Torque/HP
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Road Master
Joined: Oct 2008
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Torque/HP
Is there a difference between individual cylinder tq/hp and rear wheel tq/hp? I had my bike re-dyno'd and they said I got more tq/hp then what I had, but the sheet they gave me was for individual cylinders and not rear wheel numbers like I had last time and the cylinder numbers are lower then the rear wheel numbers when I had it dyno'd last time. So just curious. I haven't done anything different to the bike since the last time except compression release valves and a cone style heavy breather vice the stage 1 heavy breather the bike came with.
Banned
Joined: Mar 2010
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From: Southwest Florida
Just because I haven't heard of something doesn't mean anything, but I don't see how it would be physically possible to measure (accurately) individual cylinder HP or Torque. A/F mixture? Sure. Stoich? Certainly. HP/Torque? I think not.
The dyno is either measuring at the rear wheel (common) or at the crankshaft (less common).
I guess they could disconnect one connecting rod and run the motor, then disconnect the other connecting rod and re-run the motor but, that woud be beyond stupid.
Dynamometers are about 90% guess-work anyway. Torque is measured, HP is estimated, etc ad nauseam. Then there's the Weather Station that calculates based on humidity, barometirc pressure, ambient temperature to give a SAE correction factor. Which, IMHO, is something of a handjob.
I saw one sheet the other day where the Weather Station was reading 12% humidity. I thought, "Where were they, Antarctica?" I saw another one that had the ambient temperature at 126 degrees. Possible, I guess. It gave a SAE correction factor of 1.26 and the owner was running around happy as proud new Father that he had 100 Horsepower. Which, in reality, was more like 80. Not bad, but not Earth shattering either.
To me, a Dyno is a useful tool if you're using the same dyno, on the same day, under the same conditions and you're comparing tunes, upgrades or whatever immediately. You walk away and come back a few days later and the same dyno might be close and, then again, it might not.
There's things out there that I haven't heard of, but measuring individual cylinder HP? I think not.
The dyno is either measuring at the rear wheel (common) or at the crankshaft (less common).
I guess they could disconnect one connecting rod and run the motor, then disconnect the other connecting rod and re-run the motor but, that woud be beyond stupid.
Dynamometers are about 90% guess-work anyway. Torque is measured, HP is estimated, etc ad nauseam. Then there's the Weather Station that calculates based on humidity, barometirc pressure, ambient temperature to give a SAE correction factor. Which, IMHO, is something of a handjob.
I saw one sheet the other day where the Weather Station was reading 12% humidity. I thought, "Where were they, Antarctica?" I saw another one that had the ambient temperature at 126 degrees. Possible, I guess. It gave a SAE correction factor of 1.26 and the owner was running around happy as proud new Father that he had 100 Horsepower. Which, in reality, was more like 80. Not bad, but not Earth shattering either.
To me, a Dyno is a useful tool if you're using the same dyno, on the same day, under the same conditions and you're comparing tunes, upgrades or whatever immediately. You walk away and come back a few days later and the same dyno might be close and, then again, it might not.
There's things out there that I haven't heard of, but measuring individual cylinder HP? I think not.
Last edited by Grendel4; Oct 13, 2010 at 03:50 PM.
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Road Master
Joined: Oct 2008
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maybe not... but the sheets show individual cylinder numbers. and the HP/TQ on them is different (per cylinder). Maybe it was the total hp/tq and it was the air/fuel mixture that was being adjusted per cylinder. My correction factor was about 5. Not sure what it was the first time. They say I gained 6 hp with the new tune, but the new numbers are still 10 hp less then what I had when it was done the first time... Not sure what the hell it all means 
Just wondering if there is something else going on in my engine that causes the loss of hp rating... guess with all the ambiguity in the numbers I won't worry too much about it, so long as it feels right and isn't dragging or making noises under load anymore...
Just wondering if there is something else going on in my engine that causes the loss of hp rating... guess with all the ambiguity in the numbers I won't worry too much about it, so long as it feels right and isn't dragging or making noises under load anymore...
Road Warrior
Joined: Jun 2009
Posts: 1,333
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From: Jefferson, Oregon
The numbers, in reality mean little to nothing except for bragging rights. Different dyno's (makes) also read different as well. SOME tuners are known to use dyno's that fluff the numbers to make their tune/work seem better than others.
I say as long as YOU feel the improvement, that is all that matters if you trust the tuner. When I went from my slip on's with wide open BCT baffles to a full 2-1 exhaust, I FELT the improvement. I didn't dyno it. I didn't have it tuned although I know I could pick up a little more, it is not worth the money right now until I do major work. But I knew it picked up power by the feel and some will discount that butt dyno, IMHO...that is all that matters especially when the post above mentioned the numbers can change daily with all the factors that can and will affect the machines.
.2
I say as long as YOU feel the improvement, that is all that matters if you trust the tuner. When I went from my slip on's with wide open BCT baffles to a full 2-1 exhaust, I FELT the improvement. I didn't dyno it. I didn't have it tuned although I know I could pick up a little more, it is not worth the money right now until I do major work. But I knew it picked up power by the feel and some will discount that butt dyno, IMHO...that is all that matters especially when the post above mentioned the numbers can change daily with all the factors that can and will affect the machines.
.2
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Road Master
Joined: Oct 2008
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thanks, agreed... It does respond better and doesn't rattle when I first step on it anymore. I am hoping it doesn't run as hot either... the air/fuel curve was way off and is now spot on, so that is what I am going to focus on...
Club Member
Joined: Feb 2008
Posts: 11,483
Likes: 39
From: Passaic County, NJ
I would be very curious to know how the dyno operator was able to determine individual cylinder hp/tq.
Dynos measure power at the rear wheel.
It would be nice to have some sort of governing body to come up with a set of standards so that dyna A could be compared to dyno B and so on.
Dynos measure power at the rear wheel.
It would be nice to have some sort of governing body to come up with a set of standards so that dyna A could be compared to dyno B and so on.
Club Member
Joined: Jun 2007
Posts: 45,429
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From: Bedford UK
We need to know more to give you a sensible answer on this. Can you post the dyno sheet for us? As SC-Longhair points out, dynos measure at the rear wheel, and correct to crankshaft speed. What we have so far doesn't make sense!
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Road Master
Joined: Oct 2008
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check, I will post both of them (the first one and then this last one). The guy told me that it was my pipes (but they were on on the first dyno). He told me he had a guy with a 110 engine with my pipes and only got torque in the 90's When I told him a stock engine gets 92 Torque he told me that wasn't correct. I told him that is what it has on Harley's web site. He still wouldn't budge said no way and told me to just ride the bike and come back if there was a problem. I will have to take pics of the sheets, but will post later today.
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