**Hawk**

Hi all

Can anyone help. bought a subaru impreza wrx 2002 (52) collected a couple of weeks ago and have been using BP Ultimate Unleaded and I am finding that the acceleration between 4000 - 7000 rpm is not so smooth.

I know that the owner previous to me used Shell V-power but I am unable to use because the nearest filling station is about 25miles away.

Do you think its the change in fuel

Thank you in advance for your help on this subject

bugeyeandy

Most likely , for some reason a lot of Imprezas don't like being fed on BP fuel.
Try a couple of tanks of Tesco 99 or Shell V-Power and see if it clears things up, if not it could just be that it needs new spark plugs.

flashgordon666

tescos 99 cheaper then bp too.

**Hawk**

Both V Power and Tesco 99 filling stations 25 miles away.
How about esso super unleaded?

silent running

AFAIK both BP and Esso super unleadeds are 97 octane, whereas Tesco and V-Power are 99. If the car's standard it should be able to run on 97 octane super, and I hesitate to say it's just your fuel when it's such a vague problem that could be a number of things. But my advice is use up all your fuel, drive to your Shell station 25 miles away and brim the tank with V-Power. See how you get on. If it is the BP fuel (and I don't remember a single person on here ever having a good word to say about BP) then your long term solution may be to buy any old crap and top it up with octane booster.

dunx

iTrader: (3)

Bulk buy octane booster, I always carry some just in case I have to fill up with lower spec. fuel.

HTH

DunxC

caperbility

How does that work then Dunx?

I always use either tescos or shell but if i cant get it and i need some can i use normal unleaded and octane booster , just enough to get me home or to a tescos etc. Will a mix of that upset my car and how do you use it ie quantitys etc?
Many thanks

Henrik

iTrader: (5)

Before a remap, my car was very happy with Esso 97. It seems to have more go than the other 97's for some reason - i think this is down to the mixture of additives that they either do not put in or put in Other folks have reported similar experiences.

If I'm caught short between shell garages now, i try to find esso and use octane booster.

I.e. it will be absolutely fine on 97 esso unless it's been remapped for another fuel type, in which case you should try to stick to that fuel type.

dunx

iTrader: (3)

The ecu in modern Impreza's will work to achieve the best performance/economy it can, depends on driving style. My STI is ALWAYS run on the best fuel I can find, despite running reasonably well on the worst fuel money can buy.

Adding octane booster at a fill-up will allow the ecu to adjust the ignition timing to suit, whilst you are exiting the forecourt.
Different blends achieve different results, the one I use is one bottle per tankful.... easy, and buy in bulk to keep the cost down.

The crazy stuff i can get needs THREE bottles to a tankful, but that gets expensive long term, but I'm also not sure I want to mess about with methanol either..

DunxC

Henrik

iTrader: (5)

What OB are you using? I'm going to start using NF soon, but I'm having mine mapped straight after. Used a couple of bottles of millers up to now when i've had to use "bad" fuel.

Oh and the ignition timing... Are you sure that it adjusts up with fuel that is better than it was mapped for? I thought the ignition was set in the map, and then there's the IAM (ignition advance multiplier) that is used to modify it as you go along. As long as the IAM is at the maximum value, which it should be at the fuel it was mapped for (i.e. no det), how can the timing be further advanced?

I think different fuels feel different due to the "calorific value", i.e how much energy you get out of it when it's burnt, not the octane rating per se (again, as long as it's good enough).

Then again, i'm no mapper, so I might be barking up the wrong tree here