Anyone used John Noble Dyno
24-09-2009, 09:30 PM
#42
No, he does "sort of" get it, but he is playing with ur words.
The wheel figure, whilst "consistent" under the exact same circumstances, gear, tyres, etc etc etc is not necessarily "accurate" in the power that it sees.
The wheel figure is the basis of the flywheel calculation/guess so if it is totally flawed, then unless ur clever calc/guess takes care of that inaccuracy, then ur flywheel figure will be inaccurate too.
When AVA says I have 195 at the wheels in my RST and nobles says 175 at the wheels. Both are just telling u the effort that the retarder needs to put in to control the rpm.
That will mean it requires less effort if the rollers are rotating faster (smaller dia. rollers, or higher gear used etc).
The calculation back to flywheel power is a guess/estimate. AVA *might* give u a guess at the flywheel fig, if u push them but they will tell u it is a guess (a rather educated one, if u know ur cars and ur rollers and regularly use big power, new, reliable N/A cars to bench mark) other people allow the software to guess for them.
In my case, I saw both rollers give different wheel figures (due to roller speed) however the estimates at flywheel were remarkably close.
Cheers
RW
The wheel figure, whilst "consistent" under the exact same circumstances, gear, tyres, etc etc etc is not necessarily "accurate" in the power that it sees.
The wheel figure is the basis of the flywheel calculation/guess so if it is totally flawed, then unless ur clever calc/guess takes care of that inaccuracy, then ur flywheel figure will be inaccurate too.
When AVA says I have 195 at the wheels in my RST and nobles says 175 at the wheels. Both are just telling u the effort that the retarder needs to put in to control the rpm.
That will mean it requires less effort if the rollers are rotating faster (smaller dia. rollers, or higher gear used etc).
The calculation back to flywheel power is a guess/estimate. AVA *might* give u a guess at the flywheel fig, if u push them but they will tell u it is a guess (a rather educated one, if u know ur cars and ur rollers and regularly use big power, new, reliable N/A cars to bench mark) other people allow the software to guess for them.
In my case, I saw both rollers give different wheel figures (due to roller speed) however the estimates at flywheel were remarkably close.
Cheers
RW
24-09-2009, 09:34 PM
#43
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Good sumary rw.
I Ran a standard fq300 and it came out bank on the mark.
Wat do you think to the way dyno dynamics use there rollers, using 3rd gear. I dnt like them. 4 instance how can you tell if there slight wheelspin in 3rd gear.
I Ran a standard fq300 and it came out bank on the mark.
Wat do you think to the way dyno dynamics use there rollers, using 3rd gear. I dnt like them. 4 instance how can you tell if there slight wheelspin in 3rd gear.
24-09-2009, 11:08 PM
#44
I'm not really sure I understand ur question?
Wheelspin would be where engine RPM increases but roller RPM doesn't. Not sure if the rollers can tell that - however, from what I have seen, when u run up on a load sustaining r/r (ie it holds rpm against power for a few seconds to get a reading) it was pretty obvious if it was wheel spinning.
As for the dyno dynamics comment - I am not a specialist. If you took an M3 and ran it up and it came back about 410 to 415bhp, then that would do me.
I am thinking about why they would force u to use third gear? 3rd gear on every car will result in different roller speed. Maybe it is just because they are not speed rated very high and so they insist on third to try and reduce the overall roller speed (ie keep it in spec). Or maybe the run down calcs they use to work out engine bhp, works better when they keep the rollers within a set speed range, as they have spent time calculating the losses that the rollers experience from that exact speed range. Therefore increasing the 'accuracy' of the fly wheel figure.
I am guessing they might be trying to reduce variance between the same cars run up in different gears, making different wheel bhp, throwing off people who don't really understand therefore getting them a bad reputation, due to lack of understanding.
Who knows
RW
Wheelspin would be where engine RPM increases but roller RPM doesn't. Not sure if the rollers can tell that - however, from what I have seen, when u run up on a load sustaining r/r (ie it holds rpm against power for a few seconds to get a reading) it was pretty obvious if it was wheel spinning.
As for the dyno dynamics comment - I am not a specialist. If you took an M3 and ran it up and it came back about 410 to 415bhp, then that would do me.
I am thinking about why they would force u to use third gear? 3rd gear on every car will result in different roller speed. Maybe it is just because they are not speed rated very high and so they insist on third to try and reduce the overall roller speed (ie keep it in spec). Or maybe the run down calcs they use to work out engine bhp, works better when they keep the rollers within a set speed range, as they have spent time calculating the losses that the rollers experience from that exact speed range. Therefore increasing the 'accuracy' of the fly wheel figure.
I am guessing they might be trying to reduce variance between the same cars run up in different gears, making different wheel bhp, throwing off people who don't really understand therefore getting them a bad reputation, due to lack of understanding.
Who knows
RW
Last edited by Steven_RW; 24-09-2009 at 11:12 PM.
25-09-2009, 11:30 AM
#46
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wonder if rollers get less accurate as the wheel speed gets higher an higher like u say, who nows. I no dyno dynamices cost about Ł20000 cheaper than nobles mahal (spelling police needed lol)
25-09-2009, 02:29 PM
#47
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I do get it, you say the atw figure is inaccurate, yet the power reading is taken from the wheels by the machine then calculates the fly power.
So your whole argument is flawed, just like your neurological set up.
So your whole argument is flawed, just like your neurological set up.
25-09-2009, 04:16 PM
#48
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how i checked my local road was i put a 6 month old fiesta on the rollers first totally standard and had done 7000 miles, it came within 1 bhp of standard flywheel manufacturers bhp so that was near enough for me.
25-09-2009, 08:13 PM
#49
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26-09-2009, 12:56 PM
#51
lol - Your amusing
Okay - question back - what exactly does a rolling road measure? IE - what does it do to measure power and what part of it measures the power and how does an R/R work.
If you are 80 iq points ahead of me, your doing just fine
RW
Okay - question back - what exactly does a rolling road measure? IE - what does it do to measure power and what part of it measures the power and how does an R/R work.
If you are 80 iq points ahead of me, your doing just fine
RW
27-09-2009, 04:17 PM
#56
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From the rollers, you need to 4get the idea of, its the wheels turning, so the wheel figure must be accurate, wen thats not how it works.
If you want to take the wheel figure, then call it a estimation. as 10 psi more in my tyres wud affect the result, so wud size of wheels, so wud witch gear it was run in etc etc etc etc etc etc etc.
If you want to take the wheel figure, then call it a estimation. as 10 psi more in my tyres wud affect the result, so wud size of wheels, so wud witch gear it was run in etc etc etc etc etc etc etc.
27-09-2009, 06:20 PM
#57
They measure the effort that the retarder has to put in to maintain the rpm that the r/r has asked for (using a strain gauge attached to the retarder). That could be a constant ramp if it is "shootout mode" or it could be a sustained load point.
So the r/r measures the effort the retarder has to put in to maintain roller RPM as requested.
As roller RPM increases, the effort required to turn the rollers (just themselves with no retarder attached) increases.
Therefore with a basic car that has around 100 bhp and say 85 lb ft. If the car is run up in say 2nd gear (with rollers turning at 55mph e.g.) X amount of effort will need to be used by the retarder to maintain roller rpm (stop the car accelerating). If you shifted into 3rd, the rollers will be going around quicker, and the rollers themselves, take more effort to turn, so the retarder will need to use LESS than X effort to maintain rpm (stop the car accelerating) as the rollers themselves absorb more effort to turn at higher rpm. They are like a fan in the way that 1kw = 100rpm, 2kw does NOT equal 200rpm, due to increasing losses of efficiency, it will be more like 3kw = 200rpm.
SOOOOO - what that means, to u, is that the r/r measures the effort put in by the retarder to maintain set roller rpm, and therefore it does NOT measure torque at wheels as u suggest. A calculation is then completed that turns the effort used by the retarder, (initially measured using a strain gauge iirc) into a torque figure. Therefore, how can u be sure ur initial ATW figure is "accurate" in ur terms? It will just become smaller and smaller as roller RPMs rise. SO u need to take a big power, reliable standard car and run it up once in a while to use as a benchmark / calibration in each gear.
That is my take on it anyway and goes to show there is more to it than meets the eye.
RW
So the r/r measures the effort the retarder has to put in to maintain roller RPM as requested.
As roller RPM increases, the effort required to turn the rollers (just themselves with no retarder attached) increases.
Therefore with a basic car that has around 100 bhp and say 85 lb ft. If the car is run up in say 2nd gear (with rollers turning at 55mph e.g.) X amount of effort will need to be used by the retarder to maintain roller rpm (stop the car accelerating). If you shifted into 3rd, the rollers will be going around quicker, and the rollers themselves, take more effort to turn, so the retarder will need to use LESS than X effort to maintain rpm (stop the car accelerating) as the rollers themselves absorb more effort to turn at higher rpm. They are like a fan in the way that 1kw = 100rpm, 2kw does NOT equal 200rpm, due to increasing losses of efficiency, it will be more like 3kw = 200rpm.
SOOOOO - what that means, to u, is that the r/r measures the effort put in by the retarder to maintain set roller rpm, and therefore it does NOT measure torque at wheels as u suggest. A calculation is then completed that turns the effort used by the retarder, (initially measured using a strain gauge iirc) into a torque figure. Therefore, how can u be sure ur initial ATW figure is "accurate" in ur terms? It will just become smaller and smaller as roller RPMs rise. SO u need to take a big power, reliable standard car and run it up once in a while to use as a benchmark / calibration in each gear.
That is my take on it anyway and goes to show there is more to it than meets the eye.
RW
Last edited by Steven_RW; 27-09-2009 at 06:28 PM.
28-09-2009, 02:26 PM
#63
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done numerous runs at york with mine. too many to count really. but thats more down to the driver than the car as well.
quite a few people junk there spare wheel,drop tyre pressures etc. quite a few people getting under 2 seconds to 60ft, where as i can only get a 2.1 second 60ft.
quite a few people junk there spare wheel,drop tyre pressures etc. quite a few people getting under 2 seconds to 60ft, where as i can only get a 2.1 second 60ft.
28-09-2009, 09:19 PM
#64
Testing the future
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