No, actually I talk for a living. I'd love a gig as a motoring hack but sadly so far no offers. Don't think I'd be bothered doing it in Ireland however, don't think I'd be able to handle reviewing the Daewoo Matiz somehow.
I don't know precisely what detergents they put in Shell V-Power. I do know that the base fuel bears no relation to the new UK or European V-Power which is 100 RON. Our V-Power is standard 95 with the additives that are designed to clean the valve gear etc.
When I was first re-mapping my RB5, I was running a tank of V-Power and Pat Herborn found it extremely intolerant of ignition advance. It was so bad he refueled while mapping with regular 95 and was able to wind up the timing by three degrees towards TDC, resulting in about 15 extra horsepower.
Your 2002 Uk spec STI will be fine (if slow) on 95 but I wouldn't bother with the V-Power myself, once in a while to give it a clean perhaps but otherwise I'd save your money, or spend it on booster.
Uk cars have to be capable of running on 95 since it's available everywhere. Accordingly, they run two maps, high and low octane. It makes sense if you think about it, my Evo is putting out 345 Hp from a two litre engine and comes with a three year, unlimited mileage pan-European warranty. It is running 1.65 bar and is fairly highly strung dynamically. The only way that the car can be reliable at this level is to ensure that the ECU is adaptive and has the capacity to keep the engine within safe limits.
Detonation is simply not an option if they are going to have to replace engines under warranty. Therefore, what they seem to do is to start the ECU out on the high map, but if the knock sensors pick up det, the ECU immediately retards timing. If this occurs repeatedly the ECU retards further and will switch to the low octane map. It will then err on the side of caution and stay on the low map until the levels gradually creep back up.
The ECU uses a very complicated multiplier algorithim that determines how much ignition advance to apply. This determination is based on average levels logged by the ECU. As a result, the return to full power is a slow process, much slower than the drop down to the low maps. This means that one tank of rubbish fuel will not be offset by one tank of good stuff, it can take a few refills before you get back up to full strength. This process can be accelerated by resetting the ECU but even at that, you will only come out in the middle of the high octane map and the timing will still be a few degrees off maximum. With the right fuel, this will climb back up gradually with some spirited driving.
Imprezas apparently have a shortcut whereby after a reset if you hold them in gear (ideally against the brake) at about 0.6 bar for a few seconds, the ECU will shortcut the learning curve and advance the timing all the way, I don't know if this actually works but I have heard a few tuners say it does.
The only way of ensuring consistent performance is to use good fuel, using just bucketloads of bad fuel will result in performance loss in Uk cars, as I experienced down the west, however in Jap imports, you'll need the bucket to collect the tears.
Evo Magazine recently did a few comparisons in the Uk at Dynodynamics. They used a Golf Gti and an M5 and ran different fuels on a dyno. They ran three full tanks of each fuel through the cars before testing on the rollers to give the ECUs a chance to adapt. They discovered the Gti was down by as much as 20% Hp when using 95. Interestingly it made no difference whatsoever to the M5.
This actually makes sense. The Gti, like us, is turbocharged and therefore running a lot harder and hotter to get its power out of its four cylinders. Low octane is a real problem in this environment as det directly results from heat and pressure. On low octane, the ECU feels the knocking and winds back the boost, ignition timing and also enriches the mix to cool the cylinders. The result is power loss and poor economy.
The M5 on the otherhand is a 5 litre V10 that is actually already pegged back to 500 Hp in order to save its transmission. Low octane does not bother it as det is not an issue as the engine is actually nowhere near its full potential, even at 500 Hp.
Evo didn't test Imprezas or Evos but Dynodynamics said that similar percentage losses apply to us as to Golfs and other turbo engined cars. They also said our cars express brand preference with 8 out of ten Evos going for Shell with the Scoobs apparently liking BP, go figure.
These figures accord with my own results from Westward with power down 12% odd on 95 RON. Torque fares a lot better with only about a 5% drop at over 400Nm. At 1.65 bar, the Evo's low octane map is more interested in timing than boost. Imprezas are a bit different, I have heard reports of boost as low as 0.9 bar in cars running crappy petrol.
Running booster really helps. That said, I couldn't say that my perception is so finely honed that I would notice a 12% shift one way or the other. Psychologically however, I feel a lot happier knowing it's in the tank and the car is running smoother and with less det. At the end of the day once the car is safe and feels good, dyno results are irrelevant. You will only notice the extra Hp at high revs and only then if you are going head to head with somebody with similar power.
That was the point of my earlier post, the difference between the performance of the RB5 and FQ340 on the rollers is huge, on the road head to head it's huge, however, from the driver's seat there is very little in it. It is the last one that matters though so don't believe the hype.
do evos suffer worse than scoobys with 95???????? 