why would it not be 98 as the compression ratio is higher! Or have you no idea!
chris241,
Dec 19, 6:56am
i run 91 in 1999 vtr1000 and have done in all my bikes. I think 96/98 (or what eva the shit is ) is just a have ive never noticed any diffrence. I tried it in my 94 ss commodore with no diffrence at all. Its all in ya head
chris241,
Dec 19, 6:58am
in fact my commodore runs a nice clean looking pipe and thats on 91
carstauranga001,
Dec 19, 7:08am
No it's not in my head, it is fact. You will find Commodores are designed to run on 91. High compression motor bike engines are a totally different beast.
carstauranga001,
Dec 19, 7:17am
Actually, I just googled VE Commodore V8 compression ratio and it is 10.4 to 1. Specs also state recomended fuel 98 octain.
Edit. More googling and VS V8 has only 8.4 to 1 compression ratio thus you are correct to use 91.
chris241,
Dec 19, 8:09am
all im saying is ive tried it and noticed no diffrence in my bikes or cars. My current bike i tried it for a while then went back to 91 with no diffrence. Same when i had my 1991 zzr1100 tried it then back to 91 with no diffrence at all.
male_timaru,
Dec 19, 8:23am
Experiment all you like but in a bike using 12-14000 revs i would only use 98 (as mate who has done every test under the sun on his one did) and got the best results power, economy and smoothness from98
carstauranga001,
Dec 19, 8:32am
So with no actual knowledge apart from "trying on your vehicles" you posted in a way that sugested others should follow your experiance. Very dangerous advice IMO. You may not feel a difference but you will cause long term damage. High compression engines require high octane fuel. It's that simple.
kazbanz,
Dec 19, 9:20am
Ok guysI'm no ge wizz rocket scientist like you lot. But a couple of years ago I did have access to a pretty gee wizz type dnyomometer. (dyno). I was jetting up a race bikeand generally having a good ol time Interesting statistic from this. OnBP98 I got 2.5 HP and cleaner emmissions than on 91 octane.--Not a lot but the improved emmissions indicated long term it would be better for the bike.
skyline_guy_r34,
Dec 19, 10:49am
I remember being told that 95/96 octane gas really taps out at about 12.5:1. I had a bike with a compression ratio of 12.8:1. I was forced to use 98. I put half a tank of 95 in one day when i couldnt get ANY 98 anywhere. It was incredible what it did to the engine! Needless to say i rode it home and emptied the tank and waited for 98 to become available again before I went down with a gas can and got some for the bike
guider1,
Dec 20, 7:43am
My old '99 R1, which had around 12.4:1 (standard 11.8:1 from memory) ran on 91 fine. although I ran Av in it when on the track. Still managed over 300kph on the road running on 91 without problem & radared at 307kph (191.5mph) down the back straight of Puke on Av. (It's actually on TM for sale at the moment). Whether or not a high comp engine (within reason) will run on 91 is based on combustion chamber/piston design, & the 1000cc sport bikes have the perfect design to make big power on a low octane fuel. I've seen a 600hp 12.5:1 V8 streetcar run on 91 ok.
guider1,
Dec 20, 6:41pm
American Hot Rod magazine; His '93 Chevy Caprice wagon with 572ci big block makes 1740hp with 91 octane & recently ran a 9.57 at 163mph weighing 4850lb (2205kg) with the driver onboard.
guider1,
Dec 20, 6:44pm
Nothing ever has enough power. that's why I had the head ported & flowed & raised the compression on my old R1 then also fitted it with nitrous.
drog,
Dec 20, 7:05pm
Can anyone confirm that our 91 octane fuel 'recipe' is the same here as the USA!
lasertech,
Dec 21, 12:47am
Absolutely 98 from a performance point of view. We do tuning on the euro bikes, and although they appear to run fine on the 91/95 fuels, the ecu is compensating for the lower octane and reducing timing etc. 98 should be used on all performance engines.
guider1,
Dec 21, 7:43am
My old '99 R1, which had around 12.4:1 (standard 11.8:1 from memory) ran on 91 fine. although I ran Av in it when on the track. Still managed over 300kph on the road running on 91 without problem & radared at 307kph (191.5mph) down the back straight of Puke on Av. (It's actually on TM for sale at the moment). Whether or not a high comp engine (within reason) will run on 91 is based on combustion chamber/piston design, & the 1000cc sport bikes have the perfect design to make big power on a low octane fuel. I've seen a 600hp 12.5:1 V8 streetcar run on 91 ok. There are 1200 streetcars in USA running on 91. And dont give me "but their fuel's better" line. their 91 is an unleaded, low octane fuel for the general public just like ours is. Quote: Chevy High Performance magazine; Our 355ci mouse makes 765hp on 91 octane. Brett Kepner, ESPN2; The '69 Nova utilising a 427 Chevy crate motor & carbs with a Pro Chrager centrifugal supercharger astonished everyone with 8 second runs on 91 octane pump gas. Super Chevy magazine; When the F-2 Pro Charger was bolted on with 26-27psi of boost, this 91 octane (with NO additives) bad boy puts out 1160hp to the tires. Cant see too much wrong with it!
guider1,
Dec 21, 10:17pm
Each to their own. my Commodore with 11.64:1cr runs like shit on 98; it hardly even idles yet 95 is fine & still makes a ton of power. I personally reckon 98 is a rubbish fuel; it stinks burnt or unburnt & like I said, even with compression my car almost stalled the couple of times it's had it in it. 95 is sweet-as & churned out good HP numbers on the dyno. That's my opinion from personal experience with alot of different engines over the years.
mgmad,
Dec 21, 10:28pm
Higher octane fuel has better resistance to detonation, and higher CR leads to increased likelihood of detonation. Fact.
Dyno figures on the LS1 in my Commodore say otherwise, on 98 it cosistently produces more power and torque, 7kw more at peak.
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