Does anyone know why I get less gas mileage with an octane booster? I have a superchager and when I use 91 alone (the highest in Colorado), I get about 30-50 more miles a tank. If I put in an octane booster (hyperfuel +8) with the 91 octane, I get less miles per tank/gallon. Any ideas why this is?

The reason I use the booster is because I get hardly any pinging with it; without it, more pinging, but less miles per gallon... :pat:

 

Not sure about the octane question, but you've hit upon one of my pet peeves You can't acurately gauge by "miles per tank", the gauge just isn't made for that kind of accuracy, you must calculate by dividing actual miles (since the previous fill up) by actual fuel used (ie. gallons to fill it back up). Start keeping track using this method and you will be able to tell alot more regarding mpg.

 

more complete combustion uses more fuel

 

maybe look into a different octane booster, also i see lots of people get a 7th injector with S/C on that engine. i would first worry about sorting out all pinging before being concerned about MPG. somethin doesn't sound right on your setup, so first get it working smoothly (no pinging) and your mpg might also be sorted out.

 

BINGO!!!!

 

do i have the theory backwards or is that right? im htinking about it.. and im not sure right now....

 

Well, yes, i believe you do. More complete combustion means you burn more fuel, rather than passing it out as waste, right? It's late, but i think that's right.

 

Are you having pinging issues with 91 alone? Most octane boosters aren't that good and are harmful to plugs and 02 sensors on newer cars but I'd give NOS brand race formula booster a try since I have seen actual dyno results from that one.

 

It doesn't consume more fuel it just burns the fuel that was injected more completely and isn't wasted.

 

So, is the NOS better on the plugs/O2 sensor? I am having some pinging with the 91 alone, but it is minor...no pinging with booster.

 

hmmmm do you have the 1 step colder plugs? Might wanna swap gas stations too.

My 3vze was pinging like a mofo even with 93 octane and an octane booster for a while. Switched gas stations to a more hi volume place where we diesel up at and filled up with straight 93 and I can't make the 3vze ping if I wanted to! At the next fillup I'm going to readvance my timing from 10* to 12* or so and see what happens...

 

I am moving to Vail in a couple of weeks. Why is the octane 85, 87, and 91 in CO? Is my S/C going to screw up after running perfect for 60K miles?

 

This is correct......you don't use more fuel, you use it more efficiently.

You might start looking into gadget's fuel upgrades to cure the pinging.

 

There is less air (atmospheric pressure) at high alltitude. Engines will burn richer with less air so, no need for higher octane fuels. This is why so many people at sea level have more pinging problems than others at high alltitude.

 

That's so true. Today I drove to Copper Mountain (through Eisenhower tunnel ~12,500 feet above sea level) to go snow boarding and I had no pinging at all...the thing just climbed like my wife's 330xi! I was stoked. I passed a V8 Tundra...it was cool (I'm sure he was not racing me, but it was cool anyway).

 

I don't have the colder plugs. Would that help do you think?

 

I am at 9 feet above sea level and never have had any pinging. So moving to 9000 feet above sea level should be better for my S/C??? Sweet. Now if only I could find some premium for less than $8 a gallon.

 

^At altitude, it's not that you run richer as the FI system trims fuel to compensate for air density, it's that since there is less pressure in the air, you wind up with less pressure in the cylinder. It would be more like running at not quite full throttle. Pikes Peak racers run ridiculous boost up there that they simply can't do at sea level because the pressure in the cylinder would be too much to control. You can also run higher compression at altitude for the same reason.

On the octane issue, I'm going to guess that the booster you use is also an oxygenator, which adds oxygen to the fuel and requires more a slightly richer mixture to achieve stochiometric. That's a guess, though.

 

I don't know, but it sounds good! I'm going to put in cooler plugs, a colder thermo, and run the highest octane I can until I can afford the URD kit...it shouldn't be too long on that...maybe February...And...THANKS everyone...Happy Holidays!!!

 

someone correct me if im off base but the colder plugs dont retain as much heat as the hotter ones, as they have less mass. The 'hotter' plugs my induce a bit of preignition.... hence the colder plugs. I think....

I just know gadget dropped down to one step colder plugs with his SC 5vze