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Fuel warming for fuel economy
2

Fuel warming for fuel economy

Fuel warming for fuel economy

(OP)
The radiator that I am currently running is set up to also function as a tranny cooler.  Because I have a manual tranny I have no need for this function.  Would there be any fuel economy benefit to running the fuel through this core in the radiator?

The vehicle is a 1996 Dodge Neon
198K Miles

RE: Fuel warming for fuel economy

No, but it might increase the chance of a fuel leak and fire in an accident.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Fuel warming for fuel economy

I would be thinking of the following.
The fuel temp can get to about engine temp of between 190 and 210*f.  Will the injectors overheat in addition to there normal electrical operating temp elevation?
Will fuel expansion cause regulator problems?
What are the effects of elevated fuel tank temps?
Will the fuel pumps have shorter life under higher temps?
What benifit would there be to elevating fuel temp on combustion efficiency?
As the fuel is heated and sprayed into the air stream, the speed of combustion could be increased as though it were lower octane fuel and may cause ping from (now) to much ignition timing.
Usually in performance application the fuel is cooled to get density increases in the capacity of the air stream to take more fuel and cylinder packing for more power.
There are many inter-related relationships that go on so we go with a normalized world of operation. Intentionally change one thing and other things also change.

RE: Fuel warming for fuel economy

I would suggest that you do nothing to increase fuel temps.

You would probably find that your fuel economy will actually decrease. This will be due in part to the light ends of the gasoline evaporating in the rail and finding there way out of the injector nozzle, which will always be dribbling slightly. This evaporation will also cause vapour lock within the rail and hard hot restarting.

Depending on the type of fuel system you would probably notice fuel smells in the cabin. Likewise if your vehicle is fitted with a fuel tank purge system then the carbon canister will more likely be full most of the time, providing smells outside as well.

Point to note: Ping is not caused by rapid combustion, it is caused by autoignition. Rapid combustion will actually reduce detonation as the end gases are consumed before they can autoignite.

MS

RE: Fuel warming for fuel economy

The difference between the enthapies of formation

CODE

n-Octane vapour       C8H18(g)  -208450
n-Octane liquid       C8H18(l)  -249950
kilojoules per kilomole, is about 20%.

However, in a calculation of the heat released by burning it ...

CODE

CO2     8       Carbon dioxide  -393,520        3148160
H20     9       Water vapour    -241,820        2176380
C8H18  -1       n-Octane vapour -208,450        -208450
                                                5116090
... breaking up the fuel plays only about a 4% role in the energy produced by combustion; the main energy coming from carbon to carbon dioxide and hydrogen to water reactions, and that mainly as a result of multiplicity: the number of times the reaction occurs rather than the energy per reaction.

The end effect, 40 thousand in 5 million - less than 1% - is the most you could hope to gain.

I had a bottle of unlaballed sparkling wine from the cellar at lunch so apoligies if this isn't quite right.

RE: Fuel warming for fuel economy

Having done most of the calculation, I guess I could just add that dividing by an atomic weight of 8*12 (carbon) + 18*1 (hydrogen) = 114 gives 44,877,982 megajoules per kilogram for n-octane vapour, based on the above figures.

RE: Fuel warming for fuel economy

Hi Blob
I've actually done this before. I noticed 3 things:
1. There was an improvement in fuel economy. Noticeable but not much.
2. The vehicle had better acceleration from a standstill.
3. The engine pinged quite a bit and the timing had to be retarded.
The engine ran well when cruising but would vapor-lock in city traffic and when idling - not very reliable. Also, if one was in an accident and the insurance company inspected the vehicle, they would probably void their coverage - whether the modification was relevant or not. Combine these things with the already mentioned fire hazard and I was paranoid to drive the thing.
However I believe there is something to the idea. I think there is an optimum fuel temperature for each application. One would probably need a computer to monitor and control it. In some climates, the underhood temperature would be over that optimum anyways. It might be worth pursuing, but not by your average mechanic or tinkerer.

RE: Fuel warming for fuel economy


Drag and land-speed cars have been cooling their fuel for over 40 years years for more power. Here's a "Cool-Can" from Moroso, that uses regular or dry ice.

RE: Fuel warming for fuel economy

Which has what, exactly, to do with fuel economy?

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Fuel warming for fuel economy

I guess if you use a litre of hot fuel to get a certain distance, a litre of cold fuel might take you further as it weighs more and therefore contains more energy per litre, but maybe the car will be slower as it will be a gram or two heavier winky smile

If combustion efficiency were a real issue, there might be some point to this, but as most losses are due to heat escaping into the cooling system and out the exhaust, I don't see much potential for gain by focusing on the already quite efficient area.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Fuel warming for fuel economy


Cooled fuel makes for better atomization, not more fuel in the lines.

Hot fuel is not good and will also cause the fuel pump to die young. Do you really think Blob is inventing something here?

RE: Fuel warming for fuel economy

Thermodynamically there is no doubt in my mind that for ultimate fuel economy (ignoring practicalities) hot fuel would be more efficient. But we can't ignore practicalities, we are engineers, not scientists.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Fuel warming for fuel economy

How will cooled fuel make for better atomization? I think that in a gasoline engine the cooler the fuel, the larger the droplets, the poorer the combustion?!? Infact I think that with cooled fuel there is a real risk of puddling, quench, borewash and tipin stumble/hesitation.

Also, in a PFI engine anything that causes wall hangup to increase can result in part load misfire. This is us calibration engineers spend so much time in cold climates using hot climate fuels (think RFG2/CARB Phase2 in Alaska). The driveabilty of vehicles in these situations is horrendous.

MS

RE: Fuel warming for fuel economy


That it works could hardly be more proven.

As to how it works, I have always heard that it is by air/fuel temperature differential.


RE: Fuel warming for fuel economy

My experiments show that the best atomisation is at it's boiling point. Hardly cold.

The higher the kinetic energy in a molecule, the more they will separate from each other. Kinetic energy in a molecule is directly related to temperature, higher relating to hotter.

When you consider the temperature, mass and specific heat of air vs the mass specific heat and temperature of the fuel consumed by an engine, the temperature of the fuel is insignificant.

The very first thing to leak fluid in a car involved in an accident is the radiator in almost all cases. Putting hot petrol there will in my opinion, substantially increase the risk of fire, for an insignificant improvement in atomisation.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Fuel warming for fuel economy

Blob97,

In order for fuel to combust it must be in a gaseous state. If you have every conducted a flammability test you will immediately realize this.

The Holy Grail for any Internal Combustion Engine would be to convert all of the fuel to syngas prior to combustion without forming tar, gums, etc.

You cannot do this with a small spark or compression-ignition engine.

Any and all marine engineers are well aware of preheating fuel prior to injection or combustion in boilers, diesels or gas turbine engines.

The purpose is twofold:
(1) Remove water
(2) Prevent wax formation in injectors or nozzles

Preheating fuel has many advantages, but must be done safely.

Reducing droplet size increases surface area, thus more fuel can vaporize in a shorter period of time.  It is the gaseous vapor layer that surrounds the fuel droplet that burns away.  Not the droplet of fuel.





Todd
www.oxilume.com

RE: Fuel warming for fuel economy

The post by Fabrico illustrated a fuel cooling can. Cooling the fuel cools the overall intake system. This helps cool the incoming air. Cooler air is denser air. Denser air has more O2. More O2 allows more fuel to maintain the proper air/fuel ratio (stoichiometric). More air plus more fuel = more horsepower. Another example of this is the intercooler on a turbo-charger. It's only function is to cool the intake charge to allow more air and fuel into a given cylinder. I'm not sure if routing your fuel through a radiator transmission cooler will actually cool the fuel, but the concept of cooler fuel is sound.

RE: Fuel warming for fuel economy

oxilume, I am not disputing your post, however, heated gasoline causes vapor lock, among other problems. Atomization is certainly important, but the intake manifold configuration and combustion chamber design have more effect on this than the temp of gasoline. The original question was about fuel economy, and he referenced running the fuel through a cooler. In the real world, cooling the fuel can increase the fuel economy, given proper tuning.

RE: Fuel warming for fuel economy


I wasn't going to bring this up because it is entirely different than Blob's idea. It is however related to the topic. This has been around for a long time and has been to high places and back down. If Smokey says it's so, it probably is.

http://schou.dk/hvce/



RE: Fuel warming for fuel economy


It's a strange picture format, if it does'nt load, hit the "Refresh" button.

BTW, there are numerous mentions of this system on the internet.

RE: Fuel warming for fuel economy

That diagram is a good example of trying to overcome the shortcomings of a draw through carby turbo instalation.

By heating the air fuel mixture it will reduce fuel puddling and promote vapourisation. These can be big probs with old school technology as shown.

Ken

RE: Fuel warming for fuel economy

PFI gasoline engines inject onto a closed valve - almost never on an open valve (except at high load/high speed). To do otherwise greatly increases HC emissions.

Cooling the fuel: While it is tempting to imagine that this might decrease the intake systems temperature it will only be by a miniscule amount - consider the amount of air that is in that system!

Any gain that is made will be outweighed by the fact that your droplet size will be much greater and a larger proportion of your fuel simply *does not burn*. It just sails out of the exhaust port as HC emissions.

Also all of these last droplets of fuel splashing about will mean that there is plenty of oppurtunity for wetting the spark plug - hardly the stuff that fuel economy & power gains comes from!

Might I also mention that driveability is going to be badly affected - as said before the situation sort of replicates having a very low RVP fuel.

MS

RE: Fuel warming for fuel economy

What has fuel temperature got to do with particle or droplet size?

They are both independent factors that each has an effect on vaporisation rates.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Fuel warming for fuel economy

I think the key here is that we are talking about a PFI engine here, not DI.

The mixture preparation that is occuring on the back of the intake valve consists of the gasoline components changing from a liquid to vapour state - with the lightest end of the fuel vaporising first.

As soon as the valve opens the jet action that occurs between seat & valve causes a certain 'spray pattern' of fuel droplets to enter the chamber with the vapourised charge.

For a start with a lower temp there is going to be more fuel that is still in the liquid state (the heavier ends).

As this fuel enters the chamber the evaporation of the smaller droplets will occur as they pass from liquid to vapour, however since the fuel started at a lower initial temp there will be more energy required (time) to evaporate the remaining droplets.

Since there are more droplets about for longer there will be more coalescence & impingement and therefore more HC emissions.

MS

RE: Fuel warming for fuel economy

OK, I can see your point.

Is it supposition or do you have data.

I can also see the possibility that depending on valve and injector timing, that as the inlet valve opens some time before TDC, the air flow as the valve cracks off the seat at low RPM might be very slow and do little to disperse and atomise the fuel.

As in a modern engine, virtually all fuel is burnt during the power stroke, I still do not see any meaningfull gains in fuel economy, especially as the Engine Managment System will be calibrated or mapped for metering fuel at normal temperature.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Fuel warming for fuel economy


That cool fuel cool works by cooling intake air could be a big supposition.

The diagram above is of something far more than a turbo setup. "No, not a turbo! It's a homogenizer!"

RE: Fuel warming for fuel economy

I do not hold data like that personally but companies I have worked before do.

Although as you know nothing in this world is for sure so the mechanism I described mightn't be whats happening - no way of telling for absolute sure.

As for heating or cooling the fuel, I must agree with Pat here - leave it alone!

MS



RE: Fuel warming for fuel economy

This is a "AGED" problem.  Everyone has heard of the "vapor carb" problem with this is well (enviromental law) Today's fuel versus the day of "vapor carb" has to be heated to a higher point to become a vapor and how that is done is what is part of the state to state laws that create "boutique fuels".

Living out in the Oil fields we can still get our hands on "drip gas" which is gasoline before the government gets a hold of it.  The good ol' stuff that leaves vapors on the ground on a mildly warm day.  The octane of gas is not as such to make vaporization delivery a safe reality without major modifications to laws. You have to keep in mind that the lawyer in the congress will engineer the engine before you do and blame someone else for static movement forward in technology.

Look at LPG 40% cheaper to start. Has huge tax breaks for using it.

AS FOR THE COOL FUEL. its for stability not performance an engine that misses on a car 4 ft wide at high speed the shimmy would kill the guy. Its to help prevent predetentation and prevent fuel temp from changing during the run. Mattsmooty gave great explanation on why it would pollute more but not even on topic.

http://www.prnewsnow.com

RE: Fuel warming for fuel economy


GunMuse, respectfully, you need to watch those vapors. It's not likely that anyone could post something more incorrect.



RE: Fuel warming for fuel economy

No serious like,

Its the government that's making all this fuel that is so hard to vapourize...

MS

RE: Fuel warming for fuel economy

mattsooty and Fabrico

I have been around these fora for quite a few years now.

I have noticed that when aggressive or non respectful arguments, rather than rational debate evolve, people and threads disappear.

When someone looking for an argument for whatever reason starts baiting with stupid comments, they, along with those who took the bait and the thread all go together.

Best first step is to respectfully post a correction, then ignore any attempts to wind you up.

Anyone who belongs here will quickly see which argument is valid and which is ranting raving bunkum.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Fuel warming for fuel economy

Quote:

Anyone who belongs here will quickly see which argument is valid and which is ranting raving bunkum.
I've been thinking that but until now was not convinced of it.smile
Thank you Pat
Apologies GunMuse.

 

RE: Fuel warming for fuel economy

Yes, good point Pat - an error of judgement on my part....

Apologies GunMuse.

MS

RE: Fuel warming for fuel economy

Having been a drivability tech for some 20 odd years, I tend to agree that although heating the fuel will make it vaporize faster, fuel is a chemical which makes the oxygen in air burn, and thats where the power comes from. If you cool the intake air it becomes denser and will let you get more into the cylinder- so if your crafty enough to have heated fuel introduced directly into the cylinder AFTER the intake valve closes you may see some efficiency gains from the combustion process. Otherwise your just reheating the cooler air, which will negate the gains your seeking.

just my 2 cents worth.

RE: Fuel warming for fuel economy

oops, I have to add to my previous post:

You can't inject gasoline directly into the cylinder because gasoline will detonate in the fuel rails under the pressure needed to get it into the cylinder.
I'd imagine sequential port injection with warmer fuel might work, but warmer fuel won't work in anything else because as stated earlier it'll only rewarm the cooler air- which will reduce the air density.

Fuel injected directly into the cylinder is called a diesel engine.

RE: Fuel warming for fuel economy

LordMalak

"Fuel injected directly into the cylinder is called a diesel engine"

.....not a Gasoline Direct Injection engine then?

"You can't inject gasoline directly into the cylinder because gasoline will detonate in the fuel rails under the pressure needed to get it into the cylinder"

Soooooo what about the Mitusbishi GDI engines, VW FSI engines etc....?

"Having been a drivability tech for some 20 odd years"

Really???


MS

RE: Fuel warming for fuel economy

How does the oxygen get into the fuel rail to give the fuel something to react with?

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Fuel warming for fuel economy

ok, ok, I've been out of it for a couple of years. But I was taught that gasoline will detonate under extreme pressures, not the 100 or so psi its under now, but thousands psi used in diesels. Sorry I haven't kept up on current tech as I retired an am quite happy with my carburated 25 year old oldsmobile. An I haven't worked on a bishi in 10 years and VW's we're scarce as we specialized in Benz and BMW's.

I'll dig out my calculator as it occurs to me that at a 12:1 compression ratio you'll only need a few hundred psi to inject directly into a cylinder (gasoline), and as I'm not a chemist I can only guess at the stability of gasoline under those pressures. If mitsubishi and VW can do it I guess it's reletavily safe, but I've never laid eyes on either system.

again, sorry. It was only my opinion based on years of consumer vehicle service, not special vehicle development.

;)

RE: Fuel warming for fuel economy

During the latter years fo the Formula 1 turbo era, when the rules introduced fuel quantity restrictions, Honda started to heat the fuel to achieve better BSFC.  It was one of their main advantages.

RE: Fuel warming for fuel economy

yamaha di 700psi, mitsu thousands of psi, gdi pressures over 10000 in the works.  Fact is, heating fuel is not good for durability, aggravates deposit formation.

RE: Fuel warming for fuel economy

LordMalak - Actually diesels have a cylinder pressure of typically 600 psi just before combustion initiates

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Fuel warming for fuel economy

When I was in college, I had a '72 Chevy that had a 307" motor w/a two barrel carb.  I made an aluminum block that went between the carb and intake manifold, and this block was drilled to circulate coolant in series w/the heater core.  I also drilled a passage for gas to go through between the pump and carb.  It gave me 2 mpg increase in the winter.  I believe it effectively leaned the mixture a bit to do this.  Nowadays, with O2 sensors keeping the mixture stoich, it would probably have no effect on mileage, but hurt summer drivability.

RE: Fuel warming for fuel economy

I think heated manifolds have been around for about 100 years. Exhaust heat is actually quicker for reducing enrichment required for cold starts in cold climate.

The impact of also warming fuel will be minimal as there is nearly 15 times as much air as there is fuel.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

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