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View Full Version : Which N75 valve to go with?



sixfiveoh
08-04-2007, 08:22 PM
So basically, I believe that I have a faulty N75 valve, my car is holding about 75% of the boost it should be holding at full throttle. So I'm going to replace the valve, but was wondering which of the variants I should go with. I was originally going to go with the ECS N75 Race Valve http://www.ecstuning.com/stage/n75-info.html but I started to come across some stories of the excessive spiking causing the car to go into limp mode. Plus I don't know how that could be good for the car, loading an extra 3psi just from a valve. I know next to nothing about these things, however. This is what it looks like my choices are:



1.8T N75 Valves

1.8t N75 valve (version C): The N75 valve controls the wastegate of your turbo. This is a direct replacement for your OEM stock 1.8t N75 valve. This valve is from a 1.8T AWD motor and is the smoothest boost delivery of all the valves.

1.8t N75 valve (version J): This is the N75 valve from an Audi TT 225. The installation of this valve may cure surging issues and regulate boost pressures with possible boost level gains! More Power! A perfect balance of power delivery and increased boost levels!

1.8t N75 valve (version H): Want extra PSI? Just with the installation of this valve you can increase the whole turbo boost range by up to 3 PSI. More pounds of boost will give you additional HP due to the characteristics of this valve. This is also known as N75 RACE valve!

Anyone gone thru this, or are running any of the above N75 valves? Any input is very much appreciated [up]

Burntaudi
08-04-2007, 08:43 PM
Get the F. It's the replacement for the C and seems to be a bit smoother holds a little better but boost's the same. They don't make the C anymore the F supersedes it.

sixfiveoh
08-04-2007, 08:55 PM
So basically don't screw around with the ones that say they deliver more boost?

Audi91a4
08-04-2007, 09:54 PM
sixfiveoh, how did you know your N75 was going bad? CEL?

sixfiveoh
08-04-2007, 09:57 PM
No CEL, but if you look at a previous thread I made, I took the car to a shop and they told me my turbo was dead, which I just totally didn't believe, my car only has 50k on it, so I met up with a forum member and he vagcom'd it and I got this code
http://wiki.ross-tech.com/index.php/17956/P1548/005448
But my CEL wasn't on, strange. So I assume it's either a faulty N75 or something short circuited when we were installing my turbo timer, but I'm hoping it's the N75...

Audi91a4
08-04-2007, 10:00 PM
yeah I have a simmiliar problem. Are you chipped? what do you have for boost numbers with the bad N75?

sixfiveoh
08-04-2007, 10:04 PM
Nope, I'm stock. The logging we did wasn't measured in PSI, it was in mBar for some reason, but at WOT my car should be hitting 1600mBar, and I was only hitting around 1400mBar. For some reason that doesn't really convert to psi right, as 1600mBar is like 23psi, so maybe I'm mistaken on the measurement we used, but I do know whatever it was, I was supposed to be at 1600 and I was only at 1400, and when we logged his car in stock mode, also a 1.8T, he was on par with the 1600.

speedydragon
08-04-2007, 10:08 PM
You think it'll cause me to go into limp mode when chipped? Because their little chart thing says it's compatible on a 1999-2002 A4 chipped...

I've seen a few members here on az and other audi forums go into limp mode due to either the "h" or "k" valve. It's made for our cars, but once our ecu senses too much boost, especially with an added chip, it'll go to limp mode. I guess the "f" valve is the direct replacement, while the "j" would be an upgrade since it comes from the tt225, just like the "710n" dv. Since you're planning to with giac, I suggest you don't pursue the "h" valve. I'm guess the "f" and "j" are you best bet, while the "k" seems to be unknown.

Audi91a4
08-04-2007, 10:09 PM
Gotcha. Good luck with it and just hope its the N75. You could also replace it with a manuel boost controler and eliminate the N75 and make a little more power if you want to go that route chipped or not.

sixfiveoh
08-04-2007, 10:13 PM
I've seen a few members here on az and other audi forums go into limp mode due to either the "h" or "k" valve. It's made for our cars, but once our ecu senses too much boost, especially with an added chip, it'll go to limp mode. I guess the "f" valve is the direct replacement, while the "j" would be an upgrade since it comes from the tt225, just like the "710n" dv. Since you're planning to with giac, I suggest you don't pursue the "h" valve. I'm guess the "f" and "j" are you best bet, while the "k" seems to be unknown.

I see. Thanks for the input, I'm hoping I'll be fine with the "J" as it doesn't look like it will increase boost much at all, but solves surging issues. Sounds good to me? I'm still not sure [:p]


Gotcha. Good luck with it and just hope its the N75. You could also replace it with a manuel boost controler and eliminate the N75 and make a little more power if you want to go that route chipped or not.

Yeah, I considered it, but I'd really rather not run too much boost on a stock internal, stock turbo'd motor. Don't want more problems than I can deal with, I want this thing to be reliable.

Burntaudi
08-04-2007, 11:33 PM
I've seen a few members here on az and other audi forums go into limp mode due to either the "h" or "k" valve. It's made for our cars, but once our ecu senses too much boost, especially with an added chip, it'll go to limp mode. I guess the "f" valve is the direct replacement, while the "j" would be an upgrade since it comes from the tt225, just like the "710n" dv. Since you're planning to with giac, I suggest you don't pursue the "h" valve. I'm guess the "f" and "j" are you best bet, while the "k" seems to be unknown.

Not sure where your getting your info but your WRONG. The J valve is not from a 225TT. The J, H and K Valves are from inline 5 cylinder turbo motors from the 90's.

sixfiveoh your a 2001 stick with stock which is the F valve. Otherwise you will hit limp mode or at the very least you will over boost and get throttle cut.

sixfiveoh
08-05-2007, 12:54 AM
Hmm, well what do you think? Should I just go with a Forge MBC or something?

speedydragon
08-05-2007, 01:07 AM
Not sure where your getting your info but your WRONG. The J valve is not from a 225TT. The J, H and K Valves are from inline 5 cylinder turbo motors from the 90's.

sixfiveoh your a 2001 stick with stock which is the F valve. Otherwise you will hit limp mode or at the very least you will over boost and get throttle cut.

well earlier i did a search on google for the n75j and I saw on a few forums..(audiforums?) and a few other forums with audi in it, and users there posted the n75j is from tt225..that's where I got it from :D

Ado
08-05-2007, 01:36 AM
if your planing to keep the car stock, then what i would do i buy a stock n75 valve. if your planing on getting the car chipped then yea go with a race valve. i dont remember which latter i got got from DSR. since your in the bay area i would give them a call and find out. i think that 034motorsport has the same valve for $80. i would definitely give them a call. super nice guys.

speedydragon
08-05-2007, 05:32 AM
did some searching and found this http://audizine.com/forum/showthread.php?t=113725&highlight=n75 scroll down and read daft's post ^^

sixfiveoh
08-05-2007, 09:30 AM
did some searching and found this http://audizine.com/forum/showthread.php?t=113725&highlight=n75 scroll down and read daft's post ^^

Damn, looks like almost anything is gonna cause me to go into limp mode with GIAC-X? Unless I can get my hands on another N75C or N75F which I heard are both discontinued at the dealership?

Burntaudi
08-05-2007, 09:47 AM
Damn, looks like almost anything is gonna cause me to go into limp mode with GIAC-X? Unless I can get my hands on another N75C or N75F which I heard are both discontinued at the dealership?

You can get the F at the dealer. True the C is discontinued because the F replaces it. FYI I just bought a F at the dealer 2 weeks ago...they had it in stock.

HIERLEVELZ
08-15-2007, 05:26 PM
So did the N75 valve remedy your power loss. Im thinking i may have a similar problem seeing as im apr chipped and only hitting 10lbs of boost.

sixfiveoh
08-15-2007, 05:40 PM
It actually wasn't the N75 itself, it was a faulty connection to the N75. Everything's good as new now [up]