Later IVC for supercharged engine?

[plovett]

Would a supercharged engine like a later intake valve closing point, compared to a similar naturally aspirated engine?

I'm thinking the higher manifold pressure might allow effective cylinder filling longer in terms of crank rotation? Or is the differential pressure between the intake and the cylinder not what I think?

thanks,

paulie

[Newold1]

Pressure differential is the "Prime Number"

[plovett]

So is the pressure differential in a supercharged engine typically such that, it makes more power with a later intake valve closing point?

[Newold1]

No, not necessarily as I see it. A supercharger in boost will put a larger air/fuel mixture in a cylinder and make more power even if the IVC is left the same and somewhat optimized for N/A. Even with supercharging moving the IVC to late can allow the pressures in the cylinder to be decreased to a point where power can be lost.

[ptuomov]

https://en.m.wikipedia.org/wiki/Miller_cycle

[plovett]

Well I read about the Miller Cycle. Does this apply to our normal supercharged engines?

paulie

[Newold1]

NOPE, not our aftermarket or most production supercharged engines. It's a specific design architecture and build.

[ptuomov]

Well I read about the Miller Cycle. Does this apply to our normal supercharged engines?

paulie

Yes, if you’re not trying to make the most power per displacement, just a well running efficient engine.

[modok]

it could end up either way, depending on everything.
IMO long runners are not great idea, especially with a roots. that could be a factor, if it had long runners to begin with.
And of course...intercooling, or lack of, is also a factor.

[ptuomov]

If you have a relatively high compression engine and you supercharge it with minimal intake runner lengths, then retarding the valve events like in a Miller cycle engine would in my opinion something that would make sense for a street engine. It'd be efficient and one wouldn't have to redo the whole thing from scratch.

[Newold1]

Your supposition of how to use supercharging boost on an already existing high compression engine is a possible application except that the later IVC required to lower final compression while in boost to stop detonation would also lower the performance by lowering the engines compression ratio when the engine was not receiving enough boost from the supercharger at low rpms.
This is a situation where actual dynamic compression is a big factor.

[ptuomov]

Your supposition of how to use supercharging boost on an already existing high compression engine is a possible application except that the later IVC required to lower final compression while in boost to stop detonation would also lower the performance by lowering the engines compression ratio when the engine was not receiving enough boost from the supercharger at low rpms.
This is a situation where actual dynamic compression is a big factor.

I wouldn't do this with a centrifugal supercharger, but it would work with say a twin-screw or roots supercharger.

[Orr89rocz]

Do you mean a later ivc combined with a later ivo? Or you just changing ivc?

Imo for a given motor with a given duration intake lobe, the na motor would have a lower intake centerline and thus earlier ivo and ivc. The blower engines and alot of turbo stuff i have seen some cams spec’d with a slightly later intake centerline, so ivc is later but so is ivo
Exhaust is also pushed out on a later centerline so result is a wider lsa

[plovett]

Do you mean a later ivc combined with a later ivo? Or you just changing ivc?

I was thinking about a later IVC combined with a later IVO, but only because I was thinking about retarding an existing cam. I'm open to other thoughts, though.

thanks,

paulie

[cjperformance]

Do you mean a later ivc combined with a later ivo? Or you just changing ivc?

I was thinking about a later IVC combined with a later IVO, but only because I was thinking about retarding an existing cam. I'm open to other thoughts, though.

thanks,

paulie

Depends on the i & e timing events of the existing cam as to wether the later exhaust timing (unless we are talking dohc?) from retarding the cam will hurt much