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Technical uprated/double valve springs

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Technical uprated/double valve springs

I've been running in the 15 to 20 psi boost range for ages & am revving to 8200 rpm. The valve springs were all replaced when the engine was rebuilt with higher quality springs of basically OE spec.

Why >8000rpm and turbo?.. Power without to much torque :)
 
Yes, to a point. Essentially, & simplistically, if you reduce torque by 10% but run 15% lower gearing you have a net thrust gain of 5%. Obviously if flip that on its head, reducing torque by 15% and gearing by 10% then you have a net loss. On the drag strip you spend a large amount of time in the upper rpm registers, a higher torque engine will win on the 1st pull away from the line, however in all honesty for good 0-whatever times 2nd gear launches are the order of the day on anything other than a perfect surface with the turbo.

The performance loss is fast road driving when you're wanting to keep the revs down, you simply don't have the same torque levels. Though thinking about it, I never got close to WOT much bellow 4000 rpm on the road anyway & the torque reduction in the <4000 rpm range has made the car much more progressive while still delivering good torque, 95lbft at the wheels, from around 2400rpm up.
 
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ok so Gaz you dont need the uprated valve springs just get some newer ones
as im using the larget turbo and to a later date going with an aftermarket ecu (unless we work out how to get p75 ecu to rev 8500) my power band will be further up so will still be using the new valve springs when i get chance to pick them up
 
The only argument I can see for stronger springs on turbo apps (given "normal" cams) is that -- on non desmo engines -- the only thing shutting the valves is the spring (a silly design, but one that seems to work pretty well). It could be argued that the spring has to overcome boost in order to shut the valve. But I really can't see this being significant except at extremely high boost levels. Otherwise, Lancia would have called Ducati in to design the valve train for the S4, surely?
 
wont be doing much drag racing
using a 6speed box i find the gear ratios short, so want the extra revs
and for the "pub talk" numbers my 0-60mph times be bit shorter being able to get past 60mph in second:D
high revs will shorten engine life :whogives::eek: each to there own(set up):nutter:
 
Craig, about those valves. the exhaust one looks good, with the thinner stem. But whats happened to the inlet, that has a fatter stem than standard, so how can that be lighter??
Anyway i still carnt get onto eper so i might pop into fiat sometime to try and use there computer(y)
 
I think ill leave the Desmodomic valves for you to sort. Looks blumming complicated to make and fit a FIRE head. mucho respect if you do it. Ill stick to me springs
 
fingers99 said:
That would be my view, too. After all, if the revs don't exceed standard revs and the cam isn't humpty bumpty, what extra stress is placed on the springs? And what's up with a turbo application that needs 8k rpm?

Tom, you should fabricate a desmodromic set up, or go pneumatic........ ;)
Click to expand...

someone's been reading Racecar Engineering Mag!!!!!!!
 
Racecar Engineering did a big thing on desmo / spring / pneu valve operation a while ago. Pneu seems to be favoured by F1 but the compressor costs power. Not really another way of opening and closing your trusty valves on an F1 engine. The speeds that we class as rev limits and what they call an idle!

Just emailed Guy Croft about his spring kits. The man is a legend!
 
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