RB25 pulleys

[Zman]

how much can you get sr20 (s14a) pulleys for?

[T0nyGTSt]

Hey, my pulleys are out of the engine as it is.

Anyone got a contact in Sydney???

T.

[R31Nismoid]

Sweet as... GTS-t VSPEC... dont forget!!!!

lol!

also, if you can see just how much weight they can save it would be super!

[rev210]

The goal is to get 4 kilo's off the whole pulley setup I reckon.

T0nyGTSt,

can you weigh the front pulley mate?

[T0nyGTSt]

Originally posted by rev210

The goal is to get 4 kilo's off the whole pulley setup I reckon.

T0nyGTSt,

can you weigh the front pulley mate?

Ok I'll see what I can do tonite.

T.

[GTS-t VSPEC]

I was speaking to Steve at SST, he said that the main pully might be hard to change as it will affect the hramonics of the crank. Any ideas?

[rev210]

yes it will effect the harmonics of the crank, in much the same way as the flywheel does.It will be greatly offset in magnitude due to the great reduction in inertia hence the vibrational force is far less significant.

There seems to be two schools of thought on the harmonic balancer issure, one is to increase the dampening through the front pulley and thus increase the weight of the pulley. And the other is to lighten it dramatically to reduce the magnitude of force any vibration may have, both systems also rely on reducing the diameter of the front pulley in both cases reducing the 'outer' rotational mass and hence reducing the inertia.

The factory harmonic balancer on the RB26dett was found to produce a harmonic imbalance under extreeme racing conditions when it was in group A racing. They had to change the balancer for a custom made unit to fix engine failure problems.

Having said that, there are many present day R32's in circuit racing who have not changed those same factory balancers resposible for the group A dramas.

The V configuration engines suffer from harmonic issues to a greater extent and even the VG30's can be run safely with light weight front pulleys from what I have heard.

I'd put a light weight front pulley on without batting an eyelid. Having done so to quite a few engines thus far without issue.

[GTS-t VSPEC]

Dave, Seems reasonable to me. I'll ask the guys at Rotomotion as they do pulleys for the race cars, see what they think.

[R31Nismoid]

Also see what they think of the balancer issue?

maybe they have their own thoughts?

good info guys

[Steve]

Paul, dont forget!

[rev210]

Paul ,

Don't forget.

[GTS-t VSPEC]

Whoops, completely slipped my mind, will try and get up there this arvo:D

[rev210]

paul,

dont forget.

[benm]

Whats the difference between what you guys are talking about here and Ex Cam Gears (Pulley) ?

/hints at participation in a groupbuy.

[Ronin 09]

the pulleys are the things that the drive belts hang off at the front of the engine - they drive the AC/PS/Alt. The ex cam gears are the gears at the front of each cam that the timing (cam) belt spin to actuate the cams.

[sidewaymambo]

paul, how's going?

[Steve]

I do believe Paul is somewhere between Perth and Adeliade at the moment, looks like we're waiting a bit longer.

[Gradenko]

Paul, you've forgotten, haven't you?

[B-Man]

My engine in bits right now - keen to know what's doing with this .

Cheers,

[Simonster]

When I built my RB25 I used an alloy water pump pully to reduce weight and made it a few cm lager in diameter to reduce the possibility of cavitation.

Also used a custom flywheel as well, about 3kg lighter than standard. Although I'm yet engine run the engine as I'm waiting to source my turbo, I can't offer any benefits or downsides.

My thoughts would be to reduce weight of the flywheel, but reducing it too much, say greater than 4-5kg, will reduce the rotational mass too much for the street and torque off boost will be reduced. Can't say how by much but my engine builder said that any more than 5kg is pointless on a street car.