Hi guys,

I'm trying to investigate a long time problem, with my boost. I'm guessing it's a fuel issue.

And I got one question for you guys. When you do donuts (yes, it sounds stupid), does your car stalls when you're low on fuel (60% and lower)? I'm guessing it's not. I also got a fuel cut when boosting on a straight line when I'm 10% full (almost empty). I suppose this last problem is common.

*I got a single turbo with PFC. Fuel damper has been removed 5 years ago (20,000+ miles ago).*

Does my first issue comes from this piece I removed from the fuel tank 2 years ago, because of the free surfaces?

 

Thats a fuel tank baffle...pretty important. When doing donuts which way are you spinning? Clockwise or counterclockwise.

 

Your fuel is sloshing around when you do donuts and you're starving the motor. Same with straight line pulls and low gas.

 

Normal, like he said above. Gas sloshes away from the fuel line in the gas tank, and air gets in the line causing fuel starvation. This wont happen with a full tank.

I had this happen at my last autocross. We had two drivers, and made 11 runs each. Started with a full tank, and ran it to less than 3/4. Got fuel starvation on the last run or two.

 

Counterclockwise usually, but I don't think it will help to go clockwise.

And thanks guys, that's what I thought, the free surfaces.

 

Put the baffle back or get a surge tank. You're going to blow the motor eventually if you keep starving it.

 

"...if you keep starving it" BY DOING DONUTS!!!

 

Good way to blow the engine up by leaning it out during donuts. And removing the anti-slosh baffle? Because of "free surfaces?!?" What does that mean???

Also, boosting the car with 90% of the tank empty, having no anti-slosh baffles in the tank and getting fuel cut under boost for all these reasons. That's pretty dangerous to the engine's health.

Put the baffles back in. That's a good start. Don't boost the car with 10% fuel in the tank. The engine will thank you with years more faithful service in return.

 

What do the drifting guys do? And is that Hotshot fuel sponge thing on the market yet?

 

I think he means the baffle broke loose. The crappy factory spot welds tend to let go over time. Drain the tank, drop it, let it air our for a day or so, and weld the baffle back in.

 

Yes, the baffle broke loose and I'm pretty sure it is in the garbage by now. I'll try not to let the fuel cut happen, you guys are right.

But, to you guys who still have that baffle... You never experience the fuel cut?

 

its not fuel cut its fuel starvation, totally different things.

you will still experience it with baffles. better fluid control will increase resistance to it, but will not eliminate it completely. if you want to eliminate it completely, you need a fuel surge canister.

 

Get another gas tank then.

 

Do not use fuel sponge inside your fuel tank until you're removed every single tiny sharp edge. Missing baffles leave behind edges of sharp sheetmetal.

The fuel sponge will slosh around and shred, and the shredded bits will clog your fuel sock and fuel filters. It also pushed into the fuel level float assembly and messed that up. I did it once - never again.

If you want to try it, solve those problems for certain or else you'll have even worse fuel starvation.

 

I have experienced something similar recently this year. While auto crossing I got what feels like a fuel starvation. When under full throttle there is a quick total loss of power. Enough to make my head lunge forward. I had 1/2 tank of fuel both at both auto cross events. I'm running Hoosier A6 race tires and driving the car very fast. (Fastest time of the day by more than 1 second!) So ther car is certainly experiencing hard side to side loads.

I felt the same thing happen one other time. I had just made a very, I mean very fast run up a mountain road. No problems with the engine. When I got to the top at the end of the road I revved it, dumped the clutch to spin a 180* to get turned around. Right as I got pointed straight ready to take off back down the road, about 5,000 rpm full throttle, I had just barely lifted the throttle to get the tires to stop spinning, then back to full throttle , the engine did that same real quick dying thing. Again, I was leaning my head/ neck into the acceleration and when I lost power my head went lunging forward. I had a camera mounted on the driver side window so I have this recorded.

I had a little less than 1/2 tank of fuel the time on the road. I'm not planning on autocrossing again until July, but when I do I'm going to fill the tank up before and see if that helps the problem.
Car is a 94" touring. Motor built last summer, PFC, simplified sequential twins, 300 rwhp, Ohlins DFV coil overs, always on good tires.