dmhenderson's Nismo '12 GTM supercharged build thread where I freak out a lot

[Baer383]

Originally Posted by carlitos_370z

sound like a fuel cut or like Baer383 said!!!

Throttle cut is always first followed by fuel cut followed by fuel restore in that order.

[Sh0velMan]

Originally Posted by dmhenderson

Odd behavior (and this may just be me not knowing boosted cars):
Pulling hard in 2nd and got a little too close to redline and near peak I had a sudden and almost complete loss of power. Shifted into 3rd and was fine. What gives?


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If you have not disabled ETC in your ROM, this is throttle cut. Completely normal. It literally closes the throttles on you.

If you disable ETC it can only cut fuel, which is a slightly less safe way to limit RPM, especially if you're boosted. (Ideally you'd cut fuel and spark, but cutting spark results in backfiring and emissions-conscious automakers won't blow fuel out of the engine no matter what.)

I have ETC disabled so fuel cut is all I have, and for me, it's fine. It's a lot less abrupt than throttle control, but can cause the engine to stumble when you get back into the throttle, if you're really beating on it.

[Sh0velMan]

Originally Posted by Baer383

Throttle cut is always first followed by fuel cut followed by fuel restore in that order.

This is correct.

Fuel restore is generally a lower RPM than the fuel cut (rather than the same RPM). If your ETC is enabled, you shouldn't really hit fuel cut in normal circumstances, at least N/A. I suppose you could have so much boost in the pipes that revs could continue to climb after the throttles begin to close, under low loads (1-2 gear).

[Baer383]

Originally Posted by Sh0velMan

This is correct.

Fuel restore is generally a lower RPM than the fuel cut (rather than the same RPM). If your ETC is enabled, you shouldn't really hit fuel cut in normal circumstances, at least N/A. I suppose you could have so much boost in the pipes that revs could continue to climb after the throttles begin to close, under low loads (1-2 gear).

It is on,he is running Sam's tune.

[dmhenderson]

Learned something new today. Thanks!


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[dmhenderson]

Update on tune: With the cats off it and the ART pipes on, before even starting to tune the car we are at 470whp. Lesson we've learned here: Superchargers do not like cats.

Whoever bet I was going to lose power with those pipes owes me a beer.

[Baer383]

I have 516 rwhp with stock cats on.

[carlitos_370z]

great to hear that my friend!!!

[dmhenderson]

Cats on: 450whp (no tune)
Cats off: 470whp (no tune)

I'm not trying to beat your dyno number, I am only interested in gains. This might be useful info for someone else on down the line.

[Baer383]

The cats keep back pressure and with the VVEL in these cars the back pressure will help with cylinder fill,I put Berk HFC on and lost 35 rwhp.

[dmhenderson]

Definitely strange. You'd think pipes would cause more of a loss but they didn't. Same dyno, same tuner so it's definitely a legit gain.

[Chuck33079]

So how much fun have you been having with it since you've gotten it back? It's amazing how well these motors take to boost. And the chassis handles the power like it was meant to have it.

[theDreamer]

Originally Posted by Baer383

The cats keep back pressure and with the VVEL in these cars the back pressure will help with cylinder fill,I put Berk HFC on and lost 35 rwhp.

I wonder if it is since he is just running the GTM canned tune, and it is fairly tamed overall, that just opening it gives some extra HP.

[jpritche]

Originally Posted by theDreamer

I wonder if it is since he is just running the GTM canned tune, and it is fairly tamed overall, that just opening it gives some extra HP.

My thought process exactly.

[dmhenderson]

I'll have final numbers once they get in there with the Uprev software tomorrow morning. Dropped off the GT-R spark plugs earlier this evening.