressure sensor off a s5 car.

 

I'm assuming that would conpletely through the calibration off- since it returns 0-5v or so from 30 inHg or ss to about 15psi... while the NA one return 0-5v from 30inHg to 0psi... different scale.

BTW- Another factor in the pressure sensor curiosity debate- I don't see a change in AF ratio at all when the light goes on- but a definate (LARGE) loss of power.
I guess it pretty much only controls timing!


BTW- Maybe I'll try applying pressure to the sensor, and seeing if the output voltage changes, not just only under vacuum. I think i tried that one time though.
Frustrating.

 

Umm no, the N/A pressure sensor (at least my S4 one) topped out well above 1psi, much closer to 4 psi actually..
wether or not it was still retarding the timming at that level I have no idea, I guess it was.

 

Well, I don't think it really fixes the problem, but you could install a check valve so the sensor only sees vacuum...We may have just found the major limitation of the S5 ECU...

 

I've never had a problem with it before- (execpt occasionally when N/A and it was cold out- strange) only when I moved the AFM past the turbo.
My guess is now that the AFM is reading less air volume under boost compared with BEFORE the turbo, the ECU is seeing a strange relationship between the pressure sensor and the AFM, and throwing a code because it's confused....

I'm serisouly considering trying to get an S5 TII ECU and wiring harness....it would be so much better to be able to tune timing for boost!

Oh, and how could I install a check valve? That would lock vacuum in the line between the valve and the sensor...

 

Your right...Check valve wouldn't work.

Just to add something...If you are really considering getting the S5 ECU (and thus the related sensors) you might want to think hard about getting a full EMS system (ie. Microtech).

It took me all of 3 seconds to make the decision after I saw the Microtech LT8.