Camshaft Comparisons (virtual)

[DirtyErnie]

"Working From Home" has left me alone in a small room with my computer for more hours than I should be, and with a wife and kid running around the house.... let's just say looking at skinny girls is right out.

So I dusted off a Windows98 virtual machine and an old copy of Dyno 2000 and started putting in motorcycle numbers for grins. When I geek on something, I like to share it with the class.

• Airflow data is from the 'D-Port Head' thread, as a 'best case scenario' for ported XS650 flow, and reliable 'stock' airflow.
• --Honestly, this engine has waaay more airflow and waaaay more valve than it needs for 327.5cc/cylinder. At some point, I might grab pics of what the calculators over at Wallace Racing say about this engine. Cliff's Notes: stock head should push 115+Hp @ 12Krpm, ported 125 @ 13K.Maybe the calcs are a bit basic, but after playing around with D2K for a month, the heads could do it. Valve springs and crankshaft are a different story. Stock intake cross-section is about perfect for 750cc+ at 7,500RPM.
• Cam data is from various vendors and threads on here, stock info from the manual.
• Carb airflow is kinda based on some forum crawling, kinda based on some hunches, and kinda based on the curves looking like they have 'enough'. Stock carbs weren't really ever a big restriction so long as the stock mufflers were on.

D2K isn't known for being a real high-dollar piece of equipment, but seems to work fine for home-gamers that aren't depending on it to win them the championship. Absolute numbers probably don't stack up, but as a comparison should be reasonably close. The 'resonant' intakes really move power/torque peaks around, near as I can figure the 'Individual Runners' peak things in the 5K range, and I use that for the baseline. 'Tunnel Ram' peaks around 7K, will probably use this to compare the 'racing' cam grinds. Pretty sure the program is based on the old Chrysler papers from way back, saying proper ram tuning is worth about a 3psi boost pressure at the tuned RPM, and they just add that into the airflow assumptions. There's no provision for setting/calculating the tuned length of the intake runners manually (although Wallace has that calculator. Man, they have a lot of calculators)
Small-Tube vs Large-tube headers are similar to how the intakes work, just adding/subtracting torque in whatever RPM range they're programmed to.
Pretty sure both of those have good effect on the numbers because of how high the valve/cylinder volume ratio is.

• Remember, This thing is trying to find crankshaft horsepower, which we have no way of obtaining on these bikes.
• - There's a spur gear driving the clutch, a transmission, and then a chain drive before the back tire hits the dyno. Not a real efficient driveline, all things considered.
• Don't get hung up on the numbers, remember: we're comparing cam vs cam. Pay attention to the curves.

First up:

1. Stock~ish. I don't really know carb airflow to any great degree, and the 'Small-Tube Headers with Mufflers option, which eats like 5hp up top. 51ft/lb @ 5,000-6,000, 60hp @ 7-7.5K
2. Stock cam, Ported heads, bigger, open headers. The stock cam doesn't exactly suck in an engine that breathes. 56ft/lb @ 5.5-6K, 74hp @ 8-9K (marked with diamonds on the graph.)
3. Shell #1, ported heads, big, open headers. More torque everywhere, some squiggles below 3k, which I assume means the simulator thinks the engine might not like it. meh. 59ft/lb @ 5-5.5K, 76hp @ 7.5K (marked with squares on the graph)
4. Shell #1 Mis-grind I bought from Hoos ca. 2011. Gary said this batch got ground with the exhaust 5° early, so this curve may only be of interest to me. Seems a little 'peakier' than the real-deal Shell, at least in the virtual world. In the real world, I love my bike. 59ft/lb @ 5.5k, 74hp @ 7.5K (marked with triangles on the graph)

I'll do some MegaCycle stuff later, and maybe get some screen-grabs from the calcs over at Wallace Racing.

 

[Jack]

Port volume, port velocity, port shape and bowl work have far more impact on power distribution and output . If you had two heads of equal CFM #s but with different port shapes,etc for certain applications, power distribution will be influenced. The XS1, later 256 along with 447,Shell and Lillie head all have one thing in common, different port shape,port volume and port velocity. The Shell #1 cam, depending on engine package will produce between 62 to 67 HP.

 

[DirtyErnie]

You raise a very good point; airflow quality can beat airflow quantity. How a port delivers the air to the cylinder has great effect on things like swirl, tumble, fuel mixing, and can effect the burn greatly. Those details are things that could win or lose a race for you.

But D2K is nowhere near sophisticated enough to know the difference, and I'm just having a little fun seeing what it thinks different cams do in different setups. I'm using your flow numbers as a "best case scenario", because you've made them available. Thank you for that, by the way.

 

[Jack]

You raise a very good point; airflow quality can beat airflow quantity. How a port delivers the air to the cylinder has great effect on things like swirl, tumble, fuel mixing, and can effect the burn greatly. Those details are things that could win or lose a race for you.

But D2K is nowhere near sophisticated enough to know the difference, and I'm just having a little fun seeing what it thinks different cams do in different setups. I'm using your flow numbers as a "best case scenario", because you've made them available. Thank you for that, by the way.

Exactly ! There's no such thing as one head fits all applications.

 

[DirtyErnie]

But, since I'm just trying to throw cam-v-cam in a neutral, and readily accessible environment, here's Round 2 & 3!

First Up: Stock, Shell #1, MegaCycle 250-20 ("All-around street cam"), and MegaCycle 250-30 ("All-around torque cam")
First pic (Dyno2) is all four cams with the 5,500rpm~ish intake and 'small tube' headers, about what would be expected on a stock bike without mufflers, or glasspacks on the stock pipes. Loosely speaking. Stock cam is beat by the Shell and smaller MegaCycle. You can definitely see where the Shell #1 gets its reputation for torque. The bigger MegaCycle is suffering here, it wants to move more air.

Now with higher intake tuning and bigger headers. Stock cam makes a respectable showing, 3.5ft/lb delta at the torque peaks between all cams. Shell#1 again out-torques everybody everywhere below 7,500, where it falls off the cliff. The big MegaCycle grind finally gets its act together at 7500, but maybe puts 1ft/lb over the smaller MegaCycle cam.

So, that's kinda fun for me to see. Maybe I'll just leave tonight with one more. Understanding how relatively 'big' the head is on this engine, maybe it can make more power with a smaller cam...

 

[Bushyeyed1]

How about higher compression?

 

[650trader]

Computer/Internet Dreaming on bench racing without any Dyno testing is only guess work.
The project should be how to make real power with the least modifications and the least or lowest amounts of cash.
There is hardly anyone track racing and components of the past are almost non-existant not to mention the fact that
REAL Gas is next to non existant.. Who out there has the pull to have new stuff made, I do but why bother as those
who do know are shouted down by those who think they know promoting unproven mods so they can collect kudos for
their unproven work. One last thing - Riders want something they can ride that,s not a grenade.

Mike Lalonde Yamahaxs650.com

 

[Oldnwiser]

One thing about these cases is that they are about like a diesel tractor brown-lipe for durability. If you blueprint the case, choose you firing order, 360 or 277/83 have top notch mains and rod bearings of cage strength to withstand a nuclear attack (and they exist, not cheap) and the crank tacked at their weakest points and balanced, hopefully with a 533 machined and hardened to a 447 with Carrillo rods, and a turbocharger with fuel injection and tractor sleeves Shell 2nd over forging, with the turbo having a rising boost curve and running alcohol to keep it cool at 11:1 water cooling for the head. Choose your cam there are no wrong answers. Redline 11,000 rpm’s. . Boost is great and when you have a rig with good boots and all the harnesses. 250 hp 200 ft lbs and a chassis and tires for it? Naw it looses its charm. Ok the bottom of a 447 is strong. Good pistons 750 ccs 9:1 running E85 for cooling and a small turbo hidden with a rising boost curve, carbs that hide fuel injection and 90 hp and 85 ft lbs stripped down to a cafe racer that’s built right. I d think that would be about as good as it gets for a working man. Choose your timing and spot tig the crank, good balance. A couple of examples to think about, I’d like an OW-72 in a tracker. But they are even turbocharging bush- hogs these days. If it has the boots it can handle the boost.