GT-R turbos on the VQ37

husam2012 · 07-26-2017, 08:06 PM

Quote:

Originally Posted by Jayhovah

It looks pretty clear to me that your wastegates are set to ~12psi. It builds smoothly to that target and levels off.

I did some googling and it appears a stock GTR runs ~12psi... so it seems reasonable to me... though not exactly what I would have expected.

The million dollar question here is - can you change the springs on the OEM actuators, or adjust the tensioning?

Unfortunately not. I did research exactly that and everybody including my turbo said that running on just wastegate pressure (0 duty cycle in his gtr) it ran at about 8-9 psi. It's really weird that it's 12 psi on my car.

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Jayhovah · 07-26-2017, 08:13 PM

Quote:

Originally Posted by husam2012

Unfortunately not. I did research exactly that and everybody including my turbo said that running on just wastegate pressure (0 duty cycle in his gtr) it ran at about 8-9 psi. It's really weird that it's 12 psi on my car.

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Doing some more googling the answers seem a little all over the place.. though I haven't seen anyone say anything as low as 8-9... What model year did your turbos come from?

Here is the most informed-sounding (for what its worth) post:

Quote:

Boost is the same for 2012-2014 cars and then the same for 2009-2011.

It was usually measured right under 11 between (10.2-10.8psi) for the CBA then increased around 2 psi for the DBA. So yea its somewhere right at 13 stock

Max boost for 2014 GT-R? - R35 GT-R - GT-R Life

I am seeing a lot of 11, 12, 13psi posts from people. I'd be inclined to trust that kind of number since it's backed up by your own data. The curve you posted looks pretty cut and dry to me... Does not look like boost creep to me at all.

Rusty · 07-26-2017, 08:13 PM

Remember that the 3.8 and 3.7 are different motors. And the 3.7 is not a FI design. Any number of thing could cause the boost increase. Biggest I think is the difference in combustion ratios of the two. GT-R is 9 to 1, Z is 11 to 1.

Jayhovah · 07-26-2017, 08:18 PM

Quote:

Originally Posted by Rusty

Remember that the 3.8 and 3.7 are different motors. And the 3.7 is not a FI design. Any number of thing could cause the boost increase. Biggest I think is the difference in combustion ratios of the two. GT-R is 9 to 1, Z is 11 to 1.

This is true but I am not sure it applies in this case... If it was boost creep then these factors could certainly contribute. But to me this looks like his wastegates are opening at 12psi and they are activated purely on pressure alone...

07-26-2017, 08:13 PM	#3 (permalink)
Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 69 Posts: 35,351 Drives: 2011 Nismo GM 6M Rep Power: 2684438	Remember that the 3.8 and 3.7 are different motors. And the 3.7 is not a FI design. Any number of thing could cause the boost increase. Biggest I think is the difference in combustion ratios of the two. GT-R is 9 to 1, Z is 11 to 1. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

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