Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 22nd April 2010, 07:55   #1
Senior - BHPian
 
greenhorn's Avatar
 
Join Date: Apr 2007
Location: TN-14
Posts: 6,833
Thanked: 1,309 Times
Default More pickup with a full tank?

I'm not sure if my mind is playing tricks on me, but Recently I've noticed that my pickup improves drastically after I tank up. From what I read, it might be because my pump is acting up.

But i got my pump serviced just a few months ago.

What else could be at fault?
greenhorn is offline   Reply With Quote
Old 22nd April 2010, 09:30   #2
Senior - BHPian
 
sumeethaldankar's Avatar
 
Join Date: May 2007
Location: Mumbai
Posts: 2,668
Thanked: 1,018 Times
Default

I notice i drive fast when i have a full tank and slower when i am reaching the empty mark.For me seems more like a physcological thing that having more fuel in the car makes me seem to want to drive zippy without worrying about running out of fuel.

Do you feel the same when you have half tank of gas in the car ? , i mean if your fuel pump is acting up , even a half tank will do.
sumeethaldankar is offline   Reply With Quote
Old 22nd April 2010, 09:57   #3
Senior - BHPian
 
prince_pervez's Avatar
 
Join Date: Dec 2006
Location: Redwood shores, CA, USA
Posts: 4,205
Thanked: 30 Times
Default

On first thought the pick up should decrease as a result of more load at the back. I don't know about the others but my cars have returned exceptional mileage on full tanks. I have never noticed an increase in the pick up.
prince_pervez is offline   Reply With Quote
Old 22nd April 2010, 10:11   #4
Team-BHP Support
 
Jaggu's Avatar
 
Join Date: May 2004
Location: Bangalore
Posts: 17,742
Thanked: 7,449 Times
Default

Quote:
Originally Posted by greenhorn View Post
I'm not sure if my mind is playing tricks on me, but Recently I've noticed that my pickup improves drastically after I tank up. From what I read, it might be because my pump is acting up.

But i got my pump serviced just a few months ago.

What else could be at fault?
LOL unless you have a heavily clogged fuel filter or a pump which is really weak/poorly calibrated, this shouldn't happen except in your mind.

Quote:
Originally Posted by prince_pervez View Post
On first thought the pick up should decrease as a result of more load at the back. I don't know about the others but my cars have returned exceptional mileage on full tanks. I have never noticed an increase in the pick up.
Better mileage can happen, especially in summer coz vapor loss will be minimal when the tank is close to full.
Jaggu is online now   Reply With Quote
Old 22nd April 2010, 10:40   #5
Senior - BHPian
 
ghodlur's Avatar
 
Join Date: Sep 2009
Location: Thane
Posts: 5,038
Thanked: 2,075 Times
Red face

Even I have observed after I do tank full, the engine becomes a lot more smoother, the gear shifts are slick and smooth, the DTE variations are very minimal. As the fuel reaches half tank capacity, I can feel a noticeable diff in gear shifts, the engine a bit groaning and DTE going haywire.
I am unable to know the logic behind this or is this just a figment of my imagination??
ghodlur is offline   Reply With Quote
Old 22nd April 2010, 11:16   #6
BHPian
 
akash_m's Avatar
 
Join Date: May 2007
Location: Noida
Posts: 246
Thanked: 88 Times
Default

+1 to that. My swift behaves much better with tank full of petrol. With petrol near the 'E' mark (with still 5-8 litres remaining), the pickup and power seems to drop.

Is this technically justified or just an illusion?


Last edited by akash_m : 22nd April 2010 at 11:17.
akash_m is offline   Reply With Quote
Old 22nd April 2010, 11:27   #7
Senior - BHPian
 
aargee's Avatar
 
Join Date: Jan 2010
Location: KATN
Posts: 4,694
Thanked: 2,105 Times
Default

Was watching this thread for sometime before I could say something which I thought would be considered funny, but now I'm convinced that my observations are inline with most of you people. With a full tank, here're my observations...
1. The needle comes to half mark after a very long drive, but from half to empty its faster. Jaggu - would appreciate if you can help me understand the vapour loss concept.
2. The car is butter smooth with gears shifts are slick smooth & its not this smooth when the fuel is at E. Even the engine noise can be hardly heard when the tank is full.
3. Pickup - I haven't really noticed, but will try to notice during my next full tank
4. Big lesson learned is, never fill up the tank 1 or 2 days before a long drive even though the car is parked under shade. Just fill the tank the night before the long drive & the vapour loss will be less.
5. Long drive mileage increases if the tank is loaded completely rather than starting at half & topping up the tank in between.
aargee is offline   Reply With Quote
Old 22nd April 2010, 11:45   #8
BHPian
 
Exhaust_Note's Avatar
 
Join Date: May 2009
Location: Goa
Posts: 169
Thanked: 18 Times
Default

Since a long time (years) I have been noticing the same but dismissing it as "in-the-mind". Not only cars, my old bajaj M-80, current gladdy and wagon-R all display a enhanced refinement and smoothness after a tank up.

Could it be because when the fuel level drops, the physical impurities/contamination are more (as in ppm/ density) and hence the roughness? But when fresh fuel in added there is a churn and the fuel reaching the engine is actually better?

@aargee - +1. Keeping the car parked for long time with full tank have been known to cause fuel pump issues. Not 100% sure about it though.

Last edited by Exhaust_Note : 22nd April 2010 at 11:46.
Exhaust_Note is offline   Reply With Quote
Old 22nd April 2010, 11:48   #9
k36
BHPian
 
k36's Avatar
 
Join Date: Dec 2005
Location: Pune
Posts: 133
Thanked: 19 Times
Default

I have the same experience with my Swift Petrol. Full tank gives better pickup, smoother drive and better gearshift than a less than tank close to empty.

I've been thinking about it on and off but just brushed the thought aside as an illusion. It is a surprise now that so many of us are getting the same experience!
k36 is offline   Reply With Quote
Old 22nd April 2010, 12:01   #10
Senior - BHPian
 
Gansan's Avatar
 
Join Date: May 2009
Location: Chennai
Posts: 3,426
Thanked: 875 Times
Default

I have noticed this for more than two decades in my bikes, and more recently in my car as well. In the bikes it could be partly explained as the fuel flows by gravity and/or by the pressure the fuel remaining in the tank exerts. But in cars?

I always fill a full tank and will go for a refill when the fuel level comes to reserve in bike and near the E mark in car. This takes around a month. May be the fuel partly loses it's octane rating towards the end of this cycle and regains when I top up the tank, leading to the smoothness and better pick-up?
Gansan is offline   Reply With Quote
Old 22nd April 2010, 12:16   #11
Team-BHP Support
 
Jaggu's Avatar
 
Join Date: May 2004
Location: Bangalore
Posts: 17,742
Thanked: 7,449 Times
Default

Quote:
Originally Posted by aargee View Post
1. The needle comes to half mark after a very long drive, but from half to empty its faster. Jaggu - would appreciate if you can help me understand the vapour loss concept.
===========
4. Big lesson learned is, never fill up the tank 1 or 2 days before a long drive even though the car is parked under shade. Just fill the tank the night before the long drive & the vapour loss will be less.
1- Fuel gauges never work in a linear fashion. So unless we have a digital gauge units, don't think it will ever give you accurate level reading based on consumption. I think you already know the vapor loss concept, refer point 4??

Simple terms, with more vacant space in tank, fuel has more space to vaporize as it heats up and hence chances of loss. With new age sealed fuel system this is restricted to a minimum. Thanks to news emission norms, which include fuel and lubricant emissions if am not mistaken
Jaggu is online now   Reply With Quote
Old 22nd April 2010, 12:19   #12
BHPian
 
Join Date: Feb 2009
Location: KL41-MH14
Posts: 79
Thanked: 18 Times
Default

This is great and strange stuff.

I almost never drive with tankfull of petrol so cant comment. I live form pump to pump. Basically its because vehicles get borrowed a lot and ppl dont fill petrol if its more than half full.

But if what you guys are saying is true i think its time i changed my filing habits.
Any theories on why this happens?

I can understand the better mileage part but slicker shifts? how is that happening

Last edited by Dippy : 22nd April 2010 at 19:57. Reason: Correcting spelling great
Joe-Ker is offline   Reply With Quote
Old 22nd April 2010, 12:24   #13
Distinguished - BHPian
 
jkdas's Avatar
 
Join Date: Sep 2005
Location: Thiruvananthapu
Posts: 9,661
Thanked: 1,389 Times
Default

Might for old carb-walla ones ; gravity plays

Like sumeeth said, should be physcological. You cant fool the electronic stuff these days by default.

And it should be slower coz of extra weight.

Emm, another thought, maybe its like how Pete's box works; what did you fill in? air? So the ECU sees more air and hence pushes more fuel ...

This was fun.
jkdas is offline   Reply With Quote
Old 22nd April 2010, 12:28   #14
Senior - BHPian
 
Gansan's Avatar
 
Join Date: May 2009
Location: Chennai
Posts: 3,426
Thanked: 875 Times
Default

Quote:
Originally Posted by jkdas View Post
Might for old carb-walla ones ; gravity plays
Even for cars fitted with carburettors, how can gravity play a part? It holds good only for bikes, whether carb or FI!
Gansan is offline   Reply With Quote
Old 22nd April 2010, 12:32   #15
Senior - BHPian
 
aargee's Avatar
 
Join Date: Jan 2010
Location: KATN
Posts: 4,694
Thanked: 2,105 Times
Default

Quote:
Originally Posted by Gansan View Post
Even for cars fitted with carburettors, how can gravity play a part? It holds good only for bikes, whether carb or FI!
+1.

Quote:
Originally Posted by jkdas View Post
Might for old carb-walla ones ; gravity plays
Even I didn't understand this point. From my understanding, all the cars have the fuel tank in the rear & the fuel pump helps to flow the fuel from the rear end to the front, so how does gravity play a role? Appreciate if you could help us understand.


Quote:
Originally Posted by Jaggu View Post
Simple terms, with more vacant space in tank, fuel has more space to vaporize as it heats up and hence chances of loss. With new age sealed fuel system this is restricted to a minimum. Thanks to news emission norms, which include fuel and lubricant emissions if am not mistaken
Thanks I got the point. But have one more question. Vapourization happens due to heat, how does empty space matter? As long as the heat is sufficient to vaporize the fuel, the fuel will evapurate no matter there's empty space on the gas tank right? Pls guide me, if I'm incorrect here.

Last edited by aargee : 22nd April 2010 at 12:33.
aargee is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
One Full Tank on my Black Beauty: Bangalore - Guruvayur -Bangalore: Verna CRDI SX VarunM Travelogues 18 4th May 2012 22:43
Engine Stalls and shuts down during de clutch ONLY with GAS TANK FULL in Accent darthvader5000 Technical Stuff 20 7th May 2009 19:59
MPFI Esteem missing with full tank. bhogalrajnish Technical Stuff 6 20th November 2007 17:58


All times are GMT +5.5. The time now is 06:18.

Copyright ©2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks