high performance engines hav higher compression ratio, thus u need ron97 for dis kind of compression ratio

I heard on bfm last week or so some caller said she sometimes fill up with ron 97 to 'treat' her car.. Got such thing ah? Car will be happier if use expensive petrol?

Nope. car will be happier if use recommended petrol.

The higher the octane number, the more compression the fuel can withstand before igniting. For example my car using RON 95 the rate is about 16km/l while using RON 97 can go to 18km/l. #kthnxbai

This
+ if majority of the time driving in city, stuck in jam, what is the point even if the so call "improvment" on performance is true.

Compression ratio is fixed..where can suka suka change wan.hhahaa
U mean air fuel ratio?

97 on the A5, 95 on my C200. after all those bullshit, i just have to pay less. happy man ayam.

Can change ignition timing based on feedback from knock sensor

Yeah but the question was change compression ratio. That is fixed mechanically

Hope your 2.0t ea888 dun start eating oil..hehee

This post has been edited by ar188: Dec 4 2014, 09:47 AM

If timing is retarded, ignition happen faster. Therefore piston travel shorter distance before ignition hence lower compression ratio

if your car compression ratio is low no need so high ron.
go check your car manual or brochure.

A5 eat more enjin oil, but then again, a visit to Autoreign solved everything.

p.s. firm got petrol subsidy and travel allowance. so, no pinch

My car stated the minimum RON is 97 and it is true that its deliver optimum performance than RON 95. how?

This post has been edited by merajey: Dec 4 2014, 09:54 AM

er.... u mechanical engineer? from where wan?

There is generally no significant benefit of pouring a higher rated petrol if your car does not take advantage of the increased compression ratio. People who claim that RON97 works wonders for their Wira/MyVi are probably trying to justify the extra cash they spent.

Wrong laaa... retarding ignition timing is not to lower compression ratio...
to lower the compression ratio the VVTi or iVtec or variable valve technology will keep the intake valve open much longer than its required so the mixture will reverse back into the fuel injector chamber thus lowering the compression ratio

this also works with retarding ignition timing to compensate for the low RON or premature ignition (Engine knock)...

but if your engine is design for Lower RON like RON91/2/5 no point pump 97 just waste of money only...

most of CKD cars are made for RON91 due to thailand fuel... (Thai sell RON91) so inorder for your car to travel to thailand and not dying there engine is made to lowes regional requirement hence in South east Asia is RON91... this is also why before RON95 petrol pump sell minyak merah (RON92)

Some europe car uses min 95 cause based on europe region where min RON is 95...

Japanese performance car usually go around RON97-RON100 eg. Type-R is RON98... but RON97 can laaa any below will kill your engine...

1. A higher RON that what the engine is designed for will NOT produce more power, the effects we feel is largely due to different additive packages for 95 and 97 at our pumps

2. No a car cannot adjust compression at all. Higher compression ratio requires higher RON because before the piston reaches top dead centre the air fuel mixture is already hotter than a lower compression engine. Take a very simplified example, two pistons traveling over the same distance 10cm in the cylinder. One has compression ratio of 10:1 and the other 14:1.

After 10cm travel the 10:1 compressed the air 8 times of nominal pressure, but the 14:1 would have compressed the mixture to 10 times of nominal pressure despite travelling same distance.

High compression = higher temperature = more likely to self ignite before spark from spark plug. Hence higher RON needed to withstand self ignition until the spark fires.

So why doesn't RON 97 give better performance in an engine requiring only RON 95?

simply because of the reason above, the engine needs to have the mixture NOT ignite BEFORE the spark, so 95 is enough to prevent that, putting 97 also achieves same results, hence 0 benefit.

Beep beep..fellow engineer passing through..just checking out how many mechanical engineers in /k..

Proton, probably 95 is fine.

Uni of Lolyat?