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When Is A Stock R34Gtr Fully Spooled

Nismo 3.2ish

By Nismo 3.2ish,
in Engines & Forced Induction

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GTSBoy Grand Master

GTSBoy

Posted
Posted

But seriously......how long is this piece of string that you're trying to measure? Are we in 1st gear? 3rd? 5th? Uphill? Downhill?

As to the 4.9 sec 0-100 time......of course it's with a decent launch. A high rpm launch? Depends on what you cal high rpm. But realistically, on any given surface, there's only really one correct rpm to launch at, and it's not necessarily "high". ~4500rpm side stepping the clutch will get you moving fairly briskly, but the turbos won't be "fully spooled" at those revs before you let the clutch out. But they sure as hell would be if you were driving uphill in 4th.

Nismo 3.2ish Grand Master

Nismo 3.2ish

Posted
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Posted

That was my question, when are they " fully spooled." from a standing start and you say they are not fully spooled at 4500rpm in 1st. I thought they would be going hard at 4000rpm with smallish twins?

I was not really interested it those times but they were pretty quick in 1999, even now.

GTSBoy Grand Master

GTSBoy

Posted
Posted

That was my question, when are they " fully spooled." from a standing start and you say they are not fully spooled at 4500rpm in 1st. I thought they would be going hard at 4000rpm with smallish twins?

I was not really interested it those times but they were pretty quick in 1999, even now.

I didn't say "in first". Nobody launches "in first". Everybody launches with the clutch in. Ergo, the likelihood that the turbos are fully spooled up at 4000rpm BEFORE you let the clutch out and load the engine is pretty slim. The turbos will then go on to make boost once the load is applied, but you can bet your last 50c that you get full boost later (in terms of rpm) on a 1st gear launch than you would if you did a rolling start in 1st at say 1500rpm.

That's why I took the position I did on answering your question. You failed to specify exactly what you were asking about.

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Piggaz Grand Master

Piggaz

Posted
Posted

Well each gear, peak boost will be reached at different rpm due to load, will it not?

And farken "full boost". Unless it has some sort of reference to it (eg 25 psi), it's the most meaningless thing ever. Are we talking 5 psi or 55 psi?

Nismo 3.2ish Grand Master

Nismo 3.2ish

Posted
  • Author
Posted

Oh, I'm going off a controlled environment. Dyno.

This is still silly though. I think this is a school holiday question.

Just asked when a stock R34GTR would be fully spooled from a standing start, not launched at 4500 or 8000rpm, just let the clutch out and put your foot down.

Hadouken did something strange, he just gave me the answer, going at 4k , thanks Mate

Back to school now :)

Nismo 3.2ish Grand Master

Nismo 3.2ish

Posted
  • Author
Posted

Well each gear, peak boost will be reached at different rpm due to load, will it not?

And farken "full boost". Unless it has some sort of reference to it (eg 25 psi), it's the most meaningless thing ever. Are we talking 5 psi or 55 psi?

Whatever a stock standard R34GTR is, doubt if many are 5 or 55psi, you sure do swear a lot Mr Piggaz :))

Kinkstaah Grand Master

Kinkstaah

Posted
Posted

Before my engine met its fourth untimely demise, I was going to ask a boost related query.

Mind you this is a 4 speed auto that's been built a lot.

1st gear would see 22psi at about 4k and bleed off to about 21.

2nd gear would see 25psi and then bleed off to about 24.

3rd gear would see 29 psi and bleed off to about 25.

4th gear (lol) would see 30psi and crack the wastegate which is what the boost controller was set to.

There were no boost leaks in the system that were obvious. There were concerns about the FMIC not liking it and maybe not flowing boost through, but it certainly made no audible sound when an air compressor was attached to the intake.

On the dyno, it made 30PSI at about 3200 RPM, in 3rd gear. The on-road experience was different.

Is this load related? The vibe I always got was that "boost is later with less load" which makes sense, but I also got that it was a few RPM difference between first gear and top gear, not multiple PSI.

Just curious to hear what others experience in 'the real world'

GTSBoy Grand Master

GTSBoy

Posted
Posted (edited)

The general rule is exactly as you say. Higher gears mean slower ramp rates on the road, giving more time to get the gas flow up and so you make boost at lower rpm. 1st gear in particular, the ramp rate is so fast that the engine will happily accelarate through the revs faster than the turbo can spool up to give you boost. If the system is all well balanced then you get the above characteristic.

If you have a turbo with a small hot side that restricts flow, then you can actually find that you don't make more total boost in the high gears. It might still have a lower boost threshold and reach full boost earlier in those higher gears, but it might not reach the same peak boost as maybe it will in 2nd, and it may tail off more. My car with std Neo turbo tends to do that although I must admit that I haven't spent a lot of time trying to tune the gain on the boost controller to dial it out. The number of times I can usefully load the car up in high gears for long enough to be bothered by not making enough boost there are too few to cry over these days. Well, actually, the lack of such opportunities is something to cry over.

Edited by GTSBoy

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