putting premium in a car that is TUNED FOR UNLEADED results in power loss, putting premium in and then tuning for premium will then give a power gain but not before tune

make sense now?

i dont really understand the octane rating and that that much, but basically from what i think the quicker and more that stuff expands the better

does burning quicker mean expanding faster? i pressume it does, but does it still expand to the same volume or i guess more so pressure in a confind space?

Yes it does. There are some good articles around on octane ratings, it makes very interesting reading if you have the time :)

Quote:Safe? Yes.
Recommend? Not for a street car, as it cost more.

Quote:I've read expert opinions that state this, and other experts that say it doesn't really matter. For a street car, can you actually tell the difference? I cannot. Maybe on a dyno. I guess I'm wondering why would someone pay extra for high-octane fuel w/o tuning the engine to take advantage of it.

The main thing, and I'm sure we'll all agree, is that if your street car is running good on the least expensive grade, there is no reason to buy the more expensive ... if you are running a race car that is different -- then it may be important.

my mate try the premium by running a tank in their car, they conclude that it has no benefit but thats cause theyre not tuned for it, thats all im saying - dont do this

you are supposed to get better milage from premium also so that should offset the increased price

I have been running my holden ute on PULP for nearly six months. I've noticed that it runs slightly cooler and noticably smoother than it did on LRP.

If you run an engine designed for leaded fuel on unleaded without retarding the timing, it WILL ping. If you do retard the timing you'll lose some power (I have experienced this firsthand).

In my opinion PULP is the best of both worlds.

That's my $0.02+gst worth.

Chris

I'm assuming PULP is Premium Unleaded Petrol and LRP is Leaded Regular Petrol? Or is it something else?
My two cents is (are?) use the cheapest grade of fuel that doesn't knock or ping. But then I'm too lazy to tune for max power in a street car.

LRP=Lead Replacement Petrol

i.e Super, but without the lead. It's uses some other chemical to stop pinging.

Chris

Quote:Yes, if the octane rating is lower. If the octane rating is the same it shouldn't ping -- the octane rating is based on the anti-detonation property of the fuel.

This isn't an issue in the US, as only unleaded is available for street use. About 10-15 years, we switched from 89 leaded to 89 unleaded. For while we could get leaded and unleaded with the same octane rating. I think the "regular" (low octane) was 89, now it's 87 using a different rating system, the (r+m)/2 method.

I am fairly sure that PULP's octane rating is at least the same as LRP (BP PULP is one point higher. That's what it says on the pump anyway.)
I was going to try advanceing the timing a tiny bit, but I haven't had time to do this yet.

Chris

P.S. What do you guys have the timing on your dattos set at. Mine is set at 15deg advance, and it dosen't ping. Actually, now that I think about it, it still has half a tank of real leaded fuel in it. The last time I filled it was just before they started selling LRP, now that was a while ago. I need to drive it more