diga -tron data aquisition systems dt 50

[stewart]

i wonder why there can be a differance in the hp reading  if dyno is rpm calibrated off the  drum spinning  rpm....verses  rpm from inductive pick up ,, even when we have 3 devices testing the inductive reading that say its acurate ,, i have seen this and some other factors like start speed of test etc vary rear wheel hp numbers..i relize that its possiable to make much higher flash numbers but as has been written before in many 2 stroke books  sustanible hp is not always as high

[flyin9]

are you taking into effect, outside air temp, (outside the building), inside airtemp(inside), relative humidity, wet bulb temp and dry bulb temp, elevation, engine operating temperature, coolant IE is it water all the time 50/50 engine ice ect, tire temp, tire air pressure. all of these will make a diffrence. I can tell you first hand that just temperature alone will change your readings! my school has a dyno trailer and we were outside doing runs for high school kids. in 3 hours the temperature rose from 68* to 81* and we gained 2.5 HP. we did nothing to alter the bike, it was always brought up to the same operating temp and tire pressure was the the same. when doing testing you never want variables. try to keep everything as close to the same as you can.

[stewart]

yes we adjust for the temp  humidty altutuide etc very often

[flyin9]

that is good to hear! does your machine have the capibilities for an optical tach? that might help you out?

[stewart]

we can read dyno rpm from inductive at the plug  wire  ...or from drum calibration, i have seen that since gear ratio is tourque multipucation , the gear the bike is tested in would make  a different drive ratio and if the dyno  is only factoring inductive rpm  ..then first or 5th gear  bieng different could effect readings i have seen this change

[Larry Wiechman]

i wonder why there can be a differance in the hp reading  if dyno is rpm calibrated off the  drum spinning  rpm....verses  rpm from inductive pick up ,, even when we have 3 devices testing the inductive reading that say its acurate

I'll bet the dyno you're using doesn't measure RPM directly, it's calculated from drum RPM, wheel radius and gear reduction ratios. The big variable is the wheel radius. The tire deforms as a result of loading and power transmission. Chains, gears and driveshafts provide reliable data, rubber doughnuts do not.

[stewart]

larry it measures rpm off the motor ignition pulse , or it can be set at a given dyno wheel rpm in a given gear on the bike,,

[Larry Wiechman]

Which method are you using?

[flyin9]

larry, good call, it is important that the correct gear reduction, final drive, and tire calculation is correct! any one of those factors will change numbers greatly! 25%+ i have done it! its wrong but it can be done! so and so's HP juice! can add 2HP easy, ill do it for you on the computer! that S_9_= will wreck your engine, but it added 2 HP hell ill try it! I will not lie about my #'s. there are a few ppl that will lisiten to what im saying so anyone who doesnt belive me thats fine!
jared

[stewart]

we have been using the programed info from dyno jet they  go on line and take over your computer controls  we run the factory 14  47 gear sprockets  and have been using 3 third gear since its the closest trans gear to 1  to1 dyno jet has the kx  500 in its programing when you set up the tests  ,,,,larry i have used both methods of testing ,,i think a dyno is a  way to compare  one pull to the next pull and find a  change either up or down ...in dynoing car racing engines   i have seen the battles of dyno numbers rage for years one guy dyno s his one place then another place has a higher or lower number ,,we have been very attament about finding the best ways to measure incress or decress in power

[stewart]

Which method are you using?

we have used both methods a number of times larry ..as i am always looking at all options  in both testing and real world  useful power  and i think of a dyno as a tool like a dial indcator or 9.16s wrench,,

[stewart]

i wanted to say the numbers i see varying between ,,,, rear wheel drum rpm horsepower,, and inductive at the plug rpm readings.. do vary but the amount is small////compared to the change in drive train loss percntage   numbers,, that can have an effect on outcome reading ,

[Larry Wiechman]

i think a dyno is a  way to compare  one pull to the next pull and find a  change either up or down ...in dynoing car racing engines   i have seen the battles of dyno numbers rage for years one guy dyno s his one place then another place has a higher or lower number ,,we have been very attament about finding the best ways to measure incress or decress in power

I hear ya there! Takes a sharp dyno operator to get good repeatable data using a strict A to B to A test method. Comparing numbers with some other dyno means nothing.
 
Larry

[stewart]

notice on this sheet from some of todays dyno testing that hp and torque readings will always be the same number at 5252  rpm ,,since that is the constant for the math to do  the horsepower calculation  which is...tourqe times rpm  divided by  5252  equals  the hp number.....as you go below 5252 rpm tourqe numbers are  up and hp is less ..as rpm is above 5252 hp is up and tourqe heads down,,,you might have to zoom in on this picture as my camera is not doing well i think i need to find some one with a camera dyno..   i took 10 shots to get a readable 1..i have a scanner now but have to get the right hook up cable then hope to have more pictures..also note this was with standard correction method  as is shown on top left of sheet

[DoldGuy]

Stewart,
Is that a real 20 HP jump in 400 RPM? Or is it a product of the crossover @ 5252?