6 replies to this topic

[Mat Jackson]

You will probably have seen from previous posts I’m looking at new cams, but am getting more and more confused when I look at specs...

Basically, if two cams have the same duration and lift spec, will they produce the same power / delivery?

Reason I ask is I have piper regrinds with 260 duration and 10.75 lift.

Looking at other cams (Compcams and catcams) it seems hard to increase this spec - or is there more to it than that?

For example. Stage 2 compcam is 260 duration at 10.7 lift

Cat cam stage 1 is 253 at 10.75 and there stage 2 is 260 at 10.75

Surely a piper regrinds cam is not on a par with a catcam stage 2

Am I missing something? Looking at specs, not sure I want to spend £500 plus for little gains?


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Edited by Mat Jackson, 13 September 2018 - 12:05 PM.

[Mat Jackson]

Should say - these are for an NA on itbs


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[Tony H]

There is also the angle from TDC the valve starts to open. So it might be same duration but open and shut the valve earlier. Probably doesn't make any difference if have adjustable sprockets like the saab.

 

The lobes could be very different profiles but still have those same numbers. Imagine a pointy cam that opens linear to max lift then immediately starts closing. Then you could have a more oval lobe that opens faster but spends longer near the max lift, but still has the same lift and duration as the pointy lobe.

 

I think you should just ask vocky to tell you what to buy. 

[Exmantaa]

And if you compare duration specs, make sure these are measured at the same lift height... (ZZP/Comp use a different height spec f.i.)

 

And what do you want from you engine? 8000+ rpm screamer, or better  (low) torque for the road? Z22SE head or Saab head? 2.2ltr?

[CHILL Gone DUTCH]

My cams are suppose to be at there best over 8k rpm
But I only Rev to 7500

[Mat Jackson]

I’ve seen the different duration specs (1mm vs 0.050”), it did confuse me at first!!

Spec is 2.2 z2sse engine and head on itbs.

Will be fast road use weekend car, whilst happy to rev to get the power I don’t want an out and out top end racer




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Edited by Mat Jackson, 13 September 2018 - 04:53 PM.

[Nev]

Cam changes on NAs are trying to change VE (volumetric efficiency) at various RPM levels. Often, what you gain on part of the rpm curve, you lose elsewhere on the rpm curve. Bearing in mind maybe you'll gain a maybe 2 or 3 % of VE with any swap, it is far more efficient (financially and in terms of power) to super/turbo charge the car , where you'd easily see + 60% VE gains.

 

 

Edited by Nev, 14 September 2018 - 02:24 AM.