NISMO heads for the VG30E/ET

And then there is my dyno that is always discounted because it was a turbo with the wastegate wired open. I had a standalone and map sensor confirming no positive pressure in the manifold. 9.0:1, custom grind cams, very aggressive ignition timing. Sure looks like a NA map to me, but not trying to steal any best NA HP thunder. Made around 400whp at 12psi, don't thing the dyno was overly optimistic seeing as how 440cc injectors were at about 95% duty cycle with bumped up fuel pressure.

What you refuse to understand that even if its not making boost pressure, the compressor wheel is still spinning which means it is still moving more air through it than a 9:1 VG would NA. You don't need boost for a turbo to be working. For example, on my T3/T4 setup…even partial throttle with no boost building it was still quicker than a NA with a intake/exhaust....and it was stock cams etc. The ONLY reason it was quicker is because the turbo was still moving air, even without boost being made.

Even with the w/g wide open it can not negate all of the air produced by the turbo....

Just to clarify. As some people may not be familiar.

A performance oriented car should run about 1" hg below atmospheric pressure at WOT and can be as little as .5" hg.

While we normally don't express a vacuum in PSI, 1" hg = ~ .5psi

So a theoretical car with a turbo "boosting" over NA levels while remaining under atmospheric conditions would provide around .5psi "boost" at best.

I did many dyno runs tuning that engine and in all cases from 7psi and up it gained on average 12HP per pound of boost.

Trying to say this theoretical half pound of boost provided anything more than 10HP would be a very large stretch. Many sportbikes have ram air intakes that achieve positive air box pressures at speed that only account for a few HP.

Futhermore, plot this condition on a compressor map. A 57 trim T4 flowing, what, somewhere in the range of 20-30 lbs/min at .5 psi "boost" or 1.034 pressure ratio. You can infer this would be way outside anything remotely efficient if even possible.

It is highly unlikely. It is more likely that it is a restriction. That is all I have to say on the subject. If the tube frame Z ever gets finished, I will gladly dyno my next motor with turbo completely disconnected. I did just pick up some supra spindles to get started on my SLA front suspension.

The only thing highly unlikely is a NA VG30 making anywhere near 230whp with this: " 9.0:1, custom grind cams, very aggressive ignition timing." and stock log exhaust manifolds. It did so because of the turbo moving air, and NOTHING else.

A 9:1 VG30 with better cams, advanced timing and HEADERS will be lucky to do ~200whp.

i will confirm that now with my much larger turbo (60mm) on my vg33et, the car is NOTICEABLY more "peppy" even at partial throttle with the boost gauge just before the "0" line between vac and pressure.

not taking anyones side, you guys can battle it out here… but since this is about who experiences what, this is what i've noticed with my new turbo, no boost pressure. i would agree that it does get air fed to it at an accelerated rate, but probably not at any considerable pressure.

it seems almost like a helper fan for an HVAC system that needs to send air to a second or third floor from the corner of the basement.

This is a fantastic thread. Can't believe someone is finally using a set of those heads. Just thought I should throw a few things in. These are from reading my copy of John Starkey's book on the GTP nissan's. http://www.amazon.com/Lightning-Speed-N … 0970325940
1. IMSA GTP engines always used production cylinder heads.
2. The production blocks held up fairly well AT FIRST, but they tended to develop cracks from the strain of endurance racing; hence the beefy girdle addition and eventual redesign to use an entirely different block.


He pretty much refuted exactly what you said in your reply…

Plus, 'Advanced timing' vs a speed-density full standalone fuel system? 'Better cams' vs LOPE CITY??? UMMMMMM....

Back up for a second and look at the shape of the dyno graph. If he claims no delta pressure between the intake and atmo, that's believable. Claiming a gain of more than say 6-10whp purely from pumping losses is unreasonable IMO. Knowing his crazy big cams, intake, ported heads and then comparing his dyno graph to the other NA graphs… Note there is only substantially more power at high RPM (really the divergence is 5500RPM+). There are too many variables to consider (or even list) here to really say anything for sure; he seems to have made impressive numbers at 'no boost' with no bottom end work. I was impressed way back when he posted this the first time, like 8 years ago?

Production taken over by mecachrome which was a renault racing affiliate of some kind and eventually folded into nissan… maybe this is when nissan and renault started their relationship, eventually leading to merger?

What I think you're feeling is something that happens with proper intake tuning vs. average plumbing

I've made many iterations of intakes for non-turbo cars I've owned, and while I guarantee none went positive pressure by more than a fraction even at speed, there were very obvious characteristics I can only attribute to the air's momentum, there is a small power gain on the ramp up if you do it right

Normally the air is trying to "catch up" when you go WOT, and stays in vacuum until the air gets used to cramming in and the engine no longer pumps air out faster than air wants to come in, once that happens the power is what we might call ideal

It's like turning on a vacuum cleaner in a vacuum then opening air supply, but instead of allowing the air to just equalize, ramp up the vacuuming… the only thing I see the free spinning turbo doing is accelerating the intake scavenging so as to not fall as far behind, but this would never show on a dyno, best it could do is change the curve a little below peak torque

This is odd, did you re-read the section that had that information recently?

I know that the SCCA GT-1 car that Paul Newman drove had production cylinder heads.
I've also seen a particular video of a GTP-ZX that has a production cylinder head valve cover.
But then I've seen pictures of a desert racer that has a direct swap from a GTP-ZX turbo that has the elongated exhaust ports casted onto the head; a tell-tale nismo feature, no?

i'm almost convinced they switched head as well as blocks at some point.

a227700, how did you run the distributor? did they supply one with the head? its driven off the rear of the driver side cam, isn't it?

It's possible that another type of head was made outside the factory racing efforts, surely someone thought the vg was worth a little extra development?

When you spend millions per race, casting and machining a new head is lunch money

EDIT: also remember the 300zx ran GT and prototype classes.. prototypes are wide open for mods

I love it when you get butt hurt.

I have better things to do than argue about an engine I built years ago. Take it for what you want. But please don't slap logic in the face with electric supercharger theories. I have one in my computer here I will sell you, good for 20HP. It takes pressure ratio to make any significant gains. At least have the decency to tell me you think my MAP sensor was off or call my liar.

[quote]G-E wrote: but the heads i've seen have the same exhaust port flange/deck as the nismo ones, so that leads me to believe nissan was involved in implementing them on GTP-ZX engines.

Maybe that was a pic of the vg30de prototype… we know othey used the sohc engines in the z32 imsa cars as they were already proven, but the mid4 were being developed with what became the 300zr engine at the same time

For all we know nissan might have done test races with the dohc version

[quote]Tempestas wrote: Whatever guy. You had a basically stock NA engine other than cams, with crappy stock log manifolds and stock compression and you want people to believe you made more power than any of the full-on NA builds? Its bullshit and you know it. I'm not butt hurt at all because I don't give two shits about NA VG30Es, they're slow as hell and always will be. I think you're the one who is butthurt because he got called out on the fact that if your car hadnt had a turbo on it, it would not have made 230whp.