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AudiTurbo
07-28-2014, 03:36 AM
So, I have had the n75 race for some time now and I finally decided to change back to a stock on. The reason I changed back to a stock one was because I was boosting to about 25 and I wanted to make sure my turbo lasted a little bit longer. When I got the pc-16 I told them I had the race valve. Is GIAC even able to tune for that n75 valve?

So, after installing the stock on, I noticed that I would hold boost a little better to redline, but the gauge would bounce up and down from about 21 to 18 psi, then fall off to about 16 at redline (I have a video, but don't know where to post, so I can link it in)

Could it be that the computer doesn't recognize the new n75 valve? I can not find a boost leak either.

Thanks

fed0ra
07-28-2014, 07:04 AM
So, I have had the n75 race for some time now and I finally decided to change back to a stock on. The reason I changed back to a stock one was because I was boosting to about 25 and I wanted to make sure my turbo lasted a little bit longer. When I got the pc-16 I told them I had the race valve. Is GIAC even able to tune for that n75 valve?

So, after installing the stock on, I noticed that I would hold boost a little better to redline, but the gauge would bounce up and down from about 21 to 18 psi, then fall off to about 16 at redline (I have a video, but don't know where to post, so I can link it in)

Could it be that the computer doesn't recognize the new n75 valve? I can not find a boost leak either.

Thanks

The N75s are interchangeable, no need to tune for it.

If you swap out an N75 for another that has a slightly different boost profile then I would reset the ECU after. The ECU does learn a bit about how your car is boosting (at least on the later cars) but I don't think thats your issue.

Is this a used stock N75 or a brand new one? You may have a bad one. I would try finding someone with a good one that will let you try it.

AudiTurbo
07-28-2014, 08:04 AM
Okay I will reset the computer, thanks. It's a used one

walky_talky20
07-28-2014, 08:09 AM
A 98.5 won't learn anything with regard to the N75. It just runs off a duty cycle map to pulse the valve. Try a reset, but I doubt it will behave any differently.

If it's oscillating, I would think your used valve is faulty. It probably works just fine on a stock tune at 7psi, but it's worn out and can't smoothly control boost at 1bar+. Not altogether uncommon. Controlling higher pressures is more demanding on the valve.

I would suggest you put your N75 "Race" back in and instead use a ball/spring type MBC in parallel to limit your max boost to whatever you desire. You will still get smooth boost onset and boost-by-throttle control, but the MBC will cut off on the top end.

AudiTurbo
07-28-2014, 10:46 AM
Okay I might have to do that, but I thought with the MBC in parallel it go full boost when you barely hit the gas?
Thanks

BaseDrifter
07-28-2014, 11:03 AM
That is if you remove the N75 from the system and use only a MBC for boost control.

You're looping in the MBC to prevent over boosting, not to control the boost at partial throttle, the N75 will still take care of that.

AudiTurbo
07-28-2014, 11:13 AM
What mbc would you recommend? link?

This okay? http://www.ebay.com/itm/Voodoo-V-MBC-Black-Manual-Turbo-Boost-Controller-Add-upto-30-PSI-Made-in-USA-/171195819980?pt=Motors_Car_Truck_Parts_Accessories&hash=item27dc10e7cc

AudiTurbo
07-28-2014, 11:43 AM
A 98.5 won't learn anything with regard to the N75. It just runs off a duty cycle map to pulse the valve. Try a reset, but I doubt it will behave any differently.

If it's oscillating, I would think your used valve is faulty. It probably works just fine on a stock tune at 7psi, but it's worn out and can't smoothly control boost at 1bar+. Not altogether uncommon. Controlling higher pressures is more demanding on the valve.

I would suggest you put your N75 "Race" back in and instead use a ball/spring type MBC in parallel to limit your max boost to whatever you desire. You will still get smooth boost onset and boost-by-throttle control, but the MBC will cut off on the top end.


Why not just use the stock n75 that is in now instead of the race valve again?
Thanks

fed0ra
07-28-2014, 12:02 PM
Why not just use the stock n75 that is in now instead of the race valve again?
Thanks

Because it is highly likely that your used n75 is bad. If you want to get a stock N75 I recommend buying it new. These things go bad after all of these years of use, so getting a used one is kind of a crapshoot.

AudiTurbo
07-28-2014, 12:03 PM
Okay thanks. Is that MBC okay? I know how to install it, but how do I keep it at like psi? Just play with it?

BaseDrifter
07-28-2014, 12:16 PM
I've got a spare known-to-be-working N75, if you're interested shoot me a PM.

walky_talky20
07-28-2014, 01:50 PM
Okay thanks. Is that MBC okay? I know how to install it, but how do I keep it at like psi? Just play with it?

You can either turn it all the way up and turn it down until it is trimming how you want,

or you can turn it all the way down, and turn it up until your hitting your desired max boost.

AudiTurbo
07-28-2014, 02:46 PM
You can either turn it all the way up and turn it down until it is trimming how you want,

or you can turn it all the way down, and turn it up until your hitting your desired max boost.

Okay thank you