I need someone to chop me that sign

 

I dunno Billy. On the LS 2.2miles you're dropping from 90 to 40 up to 60 down to 40 up to 75 up to 100 down to 45 up to 75 etc. The biggest factor on the big track would be the drag at high speed. All I need it 13 mpg and I don't think that's unreasonable. In any event the splash and go numbers are in there and I dont' think the one minute would make all that much difference to the overall numbers.

I did use 12 gal at refill... says so in the paper.

I sure wish I had some real numbers from Indy.

[QUOTE=WestSideBilly,Jun 22 2007, 08:34 AM]By 5 he meant I-5, I assume.

 

[QUOTE=WestSideBilly,Jun 22 2007, 07:34 AM] By 5 he meant I-5, I assume.

 

 

We'll never agree on the fuel mileage thing without some real data...


I've gotten 30+ on numerous occasions. Typically averaging 75-80, top and windows down (worst case), heavy load (my 230 lbs and ~50 lbs of stuff). That would drop off quite a bit if the average was 100, but as I said, instantaneous mileage is probably in the mid 30s. The loss is the putzing around the gas station, on ramps, slowing down and speeding back up for traffic, hills, etc.

 

The faster something moves, the more friction it has. There's really no way around that. Now, that doesn't mean the F22 has less friction than the F20 at a given engine speed, but within the same engine, friction losses would track with engine speed.

A road course would be 60-80% duty. You're wide open on the straights, consuming max fuel (roughly .15 to .2 gallon per minute). The rest of the time you're consuming little (sweepers) or no (braking/turning) fuel. At IMS, you'd have a 100% duty cycle, consuming fuel at a similar rate but with no reprieves. Granted, you're going faster, but the engine is burning fuel to make that happen.

Anyone have a runway we can use? It wouldn't be hard to monitor fuel consumption.


Also, momentum has no effect on fuel mileage. In fact, momentum is more of a penalty on mileage - it's a factor of mass and velocity.

 

highway 101 out on the peninsula... 2~3 mile straights and virtually no one out there, not to mention some of the side roads, almost all of which are in pretty good shape

 

yay basic physics!

 

Billy brings up a good point about the instantaneous fuel consumption but the best element for this discussion he has just raised it the issue of top up top down. Getting 30 mpg isn't impossible... top up, level roadway, no curves and short shifting would all make it possible. There is one more point and it's been discussed here; that's the speed.

I'm not sure we're going to convince you S2k-T but the difference in drag between 100 and 85 is staggering. Drag is related to the square of velocity. In other words as velocity doubles drags is impacted by a factor of 4. I'm careful not to say it goes up 4 times since Billy is quite knowledgable in this area and would be happy to correct me but he will agree that v^2 in the equation will mean what I have said.

What equation?... there are a couple of good explanations in, where else?, wikipedia...

http://en.wikipedia.org/wiki/Drag_%28physi...t_high_velocity

So the difference in throttle between 85 and 100 *is* considerable. This is why when determining highway fuel economy carmakers routinely test at speeds around 35 mph instead of legitimate highway speeds.

Momentum in this case isn't going to help you. Yes, the car will have more momentum but the high drag is constantly trying to slow you down quickly so your momentum at 10 mph works well to sustain that speed, at 100 it won't.

Just to be sure, I don't think Billy or I are trying to be dickish to you. It's just physics.

 

no no, you guys arent being "dickish"

also, on Indy 500, you will have the chance to draft a bit. I doubt at top speed while drafting you need to be at WOT.