Why you should use Hi-Octane Fuel

[KiwiTT]

I watched Fifth Gear the other week and they compared Standard 95 with BP Ultimate and Shell Optimax. Upgrading from 95 to higher octane has little effect on power & torque, with non-tuned engines. However, on tuned egines it added about 10hp, but when used on turbo'd engines (WRX) even more so, it added over 20hp. So it is worth the hi-octane on our turbo cars.

I have also noticed a 10-15% saving on fuel economy, which more than makes up for the price difference.:scholar:

[Wouter]

And yet.... when I had the Spazda, I found that the higher octane fuels had more affect on performance that with the VR4.... or at least it feels that way!

[djb160]

whats the huighest octane we can safely put in, 98? 100?

[Gly]

98 is the highest we can buy,
there jap imports so are made to run on 100 octane unleaded

we could buy race gas or av gas, but its expensive and you need a race licence to buy it lagally, also the lead in av gas will wreck you EGO in no time.

[bradc]

wouter, thats because the mazda had no power to start with, so it would have been more noticable :)

djb, the jap's run them on 100 octane, so 98 is perfectly fine.

[djb160]

Whats the difference between avgas and 100 octane?

[Gly]

av is 105 octane leaded gas, not good for our motors,

100 octane is unleaded and we cant get it here anyways

[Subaru ETA]

guy at work buys drums of av gas for his trans am... i ran a tank to race my mates silvia. it gave mre power but it spat flames and sis all sort of stupid ****... the plugs were pretty rooted after aswell...should prob change them... ended up with big black mark up the rear bumper too from the exhaust

[rayray24]

I was to the understanding that 98 is cleaner for our motors! 95 or below leaves crap in the fuel lines etc..! I felt a big differnce in my old vr4 when i was swaping from 98 to 95 (not to many places in wellington have 98)!

[Subaru ETA]

running 91 causes a huge lack of power and economy. the engines are tuned for 100 octane so 98 is what they should run on to stop detonation etc... if it were not for the knock sensors they would ping like nobodys business but the ecu alters timing etc to compensate

[bradc]

I haven't been able to tell the difference between 95 and 98 personally, but I'll keep filling up the white one with 95, and the purple one with 98.

[Subaru ETA]

haha do you have the purple one back yet?

[bradc]

nope...

[Subaru ETA]

so what you should have said was "one day ill put 98 in my purple car, when it sees the light of day again" :p whats the progress on it anyway?

[bradc]

not too sure, I haven't spoken to them for about 2 weeks, I've been really busy with my new job. As of 2 weeks ago they were fiddling with the ecu still.

[rayray24]

Dude it better be worth it! Drags or track??

[bradc]

both....on the road ;)

[Kenneth]

av is 105 octane leaded gas, not good for our motors,

100 octane is unleaded and we cant get it here anyways

avgas shouldn't be bad for the motor, it will just degrade the Oxygen sensor prematurely.

Bosch rate their wideband oxygen sensors for 20,000KM on leaded fuel, but 160,000 on unledded.

[mpau009]

it spat flames and sis all sort of stupid ****...

You mean like this... I cleaned my car on thursday and that was spotless, drove to Taupo for the Allstars and back today, it was fine on the open road, but back in the city it popped and spluttered itself to this. And thats on 95.

Of course 98 will get more power, and be safer under higher boost, but its still only going to be as good as the tune.

I'm a little dubious about the ECUs ability to do anything of use power wise with increased octane. When i put the octane booster in for the dyno day, which was supposed to be 105+, and all it did was fly out the back:thinking:

[mattpage]

Anyone know what rating bio ethanol is? We are starting to get it here in the UK, and I know its a higher octane than petrol.
Good thing is its compatible with unleaded cars, although I think an ECu remap is needed to get the best performance.

[mattpage]

I just looked it up..
RON =129 - Exiting stuff! :D

[Gowf]

At the end of the day, if your car isnt mapped for the octane of fuel your using you will feel little difference. The higher octane fuels will reduce knock as youve said, but not increase power unless you map for it. I have a knock link installed in the vr4 and it shows some interesting things. With optimax you get no knock at all, total super shows a little bit, but esso super does actualy knock when driving hard. Ive not used any 95 RON in the vr4 but can only assume that it will knock. Didnt know they were designed for 100RON though, that is quite interesting. You can also buy various octane ratings of fuel. Carless fuels, will sell you drums of 103RON for around a mere £3.00 a litre. Fine for a 40 stage miles but not too much use on the road

[djb160]

Theres a little challange petrol station in Nelson that sells 100 octane, you need a racing licence or something for it.

[rayray24]

True that there's also one in hastings that sells 105 octane and all you have to do is sign a bit of paper to say that they take no resp. for damage to car!!!!! $2.35 a ltr thou!

[Eurospec]

At the end of the day, if your car isnt mapped for the octane of fuel your using you will feel little difference. The higher octane fuels will reduce knock as youve said, but not increase power unless you map for it. I have a knock link installed in the vr4 and it shows some interesting things. With optimax you get no knock at all, total super shows a little bit, but esso super does actualy knock when driving hard. Ive not used any 95 RON in the vr4 but can only assume that it will knock. Didnt know they were designed for 100RON though, that is quite interesting. You can also buy various octane ratings of fuel. Carless fuels, will sell you drums of 103RON for around a mere £3.00 a litre. Fine for a 40 stage miles but not too much use on the road

This is pretty much on the buttons.

The higher the octane you can put in there, the lower its propensity for pre-ignition. Also the rest of the composition of the fuel is important in terms of adatives. You are looking for a clean ignition and a controlled flame front with an even speed.

In general terms, the higher the octane, the less knock you will see, but like Gowf, i also did a test between fuels. This was between Tesco's 99 RON super unleaded and Shell 99 RON 'new optimax'. I expected the same results between both fuels, however, in an EVO6 observed zero knock on optimax, but a little with the Tesco fuel. I put this down to the different addative package.

For those of you who really want to rinse the last bit of boost out of those turbos, i use Sunocco GT plus, which is a 109 octane unleaded race fuel. Its 4.5% oxygenated and has a very good addative package. Fair enough, my gto has a 'built' engine, but i can run that right up beyond 30psi of boost and zero knock!

Cheers,

Ben.

[Kieran]

MMmm! On fluke's website, that works out at £2.85 per litre! Zoiks!:speechles

[d i c k i e s]

i might start using 98 from now on. only use 95 cos thats all pac n save can afford. (hahaha) using discount vouchers. love the six cents.

i get all the black soot all the time, (95 Premium) i only get it when i put the foot down. look back in the rear view mirror and u see a lil cloud of soot or whatever coming from the exhaust. it then ends up on the body of the car. (annoying when it comes to washing.)

[Rambaud]

Filled up with Tesco 99 RON a couple of days ago. But only driven about 20 miles, so a bit early to say - initial impression is that the car revved a bit more freely.

Previous tankful was BP Ultimate (97 RON). Over 325 miles, the average fuel consumption was just under 33 m.p.g.

Previous owner had used only 95 RON. :(

So I think it will take a few tankfuls before the ECU re-sets?

[bradc]

Rambaud, run two tanks through it, then reset the ecu by disconnecting the battery terminal for 5 minutes

[djb160]

I thought it was agreed that for non turboed cars 98 probably wouldnt offer any benefits except a cleaner healthier engine

[bradc]

his car is a GDI thought which loves 98+ octane petrol

[VR4 MAD]

Here's an interesting little bit of info regarding Octane ratings from LTSA site



Fuel myths & tips

The truth about octane numbers 91, 95, 96 and 98.

Fuel is rated according to its level of octane.
The octane number (or rating) is an indication of how much the fuel/air mixture can be compressed in the engine before it spontaneously ignites (i.e. the fuel ignites before it is lit by the spark plug). The higher the octane, the more resistant the fuel is to detonating early.
You need to use fuel with an octane rating that suits your car’s engine. If you use a fuel with an octane rating that is too low for your engine, you will get ‘knocking’ or ‘pinking’. In severe cases, this can lead to engine damage. Some high performance engines are very susceptible to knocking because they compress the fuel/air mixture more. These engines need higher octane petrol to prevent this.
The octane number is not a measure of the energy contained in the fuel. High octane fuels have the same energy per litre as fuels with lower octane numbers. If an engine is designed to run on low octane fuel, there is generally little or no benefit in switching to a higher octane fuel.

Note: the section I highlighted red. Many people equate higher octanes with higher power. This says that's NOT so........interesting. :speechles

Comments guys (and girls).

/toycar

[bradc]

yeah, always knew that. Of course if you run 91 octane on a VR-4 it will detect detonation, and retard the timing, which effectively reduces power by a huge amount.

[VR4 MAD]

yeah, always knew that.

Yeah, but alot of 'ordinary' people don't.......... and think that if they put 98 into their Morrie Minor it will become a fire breathing Ferrari. /pan

/toycar

[djb160]

it wont ???? lol

[Kenneth]

it wont ???? lol

It will if you add a flux capacitor....

[bradc]

got two flux's in my leggie, anyone keen? no part trades accepted, no returns incase you're too much of a ****ing dumbarse to get it working

[VR4 MAD]

It will if you add a flux capacitor....

Well to a De Lorean............maybe. To a Morrie.......well no, not sexy enough.

Seriously though, because AV gas and other racing fuels all have higher Octane ratings, un-informed people think its that which gives it more power, but the higher octane is required because race engines have higher compression ratios ...generally speaking.

/toycar

[rayray24]

Well you learn something everyday! In my case most days haha!

[d i c k i e s]

well this is what ill do.. ill try out 98 for a week or two? see how it goes.