Dynometer test configuration - DCT

[dduelin]

A while back I wanted to place my DCT on a dynometer but unless the front wheel is turning the DCT will not shift out of first gear, which prevents a dyno run. It's not that important to me so I forgot about it. When I rode the demonstration NC700X DCT at Bike Week I got to thinking about this again. On the demonstrator the front wheel is clamped and secured to the demonstrator frame. The rear wheel is free to turn a free-wheeling weighted drum so you start the bike, put it in D or S and let it run up through the gears. The front wheel is obviously not turning in this configuration and yet the DCT operates normally. I'm guessing the PCM uses ABS sensor data to to determine whether or not the front wheel is turning. Do you think it's as simple as pulling the ABS fuse or power supply to defeat the system?

Has anyone ridden their ABS equipped bike after pulling the power supply to the ABS?

 

[670cc]

I don't know much about dynamometer operation, so my question is, what difference does it make whether it shifts out of first gear? Is this some limitation with the dynamometer, that it needs a certain wheel RPM to operate? The engine on the bike would produce the same peak torque at its peak torque RPM no matter what gear it's in. And then the horsepower can be calculated from that.

 

[yearroundrider]

I have not pulled the fuse but I did the error abs procedure where you start the bike put it in gear, have help getting off and keeping the bike steady, put it on its centerstand and rev it in first gear till about 22 mph on the speedo. The error message popped up and I was able to ride on with the abs disabled. I know it's not the same but it's got to be somewhat similar.


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[the4Dman]

A while back I wanted to place my DCT on a dynometer but unless the front wheel is turning the DCT will not shift out of first gear, which prevents a dyno run. It's not that important to me so I forgot about it. When I rode the demonstration NC700X DCT at Bike Week I got to thinking about this again. On the demonstrator the front wheel is clamped and secured to the demonstrator frame. The rear wheel is free to turn a free-wheeling weighted drum so you start the bike, put it in D or S and let it run up through the gears. The front wheel is obviously not turning in this configuration and yet the DCT operates normally. I'm guessing the PCM uses ABS sensor data to to determine whether or not the front wheel is turning. Do you think it's as simple as pulling the ABS fuse or power supply to defeat the system?

Has anyone ridden their ABS equipped bike after pulling the power supply to the ABS?

In the 20 seconds I have been thinking about it. I'd make a 2nd mount on or near the rear wheel encoder and interval disc, and mount the front encoder on it (or a spare one with a long extension to the front encoder connector) to read the rear interval disc at the same time. That way both encoders see the same intervals.

Just a guess... but sounds like a fairly easy hack, and you wouldn't be messing with the CPU or any code or any (read expensive) real electronics. just need a spare encoder sensor and some wire and a way to mount it temporarily

I think it's more than just ABS, I think I read that if the 2 wheels are spinning at different intervals, the engine shuts down, it thinks there's a crash.

I could be wrong....often am, just ask my wife.....

Pete

 

[dduelin]

I don't know much about dynamometer operation, so my question is, what difference does it make whether it shifts out of first gear? Is this some limitation with the dynamometer, that it needs a certain wheel RPM to operate? The engine on the bike would produce the same peak torque at its peak torque RPM no matter what gear it's in. And then the horsepower can be calculated from that.

My answer is I don't know why they can't use just first gear I just know all the bikes I've done before they use top gear or one under that. (4th or 5th in a 5 speed box, 5th or 6th in a 6th speed box). I guess that the dynometer operation may adjust the resistance of the drum to simulate load divided or multiplied by gearing. 5th gear on the NC at 6500 rpm is about 100 mph, 1st gear that would be about 35 mph and that is much easier to achieve due to gearing?

 

[ld_rider]

so my question is, what difference does it make whether it shifts out of first gear?

I am far from an expert on this but here is my educated guess:

Dynos can't measure horsepower, only torque. You can create more or less torque depending on gearing. My guess is that dyno runs are done in a gear that maximizes torque, which would usually be the highest non-overdrive gear.

The torque (twisting force) number is then used to calculate horsepower. Remember, the longer the lever (the gear) the more torque you will have. Given a long enough lever, a five year old could torque a bolt to 100ft lbs..That same child with a 8 inch wrench couldn't do it.....Levers (and gearing) magnify torque.

 

[670cc]

I am far from an expert on this but here is my educated guess:

Dynos can't measure horsepower, only torque. You can create more or less torque depending on gearing. My guess is that dyno runs are done in a gear that maximizes torque, which would usually be the highest non-overdrive gear.

The torque (twisting force) number is then used to calculate horsepower. Remember, the longer the lever (the gear) the more torque you will have. Given a long enough lever, a five year old could torque a bolt to 100ft lbs..That same child with a 8 inch wrench couldn't do it.....Levers (and gearing) magnify torque.

I agree with your points except that I believe the upper gear(s) would have the least torque at the rear wheel, not the highest. The mechanical advantage of the gear ratios in first gear would multiply the crankshaft torque and give a higher torque at the rear wheel, albeit with less RPM. Maybe the dynamometer works best at low torque/high RPM at the rear wheel.

 

[MZ5]

Higher gears put lower stress (because of lower torque) on the output side of the gearbox & drivetrain. MANY automotive ECUs limit engine (or motor, in the case of a Tesla) output in 1st & sometimes 2nd gears. That's not just for wheelspin, it's for drivetrain protection. My _guess_ is that the dyno testing in high gear is at least significantly related to that. Meaning, both the test powertrain's protection and also to avoid any ECU-enforced output limits.

It may well be that the dynos themselves don't do so well with low-speed, high-torque situations, either.

 

[lootzyan]

Isn't it an idea of dyno test to be close to 1:1 direct drive gear (5th?) when drivetrain power loss is at minimum, so the only loss sources are friction and drag, some windage when moving?

 

[bamamate]

One reason they test in a higher gear is to prevent wheel slippage on the dyno. With torque multiplication of the drive train the wheel can spin on the drum. Also you need to eliminate clutch slippage that would occur if you started in first gear.

 

[dduelin]

The Honda technical rep got back with the dealership. Seems that the diagnostic computer in this Honda shop can disable the ABS for purposes of diagnosing trouble codes so they have agreed to do this and complete a dyno run for me. I'm most interested because in the earliest days of the NC700X there were two engine outputs for the 670cc engine. One at 47 hp (35 kw) was for bikes so limited for A2 European licensing and the other at 51 hp (38.1 kw). In the USA there was conflicting information as to whether or not ABS/DCT bikes got the 47 hp engine or the 51. I'm curious..... published dyno figures have so far been on manual transmission bikes and indicate the 51 hp motor. I made an appointment for the test.

 

[dduelin]

I guess I forgot to update this thread when the dyno run was done back in May. It's official - the US market gets the 51 hp motor in both manual and DCT bikes. My average 46.8 at-the-wheel hp is in line with other published NC700 engine horsepower curves for 51 brake hp manual transmission bikes (~46-48 rwhp variously). The tech used Honda diagnostic software to enter a diagnostic mode then we wheeled the bike onto the dynometer. The test was done in Manual mode in 4th gear as a roll-on from about 25 mph to about 80 mph.

 

[Mi_ka]

Just for comparative reference:

A guy here with an EU manual NC700X had inconsistent consumption troubles
so I sent him to a friendly shop so they could verify lambda=1 closed loop operation at cruising speeds (..which we did as the bike was measured to be functioning 100% OK so most probably that large rider was hovering in the rich open loop territory on the highways all too often causing the consumption problems).

As of this, I have the following dyno chart of a completely stock EU manual machine on a FUCHS dyno that also measures transmission rolling losses and calculates under load friction and inertia losses as well reporting HP numbers on the crankshaft with pretty good accuracy (from my general past technician experience). The test was done in 6th gear which is ok to compare since this particular dyno "sees" the different losses depending on gear used and does pretty good approximation on expected power at the crankshaft takeout.