Case Study: 45% above EPA?

[wobombat]

Originally Posted by jeff88

Why 45%? Or are you trying to increase your FE by 10mpg and the percent is not your concern?

In terms of maintenance, definitely check your battery. If you have even a less then perfect battery, your alternator will be working harder, negatively effecting your FE. Make sure your oil and transmission fluid are not only "fresh", but not too full, it will make the bottom end of your engine and transmission work harder.

Do you have LEDs?

In terms of aero, I would do a rear diffuser. It is relatively simple, easy to take off, depending on how you design it and can be fairly well hidden if you want it to be.

What part of Oakland? I assume you are staying well clear of the "Maze".

26 was an arbitrary number.
I really do not understand your logic concerning the battery. The battery simply holds energy, and has nothing to do with how much power is being consumed or the load on the alternator.
The transmission fluid in my tranny is in a closed system and is ridiculously hard to open and change the fluid levels. I keep the engine oil midway between the points on the dipstick.
I do not have LED's. I know they'd save energy, but the initial price would never be made back given the age of the car.
Looking into the rear diffuser, I'm afraid I don't have the expertise to make that.
And yes, I stay clear of the Maze. I don't actually live in Oakland, (Lafayette) but I work in Oakland.

Originally Posted by 101Volts

Also, I must again mention proper tire pressure; If you exceed the most fuel-efficient pressure (Which may be lower than you think,) Your FE is going to go down a lot more than you may think.

How does this work? The more pressure in the tires, the less tire on the road, right? What would counteract this at higher pressures?

[jeff88]

The more you work the alternator, the more energy from your engine goes to your alternator/battery and not to your drive train.
Check out this thread:
http://ecomodder.com/forum/showthrea...age-25288.html

[wmjinman]

I think the deal with the battery has to do with the charging. I believe the voltage regulator tries to make the battery charge until it reaches a certain voltage (13.5 -14 if I'm remembering right) Let's say your battery is "on it's way out" and only goes to 12.5 or lower when charged as full as it can get. The voltage regulator will be saying, "nope, not up to 13.5-14 yet, so keep charging". My grasp on electronics is kinda weak, so I might be totally wrong here, but that would be my guess....

The mileage actually starting to go DOWN as the tire pressure continues to rise is something I don't quite "get" either. If it starts to level off at a certain point, I could see that, but actually starting to go back down????? Of course, I'm thinking GAS mileage - I can see the centers of the tread wearing out prematurely if pumped way up all the time.

It's exciting you have a ScanGauge on the way! I predict you're gonna love it! Be sure to learn how to calibrate it in your first 2 fill-ups once you get it, then also how to do the averages in the "trip" feature. The "current" is used to do A-B-A testing, and otherwise I love to drive around with "tank" average showing, so I kinda know how I'm doing for the tank.

As far as not having cruise control, that's too bad, but you can still do valid testing. You'll just have to concentrate really hard on keeping your speed steady - and even harder on not subconsciously "skewing" the test my driving slightly more economically when testing the thing you're hoping will work.

I'd suggest finding your maximum mpg speed first. It probably won't be a surprise - sounds like you pretty much have it figured out the slowest you can go in top gear.

Oh, you know what's really neat? When you get your ScanGauge "calibrated" (on your 2nd fill-up after you hook it up), and then when driving your Max MPG speed, you see you're getting way better than you need to achieve your +45% to convince your friend. Then the challenge will be to try to KEEP that MPG going on forever. I think that's what finally got me serious about the LONG coasting up to stoplights (and watching the MPG go up), and then accelerating faster than I used to so I'd be back up at "Max MPG speed" as soon as possible.

[RedDevil]

Originally Posted by IamIan

... Momentum however is not the same thing as Kinetic Energy ...

True. As momentum also takes the directional component into the equasion. Boldly said it is kinetic energy plus a direction. I meant to say kinetic energy, it is just hard not being a native English speaker. The energy level in momentum is known, it all comes down to hair-splitting on definitions.

I will not discuss these points any further. It just distracts from the topic.
Readers with a strong knowlegde of physics don't need this information anyhow, and those who don't will not likely be convinced by either of us.

[IamIan]

Originally Posted by RedDevil

True. As momentum also takes the directional component into the equasion. Boldly said it is kinetic energy plus a direction. I meant to say kinetic energy, it is just hard not being a native English speaker. The energy level in momentum is known, it all comes down to hair-splitting on definitions.

I will not discuss these points any further. It just distracts from the topic.
Readers with a strong knowlegde of physics don't need this information anyhow, and those who don't will not likely be convinced by either of us.

While I agree to a degree ... I'll disagree on a few thing ... And I think it is more useful to people to understand it correctly than not... that makes one more likely to be able to maximize the pros an minimize the cons when one understands how it works... as such I don't think it detracts at all ... I think it adds to the knowledge base that is completely relevant to this thread.

Momentum is not just kinetic energy with direction ... it is not splitting hairs over definitions ... they are different things ... as different as blue and red are both colors but are not the same thing.

Yes both refer to movement but they are not the same thing ... momentum is never measured in joules ... it is not a term for energy.

For example:

The basic equation for momentum of a moving object is given by p=mv.
And it does not give you an p of momentum in joules ... because momentum is not energy.

The basic equation for Kinetic Energy of a moving object is given by KE=1/2mv^2 ... and as energy it does give you Kinetic in joules if your other units are matched.

There is a significant difference between them.
If m=1 for both

Initial V = 1 for both
Then Momentum p = 1
Initial Kinetic Energy = 1/2

If the speed ( v) doubles to 2
Momentum p = 2
Kinetic energy = 2

If speed ( v ) triples to 3
Momentum p = 3
Kinetic Energy = 4.5

etc ... they do not grow at the same rate ... they are not measuring the same thing, even if they are both referring to a moving body.

[101Volts]

Originally Posted by wobombat

(Tire pressure quote)

How does this work? The more pressure in the tires, the less tire on the road, right?

(Originally edited on 2013-April-06. Edited again on 2013-September-18: Take the unedited sections of this post with a grain of salt. I think perhaps the van will accelerate faster at a lower tire pressure, But again it'll coast longer too once at a given speed. So, Where does that put a good tire pressure? The one that gives the highest FE and lasts the longest?)

Correct, But I think you should have most of the tire contacting the road at a given time so the tread wears evenly and for other reasons; I did some comparison tests today between 55, 50 and 45 PSI and the car could accelerate quicker at a given engine LOD when at 45 PSI than at 50 or 55 PSI, Thus it allows you to accelerate at the same rate as a higher pressure at a lower engine load which = Higher fuel economy (In theory.)

After you get the ScanGaugeII, You can try comparing tire pressures. See how fast your car accelerates to a given speed at a LOD of 17 or so with 55 PSI compared to 50 PSI and 45 PSI and perhaps even 40 PSI.

(Edit: This next paragraph was taking the SG2 reading for granted when it wasn't calibrated very well.)

Perhaps I'm not thinking of this quite right but I know for one trip I averaged over 38 MPG in Moony with a tire strapped to the roof and very mild pulse and gliding (Without turning the engine off) when the PSI was 45ish and I didn't manage that on a recent trip without the tire strapped on or with roof racks, With an oil change and pizza pans with the tires set at 55ish and heavy load pulse and gliding.

Also, This specific paragraph is a bit off-topic but using the tire pressure pumps at gas stations to deflate the tires may take a lot more time than deflating the tires a bit lower than the PSI you're aiming for with a paper clip and re-inflating them.

[wobombat]

Originally Posted by 101Volts

Correct, But I think you should have most of the tire contacting the road at a given time so the tread wears evenly and for other reasons; I did some comparison tests today between 55, 50 and 45 PSI and the car could accelerate quicker at a given engine LOD when at 45 PSI than at 50 or 55 PSI, Thus = Higher fuel economy (In theory.)

After you get the ScanGaugeII, You can try comparing tire pressures. See how fast your car accelerates to a given speed at a LOD of 17 or so with 55 PSI compared to 50 PSI and 45 PSI and perhaps even 40 PSI.

Perhaps I'm not thinking of this quite right but I know for one trip I averaged over 38 MPG in Moony with a tire strapped to the roof and very mild pulse and gliding (Without turning the engine off) when the PSI was 45ish and I didn't manage that on a recent trip without the tire strapped on or with roof racks, With an oil change and pizza pans with the tires set at 55ish and heavy load pulse and gliding.

Also, This specific paragraph is a bit off-topic but using the tire pressure pumps at gas stations to deflate the tires may take a lot more time than deflating the tires a bit lower than the PSI you're aiming for with a paper clip and re-inflating them.

I can't imagine how the car would accelerate better with lower pressure tires, unless if your tires under high pressure were skidding and you didn't know it because of traction control and the such.
Concerning the trip there are a lot of factors there. I would never base that sort of mileage discrepency solely on tire pressure. For example, if the car is older, then maybe heavy pulses lead to compression losses. Or maybe you had a headwind and it was a cold, rainy day the latter time, but a tailwind and a clear, warm day the former time.
Although I too may be wrong, and I have no hard data to back myself up. But once I get the scanguage I do want to test that out.

Another thing I was thinking of testing concerns an auto tranny's low gears. I was thinking, why is it that manually shifting into low gears slows you down so well? In my car the manual low gears can slow me down really quick even if It's only doing 2500 rpms. The only other thing I could think of that could cause that is if there was a direct connection occurring, or in other words torque converter lock-up. So then, if it is true that the torque converter locks up when manually using low gears, then wouldn't that mean it's more efficient to accelerate in those low gears? I accelerate out of stop signs in low gear because I found I could have really high throttle/load and the car wouldn't shift down (100% throttle possible in an auto with less than 2000 RPM's!), and I feel like I've been wasting much less gas that way.

Anyone know about this?

[101Volts]

Originally Posted by wobombat

I can't imagine how the car would accelerate better with lower pressure tires, unless if your tires under high pressure were skidding and you didn't know it because of traction control and the such.
Concerning the trip there are a lot of factors there. I would never base that sort of mileage discrepency solely on tire pressure. For example, if the car is older, then maybe heavy pulses lead to compression losses. Or maybe you had a headwind and it was a cold, rainy day the latter time, but a tailwind and a clear, warm day the former time.
Although I too may be wrong, and I have no hard data to back myself up. But once I get the scanguage I do want to test that out.

Yes, There are other things I didn't take into consideration; Live and learn. I still have the feeling 45 is more fuel efficient than 50 for the tire and van combo, Though.

And 45 isn't lower than the tire calls for, Maybe 44ish really is the best fuel efficient tire pressure for that tire and car combination.

[RedDevil]

Originally Posted by 101Volts

... I did some comparison tests today between 55, 50 and 45 PSI and the car could accelerate quicker at a given engine LOD when at 45 PSI than at 50 or 55 PSI, Thus it allows you to accelerate at the same rate as a higher pressure at a lower engine load which = Higher fuel economy (In theory.) ...

When I raised the pressure in my tires from 30ish to 45 PSI I noticed that my daily commute distance as indicated by the MID dropped from 36.4 km to 36.2.
A higher tire pressure apparently makes the tire cover more distance per rotation. It gave over 5% better FE, and I can add another 0,55% to that to compensate for the difference in circumference.
It will also make a difference on the ratio between indicated and real speed.

So if you were measuring acceleration by the speedo, MID or SG, here's your answer. Though the difference between 45 and 55 PSI will probably have less effect than the 0.55% I got from raising from 33? PSI to 45.
If you were measuring your speed by GPS; nothing said

[101Volts]

Originally Posted by RedDevil

When I raised the pressure in my tires from 30ish to 45 PSI I noticed that my daily commute distance as indicated by the MID dropped from 36.4 km to 36.2.
A higher tire pressure apparently makes the tire cover more distance per rotation. It gave over 5% better FE, and I can add another 0,55% to that to compensate for the difference in circumference.
It will also make a difference on the ratio between indicated and real speed.

So if you were measuring acceleration by the speedo, MID or SG, here's your answer. Though the difference between 45 and 55 PSI will probably have less effect than the 0.55% I got from raising from 33? PSI to 45.
If you were measuring your speed by GPS; nothing said

Thanks, I do believe you that you get more FE at 45 than at 33 with that tire/car combo. I was using the ScanGauge to monitor the engine load and I could tell without looking at the speedometer that the car was accelerating quicker at 45 PSI and a LOD of 15 than above that. But, I see it as this:

Perhaps it's not raising the pressure in of itself that raises fuel economy (Though that helps with under-inflated tires,) But keeping close to just the right pressure for that tire and vehicle combo is it; Too low, The engine works harder. Too high, The engine works harder. Kinda like Icarus, Except Icarus died from flying too high. (Keep that in mind if over-inflating tires and I speak not only to you here; Over-inflated tires just as under-inflated tires are more vulnerable to a number of things that could put a driver and others in danger plus premature wear on the tires but don't take my word for it, Web Search it.)

And some vehicle and tire combos may be best set at 35 PSI, Some at 44 and some at 50. The number doesn't matter as long as the tires are "Tuned" right for that particular car and tire combo, Like tuning and then intonating a guitar. So what I'm saying is, "Keep in tune for the most efficiency."

(Edit, 2013-September-18: What does it profit if I'm trying to sound wise if I am not?)