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View Full Version : does a blown turbo still produce a small amount of boost?



tamadrumr88
12-08-2007, 01:17 PM
my friend has a '97 1.8t and we just did a boost leak test this afternoon and we couldn't seem to find any boost leaks even after pressure testing it up to ~18-20psi

would a blown turbo still produce 4psi with a leak-free system?

Brooksthepro
12-08-2007, 01:23 PM
if your car is boosting 4-5psi its probably in limp mode. Do u have a CEL?

ILoveT
12-08-2007, 01:27 PM
I'm pretty sure NDBW cars don't have limp mode.

seank
12-08-2007, 02:06 PM
^ correct

Brooksthepro
12-08-2007, 02:23 PM
I'm pretty sure NDBW cars don't have limp mode.

your right. opps. wasnt paying attention to the year.

mike-2ptzero
12-08-2007, 03:52 PM
I'm pretty sure NDBW cars don't have limp mode.

They do, all the A4's have a safe mode which runs the car at a lower boost level. The ndbw just doesn't get put into that mode by the same things that cause a dbw to go into limp mode.


tamadrumr88 - yes a blown turbo can produce some boost if the wheels are still turning, even if the compressor wheel is some what chewed up it will produce some boost.

pinky
12-08-2007, 04:07 PM
when my wastegate died, i was making 1-2psi..

ILoveT
12-08-2007, 04:33 PM
They do, all the A4's have a safe mode which runs the car at a lower boost level. The ndbw just doesn't get put into that mode by the same things that cause a dbw to go into limp mode.


tamadrumr88 - yes a blown turbo can produce some boost if the wheels are still turning, even if the compressor wheel is some what chewed up it will produce some boost.

Thank GOD, a definite answer! I never really knew that all of them had that safety feature. I always thought it was the general consensus that there was no such feature for the ndbw.

Kunundrum
12-08-2007, 05:07 PM
i'm having the same issue, and I have been told to check the N75 valve...

HIERLEVELZ
12-08-2007, 05:36 PM
I'm pretty sure NDBW cars don't have limp mode.

oh yes they do...experienced it first hand.

ILoveT
12-08-2007, 05:39 PM
Hows that?

AudiRacerS4
12-08-2007, 06:48 PM
Hows that?

unplug the N75 or the maf on a nDBW car and you will go into limp mode

audiness
12-09-2007, 09:20 AM
probably bad wastegate

fikes
12-09-2007, 09:51 AM
Hey. I have a 97 1.8t and I went from 15psi to 3 boost after I found out my throttle body died. I did boost leak tests and all and it turned out to be the TB. Give that a try to see if its dead.

ct1.8t4me
12-09-2007, 10:11 AM
The NDBW Limp mode is not the same as the DBW limp. The NDBW ECU does not have the ability to close the throttle, etc. If you unplug the N75 valve the ECU will throw a CEL, but it really isn't preventing you from doing anything. You get 5 PSI because that is what the spring in the wastegate is going to limit you to. Disconnect the wastegate and see how the ECU protects you in "limp" on a NDBW car - it doesn't.

tamadrumr88
12-09-2007, 10:23 AM
it's not the n75 because i sold it to the kid and it was working fine... i sold him my giac ko3 ecu, samco inlet, forge dv, and n75h valve. on my car it was pushing 20-22psi and it felt so strong... now we put it on his car (which i think has around 140k miles) and it's pushing like 4psi

i'm thinking of just replacing it with a k03 sport and calling it a day

ct1.8t4me
12-09-2007, 10:25 AM
With that info - I bet the wire for the N75 is broken. They like to snap inside the rubber boot, and like I said, you get stuck with whatever the wastegate spring gives you.

Also, what about a TBA? Any CEL/codes?

fikes
12-09-2007, 01:16 PM
unplug the N75 or the maf on a nDBW car and you will go into limp mode

I have a 97 and unplugged the n75 many times and never threw a cel or went into limp mode.

ILoveT
12-09-2007, 01:21 PM
I have driven my car with it unplugged also and I didn't get a CEL either. Just get your multimeter out and check the resistance. That will tell you if the wires are broken or not.

mike-2ptzero
12-09-2007, 03:10 PM
The NDBW Limp mode is not the same as the DBW limp. The NDBW ECU does not have the ability to close the throttle, etc. If you unplug the N75 valve the ECU will throw a CEL, but it really isn't preventing you from doing anything. You get 5 PSI because that is what the spring in the wastegate is going to limit you to. Disconnect the wastegate and see how the ECU protects you in "limp" on a NDBW car - it doesn't.

Limp mode is the same on both ndbw and dbw. The throttle closing on the dbw is not a limp mode but just another safety that audi included on the dbw cars. Once the ecu sees that the problem for closing the throttle to 40% is no longer there it allows the throttle to go 100% again of if you lift and go wot again you will get 100%. Limp mode has nothing to do with over boosting on the dbw car.

SpyderSE2
12-10-2007, 07:44 PM
it's not the n75 because i sold it to the kid and it was working fine... i sold him my giac ko3 ecu, samco inlet, forge dv, and n75h valve. on my car it was pushing 20-22psi and it felt so strong... now we put it on his car (which i think has around 140k miles) and it's pushing like 4psi

i'm thinking of just replacing it with a k03 sport and calling it a day

I had an issue where I could only make 4psi of boost. I tore out the ko3 and replaced it. To my dismay the problem was still there. Ended up being a clogged Cat. If I were you I would pull the pre-cat o2 sensor and see if the car builds more boost than when its plugged in. Its a quick easy test before you spend the to replace the turbo. Just my 2 cents.

Wakeboardosurf
12-11-2007, 07:36 AM
Wow guys im havin the same problem.

these are my thoughts on the matter

Its not the n75 valve we know....
there are no leaks and its not the throttle body or any of that mess
youve got a basic 1.8t engine, the analog version i like to call (we have cables)
its only a few possible things that could be causing this
spyderse2 has a great point this is what i think your problem is.

Check your cat number one.

Im having the SAMEEEE PROBLEM!!! with my gt28rs turbo. Did you notice a sound difference? or anything. my car sounds more motor now, cant wait to install my testpipe and get that damn boost back !!!

Wakeboardosurf
12-11-2007, 10:02 AM
I had an issue where I could only make 4psi of boost. I tore out the ko3 and replaced it. To my dismay the problem was still there. Ended up being a clogged Cat. If I were you I would pull the pre-cat o2 sensor and see if the car builds more boost than when its plugged in. Its a quick easy test before you spend the to replace the turbo. Just my 2 cents.

THIS IS YOUR PROBLEM

TAKE OUT YOUR FRONT 02 SENSOR AND TAKE HER AROUND THE BLOCK
YOU SHOULD BOOST HIGHER, THIS WILL TELL YOU FOR SURE.