projekteg

i don't completely understand adjustable cam gears and the affects of adjusting them, and i'm sure i'm not alone so let's dedicate this thread for information from anyone who can explain the benefits and principle behind tuning adjustable cam gears, i feel like learning something today

iflybye

From what I have read, at least on a sohc your are just shifting the
power curve lower or higher depending on if you retard or advance the gear.

Here is an article for you reading enjoyment :P

http://www.sportcompactcarweb.com/in...technology01a/

projekteg

yeah, sohc is pretty straight forward, i'm referring more to dohc.

iflybye

The linked article goes over DOHC. In fact they use a DOHC honda for testing

http://www.sportcompactcarweb.com/in...technology01a/

midnite racer x

For SOHC engines cam gears have the ability to move the torque curve around creating more useable power.
My engine is only running between 4000rpm and redline on the track then i'm going to try to make my peak torque come in around the low 4000rpm area and sustain or keep the torque flat for as long as i can with the aid of an advanced ignition. You want to find out what the lowest rpm is when ur shifting gears on the track and try to match that rpm with your peak torque. You don't want to have to "build" up to your peak tq you want to get there fast and keep it there. And if u know anything about tq curves on boosted cars then u know if u flatten it out from peak tq to redline there will be a DRAMATIC increase in power. By advancing the cam gear you are essentially lowering the rpm that peak torque comes in. And retarding the cam timing raises the rpm. There is such thing as going overboard with adding to and subtracting from these bands. This is once again up to the user's discretion. In this case you run the risk of burning the valves from opening or closing to early during the crank cycle or simply exceeding the clearance limits of the valves and the pistons if you overly retard or advance the cam gear.

Credit goes to Deevergote on cb7tuner.com for this post...pretty informative.

Deevergote:
Ok, to go into a little detail about cam timing:

I haven't done anything but research myself, so all I know is from what I've read and confirmed from reliable sources. I'll be tuning my own engine soon enough. I just got my cam gears 2 weeks ago!

SOHC engines and DOHC engines can both benefit from soem cam adjustment. There is often a 1-2 degree variation in stock cam grinds (part of the explanation why some cars of the same model and trim have different power). By adjusting cam timing with an aftermarket cam gear(s), you can find that "sweet spot" where you can make more power. Tuning the cam gear(s) will also move the powerband around.

As a warning, cam tuning can be very dangerous. Staying within 6 degrees is usually safe, but beyond that you can have valve clearance issues (intake cam/lobes especially).

So, to get into it:

DOHC engines are much easier to tune, and you have more options. SOHC engines can benefit as well though. Most of what I know involves 2 cams, though.

For a SOHC, on a dyno, your best bet is to adjust the cam in 2 degree increments. This should be enough to show changes. Advance the cam first, then retard it. Play around till you find the spot where the power is highest in the usable RPM range.

DOHC has more options. 2 degree increments again are useful.
Start in this order to get your bearings faster: Advance intake, retard exhaust. Advance intake only. Retard intake only. Advance both intake and exhaust. Retard both intake and exhaust. Advance exhaust only. Retard exhaust only.

These adjustments often have these effects:

Advance intake only. Helps bottom end and midrange power, and doesn't affect top end too much. Can give a lopey idle. Works best on a stock head, and is a good first thing to try. Increases overlap, and starts the overlap period earlier.

Retard intake only. Reduces overlap, and starts the overlap period later. Not a great thing to do to stock engines. A good option for turbo, though. Turbos like as little overlap as possible.

Advance both intake and exhaust. Good for low end power, but chokes up high. The exhaust valve closes sooner, and the intake valve opens earlier. Exhaust gas scavenging is increased at low RPM. Moves the overlap period earlier. Pretty much one of two choices for SOHC.

Retard both intake and exhaust. Moves overlap later. Basically the opposite of advancing both cams/lobes. Good for high RPM. Your other choice for SOHC.

Advance exhaust only. Another thing stock engines don't like much. Reduces overlap and increases blowdown by opening the exhaust cam earlier. Good for top end, but hurts low an dmidrange.

Retard exhaust only. Increases overlap and adds a lopey idle. Not a bad thing to try on a stock engine. Usually, engines only like a couple degrees of exhaust cam retard.


Advancing the intake cam 4-5 degrees and retarding the exhaust cam1-2 degrees is usually good on stock motors.
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A lot of this info comes from Honda/Acura Engine Performance by Mike Kojima (SCC editor). It's a great book, and I would recommend it to anyone who wants to learn about the basics of their car.

93turbo16

that is serisouly what I was looking for. All of those conditions make sense and you can see it happen when you adjust them on the dyno, which is pretty cool.

megalomaniac0110

thanks midnite!! i used these degree settings on my 2001 r6 worked good going to fine tune as soon as the weather warms up