Do you autocross with the tank nearly empty or full?

Sorry if this was discussed before. I did a couple of searches, but only found threads about the size of the tank and use of regular gas.

 

I had always run my miata with 1/4 tank or less. But at topeka this year we suffered some really bad fuel starvation with just over 1/2 a tank in the S2K. On camera you can hear the engine cut for the entire length from one turn to the next (about 4 seconds). From what I understand people run with a full tank.

 

Depends...

Gas weighs 6.152 lbs per gallon so the less you can put in the tank the better.

BUT (and this is a big but)

The S2000 is known to fuel starve on left hand sweepers. If search ever works again - just do a search for fuel cutoff or starve and you'll get a bunch of info on this.

So if you're going to be running on a grippy surface I'd try to keep just under 1/2 a tank in there. You could probably get away with less - but it's not worth the risk esp if you only get 3 runs. For big events I bring a gas can and keep it at 3 or 4 bars, more if its a really grippy surface and/or the course has left hand sweepers.

-r

 

Thanks Mrsideways. That is always the trade off...less weight v. fuel starvation v. balance. I figured I'd ask the experienced folks and save myself some time when I go autocrossing this spring.

Happy Motoring

Bill

 

As others have said, the S2K only appears to starve on longer left hand sweepers. If the course doesn't really have any, you can get away with only a few bars showing on the gauge. If you think it is a course that the car might starve on, about 1/2 tank seems to be required.

-Andy

 

This is interesting. I never thought there would be advice to run at around a half tank. It has been 20 years since I ran regularly, but back then, the problem with a half a tank was the shift in weight going into and out of corners. I take it that is not a problem with these cars? Maybe the tank has baffling to minimize sloshing? Thanks for the input.

Happy Motoring

Bill

 

Bill, I've tried it three ways now, and with the suspension set up I've given you before, the rear end stays planted a lot better with a close to full tank.

 

Thanks. That confirms my suspicions. BTW, I just went and ordered a helmet yesterday and i am now looking for a shop in the area that understands the concept of a competition alignment. Also, the sway bar is on the way...

 

That is very interesting...I have autox'd both my S's and I usually run from 1/4 tank to 1/2 tank MAX....and NEVER, had I have had any problems with fuel cuts/starvation....I am thinking maybe, just maybe I am not hearing the engine cut off....??

 

The engine cut is not something you "hear" - it's more of a something that you FEEL - and its not something you'd miss.

Exiting that left hand sweeper - go to feed in the gas and NOTHING - then a sputter - followed by a lurch forward - then a big compression brake (from the next air bubble reaching the engine) - another sputter - and off you go! The entire time you FEEL like a dumbass for not putting more gas in the tank. GAS! GAS! GAS!

It's happened to me with as much as a little over 1/4 tank - on Hoosiers on really grippy concrete (with lots of Mod/Prepared car rubber down).

I've run 1 bar and zero bars of gas at low grip sites with absolutely no problems. So I'm betting that you're not running high grip sites.

The only benefit of the fuel starve goes something like this:
"I would have had a 36 - but I fuel starved the turn around."

-r