IXLR8

Look at the bright side Steve. At least it is more technical than some of the totally off-topic non-technical threads found here...in the "Air/Oil Cooled Technical Discussion Areas" folder.

Heading back into the garage to do some technical stuff.

michel j

I agree, when I fill it right up, it's like eating too much for dinner!

Wow Steve, sorry you feel that way!

Steve 96C4S

Uh, sorry guys. I think I woke up with a bad case of cranky today. Now I understand this thread better after rereading it. It certainly has validity! My bad...

Quadcammer

not really. I would say that unless you absolutely drive it until you can't get any further, the average empty to full fill up is about 16.5 gallons.

a gallon of fuel weighs 7lbs. Hence the difference between adding 10 gallons and adding 16.5 gallons is about 45lbs.

If you can tell a noticeable difference in performance or handling with the additional 45lbs 1 foot in front of the drivers feet, you're either a much better driver than me or your butt dyno is calibrated by nasa.

Now between a full tank and a nearly empty tank (which has a weight difference of probably about 125lbs, you may notice something, but its not going to be that significant.

race911

Uh, yeah. I'll throw in my weekly "when's an instructor refused a student a ride at the track because of the extra ~180 lbs." comment.

Near full-to-near empty, WITH data logs, I can't hardly tell a difference in the yellow car. Maybe, MAYBE 1mph front straight Thunderhill (75-125 pull...45 if you check all the way back to T14 apex). And for those still not believing, I got a screen shot from the morning warmup at today's PRC race; and Tom VanOverbeck has Spec 911 pole @ 2:01.XXX with 150 lbs. trophy weight.

michel j

True, but I get to 1/4 tank faster and at that point its down 100 Lbs. At that point, with LWF, the shift from 1st to 2nd is almost acceptable. I don't run a spare, tools or jack either. I learned this from running with a 912 for years.

Many spend big $ to reduce their car's weight by that much.

NC TRACKRAT

For those of you who don't have an opportunity to exercise your vehicles as much as you'd like, you're better off keeping it topped off...Less chance for condensation to form. Water will always settle to the bottom.

jakfrost

Which is the main reason I ALWAYS top up...with 'brim' or otherwise. Here in the northeast the cold nights and warm days are perfect conditions for condensation to form. I have had to use POR15 on more than one gas tank to recover it from the rusty interior caused by condensation.

The second most popular reason for me is I'd rather be driving than stopping, performance gains not withstanding...

Jim

IXLR8

Jim, note that our gas tanks are plastic, but that doesn't mean the water can't affect the fuel pump or any other metal in the system, in time.

The Brewmeister

I always fill it. I hate stopping more than necessary.

993Brendan

I typically throw $20 in whenever I want to go for a spin.

V

I agree about not feeling the difference, but 45lbs is way off, at least in my case. I have the optional 92 liter tank so let's assume a 80 liter delta maximum. That's 0,75kg/Liter x 80 = 60 kgs = 132 lbs so it's about 3 times your figure. Or did I miss something here?

I fill up my tank all the way each time, I hate stopping for gas (would rather be in the car). I havn't noticed any performance difference though. The only thing I enjoy when stopping for gas is to see the look on the clerks face when I'm about to pay and he asks "which car is yours?" and I point at the porsche having just filled more gasoline (+85L) than the typical SUV .

Renaud Bizet

When I go from an empty tank to a full one, I can definitely feel the steering weight change.
The added weight over the front axle feels like my power steering has been dialed back a bit.
It is hard to notice over time as your burn fuel, but from both extremes empty to full, there is definitely a difference. Now in terms of accelearation I cannot tell it is more in terms of weight transfer.

Quadcammer

pretty much no one in the US has the 92l tank.

The car holds about 19 gallons from literally bone dry to completely full, but for the most part it seems the light comes on pretty early and even when the gauge shows empty, there are still a few gallons left.

As i said, full to empty is a difference of about 125lbs.

Allen

I fill it up...run it until it's about empty. I've done this since 1999...and tracked every tank of gas that's been put in...mileage, gallons, price. That makes 94 tanks of gas, avg. 19.47 mpg, price for 93 octane: min $1.20 (11/2001) max $4.26 (6/2008)...haven't bought gas since 1/2012...gotta feeling I'm gonna see a new max...big time