7A exhaust Cam

[Rusty]

Momentum of the inlet air should easily overcome that as the increase in pressure from the volumetric compression will be rather small over 6deg at the top of the stroke.

[4WheelDrifter]

True. Not bad for a turbo cam.
I've only compared cams for a BL A-Series turbo engine before . Trying to find minimum overlap. But -6°, I've never seen that before.

[Rusty]

Can't say I've ever compared standard cams. With an 2.0 8v golf it was a simple upgrade to a 266deg Piper or 270deg Kent and a vernier if you could be arsed.... those were the days!

[4WheelDrifter]

I looks as if both 7A cams would work really well, with only 3° of overlap and longer duration. The exhaust valves open 18° earlier than the RS2 and the inlets stay open for 3° longer.

[Rusty]

That'll be due to the higher momentum of the air entering in the forced induction engine being able to 'clear' the piston with the lower duration as opposed to the lower momentum air in a NA engine taking longer. 7A cams may reduce low end efficiency compared to RS2 cams due to increased blow through at these lower engine speeds where the overlap represents a significant amount of time. However, this would be rectified at higher revs due to the relatively lower time difference of the overlap.

[Jamo]

Has anyone asked kent or Piper cams to make a cam to the RS2 spec or giving them the original S2 cams for a more wild version?

[Rusty]

I suppose they could regrind the originals for a minor increase in both lift and duration (Tim Styles Racing do this on the VR6 Golf/Corrado, a relic from my VW days), assuming that the hydraulic tappets could take up the slack for the reduced minimum lobe radius. Anywhere with the correct equipment could do this but I agree that a 'performance specialist' camshaft manufacturer would be the best bet based on experience.

[4WheelDrifter]

I'm don't think I'll swap my cams. With -6° of overlap, I'm not sure the S2 cams would work so well in my cq20v.

[Rusty]

No! Performance camshafts all the way for you!

[Josh-stateside]

http://www.elgincams.com/campaper.html The # on the rs2 cams look different. We really sould have stickys for facts. If you do a search for pisobiker's post you will find info on the rs2 cams and the 7a cams.

there is a link^ to some good info on cams.

Cheers
josh