Cam Choice For A Track Orientated R32

[«Cyph3r»]

Hi all,

Just having a bit of a discussion with a mate atm who is having trouble deciding what size cams to use in his current engine build.

Basic rundown of specs:

Tomei RB28

HKS GT-RS

1mm Oversize valves

CNC porting of head

He is intending on using the car primarily for track days at QR and Lakeside, with the odd hillclimb included.

Trying to decide between:

Tomei 270deg in/ex 10.2mm lift

Tomei 270deg in/ex 10.8mm lift

Tomei 280deg in/ex 10.8mm lift

Tomei 280deg in/ex 11.5mm lift

He is aware that the GT-RS would probably be better replaced by some -5's for response, but they were on the car when purchased and can be changed relatively easily down the track if the 2.8L capacity doesn't help enough.

Another thing that should probably be noted is that the car is a gts-t, so the less peaky the power delivery is the better.

Peak power is not the goal for the build, but in saying that, the owner does not want to have a car that feels "flat" in the top end.

Any advice would be greatly appreciated.

[«Cyph3r»]

hmmmm......

decided to go with 270deg 10.8mm lift.

[Beer Baron]

I would have maybe gone the 270in and the 280ex. both 10.8

[Swiper the Fox]

I would have maybe gone the 270in and the 280ex. both 10.8

yeah...the RS's love big cams...esp. with big valves and headwork...it actually improves response.

[Piggaz]

Sure you didnt flog the motor out of my car?

Im running 270's at 10.25

[T04GTR]

what differances were noticed when upgrading?

[9krpm]

I would have maybe gone the 270in and the 280ex. both 10.8

Rich, have you got any dyno result of the gain with the bigger cam in the exhaust compare to a square setup?

[XRATED]

Rich, have you got any dyno result of the gain with the bigger cam in the exhaust compare to a square setup?

I'm planning to use a set of 260deg pon cams initially, then change to a set of 270 10.5mm. The head has 1mm OS valves, springs/retainers, port work and tomei buckets.

I will be running down the road of a stroker with low mounts. If anyone has them, I'd love to see the reults of different cam/turbo combinations.

Cheers

Justin

[Piggaz]

Dyno sheet

Spec is

GT block

Tomei 2.8

9.0:1 compression

270 @ 10.25 in and out

ported head

GT RS's

BP ultimate.

I will go on to say that when I had that tune done my coils were shagged. I have a new set to go in... yet to be put in and thrown back on the dyno. Those results were at 21 PSI

[9krpm]

Rich, have you got any dyno result of the gain with the bigger cam in the exhaust compare to a square setup?

Any one?

It make sense to have a smaller cam on the intake side to help cylinder fill and improve low to midrange response, which is crucial for trackwork. What I am keen to see is some hard evidence, hopefully on the same engine, of the gain of using smaller cams rather larger cam and advance the larger cam with cam gear.

I am still in the process of finding the sweet spot for my 272 cams. IMHO you don't want to go any larger than 272 on the exhaust side for a track car.

[bradsm87]

hmmmm......

decided to go with 270deg 10.8mm lift.

Good move. That's wat I woulda said

[bradsm87]

I would have maybe gone the 270in and the 280ex. both 10.8

Why go bigger ex cam on a turbo setup that is limited by the turbine flow? The GT-RS turbine chokes up before the compressor runs out of puff.

[«Cyph3r»]

Dyno sheet

Spec is

GT block

Tomei 2.8

9.0:1 compression

270 @ 10.25 in and out

ported head

GT RS's

BP ultimate.

I will go on to say that when I had that tune done my coils were shagged. I have a new set to go in... yet to be put in and thrown back on the dyno. Those results were at 21 PSI

Nice power curve..... haven't seen many builds with GT blocks!

I'd say my mate will be pretty happy if he can get similair figures to yours.

How extensive was the head porting you had done?

Thanks everyone for the input.

[Piggaz]

Nice power curve..... haven't seen many builds with GT blocks!

I'd say my mate will be pretty happy if he can get similair figures to yours.

How extensive was the head porting you had done?

Thanks everyone for the input.

I didnt build the engine. A mate of mine did when he owned it and I bought it off him soon after but from what he said i think it was decent. See how she goes with the new coils and some more boost shoved down her throat!

Edited September 29, 2009 by Piggaz

[9krpm]

copgaz, peak torque at 5+krpm is still laggy for some tight circuit.

You will then have to use lower gear to keep the rev up which then will tax the cooling system.

My setup with the Greddy T618 has peak torque at 4krpm and it still feels a tad laggy.

With a bit more work I think I will be able to bring that down to 3-3.5krpm....with top end compromise of course.

Edited September 29, 2009 by 9krpm