test on a BRAKED DYNO
08-12-2008, 07:54 PM
#1
MBWorld Fanatic!
Thread Starter
test on a BRAKED DYNO
soon to install my pulley, TB .. so last week made this base dyno.
I know this is not the best season to obtain good results from our Kompressor.
result is:
438WHP at about 5000rpm, Uncorrected, 3rd gear, 163Kmh; 10.4 Psi boost; IAT 142 F; Timing +11; AFR .905 volts.
28C/82.4 F ambient temp .. and a lot of humidity.
and 312.3KW *1.36= 425HP at 6000rpm;about 200KMH; 9.4 Psi boost; IAT= 155F; Timing +14; AFR .935 Volts (higher Volts value means more rich)
He calculated also the trans Power Loss and measured the energy absorption while in neutral gear: I think this is not correct because on a manual gearbox it should be done with gear in and clutch down .. but in case of Automatic box it doesn't take into account for gearbox energy absorption !
Infact the result was a 7.5% Loss that seems to me something quite different from the usual 17-18% we read everywhere.
considering that 7.5% loss, the theoretical Crank power was 473HP @6000
or 482 corrected and 708 Nm torque.
What do you think ?
--------------
full story:
only when at the shop he explained me his dyno was not the usual "inertial" dyno but a "braked" type: this means that I would not have a graph out of a single run but he had to "build" the graph taking actual values at any different rpm levels.
- computer connected to the OBD socket for data reading
- test was done in 3rd gear because the fan could simulate max 150kmh speed (95mph)
- following 6marking points were chosen: 1500-2000-3000-4000-5000-6000 rpm.
so, first thing he calculated the corresponding speed at each rpm level.
this step is necessary because for example first run at 1500rpm and speed 47.8kmh means that at that speed the dyno will brake his drums to avoid the car's engine to overcome the stated rpm level, while keeping foot down on gas. A gauge measure the torque developed and hence corresponding WHP.
After a few moments, a second run at 2000, speed fixed at 61 Kmh, ... and so on till 6000rpm test with speed at 200Kmh.
Those couple of seconds of my engine fighting against that dyno braking seemed to me something hard or heavy for the engine
.. he said to me it is something like testing a car on a uphill route !
I remember the computer showed one time, maybe during one of multiple test he made at 4000 or 5000 rpm, the max boost of 0.75 Bar/ 10,88Psi.
didn't see anymore ... but 0.62-0.65
What I remembwer is IAT temp quickly jumped from 50 to 70C degrees (or from 120 to 160F) !!
Next time I'll ask him to do reverse: begin with tests in the high rpm range and end the session with test in the low rpm range.
I remained in that closed testing room from 9.00 till 13.00; half benzin tank gone ... at least I learned something and saw with my eyes how much heat counts for these engines.
I know this is not the best season to obtain good results from our Kompressor.
result is:
438WHP at about 5000rpm, Uncorrected, 3rd gear, 163Kmh; 10.4 Psi boost; IAT 142 F; Timing +11; AFR .905 volts.
28C/82.4 F ambient temp .. and a lot of humidity.
and 312.3KW *1.36= 425HP at 6000rpm;about 200KMH; 9.4 Psi boost; IAT= 155F; Timing +14; AFR .935 Volts (higher Volts value means more rich)
He calculated also the trans Power Loss and measured the energy absorption while in neutral gear: I think this is not correct because on a manual gearbox it should be done with gear in and clutch down .. but in case of Automatic box it doesn't take into account for gearbox energy absorption !
Infact the result was a 7.5% Loss that seems to me something quite different from the usual 17-18% we read everywhere.
considering that 7.5% loss, the theoretical Crank power was 473HP @6000
or 482 corrected and 708 Nm torque.
What do you think ?
--------------
full story:
only when at the shop he explained me his dyno was not the usual "inertial" dyno but a "braked" type: this means that I would not have a graph out of a single run but he had to "build" the graph taking actual values at any different rpm levels.
- computer connected to the OBD socket for data reading
- test was done in 3rd gear because the fan could simulate max 150kmh speed (95mph)
- following 6marking points were chosen: 1500-2000-3000-4000-5000-6000 rpm.
so, first thing he calculated the corresponding speed at each rpm level.
this step is necessary because for example first run at 1500rpm and speed 47.8kmh means that at that speed the dyno will brake his drums to avoid the car's engine to overcome the stated rpm level, while keeping foot down on gas. A gauge measure the torque developed and hence corresponding WHP.
After a few moments, a second run at 2000, speed fixed at 61 Kmh, ... and so on till 6000rpm test with speed at 200Kmh.
Those couple of seconds of my engine fighting against that dyno braking seemed to me something hard or heavy for the engine
.. he said to me it is something like testing a car on a uphill route !I remember the computer showed one time, maybe during one of multiple test he made at 4000 or 5000 rpm, the max boost of 0.75 Bar/ 10,88Psi.
didn't see anymore ... but 0.62-0.65
What I remembwer is IAT temp quickly jumped from 50 to 70C degrees (or from 120 to 160F) !!
Next time I'll ask him to do reverse: begin with tests in the high rpm range and end the session with test in the low rpm range.
I remained in that closed testing room from 9.00 till 13.00; half benzin tank gone ... at least I learned something and saw with my eyes how much heat counts for these engines.
