Drivetrain losses
Discussion
PeterBurgess said:
V8 MGB with 328 at wheels, old way 328 +12 x 1.1 = 374, dynocom 328 +22 = 350 error increasing with old way.Peter
No, error increasing with Dynocom way as notional coastdown loss figure becomes progressively further away from true transmission loss figure at high power outputs.MGB transmission variations and hence variables when calculating flywheel power
Coastdown recordings.4th Gear.
95 mph road engine 20bhp losses MGB 4 speed box
95 mph road engine 22bhp losses MGB 4 speed O/D gearbox
drop tyre pressures from 32 to 18 psi losses increase by 5.7bhp
95 mph road engine 26bhp losses with leak stop gloop in rear axle.
95 mph road engine 18bhp losses Ford five speed box conversion
All running same diffs and road tyres of different makes, these are average figures from 4.5 years testing.
120 mph race engine 26 losses MGB 4 speed box modern road legal race tyres
120 mph race engine 28 losses old fashioned Dunlop class reg road legal race tyres.
120 mph race engine 28 losses MGB 4 speed O/D box mod road legal race tyres
120 mph race engine 22 losses thin oiled Ford five speed conversion mod road legal race tyres..
We have a 10 bhp variation in wp with just the gear boxes and being a higher speed engine and hence road speed. If the 28 bhp loss B was tested with 18 psi tyres we would probably have seen 34ish losses. Whether these are real figures or totally inaccurate they are repeated time after time to give us an idea of the variables and effects of them on wp.
Peter
Coastdown recordings.4th Gear.
95 mph road engine 20bhp losses MGB 4 speed box
95 mph road engine 22bhp losses MGB 4 speed O/D gearbox
drop tyre pressures from 32 to 18 psi losses increase by 5.7bhp
95 mph road engine 26bhp losses with leak stop gloop in rear axle.
95 mph road engine 18bhp losses Ford five speed box conversion
All running same diffs and road tyres of different makes, these are average figures from 4.5 years testing.
120 mph race engine 26 losses MGB 4 speed box modern road legal race tyres
120 mph race engine 28 losses old fashioned Dunlop class reg road legal race tyres.
120 mph race engine 28 losses MGB 4 speed O/D box mod road legal race tyres
120 mph race engine 22 losses thin oiled Ford five speed conversion mod road legal race tyres..
We have a 10 bhp variation in wp with just the gear boxes and being a higher speed engine and hence road speed. If the 28 bhp loss B was tested with 18 psi tyres we would probably have seen 34ish losses. Whether these are real figures or totally inaccurate they are repeated time after time to give us an idea of the variables and effects of them on wp.
Peter
Pumaracing said:
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 b
ds, 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.
Im hoping for quarters in the high 9's... given that with basically doing a burnout on a cold evening with cold tyres I did 0-60 in 3.4s and I have managed full throttle in 1st on hot tyres.... I've only done 1 full launch since i fitted the motec.
Also the Ultima 720 with same weight and similar power managed 9.9s quarters... and according to my telemetry I am a lot faster which knowing the engine builder means their engine isn't quite 700bhp.
My motec telemetry says I have done 130-140mph in 0.7s although I changed at just over 140 so the 140-150 was 1.2s.
I must say that I have seen the value that telemetry offers to racers... for example comparing 2 different runs down the same straight using full throttle one was 0.5s faster as I rev'd the car to close to 8000rpm than in one when i was changing up at 7300rpm even though the peak power is actually around 7000rpm and comes in at 6000rpm so I changed into the 'power band' in both instances.
My goal of the thread was not to validate my power figure, just to get a better idea if transmission losses could actually be tested in some way rather than guessed (sorry estimated)...
You all seemed to have confirmed what i have always believed... there is a lot of bull out there with no real way to prove or disprove it.
Spot on with guesstimates and pigeonholing.
We use the rollers to get the best we can out of cars, this involves the coastdown test which gives a value we can compare with other like cars to see all is in order, hence extra losses from gloop in axle. Race B had a badly installed prop uj added 10 to the losses and reduced wp correspondingly, customer repaired uj and losses and wp back to where we would expect for the spec of engine etc. We have tuned cars on the rollers as best we can since 1987 when I bought my Clayton. With the Dynocom installed 4 and half years ago we have changed up a gear or three with a wealth of info and comparisons so we have improved and filled in power at all rpms, albeit not much difference at peak power when retesting lots of the cars we had done on the old Clayton then on the Dynocom. Figures are irrelevant except we can compare like for like and get the best we can out of engines and drivetrains. Thats what I was saying about Silkolene reducing the viscocity and additives to get minimum friction yet still keep integrity till race finished, but not a lot longer, like Honda bikes being worn out at end of race, job done!
Once on the track we find out if we have done better than others which involves well prepared car, good driver and loadsa power!
The MGB figures I posted above are from the 400+ MGBs we have run in the 4 and a half years, not one or two and extrapolate but a good sample.
Peter
We use the rollers to get the best we can out of cars, this involves the coastdown test which gives a value we can compare with other like cars to see all is in order, hence extra losses from gloop in axle. Race B had a badly installed prop uj added 10 to the losses and reduced wp correspondingly, customer repaired uj and losses and wp back to where we would expect for the spec of engine etc. We have tuned cars on the rollers as best we can since 1987 when I bought my Clayton. With the Dynocom installed 4 and half years ago we have changed up a gear or three with a wealth of info and comparisons so we have improved and filled in power at all rpms, albeit not much difference at peak power when retesting lots of the cars we had done on the old Clayton then on the Dynocom. Figures are irrelevant except we can compare like for like and get the best we can out of engines and drivetrains. Thats what I was saying about Silkolene reducing the viscocity and additives to get minimum friction yet still keep integrity till race finished, but not a lot longer, like Honda bikes being worn out at end of race, job done!
Once on the track we find out if we have done better than others which involves well prepared car, good driver and loadsa power!
The MGB figures I posted above are from the 400+ MGBs we have run in the 4 and a half years, not one or two and extrapolate but a good sample.
Peter
Edited by PeterBurgess on Friday 3rd October 06:27
andygtt said:
I find this very Interesting, although in truth I'm not sure if you taking the piss out of me or not lol
Would I take the piss out of a fellow accountant? Moi?Anyhoo, details of the capabilities and design of my vehicle performance computer simulation programme are here.
https://web.archive.org/web/20110903091550/http://...
PeterBurgess said:
MGB transmission variations and hence variables when calculating flywheel power
Coastdown recordings.4th Gear.
<snip gibberish>Coastdown recordings.4th Gear.
Why do you keep posting coastdown losses? What point is it you're trying to make? Do you understand they have nothing to do with actual transmission losses under power or not?
I am trying to show that losses will vary with spec not constant as you seem to promote. The factors I have mentioned will change your 'formula' with different spec Bs let alone all the different gearbox/axle/diff/tyre/pressure variables with other cars.
I am surprised you do not see your one size fits all cannot work, but such is life, I did psychology originally you did accounting, heyho, have a nice weekend. As an aside, I know you like a wee dram or three, I was interested to see the stats of previous employment of the great majority of the'high-ups' in the Scottish Whisky Industry, apparently accountancy careers lend themselves well to the long term approach required to produce such wonderful aromatic beverages.
Peter
I am surprised you do not see your one size fits all cannot work, but such is life, I did psychology originally you did accounting, heyho, have a nice weekend. As an aside, I know you like a wee dram or three, I was interested to see the stats of previous employment of the great majority of the'high-ups' in the Scottish Whisky Industry, apparently accountancy careers lend themselves well to the long term approach required to produce such wonderful aromatic beverages.
Peter
PeterBurgess said:
I am trying to show that losses will vary with spec not constant as you seem to promote.Peter
Honestly, I don't know what you think you get out of creating straw man arguments that someone else doesn't even say and then ranting against them - whether it's being deliberately obtuse or just obtuse.From my archived article below which you either still haven't bothered to read or just ignore.
https://web.archive.org/web/20110909141356/http://...
"So is there any way of really measuring the true transmission loss of a car? Yes - only one - by measuring the flywheel power on an accurate engine dyno, the wheel power on an accurate chassis dyno and taking one away from the other. There is no way on God's green earth of finding out the true transmission loss just by measuring the power at the wheels.
What each individual car loses is an unknown - it will depend on tyre sizes and pressure, suspension angles and other things, but it shouldn't be far from the figures above. For sure though, no 2wd car in the world, unless it has flat tyres and a gearbox full of sand, loses anything like 30% of the engine's power in the transmission and tyres as many rolling road operators would try to have you believe. In general though it is fair to say that low powered cars have higher % losses than high powered cars. This is because some of the frictional losses are independent of engine power and so represent a bigger drain on a small engine.
Remember, these percentages are not "gospel" - they are good realistic averages. The measured wheel bhp can change depending on tyre pressure, tyre size, suspension angles and other things which won't affect flywheel power - so the actual transmission loss % will also change. It pays to try and standardize as many of these things as possible if you intend to do a series of power runs over a period of time. Always use the same tyre pressure because this is a factor which can easily change from day to day and make sure the tracking is correct on a fwd car.
Also please remember that the manufacturer's claimed power figures for a standard car are not gospel either. Even engines in perfect condition can vary by plus or minus 5% due to manufacturing tolerances. High mileage or poorly maintained engines can be well below the claimed output. It is no proof that a rolling road flywheel bhp estimate is correct just because it comes out as the same figure as the manufacturer's. Always compare with the measured wheel bhp to see if the transmission losses agree with the data above."
You waste everyone's time on here by decreasing the signal to noise ratio of the good information that some people post by diluting it with nonsense that no one can benefit from. I think you just like winding people up with stupid arguments.
Pumaracing said:
andygtt said:
I find this very Interesting, although in truth I'm not sure if you taking the piss out of me or not lol
Would I take the piss out of a fellow accountant? Moi?Anyhoo, details of the capabilities and design of my vehicle performance computer simulation programme are here.
https://web.archive.org/web/20110903091550/http://...
so you either have a lot more information on specifics of my car or have made some detailed assumptions for your calculations... i remember you once promising to calculate my clutch and flywheel gains from you spreadsheet.
Im also guessing you have gear ratio's for the box etc?
Age does not make you any less arrogant or rude it would seem Dave. I do not attack you personally and I think you would do well to try and keep a civil tongue in your head when dealing with others.
You are a clever person with a lot of knowledge it would be nice to see you share it with people in a reasonable manner instead of 'shouting' at anyone who might differ from your view, remember the scientific approach, thesis, antithesis and synthesis.
As I said, have a nice weekend.
Peter
You are a clever person with a lot of knowledge it would be nice to see you share it with people in a reasonable manner instead of 'shouting' at anyone who might differ from your view, remember the scientific approach, thesis, antithesis and synthesis.
As I said, have a nice weekend.
Peter
andygtt said:
again very interesting...
so you either have a lot more information on specifics of my car or have made some detailed assumptions for your calculations... i remember you once promising to calculate my clutch and flywheel gains from you spreadsheet.
Im also guessing you have gear ratio's for the box etc?
The approximate drag coefficient was easily worked out from top speed vs engine power from other Noble models. I put in a generic set of 6 speed gear ratios and tweaked them about a bit. Estimated the rotational inertia of your very light clutch/flywheel. Set transmission losses for approx 700 bhp. Copied the power curve from the pic you posted online and put the max rpm to 8000 and then tweaked the power curve up and down until the times matched. Nothing very complex but enough to dial in the important parameters within a percent of two of actual performance.so you either have a lot more information on specifics of my car or have made some detailed assumptions for your calculations... i remember you once promising to calculate my clutch and flywheel gains from you spreadsheet.
Im also guessing you have gear ratio's for the box etc?
I also did the Ultima 720 for fun given they've posted 1/4 mile times and speeds and lots of other performance stats. However they'd probably be very cross if I revealed just how much massively less than 720 bhp it actually has
It just has shed loads of grip off the line which enabled it to break 10s in the 1/4. It now holds the record for the most overstated power output of any car I've modelled.Dave
When I see a line of words from your writing;Approximate generic tweaked Estimated approx tweaked, I can only feel you are manipulating figures to make them show that which you wish to do so?
You take the figs as 'gospel' for bhp of factory Nobles to generate CD of Noble, what if BHP is incorrect from the factory as you say Ultima is incorrect? If Noble had less power CD would have to be lower n'est ce pas? Therefore Andy would have lower CD and not need so much bhp? Only musings.
Peter
When I see a line of words from your writing;Approximate generic tweaked Estimated approx tweaked, I can only feel you are manipulating figures to make them show that which you wish to do so?
You take the figs as 'gospel' for bhp of factory Nobles to generate CD of Noble, what if BHP is incorrect from the factory as you say Ultima is incorrect? If Noble had less power CD would have to be lower n'est ce pas? Therefore Andy would have lower CD and not need so much bhp? Only musings.
Peter
Somewhat miffed by the extraordinary amount of bhp the Ultima 720 appears to be lacking from its claimed 720 bhp when I modelled its performance I did a bit of googling and found this dyno test.
http://www.youtube.com/watch?v=t8QiQpzXUEw
If you download it and scroll through a frame at a time you can see it failing to make 500 bhp, which I presume is at the wheels. I could not possibly say in public just how close that is, when adjusted for transmission losses, to the flywheel bhp my computer programme calculated for its tested performance
Now I know bugger all about modern American engines but naively assumed that a claimed 100 plus bhp per litre from an LS7, whatever that is, indicated a 4v engine with some mighty fancy bits inside it at the very least. Imagine my surprise when I googled and found it's just a cooking 2v engine for which both my calculated bhp and this dyno test make perfect sense.
How can people lie this blatantly? My mummy and daddy brought me up to be a good little boy. "Tell the truth and shame the devil" they used to tell me before beating me into unconsciousness and sending me to bed without supper to read the bible. Well none of that ever did me any harm. These people who just invent bhp numbers would probably benefit from a damn good thrashing too.
http://www.youtube.com/watch?v=t8QiQpzXUEw
If you download it and scroll through a frame at a time you can see it failing to make 500 bhp, which I presume is at the wheels. I could not possibly say in public just how close that is, when adjusted for transmission losses, to the flywheel bhp my computer programme calculated for its tested performance
Now I know bugger all about modern American engines but naively assumed that a claimed 100 plus bhp per litre from an LS7, whatever that is, indicated a 4v engine with some mighty fancy bits inside it at the very least. Imagine my surprise when I googled and found it's just a cooking 2v engine for which both my calculated bhp and this dyno test make perfect sense.
How can people lie this blatantly? My mummy and daddy brought me up to be a good little boy. "Tell the truth and shame the devil" they used to tell me before beating me into unconsciousness and sending me to bed without supper to read the bible. Well none of that ever did me any harm. These people who just invent bhp numbers would probably benefit from a damn good thrashing too.
Interesting video Dave, poor camera work, absolutely cr*p to be honest. Walks away at the 'wrong' moment doesn't he/she? As you say maybe that is all it made at the wheels, maybe the crap camera work missed the peak power, maybe the car wp is crap as you predict. Manufacturers shouldnt bull should they as they get caught out
Peter
Peter
I bought my engine for my Ultima from the same company that the Ultima 720 comes from.. it was claimed as bench dyno'd by the tuner as 526bhp... I took the engine out and had it bench dyno'd by Peter Knight and it cam out at 490bhp... Id paid for a 500bhp engine so was fairly happy.
We then removed the dyno headers and fitted the Ultima ones I ran and it only lost another 10bhp... but in mid range it lost 60ftlb.... my car was same weight as the Ultima 720 and I did quarter mile times of 11.4 @ 126mph at the pod were they did their runs.
Given cars like the Enzo and F1 my times were pretty much were you would expect... I have a mini spreadsheet I wrote to predict times as well, its not as advanced as yours but wasn't that inaccurate (a few cars didn't fit the model though).
Do you remember Autocar testing an Ultima in their 0-100-0 way back in 2002?... that was me and I wasn't popular with the factory after that as they had continually refused to provide a car
So I am very very confident the Ultima 720 has a lot more power than 500bhp...
Incidentally I find my noble has a lot more traction than my Ultima had!
We then removed the dyno headers and fitted the Ultima ones I ran and it only lost another 10bhp... but in mid range it lost 60ftlb.... my car was same weight as the Ultima 720 and I did quarter mile times of 11.4 @ 126mph at the pod were they did their runs.
Given cars like the Enzo and F1 my times were pretty much were you would expect... I have a mini spreadsheet I wrote to predict times as well, its not as advanced as yours but wasn't that inaccurate (a few cars didn't fit the model though).
Do you remember Autocar testing an Ultima in their 0-100-0 way back in 2002?... that was me and I wasn't popular with the factory after that as they had continually refused to provide a car
So I am very very confident the Ultima 720 has a lot more power than 500bhp...
Incidentally I find my noble has a lot more traction than my Ultima had!
According to Google the 7 litre Ultima LS7 has 2.2" inch inlet valves which are the main determinant of power. Running a V8, 2v per cylinder, 7 litre engine of those dimensions through my computer power prediction programme, and even being extremely charitable with the head flow efficiency, cam duration and inlet system efficiency I get about 550 flywheel bhp for an engine in relatively driveable road going trim. Funny that eh? The same number the measured performance, the Youtube dyno test and the numbers from various other engine tuners that Google has found who've had a crack at this engine actually claim to generate rather than the 720 bhp Ultima claim. That's 170 missing bhp somewhere. I wonder where it went?
andygtt said:
So I am very very confident the Ultima 720 has a lot more power than 500bhp...
Seriously? Let's just say 550 flywheel bhp. Now I can't tell if you're being ironic, sarcastic, obtuse or just taking the piss out of me. However Newton's Laws of Motion determine the acceleration and speed of a body under given thrust and retardation forces and a computer can work those out to tiny fractions.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff