Low fuel level and engine performance
 

Is it just in my head or does the ECU make changes to the engine performance when it notices the fuel tank level is a bit low? (I mean around when the low fuel light comes on or a bit above that).

Do you guys refuel at quarter/half tank left or let it get close to empty?

I never let it go below 1/4 tank. But that is just an OCD thing on my part

I'll second sklimo above. I never go below 1/4. One of those things I'm paranoid about

To answer your question, there are documented cases of fuel starvation while under acceleration and hard cornering below half a tank while forced inducted. I'd imagine that the same issues would present themselves on even a stock car at that low a fuel level.

Glad I'n not the only one!!!

I thought I noticed the difference when moving from a stand still in first gear at traffic lights.

I guess it wouldn't hurt to just refill at a quarter tank and higher like sklimo and dbrandt01 mentioned.

I've also noticed that performance is worse with a low fuel tank. No idea of the cause... I was thinking it was a problem with the fuel injection system, but really have no idea.

I always feel like performance is better when the fuel tank is almost empty...but that may be due to the car being lighter.

Full tank @ ~12gal x ~6 lbs/gal = 72lbs

Almost empty tank @ ~.5gal x ~6lbs/gal = 3lbs

Significant difference that I can feel. When I fill up after running the tank real low, the car definitely feels slower.

No.

Engine performance is only dictated by fuel pressure and the ability to maintain that pressure into the injectors...

So the only way a performance hit will be built in to the ECU software is if the factory fuel tank is prone to have fuel starvation issues to the pump while under normal driving conditions, which may be a fuel tank design issue by itself. But given that this is not an issue, don't worry about it.

-alex

I was wondering the same thing

Most of us who autocross the BRZ/FRS run them with the Empty light on. There is no performance loss or starve that we have seen so far.

Same here. I've had cars that would starve for fuel on an autocross course under certain circumstances at under 1/4 tank, the BRZ isn't one of them.

I run Olivia with the fuel light on average about once a week, sometimes for as much as 25 to 30 miles. I have never noticed a fuel supply or performance issue with it low.

Yes, I like living on the edge. :bellyroll:

I don't know if it's a performance loss or anything but I've noticed the car definitely feels better after filling it up if the tank was previously on E


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