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Interesting 91 Octane article in today's USA Today
Posted 31 July 2004 - 12:31 AM
Posted 31 July 2004 - 04:51 PM
Posted 31 July 2004 - 07:03 PM
Posted 01 August 2004 - 05:01 AM
Most new cars have sensors that will adjust timing to the octane used, so using 87 won't ruin the motor but it will run like crap.
If you're talking about a knock sensor(all newgen subarus have at least one) that isn't a good way to use a lower octane than required.
Posted 01 August 2004 - 06:29 AM
Premium fuel does, however, allow a high compression / high performance engine to run a more aggressive fuel and timing program making more horsepower as an end result.
Posted 01 August 2004 - 07:14 PM
Posted 01 August 2004 - 07:20 PM
Posted 02 August 2004 - 10:45 AM
Aye i do believe greg is right? thats how my science teacher said it. I hear all turbo charged engines shoudl run higher octane because it burns slower causing less wear on the turbo. Also if you run too high an octane for your car itll cause carbon deposits because its burning to slow. I dont know if this is all true or myth or what just my 2 cents.
You want higher octane with a turbo or super charger because as you build boost you increase your running compression ratio. This running compression ratio can quickly exceed the rating of low octane fuel.
Posted 02 August 2004 - 01:44 PM
Posted 02 August 2004 - 02:15 PM
I ran a supercharged 5.0 mustang on the street with 87 octane. All I would do is drop my timing down to around 8 or 10 degrees BTC (10 is stock for that car). When I needed the extra power for a track day or a race I would fuel it up with 91 or 92 and raise my timing up to about 16 degrees. I'd have to say the extra timing would add easily 40 to 50 hp espically in the low RPM range. But that's only 10 to 15% of the HP the car was making.
If your car will not run without "pinging" on 87 octane then your timing is too high. Every car is different. Every engine is different even when they roll out of the same factory. I've seen stock mustangs that would not allow over 10 degrees BTC, and I've seen ones that would go up to 15 or 16 without pinging.
The new subaru motors all seem to be higher compression (over 9.5:1) With compression like this, considerable power gains can be had by running higher octane and more agressive timing. Stock timing seems to be friendly to 87 octane since I have been using the cheapest crud I can find in my 2.5 RS since the day I got it. Never a ping from the engine, nor what felt like silent detonation in my car.
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