flak monkey
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| posted on 30/9/10 at 05:57 PM |
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Please place your bets
The GTS is going on the rolling road again tomorrow after having the cams changed ready for Oss, the new owner. Hopefully it wont take too long to
dial back in - I am assuming its only going to need the fuelling altering and the ignition timing will be unaffected?
Just for fun, it would be interesting to see what you think the effect is going to be.
The last time it was on the rollers it made 265bhp @6300rpm and 245lbft at 5300rpm on standard cams with 12psi of boost.
All that has changed is the cams, the supercharger pulley and everything else is as it was at the last run.
My thinking is this:
The supercharger pumps a certain mass flow of air at a given RPM and pressure ratio. Therefore with the old set up it was pumping 0.36kg/s of air at a
PR of 1.8 bar.
The new cams are mild road cams, with slightly higher lift on both than standard (exhaust increased significantly) and much longer duration, therefore
there is now some level of overlap as well, where there was virtually no overlap with the original cams. The cams are the 210bhp spec ones from
raceline/caterham so would give a 20bhp increase in power on a standard engine with no blower.
Assuming the supercharger RPM is the same (which it is) and the factors above will cause some pressure ratio decrease. An increase in air flow will
also give a PR decrease. But a slight increase in mass air flow.
Therefore my prediction is that power will increase slightly over what it was last time, with a decrease in PR and a shift of the power up the rev
range and a corresponding decrease in torque at lower revs.
Out of interest, what think you? With your reasoning too 
Sera
http://www.motosera.com
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Ninehigh
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| posted on 30/9/10 at 07:55 PM |
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$20 on black 
It'll probably go up a bit, what's normal for race cams?
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ashg
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| posted on 30/9/10 at 07:57 PM |
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have to chuckle at how many pessimists there are on here
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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Ninehigh
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| posted on 30/9/10 at 09:31 PM |
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Actually reading it properly you might well get a bit less power as that valve overlap means you're blowing it straight through...
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r1bob
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| posted on 30/9/10 at 09:34 PM |
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ASH G
have to laugh how many pessimist's are on here
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flak monkey
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| posted on 30/9/10 at 10:37 PM |
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You miserable bunch! 
Sera
http://www.motosera.com
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Ivan
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| posted on 1/10/10 at 07:02 AM |
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I go for a 10% average increase with loss of torque low down but up to 15% increase above 4000 RPM where overlap will have less impact.
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flak monkey
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| posted on 1/10/10 at 01:26 PM |
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Results here
http://locostbuilders.co.uk/forum/9/viewthread.php?tid=143937
Sera
http://www.motosera.com
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