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View Full Version : 98 A4 APR Stage 3 ... after a hot HPDE weekend



Beemer832
08-13-2007, 06:12 AM
100+ degree temperatures, 125 degree ambient track temperatures, ok you get the point it was HOT. Ran the car very hard for a few laps and then would pull back and cool it down, then run it hard again. I noticed about 1/2 way through my first day the exhaust sounded louder and deeper and also my boost gauge was showing me hold 24-25psi almost regardless of how depressed the gas pedal was.

this didnt really bother me as the car was running strong, felt good, and no CEL's lighting up my dashboard. Oil temp and coolant temp looked good, no oil leaks, and no smoke. Car is still running fine, but now it seems whenever i depress the gas pedal it just wants to spool up and boost quickly. I am use to slowly giving it gas and slowly raising boost barely ever going full boost when driving around town.

My questions are, did I break something as in a seal or gasket somewhere in the turbo or exhaust system? Does the APR software have an adaptive characteristic to it where it will spool up faster and drive harder when you really beat on it, and then when you drive it at NO boost all day long, it tames itself down. Also i was informed that APR does an upgrade flash for ECU's. Any idea if this is true and what it entails cost and time?

Car has about 58k on the turbo kit.


thanks
josh

offroader1006
08-13-2007, 07:10 AM
so, now you got faster spool, and are complaining?[confused]

have you looked to see if your exhaust is still attached to the turbo?

mike-2ptzero
08-13-2007, 07:12 AM
Sounds like your vac line to your wg might have popped off causing the turbo to spool up quickly since there isn't enough pressure being sent from the N75 to crack the wg open to soften how the boost builds. Basicly giving you that on/off feeling a MBC tends to give you.

Beemer832
08-13-2007, 07:14 AM
haha well not complaining, but i was loving the good gas mileage before. also now if i get onto it and let off, with full boost, the engine like stutters because you are full on, and then full off.... its just kinda of not driver friendly anymore, but great on the track :).. i was passing M3's left and right.

and YES the exhaust is still attached, it just sound really loud though now. I am wondering if something came lose or i created a leak. it is running a test pipe right off the turbo with no cat into a 2.75" exhaust..

thanks
josh

Beemer832
08-13-2007, 07:40 AM
Mike,

I dont have a waste gate. at least I dont think i do. Please bare with me as I am very knew the turbo scene and not really sure how everything works yet. My understand is th WG is built into the GT28 turbo is this correct? So the line you are talking about must be somewhere near the turbo. also i ahve a purple colored valve which i am assuming the DV N75 valve which comes off the turbo down by the ground. i think this is called the turbo inlet pipe? i am so confused by names. anyways it is a silicone piece that attaches from the turbo down into the intercooler and has various nipples and hoses coming off of it.
I really appreciate everyones help so far, i hope to get this fixed so Im not worried about blowing anythign up : )

josh

mike-2ptzero
08-13-2007, 07:49 AM
Mike,

I dont have a waste gate. at least I dont think i do. Please bare with me as I am very knew the turbo scene and not really sure how everything works yet. My understand is th WG is built into the GT28 turbo is this correct? So the line you are talking about must be somewhere near the turbo. also i ahve a purple colored valve which i am assuming the DV N75 valve which comes off the turbo down by the ground. i think this is called the turbo inlet pipe? i am so confused by names. anyways it is a silicone piece that attaches from the turbo down into the intercooler and has various nipples and hoses coming off of it.
I really appreciate everyones help so far, i hope to get this fixed so Im not worried about blowing anythign up : )

josh



You have a internal wg and there will be a wg actuator bolted to the compressor housing of the turbo and there will be a vacuum line coming off of the front of that actuator. This is the line you want to look for and check to see if it is there or if there is a leak/crack in it.


Yes that purple thing is a BPV, it is in the turbo outlet pipe. The turbo inlet pipe/hose is connected to the front of the turbo and goes to the air box. The N75 valve is mounted into the turbo inlet pipe which is where the wg vacuum line also goes into. One of the other lines from the N75 will go to the compressor housing of the turbo if not there it will be connected to the turbo outlet hose since it a "pressure" hose that sends pressure to the N75 valve while the turbo is making boost. These are the 2 hoses(both at the N75 valve) you need to check.

Don Supreme
08-13-2007, 08:19 AM
No wastegate hehehhe.

Beemer832
08-13-2007, 08:22 AM
ahh wow this is confusing, i really wanna tear that turbo off one day and see what all of this stuff is. ig uess I better wait until i really do need to take it off. I will be checking these lines tonight when I get home. Any other reason why the exhaust sounds louder and deeper? Sounds like you can hear the turbo a lot more. Gotta love that pulsating exhaust note....


Josh

Beemer832
08-13-2007, 08:44 AM
so the wastegate is NOT a BOV. Because i was referring to i do not have a BOV. I didn't realize that they must have a wastegate which i assumed was the same as a BOV. I understand the BPV is a recirculatin valve that dumps excess boost back into the intake or the engine to decrease turbo lag between shifts.

Lazer Viking
08-13-2007, 08:52 AM
no no, the bov/dv pushes out excess air from the compressed (cold side)

the wastegate, does just that lets the wasted gasses out of the hot side of the turbo

lamens terms for you

Beemer832
08-13-2007, 09:00 AM
mm interesting. I really need to figure out how these things work. i thought the exhaust gas's just push through the turbine, and everything that goes through exits the exhaust, the cold side then is attached by the main shaft which also has a spinning turbine which compresses the air. so the wastegate keeps pressurized air in the hot side of the turbo and then when it builds enough psi, it lets this exit the exhaust. Is this why you get a pulsating exhaust waves which creates the turbo exhaust note?

josh

AudiRacerS4
08-13-2007, 09:09 AM
your wastegate line definetly popped off and the reason your exhaust seems louder is your building boost soon as you step on the gas and you can hear the turbo spool and the sound is loud.

Lazer Viking
08-13-2007, 09:39 AM
exactly. wastegate no open, turbo spools all the time

Beemer832
08-13-2007, 09:48 AM
so the WG line is on the hot side of the turbo, or the actuator located on the cold side of the turbo? I checked real quick and the actuator line LOOKED attached, but there could still be a leak somewhere. Weird how its still holding 22-25 psi, or would this not be considered a boost leak?

josh

Euro-Tuner
08-13-2007, 10:01 AM
what is the downside to leaving the wastegate closed? less turbo life, less daily driver friendly? is that it?

Lazer Viking
08-13-2007, 10:05 AM
the wg actuator is on the hot side, should be a round little cadmium plated thing on the hot side of the turbo, with a vac line hooked to that
your boost should hold fine, no not a boost leak, vac leak if anything.. if your boost gauge reads vac, check to make sure thats where it should be at idle, 15-20 hg

the down side, over boosting conditions, running lean, shorter turbo life, lower gas mileage, etc etc etc

onemoremile
08-13-2007, 10:12 AM
If there was no wastegate and all of the exhaust gasses passed through the turbine then the car wouldn't be able to regulate boost. It would be an all or nothing scenario like you have now. The wastegate stays closed to let all the exhaust hit the turbine or opens to let exhaust gasses skip past the turbine. This is how turbos regulate boost. External wastegates do the same thing but tend to be a bit more efficient.

http://auto.howstuffworks.com/turbo.htm

Beemer832
08-13-2007, 10:21 AM
ahh this would explain running lean. I would be hard on the car through turns and straights, and as it got hotter it seemed to start to lose power or almost studder, my instructor siad low on gas which it was. It did get better after I had a full tank but not fixed. I will be tearing my engine bay apart tonight getting down into the turbo. I need to get rid of my nasty looking airbox..... its such a PIA

josh

mike-2ptzero
08-13-2007, 06:37 PM
the wg actuator is on the hot side, should be a round little cadmium plated thing on the hot side of the turbo, with a vac line hooked to that
your boost should hold fine, no not a boost leak, vac leak if anything.. if your boost gauge reads vac, check to make sure thats where it should be at idle, 15-20 hg

the down side, over boosting conditions, running lean, shorter turbo life, lower gas mileage, etc etc etc

You mean on the "cold side" since the front of the wg actuator is bolted to the compressor housing(cold side) of the turbo.


The gold colored part in this picture is the wg actuator.
http://www.tougefactory.com/shop/images/539_th.jpg

Here is is from the front of the turbo.
http://www.tougefactory.com/shop/images/562.jpg

Lazer Viking
08-13-2007, 08:27 PM
sorry, meant cold side... good catch mike

Beemer832
08-14-2007, 06:17 AM
ahhh thanks everyone for the help. I finally found the problem last night after tearing the car apart. the vacuum line coming from the actuator going into this vacuum solenoid? it has three nipples with three vacuum lines running into it. anyways that hose had rubbed up against the engine was almost completely in half. luckily whoever put that kit together had about 100ft of extra hose laying around the engine bay so i just cut it shorter and relocated the solenoid out of the way. I was also lucky to find out that the turbo outlet pipe, not really a pipe but the silicone connection piece was almost all the way off the turbo. : O

still have an exhaust leak somewhere, I will get the car up on ramps tonight after it cools and have someone start it and see if i can find out where it is coming from. might just be the flex pipe or one of the joints.

thanks for all the help everyone, i would have been lost enjoying all that quick spooled up boost :)....

is it normal to hold 24-25psi? :)....

thanks
josh

Beemer832
08-15-2007, 06:02 AM
so i fixed the vacuum leak, and last night I found my exhaust leak. its where the flex pipe meets the back of the muffler, there is actually a few short pieces back there, but anyways its at one of the couplers. Looks like I will be taking care of that this weekend, going to use some high temp silicone seal to make a new gasket.

I also open up my exhaust dump which is basically running straight pipes out of the header :) boy that was fun and loud. Want to take that down the street next time and see how it runs..

thanks again for everyones help, i now understand a little bit more about how turbos work which will help me down the line when I need to replace/upgrade..

thanks again
josh

pinky
08-15-2007, 07:41 AM
the vacuum line coming from the actuator going into this vacuum solenoid? it has three nipples with three vacuum lines running into it.

that solenoid is the N75