03-02-2013, 02:42 PM
Their RPM readings are TOTALLY out...
FAR AS IM CONCERNED - THROW YOUR RESULTS IN THE BIN
That's why the results are so f*cked...
A TD04 XUD9 producing 210lbft and 125hp? Are you shitting me!!! There's no way it's making 210lb.ft at peak without making more power - we know that TD04s don't spool that quickly, so will be producing the power at a higher RPM.
If you're paying £30 for a dyno run, they shouldn't be doing anything less than laser tachoing the crank pulley or the pump pulley and doubling the figure to do their measurements... You've literally got to insist they do it, otherwise the readings are totally to shit...
You can hear with Davids car that it's revving to a SIGNIFICANT amount more than 3850 - it hits the bloody governor for goodness sakes!! If that's the stock governor, that should be about 4850RPM - the popping and banging is due to retarded timing, but I rekon that's relatively little to do with the static pump timing, that won't have helped, but the real cause is elsewhere - that'll be because it's starving of fuel seriously and is losing case pressure, losing all the dynamic timing and going to full retard poistion...
At the end of the day, the torque give or take you can take as correct if you believe their transmission losses, judging by the fact it's a Dyno Dynamics Shootout - that'll be 15% for FWD.
I rekon that the final reading given where it stops is at 4950rpm... If we extrapolate from there back I rekon it's making 210lb.ft at 3850 (2850rpm on the graph) - that's (210*3850)/5252 which gives you a reading of 153.9hp - MUCH more like the figure I'd be expecting, now that's at peak TORQUE... So in actual fact, you'll find the horsepower carries on a bit further, even though the torque is dropping since the RPMs are increasing...
At 4300rpm (3300rpm) it's making about 195lb.ft torque... Again (195*4300)/5252 = 159.6HP... Sounding much more like it now?
This is the EXACT reason Chassis Dynos are TOTAL bullshit, people DO NOT understand the correlation between RPM and power...
Later when I can be bothered and I'm less hungry, I'll try and replot that graph in Excel as best as I can... Basically read everything 1000RPM up and then recalculate the power on top!!!
FAR AS IM CONCERNED - THROW YOUR RESULTS IN THE BIN
That's why the results are so f*cked...
A TD04 XUD9 producing 210lbft and 125hp? Are you shitting me!!! There's no way it's making 210lb.ft at peak without making more power - we know that TD04s don't spool that quickly, so will be producing the power at a higher RPM.
If you're paying £30 for a dyno run, they shouldn't be doing anything less than laser tachoing the crank pulley or the pump pulley and doubling the figure to do their measurements... You've literally got to insist they do it, otherwise the readings are totally to shit...
You can hear with Davids car that it's revving to a SIGNIFICANT amount more than 3850 - it hits the bloody governor for goodness sakes!! If that's the stock governor, that should be about 4850RPM - the popping and banging is due to retarded timing, but I rekon that's relatively little to do with the static pump timing, that won't have helped, but the real cause is elsewhere - that'll be because it's starving of fuel seriously and is losing case pressure, losing all the dynamic timing and going to full retard poistion...
At the end of the day, the torque give or take you can take as correct if you believe their transmission losses, judging by the fact it's a Dyno Dynamics Shootout - that'll be 15% for FWD.
I rekon that the final reading given where it stops is at 4950rpm... If we extrapolate from there back I rekon it's making 210lb.ft at 3850 (2850rpm on the graph) - that's (210*3850)/5252 which gives you a reading of 153.9hp - MUCH more like the figure I'd be expecting, now that's at peak TORQUE... So in actual fact, you'll find the horsepower carries on a bit further, even though the torque is dropping since the RPMs are increasing...
At 4300rpm (3300rpm) it's making about 195lb.ft torque... Again (195*4300)/5252 = 159.6HP... Sounding much more like it now?
This is the EXACT reason Chassis Dynos are TOTAL bullshit, people DO NOT understand the correlation between RPM and power...
Later when I can be bothered and I'm less hungry, I'll try and replot that graph in Excel as best as I can... Basically read everything 1000RPM up and then recalculate the power on top!!!
