Camshaft grinds for turbo

[panel]

Man that guy is excited

[Ron Perkins]

I used a custom grind fk-45 with 112 LCD.....was amazingly decent at idle pull as far as you wanted it to. Doesn't really seem to make that much difference when you turbo.

[Steve Arndt]

86B 112LC would work great.

[Ron Perkins]

Like I said doesn't really seem to make that much difference...especially if you are running efi. CB, Comp Engineering...Gurus in turboing vws...all use close LC cams with small durations...main thing for street driving...least overlap with decent duration...THEN GO TURBO.

[miniman82]

See? I've been a guru all these years, banging the tight LSA drum. You guys are all stupid! lol

Seriously, it all comes back to what kind of combo you're building. If you like flat OEM style torque, go with the wide LSA and short duration. If you like an engine that's still snappy like an N/A engine but with massive midrange, keep the 107 LSA with around the same duration as if it really were N/A or somewhere in that area. My example: 1915, ~285 adv duration, 107 LSA, ~.350" lift @ cam. Even with low ass compression (7.3:1), it's responsive because of the EFI. I doubt the same results could be had with a draw through carb setup, you'd probably have to up the compression a whole point for the same results.

[Buggsy]

You could always assemble it with a moderate cam, measure the backpressure verses the boost pressure and then decide on overlap. But then you have to completely disassemble the engine to put in the right cam. And no doubt some will say you don't have the right turbine housing if back pressue and boost are not even, but street and road racing, in my opinion, call for a smaller ar on the exhaust side than other situations like drag racing or top speed racing.

[Ron Perkins]

What's really strange about this...I pulled the turbo system off my 2332 cc motor, Pat downs built big welded heads. 8.3:1 CR. Put my old dual 40 blo thru dells on in NA form, except no vents, CB upgrade...cam is still the FK-45 112 lobe centers...the motor is so frickin snappy from an idle...you just punch it and it sings to 5 grand lighting up the tires...crazy feeling with that turbo cam in it. Doubt if it would pull hard past 7g, though.

[miniman82]

OK, but an FK-45 still has 295 adv duration, so it's not like it's a small cam either. In order to get more RPM potential out of that setup, you'd need a tighter LSA.

[Wally]

In order to get more RPM potential out of that setup, you'd need a tighter LSA.

Isn't it the other way around?

This is my experience:
My former cam had less duration, but 114LC and went to 7K for max hp.
My new cam had more duration and lift, but 108LC and went only to 6.5K for max hp
but had more torque (because of the higher lift and/or less LC?).
Same engine, same dyno.

[Steve Arndt]

http://www.compcams.com/Technical/FAQ/LSAproperties.asp

[miniman82]

In order to get more RPM potential out of that setup, you'd need a tighter LSA.

Isn't it the other way around?

My comment was in relation to Ron's removal of the turbo system, AKA no pressure. More overlap tends to help in that situation.

[Wally]

In order to get more RPM potential out of that setup, you'd need a tighter LSA.

Isn't it the other way around?

My comment was in relation to Ron's removal of the turbo system, AKA no pressure. More overlap tends to help in that situation.

Its still doubtfull it works that way as the more overlap is not the only effect tighter LC's have... Larger LC also changes the closing and opening events on the other ends of the valve timing event as a whole and in such a way that it gives more RPM potential, same way it does in a blown situation.

There is really surprisingly little difference in the way cams behave in blown or N/A applications.

[miniman82]

There is really surprisingly little difference in the way cams behave in blown or N/A applications.

You're right, but the devil is in the details: the way that increasing manifold pressure has a way of extending the RPM potential of a given cam when going from N/A to forced, the fact that you don't need ridiculous amounts of lift with forced induction, THERE IS NO SUCH THING AS A TURBO CAM.... are these things people generally notice, or are we just anal like that because we find minutia interesting? I know I do, others may not so it might not matter to someone else what the LSA of the cam is so long as it's fun to drive and operates in the correct RPM range.

Don't get me wrong, there are different ways of grinding a cam when it comes to the difference between forced and natural. Not that there are hard and fast rules, but in some instances what works for one application wouldn't work at all in the other. More like there are different strategies when it comes to cams, I personally don't see names for any of them (turbo or otherwise), just different ways of skinning the cat. More duration, less duration, wide LSA, tight LSA. They're just cams.

[shag55]

A FK-45 is a great cam and will pull to 8500-9k in the motor.
I think you are right on target Wally! Huge duration is not needed to turn high RPMs just as not only small duration cams will give you great bottom end. Its all about the correct valve timing for a given motor and turbo.

[Wally]

Another example: I now run a FK7 (just 244 duration) in the 1200cc turbo engine and it made max power at 5500-6000.
To get more power, I think I need the intake valve to stay open longer, but I don;t want the intake valve to close too late as that will lower my dynamic CR too much (ie around town driving will suffer).
So I looked at many cam cards and actually only the grinds from Pauter do what I like.
Therefore my next cam will hopefully be a Pauter K8E8, which has 256 duration (0.050), but with only 2 degrees later intake valve closing timing.

Problem is, I can't find a dealer for Pauter cams... surely s/body must have these in stock?