Drivetrain losses
Discussion
There is no argument that using rollers for tuning can be a good thing. Using rollers for comparison is a totally different thing though.
Stevie, I reckon your 1000+ horsepower LS3 would struggle to grip on any rollers
We tend to tune more humble carbed and distributered cars which respond well to rolling roading and have won us numerous championships every year since 1987.
I attach a pic of a TR4 we tuned today. It took three hours start to finish, this would take a lot of track test time to sort and would need a driver with a sensitive bum to tease out all the power.
Lowest power line as it came in way too rich, second lowest power line air filters removed.
Third lowest power line chokes bored out from 36 to 38mm and fuelling optimised.It took four runs to optimise air correctors in stages taking them from 170 down to 150.
Highest power line optimise ignition timing for track, it would have been nice to alter the advance curve to suit the lower rpm as well but the engine runs over 4000 on the track.
Peter
Stevie, I reckon your 1000+ horsepower LS3 would struggle to grip on any rollers
We tend to tune more humble carbed and distributered cars which respond well to rolling roading and have won us numerous championships every year since 1987.
I attach a pic of a TR4 we tuned today. It took three hours start to finish, this would take a lot of track test time to sort and would need a driver with a sensitive bum to tease out all the power.
Lowest power line as it came in way too rich, second lowest power line air filters removed.
Third lowest power line chokes bored out from 36 to 38mm and fuelling optimised.It took four runs to optimise air correctors in stages taking them from 170 down to 150.
Highest power line optimise ignition timing for track, it would have been nice to alter the advance curve to suit the lower rpm as well but the engine runs over 4000 on the track.
Peter
PeterBurgess said:
There is no argument that using rollers for tuning can be a good thing. Using rollers for comparison is a totally different thing though.
Stevie, I reckon your 1000+ horsepower LS3 would struggle to grip on any rollers
We tend to tune more humble carbed and distributered cars which respond well to rolling roading and have won us numerous championships every year since 1987.
I attach a pic of a TR4 we tuned today. It took three hours start to finish, this would take a lot of track test time to sort and would need a driver with a sensitive bum to tease out all the power.
Lowest power line as it came in way too rich, second lowest power line air filters removed.
Third lowest power line chokes bored out from 36 to 38mm and fuelling optimised.It took four runs to optimise air correctors in stages taking them from 170 down to 150.
Highest power line optimise ignition timing for track, it would have been nice to alter the advance curve to suit the lower rpm as well but the engine runs over 4000 on the track.
Peter
Except I dont know how much power mine has Stevie, I reckon your 1000+ horsepower LS3 would struggle to grip on any rollers
We tend to tune more humble carbed and distributered cars which respond well to rolling roading and have won us numerous championships every year since 1987.
I attach a pic of a TR4 we tuned today. It took three hours start to finish, this would take a lot of track test time to sort and would need a driver with a sensitive bum to tease out all the power.
Lowest power line as it came in way too rich, second lowest power line air filters removed.
Third lowest power line chokes bored out from 36 to 38mm and fuelling optimised.It took four runs to optimise air correctors in stages taking them from 170 down to 150.
Highest power line optimise ignition timing for track, it would have been nice to alter the advance curve to suit the lower rpm as well but the engine runs over 4000 on the track.
Peter
as I dont often go near a dyno. I think last time was 4-5 years ago and barely anything is the same nowThe times I have used a dyno both DD and Dynapack on very separate occasions, the differences were massive. The Dynapack was more like some US numbers, the DD perhaps more realistic.
But you're backing up exactly my opinion. You're using it for tuning, you're seeing gains and losses in a real time tuning scenario.
Not making comparisons days, weeks, years apart, different weather, fuel, tyres etc etc
Been thinking Dave, I cannot see in any way how your rule of thumb makes any allowance for what may be the most important, in terms of value, parasitic losses in the drivetrain. They are the speed of tyre and the actual tyre. We all know the tyre losses are exponential with speed, we also know a tyre as wide as a bicycle one will not take as much to turn as a 30+cm wide race tyre. The compound and tread pattern also makes a difference, how does your rule of thumb take into account the different speeds and tyres? We have measured with our coastdown testing how rally tyres take more bhp to turn than road tyres so your rule of thumb would not obtain. Likewise if we test with pressures lower or higher we record different wp, how does your rule encompass this? I can see your percentage system might work with hub dynos if you were to have a different allowance for live or dead axles and associated ujs etc you wouldn't have to worry about tyre speed and type then. We all know a car shows more wp in third gear than direct top as, even though the non direct gear will lose more power than the direct 1:1 top gear the tyre speed will sap more power in direct top.
Peter
Peter
A rule of thumb or estimation by definition does not consider every single effect.
presumably if you were doing a comparison you would use the same tyres and wheels, same strap down technique, same tyre pressures and same gearing etc to minimise the influence of other variables
it should be noted that tyre hp losses do go up with higher gear due to higher speed but the force between the tyres and roller (tractive effort) reduces so the effect is not as pronounced as many would have you believe IMO.
last time i did a run in 3rd vs 4th the difference was 2.5% in output power when speed was 40% higher, you can easily get this kind of variance doing runs back to back in the same gear. nevertheless its not difficult to do power runs in same gear purely for comparative purposes
presumably if you were doing a comparison you would use the same tyres and wheels, same strap down technique, same tyre pressures and same gearing etc to minimise the influence of other variables
it should be noted that tyre hp losses do go up with higher gear due to higher speed but the force between the tyres and roller (tractive effort) reduces so the effect is not as pronounced as many would have you believe IMO.
last time i did a run in 3rd vs 4th the difference was 2.5% in output power when speed was 40% higher, you can easily get this kind of variance doing runs back to back in the same gear. nevertheless its not difficult to do power runs in same gear purely for comparative purposes
Interesting you say about variation between runs, is that an inertia rolling road? I find if I do four or five runs then take the reading each time I get consistent figures time after time, I understand this consistency is why race teams favour the inertia dyno over pau. We were told by our Silkolene contact how they could detect fractions different with different oils and tried to get the best possible, we tried this with my mate's (The Silver Fox) Harley and obtained a 1 bhp on 76 improvement with posh gearbox oil over cheapie oil. The coastdown tests, whatever they allude to, shows these improvements in measured losses as well, so if we go up one wp bhp by changing gear box oil we go down one bhp in measured losses.
When I said earlier about taking time for tuning, that is what I meant, no rushing to get spot readings, let things cool and try and keep things consistent. The software and hardware measures temp pressure and humidity and corrects the runs. The module may not be scientific measurement but it correlates with our flow bench temp pressure and humidity readings. Not same readings but always same relationship.
Peter
When I said earlier about taking time for tuning, that is what I meant, no rushing to get spot readings, let things cool and try and keep things consistent. The software and hardware measures temp pressure and humidity and corrects the runs. The module may not be scientific measurement but it correlates with our flow bench temp pressure and humidity readings. Not same readings but always same relationship.
Peter
Interestingly, even on a hub dyno
I recall one car in the US on a Dynapack, because it overloaded the torque rating in 4th, they had to dyno it in 5th gear.
( Actually had that myself first time on a Dynapack )
But on the tests they did, using 5th gear results were around 15% lower than when they had tested in 4th gear. Which sounds like a shocking amount ?
I recall one car in the US on a Dynapack, because it overloaded the torque rating in 4th, they had to dyno it in 5th gear.
( Actually had that myself first time on a Dynapack )
But on the tests they did, using 5th gear results were around 15% lower than when they had tested in 4th gear. Which sounds like a shocking amount ?
Pumaracing said:
Ok I'm now thinking you might be feeding us bum information. Looking at your previous posts and other stuff on the net your rolling road figures will already have been converted to estimated flywheel numbers and won't be wheel bhp. So I'm now thinking you have an estimated 700 bhp flywheel bhp not wheel bhp which will probably be in the low 600s.
So a hub dyno figure would be mid 600s bhp.
No im not feeding you bum information, your missreading what I have said So a hub dyno figure would be mid 600s bhp.
In the states they have a car they claim 900bhp flywheel, and said it was 700hp at wheels... thus 200bhp losses hence my confusion as its the same engine and box with same mods to box and drivetrain.
for clarification my car made 575 wheel HP in an old guise which was estimated as 626bhp at the fly at the time.... I then had it pushed a little further with new engine mods, it 'felt' a lot faster on pure wastegate pressure than the previous guise... when it was dyno'd this showed it had increased 60bhp on low boost, which matched what it felt to drive.
High boost this iteration made 595hp (i think) at the wheels and 700bhp estimated flywheel... it felt and was a lot faster than the 626bhp iteration.
Ive now had it on a hub dyno and it made mid 600bhp at hubs... no estimation of flywheel was made but it is running more boost than before and is faster any thus is more powerful.
So Im not unhappy or worried about the cars performance... I just cant believe how vastly different peoples claims for transmission losses... Personally I cant see how the drivetrain losses can be over 100bhp... I also don't beleive a wheel and tyre could loose over 30bhp (well not my ones)... that's a HUGE amount of heat or noise to dissipate and they would simply melt and or explode as thats over 22kw and is lot of electric fires of energy lol
Edited by andygtt on Wednesday 1st October 12:27
stevieturbo said:
Whether it's your fancy or not...
1/4 mile traps, 1/2 mile traps etc are far better and more reliable indicators of actual power to the ground.
Dyno's just vary too much to try and make comparisons elsewhere.
And trying to compare with US dyno's....is even more difficult. Everything is bigger over there !
Or if standing starts arent great. Some of the 30-130 or 60-130 type pulls are also a good indicator of power and can be far more reliable measured across continents ( unless you're running downhill with a massive tailwind )
I don't have telemetry from 60-130mph (unless I stick bits of telemetry together)... but I do have 70-140mph of 5.3 seconds or 70-130mph 4.6 seconds with 2 people in the car... so 1030kgs plus driver 95kgs and passenger 90kgs... so 1215kgs... I don't have 1/4 mile times or anything yet.1/4 mile traps, 1/2 mile traps etc are far better and more reliable indicators of actual power to the ground.
Dyno's just vary too much to try and make comparisons elsewhere.
And trying to compare with US dyno's....is even more difficult. Everything is bigger over there !
Or if standing starts arent great. Some of the 30-130 or 60-130 type pulls are also a good indicator of power and can be far more reliable measured across continents ( unless you're running downhill with a massive tailwind )
Wont be anything like as fast as your monster/car though lol
That's the point made in the post I referenced earlier. There is a whole lot of BS talked about drive train losses. If you weigh a gearbox and/or diff and calculate the approximate temperature rise based on the specific heat capacity of the steel, aluminium and oil when it supposedly dissipating 100HP (75KW!!) it would be molten and destroyed, glowing and dribbling around on the dyno cell floor within not many seconds of a power run. These losses are patently b
ks, it's a simple matter of physics. And as for tyres dissipating tens of KW, come on, they would be well alight in seconds whether moving through free air or on a rolling road.
ks, it's a simple matter of physics. And as for tyres dissipating tens of KW, come on, they would be well alight in seconds whether moving through free air or on a rolling road.andygtt said:
I don't have telemetry from 60-130mph (unless I stick bits of telemetry together)... but I do have 70-140mph of 5.3 seconds or 70-130mph 4.6 seconds with 2 people in the car... so 1030kgs plus driver 95kgs and passenger 90kgs... so 1215kgs... I don't have 1/4 mile times or anything yet.
Wont be anything like as fast as your monster/car though lol
I think a lot is lost through the tyres....mine go up in smoke easily lol.Wont be anything like as fast as your monster/car though lol
Log everything and all the time, the data is handy to have. Then you can get time stats whenever you want ( better if speed is via undriven wheels or GPS obviously )
It also gives yourself good reference points as to performance getting better or worse.
fatjon said:
That's the point made in the post I referenced earlier. There is a whole lot of BS talked about drive train losses. If you weigh a gearbox and/or diff and calculate the approximate temperature rise based on the specific heat capacity of the steel, aluminium and oil when it supposedly dissipating 100HP (75KW!!) it would be molten and destroyed, glowing and dribbling around on the dyno cell floor within not many seconds of a power run. These losses are patently bks, it's a simple matter of physics. And as for tyres dissipating tens of KW, come on, they would be well alight in seconds whether moving through free air or on a rolling road.
Not really no.ks, it's a simple matter of physics. And as for tyres dissipating tens of KW, come on, they would be well alight in seconds whether moving through free air or on a rolling road.Take a typical gearbox and rear diff, made of aluminium and steel, weighing around 70kg, put 100bhp into it for say 30sec, and if somehow it didn't loose ANY heat to it's surroundings, it would only go up in temp by about 53.5degC. Hardly "molten and destroyed"......
OK, talk of "200 bhp" lost in the drive train is bolleux, but in reality, a LOT of power is lost into the powertrain of your car and it's tyres.
I have sent an email to Michelin asking for power absorption at 60 and 90 mph of the Latitude Cross tyres I run on my Jeep Cherokee TD. I power tested the Cherokee on my rollers after 500 miles and got max wp 108.7 @ 3100 and max torque of 220.7 lbsft at 2400 (narrow power band eh?) power losses 22.2 bhp If I get a reply I will post it on this thread to share the info.
Peter
Peter
Edited by PeterBurgess on Wednesday 1st October 18:46
PeterBurgess said:
I have sent an email to Michelin asking for power absorption at 60 and 90 mph of the Latitude Cross tyres I run on my Jeep Cherokee TD. I power tested the Cherokee on my rollers after 500 miles and got max wp 108.7 @ 3100 and max torque of 220.7 lbsft at 2400 (narrow power band eh?) power losses 22.2 bhp If I get a reply I will post it on this thread to share the info.
Peter
You'd have to have told them the axle mass, the suspension geometry settings, what rollers you are using (dual/single & roller diameter etc) the tyre carcase temperature, inflation pressure and tread depth too!Peter
Edited by PeterBurgess on Wednesday 1st October 18:46
So far I just had the...automated response bit
I told them make and model of vehicle, tyre pressures and tyres were 500 miles old when tested. I asked for their idea of power absorption on 'normal' tarmac at 60 and 90 mph. I assume they will have enough info to hand re the Cherokee weights. I will ask em about any extra roller losses if they get back to me. Oddly enough one of my customers was involved in the development of the assymetric latitude cross tyres I am running.
A Peerless we tuned was run on a single roller Dynocom as well and recorded same power curve and losses as our twin roller one, I thought maybe the twin roller would show slightly more losses, but such is life
Peter
I told them make and model of vehicle, tyre pressures and tyres were 500 miles old when tested. I asked for their idea of power absorption on 'normal' tarmac at 60 and 90 mph. I assume they will have enough info to hand re the Cherokee weights. I will ask em about any extra roller losses if they get back to me. Oddly enough one of my customers was involved in the development of the assymetric latitude cross tyres I am running.
A Peerless we tuned was run on a single roller Dynocom as well and recorded same power curve and losses as our twin roller one, I thought maybe the twin roller would show slightly more losses, but such is life
Peter
Max_Torque said:
Not really no.
Take a typical gearbox and rear diff, made of aluminium and steel, weighing around 70kg, put 100bhp into it for say 30sec, and if somehow it didn't loose ANY heat to it's surroundings, it would only go up in temp by about 53.5degC. Hardly "molten and destroyed"......
OK, talk of "200 bhp" lost in the drive train is bolleux, but in reality, a LOT of power is lost into the powertrain of your car and it's tyres.
thats why its not a good idea to hold a car on the chassis dyno that long under WOT when operating in the powerband, in the real world the airflow helps keeps things in check. on the dyno the airflow is never the sameTake a typical gearbox and rear diff, made of aluminium and steel, weighing around 70kg, put 100bhp into it for say 30sec, and if somehow it didn't loose ANY heat to it's surroundings, it would only go up in temp by about 53.5degC. Hardly "molten and destroyed"......
OK, talk of "200 bhp" lost in the drive train is bolleux, but in reality, a LOT of power is lost into the powertrain of your car and it's tyres.
Where the x + % came from if I recall correctly.
Back in 1987-1990 when you visited a lot Dave and we worked together on the rollers we were always trying to find a way of working out flywheel power from wp. We worked out a straight percentage is no good so originally I ended up with 12 bhp for a pair of tyres (6 on a motorbike with single tyre) add to wp then multiply by 1.10 to add the 10 percent guessed losses from rest of transmission. Most of the cars we dealt with were 60-125 at the wheels and the figures didnt seem too bad comparing wp to flywheel from what folk claimed. EG MGB standard 65 at wheels on Clayton +12 gives 77 x 1.1 gives 84.7 (84 manufacturers figure). Modded B 100 at wheels + 12 = 112 x 1.1 gives 123. Dynocom 62 std B and 22 losses = 84 at engine. Modded B 100 at wheels 22 losses = 122 close to guesstimates we used to do. Mini 55 at wheels +12 =67 x 1.1 = 73.7 old way, Dynocom 55 at wheels + 14.5 losses = 69.5 beginning to show discrepancy. V8 MGB with 328 at wheels, old way 328 +12 x 1.1 = 374, dynocom 328 +22 = 350 error increasing with old way. In essence we were trying to make numbers match so we were happy with them, 24 years on and I see things differently.
On a separate note with regard to horsepower lost in transmission, the 14 mm fanbelt that drives the cooling fan on a VW aircooled; take it off and wp goes up on the one we tested from 78 to 85 so the belt was transmitting 7 bhp via friction of pulleys, no sign of overheating belt or pulleys, the heat dissipates.
Hopefully get a reply from Michelin soon.
Peter
Back in 1987-1990 when you visited a lot Dave and we worked together on the rollers we were always trying to find a way of working out flywheel power from wp. We worked out a straight percentage is no good so originally I ended up with 12 bhp for a pair of tyres (6 on a motorbike with single tyre) add to wp then multiply by 1.10 to add the 10 percent guessed losses from rest of transmission. Most of the cars we dealt with were 60-125 at the wheels and the figures didnt seem too bad comparing wp to flywheel from what folk claimed. EG MGB standard 65 at wheels on Clayton +12 gives 77 x 1.1 gives 84.7 (84 manufacturers figure). Modded B 100 at wheels + 12 = 112 x 1.1 gives 123. Dynocom 62 std B and 22 losses = 84 at engine. Modded B 100 at wheels 22 losses = 122 close to guesstimates we used to do. Mini 55 at wheels +12 =67 x 1.1 = 73.7 old way, Dynocom 55 at wheels + 14.5 losses = 69.5 beginning to show discrepancy. V8 MGB with 328 at wheels, old way 328 +12 x 1.1 = 374, dynocom 328 +22 = 350 error increasing with old way. In essence we were trying to make numbers match so we were happy with them, 24 years on and I see things differently.
On a separate note with regard to horsepower lost in transmission, the 14 mm fanbelt that drives the cooling fan on a VW aircooled; take it off and wp goes up on the one we tested from 78 to 85 so the belt was transmitting 7 bhp via friction of pulleys, no sign of overheating belt or pulleys, the heat dissipates.
Hopefully get a reply from Michelin soon.
Peter
Reply from Michelin....tells us nothing new 
My thoughts are in Capital Letters in brackets.
Peter,
I can't directly tell you you will lose "X" bhp, as it's not quite as straight forward as that.
Our figures suggest a 20% energy loss from the system in purely overcoming rolling resistance of the tyre. (ALL FOUR TYRES TAKE 20%?)
But again, energy losses from drive train, component friction and drag (WIND RESISTANCE IS A FUNCTION OF CUBE OF SPEED) will probably account for more single losses
Tyres absorb energy primarily through hysteresis of the compound and carcass.
Therefore a tyre running at it's optimum pressure will absorb less than an under-inflated tyre, producing much more heat as it flexes and rolls.
The remaining tread depth and condition of the rubber itself will also influence what heat is generated.
Rolling roads are particularly bad for tyres, as they tend to build heat up in the compound very rapidly as their surface heats the tyre much more than a normal road.
The metallic drum also has a higher heat potential making the tyre/drum contact quite different to what we see on the road. It is not uncommon to blister a tyre on a rolling road (WHEN HOLDING POWER WITH PAU...TYPICAL RUN TIME ON INERTIA ROLLING ROAD 4 SECS IN DIRECT TOP WITH 300 BHP ENGINE)
So, sadly I can't say what your precise power loss is. If you changed tyre and or tyre size you would get a different figure.
However Michelin have led the way for 25 years + on low rolling resistance compounds and technology, so a Michelin tyre will normally offer you amongst the best Rolling Resistance on the market as part of its design criteria.
THERE WE GO
PETER
My thoughts are in Capital Letters in brackets.Peter,
I can't directly tell you you will lose "X" bhp, as it's not quite as straight forward as that.
Our figures suggest a 20% energy loss from the system in purely overcoming rolling resistance of the tyre. (ALL FOUR TYRES TAKE 20%?)
But again, energy losses from drive train, component friction and drag (WIND RESISTANCE IS A FUNCTION OF CUBE OF SPEED) will probably account for more single losses
Tyres absorb energy primarily through hysteresis of the compound and carcass.
Therefore a tyre running at it's optimum pressure will absorb less than an under-inflated tyre, producing much more heat as it flexes and rolls.
The remaining tread depth and condition of the rubber itself will also influence what heat is generated.
Rolling roads are particularly bad for tyres, as they tend to build heat up in the compound very rapidly as their surface heats the tyre much more than a normal road.
The metallic drum also has a higher heat potential making the tyre/drum contact quite different to what we see on the road. It is not uncommon to blister a tyre on a rolling road (WHEN HOLDING POWER WITH PAU...TYPICAL RUN TIME ON INERTIA ROLLING ROAD 4 SECS IN DIRECT TOP WITH 300 BHP ENGINE)
So, sadly I can't say what your precise power loss is. If you changed tyre and or tyre size you would get a different figure.
However Michelin have led the way for 25 years + on low rolling resistance compounds and technology, so a Michelin tyre will normally offer you amongst the best Rolling Resistance on the market as part of its design criteria.
THERE WE GO
PETER
andygtt said:
I don't have telemetry from 60-130mph (unless I stick bits of telemetry together)... but I do have 70-140mph of 5.3 seconds or 70-130mph 4.6 seconds with 2 people in the car... so 1030kgs plus driver 95kgs and passenger 90kgs... so 1215kgs... I don't have 1/4 mile times or anything yet.
I do. I ran your car through my vehicle performance simulation programme. So 1030kg plus two fat bds, assume 0.85g grip off the line (0-60 mph 3.2s) from best quality road tyres and mid engine rwd weight distribution, 0.2 second gearchange time as I recall you telling John down the pub how you'd just managed to obtain those with practice.I get good agreement to your 70-140 mph time with 720 bhp. Your 70-130 times are wrong. They should be exactly 1 second quicker than 70-140 as 1 second is your 130-140 time. 1/4 mile is 10.5 at 150 mph with perfect launch and gearshifts. With drag slicks and optimised gearing that could be 9.2 seconds at 154 mph.
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