Fuel Tank Considerations

[BigMike]

Okay,

According to Google Earth and the projected Buttonwillow LeMons track, the short version is about 2 miles per lap and the long version is about 2.7 miles per lap.

Consider the following data:

Fuel Tank     |	Average MPG  |	# Short Laps per tank  |	# Long Laps per tank
Stock, 9gal	5	22	16
9gal + 5gal	5	35	26
.
Stock, 9gal	8	36	26
9gal + 5gal	8	56	41
.
Stock, 9gal	10	45	33
9gal + 5gal	10	70	51
.
Stock, 9gal	12.5	56	41
9gal + 5gal	12.5	87	64
.
Stock, 9gal	15	67	50
9gal + 5gal	15	105	77

From a previous Buttonwillow LeMons event, the winner's average lap time was 2:50mins completing 281 laps total. I am not sure which track version this was raced on. Here is the data:

Fuel Tank     |	Average MPG  |	Hours Per Tank if Short Laps  |	Hours Per Tank if Long Laps
Stock, 9gal	5	1.07	0.79
9gal + 5gal	5	1.66	1.23
.
Stock, 9gal	8	1.7	1.26
9gal + 5gal	8	2.65	1.96
.
Stock, 9gal	10	2.13	1.58
9gal + 5gal	10	3.31	2.45
.
Stock, 9gal	12.5	2.66	1.97
9gal + 5gal	12.5	4.14	3.07
.
Stock, 9gal	15	3.2	2.37
9gal + 5gal	15	4.97	3.68
.

edit: Additional calculation of this data shows that the 1st place car either averaged 42 MPH (if they raced the short track) or he averaged 57 MPH (if long track). Hey Bryan! What was your lap time again in the MR2 on Buttonwillow for the full length track?

[BigMike]

Before I made these calculations, I was thinking that we could add a small 5-gallon fuel tank to the front trunk. 5 gal of fuel only weighs 31 pounds, so with a tank, pump, and 1 line to the main tank, it wouldn't be more than 40 lbs max.

But after looking at the data, even if we average only 5 miles per gallon, in the worst case scenario we will get 48 mins out on the track per tank of gas. If we make 10 MPG, then this worst case will still get us a whopping 1 hour and 35 mins on the track without needing to pit.

I agree with what Bryan said at the 2nd meeting that we need to consider how long each driver can even stay on the track at a time. Is 1 hr 30 min segments inbetween pits too long? What do you guys think?

[BigMike]

If we transplant the 4A-GE into my car, then lets only put in 3 or 4 gallons and run it super super hard continuously until it runs out of gas, and then see what the average MPG is. At least this would give us a ball-park figure, plus my car is heavier than our LeMons car which would only help the cause.

[kdogae86]

interesting subject. we need to ask brian how long each track session was that he drove and how he felt after. thats the only knowledge we will have in advance. this is all a big unknown until we go do it.

[kdogae86]

put 4 gallons in the mr2 and drive it up tollhouse with a chase vehicle and see how long it takes to run out.
but tollhouse isnt long enough.

[BigMike]

Since things have changed a bit and the engine will remain with the car, I say let's tow it up to Bills and just his Tollhouse from his place. Just need to make sure to have a chase car stay close behind.

[BryanH]

If the fuel gauge works, that's probably good enough.  I can't recall for sure how long it took to go through a tank of fuel on my MK1 at the track but it was definitely long enough that a driver would welcome a break after a full fuel stint.  My trackday sessions were usually 20-30 minutes at a time, definitely not long enough to worry about fuel. 

[Sirdeuce]

Check the fuel comsumption as you would normally do, fill tank, run a few laps, fill tank, calculate. Only problem here is traffic. 1 pokey slow, and results are out the door. My suggestion is to run the back of Pine Flat. Minimal traffic, hardly ever see a cop. Or run out Burrough Valley/Maxon, R. on Watts, R. on Pittman Hill, R. on Sample, etc.. Back to Burrough Valley. Rinse, repeat. That should be about a 20+ mile course. Now, Who wants to volunteer to do the driving?!?!

[BigMike]

Now, Who wants to volunteer to do the driving?!?!

ooo! ooo! pick me! pick me!

[Sirdeuce]

Although, driving in the hills won't be accurate for flat land driving. Mileage be a bit better on the track I'm sure.

[Sirdeuce]

When kevin and I went to P-a-P for the throttle cable we saw a tank that looked like it would fit in the front trunk. Wasn't a very big tank either. Tanks material looked like it might be poly.

[BryanH]

Any tank that would fit in the frunk (without cutting it up) would only be a few gallons.  It would also change the weight distribution of the car as fuel burned off.  The stock fuel tank is actually in a really good location as far as balance, and doesn't have any pickup issues at high Gs (at least until you get really really empty). 

[BigMike]

This remains to be proved, but I think my calculations show that the stock tank will outlast driver intervals. If we make 12 to 15 MPG we might get 2 or 3 driver changes PER TANK. (of course we wouldn't want to risk running low on fuel, but I'm just saying...)

[Sirdeuce]

We can get the thing together, bring it up here, and we can all take it out for familiarization. At least the hills are a bit safer than the city streets. And we'll all (even me) have to agree not to run without a chase car. Communication and spotters would be a good idea too. Sounds like a team effort in the making.

[Sirdeuce]

As far as the mileage test runs, Mikey, I'm the better candidate. I live up here, and I know the roads better. To make sure of that I'm going out to practice RIGHT NOW!!