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WalkyHR31

RB30/25 Build Query

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Hi Guys, 

I currently run and HR31 with RB25DET making 270 RwKw. Had my engine builder do the bottom end and I did the rest. Great engine and been running it for last 6 years at the track and roll racing without any dramas. Runs 20 psi boost no problem and revs to 7500 RPM still making power. Spends a lot of time in the 5000-7500 range as I do a lot of track days etc. Rest of time just an odd w/e driver. Runs and R33 box and R200 LN diff with 3.7 gears.

However, time for more torque and KW as sick of getting blown away at RR by HSV's (S/c of course) and Datto 1200's etc!!

Have been planning an RB30/25 for some time now and finally went to my engine builder this week with all the parts to get started. He depressed me by telling me that the RB30 is not the engine to turbo due the high Rod:Bore ratio meaning it will sit too long at TDC and under high boost melt/break pistons etc. Says a 3.4 stroker will work Ok but not interested in that as too expensive and car won't handle it. Will be using good forged rods and pistons and crank collar..

Never heard of this being a problem before as there are heaps of these RB30 engines around making awesome power. This will be more a track engine than road so will see high RPM (max 7000). Looking at making around 330-350 Kw at the wheels at 20 psi. I am not a drifter and rarely hit the limiter.

So my query: is this Rod:Bore ratio a problem or not?  What has been other's experience with this combo using it for track work/roll racing etc?

Thanks guys. 

 

 

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Up till 5 months ago I would have said "no problem, go for it", but this was a stock RB30 piston from a 25/30 in a dedicated track car:20210203_125418.thumb.jpg.c9ad080245653b10499225f49ef744fb.jpg

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Thanks for that but 1. when you say stock I assume factory piston not forged and 2. what boost did this engine run? 3. Could this have been a tuning issue with a standard piston rather than the supposed Rod:Bore ratio problem? I suppose hard to know. 

 

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17 minutes ago, Ben C34 said:

Rod bore ratio is not a problem

Exactly, and this is what Rob from R.I.P.S  said about RB30 GTR's over ten years ago.

"I think the only guys who knock a 30 or genuinely prefer a 26 for a strong street car obviously have not been in a good RB30 GTR, there is just no comparison, we've proven 9000-10,000 is not only possible, but to date, has been 100% reliable (in a street/drag situation at least) the response is better, the driviblility is better, the slow cruise is better, the top end can be just as good, if not better, there really is no down side as far as I have found.

As far as rod/stroke ratio's go, it seems from the little I have looked into it, that the 26 is actually considered pretty poor and the Nissan RB30 is considered ideal.

Each to their own and I don't think there will ever be a 100% right or wrong, its just personal choice and you can't really blame a guy who has only ever been in big single turbo 26 GTRs for thinking its the "nuts", one day hopefully he'll experience a good all round RB and move up in cubes, one thing is for sure, I don't know of anyone who has had or been in a good 30 car and then said they prefered a similar spec 26.

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Thanks guys, appreciate your input but was hoping to hear from someone who may actually have an RB30 turbo engined track car that they could tell me what boost they run, rev limit they use and its reliability etc.

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1 hour ago, WalkyHR31 said:

Thanks guys, appreciate your input but was hoping to hear from someone who may actually have an RB30 turbo engined track car that they could tell me what boost they run, rev limit they use and its reliability etc.

Have you tried speaking to workshops that are building RB30's? Your like a 30 min drive from CRD, why not pop in and have a chat with the boys who are regularly building RB30 powered skylines?

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Thanks good idea. I'll call a couple including CRD. Didn't think they would be too keen to discuss if I am building not them!

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Well, they don't know you won't be building with them. Of course you're going to shop around before you choose someone to build your engine, right? 

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Motor still good?

Time for a proper twin scroll setup, twin gates (out the sides OR bonnet), nice modern turbo, big boost (none of this 1.4bar pussy shit).

20psi is g....y

 

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Yes that was option 1 but motor runs all stock gear - rods, oil pump, balancer, head, cams etc so wouldn't take too much more to reach breaking point! Anyway, already have 2 RB30 blocks, cranks, a head etc ready to go. 

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14 minutes ago, WalkyHR31 said:

Yes that was option 1 but motor runs all stock gear - rods, oil pump, balancer, head, cams etc so wouldn't take too much more to reach breaking point! Anyway, already have 2 RB30 blocks, cranks, a head etc ready to go. 

Stock RB25 with just headstuds only will do 350kW all day on E85 at the track.

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