Low fuel level and engine performance - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

whatsinaname · 10-21-2013, 09:40 AM

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?

sklimo · 10-21-2013, 09:43 AM

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

dbrandt01 · 10-21-2013, 10:03 AM

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

Frostyman · 10-21-2013, 10:09 AM

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.

sklimo · 10-21-2013, 10:13 AM

Quote:

Originally Posted by dbrandt01

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

Glad I'n not the only one!!!

whatsinaname · 10-21-2013, 11:00 AM

Quote:

Originally Posted by Frostyman

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.

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.

Flow · 10-21-2013, 01:27 PM

Quote:

Originally Posted by whatsinaname

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'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.

muffinz · 10-21-2013, 01:51 PM

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.

mav1178 · 10-21-2013, 02:21 PM

Quote:

Originally Posted by whatsinaname

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).

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

brzadrian · 10-22-2013, 10:19 PM

I was wondering the same thing

2superblus · 10-23-2013, 12:34 PM

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.

Miniata · 10-23-2013, 08:56 PM

Quote:

Originally Posted by 2superblus

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.

Dadhawk · 10-24-2013, 08:13 AM

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.

TIsbell34 · 12-01-2013, 07:43 PM

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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10-21-2013, 09:40 AM	#1
whatsinaname Member Join Date: Aug 2013 Drives: 1998 Ford ZX2 Location: Ann Arbor Posts: 67 Thanks: 0 Thanked 26 Times in 12 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	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?

10-24-2013, 08:13 AM	#13
Dadhawk 1st86 Driver! Join Date: Feb 2012 Drives: '13 FR-S (#3 of 1st 86) Location: Powder Springs, GA Posts: 19,841 Thanks: 38,891 Thanked 24,990 Times in 11,398 Posts Mentioned: 182 Post(s) Tagged: 4 Thread(s)	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. __________________ Olivia 05/03/2012 - 01/06/2024. 231,146 glorious miles. Visit my Owner's Journal where I wax philosophic on all things FR-S Post your 86 or see others in front of a(n) (in)famous landmark. What fits in your 86? Show us the "Junk In Your Trunk".

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10-21-2013, 10:03 AM	#3
dbrandt01 Senior Member Join Date: Aug 2013 Drives: none Location: N/A Posts: 411 Thanks: 185 Thanked 229 Times in 140 Posts Mentioned: 16 Post(s) Tagged: 0 Thread(s)	I'll second sklimo above. I never go below 1/4. One of those things I'm paranoid about

10-21-2013, 01:51 PM	#8
muffinz Senior Member Join Date: Sep 2013 Drives: 2013 DGM BRZ Ltd Location: New York Posts: 184 Thanks: 84 Thanked 97 Times in 49 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	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.

10-23-2013, 12:34 PM	#11
2superblus Senior Member Join Date: Sep 2012 Drives: 13 BRZ WRB Location: Wiscowsin Posts: 269 Thanks: 71 Thanked 132 Times in 78 Posts Mentioned: 6 Post(s) Tagged: 0 Thread(s)	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.

12-01-2013, 07:43 PM	#14
TIsbell34 Member Join Date: Oct 2013 Drives: 2013 FR-S Location: AL Posts: 12 Thanks: 2 Thanked 2 Times in 1 Post Mentioned: 0 Post(s) Tagged: 0 Thread(s)	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 Sent from my iPhone using Tapatalk

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