ditchyboy

I'm hoping to buy an impreza Sti blob this weekend and it was mapped by the previous owner to the current one but using bp ultimate.the guy who mapped it said it should be 330 but is 310 due to the crap fuel.the current owner uses v power but I haven't got that near me.i will use tesco momentum as I have one near me.
Basically is this ok to do or will it need a map tweak before I can drive it hard?
Thanks michael

JohnD

iTrader: (5)

If it's been mapped for Ultimate then it would be perfectly safe to use Momentum. Even better, get it re-mapped on Momentum and get the 330!

JohnD

Jolly Green Monster

iTrader: (4)

As John says.

Momentum is only a nats ..... Less than vpower power output wise

LuckyWelshchap

+1 defo !

(And more economical )

ditchyboy

So as its higher Ron than bp ultimate that's why it's ok.i take it I just have to stay away from normal unleaded.is it wise to carry a bottle of octane booster in case of getting caught out?would I have to drive it off boost even with octane booster or could it be driven normally.
Thanks again

chopperman

You cant over do the Ron, just under do it. But if you use 99ron instead of ultimate you may have more power to give if you get it mapped for the higher Ron. You wont cause damage using the higher Ron, but you could if you use a lower Ron than you're mapped for.

chopperman

To be honest i wouldn't trust octane booster and it can damage cats. If you have to use low octane fuel just drive off boost. Make sure you run at least 2 tankfulls of the good stuff before boosting again. This is to make sure all the crap fuel is out. There is no excuse for using 95 ron as just about evey petrol station have 97ron. So if you cant get 99ron, use 97 and drive off boost.
I have duel maps on my car. One is mapped for 95ron and the other for 99ron. I never use 95ron but i have the map should that be the only fuel available.

2pot

iTrader: (3)

For a daily driver - surely RON is always worse than better - bottom of the stations tanks/how long it has been in the tanks/watered down?
Why not map for 97. Then fill up with 97 or 99.
Is there an average performance reduction from 99 to 97? Or is it not that simple?

Jolly Green Monster

iTrader: (4)

Depends on power output level but noticable amount.

Vpower seems more consistent also

2pot

iTrader: (3)

Say 400bhp on 99. Would you lose.... I don't know...I hope I'd notice 5% loss.

Jolly Green Monster

iTrader: (4)

yep probably 20hp.. bp ultimate is particularly not nice in a subaru engine

chopperman

Yeah i've heard that said before, i wonder why? has it got a lot of ethanol in it or something?

JohnD

iTrader: (5)

They make a big deal about the cleaning properties of Ultimate. Maybe the Subaru bore/stroke, combustion chamber shape etc is sensitive to the additive package? I heard it's ok in EVO's?

JohnD

Jolly Green Monster

iTrader: (4)

No imho, its just a lower RON

chopperman

Isn't it supposed to be 98ron or is it just 97ron ?

It's funny, back in the 90's i had a motorbike (GPZ900R) that didn't run very well on Shell petrol. It used to leave like green enamel type deposits on the spark plug electrodes.

LuckyWelshchap

Well for me it's pretty straightforward.

I've been fortunate enough to get a GREAT Subaru.
I'm not going to throw an investment to the dogs.

It would HAVE only been run on V-power.

I did buy a very well endorsed octane booster, in case I ran short of a Shell garage.

Members of this community informed me that (Tesco) Momentum was an acceptable alternative (and they had used it), so I went for it, as a test.

Absolutely no problems with Momentum (I understand JGM's concerns about quality control, but it's NEVER been a problem with me/mine).

I still have the octane booster (NF Racing Formula) in case I get caught short/out.

But there's surely a Tesco within reach that sells Momentum.
(Mine does, but a bigger branch 9 miles away doesn't - how mad is that ???????)

JohnD

iTrader: (5)

Yes, 97RON but I wonder how the other 97 RON fuels eg Esso, Texaco, etc behave in the Subaru engine, by comparison. Have you mapped any using these fuels?

JohnD

Jolly Green Monster

iTrader: (4)

Texco and bp similar. Esso is alright.

ditchyboy

If it was mapped for ultimate I can use 97 Ron safely though cant I thinking about it?im going to use tesco momentum or v power but I live down on the south coast and there are less higher Ron pumps around.my work sites are in the middle of nowhere.