cammer427

Does anyone have any information on building a miller engine. I have heard back in the late 70's Crower offered a miller cam for the small block chevy. Is anyone doing this with the LS engines?

For those unfamiliar a miller engine uses a form of the atkinson cycle in which the intake valve is either closed early in the intake stroke or late in the compression stroke. This kills the volumetric efficiency of the engine so you have to run more boost than with a standard cam for the same horsepower. The benefit is potentially higher thermal efficiency depending on the amount of shaft power it takes to run the blower. The actual compression ratio will be lower than the geometric compression ratio due to the modified intake valve events so a higher than normal geometric compression ratio has to be used.

DAVESS02

iTrader: (30)

I'd bet this only becomes popular after servos replace cam and valve assemblies in motors. I had heard that when the move to a 48 VDC system in cars takes place, it'll also facilitate the move to PCM and servo controlled valve events. The valve/servo assembly will be much like a fuel injector from what I understand.

DanO

thats not a common request for aftermarket v8's.

However, its very doable, just get a cam from the hybrid suburbans/escalades as they are currently running atkinson in their 6.0L V8

It wouldnt be hard to have someone grind a cam to your specs.

engineermike

+1. Just figure out what compression and expansion ratio's you want (Miller means expansion ratio is greater than compression), spec out the valve events, choose the lobes and centerlines, then call up Comp or whomever you choose.

Funny thing is that changing the valve events simulates a Miller cycle without actually achieving the true cycle. Honda has an engine with a non-conventional piston-to-crank attachment mechanism that actually has a different stroke length for expansion than compression. Cool stuff.

cammer427

Gomechsystems has a good animation of their true atkinson cycle engine which uses an eccentric rod throw on the crank which changes the stroke length between compression and expansion.

z28boysteve

iTrader: (9)

Why not go so far as to replace coventional valves with Ball Valves in the cylinder heads? this would necessitate a less than 48 VDC servo to overcome the enormous spring pressure assosciated with overpowering a valvespring. Plus the valve head wouldn't shroud anything and you could run smaller ports in the cylinder head and get similiar performance I would guess.

stevieturbo

the rotary valve engine already exists.

http://www.coatesengine.com/technology.html


But as with all new technology, until it can be proven xxx,xxxmile reliable, and the cost can be brought down....it aint gona happen for everyone

engineermike

Yes, but that doesn't help achieve an Atkinson cycle.

cammer427

Using the miller cycle should help improve detonation margin on pump gas with boost. The trouble is without a pretty deep wallet and a dyno handy getting the correct expansion ratio and miller percentage could be tricky. So I wondered if anybody had a setup worked out.