steve baker
Moderator
Looks good Triton !............just curious however, looks like about a 4 HP drop from peak to 7000 RPM, is that normal ? We don't build Clones so i don't understand the power curve.
Steve
Steve
Honest hp numbers
- Thread starter Bbrstompit
- Start date
alvin l nunley
Site Supporter
I don't see that as unusual, the KT100, with a pipe, reaches peak HP at about 11,400 yet easily reaches 15,000 RPM on the top. After peak HP, with a 4 stroke, as long as there's enough horsepower to go faster (your acceleration might slow a little) the kart should be able to go faster past the peak.
steve baker
Moderator
Al, I understand your logic and agree, you always go over the peak HP on race track. Just wondering about a 4 HP drop when the peak is about 11.8 HP, IDK ?
Steve
Steve
alvin l nunley
Site Supporter
I agree with you too, but we're talking about a dyno run, not actual on track performance.
steve baker
Moderator
One of these days I will have to take the time to study the calculation program used in wheel inertia dyno machines. There has always been something that bugged me about this method and its HP calculated results.............but gotta love the repeatability!
Brake style dyno's are simple............HP = Tq x RPM / 5252
Wheel weights - 150 lbs vs 350 lbs
Acceleration rates
Deceleration - coast down HP calculation
High RPM wheel speed vs HP calculation
Inertia / RPM carry over during high RPM power loss..........
Why do inertia dynos vs water brake HP readings differ........at certain RPM levels.
etc, etc..........
Steve
Brake style dyno's are simple............HP = Tq x RPM / 5252
Wheel weights - 150 lbs vs 350 lbs
Acceleration rates
Deceleration - coast down HP calculation
High RPM wheel speed vs HP calculation
Inertia / RPM carry over during high RPM power loss..........
Why do inertia dynos vs water brake HP readings differ........at certain RPM levels.
etc, etc..........
Steve
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alvin l nunley
Site Supporter
I eagerly await your conclusions, especially the inertia/RPM question.
Freezeman
Site Supporter
The differences are interesting to think about.
It seems to me that an inertia wheel acts much like a kart and drivers weight working with a motors power out put on track. When a motor has a temporary loss of power on track the acceleration stops yet the momentum continues on. Where a brake dyno seems to work the motor more like a kart and driver does when attempting to power brake to control the speed of the motor.
alvin l nunley
Site Supporter
Back in the 70s I heard about some guys down in Southern California building an acceleration dyno. First time I'd ever heard of such a device. It worked pretty much like the acceleration dynos built today, except for one thing. While the engine is accelerated the wheel, it was also driving a small 471 Jimmy roots blower. There was no manifold for carburetors on top of the lower, instead, they partially obstructed the air intake of the dyno with a piece of sheet metal. The less restriction on the air intake, the more load was placed on the engine. Through experience, they knew how many RPMs the engine could turn on the track. By adjusting the piece of sheet metal, they could adjust the peak RPM of the engine to match the on track performance. Their instrumentation (ha ha) was a stopwatch. It was just a matter of timing the interval between hitting the throttle and the point at which the engine reached peak RPM. Make a change, test again. If the time was shorter, more horsepower, longer, less horsepower. It was that simple.
That little Jimmy blower produced exactly the same effect as wind and rolling resistance does on the track.
You know it can be calculated how much more horsepower it takes to accelerate a kart and driver from 84 mph to 85 mph. I understand it's a square function of the resistance. Someone with more math skills than me could explain that.
That little Jimmy blower produced exactly the same effect as wind and rolling resistance does on the track.
You know it can be calculated how much more horsepower it takes to accelerate a kart and driver from 84 mph to 85 mph. I understand it's a square function of the resistance. Someone with more math skills than me could explain that.
steve baker
Moderator
Wow Al, what an awesome post ! You mention the 471 blower. It reminded me of the first flow bench I built in 1974 when I used a GMC 671 blower. I used a holley dominator carburetor to control the flow and suction pressure and pitot tubes to measure air velocity, then calculated CFM, ( Q=AV ). We had a 5 HP Baldor electric reversible motor to drive it. We finally replaced this flow bench with another home built one ( much quieter ) that we still have today and still use it.
steve baker
Moderator
Big difference............Of course few share much info in this day and age
steve baker
Moderator
Our shop is always open for the serious R&D guys like you!
steve baker
Moderator
Personally Al, I think there are errors in the torque / HP calculations for inertia dyno's that very few or maybe no one understands yet.........IMO
Steve
Steve I know it’s hard to see the pic I put up but there is not a 4 hp drop I’ll look again at the dyno log but I don’t think there is not even 1 hp drop I’ll take a few pics so you can see not just only the graph but you can see the torque and hp from start of the run to the finish I’ll even show you the wheel rpm at the start of the run I think you will enjoy the ride and these are pro clones !!
It said in the Manuel that the first 500 rpm and the last 500 rpm are not that accurate . when a motor does fall hard at the very end of a pull it could be the very first onset of valve float that you can't hear. I 've worked on flow benches with 6\71 also . I built my own over then winter that was 2 things I focused on make it quieter and easy to switch from int. to ex.
Pete_Muller
Moderator
That would have been Doug Henline and myself.
Doug designed it, and he machined up the flywheel (550 lbs) at a utility company's machine shop where he worked at the time, and welded up the frame as well if I remember correctly. We got it running in 1977 or so, as I recall. It initially lived in a shop a couple of us shared in Baldwin Park, CA.
There was a fairly typical motor mount driving an axle, and that axle had timing belt pulleys that drove the flywheel and the 4-71 blower. The 4-71 had a throttle plate on the intake, and also the outlet of the blower was aimed at the engine, so the velocity of the cooling air blowing over the engine changed with speed, just like on the track. Most of us were pretty serious about enduro racing at the time, so it was easy to wear a stopwatch and just time gaps through the rpm range on the track, and then read peak rpms with a certain gear. Then we'd come back to the dyno on Monday after a race weekend, and put the exact same engine, clutch, pipe, and gear ratio on the dyno. Then we played with the secondary gearing (axle shaft to the flywheel and the blower) until the acceleration was close, then adjusted the blower gearing and intake valve so the engine would peak at the same revs as on the track. It only required maybe 2 or 3 tweaks to get the acceleration times and peak revs identical to the track numbers. The cool thing was, once that was set for say... a stock appearing engine, you could put a different engine package on the dyno (with the same gearing *it* ran on the track), and the numbers came out very close to the same as they had on the track. As long as you ran the engine, pipe, gear ratio, carb tuning on the dyno that was on the kart,, it ran the same. It is the *only* dyno I've ever used where the clutch and engine sounded and felt exactly like it does on the track.
Initially, we just timed from rpm to rpm with a stopwatch, but then I made a little hydraulic cylinder that went under one end of the motor mount, and that went to a paper strip chart recorder that Doug had found somewhere (remember: this is old school... over 40 years ago!). One person would run the engine, and the other one would just put a little pen mark on the strip chart at say 10,000rpm, 11,000rpm, etc. and we could go back and look at the torque value through the rpm range.
Probably one of the really great things about that dyno was that we could do clutch development and testing on it (and exhaust pipe testing too, of course). Acceleration times were the same on the dyno as on the track, and that included standing starts.
It was a great design (once again: Doug Henline's design, not mine). It was copied by a number of people, and there are a few copies of that dyno still floating around.
PM
alvin l nunley
Site Supporter
A different description from the one I got from Richard Burton, but essentially (some details change) the essence was the same. I saw that dyno once at Horstman's. Nice piece of work. Richard's description convinced me of the need for a dyno, which I later built. Mine was a Go Power water break. That dyno taught me a lot. Thanks for the inspiration.
Pete_Muller
Moderator
I can't remember if the one at Horstman's was the original or a copy, and I'm fairly certain RLV has one as well that they built off the original. There may be a few others floating around back east as well. There were definitely quite a few people that came by our shop to see it run back then.
I can add one more bit of info on this dyno design as well: Doug Henline's original design (at least conceptually) was inspired by a guy named Neil "Whitey" Thuesen that had a racecar engine tuning shop in east Los Angeles. I met him a few times, very interesting guy. Whitey had an inertial dyno he had built into the floor of his shop. I seem to recall it having a 1200 lb flywheel under the floor (which seems very light in hindsight). Somewhere along the way, Doug knew Whitey, and I believe that was the impetus for that first inertia dyno he designed for karting.
I can add one more bit of info on this dyno design as well: Doug Henline's original design (at least conceptually) was inspired by a guy named Neil "Whitey" Thuesen that had a racecar engine tuning shop in east Los Angeles. I met him a few times, very interesting guy. Whitey had an inertial dyno he had built into the floor of his shop. I seem to recall it having a 1200 lb flywheel under the floor (which seems very light in hindsight). Somewhere along the way, Doug knew Whitey, and I believe that was the impetus for that first inertia dyno he designed for karting.
