Engine to Chassis Dyno HP lose
Discussion
Pumaracing said:
That's not much help when what you've got to work from is flywheel bhp or OE manufacturer road car power curves. It's essential to be able to at least approximate transmission and tyre losses.
In fact much of the early work I did circa 20 years ago on establishing what true transmission and tyre losses really were was by computer simulating many cars tested by Autocar and Motor magazine and seeing what level of losses were required from the quoted flywheel bhp to match the tested performance. Now of course there's no guarantee that every car tested had exactly the claimed flywheel bhp but averaged over many simulations I was able to find very consistent patterns of loss which eventually gave rise to the loss equations for manual transmission cars on my website.
https://web.archive.org/web/20110909141356/http://...
In the 15 or so years since writing that I've found nothing to alter my view that these give a very close approximation of real losses for most cars.
Many years ago, around 1988 iirc Performance Bikes magazine took a bog standard Kawasaki GPX750, (750cc 16 valve inline four) and put it on the dyno. All the following numbers are from memory so not exactly exact...In fact much of the early work I did circa 20 years ago on establishing what true transmission and tyre losses really were was by computer simulating many cars tested by Autocar and Motor magazine and seeing what level of losses were required from the quoted flywheel bhp to match the tested performance. Now of course there's no guarantee that every car tested had exactly the claimed flywheel bhp but averaged over many simulations I was able to find very consistent patterns of loss which eventually gave rise to the loss equations for manual transmission cars on my website.
https://web.archive.org/web/20110909141356/http://...
In the 15 or so years since writing that I've found nothing to alter my view that these give a very close approximation of real losses for most cars.
At the rear wheel it put out 90ish bhp, whilst it was on the dyno they also measured how much fuel it was consuming, about 360bhp worth. So around 270bhp was going missing somewhere during the combustion/power transmission process.
First thing they measured was the coolant, oil and exhaust gas temperatures. Knowing the volumes of the fluids and their temperatures they calculated around 25%/90bhp was being lost as heat!
Then iirc they removed the clutch and span the crank to measure pumping losses, how much it cost to get the fuel/air mix in and out of the engine. I can't remember the numbers on that test but it was quite a bit.
The cylinder head was removed for the following test and the crank was spun up to speed again, over 20% in frictional losses just from the pistons and bearings!
The water and oil pumps were about 5% iirc
The final test was to connect the dyno to the output shaft and measure how much just the gearbox was sapping, around 20% again! The 20% on the gearbox was the main reason I had my gearbox internals polished whilst my engine was in bits.
As I said at the start, all numbers are from memory so they are a bit out, in fact I think the heat losses my have been over 30%
The bike magazines of the late 80's early 90's were dyno testing every single bike they road tested and their numbers were always lower than the manufacturers claimed. In the end the manufacturers started to quote rear wheel horsepower instead of crank horsepower as they were fed up with being portrayed as bulls
tters.Just to make life awkward, MG tested their engines with the gearbox fitted and running in 4th gear (direct top, I don't know when the factory started testing without boxes on.
Stan,
I will say hi to Martin for you. Thanks for the lead at Performance Trends. I think Martin is a 'preferred shopper' there as well!
What I am after is wiring diagrams for the SF901pro if you know any of your contacts who might help? The dyno manual is pretty basic and not a patch on the Clayton chassis and engine dyno manuals. It would make life a lot easier than the head scratching we have to do at times. It has been used via a pc in the past, a 486 on dos/windows 3.1? We want to run it through a modern pc hence hoping the Performance Trends software will do this....have to find an old pc and dot matrix printer otherwise
Peter
Stan,
I will say hi to Martin for you. Thanks for the lead at Performance Trends. I think Martin is a 'preferred shopper' there as well!
What I am after is wiring diagrams for the SF901pro if you know any of your contacts who might help? The dyno manual is pretty basic and not a patch on the Clayton chassis and engine dyno manuals. It would make life a lot easier than the head scratching we have to do at times. It has been used via a pc in the past, a 486 on dos/windows 3.1? We want to run it through a modern pc hence hoping the Performance Trends software will do this....have to find an old pc and dot matrix printer otherwise
Peter
Hi Stan
A quick update for you with regard to the SF901 installation. A big thanks for the files you have sent us and for the advice you have written to us, it all helped us move a step closer.
The dyno is now speaking through the console to the pc, hoozah We needed Windows 98SE with a serial port....Toshiba Tecra laptop cheap on ebay is doing the job. We get a nice 40 rpm on the rev counter when we spin the dyno shaft! Turns out the dyno was purchased with eproms to produce power in Kw and torque in Nm. The guys at Superflow are most helpful and have given us a load of info and instructions for getting it all running. We can buy US spec eproms and an update CD for around $250, we may well do this once we are happy the package is working in harmony. Although the dyno was originally built in 1992 it has been updated up to and including 2000 so we have to sort out what is what for the hardware and software.
Next step fill the water tank and wire up the fans and water pumps.
I must say I am very impressed with Superflow's attitude. They are very helpful and there is no push push shove to upgrade or buy a new dyno.
Peter
A quick update for you with regard to the SF901 installation. A big thanks for the files you have sent us and for the advice you have written to us, it all helped us move a step closer.
The dyno is now speaking through the console to the pc, hoozah
We needed Windows 98SE with a serial port....Toshiba Tecra laptop cheap on ebay is doing the job. We get a nice 40 rpm on the rev counter when we spin the dyno shaft! Turns out the dyno was purchased with eproms to produce power in Kw and torque in Nm. The guys at Superflow are most helpful and have given us a load of info and instructions for getting it all running. We can buy US spec eproms and an update CD for around $250, we may well do this once we are happy the package is working in harmony. Although the dyno was originally built in 1992 it has been updated up to and including 2000 so we have to sort out what is what for the hardware and software.Next step fill the water tank and wire up the fans and water pumps.
I must say I am very impressed with Superflow's attitude. They are very helpful and there is no push push shove to upgrade or buy a new dyno.
Peter
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