Fuel Cooler, Cooler Fuel?

[Immortality]

Does cooler fuel make more power?

I think the guys are correct, in a modern car with engine covers and metal fuel rails etc, fuel temperatures would most likely be higher than what they saw here in testing but does this also apply to fuel injection? And what about fuel economy when you aren't driving around giving it the jandle.

 

[Ginger Beer]

Plus there is the difference with dead head or return flow fuel rails, plus how hard your pumps are working, electric, or mechanical, and how much fuel is in your tank or fuel cell

I cannot see a issue with OEM setups, but when your running multiple high volume pumps to make "all" of horse powers the heat "may" cause issues

This is why getting your base fuel pressure at the injector is important, and critical with boost, as well as the fuel return valve

I'm sure a good tuner could explain it better than me

 

[Immortality]

I understand the different fuel systems, I actually really don't like the dead head design much like is used on LS motors.

From personal experience, the fuel rails on our L67 used to get cooking hot and that was without the engine cover fitted. I actually think manufacturers run em hot on purpose as I think hot fuel improves economy where as cool fuel improves power. I fitted heat sleeving and exhaust insulation wrap to our fuel rail system where it criss-crosses the blower. I do wonder though if doing this has potentially effected fuel economy.

However the reason I mention the difference between EFI and carburettor intakes is because of how/where the fuel is delivered. Carby's tend to make more peak power Vs EFI back to back when tested on the dyno, one reason for that seems to be where the fuel is delivered into the intake. With a carby the fuel is delivered at the start of the intake manifold, this exposes the fuel earlier to the air and gives it more time to interact which allows the fuel to cool the air as it goes through a phase change from liquid to vapour. Efi definitely wins the economy stakes and that seems to be because of the much finer droplet size which makes it easier to go through the phase change from liquid to vapour but it's effectively only happening at the (hot) intake valve/combustion chamber so you aren't quite getting the same intake charge cooling factor you see in a carburettor style system. A hotter fuel will take less heat before it goes through a phase change and fuel vapour is easier to ignite and burn which is important for economy.

I actually have some interesting thoughts about playing with IOT timing, it makes a difference for making power and so maybe it can also be played with for economy. All of this though will take more info and testing with the car on a dyno.

 

[Immortality]

I'd really like to try some of this stuff on a dyno.

 

[lmoengnr]

I'd really like to try some of this stuff on a dyno.

Make more room in the workshop!

 

[07GTS]

I actually have some interesting thoughts about playing with IOT timing, it makes a difference for making power and so maybe it can also be played with for economy. All of this though will take more info and testing with the car on a dyno.

if u dont have much overlap to get the full benefit of optimizing injection timing then u may only see small affects, usually good to make an adjustment and then just drive and take notice of your instant fuel usage before/after if that gets better then as it takes all variables into account then ur on the right track

 

[Skylarking]

Shouldn’t the question be what is the limiting factor in producing engine power given that fuel delivery into the combustion chamber and the air ingested through the throttle plate (considering the ECU aims to achieve low pollution levels in the closed loop control model our engines run under)? Is it the density of air (oxygen) or the density of petrol that is more important?

I thought we only deliver enough fuel into the combustion chamber to burn fully with the oxygen we have available from the air our NA engine actually suck in…

I‘d think (guess) the ECU could measure fuel rail temperature and adjust injector timing to also compensate for the changed fuel density but such just isn’t done. I haven’t seen a fuel rail temp sensor in any car I’ve owned and guess it isn’t done for a reason.

I‘d guess the reason that such fuel temp sensor don’t exist is because it wouldn’t really be beneficial because petrol engines are run under closed loop control where the amount of oxygen getting into the combustion chamber provides the overriding limitation to power production (which is why we see power fall and engines get sluggish as air temp gets above 30 and nearer 40C; o2 is reduced and timing is retarded as a result).

Unfortunately there isn’t much we could do in a practically sense to change air density in a NAT engine. So fuel density ends up being of little to zero concern since the ECU can‘t really compensate for less oxygen other than to squirt less fuel into the combustion chamber… the amount of o2 past the throttle plate is what it is…

Guess we could use an ac system to cool the air and thus could squirt in more fuel (regardless of the fuels temperature) but manufacturers won’t ever do that and for the most part vehicle owners wouldn’t see any benefit associated with the extra cost if the manufacturers did such…

Don’t know, maybe I’ve misunderstood the issue but for EFI EPA compliant cars, I don’t see the point of spending money in cooling fuel when cooling the intake air may will provide a bigger benefit

 

[Immortality]

All good questions. The above dyno test is really only relevant for max power with a carburettor setup running n/a. How it all plays out with EFI is a different question.

The above dyno results still leave me with a lot of questions. Ideally I'd like to have seen fuel flow and air flow to do a proper VE calculations.

OEM run engines hot because it seems to improve economy, however with a blower this is counter productive because heat is the enemy with boost trying to make power.

With the tuning software we have now on the V6 engines we actually have more scope for adjustment than OEM ever did.

 

[apollo13]

I don't buy this hypothesis at all. A drop of 8 degrees Celcius will increase the density of petrol by 1%. So it runs slightly rich for a given injector pulse. The exhaust sensors are going to trim that out after several minutes.