Worth Changing Cams?

[PM-R33]

Exactly. I picked up next to no gains in peak horsepower because my turbo is all ready at it's limit. However that is not what larger cams do.

The fact I gained so much power at so low RPM means the car comes onto boost faster and harder, revs out quicker and is faster overall on the street.

It would be like me engaging my nitrous at 2000rpm and turning it off at 4500rpm. On a dyno printout my peak horsepower would be bugger all bigger. Does that mean the nitrous did nothing? Hardly.

[zebra]

Whats it like at part throttle/cruise though? bigger cams mean less dynamic comp = less HP unless it has boost

[PM-R33]

I didn't really notice any difference.

[lookingforboost]

its all about under the curve if its manily a street car, just dont run out and buy the biggest ones you can find like some do

[zebra]

its all about under the curve if its manily a street car, just dont run out and buy the biggest ones you can find like some do

This - On a regularly driven street car I would be more concerned about having a good idle and what I call carpark drive ablility, i.e light throttle in 1st gear, or pulling up a sloping driveway without having to ride the clutch etc.

Being able to do this would mean more to me than 10-20kws at 4000rpm and WOT.

so it really depends on what you want to do with the car.

[PM-R33]

Hence why I didn't go some stupidly large cams. I got a power increase at every single RPM point after doing the headwork/cams. (One of my old threads is kicking around somewhere in FI where I posted my results).

I swear most people have no understanding of what "Duration" actually means and just open a catalogue and go "F**k yeah, 280 degrees sounds tuff!".

[zebra]

Hence why I didn't go some stupidly large cams. I got a power increase at every single RPM point after doing the headwork/cams. (One of my old threads is kicking around somewhere in FI where I posted my results).

I swear most people have no understanding of what "Duration" actually means and just open a catalogue and go "F**k yeah, 280 degrees sounds tuff!".

Haha yeah It happens everywhere, I knew a bloke who put a 600thou lift and something with 260odd degrees at .050 cam in his stock 308 and wondered why it made 35hp on the dyno.

[joeyjoejoejuniorshabadoo]

so what cams did you opt for again phil?

i've been thinking about camming mine for ages

[PM-R33]

I used to have HKS 256/264 cams but sold them becuase my tuner said they were f**ked and couldn't get the car to make power.

Then went Poncams and still my tuner said they were f**ked. Then found out I had a collapsed cat! So should have just kept the HKS cams

[zebra]

Oh that sucks!

[PM-R33]

Tell me about it...

[radianation]

I saw a mild gain after installing Tomei Poncams on S2 RB25DET. I retained VCT on the intake cam. I did some pulls with/without VCT on and the low/mid torque and spoolup times were significantly different, justifying keeping VCT in my situation. The cams really seem to open up the RB25DET head for further upgrades. The install is not terribly difficult and if you plan on doing more in the future go ahead and upgrade your valve springs while it's out so you can increase your redline. I'm going back to do that now.

Blue line = After Camshaft @ 20 PSI (and smaller exhaust housing on turbo hence quicker spool)

Red line = Before Camshaft @ 18 PSI

I hope this helps you in your decision. I'm pleased with the upgrade.

Edited December 13, 2010 by radianation

[zebra]

I saw around 40rwhp gain after installing Tomei Poncams on S2 RB25DET. I retained VCT on the intake cam. I did some pulls with/without VCT on and the low/mid torque and spoolup times were significantly different, justifying keeping VCT in my situation. The cams really seem to open up the RB25DET head for further upgrades. The install is not terribly difficult and if you plan on doing more in the future go ahead and upgrade your valve springs while it's out so you can increase your redline. I'm going back to do that now.

What turbo, Manifolds, port work etc, just saying 40rwhp is meaningless without more detail.

[R31Nismoid]

You'll see why its meaningless below...

Blue line = After Camshaft @ 20 PSI (and smaller exhaust housing on turbo hence quicker spool)

Red line = Before Camshaft @ 18 PSI

I hope this helps you in your decision. I'm pleased with the upgrade.

How can you even begin to post that and use it as a comparative result?

You've changed the exhaust housing which has altered boost from

18psi @ 5000rpm

to

18psi @ 4200rpm

To me it basically looks like all your gains are from the exhaust housing and nothing else.

[zebra]

yeah an extra 2psi of boost to boot, hardly a direct comaprison

[radianation]

True. The comparison dyno chart was not made specifically to test the camshafts, and my other adjustments make it hard to determine what's accurate. If you're not going for big power then you might want to skip on them, but I've not yet hit my goals so they are a step in the right direction.

Again, I hope it helps you make a decision either way. Obviously, you've used my chart to show that there is no reason to upgrade so it's worth something? ; )

Edited December 13, 2010 by radianation

[R.3.2.G.T.R]

so cams won't increase peak power however does shift the powerband, what I don't get is, upgrading would mean going larger than stock, yet response/spool is somehow better than stock down low, how?

[R31Nismoid]

It's on a dyno.

What some testing did down here was find that cars looked better on the graph, but on the circuit they were slower.

Hence a lot of Racepace cars all went back to stock cams, a few had poncams etc.

[ceejay77]

factory cams are high performane,huge job changing cams and for the amount of work the difference will not be great,I know someone who tried and was a major headache and disappointing finish,he regretted doing it.

[zebra]

so cams won't increase peak power however does shift the powerband, what I don't get is, upgrading would mean going larger than stock, yet response/spool is somehow better than stock down low, how?

I dont think response increases, but midrange power will, the top end wont increase on a smaller turbo eg. Phils GTRS because they are already at max airflow on a stock RB25, a bigger turbo that can flow more air will show gains in the top end.

So throwing some cames at a stock turbo Rb25 will give you nothing apart from a lighter wallet.

Imo I would not change the cams unless I had a .82 GT3076 or larger turbo on the car.