Q&A Forum
Hi all,
I finished the restoration of a Cartec inertia dyno, 2wd, twin 240mm roller, same as the old DimSport inertial dyno.
RPM pickup is the 4-tooth wheel from Cartec with yourdyno hall sensor, planning to swap to a wheel with more tooth in the next month due some little rpm spikes sometimes.
The rollers are 136kg each, and the calculated MOI is 5,7-6,0 KGm^2.
Anyway, I'm happy with the yourdyno functionality, but I'm little confused about calibration: after some trial and error, I ended testing two BRZ, one stock, and the other one with minor mods.
I'm using 20% of power correction factor, with enabled power correction from retardation data, from all the previous tests I did.
With the BRZ 200cv engine, the sweep test lasts 5 seconds in 4th gear, with no evidence of wheel slip.
Attached some graphs:
DYNO
One run is fine with stock torque, but is very low in power.
The 4th run is overrated in torque, but nearest the stock 200cv.
Big difference is in the retardation data: most of the times i get under-zero numbers, sometimes i get positive numbers. Whe I get negative numbers, torque is ok but not power, and viceversa. When I hit rpm limiter I always press clutch and put in neutral untill logging finishes.
Is there something wrong with my setup? Or missed I something in the calibration process or the software usage during sweep test?
Thanks!
Hi there,
You must have more teeth, minimum 200 pulses per second. See https://yourdyno.com/YourDynoHelp/brake-rpm-sensors/
Basically, I'm achieving minimum pulses per second only above 200km/h? Ok, I'll correct it as soon as possible!
Is it causing the retardation problem I'm experiencing? Must the retardation data be above or below zero?
Retardation data shall be below zero indeed. But, yes, change the trigger wheel, no use in trying to get useful numbers until then 🙂
switched to a 24 teeth wheel coming from and engine, and everything is better now! Dyno runs are very close Each other with only 2-5cv differences...
HP readings are fine, with 15% of power losses and a MOI of 6.
but I keep reading almost zero power losses during retardation... is it normal?!
Tested another car yesterday and I get the same result: the numbers seems to be fine (both torque and power) but during retardation I have almost zero power losses.
During retardation I push clutch and put neutral until software finishes logging
I’m happy with the numbers, but I am worried that I’m using something in the wrong way
Hi there!
It is normal, check out the Wheel Torque and Wheel Power, there you see the losses. The Engine numbers are corrected with the negative part of the Wheel numbers.
@admin
used to see the dissipated power on other dyno: are these ipotetical numbers? Something like the 15% we put on yourdyno software?
the 4 rollers are 136kg each, 240mm diameter and 700mm wide.
I know that it’s a small MOI for a dyno, but discovered that’s the same dyno as Dimsport used to sell in the beginning... good for 200-300cv
I’ve another one like this, hope to build a 4wd linked axys next year, to achieve a total moi of 12 and dyno more recent street cars without ABS problems
Did some more cars and everything seems fine
I still get zero hp reading during coast-down, is it normal for an inertia dyno?
the only dissipated correction I get is the 15% I put in the setup options
@matteozanusso This is normal, you can see the retardation loss if you enable the Wheel Torque/HP.