Having recently just had the 1600 on a dyno I have been in deep thought about the acctual figures pruduced from the dyno. The reading it spat out was 248.5 nm of touque and 73kw. Now I know that a standard L16 engine is rated at 96hp(71.6kw) at the fly and the car certainly doesn't drive like stock L16 which leads me to believe the kw reading to be way off, but the nm to be pretty close.
Now the maths gets involved (all you young uni maths students time to step up!). Using calculations supplied from tech resources if you know definate figures like tyre diameter, ratio's, rpm & mph ect you can calculate hp from the torque reading and visaversa. Now inputing the hp reading into the equation I get 85nm NOW THATS WRONG. BUT input the nm reading of 248.5 I get 209 hp which to me is a lot closer to what i would be expecting from a Turbo L18 with 45DCOE Weber and all its mods.
What are other peoples experiences with dyno readings and what are your thoughts on what I have just explained?
Full Version: Applying Mathematics To Dyno's
What type of box do you have e.g. 5 speed
What gear was the car run in? e.g. 4th
Do you have a pic of the graph you can post up.?
What gear was the car run in? e.g. 4th
Do you have a pic of the graph you can post up.?
QUOTE (gun16 @ Jul 25 2008, 01:56 PM) 
What type of box do you have e.g. 5 speed
What gear was the car run in? e.g. 4th
Do you have a pic of the graph you can post up.?
What gear was the car run in? e.g. 4th
Do you have a pic of the graph you can post up.?
5 speed box. Done in 4th gear (1:1)
your calculations need to take driveline losses into account as well. as locked diffs ,low tyre pressure's,clutch or wheel slip,old uni's and much more can all affect real world perfomance on a dyno or the track. 
very hard to calculate these.. still seems like a big differance though 
very hard to calculate these.. still seems like a big differance though
All the calculations are based on rear wheel power figures not fly wheel, so drive line loss dose not come into it. And all normal procedures like tyre pressures before dyno run is carried out. You could also say there is rolling resistance and air density just to name a couple to take into account for aswell.
I was simply showing the rather large variation between the two readings thats all. My wifes Pulsar probably has more kw than that but it only goes half as quick.
I was simply showing the rather large variation between the two readings thats all. My wifes Pulsar probably has more kw than that but it only goes half as quick.
I think he is refering to when you compared the factory flywheel figure to your own.
yep standard car rwkw probably much lower than 71kw
alot lower. My L18 1600 made 56 kw atw back in the day lol.
there's more to it than just the numbers too, its the whole area under the curve thing... stock could be the same as after you've worked it, but your midrange torque/power could be waaaay up, kinda like the curve you have there meaning it drives heaps better.
There's also different types of dyno's, different time of day/climate, to back when it was first tested in japan, changing the air density as you mentioned.
I think its best to see dyno's as a tool, to help tune a car rather than to give an exact figure. The shape of the curve means more than the numbers (except when you're having a brag to ya mates), they're just there to give you a ballpark as to how high up the scale it goes. After all we all know that the amount of horsepower, while it does have a big impact isn't the only thing that helps you win races. tyres/suspension/gearbox ratios etc. etc. have a huge impact as well.
Even when it comes to dyno competitions it only works because all the cars are run on the same dyno.
Not necessarily. For example, to do 20mph it might only be using 30Nm of the 300Nm available to it. Those equations will probably give you the torque required to travel at a set speed, not the maximum amount of torque that your engine is producing. It is also impossibly hard to model the amount of friction of a gear train under acceleration.
The rwhp vs. flywheel hp is important to keep in mind as well. I believe its flywheel hp x 0.75 = rwhp, as well as hp x 0.75 =
kW.
If you put that together you get approximately flywheel hp x 0.5 = rwkW
assuming your figure is rwkW, its about 150hp at the flywheel... which is a 50% increase in power.
I hope my logic follows thru, its 1am after all...
There's also different types of dyno's, different time of day/climate, to back when it was first tested in japan, changing the air density as you mentioned.
I think its best to see dyno's as a tool, to help tune a car rather than to give an exact figure. The shape of the curve means more than the numbers (except when you're having a brag to ya mates), they're just there to give you a ballpark as to how high up the scale it goes. After all we all know that the amount of horsepower, while it does have a big impact isn't the only thing that helps you win races. tyres/suspension/gearbox ratios etc. etc. have a huge impact as well.
Even when it comes to dyno competitions it only works because all the cars are run on the same dyno.
QUOTE
Using calculations supplied from tech resources if you know definate figures like tyre diameter, ratio's, rpm & mph ect you can calculate hp from the torque reading and visaversa. Now inputing the hp reading into the equation I get 85nm NOW THATS WRONG
Not necessarily. For example, to do 20mph it might only be using 30Nm of the 300Nm available to it. Those equations will probably give you the torque required to travel at a set speed, not the maximum amount of torque that your engine is producing. It is also impossibly hard to model the amount of friction of a gear train under acceleration.
The rwhp vs. flywheel hp is important to keep in mind as well. I believe its flywheel hp x 0.75 = rwhp, as well as hp x 0.75 =
kW.
If you put that together you get approximately flywheel hp x 0.5 = rwkW
assuming your figure is rwkW, its about 150hp at the flywheel... which is a 50% increase in power.
I hope my logic follows thru, its 1am after all...
QUOTE (DJ @ Aug 19 2008, 01:54 AM)
there's more to it than just the numbers too, its the whole area under the curve thing... stock could be the same as after you've worked it, but your midrange torque/power could be waaaay up, kinda like the curve you have there meaning it drives heaps better.
There's also different types of dyno's, different time of day/climate, to back when it was first tested in japan, changing the air density as you mentioned.
I think its best to see dyno's as a tool, to help tune a car rather than to give an exact figure. The shape of the curve means more than the numbers (except when you're having a brag to ya mates), they're just there to give you a ballpark as to how high up the scale it goes. After all we all know that the amount of horsepower, while it does have a big impact isn't the only thing that helps you win races. tyres/suspension/gearbox ratios etc. etc. have a huge impact as well.
Even when it comes to dyno competitions it only works because all the cars are run on the same dyno.
Not necessarily. For example, to do 20mph it might only be using 30Nm of the 300Nm available to it. Those equations will probably give you the torque required to travel at a set speed, not the maximum amount of torque that your engine is producing. It is also impossibly hard to model the amount of friction of a gear train under acceleration.
The rwhp vs. flywheel hp is important to keep in mind as well. I believe its flywheel hp x 0.75 = rwhp, as well as hp x 0.75 =
kW.
If you put that together you get approximately flywheel hp x 0.5 = rwkW
assuming your figure is rwkW, its about 150hp at the flywheel... which is a 50% increase in power.
I hope my logic follows thru, its 1am after all...
There's also different types of dyno's, different time of day/climate, to back when it was first tested in japan, changing the air density as you mentioned.
I think its best to see dyno's as a tool, to help tune a car rather than to give an exact figure. The shape of the curve means more than the numbers (except when you're having a brag to ya mates), they're just there to give you a ballpark as to how high up the scale it goes. After all we all know that the amount of horsepower, while it does have a big impact isn't the only thing that helps you win races. tyres/suspension/gearbox ratios etc. etc. have a huge impact as well.
Even when it comes to dyno competitions it only works because all the cars are run on the same dyno.
Not necessarily. For example, to do 20mph it might only be using 30Nm of the 300Nm available to it. Those equations will probably give you the torque required to travel at a set speed, not the maximum amount of torque that your engine is producing. It is also impossibly hard to model the amount of friction of a gear train under acceleration.
The rwhp vs. flywheel hp is important to keep in mind as well. I believe its flywheel hp x 0.75 = rwhp, as well as hp x 0.75 =
kW.
If you put that together you get approximately flywheel hp x 0.5 = rwkW
assuming your figure is rwkW, its about 150hp at the flywheel... which is a 50% increase in power.
I hope my logic follows thru, its 1am after all...
Good comments ther DJ.
My early days of tuning with roller dynos was 1970, water brake dyno.
Only reading you got was from a hydraulic pressure gauge ( torgue reaction from the roller )
and a roller speed as MPH. you then used a graph for RWHP/torqe @ X rpm
The only dyno that i can say has impressed me is the Dynapac
http://www.hondatech.com.au/forum/showthread.php?t=1597
QUOTE (Baz @ Aug 19 2008, 07:57 PM)
Good comments ther DJ.
My early days of tuning with roller dynos was 1970, water brake dyno.
Only reading you got was from a hydraulic pressure gauge ( torgue reaction from the roller )
and a roller speed as MPH. you then used a graph for RWHP/torqe @ X rpm
The only dyno that i can say has impressed me is the Dynapac
http://www.hondatech.com.au/forum/showthread.php?t=1597
My early days of tuning with roller dynos was 1970, water brake dyno.
Only reading you got was from a hydraulic pressure gauge ( torgue reaction from the roller )
and a roller speed as MPH. you then used a graph for RWHP/torqe @ X rpm
The only dyno that i can say has impressed me is the Dynapac
http://www.hondatech.com.au/forum/showthread.php?t=1597
Thanks Baz!
We have a water brake dyno at uni to mess around with, although one student was so kind as to do a project on it and make it a *little* more sophisticated...
I had a quick skim through that article, and this jumped out at me:
QUOTE
Remember a dynos are not an accurate power output device. A dyno is a tuning tool which allows a tuner to apply variable amounts of load on an engine testing its performance in all load and throttle positions. The only conclusive evidence which can be drawn from any dyno is a before and after result. A car started off with this much power, and now has this much.
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