gas milage

[King of the Americas]

To scotth:

Regarding my initial post, what %'s in potential increases would to attach to the varibles I offered?

Having made novice efforts as a young driver in this "dead coasting for distance" effort, I think that a practiced driver could save quite a bit if he knew the course well enough to use hills and the like.

Indeed Psiload is right, this IS all about a bet. 10-1 odds AGAINST me being able to increase the factory recommendations by 10-20 MPG. I think it is possible to make increases of 10 EASY...

20 if you did a lot of work, but moreover, that you are really only limited by how much you can put into the project.

I think his money is mine.

 

[scotth]

Re: To scotth:

Regarding my initial post, what %'s in potential increases would to attach to the varibles I offered?

Having made novice efforts as a young driver in this "dead coasting for distance" effort, I think that a practiced driver could save quite a bit if he knew the course well enough to use hills and the like.

Indeed Psiload is right, this IS all about a bet. 10-1 odds AGAINST me being able to increase the factory recommendations by 10-20 MPG. I think it is possible to make increases of 10 EASY...

20 if you did a lot of work, but moreover, that you are really only limited by how much you can put into the project.

I think his money is mine.

I think his money is yours as well.

magnetic fuel savor - worthless

underdrive pulley - small but measurable, probably not worth the time

port/polish exhaust - small, so small as to probably defy measuring.

removing spoilers - small but measureable, cheap/free so worth doing

closing up dead spots - small but measureable, near free (duct tape will do), worth doing. Duct tape the gaps in the hood, the door handles, the gaps around the head lights, etc.

high octane fuel - could help or hurt. As noted below, high octane fuel has a very slightly lower energy content, however, if the car has a modern ignition that will take advantage of the increased octane by advancing the time (or if you manually advance the time) it will be a net gain.

cold climate - bad idea. Yep, you make more power, but you drawl more fuel with it... still no problem, until you factor in the increase wind resistance... High altitude, high temp is best for gas milage.

increase tire pressure - small but measurable gain. free so worth doing.

All that together might get you as much as 5%.

Where you are really gonna do it is with driving style. I haven't noticed you mentioning what type of transmission the car has, maybe I missed it. Hopefully a manual?

Driving style will easily get you over 40 in my opinion, even with no mods to the car. 50mpg would not surprise me much. Wide open from 30 to 50mph in top gear. Then to neutral, and engine off coast back to 30. Repeat.

 

[Psi Baba]

By the way, the habit of selecting neutral when going downhill used to be referred to as "Mexican Overdrive" in less politically correct times.

And in even less politically correct times, it was referred to as Jewish Overdrive (I wouldn't be surprise if it was also called Scotch Overdrive in some parts, and I think I've also heard it referred to as Polish Overdrive). And, as the The Don hinted at, it usually involved not only putting the car (standard trans) in neutral, but turning the engine off, then coasting down the hill. Of course, in the days when people actually did this, there were no power brakes or power steering, so whether the car was running or not had no effect on those things.

 

[King of the Americas]

To scotth:

Actually, it 'has' to be an automatic, given MY disabilities, so I am a little in the hole there, but I VERY much appreciate your knowledge and insight provided herein.

I really liked the duct tape thing, never thought about it, and it would be rather cheap...and probably 'worth doing'.

More Precisely:

magnetic fuel savor - my cousin SWEARS by them, and offered me one of his to 'try' for Free, so I thought what could it hurt.

underdrive pulley - I found a set in a performance catalog, and thought they were 'pretty', so I bought them. My car is black and I am doing all the 'upgrades' in red.

port/polish exhaust - As with the underdrive pulley system, I saw this intake and matching exhaust system that I had to have.

removing spoilers - This WILL be done, along with a 'customzied' paint job and reformed front end. I am gonna "shape it like a bullet with a jet intake."

closing up dead spots - Duct tape...AWESOME.

high octane fuel - The ignition IS computer controlled.

cold climate - Summer heat, done.

increase tire pressure - Thought so.

5%...???

I was thinking closer 8-10%

But thanks Man, you've really been helpful!

 

[scotth]

The automatic hurts you 3 times.

1) Can't bump start at the end of a coast cycle (but probably not a big problem really)
2) You'll be converting quite a bit of usable power into heat in the torque converter at WOT.
3) Will be difficult if not impossible to keep it in high gear during an accel cycle

Sorry that your cousin is deluded, but you're right, it can't actually hurt your effort.

The 5% is just a guess, no calculations done. But, I have played this game before, and we didn't get all that much out of the "little" tweaks. The driving style changes made a dramatic difference though.

 

[Iconoclast]

And race cars generally drive at very high speeds, meaning that they must push alot of air. Remember that air resistance increases by the square of the velocity. Twice the speed requires 4 times the horsepower to do it.

Nope, doubling your speed requires 8 times as much power, not 4 times as much. You're quite correct that drag increases with the square of the velocity, but that's a force not power. You have to multiply again by speed to get the power. This explains why Formula 1 teams all have their own wind tunnels. If an increase in top speed is the goal, a 1% improvement in drag is equivalent to an 8% improvement in peak engine power. Of course engine improvements aren't all about more power, improving the low end torque is what improves acceleration.

Now, if you took a NASCAR for example, removed the spoilers, put narrow tires on it, and drove in the 30 - 50 mph range using the wide open or coasting in neutral driving style, it would get very impressive gas milage.

This is simply untrue. Racing engines are designed to operate over a small RPM range (say 7000 to 9000RPM, I have no idea what rev limit is mandated by NASCAR). Having a narrow operating band means the engineers can use cams with radical profiles that produce massive amounts of torque in this rev range and very little below it. For any given engine, cam modifications can be made which will increase the maximum power, but a side effect of this is that the torque curve will necessarily move to the right on the RPM scale. The upshot of all this is that increasing peak power will reduce the torque available at low and medium engine speeds resulting in a vehicle that is fairly undriveable at low speeds. Added to this is the huge cam angles and valve overlap which will send most of the intake charge straight out the exhaust runners during low speed operation. There's more problems as well, the extremely weak vacuum signal that is transmitted to the carburetor venturis at low RPM (NASCAR engines typically use a single plane open plenum inlet manifold design) means fuel metering at these engine speeds is poorly controlled.

 

[Iconoclast]

Re: To Iconoclast :

Now wait a minute there, mate!

I believe I said I worked on 'used cars' as a youth. I never claimed to be able to make thoses increases in a new stock engine...

An old engine with fouled plugs, clogged intake, and crudded up inards, clean it out and replace all seals and port and polish everything as to see yourself in it, will infact make 'big differences' in horsepower. 'I' have personally achieved as much as a 33% increase in engine performance with application of 'better' exhaust systems.

No, that's not what you said King. Let's go to the videotape and replay exactly what you wrote:

"My experience has mainly been with V-8's, and we say up to a 33% increase in horsepower by modifying intake and exhaust systems"

Changing the intake manifold and the exhaust might give you 5% or perhaps 10% increase in peak torque. To get your magical 33% you need to modify the compression, probably the head design, increase the compression...

 

[Iconoclast]

And in even less politically correct times, it was referred to as Jewish Overdrive (I wouldn't be surprise if it was also called Scotch Overdrive in some parts, and I think I've also heard it referred to as Polish Overdrive). And, as the The Don hinted at, it usually involved not only putting the car (standard trans) in neutral, but turning the engine off, then coasting down the hill. Of course, in the days when people actually did this, there were no power brakes or power steering, so whether the car was running or not had no effect on those things.

And I hope there were no steering wheel locks fitted to the columns. There's been a few cases of people switching the engine off while rolling along, turning the wheel to go around a bend, and having the steering wheel lock engage.

 

[scotth]

Nope, doubling your speed requires 8 times as much power, not 4 times as much. You're quite correct that drag increases with the square of the velocity, but that's a force not power. You have to multiply again by speed to get the power. This explains why Formula 1 teams all have their own wind tunnels. If an increase in top speed is the goal, a 1% improvement in drag is equivalent to an 8% improvement in peak engine power. Of course engine improvements aren't all about more power, improving the low end torque is what improves acceleration.

Oops, you are quite right here... my mistake

This is simply untrue. Racing engines are designed to operate over a small RPM range (say 7000 to 9000RPM, I have no idea what rev limit is mandated by NASCAR). Having a narrow operating band means the engineers can use cams with radical profiles that produce massive amounts of torque in this rev range and very little below it. For any given engine, cam modifications can be made which will increase the maximum power, but a side effect of this is that the torque curve will necessarily move to the right on the RPM scale. The upshot of all this is that increasing peak power will reduce the torque available at low and medium engine speeds resulting in a vehicle that is fairly undriveable at low speeds. Added to this is the huge cam angles and valve overlap which will send most of the intake charge straight out the exhaust runners during low speed operation. There's more problems as well, the extremely weak vacuum signal that is transmitted to the carburetor venturis at low RPM (NASCAR engines typically use a single plane open plenum inlet manifold design) means fuel metering at these engine speeds is poorly controlled.

I considered mentioning that it would be a good idea to change the cam profile (especially to limit lobe overlap), but left it out for simplicity.

However, the cars do carburate quite cleanly at relatively low rpm suprsingly enough. (I've driven one) Disabling the manual secondaries should be more than sufficient to take of the problem you mentioned or just use less than WOT.

When I entered the track in one, I short shifted up to top gear and was probably only doing 50 when I reached top (4th) gear. The car pulled cleanly and with real authority even from that low rpm. It was very impressive.

3rd gear could also be used for the test as they are geared pretty tall.

The engines certainly have a much broader torque curve than I would have guessed before I drove one.

 

[Iconoclast]

However, the cars do carburate quite cleanly at relatively low rpm suprsingly enough. (I've driven one) Disabling the manual secondaries should be more than sufficient to take of the problem you mentioned or just use less than WOT.

Damn, that's pretty cool, I'd love to have a drive of a NASCAR. Apparently there's a place in Sydney or Melbourne you can take them out on the track under supervision by an instructor, but I live too far away at the moment. Yes, Australia used to have a NASCAR series for a while, but it sort of fizzled out and I don't think they run any more.

 

[scotth]

Damn, that's pretty cool, I'd love to have a drive of a NASCAR. Apparently there's a place in Sydney or Melbourne you can take them out on the track under supervision by an instructor, but I live too far away at the moment. Yes, Australia used to have a NASCAR series for a while, but it sort of fizzled out and I don't think they run any more.

To be completely accurate, the car I drove was a retired BUSH series car. None the less, I was quite impressed.

The biggest surprise was how comfortable the suspension was. The track felt pretty rough while being shown the line to drive in a big van, and I was expecting to get pretty well pounded in the race car. Quite the opposite, the ripples and imperfections where nearly unnoticable in the race car. Far smoother than a passenger van.

 

[Iconoclast]

The biggest surprise was how comfortable the suspension was. The track felt pretty rough while being shown the line to drive in a big van, and I was expecting to get pretty well pounded in the race car. Quite the opposite, the ripples and imperfections where nearly unnoticable in the race car. Far smoother than a passenger van.

That's surprising. From watching onboard camera shots I had the impression that there was some pretty severe vibration at high speed.

 

[King of the Americas]

To Iconoclast

NOW, that would all depend on the previous condition of said motor, wouldn't it...?

I mean, a completely clogged intake, competely freed of henderence would make a larger difference than 5%

Indeed, I did not reference as to HOW used these engines were...

Wouldn't you say that one must qualify possible increases by previous condition?