Sparetire

I have yet to see an engine detonate due to an excessive VE. I have seen it happen with a high DCR.

Full_Tilt_Boogie

iTrader: (1)

*Translated for emphasis of absurdity*

fmowry

iTrader: (8)

I'm pretty sure you don't realize that JKav knows his ****. He worked or works for Garrett and was behind the creation of the Disco Potato you all know and love.

Feel stupid yet?

Frank

gospeed81

iTrader: (51)

Um...whoa there.

I got a pretty damn good grade in Thermodynamics...JKav is right ******* on.

Sparetire

Then I am confused. I hear engine builders and tuners talk about DCR all the time. How you can get away with a higher static comp if you have a mild DCR. So while you cannot measure DCR like you can SCR, it certanly matters. Just as you cannot measure HP, only TQ and RPM. Technically it does'nt exist, but it matters and is a characteristic of an engine affected by valve timing, SCR, etc. There is a pretty good Wiki on it thats probably better than the link I posted earlier.


Is it essentialy the case that by lowering VE through cam timing at peak TQ (maybe some overlap or something?)you can lower the propensity to knock? And is DCR basically a way to express that as a single easily managed number? Thats what I thought anyway....

Edit: And I got an A in Thermo. Because I am the man.....and because I only had two other engineering courses that semester........

gospeed81

iTrader: (51)

DCR is a way for those familiar with motor geometry to approximate one of the many aspects of volumetric efficiency.

It is trying to say that real compression only occurs after the exhaust valves close, when in reality this is just a measure of exhaust cam timing, which affects VE.

Other considerations are scavenging, intake cam timing, intake manifold design (helmholtz), head flow, exhaust, etc.

VE and CR can be used in thermodynamic formulas to describe the power a motor makes.

I'm not sure how you'd do the same with SCR and DCR...

Full_Tilt_Boogie

iTrader: (1)

Sense of humor in this thread = none.

mgeoffriau

iTrader: (7)

I blame Stephanie Turner.

Pitlab77

iTrader: (3)

I thought the only difference was the intake, cam, and the fact some of them used a different exhaust manifold (4-2-1) than what we used.

Faeflora

iTrader: (2)

No, you smoke **** and you r dum. That is "you r" not "your" or "you're". Two out of those three are correct.

Jkav is one of the few authoritative hard-tech engineering members here and we don't need your dumb internet jockey *** chasing him off. Input from members like him are what makes this forum good.

Sparetire

Stop being a racist *******.

Sparetire

Makes sense. But DCR seems pretty useful to me because it does give you a hard number that takes pretty much everything into account and gives you an idea of an engines propensity to spark knock. Its not as theoretically correct as looking at VE and CR etc, but it seems like a pretty expedient little number to me. My guess is that DCR and the results of a compression test would correspond fairly closely compared to SCR and a comp test.

Neddy

Old thread I know.

Can anyone CONFIRM if JDM VVT camshaft is different? If yes, what is there difference?

Other info appears correct in that the JDM does have a better intake and higher comp.