Spin when low on gas ?

[NI-KA]

Can any of you regular "trackers" tell me if the lack of baffles (or to few of them) in the gas tank is a contributor to spinning out in the Viper ?

I have been to the track twice now and everytime I have been at a quarter of a tank or lower I have nearly spun or actually spun.

Fortunately, it has not resulted in anything serious. i.e. no damage to the car - just my ego !

The place it occured last was in a portion of the track where it is "beneficial" (supposedly) to "throw" the vehicle to load the suspension for the turn - relatively low speeds -. One suggestion (from one of the track staff who stated they used to drive a Viper) was that the gas tank lacked adequate baffles resulting in slosh which can create enough momentum to cause a spin - my car is a 2006 coupe.

 

[plumcrazy]

spun as in sideways ? or spun the tires ?

less weight would do help in spinning tires

 

[NI-KA]

Spun as in rotation of the rear-end so that it is front...

Basically ended up doing a 270 by time the car stopped. This occured at relatively low speed - 70mph on a left hand turn.

 

[GTSnake]

Lack of traction over the rear tires due to low fuel level. Have you ever spun when it was a full tank?

I've noticed that my traction is much better with a full tank of gas.

 

[Roadrunner]

Lets say 4.5 gallons left (1/4 of 18gal) at 6lb / gal for gasoline... so if you were to "slosh" hard to one side and then immediately "slosh" to the other side, you would be tossing 27lbs across the rear car. Now if you were at the limit... even a single pound would put you over. But keep in mind 27lbs to the limit is only a small amount of the total traction available.

The effect is much smaller if you were not at a full 1G+ plus opposite turn prior to the "slosh".

You were likely going around anyway...

 

[NI-KA]

No, I have never spun except when low on fuel. Having now experienced the difference with low fuel I can definitely feel the difference overall in the feel of the car. The car has a less firmly planted feeling when down around a qtr. of a tank. I will now be keeping the tank above half.

It does make me curious to know if there are any specific set-ups that minimize this. Aero-kit, 3/4" lower kit, weighting, tire pressure, etc... ?

 

[mjorgensen Woodhouse]

No, I have never spun except when low on fuel. Having now experienced the difference with low fuel I can definitely feel the difference overall in the feel of the car. The car has a less firmly planted feeling when down around a qtr. of a tank. I will now be keeping the tank above half.

It does make me curious to know if there are any specific set-ups that minimize this. Aero-kit, 3/4" lower kit, weighting, tire pressure, etc... ?

Lowering the rear and diminishing the total "rake" will lessen the entry over steer.

 

[NI-KA]

How is "rake" defined? i.e. what do you mean?

Would you lower the rear and leave the front alone?

I am going to guess that to be able to adjust this might be an expensive option?

 

[mjorgensen Woodhouse]

How is "rake" defined? i.e. what do you mean?

Would you lower the rear and leave the front alone?

I am going to guess that to be able to adjust this might be an expensive option?

Rake is the difference in ride height front to rear (front is lower normally). These measurements should be at the frame to ground in between the front wheels and the rear wheels centerlines.

 

[mjorgensen Woodhouse]

Sorry missed the second half. Springs will change this although you have no control of it without adjustable coil overs. Yes can get expensive but if the track is your fun then I would suggest calling and getting the proper set up.

Thanks.

 

[ACR steve]

Suggestion set the car up with a full tank. We always set cars up based on maximum load. Our cars are wheel weal drive ,high horsepower cars. The tendency is to have an over-steer situation due to throttle input or weight transitioning from braking. The car is not having over-steer from 6 gallons of fuel sloshing in the tank. I guarantee it is due to the less weight in the rear due to the lower fuel issue . You need to be smother with the throttle and smoother while transitioning onto the brakes and back to throttle.

Remember you are now lighter in the rear with less fuel and as you apply the brakes there is additional weight being distributed to the front wheels and this compounds creating over-steer.

There also may be trailing throttle over-steer where you snap out of the gas reducing the load from acceleration to the rear wheels when you get out of the gas. This will induce over-steer.

Key is to be as smooth as possible on the transition from brake to throttle , especially with a quarter tank. Try and use the brake and throttle to help steer the car rather then fighting it with the wheel. The key is seat time. By the way I would not let the car go to much past a quarter tank on the track ,I have heard of fuel starvation issues and fuel pumps burning out from repeted low fuel issues

 

[NI-KA]

Thanks for the advise!

The fuel starvation issue was also mentioned out at the track the other day. Its good to get confirmation here from confirmed Viper people.

Just prior to the "spin" I was monitoring my fuel guage and it was showing 1/8 of a tank. After I got off the track and looked at the guage it was showing 1/4 of a tank. Obviously, the fluid shifts quit a bit while moving through the track.