car feels slow when the tank is full?

harp00n · 12-23-2011, 03:41 PM

My problem is when my tank of fuel is full - my throttle feels really sluggish and slow. But when the tank is almost empty throttle feels VERY sensitive (like it should be from the factory, I guess). And it is not because of the additional fuel weight, if a big friend of mine sits in my car when the tank is almost empty - throttle is still very sensitive

My only guess is fuel pump, as I cleaned it several times (here we have very dirty gasoline sometimes), but I can't imagine why

Maybe it is somehow connected with the self-learning ecu?

fuzzywuzzy · 12-23-2011, 05:14 PM

Gas weighs 6-7 lbs per gallon. Multiply that times 19 (our tanks capacity) and its a decent amount of weight.

christian370z · 12-24-2011, 02:16 AM

^Yep, gas weighs a lot. I always keep my tank around a half tank or under just to keep weight down a bit.

ImportConvert · 12-24-2011, 02:47 AM

I move slower after a big meal, too.

harp00n · 12-24-2011, 04:50 AM

Maybe my EVAP system is dirty or something is wrong with it. Has anybody dealt with it?

Jordo! · 12-24-2011, 05:15 AM

Any chance you are occasionally using a lower than recommended octane? If so, the ECU might be pulling some timing.

EVAP problems should set a check engine light -- is that on?

nmjaxx9 · 12-24-2011, 11:23 AM

Quote:

Originally Posted by ImportConvert

I move slower after a big meal, too.

roy'sz · 12-24-2011, 01:20 PM

Try running race fuel and see if it helps

harp00n · 12-25-2011, 03:50 AM

the problem is that it is not 100% consistent, so I can have laggy throttle pedal when the tank is almost empty, but most of the time it happens when the tank is almost full or at 3/4, 2/3... there is some connection, I'm sure!

maybe I should do this ITB: Knowledgebase - Infinitihelp.com Forums - VENT CONTROL VALVE REPLACEMENT ?

MattP725 · 12-25-2011, 08:11 AM

I'd still attribute it to the weight. I actually have heard that a gallon (of water at least) is closer to 8-10 lbs so when adding 15-18 gallons you might be adding the weight of another person pretty easily.

370Zsteve · 12-25-2011, 08:36 AM

Quote:

Originally Posted by christian370z

^Yep, gas weighs a lot. I always keep my tank around a half tank or under just to keep weight down a bit.

You are promoting rust and condensation in the upper half of your tank, then.

christian370z · 12-25-2011, 12:44 PM

Quote:

Originally Posted by 370Zsteve

You are promoting rust and condensation in the upper half of your tank, then.

Not when the fuel is constantly getting sloshed around during driving, that can't really happen. Unless the car is going to sit for a while, then it absolutely could promote condensation and rust.

cdoxp800 · 12-25-2011, 01:38 PM

Weight of 1 US Gallon of Gas = approx. 6.073 lb

So 6.073 lbs X 19 Gal = 115.387 Lbs

fuzzywuzzy · 12-25-2011, 08:35 PM

Quote:

Originally Posted by Jordo!

Any chance you are occasionally using a lower than recommended octane? If so, the ECU might be pulling some timing.

what octane are you running? Please dont say less than 93

Quote:

Originally Posted by MattP725

I'd still attribute it to the weight. I actually have heard that a gallon (of water at least) is closer to 8-10 lbs so when adding 15-18 gallons you might be adding the weight of another person pretty easily.

gas is lighter than water

Quote:

Originally Posted by 370Zsteve

You are promoting rust and condensation in the upper half of your tank, then.

really??? how does plastic rust???

Waiz · 12-25-2011, 09:28 PM

Your butt dyno needs recalibration, this is a farse.

12-23-2011, 03:41 PM	#1 (permalink)
harp00n Base Member Join Date: Sep 2011 Location: Kharkov, Ukraine Posts: 43 Drives: G35x '07 Rep Power: 13	car feels slow when the tank is full? My problem is when my tank of fuel is full - my throttle feels really sluggish and slow. But when the tank is almost empty throttle feels VERY sensitive (like it should be from the factory, I guess). And it is not because of the additional fuel weight, if a big friend of mine sits in my car when the tank is almost empty - throttle is still very sensitive My only guess is fuel pump, as I cleaned it several times (here we have very dirty gasoline sometimes), but I can't imagine why Maybe it is somehow connected with the self-learning ecu?

12-24-2011, 02:16 AM	#3 (permalink)
christian370z A True Z Fanatic Join Date: Jul 2010 Location: Newport Beach Posts: 3,900 Drives: 2010 370Z/Saab 900se Rep Power: 431	^Yep, gas weighs a lot. I always keep my tank around a half tank or under just to keep weight down a bit. __________________ -320whp / 259wftlbs- SP Rays -- RE-11s -- SpecialtyZ Tune -- Swift Springs -- Stillen 25R Oil Cooler -- Stillen G3 Intakes -- Berk HFCs -- F.I. 12" CBE -- Stillen Sway Bars -- Es14 Spring -- INGS+1 lip -- CF Spoiler -- GTR Start Button -- VLED Parking Lights -- PWJDM V2 shift knob

12-24-2011, 05:15 AM	#6 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 417	Any chance you are occasionally using a lower than recommended octane? If so, the ECU might be pulling some timing. EVAP problems should set a check engine light -- is that on? __________________ Enjoy it. Destroy it.

12-25-2011, 01:38 PM	#13 (permalink)
cdoxp800 A True Z Fanatic Join Date: May 2009 Location: FL Posts: 1,337 Drives: 2011 Nismo Rep Power: 19	Weight of 1 US Gallon of Gas = approx. 6.073 lb So 6.073 lbs X 19 Gal = 115.387 Lbs __________________ 2011 Brilliant Silver NISMO 370z. #: 0046. PPE LTH \| MillSpec Cats \| F.I Exhaust \| Akuma Intakes \| Rotora 6/4 Brakes

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12-23-2011, 05:14 PM	#2 (permalink)
fuzzywuzzy Base Member Join Date: Apr 2010 Location: In a house Posts: 211 Drives: 370z Rep Power: 15	Gas weighs 6-7 lbs per gallon. Multiply that times 19 (our tanks capacity) and its a decent amount of weight.

12-24-2011, 02:47 AM	#4 (permalink)
ImportConvert A True Z Fanatic Join Date: Jun 2010 Location: SWMO Posts: 4,454 Drives: 2019 CX5 GT Reserve Rep Power: 7626	I move slower after a big meal, too.

12-24-2011, 04:50 AM	#5 (permalink)
harp00n Base Member Join Date: Sep 2011 Location: Kharkov, Ukraine Posts: 43 Drives: G35x '07 Rep Power: 13	Maybe my EVAP system is dirty or something is wrong with it. Has anybody dealt with it?

12-24-2011, 01:20 PM	#8 (permalink)
roy'sz A True Z Fanatic Join Date: Aug 2011 Location: palmdale, ca Posts: 1,299 Drives: 2010 nissan 370z Rep Power: 15	Try running race fuel and see if it helps

12-25-2011, 03:50 AM	#9 (permalink)
harp00n Base Member Join Date: Sep 2011 Location: Kharkov, Ukraine Posts: 43 Drives: G35x '07 Rep Power: 13	the problem is that it is not 100% consistent, so I can have laggy throttle pedal when the tank is almost empty, but most of the time it happens when the tank is almost full or at 3/4, 2/3... there is some connection, I'm sure! maybe I should do this ITB: Knowledgebase - Infinitihelp.com Forums - VENT CONTROL VALVE REPLACEMENT ?

12-25-2011, 08:11 AM	#10 (permalink)
MattP725 A True Z Fanatic Join Date: May 2011 Location: Toms River, NJ Posts: 1,904 Drives: 2010 40th Rep Power: 16	I'd still attribute it to the weight. I actually have heard that a gallon (of water at least) is closer to 8-10 lbs so when adding 15-18 gallons you might be adding the weight of another person pretty easily.

12-25-2011, 09:28 PM	#15 (permalink)
Waiz A True Z Fanatic Join Date: Apr 2010 Location: SoCal Posts: 9,262 Drives: Z33 & GE8 Rep Power: 459	Your butt dyno needs recalibration, this is a farse.