Saturday, June 20, 2009
Email from Jim C to Kevin Cameron:
This is the latest "turbo crank" deal, being aggressively marketed to snowmobile people now. Turbo crank mods are cicada-like, coming around, being promoted and talked about every few years, then going away.
Is this like the deal that [then TX highschool roadracer Colin Edwards' race team manager] David Herold tested here at DynoTech with you [as team performance consultant] 20 years ago on the [90 HP Yamaha roadrace bike] TZ250? I recall you saying at some point [prior to the dyno test] it couldn't possibly provide meaningful power or airflow boost because the crank wheels were traveling well below the speed of sound [even at 12,000 RPM]. [The stock crank and "turbo" crank as you predicted delivered identical airflow CFM and HP].
The important variable in the design of a centrifugal compressor is its tip speed - the velocity of the impeller tips. The impeller accelerates the air molecules to tip speed, and compression takes place as this energy of motion is converted in the diffuser into the energy of pressure. There is a strict elationship between the two.
Compute the "tip speed" of the crank-become-a-crude-centrifugal impeller as circumference in feet times revolutions per second. If the flywheels are 5" diameter the circumference is about 16 inches, or 1 1/3 feet. If crank rpm is 8500 then revolutions per second are 142. Multiplying the two together gives us a "tip speed" of under 190 feet per second.
Referring to my handy little table "Pressure of Air on Coming to Rest from Various Speeds" I find that an adiabatic pressure rise (adiabatic means with no exchange of heat) of 2% results from 100% efficient operation. Since the crank flywheels are not equipped with a diffuser as centrifugal compressors are, it is unlikely that much of this 2% would appear at the bottoms of the transfer ducts.
To get one atmosphere of compression requires 100% efficient recovery from a wheel with a tip speed of 1200 fps.
If these things have any effect at all, it's most likely on fuel vaporization.
Thursday, June 11, 2009
6/6 Sat Dave Waters/ RJ Overholt KTM 950 Vtwin flattrack bike w/ required inlet restrictors, Ron Jewell ported heads those nascar-like inlet restrictors hurt airflow and HP, and require vastly different jetting to achieve max HP--we got that perfect, but we can't tweak timing since the ECU is fixed, and the flywheel/ pickup are buried inside several layers of engine case castings...working on timing access
6/13 private grass dragracer tuning session, Cams off
6/15 Maynard Priestly Honda 450 flattrack racer tuned to max HP, wish we had a Keihin slide rule like Mikuni so he can be at max HP jetting regardless of weather
6/15 late am neighbor Todd w/ VRod for PCIII tuning for max HP cancelled
6/18 Justin Gee Polaris PS800 pipe testing took a few hours to cure erratic fuel flow, create max HP jetting and timing, then selected the best overall set of pipes...
6/22 Bill Capizzi two Cat grass race sleds results here are private
6/23 Bill Capizzi two more Cat grass race sleds results here are private
PM Rob Schooping HTG PS1000 SkiDoo on motor plate after optimizing timing and jetting 275 Hp with a moderate 14-1 compression ratio
6/24 AM DynoPort Rich Daly converting his 180hp single pipe XP800 to big power with Nitrogen
assisted N2O, NANO plus Nitrous Express kit the NANO add-on gave us constant 900 psi regardless of bottle temp or amount of liquid left--tuned first to 184 HP max high compression (yes 800cc single pipe, I measured the bore and stroke myself), then detuned compression and timing to 170 HP then added over 100 HP with no clicks of deto using 120 octane gas. The NANO makes n2o tuning consistent and easy.
6/25 Jim Cooper one more time trying to resolve cantancerous fuel flow issues so he can run 1/4 mile without leaning out on top new rebalnced crankwheels by some outfit in Canada, smooth now excellent smooth fuel delivery to CS56 carbs even with solid mounts, mysteriously a bit less HP than his old buzzy crank but having 270hp for a full 8 seconds is better than having 285hp for 4 seconds then tailing off to 250 or worse because float bowls are running dry!
6/25 pm Tripod Dan and Danno PS800 trying for a reasonable HP curve with compression dropped to 18/1 (was 20/1 last time with awful spikey detonating results). came with less compression and new MSD set way too far advanced, preignited and frosted a plug with no clicks of deto, will come back after repairs are made.
6/29 competitive Cat grass dragracer w/ two sleds, cams off
6/30 Jason Owen two mod cats Jay and his pal Trevor had cams off, struggled with a bad EFI controller, will tune another day
7/1-7/2 pro snoX mod engine testing cams off
7/3 Friday Dean Sutter dragbike w/ Polaris mod sled engine installed cams off profession tin-knocker Dean had a slick set of hand rolled and welded pipes w/ sliding center sections and sliding stingers, optimized carburetion then while rolling timing back and forth with an external adjuster, tweaked CS length to max HP then got best HP with stingers slid inside the rear cones to create internal stingers...
7/6 Monday Jim Cooper hoping to find lost HP Jim found awful leakdown, .018" piston to wall clearance so to see if that was cause of low HP, back to DTR. Picked up another 10 hp to 280 plus with fresh topend, still a tad lower than best HP with old buzzy crank but surely good enough to be competitive on asphalt. Next is a trip to Chukaroo for a day on his eddy current track dyno for clutch tuning.
PM Dad & tripod Dan, PS800 one more time w/ less compression and MSD. Starting today with well-retarded timing, worked our way up to 229hp with a broad plateau of HP on this HTG stroker 800. It's always good to start with retarded timing and work our way up. 18/1 compression is still wickedly high but here it seems like it will be good for 5 second drag runs.
7/7- 7/14 more pro SnoX engine testing cams off
7/15-16 gone fishing, Sean Ray dyno tuned Shane Tottens PS1000 while I was gone. Bigger carbs, bigger HP.
716 pm open mod grass dragracer on the way to Syracuse dyno at 8pm (time and a half?) cams off
7/17 AM Glenn Hall D&D open mod Z1 as(H)phalt racer tuning
Late AM Stan PTM dialing in big twin Cat with massive N2O.
since PTM Stan had D&D power on his F1200 in F7 chassis asphalt sled, Glenn wanted to lend a hand to help optimize--so Stan went first, tested higher rpm pipes which werent optimal for n2o, then before we could get perfectly dialed in with low RPM pipes and boondocker n2o we lost cylinder fire on #1 with perfect piston, spark, reeds OK. Stan;s engine vibrated badly from the start, I attributed that to solid mounts but it turns out the crank was out many hundredths--enough to shake the back of the sled several inches to the right each dyno test. I goofed because I should have looked at crank runout after the first test but did not. so it was bad to start and maybe got worse as the day went on. The good news is stan has a way better Boondocker tune than he started with but the bad news is he needs a crank job.
Glenn's D&D rear drive Z1Race asphalt sled was comparably smooth as silk with the same 1.75" dyno drive shaft. Tested turbos/ Ypipes, timing and fuel tuning. With the big turbo and icewater/ air intercooler we tweaked boondocker to 429 HP when it was apparent that the fuel pump was maxed out (zero return fuel from bypass regulator). Bone stock bottom end.
7/18 Custom handgun builder Dan Bedell, Honda VTX1800/1938 big bore street/ ET drag bike w/ N2O
7/20 Yamaha flatrack racer on bike dyno
7/21 Yamaha Banshee dragracer w/ custom billet 835cc engine, on 901 shaft dyno Greedy Marty is back again from Eastern PA with all new quad-long chromoly tube chassis and even bigger engine. Last year I made a custom long 1.25' tubular driveshaft to get from typical quad's output shaft spline to the dyno to allow the quads to be strapped onto the dyno table without removing left side wheels/ tires. I didn't think about my skinny driveshaft as we tweaked timing/ fuel all the way to 175hp and 100 lb/ft. But the custom billet Banshee monster engine is geared 3/1 from primary to countershaft to output shaft in high gear which means we were twisting that skinny shaft with 300 lb/ft of torque. Smooth as silk.
7/22-7/30 Pro SnoX race engine testing