Combat Wombat max HP or torque

[hodakamax]

Well the drag race method of comparing two bikes WAS fun but not inaccurate. My team mate and I actually did this with hundreds (yes hundreds!) of runs. The two race bikes were equally maxed out (so to speak) and rarely differed more than a half a bike through the gears. After several runs we would exchange bikes to rule out rider differences. First gear starts were easy launches to try to get even starts. Actually it only took a few runs to see which bike was pulling the other. If you were testing different pipe designs you could even switch the pipes and go through more runs. Same situation on a track, it was always apparent which bike was faster or had more acceleration on the straight with the same gearing. Not rocket science but did work to sort out which modifications were working and which was not.

yet another tale from the past

Max

PS--I know that everyone didn't have access to a drag strip but we were fortunate to live on the edge of town on a main road that intersected a county road. The tests were all done there and at the time the local police just told us just to not interfere with traffic. Times were different then!

[junker2k]

I ONCE asked Harry when I picked up my bike, how much hp the bike had over last weeks bike. After getting a half hour talking too, the bottom line was did the bike start? (yes) Could you pass everyone on the track?(yes) Did you win? (Yes) Then why in hell do you care how much hp you have. I never asked again, because it just did not matter.
Jack K

[DGardner]

Talked to Tim at TTR and he will dyno all the models that Roger and I can come up with. Roger has a 93SR and I have a 97SC. Roger is looking for a ace90 and a ace100. I think it will be fun just to see what we come up with.

[hodakamax]

And Jack, how true, the bottom line was to beat the competition!

Max

[Zyx]

Most times I raced, I raced against myself. 50 mile cross country races were rarely head to head. It was about keeping pace and focus, and doing better today than I did yesterday. On the other hand, at the scrambles/moto in Athena this year I had the opportunity to plan a pass two laps ahead of the need for it, and when the moment came, a hundred feet from the finish, I pegged it and left it there. And passed the guy I had been following through every curve for most of the race. It was fun knowing ahead of time I had the faster bike, but not so much fun knowing he cornered better than I did.

Max, I suppose if the two of you did it often enough, and traded bikes, it was about as much science as one would need. We used to do much the same, for the same reason. But you see, what you were doing was taking out as many variables as you could, so there was method and science in your work. You do what you can with what you have.

The idea of getting dyno runs on as many models of Hodaka as you can muster is a good idea. The more information you have, the better you can judge it's accuracy or at least it's usability. You may even be able to get a sense of how much loss there is in the drive train. My guess is the loss is between 10 and 15%. That is, rear wheel is about ten or fifteen percent less than crankshaft. So, if you record 8 rwhp, the crank hp would be around 9 to 10 cshp. If your rwhp is 15, your cshp is around 16.5 to 17.5. I think this kind of relationship makes more sense than assuming a 33% loss, or even 26%. This is only an opinion, based on supposition and experience, and not science. If you can find a way to identify actual loss through a typical Hodaka transmission, let us know.

[ossa95d]

I truly enjoy these conversations and discussions, and I really appreciate the work that has gone into these dyno tests and results. I spent a great deal of my short time as an aerospace engineer testing turbofan jet engines on a stationary dyno and reducing the data from those tests. I have to respectfully disagree with the idea that the horsepower loss through a drivetrain would be a consistent percentage of total horsepower from one machine to another. The quantifiable horsepower loss though any similar primary drive, transmission, drive chain, and rear tire would be fairly constant at a given RPM regardless of total horsepower. Having no argument with this constant being represented as 3 to 5 horsepower at 7000 RPM (Seems like reasonable number) that loss would be 30% of the output of a 10-15 HP engine and 2.5% of a 200 HP engine. There is no way a well functioning drive train is going to rob 60HP form a 200HP bike. Put another way, if you improve the performance of an engine over stock nearly all of the horsepower increase at the crankshaft will also be realized at the rear wheel. Keep the info and the conversation coming!

[hodakamax]

Hey Ivan, Thanks for your input. I'd really never considered how much power the drivetrain used until this discussion. To me it's now clear to me (and obvious) that the drivetrain drag is not a function of the power of the engine. If all the engines tested used the same drivetrain, the drag would be a constant. I suppose that different RPMs could affect the drag of the drivetrain, for example, the loading of the bearings, but for all practical purposes I think this to be true. These discussions are fun and good for the brain indeed!

Max

[Kels]

I would agree with Ivan.. Of course, how well the clutches are "hooking up" and how smooth the tranny is working would be factors... But I suspect the losses would be in the 25-3-% range on the 125 engine...too bad nobody has a dyno that can attach to the crank.

At the end of the day.. Doug's engine seems to be producing a significant amount more HP than a stocker, which was his goal.

It does not require to be wound out between shifts and can be lugged like a Japanese bike (something that was not possible before).

Also, it is 100% streetable for long distance... It runs on pump gas and heat is low..

There is MUCH more power to be had in a form that would not be as "friendly" on the street for 5,000 miles running a year like Doug does..

It is important to realize that this engine is used everyday for long distance running and must be able to run on low octane pump fuel.

[Charlie R]

Doug, thanks to you, Roger and Tim for taking the time and initiative to provide us with the best results we have been provided to date. I appreciate your humor. Some of us here tend to get "over-wound" regarding topics so an attempt to interject some levity is appreciated, by me at least. I actually spewed coffee out of my nose at a couple of your posts.

I raced and wrenched for a USAC midget team for a few years and have a real life example of how we could have saved over 18,000.00 on one engine alone had we not used the dyno results primarily when making our decisions for which engine builder we were gonna go with. It's rather long but will share it if anyone wants to hear it.

Anyways, thanks Doug and friends!