lower peak cyl pressure with turbo

[Anonymous]

say I raised my static comp to about 20:1. I only let the intake open 1/2 the stroke time, close about 50* BBDC so I would only have half the cyl peak pressure. and more of an expansion rate.

about 10:1 now.

now i figure VE would decrease especially at higher rpm........ok so i put a turbo on......now I have more air...........too much? and start to detonate ect.

so with this setup will this only work with a N/A engine?

Its a given that I have a small, fast burn chamber.


Am i missing something?

 

[Anonymous]

do I just limit the intake stroke more? but how would this help?

perhaps the turbo simply wouldn't aid anything.

 

[StrangeRanger]

Is this what you're looking for?

http://en.wikipedia.org/wiki/Miller_cycle

 

[Anonymous]

thank you for the link.

I am trying to do essentialy the same thing except have the intake close earler than later.

up the compression, reduce peak pressure, and increase the expansion rate.

have the exaust open about 10* BBDC.

by creating a more complete-faster burn, and more expansion, I will have recouped any power loss from having less air.

also the piston wont have to use so much energy to compress the charge with the higher comp ratio.

with the greater expansion rate the egt's will lower.




sounds great except for any kind of lean burn you will have to increase the intake temp and or use a turbo.

I am trying to figure out haw to acheive this with a turbo.

 

[Lazy JW]

...have the exaust open about 10* BBDC...

Hmmmm....even the slowest revving of the low-speed torque engines I have studied open the exhaust valve a lot sooner than that. The latest I can recall opening is around 35º BBDC. Apparently the designers wanted to vent those gases early enough to avoid any excess pressure when the piston starts upward on the exhaust stroke. That would certainly rob power. Just guessing, but that's what I have observed.
Joe

 

[ASMART]

In general, it sounds like you want a very high compression ratio(physical) but limit the intake valve opening to limit cylinder pressure. Since the intake is closed longer you have more time to exhaust. Very short duration works well on low rpm but kills higher rpm performance. The turbo pressure would be need to be used as RPM increased to keep cylinder pressure up. Iam not sure about the exact valve timing you are talking about but I can see that working. Of course it wouldn't be the ultimate power machine but might have some economy and performance benifits.