I own a Black (not that the color matters) 09 SS/TC. A buddy of mine in a souped up Focus wants me to go on a 'spirited' drive w/him this coming thursday. Quite a bit of it will be going UP a mountain. Would running 100 octane race fuel give me much more power or should I just stick to the 91 that's available at the local pumps?

First, let me say I KNOW my car will blow his into the weeds, but in case I take him for a ride I'd want max 'GO' power...

 

You would need to be tuned for it to make a difference.

 

I don't think your car would love the racing fuel I think its 100 octane and it would throw off the engine unless you tune it for it

 

the point of a higher octane is to less the chance for pre detonation alowing you to run higher compression or advanced timing. unless youre engine is knocking its not going to do anything unless youre tuned for it.

 

I also recall the stock PCM is programmed to put a cap on the torque output, so you're still not going to benefit from higher octane fuel. 91 octane is only recommended for the SS/TC. High octane fuel is just going to make your tail pipes turn pitch black.

 

Excellent advice folks!! Thanks tons. Much appreciated. You just saved me the money to fillup w/$$ gas.

Cheers!

Buzz

I would like to add..

Does a K/N filter help much on a stocker? Or again, does it have to be tuned to it.

And..speaking of the nature of tuning. I currently live in Arizona but I am going to be taking over 2 months off of work (paid) to drive across the US w/my 17yr old son taking as much of route 66 as possible. We'll end up in Ohio and spend the majority of our time there. MY QUESTION is... Since my car is an Arizona car, does that mean it's tuned to Az and the barometric pressures HERE...AND..will it run funky while I'm in Ohio? Do you guys recommend a re-tune once I"m there?

Also, how much do the retunes cost when GM does them?

Thanks again for all the info.

Buzz

 

No re-tune is needed. It adapts to changes in altitude, and actually turbocharged engines have less issues at higher altitudes than naturally aspirated motors.

I wouldn't recommend K&N since they have been shown in our own testing to be inferior to paper filters.

If you really want to run high octane fuel, just gas up with Sunoco 94 octane. Ohio has plenty of Sunoco's on the state turnpike / I-80.

 

Thanks again for the expert advice Metro and others...

As for 'wanting' to run the high octane... I just wanted to see if it gave it any extra oomph. If you guys say it's pretty much pointless with the stock ride I have..then I believe it.

Thanks again... 20 minutes until my 4 day weekend starts!!

Heading up Yarnell Hill (look on Youtube for it) this Thursday. Can't wait.

 

i beg to differ. I believe even without a tune a higher octane will help slightly, nothing noticeable. Your fuel will be more combustible and burn hotter therefore giving you slightly more power, but not much, just stick with the 91. I use 93 from shell or gulf, nothing but 93 goes in my car.

 

False. All unleaded octane fuels burn at the same rate. The higher octane rating is just how much heat it can withstand before it combust on it's own.

 

You will see worse performance with higher octane if not tuned.

I guarantee it.

 

One reason why a higher octane fuel might help performance is if the car was tuned to advance spark when no detonation is detected.

 

unless you have hptuners to advance the spark when you switch to the higher octane then it is useless

 

that higher tolerance to heat will actually slow down the rate of combustion slightly, which is why there is a slight loss in horsepower when using high octane for tunes not made for it. Since the molecules of unburnt fuel closest to the flamefront have to heat up an additional few degrees, it takes longer for the flamefront to move to the next particle, effectively slowing the flamefront's speed

 

My apologies!

 

haha. just trying to share the knowledge

 

Good stuff folks... Thx for the lesson!

 

In theory, if you were deep into boost for an extended time....and were to heatsoak the intercooler, thus forcing sustained high charge temps... Running a slightly elevated octane fuel (such as, by adding a couple gallons of 100 to a tank of 91) would reduce potential for knock. It certainly isn't going to "give" you any extra performance, just reduce the possibility of power reduction.

 

^

 

I agree. The whole point of running high octane fuel is that it has a higher anti-knock rating, which prevents premature detonation (pinging, etc...)

Whenever you compress air, you increase the temperature of the charged air. This follows the ideal gas law (PV=nRT) where Pressure increases in relation to the temperature, or rather the temperature increases with an increase in pressure. So as you compress the intake air stream, the temperature of the charged air rises significantly, hence the need for your intercooler / heat exchanger. That will help reject a lot of that heat to make the charge air denser (more oxygen) for more power output.

Under gatekeeper's heatsoaked scenario, the higher octane fuel has a higher resistance to detonation which prevents the PCM/ECU from retarding the spark due to knock sensor activity. As a result you don't lose as much power.

Ideally you want the charged air to be cooler than ambient which isn't possible without some method of active cooling (refrigerant, ice, etc...)

 

ideally, you want IAT2 to be the same as ambient air. that would be a 100% efficient compressor. There's no such thing as a compressor that would deliver more than 100% efficiency

 

Is IAT2 the thermistor mounted downstream of the turbo? If so, what I said is the same thing. Ideally you want the charged air to be at ambient or below ambient for maximum power. You could get close to ambient using ice/refrigeration. I have seen some wild setups designed primarily to reduce 1/4 ET.

 

IAT2 is after the intercooler. Your intercooler should be 80% efficent or better which would mean on aver 15 degrees above ambient air temperature.

 

I have a Stage 2 SS/SC and when I take it to the track I want. to run a couple gallons of racing fuel in the car. However before I do that I want to be absolutely certain that the engine could sustain that kind of heat. Any help I could get would be great thanks.

 

what heat? octane is resistance to detonate, thats all