Variable compression
Variable compression
(OP)
How practical will a variable compression engine be?
Seems kind of fragile.
http://jalopnik.com/worlds-first-variable-compression-ratio-engine-could-ki-1785295848
Seems kind of fragile.
http://jalopnik.com/worlds-first-variable-compression-ratio-engine-could-ki-1785295848





RE: Variable compression
I have my doubts.
Benta.
RE: Variable compression
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Variable compression
je suis charlie
RE: Variable compression
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Variable compression
RE: Variable compression
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Variable compression
This was the practice on highly rated reciprocating aero-engines in the 40s and 50s, albeit using already high octane gasoline. But then again, they took advantage of all the octane also at cruise power, which is a much higher fraction of full load than typical automobile engines.
While these aero-engines aren't high compression by typical modern automotive standards, keep in mind they are highly supercharged at take-off power.
In a modern automotive application, there would be a fail-safe derate in the event of lack of fluid. Improper fluid would be detected via excessive knock, with attendant mitigation steps and trouble codes.
"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz
RE: Variable compression
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P.E. Metallurgy, Plymouth Tube
RE: Variable compression
If you are running at half rated torque output, with VVT trickery you are stuck with running at half (ish) of whatever the mechanical compression ratio is, because you are intentionally drawing only a half (ish) intake charge (whether by throttling or by VVT trickery). This mechanism allows the effective compression ratio to be maintained (ish) under those conditions.
Use of the variable compression mechanism in no way affects the possible use of VVT to simulate the Atkinson cycle.
RE: Variable compression
I think Saab's VCR engine with its hinged-block approach was a better system.
RE: Variable compression
Intake and exhaust manifolds that shift relative to the rest of the powertrain because they're attached to the cylinder head?
Sealing the two parts of the block together in a way that will last 300,000 km?
Variable-length timing chain?
RE: Variable compression
RE: Variable compression
http://www.spannerhead.com/2013/03/13/interesting-...
The movement of the head is very small, the cam chain or belt could pivot without any length change. The exhaust flex would be truly tiny if the pivot is on the exhaust side (unlike the SAAB), -much less than that from engine movement on its mounts and way less than exhaust track bounce under normal driving. Intake snorkel is flexible anyway.
In contrast, the Nissan monkey links look unduly complicated.
RE: Variable compression
RE: Variable compression
Its an interesting design that looks like it was a very fun project for that team.
"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin
RE: Variable compression
Bosch developing water injection for modern cars. Link
je suis charlie
RE: Variable compression
Very interesting gg, thanks for the link. I was wondering when interest in this approach would re-awaken in mainstream automotive thinking, following its abortive introduction by Oldsmobile in 1962 on their 1hp/cu.in. 215 CID turbocharged V8.
Automotive engines have been going down almost exactly the same development path followed by reciprocating aero engines; just several decades later. Of course, development of mainstream high power density aero engines stopped suddenly in the mid-1950s, due to the advent of gas turbines; but I don't foresee a similar cliff event for automotive reciprocating engines.
"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz