Going to look at a 98 STi tonight and a 99 STi over the weekend.

The question is, how stupid is it attempting to run one on normal UK fuel? Can they be mapped to run on the lower octane and at what expense on power? < Would it in fact be better to get a UK car and modify it?

Reason Im asking is Im moving to deepest darkest highlands with no access to Optimax. Does 95RON and octane booster come anywhere near to providing the same octane as a tank of optimax?

Thanks for any advice, but its either this or get a 99 UK car and tinker with it.

Rgds


NJ

 

Running an Sti on normal fuel is begging for trouble unless you have it mapped to suit. It is recommended to even add octane booster to optimax so dont even attempt to use normal stuff!

 

what do you mean by 'normal' ??

Optimax is generally fine (get a knocklink before running on optimax only though) or add octaine booster for piece of mind.

Plus, just to throw another item into the equation, I hear that the new Shell 101 ron fuel will be released some time this year. Perfect for all imports.

*edited due to disgracefull spelling : )

[Edited by Gedi - 7/24/2003 8:59:31 PM]

 

I assume he means 95 RON being normal.

 

The other thing to consider, if you're that far out in the sticks, is that petrol degrades slightly over time.

Thus, if you use 95 RON from some backwater village pump that's only resupplied once in a blue moon, it's likely to be even lower quality than the stuff you'd get from a large city Supermarket, making the need for knock monitoring, and either a remap or OB even greater.

[Edited by greasemonkey - 7/24/2003 5:45:25 PM]

 

Think about adding water injection IMHO.

 

Ah Hi John, was going to email you.

Whats the score with remapping an ecu for a lower octane fuel?

When I say highlands - I dont mean they only get one fuel delivery a year guys - theres just no Opti as the local garage is a Texaco and as its small - no SUL.

What octane will 95 go to if you use booster?

Cheers again

NJ

 

You can get 95 up to about 97 using 1ml/litre of NF, but I recommend using 2ml/litre of NF, or seriously thinking about water. You need a knocklink anyway, and if relying on a water system get one of the ones with a flow monitor, or at least a low level indicator.

Remapping to 95 RON is a miserable task, especially on a car that is mapped for 5-7 RON higher You take ignition timing out by chunks. Also it is less tolerant to higher boost and being lean. On a highly strung STi engine, low octane is seriously bad news, remapped or not. The result is a miserable and slow car.

I strongly advise you to work on anti detonation measures rather than just rely on an ECU.

98 ECUs cannot be reprogrammed, so you would need a standalone ECU if buying a 98 car.

Things you can do to make more power at low boost:

Bigger turbo
Bigger intercooler
Water injection
Octane booster
Exhaust manifold
Full exhaust system
Inlet pipe and induction

Mapping an ECU can only take advantage of what is there.

Detonation thresholds will move in your favour with the mods above, and against you with lower octane fuel and higher temperatures/track use/heatsoak.

If a car dets, then you can retard the ignition a bit to sort it, but usually it is as well to richen the fuelling and lower the boost as well, as all of these have a little effect.

For a given spec of car it is the mapper's job to find the best combination of fuel, ignition timing and boost. There are no free lunches, you have to modify the hardware more in your situation to compensate for the lower octane, or run plenty of octane booster.

 

Hmmm

Sounds like I need to source some decent fuel then and forget a remap type option.

Id be happy with SUL and NF I reckon but Ill have to investigate.

Or bite the bullet and buy a UK car

Cheers for some exellent info guys. Thanks John

NJ

 

The UK car would still be slower if you remapped the STi for 95 RON. But as well as remapping it I would think about the other stuff too.

 

Sorry I meant to just run it on 95RON without remapping for it.

So just in standard form with no mods

A lot of it depends on the availability of fuel so if I can find something nearby Ill plump for an import.

Thanks again

NJ

 

If you want no hassle/worries and don't want to modify it get a UK/Euro.

If you want to modify the car then start from an STi as a base to modify. The octane issue can be worked around, people do run monsters in the Highlands

 

Cool

Ill not let it put me off. The car I looked at is a beauty so Ill have to see what can be done.

Rgds

NJ

 

Surely the only monsters found in Scotland are in the lochs?

 

Some of the women are a bit ropey

IMHO - I wouldn't touch A V5/6 sti with a bargepole unless: It had come fresh off the boat, which would mean I could replace the MAF with a better one, get a remamp done, and possibly a better fuel pump. Only then would I sleep sound at night. The amount that go bang, including P1's is scary.

I would have more faith in a 98 STi R (IC spray) may be wrong, but not as many of these seem to go pop.

MB

 

OOh bl00dy hell - right can of worms

Im taking cover

NJ

 

The burds up here are OK I met one and stayed

 

MB