The online racing simulator
What's your fuel efficiency?
(71 posts, started )
Quote from Gunn :My point is: fuel usage is not based on distance driven, it is based on throttle use (or revs, probably). I manually blip the throttle so I would most likely use more fuel per lap than someone who didn't blip. Wheel spin was mentioned too, and that makes a noticeable difference to fuel usage over a long race. Time spent revving in the gravel traps is another example.

blipping the throttle won't make a big difference

when the engines under load it's going to make the biggest difference to fuel use



Quote from JTbo :Certainly engine has to be using fuel when idling, how else one could run out of fuel in first place? If LFS does not use fuel when idling then there is a bug.

If throttle is not touched there still is some throttle applied, via idle valve or some other way, fuel is also cut only if engine braking is strong enough, LFS should take these into account when calculating fuel consumption. For carbs it is different, but hopefully those can be forgotten from LFS

fuel shouldn't be cut at any time or the engine will stall

and yeah you're right, if the cars are EFI which i think most are, the throttle butterfly's will stay open a slight ammount at idle.

(if you're bored at home you can mess with the idle screw on your own cars throttle body, get it idleing at 3k for a laugh )
#52 - Gunn
Quote from danben7 :blipping the throttle won't make a big difference

Nobody said it would make a big difference. Thanks for telling me what I already know.
#53 - JTbo
Quote from danben7 :blipping the throttle won't make a big difference
fuel shouldn't be cut at any time or the engine will stall

and yeah you're right, if the cars are EFI which i think most are, the throttle butterfly's will stay open a slight ammount at idle.

(if you're bored at home you can mess with the idle screw on your own cars throttle body, get it idleing at 3k for a laugh )

No engines won't stall if fuel is cut at engine braking, most of FI cars do have it, some of carb cars have it, my fun car has programmable FI so I can set fuel and spark cut way I like, even so that engine does stall

There are few ways to provide air at idle, some use throttle butterfly, some do have idle air valve for example. My fun car does have idle 'channel' for air, throttle plate will get shut completely, but it has no idle air valve, for cold weather it has aux air valve instead, pretty useless for that car actually as I use it only at summer and really don't need high idle at all.

It is quite amount of fuel what blip can use, it can use more fuel than WOT as there is acceleration enrichments on play too, but again don't know if LFS has such at all, I guess not as fuel is rather new thing still and such thing is not most important to simulate.
Quote from JTbo :No engines won't stall if fuel is cut at engine braking, most of FI cars do have it, some of carb cars have it, my fun car has programmable FI so I can set fuel and spark cut way I like, even so that engine does stall

There are few ways to provide air at idle, some use throttle butterfly, some do have idle air valve for example. My fun car does have idle 'channel' for air, throttle plate will get shut completely, but it has no idle air valve, for cold weather it has aux air valve instead, pretty useless for that car actually as I use it only at summer and really don't need high idle at all.


ah interesting, didn't know that, i would've thought having a fuel cut would be bad for the engine

Quote :It is quite amount of fuel what blip can use, it can use more fuel than WOT as there is acceleration enrichments on play too, but again don't know if LFS has such at all, I guess not as fuel is rather new thing still and such thing is not most important to simulate.

wouldn't that be down to the specific fuel map though? i think it'd be different in each individual situation
#55 - JTbo
Quote from danben7 :
wouldn't that be down to the specific fuel map though? i think it'd be different in each individual situation

There are different methods here, some FI ECUs do have separate fuel maps for acceleration some do use simple enrichment setting, say you open throttle at certain rpm and certain speed it adds fuel by certain % compared to what it would be in that rpm and throttle opening.

At higher rpm enrichment is typically less than lower rpm, but it can easily to be 5-10% in blip situations, of course it is rather short time and there does not add lot of fuel, but consider how often it is done and it can be bit more than commonly thought, specially carb cars are using really lot of fuel if you push pedal quickly.

Enrichment is there to make sure mixture won't get lean when throttle plate is opened quickly, that creates sudden addition of air into intake and before ECU can adjust to it it needs bit of time, also helps in acceleration as when you are running stoich mixture adding more fuel gives bit more power. Also reason why WOT is often good to be richer than stoich.
Now with carbs acceleration pump is really important as it takes bit more time to get fuel to mix properly with air from main jet(s).

Something like that, sorry for any typos and such

Oh yes, fuel cut can be bad thing on race engine as fuel does have some cooling factor, also spark cut is bad in cars with catalytic converters, says those who like to keep those parts intact (after few hundred track km with spark cut limiter there is small boost on performance as internals of cat are gone)
Quote from JTbo :Certainly engine has to be using fuel when idling, how else one could run out of fuel in first place? If LFS does not use fuel when idling then there is a bug.

If throttle is not touched there still is some throttle applied, via idle valve or some other way, fuel is also cut only if engine braking is strong enough, LFS should take these into account when calculating fuel consumption. For carbs it is different, but hopefully those can be forgotten from LFS

You'd think a BF1 idling for over 20 minutes at (indicated) 3800 rpm with a bit of throttle applied would use some petroil, wouldn't you? Wrong! See the attached screenshot for proof... Feel free to try it with any car you like, none of them will even drink a centilitre of petroil while idling...

So how does LfS calculate the fuel consumption? I think by multiplying the revs (over the idle-rpm value) with a given value (for each car)...

I thought this would be common knowledge... Guess I was wrong...
Attached images
idle.jpg
There is no decimal point in a ratio. How many more people are going to try to write a ratio that way?
#58 - JTbo
Quote from bbman :You'd think a BF1 idling for over 20 minutes at (indicated) 3800 rpm with a bit of throttle applied would use some petroil, wouldn't you? Wrong! See the attached screenshot for proof... Feel free to try it with any car you like, none of them will even drink a centilitre of petroil while idling...

So how does LfS calculate the fuel consumption? I think by multiplying the revs (over the idle-rpm value) with a given value (for each car)...

I thought this would be common knowledge... Guess I was wrong...

As I said earlier, if it is that way in LFS then it is a bug and need to be fixed.
rpm x throttle position = load based consumption modifier now there is time and base consumption needed to add to formula and we get how much car consumes fuel, if one does not touch the throttle is treated as 0% throttle then there is the error, there is no 0% in any engine at idle, there is always some of throttle, so changing that to be 0.53% for example would fix problem, also that would eliminate need to set idle rpm in program, that throttle setting would be needed to tuned so that rpm at idle would be correct.
I need 1.1% fuel to drive around the bl1 with the XRT while racing. If I drift a few corners I need 1.2%.

BTW why is the consumption measured in % and not litre or gallon? Is it because both imperial and metric understand %.

17 l/100km
5.7 km/l
42.53 L/100KM
5.53 Miles/Gallon

I'm getting 6.82mpg (US).
There needs to be a poll, so we can see the average (with equivilent imp/metric). Great thread, [runs to go calculate]
And how many options would you like in the poll? One for every tenth of a litre?

//edit: Just for your pleasure and the fun of others, I suggest making a compilation of as many numbers as possible and then run a frequency analysis on it to find the "most popular" value. If you want just the pure average, sum all the values and divide the result by the number of the values. Shoud be enough.
Quote from breadfan :And how many options would you like in the poll? One for every tenth of a litre?

//edit: Just for your pleasure and the fun of others, I suggest making a compilation of as many numbers as possible and then run a frequency analysis on it to find the "most popular" value. If you want just the pure average, sum all the values and divide the result by the number of the values. Shoud be enough.

I'm fairly certain that he knows how to average several numbers
wow... that was fairly uncalled for.

It wouldn't be that hard to make categories:
Under 3mpg (equivilent km/ltr)
3-4 mpg
4-5 mpg
5-6 mpg
Over 7 mpg


I'm averaging 5.53 Miles Per Gallon or 2.35 km/ltr
#66 - JTbo
But mpg is not edible, also can't figure any other practical use for it, L/100km should be in poll, not mpg

Now we have a problem then
Quote from JTbo :But mpg is not edible, also can't figure any other practical use for it, L/100km should be in poll, not mpg

Now we have a problem then

It isn't hard to have both
#68 - JTbo
Quote from JTbo :What about those from DK? They prefer km/L

We can put everything on 1 line i think

Quote from Renku :MPG: UK or US?

I use 1 G = 3.785 l so I guess i used the US one.

What's your fuel efficiency?
(71 posts, started )
FGED GREDG RDFGDR GSFDG