Regarding Smack’s Newest Video.

[BoyntonStu]

Regarding Smack’s Newest Video.

http://www.youtube.com/watch?v=xe4uWoO-TJg

I sent this comment :

If, according to your video statements, Hydroxy can only increase mileage by 12%-20% why not use a much simpler method?

Restrict the air about 25% and the ECU will be fooled into thinking it is in Denver or another high altitude location.

For less air, it will reduce to gas to keep 14.7:1 ratio.

My car went from 28 to 32 MPG using 10 cents worth of duct tape.

BoyntonStu

[alpha-dog]

I installed a PSC1 which does remap the entire fuel map. I wasn't having good results with the EFIE and I used pre and post cat EFIE's. I will be tuning once my wideband A/F ratio meter is installed. Nice thing about this PSC1 is that it has a wire used for nitrious oxide which I believe could be used to kick on another electrolyser at a higher rpm. I could boost HHO output up to 7Lpm above 1600 rpm. I'll probably need to upgrade my alternator for that. I want to suggest to all of you to look at some of the racing products like the PSC1-023 to control your A/F mix.

[BoyntonStu]

I installed a PSC1 which does remap the entire fuel map. I wasn't having good results with the EFIE and I used pre and post cat EFIE's. I will be tuning once my wideband A/F ratio meter is installed. Nice thing about this PSC1 is that it has a wire used for nitrious oxide which I believe could be used to kick on another electrolyser at a higher rpm. I could boost HHO output up to 7Lpm above 1600 rpm. I'll probably need to upgrade my alternator for that. I want to suggest to all of you to look at some of the racing products like the PSC1-023 to control your A/F mix.


If, Smack is correct, and after all the work and investment, Hydroxy, EFIE, bubbler, etc. won't due much better than 10 cents worth of duct tape, why mess with it?

BoyntonStu

[bigjim56]

I watched the video and was surprised that he uses the hydroxy on his bike w/a PC3. That's what I run on my bike. He is correct that in order to run it most efficiently it needs to be "mapped" at a local mc shop that tunes these units. This map run will cost $150-200 though, so its rather costly, and any adjustments made after can deter the map setting.

The nice thing is the map can be safely stored on your laptop and reset or retuned (or kept stock) as needed, and reinstalled thru the PC3 fitting in the back of the unit. The PC3 is a very nice and handy unit for a motorcycle w/fuel injection. There are many rider maps out there on the PC3 website (and other rider websites/VTXOA.COM) that will come very close to the characteristics of your ride...aftermarket pipes/hypercharger/etc. I found a map from a rider w/very like engine add on characteristics and installed on my bike and it runs awesome. I'm sure it would run stronger w/HHO, but its not worth the $ to find out. How much power is enough?

bigjim56

[BoyntonStu]

Because $.10 worth of duct tape does nothing to help emissions (and probably makes them worst).

Actually 10 cents worth of duct tape actually does reduce emissions.

Less air, less gas, same 14.7:1 ratio, generates less pollution.

Are you stating that folks like us should spend our time and money to clean our car emissions if for nothing else?

BoyntonStu

[locco]

less air, less fuel = less power

If you want to climb the same hill etc, you'll need to press the accelerator in further thus pumping more air+fuel in to produce the same amount of power that you were using before to climb the same hill.

If only it were that simple :)

[BoyntonStu]

less air, less fuel = less power

If you want to climb the same hill etc, you'll need to press the accelerator in further thus pumping more air+fuel in to produce the same amount of power that you were using before to climb the same hill.

If only it were that simple :)

Actually it is..

4 cylinder cars get up the same hill as 6 or 8 .cylinders.

The question is how much power is required?


On level ground do you require 0-60 on 8 seconds or would 10 seconds be quick enough?

Saves you gas at slower acceleration with less power for certain.


A buttery air restrictor that opens on full throttle will get you back to 8 seconds.

The cars in mile high Denver have no choice but to run at lower power than they could at sea level.

Simple enough?

BoyntonStu

[locco]

4 cylinder cars get up the same hill by reving higher at a lower torque thus producing the same amount of power (assuming both cars weigh the same) that the v8 used (same amount of power implies the same amount of time to to get up the hill). The only difference is that the 4 cyl did it at wide open throttle thus deacreasing pumping losses, so it burnt less fuel.

The only thing the tape obstruction seems to be doing is forcing the throttle to open further.. but..

In Denver the altitude means that the air is at a lower density. So for the same 100% cylinder volume your engine can draw in, it will only be getting lets say 80% air/oxygen as compared to sea level. So in Denver you get an 80% air charged cylinder across the whole throttle angle, While by blocking the intake (by 20% area) you'd only be achiving Denvor conditions from 80% to 100% wide open throttle. From 1% to 80% open trottle the cylinder is still seeing a full 100% air charge as the tape restriction is having no effect.

So you're really restricting the driver by reducing the available power from 80%+ WOT. so it's more of a social enginering device :) So I can see now how you'd save fuel using tape, personally though I'll just stick to my granny like driving habbits to conserve fuel with the option to open her up when I need to overtake. I need all the power I can get from my little 1.8L :)

[BoyntonStu]

"While by blocking the intake (by 20% area) you'd only be achiving Denvor conditions.

If you stop here it would be correct.



from 80% to 100% wide open throttle.

Incorrect. A 20% air restriction results in 20% less dense air (as measured on the MAF). From idle to 100%, the MAF sees 20% less air that without the restriction.



From 1% to 80% open trottle the cylinder is still seeing a full 100% air charge as the tape restriction is having no effect. See above.


The beauty of a throttle controlled butterfly is that when you desire it, it will open to 99%.


BoyntonStu

[locco]

Boynton, I'm still not understanding your logic. Explaining things online can be challenging without a napkin to scrilbble on :)

A 20% air restriction only comes into play (reduced density is calculated by ecu from MAF input and assumed intake diameter/area) above 80% throttle as before this the throttle controls the amount of flow as it's the largest restrictor. So when the throttle is opened 20% the MAF sees 20% of total possible air flow (air mass), not 16% as your logic would have it, this is because the tape restriction can't selectivelly block air. In your scenario for a true 20% reduction in air mass to occur at 20% wide open throttle, you'd need the tape to block 84% of the flow area, so that only 16% of air can get through, therefore making the duct tape the air flow limiter.

So I hope you can see that a constant 20% tape area constriction only overtakes flow control after 80% throttle, until this point the tape has no effect as it lets through 80% of total air flow. Here's a few diagrams to illustrate my point.

http://server3.uploadit.org/files/loccomoffo-denvor_throttle_small.jpg (http://www.uploadit.org)

By oxygen% before the air filter, I really mean 100% available air :)

[BoyntonStu]

Boynton, I'm still not understanding your logic. Explaining things online can be challenging without a napkin to scrilbble on :)

A 20% air restriction only comes into play (reduced density is calculated by ecu from MAF input and assumed intake diameter/area) above 80% throttle as before this the throttle controls the amount of flow as it's the largest restrictor. So when the throttle is opened 20% the MAF sees 20% of total possible air flow (air mass), not 16% as your logic would have it, this is because the tape restriction can't selectivelly block air. In your scenario for a true 20% reduction in air mass to occur at 20% wide open throttle, you'd need the tape to block 84% of the flow area, so that only 16% of air can get through, therefore making the duct tape the air flow limiter.

So I hope you can see that a constant 20% tape area constriction only overtakes flow control after 80% throttle, until this point the tape has no effect as it lets through 80% of total air flow. Here's a few diagrams to illustrate my point.

http://server3.uploadit.org/files/loccomoffo-denvor_throttle_small.jpg (http://www.uploadit.org)

By oxygen% before the air filter, I really mean 100% available air :)

TPI Throttle posigtion indicator.



Throttle Position Sensor Adjustment

Adjusting your throttle position sensor

Phil Coconis / autoMedia.com

Although there are literally dozens of sensors that provide critical data to the engine management computer of a modern, fuel-injected engine, few are actually adjustable, or can be affected by adjustments of related components. The throttle position sensor, often referred to as the TP sensor or TPS, is one of these rare devices.


It is important to get to know the function and servicing of this sensor for a couple of reasons. As with any electro-mechanical moving part, they have been known to malfunction or ultimately just plain wear out. Besides that, they are often victims of improper service procedures. These procedures will either result in damage to the sensor, or impair its range of operation. In any event, a malfunctioning, damaged, or misadjusted TPS will cause a variety of driveablility symptoms, often accompanied by a check engine MIL (malfunction indicator light) displayed on the instrument panel.

Your logic did not include the TPI.

BoyntonStu

[locco]

So are you saying that you adjusted your Throttle Position Sensor when you put the tape on?

[BoyntonStu]

So are you saying that you adjusted your Throttle Position Sensor when you put the tape on?

No adjustment necessary.

Here's the way I believe it works.

You go from idle to 20% throttle position.

The ECU says 20% throttle Hmnn what air do I see?

The MAF indicates tell me that we have less air that at sea level.

I must do my job and deliver just enough gas to create 14.7:1 air:gas ratio.

It does it, and you will get less power.

Less power translates to less performance and less fuel.

Not noticeable except at the gas pump.

Press to 80% throttle or any other preset minimum position and the butterfly opens up.

BoyntonStu

[Painless]

A user on another forums has achieved similar gains on a MAF based truck by installing a device which allows some air to bypass the MAF sensor without being measured. This is without HHO, I need to find out more about the installation but that is essentially how it works.

If I remember correctly, most MAF's sense flow by letting air cool a heated wire and measuring the temp difference.

I'm wondering if simply needing a wider throttle opening to achieve the same HP is creating gains due to the reduced pumping requirements on the engine?

[BoyntonStu]

A user on another forums has achieved similar gains on a MAF based truck by installing a device which allows some air to bypass the MAF sensor without being measured. This is without HHO, I need to find out more about the installation but that is essentially how it works.

If I remember correctly, most MAF's sense flow by letting air cool a heated wire and measuring the temp difference.

I'm wondering if simply needing a wider throttle opening to achieve the same HP is creating gains due to the reduced pumping requirements on the engine?

Let's go back to Genesis.

In Australia, Lyall Bailey was into outboard motor racing.

There were 3 HP classes. 5, 7.5, and 10.

They discovered that all the engines were identical except for the air restriction.

I agree that the air restriction in this case only acts as a power governor at the top end.

This got Lyall to thinking about high altitude and ECU's.

I did what he indicated, and you can visit me in Sunny Florida and see what it feels like in my car.

The MPG gain is real.

Her's the point: My engine is a DOC 2,000 CC Ford ZX2.

It can rev to over 6,000 RPM before seeing red.

I never exceed 3,500 RPM and yet there is MPG gain.

Mixing theory and practice, I know that it works.


I strongly believe that the manufacturers if ECU cars must design for all altitudes.

What do you believe happens if you drive your car to Denver tomorrow and arrive there with half a tank of sea level gas?

BoyntonStu

Why not spend 10 minutes doing it instead of 10 hours talking about it?

Restrict the air, say 20% using duct tape.

Disconnect one battery cable and touch it to the other terminal.

Start your engine and if it idles OK, run a few tanks like that.

Report back with your results.

[Painless]

Let's go back to Genesis.

In Australia, Lyall Bailey was into outboard motor racing.

There were 3 HP classes. 5, 7.5, and 10.

They discovered that all the engines were identical except for the air restriction.

I agree that the air restriction in this case only acts as a power governor at the top end.

This got Lyall to thinking about high altitude and ECU's.

I did what he indicated, and you can visit me in Sunny Florida and see what it feels like in my car.

The MPG gain is real.

Her's the point: My engine is a DOC 2,000 CC Ford ZX2.

It can rev to over 6,000 RPM before seeing red.

I never exceed 3,500 RPM and yet there is MPG gain.

Mixing theory and practice, I know that it works.


I strongly believe that the manufacturers if ECU cars must design for all altitudes.

What do you believe happens if you drive your car to Denver tomorrow and arrive there with half a tank of sea level gas?

BoyntonStu

Why not spend 10 minutes doing it instead of 10 hours talking about it?

Restrict the air, say 20% using duct tape.

Disconnect one battery cable and touch it to the other terminal.

Start your engine and if it idles OK, run a few tanks like that.

Report back with your results.

Stu,

Firstly, please let me make this point clear, there is not a shadow of a doubt in my mind that what you are reporting is true. I have 110% trust in anything that you report.

What I am interested in is learning more about why this works. You may recall that I tried it on my Ram several months ago, I employed a 25% restriction and a computer reset yet saw no changes. My Ram employs an IAT (intake air temp) between the air filter and throttle body and a MAP sensor inside the intake manifold. I'm thinking that this may only work on MAF equipped vehicles. This makes me even more interested to understand why exactly this works and if it can be adapted to MAP vehicles.

I was doing some reading over on the Dodge forums yesterday, most of the members there are into performance, however, some are also interested in MPG. One mod that a lot of the performance guys purchase is called a Power Wire, this is quite simply a 4.7k resistor which is placed in series with the IAT sensor, the effect of which is to fool the ECU into thinking that the intake air is about10-15 F cooler than it really is. This results in an advance in timing and slight richening of fuel at WOT giving better HP.

Yesterday, I was reading another post about the aforementioned Power Wire by one of the guys interested in MPG. He found that at WOT the mod gave more performance, however, at normal driving it gave some extra MPG of fuel economy. My guess here is that the richening of fuel at WOT goes through the ECU fine as it is running in open loop at this point and ignoring the O2's. During normal closed loop driving, the slight fuel richening is reversed by the O2's resulting in just a timing change.

This week I will be performing a one tank test on my HHO setup and employing some risk also. If this tankful returns absolutely no gains or losses in MPG (no electronic mods) and no visibly different fuel trim behaviour I will be removing my HHO cell until such a time as I can afford to employ a much higher volume of gas to experiment with. Meanwhile, I will be working 100% on other non-HHO fuel economy methods.

Russ.

[locco]

BoyntonStu, the TPS isn't used by the ECU to calculate the total amount of fuel injected into the cylinder. It only injects more fuel when the throttle chages quickly, ie. acceleration. The main sensor that dictates the amount of fuel injected into the cylinder is teh MAF, with the 02 sensor used as a trim. Your assumption about less air being detected by the MAF is still wrong under 80% throttle. I'm not sure why you admit that intake restriction curbs peak power in outboards but not in the tape scenario? Also in regards to your RPM, maybe your max power is at 3,500RPM? So the tape is limiting your power/fuel there. Actually the whole argument is null as the O2 sensor would trim your fuel in closed loop at any time you fooled the car to run lean.

Also car manufacturers do design engines for all altitudes as the MAF measures air mass, not volume, therefor no user adjustment is needed when entering less dense air as the MAF takes this into consideration and fuel delivery is calculated accordingly.

Painless, installing a MAF bypass would mean that the bypass would contribute a higher % of total air mass when the throttle was least opened. So it would create a lean mixture at lower engine loads. The bypass would have teh effct of leaning the mixture out less as the throttle was opened up more as the area of the bypass became a smaller % of the overall throttle area. Hope that makes sense :). I guess in this case you would be forced to open the throttle up more to put more fuel/energy into the cylinder. The problem would be raised exhaust temp in open loop which may be problematic in the long run. Overall though in closed loop the 02 sensor would detect a lean burn condition and trim the injectors to pump more fuel in anyway :)

The MAF works by measuring the temp of a heated wire, with the output signal correlating to the amount of current needed to bring the wire back to a standard temp. It measures the mass of air flow.

BoyntonStu, I'll stick the tape onto a well runing car (MAF) next time I fill up and will report back with results. The tape is definatelly not working the way you think it is, the logic just doesn't allow it. The only other way is that it might be introducing turbulance into the airflow thus cousing a better air/fuel mix thus creating a better burn.

Painless, I see that you've been on this forum for a long time, are you giving up on HHO to provide you with fuel savings??

[BoyntonStu]

Stu,

Firstly, please let me make this point clear, there is not a shadow of a doubt in my mind that what you are reporting is true. I have 110% trust in anything that you report.

What I am interested in is learning more about why this works. You may recall that I tried it on my Ram several months ago, I employed a 25% restriction and a computer reset yet saw no changes. My Ram employs an IAT (intake air temp) between the air filter and throttle body and a MAP sensor inside the intake manifold. I'm thinking that this may only work on MAF equipped vehicles. This makes me even more interested to understand why exactly this works and if it can be adapted to MAP vehicles.

I was doing some reading over on the Dodge forums yesterday, most of the members there are into performance, however, some are also interested in MPG. One mod that a lot of the performance guys purchase is called a Power Wire, this is quite simply a 4.7k resistor which is placed in series with the IAT sensor, the effect of which is to fool the ECU into thinking that the intake air is about10-15 F cooler than it really is. This results in an advance in timing and slight richening of fuel at WOT giving better HP.

Yesterday, I was reading another post about the aforementioned Power Wire by one of the guys interested in MPG. He found that at WOT the mod gave more performance, however, at normal driving it gave some extra MPG of fuel economy. My guess here is that the richening of fuel at WOT goes through the ECU fine as it is running in open loop at this point and ignoring the O2's. During normal closed loop driving, the slight fuel richening is reversed by the O2's resulting in just a timing change.

This week I will be performing a one tank test on my HHO setup and employing some risk also. If this tankful returns absolutely no gains or losses in MPG (no electronic mods) and no visibly different fuel trim behaviour I will be removing my HHO cell until such a time as I can afford to employ a much higher volume of gas to experiment with. Meanwhile, I will be working 100% on other non-HHO fuel economy methods.

Russ.

Russ,

Thanks,

In your experiments you have always looked for responses from your engine.

I suggest another air restriction test.

Block your intake 75%, reset the ECU and see if it idles.

It probably will not idle smoothly. Aha! A result.

Slice away some of the duct tape and retry.

There will be a point where it will idle fairly smoothly.

Try a tank with that setting.

Please tell us what you EGT reads.


Back to air restriction theory.

We forgot the human computer.

When we step on the accelerator, we set the power, not the ECU.

The ECU sets the air fuel ratio, and not the power.

IOW When pulling away from a stop light, we decide the acceleration.

If there is air restriction, our 'remembered' foot position will give us less acceleration and more MPG. We hardly notice it, because the car feels right.

No stumbles, just a normal feeling of a slightly less powerful car.


We accept the reduced power subconsciously.

BTW When I replaced my tires with 4% larger diameter ones, it was as if I changed the final drive ratio by 4%. I didn't notice that change.

BBTW Since my current MPG readings are with the 4% larger than stock tires, I would expect that my 28 MPG to 32 MPG readings are 4% lower than it would have been with stock tires.


FWIW

BoyntonStu

[Roland Jacques]

Suject change:D

forgive me, Ive been out of the loop for a while.

What is the Gensets (however it spelled) that Smack refers too in part 4othe the video? at the end time 7:40 http://www.youtube.com/watch?v=fmUsmkQWCf0&feature=related?

He says it will change everythings...

[Gary Diamond]

Suject change:D

forgive me, Ive been out of the loop for a while.

What is the Gensets (however it spelled) that Smack refers too in part 4othe the video? at the end time 7:40 http://www.youtube.com/watch?v=fmUsmkQWCf0&feature=related?

He says it will change everythings...

A genset is a generator and and engine tied together

[Roland Jacques]

I'm still not clear

Does that mean the generator output somehow ties into the engine RPM?

more RPM = more HHO?

[Painless]

Russ,

Thanks,

In your experiments you have always looked for responses from your engine.

I suggest another air restriction test.

Block your intake 75%, reset the ECU and see if it idles.

It probably will not idle smoothly. Aha! A result.

Slice away some of the duct tape and retry.

There will be a point where it will idle fairly smoothly.

Try a tank with that setting.

Please tell us what you EGT reads.


Back to air restriction theory.

We forgot the human computer.

When we step on the accelerator, we set the power, not the ECU.

The ECU sets the air fuel ratio, and not the power.

IOW When pulling away from a stop light, we decide the acceleration.

If there is air restriction, our 'remembered' foot position will give us less acceleration and more MPG. We hardly notice it, because the car feels right.

No stumbles, just a normal feeling of a slightly less powerful car.


We accept the reduced power subconsciously.

BTW When I replaced my tires with 4% larger diameter ones, it was as if I changed the final drive ratio by 4%. I didn't notice that change.

BBTW Since my current MPG readings are with the 4% larger than stock tires, I would expect that my 28 MPG to 32 MPG readings are 4% lower than it would have been with stock tires.


FWIW

BoyntonStu

Once I have my new MAP sensor installed and have run my test tank with the new HHO setup, I'll give the air restriction another try on it's own.

Russ.

[Gary Diamond]

I'm still not clear

Does that mean the generator output somehow ties into the engine RPM?

more RPM = more HHO?

If its done right it will have a feed back to the engine

[zachattack]

BoyntonStu.

Just from personal experience of also going 4 tire sizes bigger you will stay the same on mpg but normally decrease mpg.

bigger tire size= more surface in contact with the road. Which makes more friction. In turn using more fuel/power to keep the tires rotating. Or keeping the vehicle at the same speed.

Once again just my own experience and figuring.

zach

[locco]

I'm still not clear

Does that mean the generator output somehow ties into the engine RPM?

more RPM = more HHO?


Roland, The engine in teh genset runs at a constant RPM, when you apply electrical load to it the electrical generator slows the engine down, thus teh engine needs more fuel (conserving energy) to get back up to the same RPM.

So constant RPM. Gen output ties in to fuel consumption. As electrical power (energy/time) must be matched by (engine power) ie fuel input (energy/time)

Hope that helps

[BoyntonStu]

BoyntonStu.

Just from personal experience of also going 4 tire sizes bigger you will stay the same on mpg but normally decrease mpg.

bigger tire size= more surface in contact with the road. Which makes more friction. In turn using more fuel/power to keep the tires rotating. Or keeping the vehicle at the same speed.

Once again just my own experience and figuring.

zach

Zach,

I put +1 size tire on my car and the speedo/odo are more accurate.

Car manufacturers may not allow them to show slower than true.

More tire contact creates less friction rather than more friction.

Do you ever place a towel under something you are trying to slide?

However, it is possible to increase tire diameter and not change the contact area by picking the correct tire.

BoyntonStu

[Painless]

More tire contact creates less friction rather than more friction.

If you take 1 flat square foot of rubber and drag that along the road then do the same with 2 flat square feet of rubber, the second will generate more heat because of higher friction of the larger surface.

Are you making a distinction between 'friction' and 'grip'?

I'm confused.

Russ.

[BoyntonStu]

If you take 1 flat square foot of rubber and drag that along the road then do the same with 2 flat square feet of rubber, the second will generate more heat because of higher friction of the larger surface.

Are you making a distinction between 'friction' and 'grip'?

I'm confused.

Russ.

Russ,

The nail has been hit on the head!

When you want a chair to slide across a floor, you want big foot pads under the legs for less sliding friction.

Imagine chair legs with nails for feet. These tiny 'tires' have enough friction to scrape and scratch your floor.

"Friction should not be confused with traction. Surface area does not affect friction significantly because as contact area increases, force per unit area decreases. However, in traction surface area is essential."

BTW Dragsters can produce traction greater than the normal force to the track.

There is almost a meshing of teeth and gear effect as the rubber 'fills' the voids in the track for greater than sliding friction accelerating forces.


BoyntonStu

[Roland Jacques]

Roland, The engine in teh genset runs at a constant RPM, when you apply electrical load to it the electrical generator slows the engine down, thus teh engine needs more fuel (conserving energy) to get back up to the same RPM.

So constant RPM. Gen output ties in to fuel consumption. As electrical power (energy/time) must be matched by (engine power) ie fuel input (energy/time)

Hope that helps

Yes it helps

Its been a long time but, i think we called devices like that a governor, so Thank you

[zachattack]

Wow guess I was off base on the tire size. Thanks for the info.

Zach

[locco]

Yes it helps

Its been a long time but, i think we called devices like that a governor, so Thank you

Roland, they're still called governors :) simple centrifugal weights which apply force to the throttle when the RPMs drop.

[locco]

When you want a chair to slide across a floor, you want big foot pads under the legs for less sliding friction.

Imagine chair legs with nails for feet. These tiny 'tires' have enough friction to scrape and scratch your floor.

BoyntonStu

Stu, if your chair is cutting into the floor then it's not a function of friction anymore :) It becomes a function of material properties and pressure applied (weight/area). Force needed to overcome friction is independent of surface area. It seems couter intuative I know, but you can't argue with physics :)

Draging flat rubber on the ground would fall under static (to get the rubber going initailly) and kinetic friction (on the go force required to pull it)

http://en.wikipedia.org/wiki/Friction

Tire resistence would fall under rolling friction (formula example half way down)

http://en.wikipedia.org/wiki/Rolling_resistance

All three friction types are surface area independent and give you the FORCE needed to overcome the friction/resistence between the two materials.

So increasing tire pressure which is recommended so often in many sources to save fuel must work by decreasing the rolling friction coefficient and not by decreasing contact area of the tire...I can't find any data on pressure vs rolling friction coefficient :(

Interesting thread
http://www.eng-tips.com/viewthread.cfm?qid=141306&page=3

Tires on hybrids
http://www.hybridcars.com/gas-mileage-factors/low-resistance-tires.html

[H2OPWR]

[QUOTE=locco;25804]
Tire resistence would fall under rolling friction (formula example half way down)

http://en.wikipedia.org/wiki/Rolling_resistance

So increasing tire pressure which is recommended so often in many sources to save fuel must work by decreasing the rolling friction coefficient and not by decreasing contact area of the tire...I can't find any data on pressure vs rolling friction coefficient :(

Increasing tire pressure inproves fuel economy by reducing the contact patch with the pavement PERIOD. The less contact area with the pavement the easier the tire rotates improving fuel economy.

Larry

[zachattack]

Lets say you have tires that have a 50,000 mile warranty. Most last 40,00-50,000 depending on inflation, rotating, and driving style. Under inflation will wear the outside of the tread faster than the middle. Over inflation will wear the middle tread faster than the outside. Which would wear your tires improperly thus causing you to purchase tires way before 50,000 miles. More like 25,000 miles. And the cost of tires wearing out that fast would not be equal to the small gain in mpg you get. Or at least it wasn't from my own personal experience on my F250 diesel truck.

Zach

[H2OPWR]

Lets say you have tires that have a 50,000 mile warranty. Most last 40,00-50,000 depending on inflation, rotating, and driving style. Under inflation will wear the outside of the tread faster than the middle. Over inflation will wear the middle tread faster than the outside. Which would wear your tires improperly thus causing you to purchase tires way before 50,000 miles. More like 25,000 miles. And the cost of tires wearing out that fast would not be equal to the small gain in mpg you get. Or at least it wasn't from my own personal experience on my F250 diesel truck.

Zach

You are absolutely correct. You can not gain enough fuel economy by overinflating your tires to overcome the wear.

Larry

[locco]

Larry,

Physics states that all three friction types are surface area independent.

You're right, inflating tyres reduces contact area, but this is irrelevant to the final outcome of rolling resistence. Look at the rolling friction formula, contact area doesn't feature in it. It's counter intuative but its a hard fact.

Looking at it in a different way... by reducing surface area you're increasing the pressure (weight/area) between the road and tire. So the surfaces are pressed together harder so the drag between them is higher...equaling the same rolling resistence.

To save some fuel just buy some low rolling resistence tires next time, which are available from nearly all manufacturers now.

[H2OPWR]

Larry,

Physics states that all three friction types are surface area independent.

You're right, inflating tyres reduces contact area, but this is irrelevant to the final outcome of rolling resistence. Look at the rolling friction formula, contact area doesn't feature in it. It's counter intuative but its a hard fact.

Looking at it in a different way... by reducing surface area you're increasing the pressure (weight/area) between the road and tire. So the surfaces are pressed together harder so the drag between them is higher...equaling the same rolling resistence.

To save some fuel just buy some low rolling resistence tires next time, which are available from nearly all manufacturers now.

If this is true then why do the best racing bikes have very skinny tires with very high pressures? They strive to have the smallest contact patch possible with the road.

Larry

[locco]

Not for the reasons I've stated before unless we want to rewrite the laws of physics. But please find something concrete to explain this so you can share with us. I'm just as curious as you are.

Showing that B is caused by A without supporting theory can prove problematic. It's too easy to draw too many false conclusions this way.

Why do the top race cars use such wide tires? To maximise tire contact?

As for motorbikes, the way I'd explain it using physics is... following the rolling friction law

RRC = (Force to overcome RRC x tyre radius)/vehicle weight

A motorbike having a lower weight than a car (but roughly same wheel radius), has a much higher RRC thus needing a smaller tire contact area.

Not to mention smaller power that needs to be delivered, plus the need to easily lean the bike as it turns.

[H2OPWR]

Not for the reasons I've stated before unless we want to rewrite the laws of physics. But please find something concrete to explain this so you can share with us. I'm just as curious as you are.

Showing that B is caused by A without supporting theory can prove problematic. It's too easy to draw too many false conclusions this way.

Why do the top race cars use such wide tires? To maximise tire contact?

As for motorbikes, the way I'd explain it using physics is... following the rolling friction law

RRC = (Force to overcome RRC x tyre radius)/vehicle weight

A motorbike having a lower weight than a car (but roughly same wheel radius), has a much higher RRC thus needing a smaller tire contact area.

Not to mention smaller power that needs to be delivered, plus the need to easily lean the bike as it turns.

I for sure do not have all the answers but I do know that race cars have wide tires for traction alone. Fast around a corner is way more important than fast down a straight away if you want to win.

[locco]

From the reading I've done it seems that wider tires allow for a softer compound to be used on the tire. This is because the shear forces generated during cornering are resisted by a greater cross sectioon of tire thus reducing shear stress thus allowing for weaker/softer rubber to be used.

Thus: wider tire = lower shear stress = softer/weaker rubber = higher RRC = more grip

Once again increased contact area does not increase RRC using the same rubber

Anyway I think we've hijacked this thread enough now, appologies. Time to move on...