can someone check my maths? (mpg to lpm)

[jimmyhackers]

im trying to figure out a rough litre per minute figure of fuel used for my petrol car (boo)

if i get 30-35mpg at a steady 50-60mph......what rate of fuel am i using in litres per minute?

if i go with 30mpg and 50mph.... i will use 1.66 gallons of fuel in an hour. thats 6.3 litres per hour... or 0.105 lpm?

35mpg and 60mph... i will us 1.714 gallons of fuel in an hour. thats 6.5litres per hour..or 0.108 lpm ?

if i lead footed i can go as low as 20mpg.....

im making a peltier fuel cooler.....and would like to know what kind of fuel flow rates im expecting so i can bench test appropriately.

TIA
jim

 

[fechter]

Your math looks right.

What does cooling the fuel do?

 

[DanGT86]

Many fuel injection cars use a return style regulator sending most of the unused fuel back to the tank.

I obviously don't know the particulars of your system but it might be a factor to keep in mind when designing something.

 

[jimmyhackers]

thanks for replies

ive never seen a gasoline preheater in the UK...maybe in colder climates
ive seen preheaters on diesels in colder climates mind.

i have seen fuel coolers though. either in rad form or the drag race tubs with dry ice in.
however, there are no sub-ambient active systems that dont require replenishing

my cars fuel system is a return style to a swirl pot in the tank.

the theory is....the fuel pump pressure/power aswell as engine bay temps will raise fuel tempreture. unused (hotter) fuel is sent back to the tank.
over time this can increase overall fuel temps and increase evaporative emmisions and knock potential....

petrol can still vaporize as low as -43 c, im not going anywhere near there.
i imagine its interaction with the piston head and cylinder walls during the compression stroke will atomise it further, and as they will be at a greater temp delta with cooled fuel...this reaction will be increased?

i can also turn it off if starting issues arrise.

my main thought is (commercially), past my own uses, is as an octane "booster".
Colder fuel and therefore a colder intake charge means less likelyhood of pre-detonation. depending on how much i can boost apparent octane decides what more expensive high octane fuel you can replace with cheap fuel and those money savings over time.

i.e. the material parts cost of my current testing unit is about £50, in the uk we can get 95 to 99 octance, with the price being about 12-15p differnet per litre. thats over a fiver saved every 50 litre tank...so itd pay for itself in 10 tanks.

on my test rig the pump runs at about 4lpm and im getting a 1ish deg C drop between inlet and outlet liquid temps for about 25watts of electrical power. with a max low temp of about 7-8 degrees liquid vs 17deg amibient air if i let the system run for a few minutes.

although my car may use about 0.1lpm, due to the fuel pressure regulator being located on the fuel distribution rail in my car. i can only mount my cooling device before it.... meaning a lot of the cooled fuel will be sent back to the tank...so my lpm figure that goes through my fuel cooler will be a lot higher than 0.1lmp.

annoyingly i cant find documentation specifically on varying fuel temp vs octane rating....just a generalised statement that hotter fuel increases knock chance and vice versa.