FR500 Cobra Fuel Mileage Update

[99svtvert]

For those interested in FR500 motor Heads, Cams, Intake, (Stock 03 Cobra Tank and pumps, 39# inj, 90mm LMAF);

Fuel mileage (3.73s):

1st Tank -- 178 Miles (Dyno Tunes)
2nd Tank -- 210 Miles (Dyno Tunes)
3rd Tank -- 165 Miles (several easy 1/4 mile runs and Dyno Tunes)
4th Tank -- 277 Miles (Mostly City Driving)
5th Tank -- 314 Miles (City and Highway)
6th Tank -- 331 Miles (Mostly Highway)
7th Tank -- 326 Miles (City and Highway)
8th Tank -- 276 Miles (City)
9th Tank -- 337 Milrs (Mostly Highway)
10th Tank -- 320 Miles (Mostly Highway)

Swapped in 4.30's; out 3.73s

11th Tank -- 309 Miles (City and Highway)
12th Tank -- 297 Miles (City and Highway)
13th Tank -- 304 Miles (City and Highway)

3644 Miles Total

Avg. -- 280.7 Miles per Tank

Take away the first 3 Tanks for breaking and tuning, then

Avg. -- (minus 3 Tanks @ 533 Miles) = 311 Miles/Tank.

About 20.6 MPG

Which, beleive it or not, is a little better than the stock motor I had. I did not have an 0.5:1 6th before but I also did not have 4.30's either.

 

[REX-RACER]

Outstanding! I can tell you from experience that if you get out of St. L. where the gas is 10% ethanol blend, your milage will go up 2-5 mpg!

I took a road trip last month and when I got out of St. Louis to places where the 93 octane was not ethanol blended my mpg went from 21-22 to 25-26 plus it seemed like the exhaust tone got 1/2 and octave lower!

 

[01cobravortech]

Damn, well those are some pretty damn good mpg numbers with the FR500 stuff. How many miles on your stock block before doing the FR500 swap? I'm concerned about the durability of my stock shortblock which now has close to 60k on it.

 

[cobraracer46]

Fuel mileage (3.73s):

1st Tank -- 178 Miles (Dyno Tunes)
2nd Tank -- 210 Miles (Dyno Tunes)
3rd Tank -- 165 Miles (several easy 1/4 mile runs and Dyno Tunes)
4th Tank -- 277 Miles (Mostly City Driving)
5th Tank -- 314 Miles (City and Highway)
6th Tank -- 331 Miles (Mostly Highway)
7th Tank -- 326 Miles (City and Highway)
8th Tank -- 276 Miles (City)
9th Tank -- 337 Milrs (Mostly Highway)
10th Tank -- 320 Miles (Mostly Highway)

Swapped in 4.30's; out 3.73s

11th Tank -- 309 Miles (City and Highway)
12th Tank -- 297 Miles (City and Highway)
13th Tank -- 304 Miles (City and Highway)

3644 Miles Total

Avg. -- 280.7 Miles per Tank

Take away the first 3 Tanks for breaking and tuning, then

Avg. -- (minus 3 Tanks @ 533 Miles) = 311 Miles/Tank.

About 20.6 MPG

You left out an important piece of data: rate of speed. In other words, how many miles per hour was the vehicle driven at on the freeway and on city streets ? Mileage figures for 55MPH will be significantly different than ones based of off 80MPH Speeds.

 

[99svtvert]

You left out an important piece of data: rate of speed. In other words, how many miles per hour was the vehicle driven at on the freeway and on city streets ? Mileage figures for 55MPH will be significantly different than ones based of off 80MPH Speeds.

70-75 Highway.

 

[ex-PJs snake]

Outstanding! I can tell you from experience that if you get out of St. L. where the gas is 10% ethanol blend, your milage will go up 2-5 mpg!

The ethanol blends will also reduce hp output by an estimated 3-7 on many applications, including n/a.

Where I live, the ethanol blend has not taken foot....yet, but with straight 91-93 octane, my city is roughly, depending upon driving conditions and "foot," 23-26 and highway is 26-30 and thats with a supercharger. City mileage is definately better than sticker, which I think when new, was estimated at 18. Highway is within new sticker estimations of 26.

 

[99riocobra]

so what's the reason we have the 10% ethanol in STL and the close surrounding areas?

 

[SvtSmitty]

We've got the 10 % ethanol here (Boston,Ma) think eventually its going to be throughout the U.S. and Canada by 2010

http://www.ethanol.org/

 

[REX-RACER]

The ethanol blends will also reduce hp output by an estimated 3-7 on many applications, including n/a.

Where I live, the ethanol blend has not taken foot....yet, but with straight 91-93 octane, my city is roughly, depending upon driving conditions and "foot," 23-26 and highway is 26-30 and thats with a supercharger. City mileage is definately better than sticker, which I think when new, was estimated at 18. Highway is within new sticker estimations of 26.

Ya know, I'd always wondered if there was a horsepower component also but I didn't want to say anything and then have someone say, "DO YOU HAVE DYNO DATA TO BACK THAT UP?!?!?!" :beer:

so what's the reason we have the 10% ethanol in STL and the close surrounding areas?

One word, "Emissions"! St.L. is actually considered a smog city w/ pretty bad aqi. :cryying:

 

[99svtvert]

I did not know about the percentage of ethanol here. Does octane make a difference in the percentage ?

 

[REX-RACER]

I did not know about the percentage of ethanol here. Does octane make a difference in the percentage ?

I don't think so, they add 10% ethanol to all the fuel around here. The reason is alcohol has much lower NOx emissions when burned and one of the byproducts is actually water.

The thing is, ethanol actually has a higher octane than gasoline, something like 100 iirc. But it has a different stoichiometric energy yield that most cars aren't set up to compensate for so subsequently you get slightly less power and milage.

 

[ex-PJs snake]

Ya know, I'd always wondered if there was a horsepower component also but I didn't want to say anything and then have someone say, "DO YOU HAVE DYNO DATA TO BACK THAT UP?!?!?!" :beer:

Well, if someone had asked for a link or dyno data, they would have been crap out of luck...my long time SCT tuner told me this concerning the use of 10% ethanol blend and lost hp. He lives in the city and has to use the ethanol blend and I live about an hour from him in the country and as of yet--knock on wood--I have not seen our gas pumps tagged with the little tag indicating the 10% ethanol blend. Personally, and maybe I am biased, but I tend to take most of what he (Ed Clark) says concerning these type cars seriously being he frequently drags one at a local drag strip--he's a qualified SCT tuner--and has access to a dyno. ;-)

 

[01vert]

Thanks for the data


Jeez, always nice for a guy to put up some data and then someone complains about it. What does it matter what speed he was going? It is just a comparative. Has no relevance to any other car other than the general increase or decrease in mileage. Might as well say "well its not my same compression" or "my tires are a different compound than yours". The data only compares the change to the FR parts vs the stock parts and if mileage changed. We can use as a base that he did not radically alter his driving speed on the highway or why would he bother putting together such data in the first place?

Thanks again for the info, like to see people with higher hp cars still knocking down decent (and sometimes better) mileage.