View Poll Results: How much gas should be in the tank for auto-x?
Voters: 143. You may not vote on this poll
How much gas in your tank for auto-x?
03-19-2007 | 12:05 PM
#21
fortunately for autocrossing, the turns are pretty quick and you're usually not really giving it a lot of throttle to worry about fuel starvation or overheating the fuel pump. Still though, there's no reason to autocross with more than a 1/2 tank of gas.
03-19-2007 | 12:36 PM
#22
Originally Posted by sentry65
fortunately for autocrossing, the turns are pretty quick and you're usually not really giving it a lot of throttle to worry about fuel starvation or overheating the fuel pump. Still though, there's no reason to autocross with more than a 1/2 tank of gas.
http://www.scca.com/_filelibrary/fil...0nationals.pdf
03-20-2007 | 05:07 AM
#23
Originally Posted by tomsn16
We preferred using the fuel load to find the right weight to keep rear wheelspin to a minimum.All our testing kept telling us that a full or near full tank was best,even on the high grip concrete at Peru Ind,so we never let it get below 3/4.
Ballast per se not allowed in stock class.
Ballast per se not allowed in stock class.
03-20-2007 | 05:09 AM
#24
Originally Posted by sentry65
fortunately for autocrossing, the turns are pretty quick and you're usually not really giving it a lot of throttle to worry about fuel starvation or overheating the fuel pump. Still though, there's no reason to autocross with more than a 1/2 tank of gas.
Usually when I come out of a turn, I'm full on the throttle. I would be willing to say that autox takes more out of the car than a track day, mile per mile.
03-20-2007 | 05:12 AM
#25
Originally Posted by tomsn16
Sentry's post reminded me that most any single setup item may not work for all since there are very few if any exact same setups.In the case of fuel load we are just trying to share our learnings from 2 years of testing that yielded a repectable finish(by Carter) at last years Nationals...click and go to page 4 for BS results.
http://www.scca.com/_filelibrary/fil...0nationals.pdf
http://www.scca.com/_filelibrary/fil...0nationals.pdf
03-20-2007 | 07:33 PM
#26
Yeah, I really notice when I get below 3/8 tank that the rear gets really light and is struggling for grip. I don't like having more than 1/2 a tank, but that's only about 20 pounds or so.
One "advantage" to leaving the stock muffler is that the weight is low and at the rear of the car. In the rain, I've often been tempted to put the spare back into the car (and have done so -- with decent results).
One "advantage" to leaving the stock muffler is that the weight is low and at the rear of the car. In the rain, I've often been tempted to put the spare back into the car (and have done so -- with decent results).
03-20-2007 | 07:58 PM
#27
great info here guys! I assume for BSP, that it'd be more advantageous to use corner balancing for optimum weight balancing and then to run the lightest set-up possible...is that right?
-Peter
-Peter
08-06-2007 | 07:14 AM
#28
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From: Lone Star State
Wanted to resurrect this thread to share my latest experience. I've had a full tank for autocross during the last few months and decided to try 1/4 tank this past weekend. With a full tank, my Z did not have any issues putting the power down at any point on any given course. This weekend while on 1/4 tank, I struggled mightily on trying to get grip in the rear. In addition, my Z was "tail happy" -- with a full tank, my rear was more predictable knowing that it always stayed planted. I have a true dual exhaust so my rear is already light without the stock muffler. Also, I was trying to break-in a new set of r-compounds with only seven (7) runs on them previously so they're still slippery. The combination of a lighter rear & slippery tires did not make for a good experience on the course.
So, after yesterday's autocross, I decided to add 10 gallons to the tank (slightly less than 3/4 tank). Boy, was there a difference! I was able to put the power down & the tires had more grip on them, even though they still needed to be scrubbed more to get even stickier. Based on my personal experience, a full tank was just too heavy & a 1/4 tank too light. I have not experimented with a half tank yet but 3/4 tank definitely felt much better than a 1/4 tank or a full tank.
Below are a few comments that I extracted from this thread that I felt were very informative. I definitely learned quite a bit from my experience & felt that I should share them with other fellow auto-xers.
So, after yesterday's autocross, I decided to add 10 gallons to the tank (slightly less than 3/4 tank). Boy, was there a difference! I was able to put the power down & the tires had more grip on them, even though they still needed to be scrubbed more to get even stickier. Based on my personal experience, a full tank was just too heavy & a 1/4 tank too light. I have not experimented with a half tank yet but 3/4 tank definitely felt much better than a 1/4 tank or a full tank.
Below are a few comments that I extracted from this thread that I felt were very informative. I definitely learned quite a bit from my experience & felt that I should share them with other fellow auto-xers.
Originally Posted by 12AutoX
As far as the wheels feeling planted, I tend to do better with a copilot, esp. on asphalt. I run half a tank because I haven't made up my mind whether more weight is better or worse for tight courses and a torquey motor.
Originally Posted by PDX_Racer
Mine is *very* balanced at 3/8 of a tank, less than that and the rear is too light, more and there's a bit of extra weight. I'd rather have closer to 1/2 than 1/4 tank.
Originally Posted by tomsn16
We ran a full tank and so did Chris Hammond.Based on our testing rear wheelspin out of corners was nearly eliminated with a full tank plus a big front bar plus 285/30 Kumhos plus proper shock tuning.The Z's advantage is at corner exit(torque and lot's of it) and you must do everything you can to reduce wheelspin.
Originally Posted by PDX_Racer
Yeah, I really notice when I get below 3/8 tank that the rear gets really light and is struggling for grip.
Originally Posted by tomsn16
Sentry's post reminded me that most any single setup item may not work for all since there are very few if any exact same setups.In the case of fuel load we are just trying to share our learnings from 2 years of testing that yielded a repectable finish(by Carter) at last years Nationals.
Last edited by z-u-later; 08-06-2007 at 07:17 AM.
08-06-2007 | 05:45 PM
#29
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From: CT
Originally Posted by Fluid1
Not to attack, but please back up your claims?
Usually when I come out of a turn, I'm full on the throttle. I would be willing to say that autox takes more out of the car than a track day, mile per mile.
Usually when I come out of a turn, I'm full on the throttle. I would be willing to say that autox takes more out of the car than a track day, mile per mile.
08-06-2007 | 05:58 PM
#30
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From: Falkville, AL
My experience is that I prefer a full tank in the 07. Leave in the spare and jack also since it doesn't matter. I find if I'm a little too binary on the throttle I spin the rear tires going in a straight line, let alone exiting a corner. My first two months in the 07 were spent relearning how to drive since I found it that much different than the 03.
08-06-2007 | 06:04 PM
#31
Originally Posted by tmak26b
not really, i would love to see your melt your pads at the autox or fuel starve on a 10 degree banking pulling WOT in 5th.
Call me crazy!
Good topic resurrection z-u-later
08-06-2007 | 06:07 PM
#32
Originally Posted by DriveI65
My experience is that I prefer a full tank in the 07. Leave in the spare and jack also since it doesn't matter. I find if I'm a little too binary on the throttle I spin the rear tires going in a straight line, let alone exiting a corner. My first two months in the 07 were spent relearning how to drive since I found it that much different than the 03.
Most club will have a clean check before the first track session. Nothing should be in the car except you and your instructor.
08-06-2007 | 06:22 PM
#33
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From: Falkville, AL
Originally Posted by Kolia
You don't want to have anything that can potentially come loose in your trunk while tracking. More so when you're sharing the same space like we do in our hatchback.
Most club will have a clean check before the first track session. Nothing should be in the car except you and your instructor.
Most club will have a clean check before the first track session. Nothing should be in the car except you and your instructor.
08-07-2007 | 01:23 PM
#34
Good thread resurrection. I autoX with 3/4. I did a few with 1/4 or less earlier this year and my rear end was definitely looser/less planted. I didn't notice so much in terms of wheelspin out of corners, but rather in areas of frequent transition (e.g. slaloms).
08-08-2007 | 05:58 AM
#36
I always try to run as low as possible. But I haven't noticed much (if any) difference from being at 1/4 of a tank vs. being on - - - on the trip computer. I have noticed a difference when being near full vs. 1/4 of a tank. I usually like to have enough to do my runs and not have to stop by a gas station on the way home.
08-08-2007 | 10:23 AM
#37
Lee and I are running a full tank and will continue to do so. We experimented with different levels all season at local events and found that a full tank gives us the best traction coming out of tight corners.
In Toledo at the Pro on sunday we were actually encountering some wheel spin coming out of the turn around once we had burned off a 1/4 tank of fuel on saturday.
So we will definitely bring a 5 gallon bottle for filling the car up on day two of the Pro finally.
K
In Toledo at the Pro on sunday we were actually encountering some wheel spin coming out of the turn around once we had burned off a 1/4 tank of fuel on saturday.
So we will definitely bring a 5 gallon bottle for filling the car up on day two of the Pro finally.
K
08-08-2007 | 04:53 PM
#38
I run a full tank just for consistency. Its just one less variable to track from week to week while I learn proper technique. also another interesting point when I run with a passenger I can almost count on a 3 second reduction in
time.
my times from the last event...Guess which one I had someone riding with me.
144.304+2
138.578+1
140.049+2
141.923+1
140.171
136.634
139.719
140.659
I beat 4 vipers at this event
great cars bad drivers 
time.
my times from the last event...Guess which one I had someone riding with me.
144.304+2
138.578+1
140.049+2
141.923+1
140.171
136.634
139.719
140.659
I beat 4 vipers at this event
great cars bad drivers
08-08-2007 | 08:31 PM
#39
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From: Lone Star State
Holy cow! That's a long azz course! Over two minutes!? Where do you guys do your autocross, on a runway? With a big course like that, no wonder you need a full tank of gas! 
Last edited by z-u-later; 08-08-2007 at 08:33 PM.
08-09-2007 | 09:24 AM
#40
Originally Posted by Fluid1
I go with the smallest amount possible. Basically, when the heads-up indicator starts blinking the ----- after it's damn near empty, that's the perfect level. I did 18 runs at that fuel level with no starvation. So I didn't vote on the poll.
Since I have posted this, I started running a full tank.
The extra weight really helps my open rear diff and reduces wheelspin.
Although I'm about 175 pounds heavier with a full fuel load as opposed to empty, I am now faster.