November 2008

Sunday, November 23, 2008

DynoTech : December dyno schedule & other stuff

12/1 Rob Schooping dyno tuning Skidoo triple 1200 stroker lakeracer this one was a hermaphrodite, but not as powerful as the typical HTG1200 triple
12/2 private session all day, cameras off

12/4 Mike Martin MPI SC Nytro one more time with bigger fuel pump. Mike did a complete custom fuel system on his own to get fuel flow to match the big air flow
12/5 AM open    PM Deeder better have his parts now. Deeder got his stuff, still making 300 plus, but a small piece of cylinder casting popped loose between bore and oring. Back to the plater.

12/8-12/14 Dyno Nightmare Week--a dozen AmSnow Shootout sleds to certify monday-wednesday, live on DynoCams, please let me catch at least one cheater (!?)... then I pick up stock and mod trophies, head for Old Forge on Thursday but must stop at Syracuse airport to pick up AmSnow Ed Mark Boncher who will be expected to chip in for gas and road beer, Shootout #19 (don't know roman numerals)  on Friday at Woodgate.

12/15 Bill Swartz several CS mod engines, live on DynoCams

12/18 Anthony F F7/8 twin pipe Boondocker tune create two perfect maps one for 87 octane 10.5/1 163hp, 93ish octane 12/168hp
12/19 Mike Scarcella cancelled
12/21 Allen Miller Bender Viper cancelled
12/22 Kyle Cook, Rob Schooping two mods cancelled due to weather
12/26 Jeff Sherlock w/ mod F1000 and new Jaws pipes, Top Gun Dave Dillenbeck trying new high rpm pipes on his Cutler F7/10  Jeff's dyno session was shortened by a combo of a failed Boondocker box and/ or an air lock in his cooling system (air pocket above comb chamber = detonation with safe A/F ratio). He had just come off Jaws' SuperFlow dyno just like mine, with new Jaws F1000 twins, perfect  Boondocker tune and HP he wanted to share with DTR. His plan was to make some good HP then pop the head off to let me measure bore and stroke like Rich Daly did with his XP800. But before the good HP could be made, initial dyno midrange fuel flow was horribly lean, down to 17/1 and we kept stopping the dyno tests midstream to have Jeff add Boondocker fuel numbers. Adding 20 to all WOT rpm settings did almost nothing to increase fuel flow, and eventually a plug got speckled. There were also issues with trying to get dyno cooling water through the chassis and into the reverse cooled engine, possibly contributing to the detonation. The lack of fuel due to the boondocker reverting to stock fuel flow, combined with air trapped in the head = short dyno session. Jeff will fix whatever the problem is and come back again next week. But for now I can offer that the Jaws F1000 twin pipes are incredibly, very nearly as quiet as a stock exhaust. The ultimate HP delivery will be demonstrated when parts are fixed, Boondocker replaced and coolant bled perfectly, and head is removed for bore/stroke measurement by yours truly.
Dave D's day was better, but the high revving twins didn't make his F10 happy, so he went back to his original 8000rpm pipes and made more power. Tweaking on his wet N2O system (Dave had to buy a $100 hot air gun to heat his n2o bottles because he knew I wouldn't let him use a 3000 degree torch to overheat the aluminum bottles that lose much of their tensile strength at 600 degrees F) made him over 260hp with .65 lb/hphr. Will Dave's 260 HP n2o Firecat run w/ Mike Koz' 300 HP n2o F1x00?

 12/27 Mike Marpoux, SkiDoo Big John Big bore, and 09 800XP stocker

Sunday, November 09, 2008

DynoTech : Kevin Cameron on breakin friction


Kawasaki's KR250 road race two-stroke most certainly developed more power after some break-in time, but the energy argument disposes of the idea that it could be a large amount. If much power was going into making metal particles you'd see the metal - lots of it.
In four-strokes, the largest component of friction comes from the ring stack and secondarily, from the piston, the reason being that ring-to-wall oil films are very thin so the rate of shear is large. Because engines don't fill their oil with wear particles we can see that metal-to-metal friction is very small. This is especially so  in late-model stuff, which has all lapped rings. I rented a Mitsubishi something-or-other at the Atlanta airport once with 7 miles on it, and was interested to pull the dipstick after 200 additional miles of rush-hour 85-mph driving - the oil was still clear amber. Back in the old days of cross-hatch honed cylinder walls that acted as mill bastard files to shave rings into shape, the first oil change was dark with wear particles.
At lower throttle angles a four-stroke also has a lot of pumping loss, usually lumped in with friction. This is the energy used to pull a partial vacuum in the cylinder on the intake stroke. Diesels, being unthrottled, have little pumping loss, as do crankcase-scavenged two-strokes.
At idle or similarly low rpm there is an increase of friction loss from the valve train as the heavy pressure between tappet and cam lobe increasingly crushes through the dynamic oil film, leaving an increasing share of the load to be carried by the oil additive layers on the parts. As this additive-carried friction is typically 10-100X the friction of the oil film (usually of the order of .001) this can be a fair amount, and is responsible for much of the rise in friction at very low revs. During break-in this is probably a source of some excess friction. Some anti-friction agents such as tricresyl phosphate (the TCP of story & song) act as polishing compounds. As they react with the metal surface they form friable phosphides, and concentrated friction may rub some of this off, taking some metal with it. I have often seen power gears that were fairly rough-looking when new assume a much more polished, finished appearance after some hours of operation.
OIl film friction rises steeply with rpm, so the friction loss curve is a "bucket" - high at the extremes and low in the middle.