[968norway]

I was talking to the engine guy at the porsche center. He had a 968CS when he was working for a tuner in Germany. They took an exhaust cam and cut off the bit for the timing belt and used it as an inlet cam since it has more lift (so he said). They set up a chip and he was getting 270 hp on the dyno. He seems to have had a different exhaust manifold also.



Kind of interesting, has anyone heard of this?

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[Cloud9...68]

I wonder what they used for the exhaust cam...

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[968norway]

I think the exhaust cam was just the standard one. It just seems interesting since performance cams are such a rarity.

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[eurocarnut9xx]

This doesn’t make any sense…



The stock cam specs with variocam inactive (basic timing, rpm < 1500, 5500 < rpm) are:

IVO <acronym title='before top dead center'>BTDC</acronym> -7.5

IVC ABDC 52.0

EVO BBDC 31.0

EVC ATDC 1.0

Lobe center 112.5

Overlap -6.5



And with variocam active (torque timing, 1500 < rpm < 5500rpm) are:

IVO <acronym title='before top dead center'>BTDC</acronym> 7.5

IVC ABDC 37.0

EVO BBDC 31.0

EVC ATDC 1.0

Lobe center 105.0

Overlap 8.5



These give intake duration of 224.5 with 11mm lift, and exhaust duration of 212.0 with 10mm lift. I fail to see how using a shorter duration cam profile with less lift would improve the overall volumetric efficiency of the engine? Perhaps it was the other way around, as it is the intake cam that is connected to the timing belt, has longer duration, and higher lift? If they did do something like that it may provide better cylinder scavenging if appropriately balanced with other components.

Pete has helped develop cams for these cars, and while I do not know the specifications of those cams, he may be able to chime in on the affects of various configurations?

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[968norway]

Yes, it turns out the exhaust cam actually has less lift, but I was just relating something someone said. Though it may be the case that at higher rpm's, less lift is what is needed. From what I've heard about RSBarn stage 3, most of the power gains are at the top end. It could be that the high lift is best for the low end torque and less lift is better for top end. Also, the gain the mechanic said he had are about what RSBarn gets.

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[RMW]

anyone have a set of stock cams for sale?

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[unknown4u]

Interesting story. Not because of the lift but for the possibility to lose the chain if I would like perhaps in the future when adding a compressor...... Then I can fit a longer belt and fit an electrical waterpump as well. Maybe......

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