B94Cast

Situation:
ECU off by approx 3PSI on what it reads - @ roughly 3PSI, ECU finally sees boost

Measurements:
3 Different boost gauges
AFC (afc coincides with ECU readings)
Feel - can feel the boost (when it is not bouncing into lean section)
Sound - can hear the turbo spooling, and hear the white noise of gobs of air flowing into the turbo

Symptoms:
A/F gauge still sweeping under partial throttle while in boost
Sweeps go into lean region while in boost
Lost power
Danger to engine?
Only happens when boosting at partial throttle, less than roughly 40%


Corrective actions attempted:
Rewrote multiple Uberdata images (results same)
Wrote to different chips (results same)
Compared data on chips to .bin - data is 100% valid
Purchased additional P75ECU - Chipped it (results same)
Replaced map sensor with another one (results same)
Changed settings in AFC into -% and +% on correction% (results same)
Restored system back to FMU and Aquarium parts (back to normal - no sweep under boost)

Verified:
No vacuum - boost leaks that I can find (even if they did exist, why does map report different values from gauges?)
Over roughly 40% throttle - no longer sweeps
Occasionaly, after a shift, even at better than 40%, will sweep while in boost
When sweep occurs (what prompts to look at A/F gauge) the power drops substantially

I have exhausted what I know to check. I am very concerned with seeing red while I am in boost, and do not want to damage engine. I would like to correct this somehow, even if it meens that I modify the voltage/resistance from the MAP sensor. But it does not make sense that I should have to do this. I am in the Denver area, so the altitude is roughly 6,000 feet where I am on the front range.

I am running 9PSI boost, high volume fuel pump, and Uberdata.

Any ideas, especially from someone who may have encountered this would be appreciated!

Thanks!!

B94Cast

TTT

ion_four

You are running an uberdata chip AND using and AFC? what are the settings on the afc, and is the chip trimming fuel as well? I would set the AFC to 0% trim, and only use it to do on the fly tuning of a couple percent. THEN, when you have the car where you want it, take the AFC out and sell it on eBay

::EDIT:: Also, what size injectors are you running? You could try the sensor check on the AFC and see what the input (or is it ouput?) voltage of the MAP sensor is, or you could verify the in and out with a voltmeter and see if the AFC is fucked up.

Bottoz

Altitude my friend...its all Altitude. I was wondering the same thing when I insalled my AEM EMS. At about 5500 feet, we're only getting about 11.7 psi of normal air pressure.....sea level air pressure is 14.7. There's your missing 3psi. This is why Altitude is a killer of power.

Im assuming you have a 9psi spring in your wastegate. If you look at a mechanical boost guage, at full boost the mechanical boost guage will read 9psi. Thats because a mechaical boost guage reads 0 psi no matter what altitude it is at.

Your electronic boost guage (MAP sensor), reads the Absolute Pressure of the air. Therefore, since you are starting out at about -3 psi due to altitude....add 9 to -3 you get +6.

So, you're boosting 9psi of Colorado air, and only 6psi of Sea Level air. Using this theory, I've been boosting 12psi of up here for a while...which equals to the 9psi of sea level boost I wanted. Granted, the turbo is spinning faster to pump more air....but the actual ammount of air entering into the engine is safe.

Bottoz

B94Cast

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bottoz &raquo;</TD></TR><TR><TD CLASS="quote">Altitude my friend...its all Altitude. I was wondering the same thing when I insalled my AEM EMS. At about 5500 feet, we're only getting about 11.7 psi of normal air pressure.....sea level air pressure is 14.7. There's your missing 3psi. This is why Altitude is a killer of power.

Im assuming you have a 9psi spring in your wastegate. If you look at a mechanical boost guage, at full boost the mechanical boost guage will read 9psi. Thats because a mechaical boost guage reads 0 psi no matter what altitude it is at.

Your electronic boost guage (MAP sensor), reads the Absolute Pressure of the air. Therefore, since you are starting out at about -3 psi due to altitude....add 9 to -3 you get +6.

So, you're boosting 9psi of Colorado air, and only 6psi of Sea Level air. Using this theory, I've been boosting 12psi of up here for a while...which equals to the 9psi of sea level boost I wanted. Granted, the turbo is spinning faster to pump more air....but the actual ammount of air entering into the engine is safe.

Bottoz</TD></TR></TABLE>

THANK YOU!!!
That makes absolute sense!
I work down in the springs... I will have to buy you a beer or lunch or something!!


Now, to get the uberdata to stop swinging lean....

Thanks for the suggestion ion_four - I think I will do exactly that - ebay, here I come!

ion_four

DAMNIT! I wish I'd noticed his location...I MIGHT have thought of that

Mr. Softee

Also, a note... hearing that loud turbo spool doesn't mean for sure you are making boost yet... usually it means you are right about to


get to the dyno

B94Cast

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94goldjungsr &raquo;</TD></TR><TR><TD CLASS="quote">Also, a note... hearing that loud turbo spool doesn't mean for sure you are making boost yet... usually it means you are right about to


get to the dyno </TD></TR></TABLE>

Know of any good ones in Colorado?

Bottoz

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B94Cast &raquo;</TD></TR><TR><TD CLASS="quote">

Know of any good ones in Colorado?</TD></TR></TABLE>


There's http://www.dynopro.com and http://www.paragontuning.com in Denver. Suposedly there is a new one near the Springs. When I get back from Afghanistan I'll be using http://www.pfispeed.com in Ft. Collins.

Bottoz