Natty Boh

Anybody ever had issues using the N75 F with a boost machine. I replaced the C N75 with an F and now the car overboosts and can't be controlled with the boost machine. I understand that the C valve has been replaced with the F valve because the C was problematic. The F does seem to hold boost better but it's holding boost at 26psi...no good

TTschwing

Put the C back in. N75's are rarely problematic so I don't know where you heard that. The Boost Machine essentialy operates like a Variable N75 and always operates best with the stock N75.

Turn it off (Full clockwise on the regulator, full counterclockwise on the Relief valve) and let the car settle in and see where you end up, then adjust from there. Some of the latest X chips files are boosting unusually high.<ul><li><a href="http://www.modshack.info/bminstall.htm">Boost Machine tuning..</a></li></ul>

joe@vwvortex

My 03 came with an F stock ...........weird

Natty Boh

Thanks steve, I'm going to put the c valve back in. I knew all the newer cars were coming with the f valve so I wanted to try it out. I have been using the xchip for about 18 months, did recently have it upgraded when I changed to flashloader, but didn't see a difference in boost until I put the f valve in. Guess its the way the f valve reacts with the 01 program

joe@vwvortex

however - i've hard problems with boost stock - and my TT is getting a new turbo. I'm curious to see what type of boost levels i'll get when it fixed.

kodeTT

programming the ECUs. Dahlback recommends the "J" valve and works well with the car and chip. i'm pulling 25-26psi...and with the d-chip, the duty cycle operates differently...with more frequent on/off cycles so the turbo doesn't overheat with 26 lbs of boost...at least what i am told.

TTschwing

At least on the turbo side. Higher duty cycle means the wastegate stays shut more for higher boost.....It seems that DB maintains cyclinder cooling with a VERY rich A/F ratio Bill..

kodeTT

as far as the duty cycle...DB has a lower duty cycle...about 82% which opens and closes more frequent than APR and GIAC, which probably keep the turbo cooler, i would think

TTschwing

you actually have a HIGHER (numerically) duty cycle. 100% meaning no signal to the wastegate actuator and where most programs start from idle until the program starts to bleed boost and taper as a control measure. The wastegate is fully closed at 100% (Minimal to no lag). The number lowers as RPMs rise and more pressure is sent to the actuator, cracking the valve open to balance requested boost. Higher numbers force the turbo to work harder hence more heat. APR tapers to about 65%.

kodeTT

but i thought the APR had a higher duty cycle. oh well...i'll leave all those digits up to the programmers...what do i know. haha.

all i know is that the DB chip likes the Greddy RS valve. i also replaced a cloth covered hose that looked like it was getting worn on a corner...holding boost longer and the car feels pretty strong these days...with new 'low' exhaust pipes.