Nissan 370Z Forum - Yet Another DIY GTM TT Install

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Just a small update on how the car is doing, so far no leaks, no rattles, drivability is perfect. No startup issues, no hesitation, AFR seems in check though may be a bit rich in some areas under WOT, I have sent a few logs for Sam to look over.

I hope you all like my dremel mod =]

http://fbcdn-sphotos-a.akamaihd.net/...30785744_n.jpg

http://fbcdn-sphotos-a.akamaihd.net/...89566698_n.jpg

Nicely done. Looks very clean, especially for a temporary setup. How many psi do you get on the waste gates with boost controller off?

One thing I want to warn everyone about with the GTM kit and internal wastegates: If you want the option of running < 10psi and you aren't running a stock exhaust/cats, don't get them.

I made such a big deal about how theres no reason for externals and its a waste of money blah blah blah, now I feel like an idiot. Our engines flow a fuckton of air (technical term), the end result is that in 3rd-6th at 6k+ there is basically TOO much air flowing for the internal wastegate ports on the Garett turbos. I have the actuators at basically 0 preload, just enough tension on the flapper to keep them from rattling at idle, and I had boost creeping to 13psi at redline in higher gears.

You basically have 3 options for controlling boost creep when you have too much exhaust flow:

1.) run external wastegates, large wastegate opening flows more air, duh.
2.) port the internal wastegate housing, have to remove turbos
3.) restrict the exhaust flow (add backpressure)

I am working on option 3 right now, I have re-installed my old invidia gemini which is smaller diameter and more restrictive path than the aam 2.5". This reduced my creep from 13psi down to about 11psi, which is great but still not what I want. My next option is to either install high flow cats in place of test pipes, or install exhaust restrictors. An exhaust restrictor is basically just a metal plate you install in place of a gasket that has a smaller diameter opening.

If I was made aware of this issue when purchasing, which I wasn't, I would have gladly just went with external wastegates and recircd. I am not blaming GTM for this issue, but this is something they ABSOLUTELY should make clear when people purchase the internal wastegates.

I have heard of the boost creep problem with the stage 1. When I was ordering my kit, Sam recommended that I go with stage 2 due to the high exhaust volume of the vq37 engine. Any particular reason you went with stage 1? I would have expected Sam to warn you about this.

Quote:

Originally Posted by modme (Post 1718326)

Sam was surprised that he didn't warn me about it, but I can assure you as I did him, he said nothing. If he would have made even the slightest hint at boost creep I would have went external wg or stage 2 since the larger .86 AR helps mitigate this. My plan all along was to run no more than 8psi daily, and 10-12psi high boost with controller on.

Anyway whats done is done, I believe I can get down to 8-9psi max by adding a bit more back pressure. I just want everyone to be aware of the potential boost creep issues when making their decision.

Edit: I also want to point out that Sam even offered to swap exhaust housings for me to the .86 ar (stage 2) for free. I really appreciated this but after all the work I simply cannot pull these turbos off the car right now.

Very nice man. Glad to hear you're not having any issues. Seems a lot of folks have all kinds of problems after installing FI on these cars. Guess it's all in the tune or ?

Quote:

Originally Posted by Speedy (Post 1718744)

Very nice man. Glad to hear you're not having any issues. Seems a lot of folks have all kinds of problems after installing FI on these cars. Guess it's all in the tune or ?

Assuming you dont mess up the install, It's pretty much all about the tune. Sam has this nailed down.

I have the Stage 1 GTM TT and opted to go with external gates. I still get about 1 psi over the EBC setting, but does not creep above that. I set the lower setting to 6 psi and it gets me about 7-7.5 psi. High setting is at 10 psi and it ends up hitting 11-11.5 psi. This is with the gain set at 100 - If I turn down the gain, it gets even closer to the actual setting, but it loses alot of TQ early in the curve...

Quote:

Originally Posted by Greedy (Post 1719400)

yeah the externals have a bigger path for the exhaust gasses to flow. what exhaust do you have? I would advise anyone going with stage 1 turbos to only get the external wastegates for better low boost control.

I'm looking to have a machine shop fabricate some exhaust restrictors instead of going with HFC, hopefully that will keep me under 9psi with the controller off.

I have the GTM 3 inch. More back pressure should help for sure, and I think the restrictors are the way to go, they don't have the same potential of failing or melting like the HFC's. Would be cool to have a modular section of exhaust that you can take out and change the amount of restriction (different baffles / perforated stainless disks etc..) so you can get it dialed in perfectly. - Hope it all works out.