N75 Question...

[EErie B6]

after searching the forums, i found that i have a surge problem, and it appears to be my n75

my question is, what kind do i want to replace it with? o.e, ecs, or is there a better option?

car in question is a 99.5 B5, stock with APR 1.0, and R1 DV

thanks

[CyberPMG]

Get the regular N75-F. You can get it either from the dealer or some sort of online parts store (ECS). Don't get the J or H race valve.

[My OOOO My]

Get the regular N75-F. You can get it either from the dealer or some sort of online parts store (ECS). Don't get the J or H race valve.

Why do you NOT recommend the J or H valves ???

[EErie B6]

Thank you...

what is different about the "j" and "h" valve that makes them bad?

[CyberPMG]

The J and H versions are considered "race" N75s. With the smaller turbo (K03/K04), it can cause overboosting and throw you into limp mode. You would need a manual boost controller (MBC) to compensate the J and H versions of the N75.

[EErie B6]

forgive me for asking a dumb question.. well another one

isnt it the ecm that monitors and controls the boost level?

i was under the impression that the ecm sends a signal to the n75 which actually has to do the dirty work of manhandling the wastegate... the ecm telling it when, where, and how much.

i... (and this word gets me in trouble) ASSUMED that the race valve was simply a stronger "muscle" to better deal with higher than stock boost levels? ... and the ecm would tell it to back off, once the desired level was reached?

but now i gather that that thought is completely wrong?

How does this system really work?

and thanks for your input so far.

[EErie B6]

i think i might have figured out my own question...

in comic form...
as the engine winds up, it can ingest more air, and while trying to hold the boost level that the ecm calls for...the turbo maxes out, boost begins to fall, the ecm says: "more boost," to the n75, and the n75 replies: "im trying my best", the ecm says: "do better" so the n75 holds the wastegate closed, with no regard for turbine rpm, thus overspeeding the turbo? ...or very similar... except in German... we all know the car and all it's parts speak german. =P

or is that completely wrong too?

[My OOOO My]

i think i might have figured out my own question...

in comic form...
as the engine winds up, it can ingest more air, and while trying to hold the boost level that the ecm calls for...the turbo maxes out, boost begins to fall, the ecm says: "more boost," to the n75, and the n75 replies: "im trying my best", the ecm says: "do better" so the n75 holds the wastegate closed, with no regard for turbine rpm, thus overspeeding the turbo? ...or very similar... except in German... we all know the car and all it's parts speak german. =P

or is that completely wrong too?

LOL... LOL... LOL

John, that is the BEST description I have ever read

[EErie B6]

lol, thanks

im trying to understand how this component works, and that was all i could come up with that made sence.

another thing i dont understand is how the valve actually knows the approximate rpm of the turbine anyway. i would think that it would be trying to hold as much boost as possible, no matter what type it was, as long as the computer told it to do so.

could someone fill me in?

thank you.

[old guy]

lol, thanks

im trying to understand how this component works, and that was all i could come up with that made sence.

another thing i dont understand is how the valve actually knows the approximate rpm of the turbine anyway. i would think that it would be trying to hold as much boost as possible, no matter what type it was, as long as the computer told it to do so.

could someone fill me in?

thank you.

This should help: Clicky click Explained on a different VAG car, but the function is the same.

[EErie B6]

old guy, thanks a ton.