Spool time?

[summoner]

Mate runs a GT30R with 45mm external gate on his SR20DET.. goes hard etc.. he's going to be selling the turbo+gate soon so tempted to buy it and am wondering roughtly where abouts it will spool up on an RB20.. being oversquare as oposed to SR's square setup will effect this i'm guessing.

Would it spool by 4/4.5? or would i need cams to get it to even start by then?(btw yes turbo is a ball bearing unit)

[adam 32]

well pauls turbo spools at 4K on an RB25 with a tubular manifold, so id predict 45-4800

[Chef_32]

could be a bit big, but if you're planning for internal mods, could work out nicely.

[RS500]

summoner,

it would depend on which GT30 core it is and what A/R exhaust housing he is using.

[Steve]

..... and what exhaust mods, adj cam gear AND what exactly do you mean by spool? Its a bit vague. Do you mean starts to make boost? Makes 10lbs, makes 14lbs etc.

HKS GT30 with 0.61 turbing housing and 84 trim exhaust wheel on my RB25 made around 1 bar at around 3krpm, the interesting thing is that once it gets to around 8lbs the turbo spools very quickly, so quickly that from 8lbs to 14.5 is only a couple of hundred rpm, to 1.2bar isnt alot more, but I also have a tuned length ceramic coated manifold, but my exhaust is pretty restrictive (quiet).

Lots of buts.

[summoner]

ok by spool i meant Max boost.

by exhaust, dump pipe, front pipe, 3.5" exhaust

eitherway i was basing these questions ona stock engine wise setup, eg cams etc.

[Steve]

And full boost is?

and what size turbine housing?

I think realistically, with stock manifold, the best you could expect would be 14lbs by around 4-4.5krpm, but it really does depend alot on the turbine housing size - ie fit the smallest you can whilst not getting too much back pressure, or causing compressor surge.

This unfortuneately is usually accomplised by trial and error.

That is quite a large turbo for a 2L

[summoner]

yeh.. works fine on mates SR by 4000 at 1.4bar..

i was thinking run 1.2bar for now then when rebuild engine run more

overall if it comes on by 4,500 rpm im not fussed as it revs to 8000rpm nicely as it is and so far seems the stocko doesnt really come on till 3,500-4000

[WazR32GTSt]

if you get the head ported (the exhaust side) when you rebuild the engine then will that help?

[Steve]

It could help, depending on the back pressure being generated by the turbine and manifold and of course the rest of the exhaust system.

Most Jap engines' heads of late seem to flow around 95% efficiency from what I have read, so the benefits would be minimal. More to be had from cams and timing. Once again though if you increase overlap, it may rob you of power if you have excessive back pressure causing exhaust gas to revert in to the cylinders.

No substitute for a well flowing manifold and a correctly matched turbine housing, front pipe, cat and cat back.

I have just purchased a 0.87 turbine housing for my turbo, I expect boost to be a few hundred rpm later, but should pull alot harder. Less back pressure also means you can run more adv timing. Once the cams go in, and adj exh cam wheel, it should bring boost on earlier by 300+rpm, so the effect of the larger housing will be negated from that point, just give me better top end:)