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Installing Cam Gears

mr_rbman

By mr_rbman,
in Engines & Forced Induction

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mr_rbman Grand Master

mr_rbman

Posted
Posted (edited)

got some cam gears for my 32 and i'm just checking that when installing them ready for tuning its best just to set them both to zero?

EDIT: I've just finished installing my adjustable cam gears and now the cars idle is extremely rough and eventually stalls, my ignition timing on my power fc is on about 20? Don't have a timing light so can't check it that way!

Anyone got any ideas what it could be? I made sure the harmonic balancer lines were at tdc aswell as having both the cam gears at 0 (figured i'd let my tuner play around with whats best)

PLEASE HELP!!!!

Edited by mr_rbman
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The Dan Grand Master

The Dan

Posted
Posted
got some cam gears for my 32 and i'm just checking that when installing them ready for tuning its best just to set them both to zero?

Set them both to zero and dial them in on the dyno when you take it in for a tune.

If it's a 20, the inlet will most likely stay at zero and the exhaust will probably be changed to 2 degrees retarded but leave it up to the tuner to set it properly.

Cubes Grand Master

Cubes

Posted
Posted

Definitely some tweaking to do ash.

Drop Andrew a line and see what he set his up at.

All though he was running RB20DET cams which run a 240duration 7.8mm lift exh cam vs the rb25de's 232duration 7.3mm.

I'll try to dig up the R32 RB25DE and RB20DET cam centerlines to get you started.

Cubes Grand Master

Cubes

Posted
Posted

Ok got the centerlines...

R32 RB25DE

Inlet: 240dur 7.8mm lift, Centerline: 112degree's

Exh.: 232dur 7.3mm lift, Centerline: 118degree's (I think)

IVO: 8, IVC: 52, EVO: 54, EVO: -2

In/Exh lobe relationship (LCA): 115degree's

Overlap: 6degree's

RB20DET

Inlet: 240dur 7.8mm lift, Centerline: 115degree's

Exh.: 240dur 7.8mm lift, Centerline: 120degree's

IVO: 5, IVC: 55, EVO: 60, EVC: 0

In/Exh. labe relationship (LCA): 117.5degree's

Overlap: 5degree's

Should give you a good head start in where to begin fiddling. :ban:

Also note the tomei web site lists very very slightly(LCA) different specs for the cams. I'll believe the engine manual.

Where to start with the 3ltr... No idea :wave:

post-382-1160403623.jpg

WazR32GTSt Grand Master

WazR32GTSt

Posted
Posted

as said leave it at zero for the dyno operator to change...

on my rb20det i made more power everywhere with +3 inlet and -5 exhaust settings (do a search i wrote it all in a thread somewhere)

it basically shifted the power curve left so that at the same rpm i was making about 10% more power.. :(

mr_rbman Grand Master

mr_rbman

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as said leave it at zero for the dyno operator to change...

on my rb20det i made more power everywhere with +3 inlet and -5 exhaust settings (do a search i wrote it all in a thread somewhere)

it basically shifted the power curve left so that at the same rpm i was making about 10% more power.. :)

cheers, i tried looking for that thread as i remember it but i dunno what i do when i search but i never seem to find what i wanna look for!

Cubes, thanks for that but isn't that referring to camshafts rather than cam gears? I think i'll let Shaun just fiddle with it on the dyno, as long as i have it setup safe to drive for a while i'll be happy!

Cubes Grand Master

Cubes

Posted
Posted
cheers, i tried looking for that thread as i remember it but i dunno what i do when i search but i never seem to find what i wanna look for!

Cubes, thanks for that but isn't that referring to camshafts rather than cam gears? I think i'll let Shaun just fiddle with it on the dyno, as long as i have it setup safe to drive for a while i'll be happy!

The cam gears is what setup the centerlines... For example 0 on the rb25de inlet cam is a centerline of 112degree's. Move the cam gear -5 or +5 and it changes the cams centerline accordingly.

So there's 3degree's difference between the std positioning of the rb25de and rb20det inlet cam.

Sky30 ran a heap of overlap to bring the turbo on sooner and pick up mid range power; from memory top end power was sacrificed by ~10rwkw but he picked up something like 20-30rwkw through the mid. He will be able to clear up the exact power increases. I can't remember exactly but those numbers do ring a bell. :)

mr_rbman Grand Master

mr_rbman

Posted
  • Author
Posted
The cam gears is what setup the centerlines... For example 0 on the rb25de inlet cam is a centerline of 112degree's. Move the cam gear -5 or +5 and it changes the cams centerline accordingly.

So there's 3degree's difference between the std positioning of the rb25de and rb20det inlet cam.

Sky30 ran a heap of overlap to bring the turbo on sooner and pick up mid range power; from memory top end power was sacrificed by ~10rwkw but he picked up something like 20-30rwkw through the mid. He will be able to clear up the exact power increases. I can't remember exactly but those numbers do ring a bell. :P

ahhh, i understand now, takes me a couple of reads to understand things but i get there! I'll msg andrew!

The Dan Grand Master

The Dan

Posted
Posted
3lit3,

By retarding the exh. cam by 2 degree's what sort of gains do you see? Mid to high rpm with no noticable loss from the low end?

Mainly just a jump in mid range. No loss down low but I am using a GT2876 with a 0.86 rear so it really has nothing down low anyway.

Cubes Grand Master

Cubes

Posted
Posted

I'd say start again.

Rip out the radiator, harmonic balancer and cam belt covers.

Throw it on to TDC and check the cam timing is all lined up.

By leaving the harmonic balancer on and trying to line everything up its possible for the belt to be slightly off the lower drive gear (simply because there's no tension on it and you can't see it), as a result when you spin the motor over it jumps a tooth or two and the cam timing is thrown out.

If you remember back to when you first got the motor in the car, I checked and reset (as it was out a tooth) the cam timing; I pulled off the balancer as it wasn't worth the hassle of the lower drive gear being out a tooth or two.

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