[Sutripta]

Originally Posted by CPH

This is 2 examples of real drive train losses on cars that us folk can afford.

Example 1
Transmission loss
@ 2500rpm = 11%
@ 3000rpm = 11%
@ 3500rpm = 11%
@ 4000rpm = 12%
@ 4500rpm = 12%
@ 5000rpm = 12%
@ 5500rpm = 14%
@ 6000rpm = 16%
@ 6500rpm = 19%
@ 6750rpm = 24%

@ peak power 17%

The car was a modified Punto FIRE with 6 speed gearbox.

Example 2
Transmission loss
@ 2500rpm = 17%
@ 3000rpm = 17%
@ 3500rpm = 18%
@ 4000rpm = 20%
@ 4500rpm = 21%
@ 5000rpm = 23%
@ 5500rpm = 26%
@ 6000rpm = 29%
@ 6500rpm = 34%
@ 7000rpm = 39%

@ peak power 29%

Hi,
By transmission loss, you mean power absorbed and dissipated, right?
Do these figures include the rolling resistance of the tyres?

Do you have breakup figures for gbox (layshaft/ epicyclic) diff (hypoid/ spiral), and joints (UJ/ CV)?

Regards
Sutripta

[Shan2nu]

This is 2 examples of real drive train losses on cars that us folk can afford.

Example 1
Transmission loss
@ 2500rpm = 11%
@ 3000rpm = 11%
@ 3500rpm = 11%
@ 4000rpm = 12%
@ 4500rpm = 12%
@ 5000rpm = 12%
@ 5500rpm = 14%
@ 6000rpm = 16%
@ 6500rpm = 19%
@ 6750rpm = 24%

@ peak power 17%

The car was a modified Punto FIRE with 6 speed gearbox.

Example 2
Transmission loss
@ 2500rpm = 17%
@ 3000rpm = 17%
@ 3500rpm = 18%
@ 4000rpm = 20%
@ 4500rpm = 21%
@ 5000rpm = 23%
@ 5500rpm = 26%
@ 6000rpm = 29%
@ 6500rpm = 34%
@ 7000rpm = 39%

@ peak power 29%

Wow, 29% is insane. But isn't the Punto Fire a FWD? Thats a big loss.

Shan2nu

[CPH]

Originally Posted by Shan2nu

Wow, 29% is insane. But isn't the Punto Fire a FWD? Thats a big loss.

Shan2nu

Wider than stock tyres. The top speed lost with the tyres due to softness (grip) and increased witdth is about 15kph. This alone is good for quite a few more %. Also the lowering by 30mm incurred more losses. And the gearbox was new, which means it would loose a bit more power.

The 2 examples are there just to show how difficult it is to determine losses.

Because of it it is absolutely necessary to alter only one component and make sure that all other variables stay as close as possible (i.e. ambient climatic conditions, altitude, dyno, fuel, tyres suspension and positioning on the rollers).

[Rahulkool]

Not to offend anyone but i highly doubt that a car that old will be putting that much power on wheels with those mods. Just my opinion, if one stock car can be dynoed on the same dyno at the same time then only results can give a idea.

[Lalvaz]

Originally Posted by Rahulkool

Not to offend anyone but i highly doubt that a car that old will be putting that much power on wheels with those mods. Just my opinion, if one stock car can be dynoed on the same dyno at the same time then only results can give a idea.

Hmmm.... I guess we'll all have a much clearer picture once GTO does the dyno test for his Civic before and after the mods. I'm sure we'd all like some conclusive evidence of an increase in power before we undertake the mods.

[Sutripta]

Originally Posted by CPH

Example 1
Transmission loss
@ 2500rpm = 11%
....
@ 6750rpm = 24%

Is this a typo?

Originally Posted by CPH

...Also the lowering by 30mm incurred more losses.

Why?

Could you tell us how these loss figures are arrived at?
Also, what would be the loss from crank to hub (leaving aside tyre losses) for a FWD car, and a RWD car.

I am really interested in knowing the losses in an automotive gearbox.

Regards
Sutripta

[CPH]

Originally Posted by Rahulkool

Not to offend anyone but i highly doubt that a car that old will be putting that much power on wheels with those mods. Just my opinion, if one stock car can be dynoed on the same dyno at the same time then only results can give a idea.

Although I understand where you are coming from, I can assure you from experience that was has done to the car has improved performance.

[CPH]

Originally Posted by Sutripta

Is this a typo?


Why?

Could you tell us how these loss figures are arrived at?
Also, what would be the loss from crank to hub (leaving aside tyre losses) for a FWD car, and a RWD car.

I am really interested in knowing the losses in an automotive gearbox.

Regards
Sutripta

It wasn't a typo. This is what we measured.

Lowering affects the wheel power because the drive shaft gets more angled in relation to the gear box. This means more you lower the more energy is being lost in the CV joints.

Unfortunately you can't give exact figures.

Tyre diemsion (not the drag) affect the losses to a certain degree. The further the weight is from the centre of the tyre the more torque is eaten up under acceleration, but this weight has got its plusses too.

The drag losses in the gearbox are partly determined by the gear box fluids. (the old Mini used gearbox oil, some car use ATF, some use heavy gear box oil) the number of gears, differenc in straight cut and cross cut, wear rate, state of fluid and size of gear box components. The flywheel mass is also a factor.

The diff has got its own losses.

RWD unless it is a rear or mid engine with the same gear box configuration as a FWD will have anything between 5 and over v10% more of a loss because of the change of direction.

Automatic gearboxes have varying losses. It also depends whether it is a powder system like Fiat's weird design, belt driven Vario system, solenoid controlled gear box or torque converter box.

Most of the rr manufacturers have the specific loss details on their software.

But the best way to deal with it is going on a rolling road that can assess the losses on coasting, which is not the most straight forward thing to do and most people do it wrong.

[Sutripta]

Hi,
Difficult to inline post, so my comments in bold.

Originally Posted by CPH

It wasn't a typo. This is what we measured.
The loss figures would be easier to comprehend if they were given as absolutes, or as a percent of something fixed (like peak HP). Here I think these refer to % of HP at that particular RPM, which is a varying quantity. If so, the sudden rise (6750 - 24%) can also mean the engine has run out of breath!

Lowering affects the wheel power because the drive shaft gets more angled in relation to the gear box. This means more you lower the more energy is being lost in the CV joints.
Question is how much.

Unfortunately you can't give exact figures.
Ballpark figures?

Tyre diemsion (not the drag) affect the losses to a certain degree. The further the weight is from the centre of the tyre the more torque is eaten up under acceleration, but this weight has got its plusses too.
Would think tyre rolling resistance is a substantial, if not THE substantial contributor for losses.
Does the roller diameter have any part to play?

The drag losses in the gearbox are partly determined by the gear box fluids. (the old Mini used gearbox oil, some car use ATF, some use heavy gear box oil) the number of gears, differenc in straight cut and cross cut, wear rate, state of fluid and size of gear box components. The flywheel mass is also a factor.
These are commonsense factors. Would be interested in some hard figures. Esp for the common 5 speed manual gbox with layshaft and helical cut gears. What losses for direct top (I know, difficult to find in this age of all indirect gboxes)
Aren't the minis gears in the sump?
Why should flywheel mass be a factor?

The diff has got its own losses.

RWD unless it is a rear or mid engine with the same gear box configuration as a FWD will have anything between 5 and over v10% more of a loss because of the change of direction.
Once again figures for a spiral bevel and hypoid bevel setup.

<snip>

But the best way to deal with it is going on a rolling road that can assess the losses on coasting, which is not the most straight forward thing to do and most people do it wrong.

Agreed. The coast down figures are very important. And very easy to get wrong (or to fudge!)

The main unanswered question is how are all these loss figures obtained/ calculated. Because these are added back to crank power.

Regards
Sutripta

[Shan2nu]

Not to offend anyone but i highly doubt that a car that old will be putting that much power on wheels with those mods. Just my opinion, if one stock car can be dynoed on the same dyno at the same time then only results can give a idea.

I dont know whats there to doubt? Its a dyno result afterall. It doesn't really matter what the brochure says. These are real world figures.

And theres no point comparing it to a stock engine, bcoz diff engines age differently. If you want to see what this engine does in stock form, you'l have to fit the stock intake/exhaust and do back to back tests.

Shan2nu

[CPH]

It wasn't a typo. This is what we measured.
The loss figures would be easier to comprehend if they were given as absolutes, or as a percent of something fixed (like peak HP). Here I think these refer to % of HP at that particular RPM, which is a varying quantity. If so, the sudden rise (6750 - 24%) can also mean the engine has run out of breath!

The rise was constant. I have to dig out the graphs, because the figures were taken from a thread I made some time ago. It actually wasn't a sudden rise. The rolling road has got roughly about 800 reference points throughout the rpm range. I just took some to give an indication (otherwise I would sit typing it all month).

Lowering affects the wheel power because the drive shaft gets more angled in relation to the gear box. This means more you lower the more energy is being lost in the CV joints.
Question is how much.

Again this depends on the individual car. If you have a car that is wider than another than the angle changes less than on the car with the narrower track. If you have uneven length drive shafts it will be even worse for the short one.

I don't wan't to be vague (especially as a development engineer) but I can't give even ball park figures when the spectrum is to big. This is why rr manufacturers have done extensive loss testing and have features to include them, but still will maintain that these figures can vary quite substantially due to circumstances, which is the reason why I eather go through the headache of assessing the losses with the correct coasting procedure.

I know this is not what you hope to hear, but I am not giving numbers when they are rather an average figure that can be up or down by 20%.

Unfortunately you can't give exact figures.

Ballpark figures?

As I said above. Giving ball park figures would not be accurate and I am not going to mislead you.

Tyre diemsion (not the drag) affect the losses to a certain degree. The further the weight is from the centre of the tyre the more torque is eaten up under acceleration, but this weight has got its plusses too.
Would think tyre rolling resistance is a substantial, if not THE substantial contributor for losses.
Does the roller diameter have any part to play? [/i]

Rolling resistance is a factor, but not the biggest.

The figures quated were done on a TAT, which I consider as the best rr set-up, which features a massive single roller with a surface that would have not an impact that could be maeasured in %.

With twin rollers the story is a bit different.

The drag losses in the gearbox are partly determined by the gear box fluids. (the old Mini used gearbox oil, some car use ATF, some use heavy gear box oil) the number of gears, differenc in straight cut and cross cut, wear rate, state of fluid and size of gear box components. The flywheel mass is also a factor.
These are commonsense factors. Would be interested in some hard figures. Esp for the common 5 speed manual gbox with layshaft and helical cut gears. What losses for direct top (I know, difficult to find in this age of all indirect gboxes)
Aren't the minis gears in the sump?
Why should flywheel mass be a factor?

The variations between the different gear box oils can be in excess of 5% in drivew train losses. Even with a set box you can have massive differences depending on the wear rate. And a big difference will the location make. Where I used to live we had on extreme summer days up to 55 degress Celsius and the lowest I experienced there was -43 degress Celsius. A starer motor is working hard to turn the engine over with often a much thinner oil and a battery that is kept in the house overnight to be warm enough to give power.

The gear oil might not be far from solid and will possibly on a short run not get warm enough to get to operating temp.

From a cold to a warm gear box oil we measured a total drive train loss of up to 3% difference on a day you Southerners would consider warm to hot.

[Ford Rocam]

Originally Posted by Rahulkool

Not to offend anyone but i highly doubt that a car that old will be putting that much power on wheels with those mods. Just my opinion, if one stock car can be dynoed on the same dyno at the same time then only results can give a idea.

Originally Posted by Shan2nu

I dont know whats there to doubt? Its a dyno result afterall. It doesn't really matter what the brochure says. These are real world figures.

And theres no point comparing it to a stock engine, bcoz diff engines age differently. If you want to see what this engine does in stock form, you'l have to fit the stock intake/exhaust and do back to back tests.

Shan2nu

Adding to that, its how the Engine & car is serviced at regular interval, time to time, like changing oil (engine & gearbox) sparkplugs,filters etc.. etc.. & at later stage going to Fully Synthetic Mobil 1 in this case, are the factors contributing to such wonderful results. If this car was not maintained as it should be the results might not be the same.

[SirAlec]

Just for the information. inertia dynos are never accurate and can deviate garvely from real world figures that a particular vehicle is producing.

Inertia Sweep: An inertia dyno system that provides a fixed inertial mass flywheel and computes the power required to accelerate the flywheel (load) from the starting to the ending rpm. The actual rotational mass of the engine or engine and vehicle in the case of a chassis dyno is not known and the variability of even tire mass will skew power results. The inertia value of the flywheel is "fixed", so low power engines are under load for a much longer time and internal engine temperatures are usually too high by the end of the test, skewing optimal "dyno" tuning settings away from the outside world's optimal tuning settings. Conversely, high powered engines, commonly complete a common "4th gear sweep" test in less than 10 seconds, which is not a reliable load condition as compared to operation in the outside world. By not providing enough time under load, internal combustion chamber temps are unrealistically low and power readings, especially past the power peak, are skewed low.

[Sutripta]

Originally Posted by CPH

The rise was constant. I have to dig out the graphs, because the figures were taken from a thread I made some time ago. It actually wasn't a sudden rise. The rolling road has got roughly about 800 reference points throughout the rpm range. I just took some to give an indication (otherwise I would sit typing it all month).

6000 - 6500 (500 rpm diff) - 3%
6500 - 6750 (250 rpm diff) - 5%
If linearly extrapolated to 500 rpm, - 10%.
Cause for head scratching, I'd say!

As I said above. Giving ball park figures would not be accurate and I am not going to mislead you.

Ballpark figures are just that:- ballpark figures. No one is going to be "mislead" by those. Amongst other things, it helps people get a feel of things, do back of envelope calculations.

The variations between the different gear box oils can be in excess of 5% in drivew train losses. Even with a set box you can have massive differences depending on the wear rate. And a big difference will the location make. Where I used to live we had on extreme summer days up to 55 degress Celsius and the lowest I experienced there was -43 degress Celsius. A starer motor is working hard to turn the engine over with often a much thinner oil and a battery that is kept in the house overnight to be warm enough to give power.

The gear oil might not be far from solid and will possibly on a short run not get warm enough to get to operating temp.

From a cold to a warm gear box oil we measured a total drive train loss of up to 3% difference on a day you Southerners would consider warm to hot.

For any quantitative figure to be meaningful and comparable, it has to be reproducible. By anyone. Thats why the circumstances under which it was obtained has to be clearly spelled out. And to make it easy to compare, we have the concept of Standard Test Conditions. It is essentially an attempt (though not always successful) to remove these variations.


Actually rather than getting lost in minutiae, it would be educative for us if you told us
a) How you do your measurements, esp the coast down,
b) And what are the ballpark figures bandied about in the trade.

In your opinion and experience, which was the best and worst (in terms of efficiency) manual layshaft production gearbox (no spur gears!) you have come across? And rear diffs.

Regards
Sutripta

[CPH]

Sutripta, you don't know what you are doing to me.

It will take some time to get all the data together. So bear with me.