Location: Winston Salem, Greensboro area of North Carolina
Posts: 152
An Eye Opener When It Come To TORQUE
Here are a few things I want to discuss to get you thinking about horsepower. Again, this a theory that has a lot of debate. I won’t get into the theory of horsepower and the history of how the term was created. There are many websites that you can search to find that information. I’m going to cover how torque affects horsepower, how to understand a dynamometer interpretation of power and how it calculates power.
To start with, a dynamometer has a weighted drum that has sensors that can determine the speed of the drum. The dynamometer has a computer that has software installed that will calculate the information that is provided. I won’t take the time to elaborate on the details of how dynamometer works but, I will focus on the basic calculations that it makes.
I have to set some history of how the dynamometer came to be common place for motorcycles. This again is a very touchy and a debated subject so, I wont elaborate on the details but, I’ll give a brief description. If you want more details you can find articles on the internet and I also have an article on my website with more details. It’s titleed “The Truth About Dyno”.
The creator of the dynojet dynamometer is one person that was essential in promoting the motorcycle dynamometer. From the articles that I have read, he basically started out manufacturing and selling jet kits for motorcycles. He found that the technicians had no way to show the customer the advantages of using his product and also found that technicians had no scientific way of tuning the motorcycle properly. In short, he hired some engineers to develop a reasonable cost dynamometer to promote his jet kits.
The dynamometer basically uses a formula to calculate horsepower. All dynamometers should use this formula. Around 1972 a group from SAE “Society of Automotive Engineers” decided to create a standard formula for all dynamometers to use. This formula is the base that is being used today with the exception of users manipulating the formula. That is another subject also. The formula created by SAE is: Torque multiplied by RPM divided by 5252.
This bring us to the subject of the article. You should be able to calculate the horsepower effects by manipulating the Torque. To show you what I’m talking about, I’ll use this dyno graph for an example.
Just a note: Ignore the spikes around 4,300 RPM. The are most likely caused by clutch slippage. The customer will be glad to put up with a little slippage for a couple of hundred RPMs when they are making 170+ Torque.
TQ x RPM / 5252
Look at the 4,000 RPM and note how much TQ there is. It has approximately 160 TQ @ 4,000 RPM. So multiply 160 x 4000 /5252 = 121.85 HP. This is very close to being correct with the graph.
Let’s choose 6,000 RPM. The TQ is approx. 144 x 6000 / 5252 = 164.5 HP
This basically proves that the calculations do reflect what is posted on the graph.
Now to get you really thinking! What would happen if we retarded the camshaft timing 5 degrees? Retard the timing 5 degrees will move the TQ band up the scale approximately 500 RPM.
Let’s calculate the HP at 6,000 RPM if it was making the same amount of TQ at 5,500 RPM.
TQ @ 5500 RPM is approx. 153 TQ, so, 153 x 6000 / 5252 = 174.79 HP
That is a 10 HP gain just by retarding the cam timing 5 degrees.
This should open your eyes in a new way in seeing how that horsepower responds to torque. When I built my motor I was shooting for a lot of TQ on the bottom end. I wasn’t much for dyno shootouts since dynamometers usually won’t have the same readings. I wanted that awesome feel of taking off and feeling the “G” Force. I’ve been accused of building a “Dyno Queen” on another forum. I didn’t have that intention. I am a firm believer in TQ not HP when it comes to these heavy bikes. After seeing the HP increases resulting for the TORQUE, I couldn’t pass up the opportunity of winning 5 of 5 dyno shootouts in NC in 2008. If I was building a “Dyno Queen” I would have used different camshafts that would move the TQ as far as I could up the band. Just think, If I had moved my TQ up 500 RPM it would have made 193.74 HP @ 5500 RPM.
I hope that this will give you a little insight when you are planning your next build. I’ll be more than happy to answer any question, if I can.
I thought I would add this video. This was just after I installed nitrous. It scared the crap out of us the first time. I was only using a .028 -.030 shot.
This is great info,
Can you adjust the cam timing on a completely stock engine? or does this info only apply to aftermarket cams etc... I have an '06' Ultra with the TC-88 (bone stock)
thanks
__________________ Scott aka Psycho
Redneck without a clue
Location: Winston Salem, Greensboro area of North Carolina
Posts: 152
Quote:
Originally Posted by unclepsycho
This is great info,
Can you adjust the cam timing on a completely stock engine? or does this info only apply to aftermarket cams etc... I have an '06' Ultra with the TC-88 (bone stock)
thanks
Crane cams offers a 4 degree gear for pre 2007 engines that is 4 degrees advanced when installed one way and is 4 degrees retarded when installed the other way. This gear replaces the stock crank gear that drives the cams. I have used several of them but I have found that they are hard to find.
Woods offers a 4 degree advanced gear for 2007 and later engines.
This gear replaces the stock outter cam gear. I'm going to ask Bob if he offers a 4 degree retard gear.
Copy and pasted from Woods website:
Quote:
NOTE: 216020+4 Advance Gear is available for these Roller Link Chain Drive Cams
I have the 4 degree advanced gear but, it was just way too much TQ with nitrous. I have had the bike weighed with me on it at 1100 + lbs and it's still hard to keep the front end down in second gear. That's without poping the clutch...just a throttle roll on.
Location: Winston Salem, Greensboro area of North Carolina
Posts: 152
Quote:
Originally Posted by unclepsycho
This is great info,
Can you adjust the cam timing on a completely stock engine? or does this info only apply to aftermarket cams etc... I have an '06' Ultra with the TC-88 (bone stock)
thanks
One thing that I didn't add that I have found during experimenting with retarding the timing is that the TQ number lowers a little. It increases a little when advancing the timing.
Your question got me thinking about something that I haven't tried.
I found a stock 96 graph on the internet
The stock 96" had 69 HP and stops at approx. 5200 RPM. If you install a 4 degree gear, it should move the TQ up 400 RPM. Using that same formula, it should have close to 84 HP @ 5200. Keep in mind that this is not exact because it will loose a little TQ when the timing is retarded.
This also means that it would be sluggish on the bottom end.
So, what if you installed lower gears in the primary to compensate for the sluggishness?
Now add a good matching exhaust and air cleaner. It's not abnormal to see an increase of 15 HP on a stock engine with the correct pipe and air filter.
There could be close to 100 HP at a very low cost.
If anyone tries this, I would be interested in the results.
Wow! all this is great, I hafta finish a project and get it sold (neet trick in this economy) then I will be able to do things to the Ultra. Reasearch and parts list has started. Thanks for the info. pipes and intake, re-map, and then the cam sounds like the direction to go. as far as exhaust, I dont always want the loud, so I may go with the "Hushers" or the other one I cant remember. the other exhaust has a cable instead of the air comopressor to close off the baffles. Exhaust is a whole 'nuther subject, so I will stay focused on the cam for now. Seems ike with a cam change, ignition timing or other adjustment may be needed.
thanks again for this info.
__________________ Scott aka Psycho
Redneck without a clue
I think it would be vey interesting to see what happens on a bike with a stock cam. I have one of the Crane sprockets on the shelf . I installed it in a TC95 in an effort to get back some of the bottom end for an owner who bought too much duration. It helped quite a bit but the bike started overheating so went back to stock and geared down.
Looking forward to gearing down a TC96 with a 6spd.
Ok 100hp with breather, pipes, efi control and 4 deg advance ??? I think the algorithm needs work.
An Eye Opener When It Come To TORQUE 
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