Ian Waller

Okay, I know that STi's are designed for 100RON fuel. And I know that to get the quoted power figures you will need to run 100RON fuel (or as close as possible, hence the octane booster).

But, my question is, do they really NEED it? If I run my STi on 97RON am I going to damage the engine, or will I just not have the max power possible????????

Ian
STi II

TRIGGER

I gather it is only the Version 5 that really had problems with the lower octane fuel, especially when pushed on trackdays. A few engines went bang apparently. Version 1-4 are fine with lower octane stuff. My version 4 has no problem running on normal ul but just has less power of course, although I nornally use super with booster for trackdays.

Ian Waller

I appreciate that this is a 'how long is a piece of string' question, but . . What sort of power would you usually expect to lose by running at 97RON?

Ian
STi II

Adam M

Ian,

my view is that if you have gone for a road car with this performance, you shouldn't cut corners in its maintenance.

it really should be run with octane booster.

Run it on 95 at your own risk. It mighjth be okay, it might not.

I wont run my car on less than super and octane booster.

If you are concerned, buy a knocklink and have a look at what is going on. You will know if you are in trouble.

Mike Tuckwood

Yes they do.

CraigH

Trigger,

Without sounding funny, I don't think versions 1-4 are "fine" on unleaded.

Think you're playing with fire running it that way......

Bad Bads

When I bought my Sti3 the previous owner ran it on UL.After a trip to PE Mervyn advised me to run it on at least SUL.After changing over I did notice a slight difference.I now run the car on SUL+ Miller OB and it has never felt smoother,whether it raises the BHP by much I do not know but I am very happy with the way it is now.
Cheers Paul.

TRIGGER

Craig - 'Fine' is a relative term. Lower octane fuel under normal driving conditions (not redlining every gear change) doesnt destroy engines in these cars, but doesnt give such good performance. On track I would always use octane booster anyway.

Ian Waller

I was not suggesting that I would run the car on 95RON, I was asking about 97RON.

Considering that in everyday driving it is, almost, impossible to use STi performance on public roads. Is it likely to damage the engine using 97RON. I appreciate that under the stress of a track day 100RON would be highly advisable.

Ian
STi II

Adam M

It is better to run on higher octane, but not too high.

Itr is wrong to tell people they will be fine in day to day driving.

All in takes is one full throttle over taking manouevre, a little bad det, and bang it could be gone.

you have to remember what fuel to have in there and drive accordingly.

Wet cold evenings will help you for example.

As I have said, on my standard ecu I would not run a 22B engine at less than 99 ron, unless I had to. inwhich case, i would put the minimum fuel in and drive like there is a big spike pointing out of my steering wheel, until it is all gone and some healthy 99 is back in there.

That is if not running an aftermarket ecu.

I used to run the wrx with just 97 day in day out, and had no quarms about booting it, but that was my luck, you might not have the same.

Just be warned.

slippyr4

Hmmmm. Lets not forget that scooby ecu has detonation sensing, and reduces boost accordingly & timing. Lower octane fuel is going to bring your max boost down.

One thing that helps a lot in counteracting low-octane fuel is improving intercooler efficiency. Perhaps fitting bigger intercooler, perhaps FMIC.

Shaun

Yeah you are absolutley right, but it won't bring it down enough to compensate going full chat on a 276bhp engine designed for 100 ron, when you are using 97 ron at 7000rpm. 3 ron may not sound alot, but when an engine is mapped for that limit, it's a huge amount of advance.

You'll be WELL surprised how much ignition has to be taken out of a car when changing a map from 98 octane to 97 octane.......the power loss is equally huge!!!

As has been said.....buy a knocklink and see for your self.

Shaun.



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