More cam lift? to help spool, large turbo

[tuRBy]

If i change my cams lift from 9.1mm to 10 or 11mm will this make a large turbo spool faster, or earlier? if so by how much ? a hundred rpm, a few hundred?

is there a negative effect/s to having 10 or 11mm cams?

what duration cams will I need to hold a power curve that increases up to 9200rpm ? 280/272 or 290/280?

[seve7]

if you want faster boost you can always retard timing and add more fuel, although you have to watch your egt's as they can get out of control pretty easily like that. you can also advance the exhaust cam, and wrapping the exhaust manifold helps too.

[SamuraiSam]

Generally speaking the cams will increase your VE so yes your turbo would spool earlier

Every engine will be different and camshafts will net different results so I don't know if there are many people over here that can give you accurate answers.

seve7 you are techincally correct, however, I have tried this method on the dyno and the amount of power lost as you back off of mininum best torque, or your det threshold, is very large so i find it to be 'chasing one's tail'. The most timing that produces Minimum best torque before detonation is always the timing you want to run. Wrapping the exhaust manifold is an excellent excellent idea.

[seve7]

Originally Posted by SamuraiSam

Generally speaking the cams will increase your VE so yes your turbo would spool earlier

Every engine will be different and camshafts will net different results so I don't know if there are many people over here that can give you accurate answers.

seve7 you are techincally correct, however, I have tried this method on the dyno and the amount of power lost as you back off of mininum best torque, or your det threshold, is very large so i find it to be 'chasing one's tail'. The most timing that produces Minimum best torque before detonation is always the timing you want to run. Wrapping the exhaust manifold is an excellent excellent idea.

x2 on chasing the tail, any faster spool done this way is really marginal before dramatic loss of torque, i meant this as being easier on an engine than 2 stepping for launching. i didnt mean for a driving map, just a launch map on an ecu with switchable maps.

basically what is boils down to is 1 heat, and 2 air mass, increase either and the turbo will spool faster.

[SteveN]

longer duration cams will REDUCE low down power and torque, and make spoolup worse, not better.

i never understand why GTR owners seem to think otherwise, tho it explains how most GTRs drive, lol.

more lift though, thats a different story, tho how much it helps spoolup, well, debatable.

but if you want a powerband that goes to 9000+ you need lairy duration cams which isnt good for low down power anyhow, so you screwed.

its all swings and roundabouts, you cant have it all.

[paul cawson]

Originally Posted by tuRBy

is there a negative effect/s to having 10 or 11mm cams?

what duration cams will I need to hold a power curve that increases up to 9200rpm ? 280/272 or 290/280?

High lift cams give more torque without any effect to the power band so they are worth having.
As Steve has said long duration camshafts push the power band up the RPM range a must for big BHP but no good for low rpm response.

If you are pushing enough air through the head the long duration cams will help lag, but will make it worse on lower BHP engines

[Madden]

I have just seen some HKS 280 9.15mm lift cams. My power band is right at the top say after 5500rpm onwards. If i was to install these cams would it make my lag worse but increase the power up the top? I'm used to the really late power now and drive the car to suit.

Would 260 durration be better for me or the 280's. Single t04r turbo.

[paul cawson]

I would have thought 272s would be best, but have never had bigger than 264s myself so its best to check with a tuner. 280 cams with the right valve timing may work well.

[Madden]

Cheers mate i will have a look.

[tuRBy]

good ideas, will certainly look at having the manifold wrapped, and I thought about a heat jacket for the turbo exhaust housing.

On the cams, does 11mm lift put more wear on the engine? if not, and there are no downsides - 11mm is what I will go for.

As for higher cam duration, i dont mind losing 10 or 15% power under 4000ish rpm, looking for 4-5k faster spool , and a big gain 5k to 9k+. As long as the car idles 'ok' without cutting out, and the car drives smoothly like an NA 2.6 under 4k that suits me perfectly.

any ideas what duration I would need so it doesnt choke untill 9250rpm? 280/272 or 290/280? Am I right to go for stepped cams, or would 280/280 or 272/272 be a better choice?

[paul cawson]

Originally Posted by tuRBy

On the cams, does 11mm lift put more wear on the engine? if not, and there are no downsides - 11mm is what I will go for.

11mm camshafts require a lot of work, new valve springs, retainers, pockets in the pistons, stronger cambelt, head work for cam clearance.
You will also need a bigger duration to ramp up the lift, or have more valve train wear

[tuRBy]

Originally Posted by paul cawson

11mm camshafts require a lot of work, new valve springs, retainers, pockets in the pistons, stronger cambelt, head work for cam clearance.
You will also need a bigger duration to ramp up the lift, or have more valve train wear

thanks, do you know whats the max lift you can run safely without pocketed pistons?

and whats the minimum duration i need with 11's?

[paul cawson]

Originally Posted by tuRBy

thanks, do you know whats the max lift you can run safely without pocketed pistons?
and whats the minimum duration i need with 11's?

9.2 lift is the safe limit for piston clearance and 10.00 lift before uprating the stock valve springs and retainers
I think the minimum duration for 11mm lift is 280

[Madden]

Good stuff Pual. I was told max of 9.8mm before head mods. I didn't know you have to pocket the pistons **** that. I would just put a couple of headgaskets on

I got those 280 9.15mm cams for £230 so just waiting on delivery. What effects would changing the cam timing have on the performance? i.e advance and retard the inlet or exhuast cam?

[tuRBy]

paul: cheers

madden: would be interested to know what happens to your spool/full boost RPM before and after the cam change. have you dyno'd the car yet? so you can compare before and after.

There is some cam timing info on the tomei site, under - contents/adjust pully :

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