Reliability at 400wrhp(310wrkw)

[Guest mmdb]

alright thanx guys. I'm going to look into the sr20det and see how much i can obtain from that engine without tearing apart the engine. I want to keep it the stock internals if i can.

[whatsisname]

One VERY BIG factor that needs to be considered is the health of the internals BEFORE turning up the wick. A motor that's had a hard 100k before it gets into your hands may well fail at 250rwkw. A fresher motor might hold on 30-40k or even longer?

How many kays does the motor REALLY have on it when you get the car?

My motor was putting out over 200+rwkw for 2+yrs (not many kays travelled though) I REALLY looked after the engine too (the whole car in fact). I'd say that the engine would have lasted quite a bit longer with a more mild turn. And slightly less power.

My motor cracked a ringland on #6. Not an uncommon point of failure in the RB25DET.

[StraightSix]

re: thick headgaskets . . . another consideration is that the squish areas around the edge of the combustion chamber are a great help in preventing detonation. With a thicker headgasket you basically eliminate those squish areas.

J

[Steve]

StraightSix, although the squish zone is changed, it would be aruable that it is eliminated, only increased. It may not be as effective as the stock setup, but this is more than compensated for by the reduction in CR - this is evident by the many 300rwkw RB25s being built in Japan, with stock internals. Even Ben Ellis, who is doing a RB25 build in HPI magazine is following this philosophy. He has spent a large amount of time in Japan around performance cars, so if it were that detrimental, would he still be doing it?

[Sydneykid]

Hi drift_me_silly, you priced this stuff yet? Let me have a go....

-new r33 gtr crank

$1400

-custom je forged pistons

$1800

-carillo rods

$2200

-nizpro crank girdle

$3000

-electric w/pump

$400

-cryo treatment of internals/block & head

$300

That's $9,100 without any labour or top end work. Shoot I could build an RB31 bottom end for way less than that. In fact a complete RB30/RB25 hybrid would be cheaper.

Hope that adds to the discussion

[Xeron]

The quench debate is very valid. Theoreticly you want your quench distance (the height of the compressed head gasket plus the distance the piston is down the bore at TDC) to be no more than say, .055 inches, preferably closer to .045, although this depends on your setup and i'd ask someone knowledgable, dont want valves to be hitting pistons now do we. Quench does make a BIG difference to detonation, its vital in a good engine build.

The best way to lower compression is not through a thick head gasket, but rather getting a dished piston really.

[StraightSix]

Originally posted by Steve

StraightSix, although the squish zone is changed, it would be aruable that it is eliminated, only increased.  It may not be as effective as the stock setup, but this is more than compensated for by the reduction in CR - this is evident by the many 300rwkw RB25s being built in Japan, with stock internals.  Even Ben Ellis, who is doing a RB25 build in HPI magazine is following this philosophy.  He has spent a large amount of time in Japan around performance cars, so if it were that detrimental, would he still be doing it?

It is true that the reduction in compression ratio more than makes up for the loss in squish. However using dished pistons and keeping the squish would allow you to run a slightly higher CR thus improving low-end response.

J

[Cool Hand Luke]

Was it not in zoom they had a turbo comparison on an RB25 which was "internally standard". Although it did have a different plenumn on it, the power was something like 306rwkw. The guy who i bought my car off is building a RB25 180, at 4000rpm it had 240rwhp. I dont know an overall power figure but it had std manifold and internals.

I think not only is it a major factor as how old the engine is, but also the tuning of it. With poor tuning a standard engine will blow up, so to say that because one blew up with 400hp at the flywheel doesnt mean that thats the limit of an RB25. Many people i have talked to on the coast have said that the limits (with correct tuning and as long as the internals are fine, with all the correct parts ie injectors, turbos) for the RB25 is a bit over 300rwkw, with the RB20 being around 250rwkw.

[Steve]

Originally posted by StraightSix

..... slightly higher CR thus improving low-end response.

J

boost and higher CR generally dont mix, loosing a bit of bottom end, well if you are running 300rwkw, you wont have a great bottom end, and nor should you expect one with a 2.5L engine. But at least with RB25 you have the VCT which compensates, which the RB26 doesnt have.

Its always a trade, top end, bottom end or midrange.