MPG-topic

[Lasse]

We don't yet have MPG-forum or topic. Ok, we have that 34:1 topic, but that is not the same thing, so I assume anybody don't resent if I start one. I'd like to hear what you others will make for engine to improve MPG.

I have one idea. I'd like to hear what you think.

When we are driving at low constant speed, we don't need very much horsepower, but our engines are making maybe 5 or 40 times more horsepower @ WOT.
That is situation where your engine is extremely too powerful at low speeds. So when you drive low speed, you have to somehow limit power or car is accelerating. What we do is we lift right leg from gas pedal and close throttle. And what happens? Volumetric efficiency drops very low and car goes constant speed. In side effect compression pressure drops very low. That can't be good for fuel economy, right? Next question is how much fuel car will consume if it have so small engine it just gives enough horsepower @ WOT to drive constant speed at let's say 50 mph? I think it is much efficient, because of good compression pressure.
Next you think I will suggest to put two engines in car. That is one solution, but not very practical. What I suggest we make conditions for big engine allmost same that in small engine. Ok, lean burn engine is doing that, but there is limitation in mixture leaness. Conventionally we try to atomize fuel to small particles and we put it in chamber and pray it will mix homogenous with air and burn efficiently in very low combustion pressure. My idea is what if we vaporize fuel and mix it air before even it is entering to intake manifold. Vaporized fuel will take very much volume of air, so you don't have to put so much fuel in mixture, because mass of air entering in the engine is low. So you don't have to lean mixture to it's limits for getting good combustion pressure.

Another idea is to heat air so hot it expands much and therefore you don't have to put so much fuel in it to satisfy engines AFR limit. I don't know if it is good to combustion at high compression pressure, but that might be tradeoff.

Maybe fuel can also be for example propane so it vaporized very easily and takes volume of air.

I repeat, my english is not best possible, I hope you understood my idea. And I am very unexperienced hobbyist, so I really like to hear your opinions for my theories.

[rookie]

As for an economy section, I don’t know if GFN is going to do a separate section but I do know David and Dusty have been working to put together some tech articles that focus on this very subject and they may do it along the lines of the porting school theme.

I don’t have a lot of knowledge around fuel its self so I hope others will elaborate on fuel as a vapor, but my understanding is you can only vaporize it so much before the effects hurt instead of help.

It seems to me that the fuel manufactures should be looking at their fuel blend, to get more miles per gallon from a fuel standpoint.

On my carbureted cars I reduce the idle feed circuit to reduce the amount of fuel it uses at idle and part throttle, this, along with advancing the timing curve as much as possible (all trial and error per engine) helps with fuel consumption.

The duel engine thought is what brought about the hybrids.

Some people over the years have tried a duel intake system, one small for low speed and one large for upper rpm; most have failed but seems like the most cost effective if someone could get it right.

I would like to see more here about gear and overdrive transmissions effects on economy as well.

[Lasse]

Originally Posted by rookie

I would like to see more here about gear and overdrive transmissions effects on economy as well.

I think gear ratio have great role in fuel economy, because it's making just same thing = Improving cylinder pressure. If you put your vehicle in higher gear, what you are actually doing, you lower engine rpm and you increase compression pressure, because you have to push more gas pedal to get satisfying torque from engine. But engine have it's limits for low rpm operation, especially if it is made for high rpm performance.

[Lasse]

Originally Posted by rookie

I don’t have a lot of knowledge around fuel its self so I hope others will elaborate on fuel as a vapor, but my understanding is you can only vaporize it so much before the effects hurt instead of help.

Do you speak full horsepower potential of engine or maybe about 15 horsepower (or something about that) what we want at 50 mph?

[nitro2]

Well to have any hope getting really good fuel economy on a V-8 a number of things would have to change and one of them would be operating the engine at very low rpm under at least a moderate load. A big cylinder at very low rpm is going to be a problem child from the standpoint of detonation, but ignoring that and A/F mixture preparation and gearing for now, what would be a practical limit to how low (rpm) you can go on a decent V-8 before there are issues to address - mechanical, lubrication, etc. etc. Very low rpm is not something we have ever looked at, so I'm throwing it out there in the hope that someone may have something to offer. Obviously tractor engines and the like can run at very low rpm under load but thats not what is needed if we are going to have our cake and eat it to.

[Cammer]

V8 engine designs are difficult to engineer for exceptional fuel mileage.

Older, V8 powered street vehicles may become dinosaurs!

4 cylinder turbocharged engine designs show great promise.

Smaller, lighter vehicles will be the order of the day.

Racing will see many changes in the near future!

Oil is the great dictator!

We must find new energy sources or remain slaves to oil!

I personally do not want GFN to become dominated by MPG topics.

Efficiency is as important to a race engine as to a street vehicle.

My research has uncovered deficiencies with race engines which very few address. I am sure members such as nitro2 see many areas of possible improvement on a daily basis.

Crack open your college engineering texts because the future will demand more than a basic understanding of the ICE!

[seattle smitty]

[quote=Cammer]

I personally do not want GFN to become dominated by MPG topics.


That's part of why several of us wanted a separate forum. As compared to some other fuel economy sites I've seen, the better-informed folk are here . . . and we need you to call B.S. on some of the zanier ideas we'll offer up, Cammer.

[rookie]

Originally Posted by Cammer

My research has uncovered deficiencies with race engines which very few address.

Cammer,
I think it was you that once said, be prepared to post data and back up what you post here.

We are all ears

[BlackCat13]

We will ALWAYS be slaves to OIL.

More than motor fuels come from oil.
We live in an oil dominated world.

Plastics
Fertilizers
Medicines
and hundreds of other things come from OIL.

Only so much plastic can be made from a barrel of oil.
The rest is motor fuels, LP gas, etc.
The world will still demand oil products.

All we can do is reduce our dependence on gasoline,
although I personally believe that oil is abundant,
far more than we realize,
and all we have to do is go get it.

Finally after 30 years of green freaks preventing drilling,
a new onset of drilling is being allowed off our coasts.
Now if the liberals will just allow new refineries to be built.

Unfortunately it will take 6-8 years for the pendulum to swing.

Smog? mmmmmm.

[nitro2]

Some of the new cars with V-8s get relatively good gas mileage considering they are still heavy. I'm still waiting for someone to build a lightweight, decent handling V-8 rear wheel drive car that doesn't cost a fortune, but I guess that will never happen. By lightweight I mean 2500 lbs. max.

A V-8 will never match a turbo 4 cylinder for fuel economy, but there are ways that could get a V-8 into a situation where economy was pretty good, good enough to keep it off the dinosaur list.