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Steps in power limitation of the RB25DET


WizardBlack

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EDIT: Let me rephrase for clarity (it's been a couple of long days.. heh).

If you continually bolt on things to make more power (turbo is required pretty early, so I hear. Beyond 10 psi IIRC?). When (horsepower-wise) do you start to break things or at least get into that zone when ppl in the know start to get real nervous? If you fix the first thing, what is next, etc.? This'd be a good sticky subject for ppl modding the RB so they know what to expect.

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RB25DET with Front mount and 3inch exhaust. Stock clutch 10PSI lasted about 6 months.... Then I put a 4 puck in and the solid differencial mount lasted about 1 month... Grade 3 bolt pulled apart, not snapped, pulled... Thats all I got so far.... Havent beat on her too much.

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Weak link in my experience is the piston ringlands. My bone stock motor made 500+hp for sometime, reliably. It wasn't until I pushed it over 600 rwhp on pump gas that I started breaking stuff and the ringland was the first to go (no need for a metal headgasket on a stock motor! lol)

 

JT

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with the little experience i have with high power RBs...from what ive read is the first thing that usually has issues is the ignition system around 300whp

 

Next is the RB20 trans (if you have one) around 400 whp

 

Ringlands around 550

 

and the 9 sec rb nearing comlpetion thread is testing the stock girdle and crank i believe up to around 1000....

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i hit 441 with just hg and studs + bolt ons on 100 octane

 

a friend of mine hit 500 with stock head/cams/and stock intake manifold on 35r@19psi. stock cams are good well to 600. but it does help bigger turbo's spool if u match ur cam correctly. stock pistons as jtaylor said should be fine in the high 500's. rb25 is a gangster ass motor for the price =]

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rb25 is a gangster ass motor for the price =]

 

Yeah, I am seeing that. I am surprised. I heard a little differently but I guess most of that is versus the monstrous RB26. It would put about any motor in a poor light, I guess.

What do you guys spin to reliably?

 

Summation:

Stock turbo to 10 psi

Pistons to 500

Headstuds to 500

rods to ???

 

Do you guys even do ARP rod bolts? Water pump or oil pump? I heard N1 pumps are actually slower (at the same rpm) to account for the extreme rpms of N1 applications. Or at least the water pump is.

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Yeah, I am seeing that. I am surprised. I heard a little differently but I guess most of that is versus the monstrous RB26. It would put about any motor in a poor light, I guess.

What do you guys spin to reliably?

 

Summation:

Stock turbo to 10 psi

Pistons to 500

Headstuds to 500

rods to ???

 

Do you guys even do ARP rod bolts? Water pump or oil pump? I heard N1 pumps are actually slower (at the same rpm) to account for the extreme rpms of N1 applications. Or at least the water pump is.

 

The water pump is, however the oil pump is not. The oil pump has a higher pressure. And apparently has a slightly weaker metal casing due to some metallurgy lab results, but to be honest, I think it's a waste of time even worrying about that. Some people have had RB26 N1 pumps go for years, some for days.

 

Same with stock pumps. Only way to be extra sure is to drop 1000 on a tomei or jun.

 

I'm going with N1 oil pump and standard water pump.

 

And for the price, ARP studs should be done at head-gasket change. it's just better in the long run.

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i haven't heard any problems out of the stock rods. i got duped into getting the n1 water pump rofl. so far no problems tho. i went new oe oil pump when i put this motor together. my redline's set to 7400, i hit it from time to time, but i try to shift at 7. stock rod bolts. aftermarket rods usually have arp studs in em. stock main bolts are fine too. i dunno the limits but i have peace of mind with my set up till i reach 550.....then i'm crossing my fingers lol.....i don't know what i'm gonna do if i break this r200 >_

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Next is the RB20 trans (if you have one) around 400 whp

Why would you get an RB25 and then use an RB20 trans? Piecing it together? I have the feeling that some shady sellers put an RB20 trans with the RB25 for unsuspecting buyers so they can sell the trans for more money or put it with an RB26.

I take it there are small ways to tell the difference between the two if you look carefully? I saw the the RB20 trans has strengthening ridges all around the bell housing all the way up to the mating surface whereas the RB25 has like three rows farther back and then some more up on the bell but not all the way around.

 

On a side note, it seems like the RB25 has a similar powerband to the SR20 with similar mods; just about 20% higher everywhere. Very interesting.

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There is an enormous difference between the 20 trans and the 25 externally. The size is very different. 25 tranny weighs enough to make me wish I had a trans jack.

 

RB20det trans is very close size wise to an L series 5 speed.

 

Evan

 

 

i must be a big brute then cause i know i have had no problems moving my trans around .

 

i guess i can see if the 20 is similar to the l series trans. i am putting mine in a Z31 so the size difference is pretty minimal

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There is an enormous difference between the 20 trans and the 25 externally. The size is very different. 25 tranny weighs enough to make me wish I had a trans jack.

 

RB20det trans is very close size wise to an L series 5 speed.

 

Evan

 

That's part of the reason why I want to go with an SR20 6 speed and RB20 bellhousing.

 

Lightweight, closer gear ratios, same flywheel/clutch.

 

That, and the weight savings of not having a forced induction system hanging off my motor should allow me to save a couple of hundred pounds, which should put me a hair under the factory weight when everything is said and done.

 

300 - 350 hp in a cruiser/light track-duty car should be fun with close gear ratios and 7600 rpm + :D

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That's part of the reason why I want to go with an SR20 6 speed and RB20 bellhousing.

 

Lightweight, closer gear ratios, same flywheel/clutch.

 

That, and the weight savings of not having a forced induction system hanging off my motor should allow me to save a couple of hundred pounds, which should put me a hair under the factory weight when everything is said and done.

 

300 - 350 hp in a cruiser/light track-duty car should be fun with close gear ratios and 7600 rpm + :D

 

shiiiiiiit. 1000 bucks for the 6 speed transmission.

 

meh. i guess i'll go with it and go with the FS5R30A if the 6 speed breaks. They cost the same price, but the weight/extra gear/close ratio gets me =)

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shiiiiiiit. 1000 bucks for the 6 speed transmission.

 

meh. i guess i'll go with it and go with the FS5R30A if the 6 speed breaks. They cost the same price, but the weight/extra gear/close ratio gets me =)

 

I heard the 6 speed is as weak as the 5 speed for the SR20's. No hard facts of course.

 

240zwannabe: That is absolutely not a threadjack. This is exactly what I was hoping to bring to the front. A good discussion of hard facts so we can determine when everything will need replaced. So far:

 

Turbo: 10 psi

Pistons: 500 whp

Head Studs: 500 whp

Rods:

Crank:

Block:

Mains:

 

What's the highest powered stock bottom end car (other than pistons if those are replaced)?

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