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Old 12-15-2009, 06:05 PM   #1
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Are Adjustable Cam Gears Worth It!

It has come the time to change my timing belt, since I have a Focus there are all sorts of goodies to make my car go fast and get really bad gas mileage, that is until I saw a pair of adjustable timing sprockets. Would the mileage improvements be worth the investment to have the ability to retard my intake cam a couple of degrees?

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Old 12-15-2009, 09:00 PM   #2
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Go for it. Cam gears will let you move the power around and put it where you want. I'd recomend advancing the intake cam for more low end power, which will let you shift sooner and keep the revs low.

OTOH retarding the intake cam might provide an Atkinson-cycle type of benefit during steady cruise. The only sure way to find out is to try it and see.

Dave W.
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Old 12-16-2009, 07:16 AM   #3
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how much of an investment are they?

hard to say if the advantages are worth it without knowing the initial investment.

I do like the idea of experimenting with timing
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Old 12-16-2009, 10:26 AM   #4
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I have an adjustable cam gear in my 455. I got it so I could index the cam, not as a tuning device.

However, one time I decided I had too much high-end power, and not enough low-end torque. So I advanced the cam 4 degrees.

Well I didn't pick up an low-end torque, I did lose high-end power, but I did gain about 4 MPG. That was when I was getting almost 20 MPG in my daily driving (probably mostly 18 or so, to be fair.)

But power was too far down, so I didn't leave it there.

I sure would love on-the-fly adjustable cam timing...

Think you are saving gas? Prove it by starting a Gas Log, then conduct a proper experiment.
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Old 12-16-2009, 11:26 AM   #5
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Hi all,
When I was a student I remember reading a thesis from two students who wanted to test different positions of the camshaft. I remember the vehicle was a small Fiat, with a small petrol engine DOHC, carburettor.
They could not adjust the camshaft while the engine was running, but they could very easy just change it a few degrees. After each adjustment they put the engine on a dyno and measured torque, BHP, fuel consumption and emissions on a range of RPM's and engine load.
Very interesting conclusion: NO gains could be achieved, on no matter what field when you only adjust the camshaftposition.
On engines developed by R&D-departments with variable camshafts everything is adapted to go with it (fuel mixture, ignition timing, EGR, expected lambdavalue, drive by wire throttle housing,...).
I know e.g. the variable exhaust camshaft on a European Honda TypeR's main function is EGR. They did not had to install a classic EGR, but by delaying the closing of exhaustvalve you suck in some exhaust gas....there's your EGR.
A question raises: aftermarket camshafts have most of the time only one goal: more power by more valve overlap and higher valvelift. If this is the case I would definitely not do this.
Based on this (limited) info I would not go for this modification.
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