Fellow autocrossers,

Took my '07 TC to its first autocross on Sunday up at the Boeing lot in Everett. The car was great fun accept for one issue. With a 1/4 tank of fuel I had severe fuel starvation in right hand corners. That discovered I filled it to a 1/2 tank indicated and experienced the issue again, but only in one spot on course. After yet another trip the gas station and now with 2/3 indicated the problem was solved. Well sort of. I'm now hauling around a lot of extra weight! I'd like to find an "H Stock" class legal fix for this as I'm getting ready to spend a bunch of $ on lightweight wheels, R compound tires, and a lightweight exhaust.

Thanks for your help,

Autoxer

 

Anything you could do to fix the problem would take you out of HS. That is just a shortcoming of the car.

I've run 30+ events on R-compound tire and tires and other goodies. You will want to be at 3/4 of a tank when you have your R's installed. They generate much higher G's and slosh the gas even more.

Even with the down side having to carry around more fuel it is still a very competitive HS car.

 

I was hoping for a TSB from Scion. Oh well.

What have you done to your tC? Shocks? Sway bar? Wheels? Alignment? I'd rather learn from others instead of making a bunch of mistakes on the way to success.

Thanks

 

HS mods include:

2006 tC
Front Hotchkis Sway Bar (set soft)
Rear TRD Sway Bar (set hard) yes it is class legal
Front TRD pads
TRD air filter
Magnaflow Catback
17x7 Motegi Track_Lite Wheels
245/45 Kumho V710 40 psi front 45 psi rear

This season I'm going to start my alignment off at -1.5 front camber and -0.5 rear with 0 toe front and rear.

When it comes to shocks. I will be working with one my customers that is running the same setup on his tC plus the TRD shocks. My car with stock shocks should give us a good baseline comparison on how big of a difference the shocks can make. If it is .3 seconds or more I will have to have them on my car.

Hope this helps.

 

Thanks so much. Yes that does help. I picked up a set of brand new (stock) tC shocks and springs yesterday evening. I'll be ordering Konis today. I'm still on the fence about "17 or "18 inch wheels.

 

OK, I just realized you said V710, 245/45/17's on 7" wheels. Does that size fit well on a 7" wheel? That's a lot of rubber for HS!

 

Suprisingly yes. Everybody told me that a tire that wide would be pinched on a 7" rim, but it's not. Work great grip for days and very little ABS action.

Hell yeah! I'm running as much or more rubber than anybody I know in HS except for the Tacoma XRunners.

 

wait i'm very surprised to hear the rear sway (even TRD from the manufacturer) is stock legal, does that mean that the TRD shocks and springs are as well? (edit, obviously the shocks are but i'm curious about the springs)

 

Unfortunately the springs are not allow. The TRD RSB and TRD Front Strut Tie Bar are allowed because anybody could have ordered their tC from the factory with that equipment on the car and on the Monroney LabeL (window sticker).

The TRD springs on the other hand, are added to the car only after it gets to the dealership and therefore does not qualify as a "factory option".

But hey, a TRD RSB is more than most "stock" cars have to work with.

 

man, that sux, i run 1/4 tank or less when i auto-x and have no problems

 

i have had the "starvation" issue in my 05 ever since i have been auto-x'ing.. this will be my third year.. i pretty much only keep it around at 3/4 or a full tank due to this...

 

Three of us drive the car at events so I fill it and try not to think about all that extra weight. :-)

 

I always do fuel management the week of the auto-x, so I get there w/ about 1/4 tank or less.

 

So I'm seeing that nobody with an xB is having this problem. What is a good amount to have in the tank with the xB? I'll be running my box for the first time on the 24th of March.

 

some1 told me as a rule of thumb to run 1/4 or less, or full

 

just another mention of the fuel issue, it's only happened to me on one corner at one event because it was a high speed, decreasing radius right hand turn, and I had about a half a tank of gas and noticed an obvious power loss until I straightened out the car again, and I knew it was the fuel but I was hoping it was a one-time thing and it wouldn't happen on my 3rd run, well it did again, and it killed literally 2 seconds off my 50 second run, so I asked the officials if I could make a gas run, I did, came back with 3/4 tank (which solved the issue) and ran the best time I ran that day and pulled 1st place in my class

I looked at a part's list blow-up of the TC's gas tank, and where the pickup is, and the way the tank is shaped will cause the issue when it sloshes to the left from a severe right-hand turn. I've not experienced it when turning left, and neither has anyone I know, and the way the tank is shaped, left-hand turns shouldn't be a problem.

Again, any inline fuel pump or booster or the like will take the car (legally anyways) out of H-Stock.

 

wow thats pretty crazy, been to many events never noticed this problem,but i should pay more attention.

 

i know i can easily look it up but maybe you can just tell me

any of those type of modifications STX legal?

 

I always fill up my tank before I go racing. Yes, I have a little bit more weight, but it really helps out in the corners. With a full tank, the weight stays (for the most part) stationary. With a 1/4, 1/2, 2/3, etc. filled tank, every time you go into a corner, accelerate, brake, etc. the fuel sloshes around affecting the balance of the car.

Think of it this way, a gallon of gasoline weights approximately 5.8 to 6.5 pounds depending on the temperature. A half tank of fuel would weigh approximately 42lbs (8gal * 6lbs) where a full tank would weigh approximately 84lbs (14gal * 6lbs).

Now, an average bowling ball weighs approximately 15 lbs. A half tank of fuel would be equivilant to about 3 bowling ***** and a full tank would be about 5 and a half...we'll call it 6 ***** with one being a 7.5 pound kid's ball.

Imagine going to the track with the bowling ***** in your hatch. The 3 ***** are just put in the hatch to roll around (much like the fuel can slosh around). Or, you can put your 6 bowling ***** in a bag to keep them together (like a full tank).

Think of braking, going into a hard corner, then accelerating out of it with 3 bowling ***** in your hatch. That much weight moving around will affect your handling. Now, at the expense of being a little heavier (which will increase traction), you have the 6 ***** stationary in your hatch, not rolling around. Your car will be much easier to control when doing aggressive driving.

Think about that the next time you go to the track.