What are the benefits of running a cam on a forced induction application?

What are some ideal cams to accomodate either a TT/PD/CEN application?

Thank you


I did find this :

Thunder Racing Custom "Blower" Camshaft - 214/230 .601/.575 117 LSA. which isnt much different than their Thunder Racing Custom "CheaTR" Camshaft - 214/230 .601/.578 117 LSA.

 

Benefits are the same as on an N/A engine. The valves stay open longer, allow more A/F into the combustion chamber.

Having said that, cam designs can vary widely between turbos, centrifugal blowers, and positive displacement (Roots type or twin-screw "Maggie") blowers.

Cams for a Roots blower usually have a split duration, with the bias towards the exhaust. A/F is forced in, and you need the extra exhaust duration to scavenge the cylinder. LSA is usually pretty wide, 114 or higher. This is to keep valve overlap low --- don't want the intake charge running right out the exhaust. However, a blower can also tame a big cam, make it idle better. You got lots of boost down low, so the TQ curve from the cam doesn't have to be real flat. The TR cams you cited fit this profile. IMHO, you could go a lot higher than 214 on the intake duration, but the combustion pressures would be too high for stock compression ratio, so you'd need dished pistons or larger combustion chambers.

Turbo cams are often the opposite, with a reverse split. Exhaust duration is shorter to keep velocity and temps up, helps spin the turbo.

Cams for centrifugal blowers can vary. Since they don't produce a lot of boost down low, some grinders like to advance the cam a bit for better throttle response. If you run too big a cam, low end response will be really crummy. So, you want to match the cam profile to the boost profile. Best bet is to check with your blower vendor.

 

The main reason that you would go with a blower cam is allowing the engine to flow easier. Get more air in and more importantly get the exhaust out, thats why you want a much higher exhaust lobe and even lift. If you run a cam you can go with less boost which reduces heat, which is very import in my Houston heat, and still make the same hp. I plan to run a big pulley 5" with a D-1 and a cam around 218/224 .569 / .575 on a 115 and comp 918 springs.

 

What about this one with a PD setup


230/230 .591/.591 114 CompCam

 

Pd????

 

PD=Procharger D1??

In any case, no, you want more exhaust (second number) than intake (first number)

Personally with the power you will get from a Procharger I think there is no need for a cam. There will be zero traction at 550 HP, let alone 580.
To each his own, but to get the pieces in place for that car to have traction and be able to launch safely, you're looking at thousands of dollars, of course, I speaking of racing it. There are very few blown cars at the track, this may be the reason.
Throw a set of heads and a cam in it

 

I'm having the D1SC installed this month. My cam is a 224/230 581/592 114LSA. Also have AFR heads, Dynatech headers and Corsa Sports. I've been told my cam is a blower cam.

 

If I'm not mistaken, PD is Positive Displacement, i.e. Maggie or KB.

As mentioned before, PD superchargers like more exhaust and lots of LSA to reduce overlap. That cam would work, but is far from ideal on a PD supercharger. The cam just above would be better, but could still use a bigger LSA for your PD setup.

I believe this is the cam John Page at 21CMC puts in his maggie setups:

LPE LS1 Camshafts 207/220 .571/.578 w 1.7 rocker 118.5 CL
Code:LS1-GT2-3

Notice the exhaust is 13deg larger than the intake, and the large LSA.

 

I have that one too but since its 114 +2 LSA the cam is really like a 226/228 which isnt much of a difference. Andy from A&A uses a 224/224 so comming up with hard and fast rules like the cam should have more exhaust bias than intake is false since it is head dependant.

The only real rule should be that overlap is bad in FI

A 232/240 on a 110lsa wouldnt be optimum even thought it has a big exhaust bias.

 

Yes, PD is positive displacement.

I will be running the maggie.

 

The +2 does not affect the LSA, or the intake or exhaust duration, it affects the valve events, makes them occur earlier.

I'm sure that Andy from A&A knows what he's doing, but I thought he ran a centrifugal blower, not a Maggie.

What hard and fast rules? I said "usually", which is accurate. Most cam manufacturers will give the same advice. And it is not head dependent at all. No, a 110 LSA would not be optimal. As I said, "the LSA is usually pretty wide, 114 or higher."

I've had 3 different B&M blowers, and also a Whipple twin-screw design similar to the Maggie. I've had 5 different blower cams, 2 from B&M, two from Comp Cams, and a Lunati. The cam advice I got from all the vendors was remarkably similar, and proved to be accurate.

I also have had a single turbo Spearco setup on an SBC, running through stock cam & heads. I researched several different turbo cams, but never bought one because it was strictly a street application.

I've never owned a centrifugal blower, so I don't offer advice about them.

 

Does anyone have a sound clip with a "blower cam" so that we can hear the audible lope? I'm kind of interested to hear what it sounds like.
Thanks!

 

A blower cam such as I described should not have much lope at all. First, the LSA is fairly wide (114 or higher), which reduces overlap. Also, even in an overlap event (intake and exhaust valve are open at the same time), the intake charge is coming into the combustion chamber under boost. This prevents the exhaust charge from reverting back into the combustion chamber, keeps the idle smooth.