another dumb Q from the sig- PETROL

Ive got a Suzuki Ignis Sport vvt. ( a what i hear you ask!)
Suzuki actually recommend using higher rate fuel Optimax etc. in the
handbook. Not sure other car manufacturers do that as standard.

[BillyC]

I think anything with Variable-Valve-Timing is to a certain degree, be abl to adjust the compression of the engine.

Couple this with Lambda sensors to measure the burn efficiency, electronic ignition to adjust the spark timing, FI to adjust the fuel delivery, and anti-knock sensors to make sure nothing's going wrong..... then a high-octane fuel should give noticeable performance increases.

The Subaru Impreza Turbo has all of the above (except perhaps the VVT). The difference between Premium Unleaded 95 RON, and Optimax 98.5 RON; is over 40 bhp!

Bill, Cheers for that.
Whilst not quite in the same performance league as the Subaru, the Suzuki is still a fairly highly strung motor in the scheme of things. (0-60 in 8.5 secs from 1.5 litre engine)
So will probably benefit from Optimax and the like.
Strangely enough, i'm only putting the better fuel in the SV at the moment!

cheers guys

very informative

very informative indeed. I wonder what the supermarkets claim about their fuel, and what it really delivers or contains...?

there is certainly a difference between Optimax and Ultimate and lesser fuels. my bike just feels better, it seems to run sweeter.

The additives they use are expensive, thats why the supermarkets can offer cheaper fuel.

Many people will tell you it is all the same, although many tankers will operate from one refinery, there are still special blends made for companies.

Shell will evaporate a lot faster than Asda.

MCN did a test a few months back and they agreed with me :P

Believe it or not, my bike sounds different with std fuel... I always try and run with Optimax where possible (I have a number of shel garages fixed in my mind for regular trips). When running with 95 RON the exhasut note tends to be "raspy" rather than a smoother sound.

It took me a while to figure it out, but a couple of weeks ago it was making the raspy sound when I refilled with Optimax. As I was riding to work I noticed the sound had changed and thought about the fuel. To prove my theory I let the tank get very low (just under 15 litres went in) and low and behold the sound was back.....

I guess it's something to do with the way it burns coupled with the fact that my bike really over-fuels on roll off (and it tends to backfire less as well).

.

further reading - some of it interesting

http://www.elektro.com/~audi/audi/toluene.html

"For turbocharged or supercharged engines, insufficient octane will also lead the engine management system to curtail the amount of boost which in turn defeats the purpose of these engines" - Going back to the subaru impreza turbo +40bhp

Well if anyone has the time/money grab one of these and do some research http://www.sinar.co.uk/docs/portable_octane.pdf lol

[embee]

Originally Posted by adam

further reading - some of it interesting

http://www.elektro.com/~audi/audi/toluene.html

"For turbocharged or supercharged engines, insufficient octane will also lead the engine management system to curtail the amount of boost which in turn defeats the purpose of these engines" - Going back to the subaru impreza turbo +40bhp

Many moons ago I was slightly involved with someone doing moped racing, which was supposed to be as cheap and cheerful as you could get, buy a 50cc moped and do 6hr endurance races as teams of 3 or 4 riders.

Some sponsored teams started getting serious (dealer sponsored 2-strokes), so we thought we ought to retaliate. We had a Honda SS50 (4-stroke), and nothing in the rules outlawed pressure charging, so on went a belt driven supercharger (we used an exhaust air-injection pump used for emission control on bigger engines).

After eating a few pistons+rings, we started using 50% toluene. Since pure (laboratory) toluene is quite expensive, we hunted round and found some commercial paint thinners which was 95% toluene and cost a couple of quid a gallon.

One race a rider forgot about the reversed gear lever, over-revved it, so it came in, had a replacement engine fitted, went back out and finished sixth (it had such a big lead when it blew).

On the right gearing it would do 95mph, we reckoned about 15BHP or 300BHP/litre.

Note you should not use paint thinners as a road fuel, or you'll have lynw after you for the duty!