Q. How restrictive is the pop off valve?

[Robin Plummer]

I note that the current Champ Cars engines such as Honda's are now revving to 15,000rpm which is amazing for steel spring valves. Now the question I have is the engines produce about 850-900bhp with the pop value on. How much could they produce without that restrcitor?

[enzo]

The popoff doesn't 'restrict', it limits maximum boost pressures.

I asked that of a Ford engineer a while back - he figured 2000 hp with unlimited boost & a redesign of some components would be reletively easy to obtain, but not for very long!

[Crash Test]

Shoot!

Where's Franklin with his jet engines now?

[Robin Plummer]

Enzo surely to limit something is to restrict?

If your road car will not rev above 7500rpm it is restrcited to that amount, as the engine will go higher?

[enzo]

Sorry - when I hear "restrict' in this context, I think of meaning a flow restricter like a venturi.

Just a matter of semantics, I guess ! C'est la vie!

[KC]

According to RaceTech Engineering, the valve springs used in CART have been the most studied and tested components on the cars. Honda, Ford-Cosworth, Mercedes-Ilmor, and Toyota have spent many hours and tons of money developing the current lot of titanium mult-coil springs used to limit valve float at the insane rpms turned.

[Franklin]

CART cars are only slightly lighter than the Porsche 917/30 Can-Am car (a 1,300 to 1,500 horsepower car).

If CART had engines producing 1,500 to 2,000 horsepower but were restricted to two-wheel drive and current size tires there would be a lot less incentive for building 15,000 rpm engines.