Author Topic: Cam timing Set-up  (Read 4876 times)

Offline G-spot

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Cam timing Set-up
« on: August 15, 2008, 09:14:35 am »
Started this thread after almost adding it to the Rolling Road Day thread;
Has anyone done much playing around with there Cam timimng,  I ask this as I've been playing with my cam timing a bit recently and achieved some interesting results. Would be nice to measure(rolling road day in mind) how much variation I'm getting between setups.  For example, I retarded my cam by about 10degs before the Peaks event, which resulted in loads of low end torque, at least +10% increase in ecomany(42mpg on Peaks Rally/Tatton Park plus Motorway home as far as Ross-On-Wye), but I have lost some top end power, I know this is to be expected purely down to the physical constraints of a single OHC, but could be good discussion if anyone has had any other finding.

I've found if I have the Cam(schrink) coming in bang on No.1 inlet 17deg BTDC I get loads of top end power, the engine revs really freely, but I only achieve 10/11PSI boost, and below 3000rpm there ain't a lot of power which makes for differcult driving when the car is loaded up(hence the adjustment before Paeks Weekend) though I've managed fine when I'm on my own.

Since retarding it my boost is reaching nearer 14/15PSI, and it pulls from about 1600rpm, but definatly flattens off around 5k, but I think its slower overall.

I'm gonna continue to make interim adjustments every couple weeks and see what happens, but if anyone has got a know figure for optimum handover between torque and BHP whilst maintaining driverability it would good to compare notes.

 :nerd:

Offline hayesey

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Re: Cam timing Set-up
« Reply #1 on: August 15, 2008, 09:33:21 am »
don't be fooled by the boost reading, what you are measuring there is the back pressure building up in the inlet manifold.  The fact that with your timing advanced you see less boost at the inlet means that power of the air is getting into the engine which is a good thing generally.    

This should be an interesting thread though.  I will look forward to what people say as I've not messed about with my cam timing, I don't even have a vernier at the moment.

Offline PeteG40

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Re: Re: Cam timing Set-up
« Reply #2 on: August 15, 2008, 09:36:54 am »
i was just going to put the same as hayesey, you'll find big valve heads, big throttles and a gt inlet manifold will get low psi reading as the air is actually going in the engine as opposed to backing up in the inlet.