Author Topic: Tuning cam gears.  (Read 2880 times)

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Offline Pure_Sincerity

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Tuning cam gears.
« on: Feb 23, 2013, 09:13AM »
Read alot into the DIY adjustible cam gears for the ka24de, and decided I will give them a shot. Many guys from the dates have done so and all vouch that it yields good noticible results.

But what should we/I tune for ?

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advancing or retarding the intake cam will optimize cylinder pressure at various RPM ranges, advancing closes the intake valve earlier on the compression stroke to build more compression at lower RPM.

So, more compression at lower rpm = more down low torque ?

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Retarding the intake cam allows the intake valve to remain open longer to take advantage of the intake charges inertia to maintain good volumetric efficiency at higher RPM

Self explanatory, more power up high in the rpm board.

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.Overlap is the time that both intake and exhaust valves are open at the same time. Increasing the overlap period by advancing the intake cam and or re- tarding the exhaust cam, can increase the scavenging effect of a tuned exhaust, causing the intake charge to flow into the cylinder and out the exhaust. By sacrificing a small part of the intake charge as the exhaust valve closes, a stronger intake flow has been initiated earlier. If this is tuned correctly the net intake charge should be larger at some RPM range, but will probably decrease at another.

For a ka24de, that's a 2.5 degree retard on the intake cam and a 2.5 degree advance on the exhaust cam.

Obviously, before even starting your car After tuning your gears, you must check your valve clearance by rotating the engine manually by hand.

Personally I'm considering the Overlap for the lump lump and better exhaust scavenging or retarding the intake cam to around 5 degree for that higher rpm output.

Opinions ?

Most guys from the states have only advanced the intake cam 5 degree for the higher comp at lower rpm to get more torque. But due to the individual throttle bodies, I don't want any more low, I was to go for mid-high.
« Last Edit: Feb 23, 2013, 09:37AM by Pure_Sincerity »
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Offline MattJohn

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Re: Tuning cam gears.
« Reply #1 on: Feb 23, 2013, 01:38PM »
I don't know sorry  :P  :P

Offline crazy2287

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Re: Tuning cam gears.
« Reply #2 on: Feb 25, 2013, 11:01PM »
Typically you only adjust this to change your torque area. As you move the torque peak to a lower RPM the maximum achievable torque will get higher. however power at higher RPM is limited and total power will suffer.
Go the other way, the opposite is the case. Torque comes in at higher RPM. But not as strong, however the higher RPM torque calculates to give higher total horsepower. You WILL however need to consider that to make use of this you will need to increase your peak RPM and accept the consequences.
Typically you will need to insure your rotating assy can withstand the higher rpm. as well as increased valve spring pressures at a minimum.

best performance is usually had following the camshaft specifications. Altering the dial can be done if, for example, the cam you purchased had a rpm range of 4000-7000 and you were not comfortable revving that high you could advance the cam to bring that rpm range lower.

Playing with the LSA or overlap rather is interesting. It may be beneficial if your exhaust scavenges well and is free flowing. Be careful of over scavenging.
Be careful removing material from the cam gears. a failure there when the engine is running will obviously be the end of that engine. or at least a set of valves.

If you work out the PCD of the teeth on the cam gear you could offset the holes you drill to this PCD. this could give you a much finer control of the degrees of adjustment and at the same time space the holes apart more. Leaving more material between the holes will aid in strength. I've seen a cam gear shear its keyway before sooo.. yeah.
Bit of a mindfk to set it as you will need to jump teeth on the gear but once you get a dial gauge jigged up on number 1 it should be fine.

Just some food for thought. I like the idea though, will be interesting to see how you go. Make sure you get a reading before and after you fk with the cam dials.
« Last Edit: Feb 25, 2013, 11:11PM by crazy2287 »
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Offline SSS

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Re: Tuning cam gears.
« Reply #3 on: Feb 26, 2013, 07:26AM »
In addition to what has already been said, set them up on a dyno so you can see the effect to your torque curve straight away.

You may also need to adjust fuelling / timing to suit.

Offline chr1S

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Re: Tuning cam gears.
« Reply #4 on: Feb 26, 2013, 08:59AM »
I usually only use them to dial cams in, once they are dialled in RIGHT - amazing how many aren't.. the cams generally work as they are intended.

If you have cams that require big rpm and your bottom end can only handling idling, if you expect to tune this out with cam gears, good luck.

Oh, and clay the shit out of your engine so you know your limits.
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Offline Pure_Sincerity

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Re: Tuning cam gears.
« Reply #5 on: Feb 26, 2013, 09:44AM »
I do not intend on exceeding the factory redline, I was intending on obtaining more torque up high before the factory redline such as 4-5krpm if possible.

Also, "clay the shit out of your engine ?"
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Offline SSS

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Re: Tuning cam gears.
« Reply #6 on: Feb 26, 2013, 11:18AM »
I do not intend on exceeding the factory redline, I was intending on obtaining more torque up high before the factory redline such as 4-5krpm if possible.

Hopefully your ITB's will have provided the necessary bump to widen and lift your torque curve; personally i'd aim for no more than 5k rpm at peak torque. Otherwise it'll be a real prick to drive.

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Also, "clay the shit out of your engine ?"

Dummy assemble the engine, place roughly 3mm thick pieces of blu-tac / clay on the piston crown where the valves come closest to the piston crown. Install and torque down the head, then rotate the engine so the valves leave an impression in the clay / blu-tac.
Pull the head off, and using a vernier, measure the thickness that is left between the depressed clay / blu-tac and the piston crown, and this will give you your piston to valve clearance.

You can go as far to check it for various positions of the cam, ie 5 deg retarded and 5 deg advanced so you know how far your can advance / retard the cam and not make piston to valve contact.

As chris said, adj cam gears should only be used to correct cam timing where it differs from the cam grinder's cam specs. This is done by degreeing the cam, which would be done after the "claying" stage as I explained above.
Degreeing the cam checks the opening and closing of the valves relative to crank position, which is typically given by the cam grinder when you buy aftermarket cams.

Google it for the procedure, i won't regurgitate it here.

Offline crazy2287

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Re: Tuning cam gears.
« Reply #7 on: Feb 26, 2013, 05:15PM »
I do not intend on exceeding the factory redline, I was intending on obtaining more torque up high before the factory redline such as 4-5krpm if possible.

Also, "clay the shit out of your engine ?"

Then leave the torque curve where it is, a Dyno will tell you for sure but you want to have the power curve peak (Powercurve, NOT torque curve) just prior to your red line. I think you will find the engine will already be doing this as is most likely the factory settings.

I run the cam in my engine (old falcon) 2ยบ advanced to lower the torque curve. the cam is designed to 6000 but i wanted redline to be about 5500rpm due to limitations of the valve springs. so rather then loosing that power between 5500 and 6 by not using it i lowered the curve so it stops producing power by 5500. The car is still SLOWER then it would be, had i decided to increase valve spring pressure and maintained the cams intended settings.
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