Dyno run (2017)

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It is easy to take readings from a black box at face value, without questioning the means of calibration. To my mind, the torque reading is much more important than horsepower, because if you improve the torque, you can raise the overall gearing to go faster without revving the tits off the motor. As I understand it, most dynos these days are based on inertia, and that is related to torque. I don't understand how the distinction is made between horsepower and torque on those dynos. One thing of which I am certain - if you modify a commando motor to get more top end power, the mid-range often suffers. So the self-imposed rev limit is important.
About fuel economy - petrol is very difficult to jet for without going too rich. It also depends on how hard you work the throttle. Main jets are usually relatively richer than mid-throttle jetting.
 
Ken, the noisier peashooters on my Roadster are a set of copies (not sure of the brand, have a weld line at the reversve cone ) that i cut the small end off , removed the baffles and rewelded the small end back on.
I used these on both motors during testing, in fact ran three sets of mufflers on each motor on the dyno , no carb changes and no ignition changes to see which produced the best results.
Happy to put up with a bit extra noise to get the best out of the motor.
Race bike is a performance motor , now I run the 2 EX 1 system on that, the modified peashooters stay on the Roadster.
Hope this info helps
Regards Mike
 
I'm guessing the results shown are on a rear wheel dyno; What else is recorded besides the torque and HP figures? Has anyone tuned using an engine dyno?
 
YukoNorton said:
I'm guessing the results shown are on a rear wheel dyno; What else is recorded besides the torque and HP figures? Has anyone tuned using an engine dyno?
Click to expand...
Thruxton!

Or anywhere you see 'at the crank' figures quoted!
 
Brooking 850 said:
Ken, the noisier peashooters on my Roadster are a set of copies (not sure of the brand, have a weld line at the reversve cone ) that i cut the small end off , removed the baffles and rewelded the small end back on.
I used these on both motors during testing, in fact ran three sets of mufflers on each motor on the dyno , no carb changes and no ignition changes to see which produced the best results.
Happy to put up with a bit extra noise to get the best out of the motor.
Race bike is a performance motor , now I run the 2 EX 1 system on that, the modified peashooters stay on the Roadster.
Hope this info helps
Regards Mike
Click to expand...

If the exhaust system is stifling the motor, the performance cam won't work as intended. So opening out the muffler can help, but it is not the only factor. Changing the exhaust system can cause the motor to run leaner, so that can boost performance if it is already a bit on the rich side. A better way is to modify the exhaust, then re-jet the carbs as well as progressively advance and retard the cam timing until you get the best results. It is a time-consuming exercise and in the end you probably have to comply with the noise laws even when racing. My feeling is that the Exup system which is used on modern race bikes is more about controlling noise than it is about improving torque. If you set the bike up to produce max torque it will be noisy, so Exup removes a problem and overall performance is better.
 
Jetting is a minor task, but some guys make it more difficult than it actually is. You need to know the symptoms of lean-ness apart from plug colour. If you lower the needles until you get the cough or flat spot then raise them one . . . ? Then check that your main jets at still rich enough by doing a plug chop. I would do it whenever I did a major mod to the exhaust system. I once made a 2 into 1 which chopped 2000 RPM off the top of the usable rev range, but gave much more mid-range.
 
Fast Eddie said:
This is a pic of a run I did when I first built mine (JS1 cam, JS 10.5:1 pistons, 35mm FCRs, stock RH10 head).

You can see how my data wasn’t ‘clean’ below 3000rpm.

But you can also see how flat the torque curve is. It’s close to 50 from 3400 and doesn’t drop off until after 6000. Hence my suggestion that good twin carbs would be good on yours Ken!

BTW, the last run I did was 64.6 bhp (after Comnoz head work) but the dyno computer was unable to print out the torque graph, which is kinda annoying!


I wonder how well that will work in 40 C degree + plowing through kangaroo crap with the next gas servo 200km away ?
Click to expand...
 
I don’t know either Splatt...

Send me some kango do-do and I’ll test the ploughing.

No idea how to test the 40 degree c bit though here in Blighty !!
 
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Of course. Forgive me, I wasn’t thinking straight, too pissed !

Now, with respect to Ken (the OP) maybe we should get back to waiting for updates on his jetting changes and o2 sensors...
 
Fullauto said:
Fitting my O2 sensor shortly.
Click to expand...

I think you'll find that both useful and entertaining. I first used one a couple of years ago, first to jet a Rotax powered race bike converted to street use, and later on my 920 nitrous Norton at Bonneville. I found it extremely helpful.

Ken
 
Ken, are you ‘working on jetting’ Because the AF ratio was out on your dyno run? What are you hoping to correct?
 
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