gota911

Good one!

However, you should have done that BEFORE your brain became warped!

niner niner seven

hilarious

niner niner seven

yeah that is huge

i drove my grandmother in my 997 once. she weighs prolly 150 to 160. i could really feel the difference when there is another persons in my passanger seat as the car was a bit more sluggish. i thought fuel would weigh a fraction of that so i might considering going half tank. besides the more fill ups = more talking to girls at the gas station.

Coochas

A few weeks ago at Monticello I had 5/8 tank and went out for my 25 min session. I had to come in when the low fuel light went off! The TT in particular is a pig on gas at the track.

Our 997s are between 3100-3500 pounds. An extra 8 gallons of gas at about 6.5 pounds a gallon is a drop in the weight bucket!

Alfaguy2

I put in about €20 a week - the car is only taken out about three times a week for short pleasure trips.

If I am going on a long journey I always fill the tank.

I never noticed much of a difference in handling if the tank is full or almost empty - except in my wallet of course.

sjfehr

1/2 tank is actually one of the worst things you can do, performance-wise, as it allows the greatest amount of sloshing; 60-odd lbs of weight moving back and forth as you maneuver, and unbalancing the car in the process. Unless you're interested only in straight-line speed (I know you aren't; you drive a Porsche!), you're better off with either a full tank or as empty a tank as you care to risk.

Mike in CA

Although that might seem to make sense intuitively, I think it's a pretty minor factor especially given the fact that 1) there is quite a bit less mass moving around to begin with which will partially offset the weight transfer, and 2) the fuel tank is irregularly shaped which is going to inhibit sloshing from side to side to a great extent. With respect to competitive events, I've got to drive to the event, run autoX all day, and drive home without refueling. If I start with a full tank I'll be down to 1/2 by the time I'm trying to get in my fastest afternoon runs. If I start with 1/2 tank I'm running with minimum fuel by afternoon. Works for me, anyway.

budmanv24

Calculations on effects of fuel sloshing:
http://www.rennteam.com/forum/thread...ing/page1.html

Are 997 tanks not baffled?! If they didn't the gas gauge would bounce around like crazy as you went down the track.

Heck, my 92 jeep wrangler tank has baffles in it if I remember correctly.

Personally before going out out on the track I empty my trunk...both figuratively and literally.

mdrums

Sometimes I remove my left leg. Saves about 12lbs...

Mike in CA

You must have PDK.....

sjfehr

By those calcs, works out to about 2% increase in loading on the outside tire. There's more than just the weight transfer and corner weighting; there's also the inertia of the fuel sloshing. 2% is an easy number to work with, though.

2% would be negligible on the street (we should never be driving that close to the edge), but speaking from a competition standpoint, 2% is 1.2 seconds lost during every minute spent cornering.

brendo

winner

lexart

I hope its Snell tested and certified to at lest SA2005 or better. If not, you'll need new skull come next season

Mike in CA

Not to drive this into the ground but I still think the "sloshing effect" is being way overstated for several reasons:

1) The link to the Boxster board which derives the 2% figure assumes that all of the fuel in one side of the tank will slosh to the other side in a 1g turn. This might be true in a perfectly symmetrical tank, but the 911 tank, even assuming it has no baffles, is not symmetrical, so the weight transfer will be something less than perfect and the resulting additional tire load will less than 2%.

2) Even if the 2% additional loading of that outside tire were correct, it still doesn't automatically follow that cornering will be degraded by an identical 2%. Adhesion of the other tires, steering, power input, etc could all mitigate the effect. It's not necessarily a one to one relationship.

3) A reduction of 59 lbs (1/2 tank of fuel in a 911) is a 1.8% decrease in weight for a 3200lb car. Whatever small decrease in cornering times might be attributed to that 1/2 tank of fuel sloshing around is going to be made up to some degree by increased acceleration on the straights and better braking into the corners due to the lighter weight.

This whole discussion is a little like arguing how many angels can dance on the head of pin but it's kind of fun to work through. Bottom line, I still think the possible negative effect of sloshing fuel is overstated and is likely going to be quite a bit less than the positive effect of lower weight.

DPorcella

After a tough day, you guys' senses of humor made me smile. Thanks!