I'm well aware that running an STI on 95RON is bad news, and I understand that the ECU reprograms itself, with the consequential loss of up to 25 bhp. To reset the ECU, which of these old wives' tales is the best method.
1. Unplug the battery lead for an hour, then fill up with 98RON then go for a blast down the motorway with four up (while retuning the radio presets)?
2. Unplug the ECU (where is it?)
3. Remove the ECU capacitor and pop it in the freezer overnight?
Lastly, has anyone tried a bottle of octane booster (£5) instead of using 98RON (an extra £9 per tankful) - or both, to reproduce 100RON?

I have been through this ECU reset theory with my mechanic (Dave West of Risboro 4 Wheel Drive) and he states he cannot find anything in the Subaru diagnostic tool to "RESET" the ecu. He can clear the error memory and thats about it!! He showed me and I couldn't see anything relevant either.

As for option 1 - how do you stop your Thatcham class 1 alarm from sounding, as it will do when the battery is disconnected? Apparently my alarm will continue to sound under it's own power for up to an hour, even under water.

We mix Av-gas 50/50 with our 96 RON to get closer to 100 RON in NZ, much cheaper than using "104+" octane booster. I've changed my ECU for a "Possum-Link" laptop programmable model. Sells for NZ$1200 (400Pounds).This can adjust everything incl boost,map,ignition,fan temp!...and makes the air-flow meter redundant.

Sean at Lancaster told me to remove the battery lead for four or five minutes, find 4 heavy set rugby players and a hill, put the rugby players in the car, and my foot flat to the floor.

He told me his Select software let's him reset it more easily, but the result's the same.

Rob.

Stick the alarm in "Valet mode".
Find a stretch of private road.
Drive like hell :-)

My battery was disconnected for 2-3 hours as Peter Croney of Scooby Sport was busy dealing with more grateful customers!
I drank coffee and leafed through his stash of glossy magazines....
Australian WRX magazine is a standard for true grip to aspire to!

The immediate effects of SUL reset ECU were apparent just rolling along in traffic.

Once the full boost runs were completed the car went back to being scarey!!!!

STi performance and pistons for that matter do not appreciate NUL

For over a year the "ECU myth" was discussed.

In my experience it is an essential procedure if you ever run out of SUL and have to poison your car with NUL

My experiences make me believe otherwise, Anders.

I have been forced to run my car (an

From my experience I have to agree with Mark. I run my STi4 on both NUL (driving in fourth round London, long motorway treks) and SUL (blasting around Cumbria).

My dealer has stated that the 'reset' thing is a myth and until someone can show me results from a rolling road (same tank of SUL, before and after reset) I tend to believe him.

The is certainly likely to be a psychological effect where one makes the change then EXPECTS it to make the difference. I would question whether anyone can really tell the difference of a relatively small percentage drop/increase in power in normal - ie non-timed track driving. My experience on the track shows that UK cars and STi's are relatively well matched below 80mph and it is only over 100mph where the extra power shows. That is with a difference of 60bhp!

Time will tell.

I have the next dyno day to check the figures.

Of course this will only be a relative test as the weather will be better.

There is no point arguing with O as he is always right.

Thanks for your comments, but going back to the original question about octane boosters, has anybody tried them? There are three that I've heard of: Mega Power, Turbo Boost and Wynn's. They work out at around £5 per tankful (as opposed to £9 extra for SUL) and increase the octane by 2 to 5 points. They are lead free.

there is another octane boosters
it called Pro Boost (silkolene)
its use bij us in the race to sroke and four stroke engine
price 10 pound /litere
its enough for 300/100 litere 3%/10%
and increase the octane by 7 to 12 points
if use to much its damage your engine

ECU reset works a treat !
Last Weekend had to stick £10 of UL to get home.
Re filled with SUL on empty. The car felt very flat above 4500 revs.
Disconnected battery for 1 hour reconnected battery drove very quietly to the garage filled up with second tank of SUL drove very quietly to the Motorway then went balls out for 30 seconds using the brake a bit.repeated a couple more times.

What a difference car pulls and pulls right round to 6500 no flat feeling or nuffink just a huge smile on my face http://bbs.sidc.co.uk/smile.gif)

Its free to try so just give it a go ! JUST DO IT
(But put a couple of tanks of SUL in first.)

For number 3 - Surely if its hard to find the ecu - finding the capacitor to remove it will be even harder and a very awkward job for even a garage mechanic to do.You would also have difficulty refitting it without damage.

Also electrical components and wet places historicly don't mix very well http://bbs.sidc.co.uk/smile.gif

I'm wondering if Jap and UK cars behave differently. Maybe the Jap ECUs are programmed to expect higher octane fuel and therefore adjust to it much quicker than the UK ones - this might explain why the difference of opinion seems to lie between grey owners and UK owners.

I own a 98 WRX and I must admit that I find it very hard to tell the difference between SUL & NUL while staying within the speed limits - perhaps it becomes more apparent on the rolling road. The only reason I use SUL is to avoid "piston death". However, I always try and use Esso fuel and I've heard rumours that their fuel is always on the high side of the octane ratings (is this true?!).
After reading all this discussion, I'll try it out on my car today...

The effect of going for a blast on the M-way will be to burn off the carbon deposits that tend to build up in day-to-day traffic. I always find my car feels much better after I've given it a really good hiding on some deserted roads. I'm not saying this proves anything one way or another, but it could account for the perceived improvement.

Gibo - why don't you try a couple of experiments. First off, just take the car out and give it a blast without doing a reset (and without putting any NUL in) and see whether you notice the same sort of difference afterwards. Another thing to try would be to put a small amount of NUL in, refill with SUL then go for a blast, again without an actual reset.

Meanwhile, my car is running way rich, so I'm actually hoping the ECU reset *isn't* a myth and will fix my problem...

-= mike =-

I have an Sti series 2 (5 door) Proir to this I ran a Cavalier Turbo for two years and tuned it to 280 bhp. I would very much endorse the comment re Esso fuel. I found the Cav ran as sweetly on Esso unleaded as most other Super unleaded.