Flywheel question

[Warpspeed]

Does anyone know if the RB25 and RB26 flywheels are the same or interchangable. Also what are they made from, grey iron (unlikely), nodular iron, or steel ? Are the RB25 and RB26 pressure plates similar and/or interchangable?

[MegaGTS4]

I have read somewhere(on the net) that the NISSAN RB20DET/RB25DE/RB25DET/RB26DETT are interchangeable(this is backed up by the fact that the JUN flywheels for these engines are the same part number!) and the factory ones are made from cast!(don't know what grade steel?)

Some aftermarket ones are made from forged Chrome-molybdenum steel!(and some are even made from Aluminum!!)

but I'am not quite sure about the pressure plate though because they would probably have different clamp pressures! But the pressure plate(standard) is made of Nodular iron!!

MEGA

P.s but don't trust me because I drive an auto!!!(will be manual very soon! :uh-huh: )

[Warpspeed]

Thanks Mega. I am new to skylines and still have a lot to learn. My thoughts are that a bog stock RB25DE may have a nasty flywheel, where an RB26DETT may have something far better that is not going to go out through the windscreen at 8000RPM.

As you say, the RB motors probably all have a similar sized flywheel, but the quality of material may vary.

I have actually seen a cast grey iron flywheel split in two when accidently dropped onto concrete (woops !)

Am planning to put an RB26 crank and rods into a GTS-4, and am just wondering if the stock flywheel is up to the job.

[MegaGTS4]

Didn't think that you could use RB26 crank in a RB25?

(maybe I don't know? :confused: )

RB25DE

Bore x Stroke (mm) 86.0 x 71.7

RB26DETT

Bore x Stroke (mm) 86.0 x 73.7

Might work but to what benefit? I have seen RB26 heads on RB25s and a few RB26 heads on RB30s and even RB25 head on a RB30 but none used internal parts from the RB26!!

this is a site showing the benefits of such a head convesion!(RB25 head on RB30 block)

http://www.autospeed.com/A_0004/article.html

MEGA

[Warpspeed]

RB25, RB26, and RB30 all have 86mm bore. It is the RB20 that has the smaller bore. I also understand that the 4WD blocks are different from the "normal"blocks in that the pan rails are wider apart for the special sump.

The RB26 crank is far heavier and more sturdy, it is also fully counterweighted, in other words there are two counterweights one on either side of every conrod. The RB25 crank is less strong and rather crude in comparison. Still a bloody stong crank though !

I also need to lower the RB25DE compression from 10.5 down to 8.5 (guess why). By putting all the RB26DETT stuff into an RB25 block I get to keep the same engine number (hee hee) and no one will ever know. I just want to make sure the flywheel is not going to be the weak link. It iwill all be going into a 33GTS-4.

[rev210]

The factory cast iron flywheels are around 9/10 odd kg!

The RB26/30/25 flywheels are NOT interchangable.

Do not machine the stock cast iron one to decrease weight it is not safe.

[Warpspeed]

Safety is the uppermost thing in my mind, and the reason for this thread. It looks like either a stock RB26DETT flywheel then, or one of the standard weight steel aftermarket ones.

Thanks heaps REV210, that is the information I am after.

[rev210]

Originally posted by Warpspeed

Safety is the uppermost thing in my mind, and the reason for this thread. It looks like either a stock RB26DETT flywheel then, or one of the standard weight steel aftermarket ones.

Thanks heaps REV210, that is the information I am after.

The aftermarket ones are the way to go. They can be as light as 4 or 5 kgs, faster reving/boost and less strain on the gearbox are benifits.Ogura make a fairly cheap one from chrome-molly.

[Warpspeed]

Thanks, I will check out Ogura.

[Cubes]

I've got a chrome molly flywheel and straight away i noticed it was actually a hell of a lot easier to get moving.

When the crank/cam belt was out one tooth it was very gutlless off boost.

It is also a lot easier to rev' match gearing down and can be done a lot quicker..

[Warpspeed]

Hi Joel. Originally I was thinking only to get a standard weight steel flywheel that would take a bit of a rev without exploding.

However, rev210 and yourself have now got me thinking a bit about flywheel weight.

With 4WD turbo cars the BIG problem is getting the car moving from a standstill, with a larger than stock turbo and decent cams, this only becomes worse. Launching the car at a million revs is a bit hard on the driveline ! I do not think a squirt of nitrous is really a practical solution on an everyday streetcar, although it certainly does work.

I am planning something a bit different. A supercharged GTS-4, designed to have a large amount of torque over a wide rev range. A light flywheel is going to make a lot of difference in first gear, and I will not have to launch the car.

I agree with what you say about rev matching and faster engine response. The GTR six throttle body setup is also a step in the right direction for fast throttle response as well.

Hmmmmmmmmm interesting.