Cams

[PranK]

Hey all, been meaning to ask for a while but kept forgetting.

I have a fair idea of cams but not entirely the effect of them according to their lift / degree's.

Ok, so my understanding is that cams have lift, and I assume that this relates to how high the cam goes when rotating. However, I dont know what the degree's mean or how any of this gives different power gains at different RPM... Engine internals are certainly not my strong point.

Thanks

C

[bogcock]

lift= mm valve lift

duration= how long its open in degrees

timing= difference between inlet exh lift

[PranK]

Ok, so to make higher HP you want it open longer and higher, is that right?

[bogcock]

depends on the setup.

usually more lift = more flow, but you also need duration. the problem lies in getting a good combo as at high rpm you can get valve slap, eg over revving. to compensate you can use tougher valve springs etc. but it depends on the lift. if the lift is more than the springs can take the springs will bind, or over compress.. VERY bad.

if you need high revs eg nat asperated, you need less duration more lift... to raise the rev range

use as a guide as this may not be correct to some out there

Edited June 21, 2006 by bogcock

[PranK]

So for an internally-stock GTR, you wouldn't want much lift, is that right? I think the tomei poncams are 262 and 10.2 and are supposed to be good for stock engines with bolt ons.

Thanks for this info too.

[bogcock]

poncams are good because they use the stock valvetrain.

if you want big power you will need more lift and around 264 duration..

procams are better, but you need to change valve springs, retainers etc

for a stock gtr (internally) cams wont really give too much benifit. ive seen stock cammed gtrs running 600hp with no problems. attend to other parts 1st, such as turbos, ecu, injectors zorst etc

Edited June 21, 2006 by bogcock

[PranK]

Ok cool, thanks for the help. Wasn't sure whether to go Turbo's or cams next, I dont want big power though, just good power.

Thanks again.

[bogcock]

def turbos... then ecu and injectors

[PranK]

Cool thanks.

[Ronin 09]

Christian - i went for std turbos, tomei poncams 260 9.15mm.

It made a huge difference to the midrange and drivability.

Someone else on here also did poncams on std turbos...

Full list is:

1.1 bar

turbo back exh

stock airbox, high flow filter

poncams + adj wheels

i reckon area under the curve is pretty good, and low down power...

sure turbos would have made more power, but drivability is very much improved... and I don't drive b/w 5000 - 8000 rpm all the time - 85% if the time is between 2000 and 4000 rpm

don't completely discount cams

[PranK]

And that was 260 9.2 on both int and exh?

You should think about getting a fuel presure reg. I found mine to be fantastic (I have very similar mods).

[Ronin 09]

yep its getting FPR and some other bits shortly...

poncam type-b

260 9.15 inlet and exh

[siddr20]

Wow that is very interesting!!

How much does poncams cost?? Also whats involved in installing them. Anything else needed inorder to use this??

[D-limo]

Isn't changing the exhaust cam gear on an internally stock GTR meant to be a worthy mod?

[R31Nismoid]

sure is.

cam gear on the RB26 gives solid gains for cheap

[B-Man]

Bit OT - but whats the diff between a PonCam and a ProCam ?

[PranK]

Yeah between my 2 GTRs I have done mods quite differently but gotten similar power, but the power is very different.

Old GTR;

Power FC

Full Exhaust

More Boost

243rwkw

New GTR;

Cam Gears

FPR

Full Exhaust

More Boost

250rwkw

But the way that power is produced on the new GTR is astounding compared to the old one and I reckon its all cam gears.

Poncams are only $850-ish delivered from Nengun, not sure how much fitting is tho.

[R31Nismoid]

IMO if your on the stock turbo's... just stick with the cam gear

[ned]

Bit OT - but whats the diff between a PonCam and a ProCam ?

Hi B-Man

I have just been doing similar research on cams also, and have found that while all the specs seem similar on the poncams and low end procams (eg 9.15 lift, similar durations), the procams are apparently a more aggressive "ramp" affecting the speed of valve opening. This means that the procams need the uprated springs where the poncams dont, and presumably affects the power/torque delivery.

The Tomei website has some good info in Engrish describing the cams.

Cheers

Ned

[B-Man]

Cool - thanks Ned - makes sense.