Cams with supercharger worth it?

[3deep]

Anybody have any experience with cams and supercharger.
Any grind or dur,lift data.

[mertdastan]

Supercharged engines hate cams with higher lift and duration because the overlap causes the engine to loose boost.

On our engines the intake valve opens while the piston travels upwards during the exhaust stroke. That is to scavenge the gases better and let fresh air to rmove the exhaust gases. When you open the inlet valves earlier than stock inlet valves you loose some of the air via the exhaust valve. And that does mean you loose some of your forced air.

So stay with standard cams.


Euro supercharged 600 hp 3,2M3

[jbob]

yep, altho only the overlap makes u loose power w/ forced induction, you can see some pretty good gains from higher lift and a little more duration as long as there' is little to zero overlap.

altho, having double vanos on ur m3 does increase overlap, but i'm assuming that performance chips made for forced induction setups change the overlap since there's a lot of turbo'd/supercharged m50's s50's around.

i'm sure someone probably makes cams for forced induction.....AA probably knows someone who can or maybe they can make them for you.

[ETHOMAS]

AA has a set of cams to work with SC I gave them a call a few months ago they said they have a cam kit that delivers an extra 30-35 hp.SC work well with cam's as long as the cams are design to work with SC.

[Spencer]

Did AA mention a price on how much they charge for those cams?

[Jeff Zusman]

Here we go, I hope you guys understand this stuff!


Needs spell check, I'm working in the dark here the kids are asleep!

Osh



Cams For Your Supercharged M3


It is correct, too much cam overlap across TDC is not desirable once
forced-air-induction exceeds a given velocity. On turbo cars it is best to
reduce overlap under all conditions as the rate-of-air-flow increases in
relationship to load ( not engine speed-RPM) On Supercharged engines the
Rate-Of-airflow increases in relationship to engine rpm. Therefore, on a
supercharged motor, keeping some overlap is good for bottom-end torque until the airflow exceeds a certain limit.

Once that limit is reached, blow-through will begin and continue with the increase in air flow (boost).On late model BMW motors we have the option to switch off the VANOS making it very adaptable to control cam timing under all dynamic airflow /rpm conditions. IE: keep the overlap for bottom end response and turn it off at the needed airflow-rpm limit.

So this raises some questions as to finding the best cam set-up for your
application. Lift and duration are the specs we all focus on when shopping
for performance cams, but what do these numbers mean in terms of performance for SC applications?

The VANOS will manage ( if programmed correctly) the switching point to reduce overlap; but how to make the lift and duration specs do the work we need is a long and complex proposition that often requires calculation and testing. Each test will also require tuning and quantification of data. If you bolt the (off the shelf) cams in, you will surely have better performance ( once the tuning is done).

Exhaust cam:
You can try advancing the ex cam to reduce overlap. This will certainly help
But there is often a trade off using this method. This will reduce blow
through but closing the ex cam sooner means opening it sooner. Opening it
sooner causes blow-down to occur sooner. (Blow-down is a term used for
blowing down the cylinder pressure to expel the cylinder of combustion
gases).

Once cylinder-blow-down happens, all the expanding gases pushing the
piston down are expelled. The power stroke is over! So the magic question
is , How much did I gain by reducing overlap and how much did I loose from
early blow down. The gains and the losses will be there by the mear facts
of physics. How much... is the unknown...

So what is the perfect exhaust cam for a supercharged engine? The true
answer lies in the R&D work. Perhaps an exhaust cam with less duration and
higher lift is the answer. This will reduce overlap and allows blow-down to happen later- allowing the combustion gasses to fully expand.

Intake cam:

Believe it or not , in this application , the Intake side is not as critical
as the exhaust side. The supercharger is forcing the air into the cylinder
so intake valve has no choice but to cooperate :-). Duration is good as long
as it doesn't interfere with the ex cam events. The maximum lift will be
dictated by the intake port and valve design. The M52 engine will not flow
anymore air worth working with after 11 mm lift. Larger valves and very
clever port work will yield more air flow but not by lifting the valve much
more than 11mm. The other dynamic that we have found that helps the intake cam profile is the ramp up speed of the cam. This is unfortunately at a high price as the hydraulic buckets and small diameter surface of the buckets don't leave allot of room for maximized lobe action. Aside from this design limitation of the m52 motor, clever cam timing, design, tuning and temperature control will wake the beast :-)

Cam selection and timing is not a simple science, There are many variables
that must be considered. Simply purchasing a set of performance cams is often a hit and miss proposition. However, a good set of performance cams are much better to start with than the stock units. You can better re-profile the cams for specialized applications such as yours.

Sincerely,

Osh Minelian

Director
Product Engineering
RMS


:

[Jeff Zusman]

all greek to me!