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-   -   Max kmpl , and how to achieve it (https://www.team-bhp.com/forum/technical-stuff/28072-max-kmpl-how-achieve-10.html)

i had the more recent vehicles in mind when i mentioned the computer thing in my earlier post.

i try to get max kmpl as if it is a game to entertain myself.. to anticipate while driving so i can get max KMPL. it is amazing how much difference it makes. i get between 16 to 17 KMPL with my Laura manual on my daily city commute of 40KM in Bangalore.. whereas my wife's driver gets 11ish with the same car, same conditions.. which is what i was also getting before i started playing this game of getting max kmpl. the actual KMPL figure might slightly less than what is displayed by the on-board computer but the improvement is for real.

i realized i don't have to press the accelerator 60% of the time in bangalore traffic - and nobody can tell that i am driving like a granny never touching the pedal!! BTW, Laura is fantastic for low RPM, high-gear driving in city with minimal engine braking whereas I have to stand on top of the accelerator pedal all the time in my Corsa!!

Really? I have always feared as much but since I have seen these products from reputed companies such as 3M, etc. I thought they do what they claim.

i have seen many engines ruined due to engine de carbonising,,< though none of the product was a 3m>
instead use acetone /system g in 2.5 ml per litre on regular basis in petrol ,
use 8-10 % of system d in diesel , directly fix it to inlet od the pre diesel filter and run the engine on varying speeds and loads<purging> its safe, effective, and cost effective too <250 rs for the sys d and 40 rs for the diesel

When we have to stop car at lights/jam for about 1 min to <2 min, is it good to switch off to save fuel?

If it is more than 2 min, of course its good to switch off and if <1 min its good to keep it on.

Also, in bumper-to-bumper traffic conditions, many times I drive in 1st gear, sometimes I think of switching to 2nd, but seeing few meters ahead a vehicle & I will have to stop behind it, I continue in 1st gear in 20 kmph or little more speed, what is good to do here (switch to 2nd or continue in 1st)?

There's so much more to driving styles that could be done before attempting something darastic with the plumbing on the car etc.!

Coasting in nuetral for one,..I've genuinely tried it & it works. On NH8 (Ggn-Del) streatch. At the exit of every flyover at 90kmph, slip it in nuetral and you maintain 80 for at least a couple of km,..engage 5th when you hit 65-70, and gentle on the gas again.

I've streatched the liter from 14 to 17 by just coasting wherever possible, even when anticipating a red light or turn.

Coasting in Neutral is an absolute NO-NO. In Neutral you would have much less control on the car than in gear and the breaking distance also increasing when in Neutral. So please do not coast in Neutral just to save an ml or two of petrol. It isn't worth it.

my car manual says switch off if idling more than 60 seconds for better FE - which is what i do. if i am not sure of the time - i switch off - which turns out to be the right decision more than 90% of the time. it also cheers u up if the signal takes really long to turn green :-)

bumper to bumper traffic: this is where you can make a huge difference to your FE. a lot depends on the car and its transmission. as you become more confident and understand your car better you will learn to drive in the highest gear possible - assuming you are aiming for max FE. following steps help me:

1. in bumper-to-bumper traffic, coast in neutral as much as possible if the speed is < 5kmph. engage in gear just to get some momentum. also saves clutch.

2. NEVER accelerate/rev in 1st gear. u get worst FE in this. In fact, rapid acceleration in any gear should only be used in exceptional cases. not to drive for more than 2-3 meters in 1st gear for better FE.

3. Avoid quick "accelerate/brake" cycles. You are creating rapid "acceleration/deceleration" which essentially "drinks fuel/kills brake pads" without making any difference to your average speed. instead anticipate the average speed of the traffic and maintain it in the highest gear possible. Don't touch the accelerator pedal unless your speed is falling below the average speed of the traffic. my car has a nice foot rest next to the accelerator pedal also.

i am not crazy about FE, but it is a good thing to aim for better FE - it will make you a more mature driver (less aggression) and it makes the daily commute less 'hateful'

very true. It would have been a better place out there if eveyone knew this. ANd just imagine the amount of fuel that could be saved just at one junction. If you look a the bigger picture its quite very interesting and world saving:)

It absolutely makes sense to turn off engine while waiting for long periods at lights, in theory. This means no A/C and windows down while waiting at signal, inhaling all kinds of gas cocktail is the last thing one wants. Does any one have a solution to this ? It goes without saying I do not turn off engine while waiting at traffic lights, would like to hear how people manage to switch off engine.

If stop time is more than 60 minutes, I switch off the engine and turn on the keys to keep the AC blower running. It help s for next 1 - 2 minutes, I start the engine if I start getting stale air.

cheers,

Hi guys, I've tried the switch-off-engine-if-idle-more-than-60-seconds routine. And yes, I did get 80 Kms more per tankful ! But a few weeks after my triumph, my battery gave out on me ! I'm convinced the increased number of starts contributed to the demise of my battery - the battery was then a couple of years old. I'm not sure I saved enough by way of fuel costs to offset the price of a new battery.

To those who're interested, my drive to work is around 6.5 Kms, & I have to endure 6 traffic lights in that distance, most stay red for 90 seconds, the rest are 180 second lights. Anyways, if you're planning to try this routine, ensure your battery's up to the task...

A very good point brought out. Is it the number of starts or battery use when the engine is off, that made the battery drain prematurely.

I went thru this thread and its very informative of you Turbosam for sharing your findings and knowledge.

I tried the inertia stuff of FE just as an experiment and the results are good.

as usual filled up 62.5ltrs till Fuel Warning Light glows = 375kms = FE of 6kmpl (city / highway 50/50%)

Turbosam @ Maintaing the constant light throttle in city, no hard acceleration,

highway speed betwwen 90 / 110kmph (prior to this i would maintain same 90 / 110kmph cruising but this time i used the tech of gradual acceleration thereby not getting to 100kmph in under 12 to 15 seconds but gentle on throttle and maintianing it then)

No speed burst and not crossed above 110kmph all through the run.

RESULT:
Advantage = Gain of 146kms Fuel Light has just started to glow = FE approx 8.32kmpl
Disadvantage = Need alot of nerve to control the desire to press the throttle and also to change ur driving style.
Also u have to keep constant watch on the rearview in braking and ""gradual accelerating"" situations.

Overall its very good on a Long Drive if u are in no hurry!!

check out the wattage of the startor motor .. if its a 80+bhp car it will be having the rating @1500 watts.
cranking currend drawn is @350-450 amps
take the startor efficiency in to consideration<@50>...<3000 watts>
take the battery's efficieny of converting chemical energy in to electrical energy ,25%>@
then take batterys efficiency to convert the charging current in to chemical conversion!<@28-30%>
then consider the alternator's efficiency to convert the mechanical rotery motion into electrical energy at low rpm in traffic!!!
then consider the frictional losses in the belt and pully arrangement!
then consider the mechanical efficiency of the i.c. engine MAX-25% AT MAX TORQUE RPM AT FULL THROTTLE AT MAX PAY LOAD .. so in traffic it will be @ 10 -12% to the max
and u are trying to save just some ml of fule ... ha ha ha < just trying to be funny in a loose loose battel of fuel crysis>:Frustrati

thanks a lot .. either way we -the fossil fuel heads- are not going to stop using the cars till we die!!
bu we can sure save some bit of fuel where and whnenever we can .
afterall we the tech inclined people should take the first step towards saving the fuel+environment +keep the fossil fuelled cars running!!
lol: