Reducing parasitic loss in the transmission

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Reducing parasitic loss in the transmission

Post by Velocity_Dan93 » Mon Jan 23, 2017 8:14 pm

Being as the car is away at rotary revs having a tasty rebuild I find myself having a lot more free time which was spent on cleaning and collecting shell v power points.
As I'm aiming for high figures ( the 200 who mark) I started reading into why the rx8 does so s&*t on the dyno. I've been reading lots of things about comparing it to the s2000 and while it's obviously a little bit quicker, not by as much as the low dyno results would show.
So where the hell is all the power going ?
3 main answers cropped up
1. Mazda are liars ! ( believable to an extent )
2. The rx8 enters a low power mode when on the dyno because it can tell the front wheel's are stationary and runs rich to prevent over heating
3. Paracitic transmission loss
I think the answer is a mix of all 3 but mainly the last 2 which got me looking into ways of reducing this loss. I'm already adding in an underdrive pulley kit, light weight flywheel, and pettit flywheel nut.
All these thing is a way WILL increase my whp as it will reduce the amount of power that the transmission eats up. When people talk about a paracitic transmission loss they give X% or Y% but it can't simply be a %. Compared to a standard engine say 100 bhp the loss is 15% so 15 bhp . However is you managed to increase the engine output to 200 bhp you wouldn't get a 15% loss and it's only reflective of the origional amount, you still only loose that 15bhp . By increasing the power and reducing the transmission loss you are eating away at this magical mystery figure from both sides. The only way to figure it out exactly is to have the engine on a dyno and then a chassis dyno and work out the difference.
So what other ways are there to reduce the paracitic loss of the transmission?
Not much, the bits I've already done are probably the easiest and cheapest things to do, however there are other thing's to consider.
1. The diff/lsd would a different one make a difference
2. Transmission fluids, a less viscous oil would reduce loss but only slightly
3. Cv joints
4. Wheels
5. Floating rotors on the rear
6. Gearbox
From what I can tell the floating rear disks are the cheapest option (£1300 k sport rear kit)
From there you are looking at about £8k for a set of full carbon fibre wheels at 11lb per wheel and God knows what on custom setups for the CV shafts.
The diff/ lsd is an interesting one as im not sure how you would measure how they would reduce or increase the losses. Obviously the R3 diff aids acceleration but not in this way. As far as I can tell no one has gone down the route of a custom cv setup. Alternativley get some boost and be done with it :P
Last edited by Velocity_Dan93 on Tue Jan 24, 2017 5:35 pm, edited 1 time in total.
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Re: Reducing paracitic loss in the transmission

Post by ChrisHolmes » Mon Jan 23, 2017 9:20 pm

Velocity_Dan93 wrote:Being as the car is away at rotary revs having a tasty rebuild I find myself having a lot more free time which was spent on cleaning and collecting shell v power points.
As I'm aiming for high figures ( the 200 who mark) I started reading into why the rx8 does so s&*t on the dyno. I've been reading lots of things about comparing it to the s2000 and while it's obviously a little bit quicker, not by as much as the low dyno results would show.
So where the hell is all the power going ?
3 main answers cropped up
1. Mazda are liars ! ( believable to an extent ) Possibly
2. The rx8 enters a low power mode when on the dyno because it can tell the front wheel's are stationary and runs rich to prevent over heating Wouldn't all cars do this?
3. Paracitic transmission loss The main cupltir
I think the answer is a mix of all 3 but mainly the last 2 which got me looking into ways of reducing this loss. I'm already adding in an underdrive pulley kit, light weight flywheel, and pettit flywheel nut.
All these thing is a way WILL increase my whp as it will reduce the amount of power that the transmission eats up. When people talk about a paracitic transmission loss they give X% or Y% but it can't simply be a %. Compared to a standard engine say 100 bhp the loss is 15% so 15 bhp . However is you managed to increase the engine output to 200 bhp you wouldn't get a 15% loss and it's only reflective of the origional amount, you still only loose that 15bhp Logical. By increasing the power and reducing the transmission loss you are eating away at this magical mystery figure from both sides. The only way to figure it out exactly is to have the engine on a dyno and then a chassis dyno and work out the difference.
So what other ways are there to reduce the paracitic loss of the transmission?
Not much, the bits I've already done are probably the easiest and cheapest things to do, however there are other thing's to consider.
1. The diff/lsd would a different one make a difference
2. Transmission fluids, a less viscous oil would reduce loss but only slightly
3. Cv joints
4. Wheels
5. Floating rotors on the rear
6. Gearbox straight cut gear may reduce the power loss but would be noisier
From what I can tell the floating rear disks are the cheapest option (£1300 k sport rear kit)
From there you are looking at about £8k for a set of full carbon fibre wheels at 11lb per wheel and God knows what on custom setups for the CV shafts.
The diff/ lsd is an interesting one as im not sure how you would measure how they would reduce or increase the losses. Obviously the R3 diff aids acceleration but not in this way. As far as I can tell no one has gone down the route of a custom cv setup. Alternativley get some boost and be done with it :P
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Re: Reducing paracitic loss in the transmission

Post by Sonic KaBoomii » Mon Jan 23, 2017 9:23 pm

Momentum isn't power loss. Flywheels, lightweight wheels, floating discs all (may) help acceleration, but they're not releasing any more power ...not that you could measure on a dyno anyway
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Re: Reducing paracitic loss in the transmission

Post by Rotary Potato » Mon Jan 23, 2017 9:28 pm

I'm not an engineer (i got thrown out of university many years ago while trying to become one). However, I'm not certain about your % vs actual number for transmission losses.

If you transmit more torque through a system, it stands to reason that the added torque would load up the system, causing more parasitic losses. At least in my head ...
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Re: Reducing paracitic loss in the transmission

Post by Velocity_Dan93 » Mon Jan 23, 2017 9:41 pm

Sonic KaBoomii wrote:Momentum isn't power loss. Flywheels, lightweight wheels, floating discs all (may) help acceleration, but they're not releasing any more power ...not that you could measure on a dyno anyway

I think you could measure it on a dyno, there are lots of examples mainly in the Honda world which show an increase. Everything the engine is attached to requires energy to move, less mass, weight or inertia required to move it the more power can tansmit through it and obviously quicker as you said with the increased acelaration. Granted we are talking about a small amounts of power. Many companies claim underdrive pulleys incase bhp ( granted 2-3 ) with lots of dyno charts. Doesn't a light weight flywheel work the same way ?
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Re: Reducing paracitic loss in the transmission

Post by Sonic KaBoomii » Mon Jan 23, 2017 9:47 pm

No. An underdrive pulley reduces the load on the engine by turning the ancillaries slower, a flywheel is directly connected to the engine so always turns at the same speed
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Re: Reducing paracitic loss in the transmission

Post by ChrisHolmes » Mon Jan 23, 2017 9:50 pm

A lighter flywheel uses less power to spin up thus it fractionally increases performance.
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Re: Reducing paracitic loss in the transmission

Post by Conan » Mon Jan 23, 2017 9:51 pm

But it takes less effort to turn it
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Re: Reducing paracitic loss in the transmission

Post by ChrisHolmes » Mon Jan 23, 2017 9:54 pm

Note the 4th, 5th and 6th words Pete
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Re: Reducing paracitic loss in the transmission

Post by Rotary Potato » Mon Jan 23, 2017 9:57 pm

Sonic KaBoomii wrote:Momentum isn't power loss. Flywheels, lightweight wheels, floating discs all (may) help acceleration, but they're not releasing any more power ...not that you could measure on a dyno anyway
Is it possible that you're confusing a flywheel figure with a at the wheels figure?

To get a 'flywheel' figure with the engine still in the car, the dyno tries to measure the transmission losses on the rundown, and subtracts these from the wheel figure (which it can accurately measure) to estimate a flywheel figure.

I understand that if done right by an experienced rolling road operator a flywheel figure can be pretty accurate.

In the above examples, the transmission masses all take power to spin up and keep spinning, so reducing that mass/friction would increase (measurably on a dyno) wheel power but not flywheel power.
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Re: Reducing paracitic loss in the transmission

Post by Sonic KaBoomii » Mon Jan 23, 2017 10:04 pm

Rotary Potato wrote: Is it possible that you're confusing a flywheel figure with a at the wheels figure?
I don't think so.

I don't pretend to be an expert on the subject, but transmission loss is exactly that; power lost turning the gearbox cogs through oil, flexing rubber CV boots etc

You'll always make peak power at the same revs, and reducing the time it takes to get there doesn't increase the power
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Re: Reducing paracitic loss in the transmission

Post by Rotary Potato » Mon Jan 23, 2017 10:12 pm

Sonic KaBoomii wrote:
Rotary Potato wrote: Is it possible that you're confusing a flywheel figure with a at the wheels figure?
I don't think so.

I don't pretend to be an expert on subject, but transmission loss is exactly that; power lost turning the gearbox cogs through oil, flexing rubber CV boots etc

You'll always make peak power at the same revs, and reducing the time it takes to get there doesn't increase the power
Ditto ... i'm no expert either.

However, look at it this way.

Take a scaletric car motor. If you put a current through it, it spins up, and has a power you can measure.

If you attach a brake disc (or any very heavy lump) to the motor, when you pass a current through it, nothing happens apart from a bit of a smell. Does this motor now have zero power, or have the transmission losses absorbed all the power the motor produces?

I've taken a highly exagerated example to try and show my thinking.
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Re: Reducing paracitic loss in the transmission

Post by Velocity_Dan93 » Mon Jan 23, 2017 10:16 pm

Just to be clear I am talking about WHP being increased not BHP. I'm not an expert either but after a lot of reading I do think it reduces the losses by reducing the power needed to move stuff. I think redline who make diff and transmission oils say they give a 1-2 whp increase in some application's too. The more you look the more people ( and companies ) say it's possible. But when you're looking for that 0.1 bhp, 1-2 bhp is all you want really and I'd be kicking myself if I didn't look at every avenue to make the most out of the power available
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Re: Reducing paracitic loss in the transmission

Post by Sonic KaBoomii » Mon Jan 23, 2017 10:21 pm

Oil - absolutely; reduce friction, free up power
Anything where there's no friction involved - definitely not
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Re: Reducing paracitic loss in the transmission

Post by warpc0il » Mon Jan 23, 2017 10:29 pm

For maximum power on the dyno, pump the tyres up to 50 psi.

It doesn't help on the road but dynos are mainly a pi$$ing competition...
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Re: Reducing paracitic loss in the transmission

Post by Velocity_Dan93 » Mon Jan 23, 2017 10:33 pm

Surely that again is the same thing, less friction requires less energy to move it ? I'm not trying to be an argumentative tw@£ I promise :P
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Re: Reducing paracitic loss in the transmission

Post by ChrisHolmes » Mon Jan 23, 2017 11:42 pm

That's not reduced friction with high tyre pressures, it's reduced rolling resistance. This would a great discussion over a few beers I am sure.
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Re: Reducing paracitic loss in the transmission

Post by PeteH » Mon Jan 23, 2017 11:49 pm

In bhp the "b" stands for brake. Power (real proper engineering power) is measured by a device that applies a brake to hold the engine at fixed revs while at full throttle. In this condition the inertias in the drive train are eliminated because there is no acceleration. So lightweight (or, more properly, low inertia) flywheels, nuts, drives shafts, wheels, etc, will have no effect at all on the true measured bhp figure.

One of the problems with chassis dyno, rear wheel dyno, and rolling roads, is that they sweep the car from low revs to high revs. The power train accelerates, so it measures both the engine bhp and the inertia of the driveline (and the losses). Some dyno operators use a rough factor to "correct" this. Some do a run down test to try to measure the other factors. Any method is imperfect. Hence Warpc0il's comment about pi##ing contests.

At least Ben at RR uses the same method for all cars, so all runs are comparable (I think).

By the way, reducing inertial will allow the car to accelerate more quickly, but not because there is more power. Reducing inertia is more equivalent to reducing car mass.

And regarding oil viscosity. Lower viscosity will have slightly lower churning and shearing losses, but may increase friction, and may substantially increase wear. You have no way of knowing which factor is going to dominate. Are you sure you want to experiment?

The most effective way of reducing losses would be to fit low rolling resistance tyres (and/or higher pressures as mentioned above). You will go fractionally faster in a straight line, and substantially slower around corners.

If you get 200 rwhp at Ben's then I'd just be happy with having one of the most powerful NA cars around. :thumright:
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Re: Reducing paracitic loss in the transmission

Post by Dr. FrankenRex » Tue Jan 24, 2017 9:22 am

My main question is what is this all in the pursuit of?

A number on a piece of paper, or a car which goes really fast? If it's the latter you're much better off ploughing that kind of money in to track-day tutoring. If it's the former, then I agree with Warpc0il - do everything you can to skew the figures in your favour, doesn't prove too much.

A couple of extra whp will make your car's potential increase, a couple of hours with a decent instructor will make your car's realised potential much higher - usually for much less money, too! :thumleft:
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Re: Reducing paracitic loss in the transmission

Post by Conan » Tue Jan 24, 2017 10:53 am

ChrisHolmes wrote:That's not reduced friction with high tyre pressures, it's reduced rolling resistance. This would a great discussion over a few beers I am sure.
Perhaps we,ve had a few beers already :)
I thought friction was resistance
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Re: Reducing paracitic loss in the transmission

Post by Ainmhidh » Tue Jan 24, 2017 11:18 am

Friction could be considered resistance, but not all resistance is friction? Rolling resistance is e.g. deformation of tyres - high pressure means less deformation = less rolling resistance. The only friction affected is the contact patch between tyre and 'road' surface, which will have a reduced area at higher pressures (due to less deformation of the tyre) so same coefficient of friction, but over a smaller area so less 'grip'. Nothing to actually affect the power reaching the wheel though. (disclaimer: not quite an engineer!)
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Re: Reducing paracitic loss in the transmission

Post by Conan » Tue Jan 24, 2017 11:34 am

I believe friction is the resistance between two materials.
What material it is or how hard it,s pumped up is immaterial, that merely changes the measurable amount of friction/resistance.
I,m not an engineer either ;)
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Re: Reducing paracitic loss in the transmission

Post by ChrisHolmes » Tue Jan 24, 2017 12:08 pm

Conan wrote:
ChrisHolmes wrote:That's not reduced friction with high tyre pressures, it's reduced rolling resistance. This would a great discussion over a few beers I am sure.
Perhaps we,ve had a few beers already :) Certainly not me Pete, you?
I thought friction was resistance


Friction is a resistance to movement so your correct in that, but rolling resistance is not friction, it is created by the deformation of the tyre tread from curved to flat as it meets the road surface. In the tyre world static friction can be simply defined as the grip a tyre has. If that friction is overcome by an external force, braking, accelerating or turning then you have sliding friction which is less than static friction and hence your skidding.

Edited: wrote and posted this before I read the one from Aidmhidh, scarily similar wording!
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Re: Reducing paracitic loss in the transmission

Post by ChrisHolmes » Tue Jan 24, 2017 12:25 pm

Conan wrote:I believe friction is the resistance between two materials. Correct
What material it is or how hard it,s pumped up is immaterial, that merely changes the measurable amount of friction/resistance. Also correct except for saying its immaterial because the higher pressure tyre will have less deformation and therefore a lower rolling resistance and of course it will have less static friction because the road contact area will have been reduced
I,m not an engineer either ;)
Neither am I

Let us go back to when they built the pyramids to perhaps help you understand what us being said.

Take one large block of stone lying on a smooth rock surface.
Attach one end of a rope to the block and the other to an elephant and say PULL, nothing moves.
Keep adding elephants until the block moves, let's say it moves at 3 elephants therefore that's the static friction force
Once moving release one of the elephants and the block keeps moving, that is the sliding friction force.
Give the elephants a rest and a drink of water whilst you lift the block onto several rollers.
Pick any single elephant at random and attach the rope to it and say pull, the block rolls on the rollers because the static and sliding friction have been removed.
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Conan
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Re: Reducing paracitic loss in the transmission

Post by Conan » Tue Jan 24, 2017 12:55 pm

Conan wrote:
ChrisHolmes wrote:That's not reduced friction with high tyre pressures, it's reduced rolling resistance. This would a great discussion over a few beers I am sure.
Perhaps we,ve had a few beers already :)
I thought friction was resistance
Try pissing up the wall a bit higher Chris
I just wasted 5 minutes googling this (can,t remember the last time I did that)
Rolling friction
Rolling resistance
Rolling drag
These are all the same in this instance
Coefficient of rolling friction or CRF is W=mag

The reference to tyres friction/resistance /drag is totaly irrelevant as that isn't the question the OP asked.
It was an excellent laymans example of friction / resistance / drag by Warpcoil though.
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