Lol...my bike 11.0 to 1 compress ratio and use Ron97 every time i fuel it up..

go wikipedia and do the formula calculation.. check manufacturer specification for compression ratio (I hope manufacturer dont lie their compression ratio)

my savvy state use ron 95 above only

Already stated the formula there.

I think you think too much. It wont affect your gear box la bro. Doesn't make sense at all. Use logic instead of "i think my car... no power la... bla bla bla...." Give your car service regularly, gear oil, engine oil and etc.

He's asking how you come to the conclusion that compression ratio directly determines the RON usage. The site does not explain that because compression ratio is just a static component measured at TDC. Static compression ratio alone does not determine the RON usage.

Ignition timing plays a bigger part as the more aggressive the timing, the higher the RON is required to prevent detonation even though there is no change to the static compression ratio.

As for CPS lower compression ratio, that is not due to reduced timing as stated by you.



Every engine can only have 1 static compression ratio as that is determined by the shape of the piston. In the CFE, the piston is changed to reduce the compression ratio from 10.1 to 8.9 without changing the length of the conrods. Ignition timing DOES NOT change static compression ratios. Therefore the campro CFE static compression ratio is 8.9 and not a variable 8.9 to 10.1. THis is static compression ratios we are talking about, not dynamic. That would be another story and another topic.

This post has been edited by sleepwalker: Aug 2 2012, 12:51 PM

The tric to reduce compressio ratio is directly invilve in variable timing where the valve maintain open in the inlet to have flow back hence reduce compression ratio and save fuel each piston has a fix compression ratio but by retarding the inlet valve longer the mixture will flow back and reduce the compression ratio hence this is how knock sensor work.

Then you are talking about dynamic compression, not static compression anymore. Just like how a forced induced engine has a much higher dynamic compression ratio even though it has a lower static compression due to the fact that more air and fuel is forced into the combustion chamber. However, this does not change the fact that the STATIC compression ratio remains the same throughout the whole process.

It is not a trick. It is your lack of understanding what Static and Dynamic compression ratios are. You do not change static compression ratios by changing valve timing and lift duration.

somehow using ron 95 car , feels like no power .. lol

psst... let me tell you a secret... It's in your brain.... it is not REAL......

your car RX8, of course la

when its on 2 cars , it real all right ..

Yes agree with you the compression ratio pretty much remain the same since the cylinder length is the same (unless some genius invent variable cylinder length management haha not possible)

Alot of new car come with hi tech stuff to varies cylinder / varies valve / retard ignition / and with the new Prius engine even make a normal otto cycle engine become atkinson engine.... simply by playing around variable valve / retart the valve / etc etc

Psstt... another secret... your right foot your right foot...!!!

hahaha actually it is very hard to determine by feel... unless you dyno your car lor...

here is the video again

watch this video

http://youtu.be/dDHwCWdrtdg

dunno la , as long the car does not blow up on me i don`t care ...

dont say dunno lar.... cannot ignore your feel one... very bad for karma hahaha

Yes but we are not talking about those engines are we? The word STATIC means non-changing. If an engine has changing ratios, they'd most probably call it..Variable Compression ratio (yes thank you captain obvious..)

And your reference again to otto cycle engine is still not related to STATIC compression ratios. That is dynamic compression ratios.

Please understand the fact that the calculation of the static compression ratio comes from simple volume mathematics. Don't look at the formula in wiki as that would confuse you into thinking that CRs are complicated stuff. It is just a simple volume of the whole cylinder when the piston is at BDC (bottom dead center) plus the volume between the piston and engine head at TDC divided by that same volume again at TDC.

Once you understand that, you will realise that no matter what you do with cams/lifts/valves/duration/etc etc, you will never change the Static CR. Confuse yourself Static CR with Dynamic CR.

I also feel RON95 no good for my car...

Maybe u drive Insight u dont see any difference cause its already low performance anyway?

Google: Mazda CX5 Compression Ratio, Fuel RON requirement.

/Argument