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This is suspicious - just as I was coming home, I pulled away from a light, no boost, and shifted into second and the car stalled in the middle of the intersection. I suspect my vacuum like is still alive, and well...
The N75 valve is a pretty simple device... just a 12V triggered 'switch' that connects output C to either input A or B. Very simple to bench test, and not likely to be a 'partial failure'. It's either going to work or it isn't. Double check all the hoses going to it, some are prone to cracking, especially the little 90 degree elbow that connect to the y pipe.
If the N75 isn't switching properly, I believe it's "off state" (no voltage applied) is to feed the y-pipe (boosted pressure) input to the wastegate output to prevent overboost, which would mean that the wastegates are opening at the default spring pressure, which is more like .5 bar.
For those not familiar with the N75, when it 'switches' (which it does rapidly), instead of feeding boosted pressure to the wastegates, it connects just intake vacuum, essentially tricking the wastegates into thinking the turbos are making less pressure then they are. The ECU turns the E75 valve on and off rapidly to control the exact boost pressure it is requesting. Without it, the turbos would be controlled strictly by the wastegates, which in our cars are set pretty low.
The N75 valve is a pretty simple device... just a 12V triggered 'switch' that connects output C to either input A or B. Very simple to bench test, and not likely to be a 'partial failure'. It's either going to work or it isn't. Double check all the hoses going to it, some are prone to cracking, especially the little 90 degree elbow that connect to the y pipe.
If the N75 isn't switching properly, I believe it's "off state" (no voltage applied) is to feed the y-pipe (boosted pressure) input to the wastegate output to prevent overboost, which would mean that the wastegates are opening at the default spring pressure, which is more like .5 bar.
For those not familiar with the N75, when it 'switches' (which it does rapidly), instead of feeding boosted pressure to the wastegates, it connects just intake vacuum, essentially tricking the wastegates into thinking the turbos are making less pressure then they are. The ECU turns the E75 valve on and off rapidly to control the exact boost pressure it is requesting. Without it, the turbos would be controlled strictly by the wastegates, which in our cars are set pretty low.
that's interesting info.
what would you venture if you had to guess would cause a "new" n75 install to create a boost level limited to .6 on a car that prior to the swap fully boosted to 1.3 and had an accompanying soft code" stored = p 0234 "overboost condition" - but no "cel's" etc.
seems odd. i havent checked again to see if the code is still stored or not as i only have an obd reader. obviously a vac leak is now suspected.
Drove my new to me tt from the deep south to the northeast. Encountering a bad tank of gas in Tennessee that made me think the car was having a problem. Good gas resolved the issues.
Drove my new to me tt from the deep south to the northeast. Encountering a bad tank of gas in Tennessee that made me think the car was having a problem. Good gas resolved the issues.
09-03-2020, 08:26 PM
