VR4 petrol do I use 91 or 95

[Subaru ETA]

what they said!

[Slam Jay]

Whats the necessity of disconnecting and reconnecting the battery after the first fill of 98? The previous owner of my VR4 used 91 for some misguided reason, and its had two fills of 98 since I bought it. Is it still a good idea to disconnect and reconnect the battery?

[Ryan]

Whats the necessity of disconnecting and reconnecting the battery after the first fill of 98? The previous owner of my VR4 used 91 for some misguided reason, and its had two fills of 98 since I bought it. Is it still a good idea to disconnect and reconnect the battery?

Resets the ECU and clears things like det count if it has been run on poo fuel in the past. Essentially a clean slate to start with again.

[KiwiTT]

Some NZ members (KiwiTT I believe) use 95 in the standard boost application.

I have now reverted back to 98 as I noticed no significant benefit by trialling the new Shell V-Power (95).

[Ryan]

I have now reverted back to 98 as I noticed no significant benefit by trialling the new Shell V-Power (95).

Have you noticed any benefit since you returned to 98RON?

[bradc]

You'd never notice any benefit by moving from BP 98 to some over-hyped 95 octane that has nothing to do with the fuel that they put in F1 cars

[Ryan]

If the V-power available here was the same as the V-power in the Eurozone it would be surprisingly close to the composition of ordinary petrol but the fuel compounds in F1 are more tightly controlled.

[raph]

used BP 98 in all my modded cars, 99 ultimate when at ARAL and V -power 100 when i was feeling like throwing some euros around

nothing less than 98 tho

[WildCards]

I wasn't really sure whether to start a new thread with this, but I guess it's relevant information.

An interested thread over on PH has lead to a few comments, if true make for interesting reading.

The thread:
http://www.pistonheads.com/gassing/t...uel?&mid=59876

The comments:

[Bloke 1]
Its a complicated business, for turbo cars you want stability which Tesco 99 and Shell Optimax / V power whatever its called offer, this is easily measured if your in a tuned car with knock detection, these two UK fuels work well. BP Ultimate is crap for turbos it doesn't allow the ignition advance that the tesco or sheel allows, but apparently (so I've read -don't know if true) the BP stuff has a higher calorific value so the burn is supposed to provide more energy

[Bloke 2]
Generally speaking the calorific value of the fuel is inversely related to its octane rating. Longer-chain hydrocarbons have higher calorific value but lower octane rating - see LPG (high octane, low calorific value) at one end of the scale and diesel (high calorific value, ruinously low octane) at the other. Many octane-boosting additives are hydrocarbon molecules with added oxygen which also gives them a low calorific value - in effect they are partially oxidised before they even get near your engine.

[Bloke 3]
Shell fuel has a higher calorific value than Tesco/Greenergy 99RON. The ethanol reduces this, whilst upping the octane: thats why it better suits turbocharged cars which derive a greater benefit from the increased advance.
....
Id say that Optimax/V-Power was better in theory, but Greenergy99 seems to suit some turbocharged cars better in practice.




Interesting stuff given that alot of folks on here use either Tesco99, Shell V-Power or BP ultimate. I don't know how this info converts to NZ though.

[elnevio]

Not looked at the actual thread - but I agree with all of the comments above!

[andydckent]

IMO Tesco 99 seems to work better than Shell V-Power

[sampsulo]

*scratching head and wondering if ordering the VR4 to Africa is the right thing*

[Beastlee]

Guys I've run mine on ARAL (BP) Ultimate 100 and V-Power 100 since arriving in Germany in Oct 07 and I woul dsay that after trying both with varing driving styles that the Shell was better fuel. My car gave less knock and more MPG on Shell than the ARAL every time, so much so that I haven't put ARAL in for about 6 months now.
I still get the occasional knock count (up to 80 max) but I never get any drop in the octane level. My knock seems to come at odd points to oso I'm not even sure it's anything to do with the fuel or even real det over a knocking crossmember, it's certainly more to do with the 13psi I run than the fuel.