Tuesday, August 02, 2011
Coming next: a $2200 coolant flowmeter to integrate into our SuperFlow 902 data acquisition system...
I subscribe to Cycle World magazine primarily to read CW Technical Editor Kevin Cameron’s (KC’s) monthly TDC (Top Dead Center) column. Recently he did one on turbulence, which relates in part to the "Bathtub vs Shrinkwrapped heads" info he provided us (scroll down in the blog section to read that). So I asked KC to provide us an update article to explain turbulence and its benefits, both in snowmobile combustion chambers and cooling systems. That five page article is now posted on our subscribers' pages.
There are times when we question a stock sled's ability to properly cool itself, much less one modified with higher than stock power levels. Last year, Boyesen sent me a billet water pump impeller for a Polaris twin that I would like to test. Joe Dispirito has made some billet thermostat housings that he says reduce Polaris engine temperatures in the field. This new coolant flowmeter will enable us to assess both, and estimate the velocity of the coolant flow, in ft/second, through the heat exchangers. The flowmeter is a short 1” diameter turbine with a long cable which will enable us to test coolant flow on the sleds, with coolant flowing through the sleds' heat exchangers.
And how about Kevin Cameron's opinion of the most ideal, highest power, highest turbulence producing squish clearance at .027" even on two-stroke roadrace bikes that endure minutes at WOT? Certainly controversial for those of us who are used to seeing .050-.060" squish clearance in sled engines modified for maximum power. Sure, there are lots of powerful engines winning races with .055” squish. But couldn't all of those engines make even more power with pistons .005" from kissing the heads, and squish band width and timing optimized on the dyno? From what I've seen here, yes!
There are some 30-odd articles by Kevin Cameron in our archives. When you scroll down the subscribers pages to the 37 scanned copies of the early printed DynoTechs, you will find in most of them a technical article (TCD-The Cellar Dwellar) by KC on all things two-stroke and snowmobile engine performance related. Many young sled hotrodders who are DTR members make a mistake by ignoring the "old stuff". But in those old scanned issues in the archives is a treasure trove of meaningful information. It may not be too exciting reading about obsolete 650 piston port triples, 110 HP Wildcats, 75 HP Phazers, etc but most of what we have an understanding of today was learned back then, and documented in those scanned printed issues.
We've all been fortunate to have Kevin Cameron to help explain things that have baffled and bewildered us ever since we began testing and printing results back around 1988. Even today, just when we think we "know it all" (tongue-in-cheek), something will come along that needs explanation by KC and he still takes the time to help us to figure out what's going on. Turbulent flow of air and coolant is a great example of that.
I became acquainted with Kevin Cameron about 24 years ago. Kevin had built a Honda Hawk roadrace engine for a New Englander named Ed Abdo. The mods included a set of Keihin flatslides Kevin had converted to downdraft operation with stock floatbowls machined off, and remote floatbowls added. Ed had been unable to get the engine to run cleanly--too rich or too lean everywhere. In 1987 (before the invention of the DynoJet inertia bike dyno) C&H Dyno Service (that's what we called it before it became DynoTech Research) was one of the few dyno testing facilities that could accommodate a motorcycle engine in the bike’s frame using splined trans output shaft (never call them countershafts!) adaptors to connect engine to the dyno absorber. So Ed Abdo came here out of desperation. He showed up here with a shoebox full of every tuning component Keihin made for those carbs, and Ed and I dyno tuned this gurgley thing--madly swapping pilots, air jets, needles, tubes, mains etc on those custom carbs until they worked perfectly, and made lots more HP. At the time, I think Kevin was most impressed because the changes we made to correct the mixture on those carbs in some cases contradicted the Keihin carb manual! Two monkeys with an instrumented dyno, and lots of tuning parts can create excellence! But we kept at it until we had relative perfection. And the actual airflow/ fuel flow data was as intriguing to KC as well as the output shaft torque and HP.
Kevin Cameron subsequently agreed to become “Technical Editor” of my DynoTech newsletter, providing engine-related technical info that helped educate us then-novice sled tuners. About the same time, he became a consulting engineer for Texas high schooler Colin Edwards' (who grew up to be two time world Superbike champion and now races for Yamaha in GP-1) motorcycle roadracing team, which was financed by actor Woody Harrelson. The race team and Kevin came here several times to test and tune incredible Yamaha TZ250 (90ish HP at the output shaft) bikes. Those were enjoyable, educational (as much for me as for them!) times.
Over the years, Kevin would occasionally even consult with me on particular issues about what I might have experienced on my dyno. He appreciated my opinion on things, since he suggested that I had a unique perspective--virtually everything I knew and at least partially understood came from actual dyno testing--not clouded by preconceived notions and opinions. I was honored to receive an acknowledgement in KC’s 176 page “Sportbike Performance Handbook” (MBI Publishing) in 1998.
Read Kevin’s piece on Turbulence, and engine builders please experiment with those squish bands! It should be done methodically on a repeatable dyno with copper tube connected to the engine to listen for knock. There’s surely hidden HP there! It’s great fun when a racer comes to test with a box full of chambers and a means to quickly change timing. Stay tuned this season forward as we examine and document the advantages of high velocity in allowing/ creating higher power levels in both trail and race engines.