Horsepower & Torque

[saab9k]

yes in airplanes, i checked out in a cesna 210, consant speed engine.
It is operating in best torq rpm. Keeps you busy the first few times you fly it.

 

[FLTR2008TRIKE]

I'm going to try and keep this simple and hope I can answer some questions, To truly explain how everything Wiz mentions comes into play would take a very long writeup, don't think my hands would like it very much.

Here's my 2 cents or my twisted way of looking at the world or performance surrounding heavy bikes and trikes with traveling and poor fuel quality in mind.

I'm a Torque junkie, the simplest way to describe it is that feeling you get when you start twisting that throttle and you feel the bike or trike pull, that wonderful stretch your arms out pullpepper.

When I mentioned my twisted thoughts above concerning traveling and availability of good quality of fuel, octane and compression along with the weight of the bike or trike weighs heavily on my mind, its a balancing act. Octane is a measurement of the fuels ability to resist detonation at a given compression. As we have all learned traveling the wonderful country we can and will run into varied octane rating and fuel formulations.

Some I've come across, everyone knows good old 87 octane, then you get a bump to 89 octane, 91, 93 and in some states you may see 94. The higher the number the more resistant the fuel is to detonation. When I choose a camshaft and tune for both my dads 09 Triglide and the 10 Triglide I used to own, fuel quality was one of my biggest criteria. I did run 89 octane with 10% ethanol while out west with not a bit of problems, I believe I could have also run 87 octane and got away with it, flexibility was what I was after and what I got.

This brings me to compression, people often read and hear terms such as 10.1, 10.5:1 etc. The majority of the time people are describing what they call Static Compression. To keep this simple we will say this is the compression of the cylinder if you did not have cams installed to open and close the valves.

With the introduction of the cams to open and close the valves things change. This is when Dynamic Compression comes into play. The camshaft is your engines brain, through how far open, how long open and when they open and close can make or break a combination. The simplest way to explain dynamic compression is how much pressure the cylinder builds based on when the intake valve closes in relationship to how far up on the compression stroke the piston is. When the piston is on the way up on the compression stroke there is a period of time the intake valve is still open, this allows some of the pressure to bleed off into the intake tract, Depending how long the intake valve is open determines what your dynamic compression actually is.

An example would be the 103ci engine as it comes in the Triglide, if everything is as it should be the Static compression ratio should be in the neighborhood of 9.6:1. With the stock cams your Dynamic compression will be in the neighborhood of 9.1:1.

A way of measuring the compression is often talked about as CCP, or Cold Cranking Pressure. If you was to hook up a compression tester to the above mentioned engine with the push rods removed so the valves can't open or close you will see a cylinder pressure around 202 psi, now install the push rods and allow the cams to do their job you will see the pressure around 188 psi, this is due to the pressure being bled off because the intake valve is still open part of the way.

The intake valve closing is listed in degrees, stock Harley cams come in around 34 degrees ABDC. Now install a cam with a later intake closing you will bleed off more cylinder pressure. An example is a cam with an intake close of 40 ABDC, your dynamic compression would be 8.9:1 or a CCP of 182 which is 6 psi lower than the stock cam.

So how does compression relate to torque. The simplest way to explain it is the harder you compress the air fuel mixture the bigger the bang would be, of course a bigger bang means bigger torque. The down side to the bigger bang is increased heat and the chance you may have a fuel that starts to go bang before you want it to, this premature bang will result in the dreaded ping. Unfortunately not all pinging is audible, sometimes an engine can experience detonation or preignition without it being heard.

When choosing a cam bigger isn't always better, folks sometime choose cams based on how far they will open the valves. A lot of cams which open the valves quite aways also have very late intake closing points, keep in mind the later you close the intake valve the less dynamic compression you have, this will result in an engine which is a dog in the low rpm range. For instance using the 103 as mentioned above increase the intake close to 50ABDC and you would see a dynamic compression around 8.4:1 or a CCP of 171 psi. This is a pretty significant reduction in compression and will defiantly be felt in the seat of the pants. If you want to run a cam with a later intake close you have to have more static compression to compensate for the bleed off of the intake valve being open longer.

Of course we all want a little more performance (Or at least some do). To get more performance you have to open the intake and the exhaust valves farther. The heads on the modern Twin Cam 2006 to present will support a cam with an advertised lift of .575, this is the measurement of how far the valve is open in inches. The stock HD cam comes in with a .473 lift on both the intake and exhaust side. Once trick a cam designer will do is open either the intake valve more than the exhaust or vise versa to compensate for intake or exhaust port weaknesses, most modern bolt in cams for the newer Twin Cam engine have equal intake and exhaust opening.



With this being said, its getting late and I have a early 3:45am get up for work and 12 hour shifts, not to mention my fingers are getting tired. I'll let someone pick up and add to this little post. If I missed something or didn't explain it well enough by all means add to this, sometimes what is in my head doesn't translate into type written words very well.

Im with MSOCKO3. Im also a torque junkie. Max HP is number that you have to chase starting @ 5250rpms to see the HP# rise above the Torque #. The only thing I would add to what MSOCKO3 posted is you can also increase the torque # with displacement or stroke as well as using both to achieve it to make a big bike or trike move and accelerate with ease. But it is all going to come with a cost. Harley were originally designed as a lower rpm torque engine and still are today

Wiz your question is a loaded one, reason being the cost associated with improving the power output of the existing 103" engine is a minimum of $1000.00 if not more for someone who doesnt have the ability to do the work themselves. That number is taking into account the cost new items which include the ecm program setup such as a TTS unit, better breathing AC, labor modifying the existing exhaust headpipe and then replacing the muffler baffles or replacing the mufflers to allow the engine to breath better. Then the cost of the labor to install the items then after that then you need to pay to have the trike tuned. Add a cam the additional labor and parts and before long your almost @ 2k additional dollars

Can you save money by buying used items such as the air cleaner, exhaust and mufflers as well as doing the labor to install it yourself, yes. But its still costing some coins to do it.

I realize that HD has to meet EPA guidelines to sell what they produce. But I also feel they are 20yrs behind the automotive industry with efficiency and power output of the engines they are producing. Today's cars are running higher compression engines that get better gas mileage and still produce significantly more overall power then they did 20yrs earlier.

Why cant HD see this and do the same thing?? If you go to other Websites that engine builders chat on and talk about what they can do with these same engines that HD is producing, it got to make you wonder how is it a large corporation like HD cant yield engine power numbers close to what the small HD shops can do with the same if not better reliability???

 

[Sloufoot]

The bean counters are running the company now days. Why would you change a cash cow when it would mean investing more money onto something that is already at the top of the motorcycle price range??
If the thing didn't sell, and the people didn't just go on believing there is no other way to build a Harley something would happen.
All they would have to do is bring out a different engine, same bike and see what would happen. I don't mean a crotch rocket, but the engine only.
Everyone says they wouldn't buy a water cooled Harley ??? Fine keep the old school, but give an option of something new.
By the way my dealer says Harley is still THINKING about a oil cooled head for the Trikes in '14. But it is going to have to convince the bean counters..............

 

[FLTR2008TRIKE]

The bean counters are running the company now days. Why would you change a cash cow when it would mean investing more money onto something that is already at the top of the motorcycle price range??
If the thing didn't sell, and the people didn't just go on believing there is no other way to build a Harley something would happen.
All they would have to do is bring out a different engine, same bike and see what would happen. I don't mean a crotch rocket, but the engine only.
Everyone says they wouldn't buy a water cooled Harley ??? Fine keep the old school, but give an option of something new.
By the way my dealer says Harley is still THINKING about a oil cooled head for the Trikes in '14. But it is going to have to convince the bean counters..............

I agree the bean counters are in charge when it comes to building engines and the bikes they go in. HD's money is made off the clothing line anyways :Shrug:.

 

[Sloufoot]

I agree the bean counters are in charge when it comes to building engines and the bikes they go in. HD's money is made off the clothing line anyways :Shrug:.

Yep,,,, I go in around March & buy next years coat !!:Trike1: