How bad do you want to get better mileage???

[Sveivo]

Ah, but can you please explain WHY it is not good practice?
I am failing to see, mechanically, what will cause a problem.

Now please keep in mind also what I'm referring to is NOT popping it in and holding it just to coast (so you are using the pedal/clutch more often), but rather simply holding it in longeri n cases where you need to shift anyway.
E.g., coming downhill, stop ahead. You will have to downshift anyway, just pop it in early and coast up to the stop. Ot, holding it in longer between gears.

Actually, there is a reason that it is not good. When the clutch pedal is in, the mechanism that separates the clutch and flywheel is loaded, and, therefore isn't in its natural state. Basically it puts stress on things.

I don't know the ins and outs of it, but if you do some googling, perhaps you could find something.

I remember reading that if you hold it in too much, the mechanism wears out more quickly. It might even be in the owner's manual.

But in reality, unless you really have the clutch in all the time, I do not think you would really harm anything. These parts would probably last a long time anyway. It's just for the sake of rigor that I wanted to make the distinction.

Peace.

Simple way to lower RPMs...and increased gas mileage
Slap on some 185/75R16s on your car. Will drop highway RPM about 400-450 RPM.
Yes your speedo will be off.
Yes your car will be even more of a dog off the line.

Very insightful first post

 

[Magus]

You can always increase your mpg if you driving habits are good and you are stock.

CAI, UDP, Header, midpipe w/ highflow cat, lightweight wheels, narrow tires, higher than oem psi in tires (32psi), no roof rack, oem sized front drill slotted rotors, and keep your car waxed.


If you decide that is not enough, you can always do aero mods. I have yet to see many people go that far yet but check this guy out?!?

He got 5 mpg from blocking the grill and fogs with tape!
http://ecomodder.com/forum/showthread.php/scion-xa-aero-mods-2969.html

 

[Sveivo]

You can always increase your mpg if you driving habits are good and you are stock.

CAI, UDP, Header, midpipe w/ highflow cat, lightweight wheels, narrow tires, higher than oem psi in tires (32psi), no roof rack, oem sized front drill slotted rotors, and keep your car waxed.


If you decide that is not enough, you can always do aero mods. I have yet to see many people go that far yet but check this guy out?!?

He got 5 mpg from blocking the grill and fogs with tape!
http://ecomodder.com/forum/showthread.php/scion-xa-aero-mods-2969.html

I try to stay away from a lot of exhaust mods due to noise; however, I don't doubt it helps a lot!

As far as blocking the grille... Doesn't it cause things to run hotter? I know it's just the upper grille, but still.

I personally noticed an increase in mileage after lowering the car... 1 or 2 mpg... But maybe there is something else involved.

 

[pasadena_commut]

and keep your car waxed.

That's good for the paint, but MPG? While it is true that dirty airliners have higher drag than clean ones, they are moving a heck of a lot faster than I hope to ever see in the P5. On the other hand, extensive hail damage might actually make the car a little more slippery, via the golf ball dimple effect.

If you decide that is not enough, you can always do aero mods. I have yet to see many people go that far yet but check this guy out?!?

He got 5 mpg from blocking the grill and fogs with tape!
http://ecomodder.com/forum/showthread.php/scion-xa-aero-mods-2969.html

I loved the poor man's wind tunnel - bits of yarn stuck all over the car and a buddy driving alongside with a camera. The guy claims his car doesn't overheat with the grill blocked off like that. That is a bit hard to believe - the manufacturers put the radiator behind the grill for a reason.

For the P5 the recessed fogs would also be a good place to start. Although, once covered you would not want to turn them on, it might even be a fire hazard. Speaking of fire hazard, I do hope that guy kept the duct tape away from all the hot bits.

I also wonder about the plastic ridge that runs under the front bumper. Not sure what it's called, or what it's actually for, but I'm talking about the one that scrapes on some concrete parking wheel stops if you drive too far forward. The thing is what, 4 feet across and 2 inches or so high. Imagine what it would do to airflow if it ran across the hood - it is probably causing nearly as much drag where it is now on the bottom of the car.

 

[Sveivo]

That's good for the paint, but MPG? While it is true that dirty airliners have higher drag than clean ones, they are moving a heck of a lot faster than I hope to ever see in the P5. On the other hand, extensive hail damage might actually make the car a little more slippery, via the golf ball dimple effect.

LOL. Are we taking this a bit too far?

The ecomodder link is right up there with being a little crazy. Very creative and thought out though...

 

[gottacatchup]

That's good for the paint, but MPG? While it is true that dirty airliners have higher drag than clean ones, they are moving a heck of a lot faster than I hope to ever see in the P5. On the other hand, extensive hail damage might actually make the car a little more slippery, via the golf ball dimple effect.



I loved the poor man's wind tunnel - bits of yarn stuck all over the car and a buddy driving alongside with a camera. The guy claims his car doesn't overheat with the grill blocked off like that. That is a bit hard to believe - the manufacturers put the radiator behind the grill for a reason.

For the P5 the recessed fogs would also be a good place to start. Although, once covered you would not want to turn them on, it might even be a fire hazard. Speaking of fire hazard, I do hope that guy kept the duct tape away from all the hot bits.

I also wonder about the plastic ridge that runs under the front bumper. Not sure what it's called, or what it's actually for, but I'm talking about the one that scrapes on some concrete parking wheel stops if you drive too far forward. The thing is what, 4 feet across and 2 inches or so high. Imagine what it would do to airflow if it ran across the hood - it is probably causing nearly as much drag where it is now on the bottom of the car.

Dimples only help air flow and reduce drag on relatively small objects. It works very well on golf balls and other objects maybe under a foot wide but not on a car. The principle behind it is that it turns the airflow turbulent which causes the boundary layer to remain attached longer. An attached boundary layer produces less drag than a detached one. However a car is big enough that putting dimples on the surface wont change the fact that the boundary layer is turbulent and most likely unattached.

That being said it would make sense to take a ball peen hammer to your side mirrors. They're the right scale to have this surface finish make a difference. They do it in F1 so it must be true right?

 

[maxek]

Is Anybody trying this?

 

[pasadena_commut]

Is Anybody trying this?

Trying what, dimpling the side mirrors? Doubt it, there will not be much of a gain from it even if it works. Eliminating the side mirrors would be much more effective. Google around and you'll find a lot of material on it, although mostly on concept cars. Here's a guy who took a pretty comprehensive look at it:

http://www.metrompg.com/posts/mirrors.htm

 

[SlowPro98]

Instead of crying and whining - maybe we just need to change our habits.

agreed. My wife and I both focus on gas conservation. most of the time(ugh). regular gas is between $4.27 to $4.29. I found a place that does cash only for $4.19 yesterday, but it's all the way out in ellington.
prices aren't going down, so our speed must go down. I get the miata up to speed and just coast as much as possible. I get away with putting in a few bucks every few days, never really filling her up.
The wagon does great as long as we use the cruise. Jess only fills up twice a week. We're going to New Hampshire tomorrow and we're going to ease our way up there and save $.30 by gassing up there.

 

[niky]

For the best mpg in the hills you do not want engine or any other kind of braking going down the hills. Its just like a high school physics experiment, you want the marble to roll freely down the first hill and then use that kinetic energy to get back up the second. The laws of physics say one thing, but the laws of the highway patrol say another - if you convert all the PE to KE on a long hill the car could easily be going 110 or 120 mph (wherever wind drag equals the pull from gravity). The cops will not be amused.

Some guy did that in the Ultimate Street Car Challenge at SportCompactCar. Got 40 mpg out of a 400 hp twincharged MR2. Smart guy.

That's good for the paint, but MPG? While it is true that dirty airliners have higher drag than clean ones, they are moving a heck of a lot faster than I hope to ever see in the P5. On the other hand, extensive hail damage might actually make the car a little more slippery, via the golf ball dimple effect.

I loved the poor man's wind tunnel - bits of yarn stuck all over the car and a buddy driving alongside with a camera. The guy claims his car doesn't overheat with the grill blocked off like that. That is a bit hard to believe - the manufacturers put the radiator behind the grill for a reason.

For the P5 the recessed fogs would also be a good place to start. Although, once covered you would not want to turn them on, it might even be a fire hazard. Speaking of fire hazard, I do hope that guy kept the duct tape away from all the hot bits.

I also wonder about the plastic ridge that runs under the front bumper. Not sure what it's called, or what it's actually for, but I'm talking about the one that scrapes on some concrete parking wheel stops if you drive too far forward. The thing is what, 4 feet across and 2 inches or so high. Imagine what it would do to airflow if it ran across the hood - it is probably causing nearly as much drag where it is now on the bottom of the car.

RE: dimple effect, read up on vortex generators. If you've got a P5, you can stick a bunch of these near the trailing edge of the roof to reduce the turbulence in the car's wake. A bit of trial and error to get it right, but you could save a few mpg that way. There's a cheap commercially available vortex generator called the "airtab". But cheap as it is, I think you could work up something nearly as effective with stuff you can buy from the hardware store.

You don't really need a grille at speed... that's why 92 Honda's didn't have them. You have a lot of air entering the radiator from the bumper inlet.

RE: plastic chin: You actually want that thing under the car... it keeps air from going under it and jostling around on all those protruberances down there. If you could make a flat undertray for the rear bumper and some air deflectors to put in front of your wheel wells (which act like giant parachutes), then you can probably remove it and make your car much more aerodynamic without having to tape up everything on top.

 

[Magus]

NEWS: The blue wagon is in testing. I have put blue painters tape temporary on my upper grill and fog lamps to test for aero drag improvements.

The Route: Elkton, MD to Laurel, MD. This is mainly a freeway drive, but has stop and go traffic through Baltimore. The trip is 77 miles one way and I drive this down and back everyday.

Results thus far: The car has not over heated as others have guessed. The way the lower grill is designed, the air is shoved in a upper wards direction. I would probably be wary on a large engine or turbo vehicle. Heck even the OEM intake takes air from the crack between the hood and the grill. I will posts pictures later tonight hopefully. Some tape has tried to come off, but was easily removed and very little. I choose the painters tape to prevent residue, and for not sticking out too bad. If this works, I will be trying to create a solid grill for permanent use. The real problem is how to fill in the fog spots.

Other news: Driving the speed limit vs. 5mph over has net ~2 mpg.


As for the underside air dam, it's purpose is to shove the air away from parts that would cause more drag and turbulence under the car. Ecomodders are putting air dams in front of the wheels and trying to smooth out the rearend of the car. Lowering the car helps minimize the amount of air, and makes the from air dam more effective. I would spend money on lowering, but it's going to take $500+ to do it right. The header with mid-pipe will be cheaper.

 

[pasadena_commut]

RE: dimple effect, read up on vortex generators. If you've got a P5, you can stick a bunch of these near the trailing edge of the roof to reduce the turbulence in the car's wake.

Not sure that's the right thing to do on a wagon. Isn't the spoiler there specifically to kick the air off the back of the car? The vortex generators are used on sedans to keep the boundary layer attached to the back window. I did not see a reference to using them on a wagon.

I think my first aerodynamics project will actually be on my wife's Subaru Legacy wagon. That is the car we take on long highway trips, and it still has the roof rack cross bars on - even though we never use the rack. Those gotta go! I do not think it is as easy to remove the rest of the rack as on the P5, but the pieces that run down the length of the roof should not cause as much drag as the cross bars.

 

[niky]

You can do the poor man's wind-tunnel mentioned earlier, stick bits of yarn to the back of the P5 and see if the turbulent wake sticks to the back of the car. If it doesn't, your spoiler is doing its work.

The airtab thing isn't quite like the vortex generator on the Lancer Evolution. It's designed to push the air away from the car instead of making it stick. It's most popular amongst truckers, who've got big, flat vehicles with big broadsides. Experiments by car owners have yielded minimal gains, which means you might not be able to justify the price for the commercial items, but you might be able to justify making your own following the design from pics off the web.

But again, if your spoiler already does that, then you can experiment with other places. If I recall correctly, Honda and Toyota use a protrusion on the edges of their headlights (at the front corner of the car) to smooth airflow over the car. That's one place you might be able to use a vortex generator to good effect.

And there's always the wheel-well air-deflector. Am planning to DIY this on the car... trying to eke out a few ticks more acceleration from 0-100 mph on my car.

 

[P-Funk!]

Not sure that's the right thing to do on a wagon. Isn't the spoiler there specifically to kick the air off the back of the car? The vortex generators are used on sedans to keep the boundary layer attached to the back window. I did not see a reference to using them on a wagon.
(attn)
The 'spoiler ' on the back of the P5 is useless from an aero standpoint. The reason the back gets so dirty so quickly is the low pressure area on the hatch. It literally vacuums up the road water/dirt/exhaust gas.

The ideal 'spoiler' is really the dimples like on the roof of a Mitsu EVO to break up the non-laminar flow (anything past 1/4 length of the vehicle roof is non-laminar already and help break up the low pressure on the hatch.

Add the mitsu EVO vortex generators to the 'spoiler' and test with the yarn on the hatch. The vortex genrators would have to be taller (~2") to be effective on our longer roofs.

(Me? MS/Engineering and Aeronautical Science)



I think my first aerodynamics project will actually be on my wife's Subaru Legacy wagon. That is the car we take on long highway trips, and it still has the roof rack cross bars on - even though we never use the rack. Those gotta go! I do not think it is as easy to remove the rest of the rack as on the P5, but the pieces that run down the length of the roof should not cause as much drag as the cross bars. True.

 

[pasadena_commut]

The 'spoiler ' on the back of the P5 is useless from an aero standpoint. The reason the back gets so dirty so quickly is the low pressure area on the hatch. It literally vacuums up the road water/dirt/exhaust gas.

The ideal 'spoiler' is really the dimples like on the roof of a Mitsu EVO to break up the non-laminar flow (anything past 1/4 length of the vehicle roof is non-laminar already and help break up the low pressure on the hatch.

Add the mitsu EVO vortex generators to the 'spoiler' and test with the yarn on the hatch. The vortex genrators would have to be taller (~2") to be effective on our longer roofs.

The spoiler can be removed pretty easily, leaving 4 holes where one could mount whatever aerodynamic device is desired. Of course the 3rd brake light would need to be relocated.

The wife's Subie wagon has no spoiler, well, other than a tiny sort of bend at the trailing edge of the roof. The Subie's back window gets filthy just as fast as the P5's does. Every wagon I've ever driven had that same problem.

 

[red95_240sx]

...draft people...

 

[323]

my rear bumper collects a lot of dirt as well

 

[pasadena_commut]

Looked around for the coefficient of drag for the P5 and finally found it on motortrend here:

http://www.motortrend.com/cars/2003/mazda/protege5/specifications/index.html

as 0.32. Bizarrely, that was exactly the same value cited for a 2002 DX Sedan (roughly the same car, as a sedan), a 2004 Mazda 3 (roughly the same car with what appears to be a more streamlined body), and even a 2000 Subaru L Wagon (our other family car). Ok, maybe the 3 and the P5 come out the same, and maybe the bigger Subie wagon is the same too, since it is pretty close in shape, but how can the Protege sedan possibly have the same Cd as the P5 wagon?

 

[pasadena_commut]

Remember the air deflector underneath the front of the P5? Mazda went a different way with the Mazda6. In this article

http://forum.***************/lofiversion/index.php/t91862.html

they cite a 0.30 Cd for the Mazda6, and state that it is partially the result of the per wheel wind deflectors, which are shown here:

http://img142.imageshack.us/my.php?image=10022008316vo0.jpg

Click on the picture to get it to full size and you will be able to see that there is much more attention on the 6 than on the P5 to under chassis aerodynamics, with plastic (?) plates extending to at least the back of the front wheels. There is no full width air deflector on the 6, at least not one before the front wheels, instead they chose to smooth the bottom of the car.

 

[P-Funk!]

Looked around for the for the P5 and finally found it on motortrend here:

http://www.motortrend.com/cars/2003/mazda/protege5/specifications/index.html

as 0.32. Bizarrely, that was exactly the same value cited for a 2002 DX Sedan (roughly the same car, as a sedan), a 2004 Mazda 3 (roughly the same car with what appears to be a more streamlined body), and even a 2000 Subaru L Wagon (our other family car). Ok, maybe the 3 and the P5 come out the same, and maybe the bigger Subie wagon is the same too, since it is pretty close in shape, but how can the Protege sedan possibly have the same Cd as the P5 wagon?

Because the coefficient of drag is MOSTLY based on the frontal area of the body. Other factors are the length, tire/wheel width, ride height etc...