Cam Gear Adjustment

[david-b]

I read on Tuners and cant find it again something about what happens when the cam gears are adjusted. It was like, if you advance them, its more power higher up or lower down, but worse fuel or something. Does anyone know what I'm talking about? What happens when the cam gears are adjusted basically? I know physically what happens, but what's a result of that? Also, and helpful tuning tips for this topic also? Thanks.

[david-b]

http://www.dsmtuners.com/forums/showthread.php?t=247807

ADVANCING
Begins Intake Event Sooner
Open Intake Valve Sooner
Builds More Low-End Torque
Decrease Piston-Intake Valve Clearance
Increase Piston-Exhaust Valve Clearance

RETARDING
Delays Intake Event Closes Intake
Keeps Intake Valve Open Later
Builds More High-End Power
Increase Piston-Intake Valve Clearance
Decrease Piston-Exhaust Valve Clearance

This is what I was talking about. Is there any benefits to just doing say the Intake and not the exhaust, or vise versa?

[kjewer1]

I've been assing around with the cam gears a lot lately trying to get the revolvers to work. Mostly just retarding the intake cam. It was worth a couple MPH in trap speed. At some point I reached a point of diminishing return around 3-4 degrees. I was still holding too much boost on the top end (lower airflow) and getting a lot of knock in fourth with ridiculously low timing (peaking at ~12 degrees on 118 octane). I went back and set both cams to -2. This had a more profound effect on things. Boost dropped another psi more than just the intake at -4, and all of the knock went away and it took another ~5 degrees of timing. I forget what the performance gains were. If I was still on those cams I'd still be retarding both together until I reach the point of diminishing return, or I feel the exhaust valve is about to get smashed. Ted B gave me some advice that certain seems reasonable, for my particular case, and that was to retard both together until the point of deminishing return, the slowly advance the intake cam IIRC until it seems to have an effect.

Unfortunately I just don't have enough personal experience with this to be of much more help. The basic advice above is correct, advance to increase midrange, retard to increase top end. When you start to change them by differing amounts more things get involved, like lobe seperation angle and overlap, and the like. The dyno is really the only way to do this right, since making adjustments is almost ALWAYS a compromise. If you gain top end, you lose midrange, and vice versa. Cam gears are good for tailering the powerband to your needs, but you're not going to suddenly produce HP out of thin air.

[david-b]

I wasn't planning on getting more hp out of the air, but I want it to be running most efficiently right now. I know the dyno is the best place, but was just trying to get the jist of things. And again, minus a turbo, I only have full motor to go off results. Don't have any boost to deal with.

Now, this may be the ultimate nOObie questions, but advancing and retarding... advancing would be pushing the cams toward the front, right?

[kjewer1]

Depends on which way the motor rotates. A more appropriate way to look at is not in terms of front or back or whatever, but in relation to the direction of rotation. In other words, rotating the cams in the direction of rotation would be advancing, moving them in the opposite direction would be retarding.

Think of it in relation to the crank shaft position. If the motor turns clockwise, turning the cam clockwise moves it further "ahead" of the crankshaft compared to where it was before, so that is advancing it.

Etc.

[david-b]

Got ya. That's what I thought. Thanks for clearing that up.