N75J on a standard 1.8T?

[spj]

Hi all,

Would it be benifical to replace my standard N75, with an N75J?
My car is standard...

Also, would it be worth replacing my diverter valve at the same time? It is 100000kms old now...

Thoughts?

Thanks.

[DUB 20V]

prob not you wont even notic it, save your money and get a ecu upgrade

[No457 Snowy]

As Adrian said forget it, unless the original DV is actually faulty and losing boost you'll gain nothing and if you go playing with the N75 you could create problems you don't have now.

Snowy

[schoona]

N75J is upgraded spark plugs right?
Sorry, not on it as far as mk4/1.8T tuning goes.

I can't for the life of me see how this would have a detrimental effect. If the same gap is maintained, it is a guarantee for the next xxx kms that your plugs are fine.

What is the cost like for the set of 4?

[DUB 20V]

N75J is upgraded spark plugs right?
Sorry, not on it as far as mk4/1.8T tuning goes.

I can't for the life of me see how this would have a detrimental effect. If the same gap is maintained, it is a guarantee for the next xxx kms that your plugs are fine.

What is the cost like for the set of 4?

stick to the merc mate

[gpk_gti]

sorry adrian but I did a dyno with and without the n75j and there was a slight difference in the psi (dont ask me for the exact figures but if I find the dyno sheet ill post the difference for you).for the $100 it was worth it.

[gpk_gti]

N75J is upgraded spark plugs right?
Sorry, not on it as far as mk4/1.8T tuning goes.

I can't for the life of me see how this would have a detrimental effect. If the same gap is maintained, it is a guarantee for the next xxx kms that your plugs are fine.

What is the cost like for the set of 4?

hahahhahahhha,,,,another gold post!!! ...guys,lay off the booze!!! cant you wait till xmas day?????????????

its the solenoid the controls the amount of boost to the waste gate,,,,something like that.....

[h100vw]

hahahhahahhha,,,,another gold post!!! ...guys,lay off the booze!!! cant you wait till xmas day?????????????

its the solenoid the controls the amount of boost to the waste gate,,,,something like that.....

George is pretty close, it is modulated by the ECU to control the boost and in extreme circumstances will open the wastegate using stored vacuum to prevent any exhaust gas making it to the turbo.

http://s4wiki.com/wiki/N75

I forget which way round it is but I would say not to fit anything but the std one for your engine, unless the software has been specifically written for another valve.

There is a chance that a non-standard valve will cause the ECU a headache and put the car in limp mode.

Gavin

[schoona]

bahaha quite obviously i really had no idea about 1.8T's!
for some reaosn (i think it may be pogo GTI's sig's) I associated NGK with N75J. NFI why, just did.

as they say, don't know if you don't ask.

[schoona]

stick to the merc mate

I don't want the Merc!!!!

[Bug_racer]

George is pretty close, it is modulated by the ECU to control the boost and in extreme circumstances will open the wastegate using stored vacuum to prevent any exhaust gas making it to the turbo.

http://s4wiki.com/wiki/N75

I forget which way round it is but I would say not to fit anything but the std one for your engine, unless the software has been specifically written for another valve.

There is a chance that a non-standard valve will cause the ECU a headache and put the car in limp mode.

Gavin

Deary me , we need a bit of a better explanation here as to how an n75 works , and I kinda guess we need an explanation on how the turbo works as well !


Everything either works on boost or a lack of it , there is no vacuum involved , the only vacuum in a turbo system is for the brake booster !

The exhaust gas exists the manifold and into the turbo . The turbo exhaust wheel is always spinning , if it wasnt spinning there would be very little intake air going in ! It spins to create positive pressure to pressurize the turbo hoses , intercooler , manifold etc . At this point the wastegate is shut until it can completely pressurize the system to the point at which it is ordered to . If the throttle is wide open it will continue pressurising until it reaches peak efficiency before it drops off (this is where you need to look at compressor maps to find out turbo flow/efficiency) . Say you back off the throttle when turbo is at max boost , the boost control solenoid is given a signal to open the wastegate of the turbo to decompress the exhaust side of the turbo . It uses the positive pressure in the outlet side of the turbo that feeds the manifold . The Diverter valve depressurizes the intake side that goes to the manifold . The DV uses the change in pressure from one side of the throttle body to the other to regulate the pressure coming out of the turbo into the manifold , some DBW cars use an electronic solenoid to open/close the DV . It then dumps the excess pressure back into the intake pipe . Which is also how the n75 works , it also allows some pressure back into the intake if it doesnt require the wastegate of the turbo to be completely opened .

Any Q's ?

[h100vw]

My explanation wasn't perfect, so thanks for sorting that out.

What's the score with the J valve, which was the original question.

Gavin

[madglf3]

Deary me , we need a bit of a better explanation here as to how an n75 works , and I kinda guess we need an explanation on how the turbo works as well !


Everything either works on boost or a lack of it , there is no vacuum involved , the only vacuum in a turbo system is for the brake booster !

The exhaust gas exists the manifold and into the turbo . The turbo exhaust wheel is always spinning , if it wasnt spinning there would be very little intake air going in ! It spins to create positive pressure to pressurize the turbo hoses , intercooler , manifold etc . At this point the wastegate is shut until it can completely pressurize the system to the point at which it is ordered to . If the throttle is wide open it will continue pressurising until it reaches peak efficiency before it drops off (this is where you need to look at compressor maps to find out turbo flow/efficiency) . Say you back off the throttle when turbo is at max boost , the boost control solenoid is given a signal to open the wastegate of the turbo to decompress the exhaust side of the turbo . It uses the positive pressure in the outlet side of the turbo that feeds the manifold . The Diverter valve depressurizes the intake side that goes to the manifold . The DV uses the change in pressure from one side of the throttle body to the other to regulate the pressure coming out of the turbo into the manifold , some DBW cars use an electronic solenoid to open/close the DV . It then dumps the excess pressure back into the intake pipe . Which is also how the n75 works , it also allows some pressure back into the intake if it doesnt require the wastegate of the turbo to be completely opened .

Any Q's ?

Thanks for that mate, good info. I too was wondering what it did.

[gpk_gti]

wow,the professor has spoken....too much info got a headache! hahhaa


I was running the n75j for a few weeks without a upgraded ecu without having any issues....

[No457 Snowy]

Following on from Seb's explanation, the way I always understood it as a "non-mechanic", compared to stock, the N75J is "slower" in opening the turbo's wastegate thus helping build a bit more turbo boost and keeping actual pressure most of the times above the ECU's requested pressure.

When you ask people that have done it, responses seem to vary, but in some cases if your stock ECU sees that as an "over-boost" situation it can put you into limp mode to protect the engine.

So after 2 pages of responses I think your question was really answered in the first two response posts.



Snowy