Sunday, May 10, 2015
In Summer , one of each of the aircraft types suffered fatal inflight breakups. How long has that drum remained open? It got thicker fatter and is more like the wing of the Citation Sovereign than that of the smaller CJ1, 2, or 3. I honestly dont have much prop knowledge In short, Hochschwender and Prandtl proposed that for a given air velocity, there was a corresponding droplet size to which fluid would inevitably be broken down by this process.
Traditionally tops were constructed of wood , sometimes with an iron tip, and would be set in motion by aid of a string or rope coiled around its axis which, when pulled quickly, caused a rapid unwinding that would set the top in motion.
Today they are often built of plastic , and modern materials and manufacturing processes allow tops to be constructed with such precise balance that they can be set in motion by a simple twist of the fingers and twirl of the wrist without need for string or rope. The motion of a top is produced in the most simple forms by twirling the stem using the fingers. More sophisticated tops are spun by holding the axis firmly while pulling a string or twisting a stick or pushing an auger.
In the kinds with an auger, an internal weight rotates, producing an overall circular motion. Some tops can be thrown, while firmly grasping a string that had been tightly wound around the stem, and the centrifugal force generated by the unwinding motion of the string will set them spinning upon touching ground. The top is one of the oldest recognizable toys found on archaeological sites. Spinning tops originated independently in cultures all over the world.
Some role-playing games use tops to augment dice in generating randomized results; it is in this case referred to as a spinner. Gould mentions maple seeds , celts leading to rattlebacks , the fire-drill , the spindle whorl , and the potter's wheel as possible predecessors to the top, which he assumes was invented or discovered multiple times in multiple places.
The action of a top is described by equations of rigid body dynamics see the section Rotation in three dimensions. Typically the top will at first wobble until the shape of the tip and its interaction with the surface force it upright; contrary to what is sometimes assumed, longstanding scientific studies and easy experimentations reproducible by anyone show that less friction increases the time before the upright position is reached unless the top is so unbalanced that it falls before reaching it.
In the "sleep" period, and only in it, provided it is ever reached, less friction means longer "sleep" time whence the common error that less friction implies longer global spinning time. There have been many developments within the technology of the top. Bearing tops, with a tip made of a small hard ceramic, tungsten carbide or even ruby ball sometimes wrongly believed to spin with respect to the body of the top , have been one of the biggest changes.
In addition, plastic and metal have largely supplanted the use of wood in tops. A top may also be used to demonstrate visual properties, such as by James David Forbes and James Clerk Maxwell in Maxwell's disc see color triangle. By rapidly spinning the top, Forbes created the illusion of a single color that was a mixture of the primaries: Forbes, which I witnessed in … [established] that blue and yellow do not make green, but a pinkish tint, when neither prevails in the combination…[and the] result of mixing yellow and blue was, I believe, not previously known.
Maxwell took this a step further by using a circular scale around the rim with which to measure the ratios of the primaries, choosing vermilion V , emerald EG , and ultramarine U. Asymmetric tops of virtually any shape can also be created and designed to balance. Gould lists the six main types of tops as the twirler, supported top, peg-top, whip-top, buzzer , and yo-yo. The bully and the named top in the title are challenged by Shepherd's ongoing protagonist Ralph and a so-called "gypsy top" of similar design to Mariah named Wolf.
From Wikipedia, the free encyclopedia. Several terms redirect here. This article may be expanded with text translated from the corresponding article in Portuguese. It works if anything, better than the ear muffs. This will provide clarity and understanding about how we use it. Sean Ray installed the copper tube here several years ago. The copper tube must be solidly attached to the top end of the engine to transfer the sound of deto. On sled engines the head is good, and on engines with thermostat housing, the 6 mm bolts attaching bolts there are ideal.
Arctic Cat twins have no thermostat housings on the heads, but have a larger metric tapped hole near the center of the head, said to be used at the factory for a lifting lug. That works well on SkiDoo Etec engines. Sleds with individual heads and more than two cylinders should have the lug attached to the coolant outlet manifold on the center cylinder. The sound of deto carries well through the coolant manifold, from one cylinder to another. The copper tube is routed into the control room through the wall separating it from the engine dyno room.
And of course care must be exercised when routing the copper tube through the engine compartment to keep the copper from rubbing against anything. The following photo shows how Sean took the foam insulation out of the left side of a set of cheap Harbor Freight ear protectors. Then Tygon fuel line connects the copper tube hanging in the control room and does a nice job transferring clicks to our left ear.
The headphones are only necessary on loud race engines. The control room is pretty well insulated so on most trail engines the headphones are unnecessary. On quiet engines, detonation clicks are very audible coming off the outside surface of the copper tube itself, and can be heard by everyone in the control room. This setup has saved many hundreds of pistons by allowing us to abort a test before damage occurs from detonation.
When we monitor engine knock with Arctic Cat or Polaris EFI software if we hear two loud clicks during a dyno test, both will usually pull a couple of degrees of timing and the dyno test is usually aborted since we know HP will be down. On sleds with no knock protection a click or two at torque peak is acceptable since the deto will usually subside at high RPM.
And it's a combination of rapid clicks over an extended period of time that wrecks parts. The highest BMEP mod two-stroke engines are usually octane-limited. Our ears tell us that! Four-strokes are more forgiving than two-strokes when it comes to tolerating detonation. Once the proper amount of fuel joins the N2O in the intake, the deto subsides! It sounds awful, and probably doesn't help longevity of parts, but we have learned to accept that. We still benefit from watching the real time graph on the dyno while testing.
We still can seize engines from too-lean mixtures caused by the wrong jet selection or partially plugged main jet or EFI tune, and too-often by stale, low RVP race gas that wont vaporize adequately in the combustion chambers.
Severely lean engines might not detonate. Prignition is often preceeded by detonation which scours away the cooling boundary layer of air insulating parts from degree F combustion gases. Once a hot spot occurs from, say, six clicks of deto, then quiet preignition can begin and really make a mess of things. But something like stale race gas can create extremely lean mixtures in the combustion chambers even when our meters are showing safe numbers.
So it pays to watch the numbers and the HP curve during testing. How about field testing with a short copper tube bolted to the engine? Maybe some sort of BlueTooth deal could be used with Chassis Ears inside a helmet. Then the flexible Tygon hose could be used to allow listening while riding. If someone comes up with a functioning copper tube deal for field testing, please send a picture that I can post here!
It had been used for a few years by a dirt track owner for testing gas in some class of racers who were limited to using pump gas. He recently sold his race track in the Albany NY area, and had no more use for this equipment. But we surely can make good use of this for tuning trail machines on the dyno. And once again, who but me would be interested in buying a used octane tester?
We often encounter what we think is substandard gas, and now we can be sure. This one is calibrated to test unleaded gas with or without ethanol, and if I can obtain lab certified samples of commonly used race gas, it can be calibrated to do those, too. Is the 93 octane gas really 93 or is it or 86?
This will take the guesswork out! For race engine tuning, our biggest problem is stale race gas that racers buy unwittingly. But after gas is drawn and drum resealed, more light ends will escape into the air pocket above the fuel in the resealed drum.
When first opened, the Coke is fizzy and good. But every time the plastic bottle is resealed then reopened later, more CO2 escapes into the atmosphere. And each time that happens, the fizz is diminished. How long has that drum remained open? It pays to be leery! Those are a great tool for dispensing and storing race gas in gallon drums, very much like draft beer systems do with CO2. That means our indicated. In that situation, there might be zero clicks of deto, just wickedly net lean mixtures that cause pistons to grow quickly and stick in the cylinder bores!
If the gas is stale, all of our dyno meters can be telling us all is well, zero clicks of deto means octane is sufficient, and piston s can stick and spoil our tuning session. He had bought 5 gallons of VP C16 gas from a local vendor, and Gene knew it came from an unsealed 55 gallon drum in the corner of the warehouse. It was much more pleasant charging Gene for the second tuning session. How can we prevent future issues like this? Every name brand race gas has an RVP rating.
How is an RVP test performed? Thank you KC and Google! RVP is determined by precisely heating a quantity of gasoline to Then after agitating the The higher the RVP, the easier it is to vaporize, especially in cold winter air.
Winter blended pump gas RVP is close to 15psi. Amond the lowest RVP even when fresh is C16 with less than 2psi! Trying to start a Cfueled engine in February is impossible! Sunoco Maximal which has octane similar to C16 has 6psi RVP--a much better high octane fuel for cool engine performance in winter air. If you watch dragracers "clean out" their engines on jackstands prior to the start of a race, you often hear them gurgle and pop for the first few quick blasts from clutch engagement to peak RPM.
That gurgling you hear is lean misfire from cold low RVP gas going through cold carbs and into cold combustion chambers. Once the combustion chambers are heated, more of the lava-lamp-like globs of fuel will finally vaporize, and the engine will run cleanly. The higher the fuel's RVP, the better! So let's just measure our fuel's RVP. Who in the world, but me, would want to buy a used RVP test bath? I hated high school chemistry. The only enjoyment I got from those awful lab sessions was making hydrogen bombs from dissociating hydrogen and oxygen from water then igniting those with a match..
Acetylene bombs were also great fun, especially when several of my equally deviant pals and I pooled our precisely rationed grams of calcium carbide to mix with water! My annoyed chemistry teacher would be proud, if he were still alive. The gasoline to be tested is poured into the shorter lower portion of the stainless steel cylinder, which unscrews from the hollow upped air chamber.
After the lower chamber is filled with gasoline to be tested, it is attached to the upper chamber. It holds about 20 gallons of On the dyno, we often jockey ignition timing and boost pressure levels, to enable us achieve maximum reliable power on a given octane.
Do we go with more timing and lower boost, or less timing and more boost? But what about fuel flow? What shall we do?
H-D had loaned us engineering software to enable us to tune the front and rear hotter running cylinders individually. According to the CW article, the turbocharged Buell X1 test bikes exhibited greater reliability than the normally aspirated high compression X1s.
I was leery since the counterfeit pipe had poor welds, and my suspicions were confirmed when we installed the BMP modded stock pipe I have here for test purposes and picked up 13hp. Sled 1 was autopsied back home, bone dry like sled 2.
Moral of this unhappy story is, whenever an engine is removed, then reinstalled, the first one or two tanks of gas should be premixed. They will be back, with slippery fuel in the tanks next time! This year, Tom Smith is helping out in George's absence. To those of you who are coming to the Shootout this December, please do not annoy Tom! Also if there is a hotrodded Yamaha Nytro SnoX machine that could qualify for a free tune.
AmSnow editors Mark Boncher and Mark Savage are working with us to make this possibly the most entertaining Shootout in 22 years. Or is it 23 years? Thanks to AmSnow for cutting some slack this year to make this a no-brainer for any company that deals with Cat turbo stuff! Also, any aftermarket company wanting to showcase higher power ie: Interested companies can call me at or email me at info dynotechresearch.
PCV adjustment made no difference. Don tried a new filter and fuel pressure still dropped at high revs, then he sprung for a new in-tank fuel pump and all is perfect now. If it's not too late, could "goin with the flow" [the name of the next tech article KC is writing for us explaining how fuel vaporization happens] also address sleds with EFI with injectors fitted to the throttle bodies, and maybe compare how fuel is vaporized coming out of an injector into the airstream compared to carbs like your original goin with the flow addressed?
I think that perhaps half of the hotrod sleds we tune here are EFI and we need to understand the difference, if any. I cringe when guys come here to tune sleds with bored out EFI throttle bodies. And probably those big throttle bodies with lower velocity at the same CFM do a worse job of vaporization. His previous dyno guy was making him "happy" dyno sheets but Kenny was trying to race with unhappy engines.
The Hondas and Yamahas have flat HP curves from and the Kaw peaks at ish then drops significantly as revs climb. Early on with Kenny's Ron dropped from From Kevin to Jim: British racing singles of the s started life with flat-topped pistons and compression in the 4. This allowed them to pretty much copy the hemi 2V chamber pioneered by Fiat in their GP car engine, setting the two valves at a degree included angle.
Benzole was a catch-as-catch-can mixture of benzene, toluene, and xylene - all highly anti-knock aromatic compounds. With all that new ON, compression ratios could go up.
It was a lot cheaper to make a new piston than a new head, so up, up went piston domes. Along came Harry Weslake with a little help from the tangential intake port, which converted high intake velocity into rotary swirl around the cylinder axis. THis "stored" intake energy for later use as turbulence to accelerate combustion. Now a little math - making a true hemi chamber exactly doubles the surface area of the combustion bowl, as compared with the area of a disc whose diameter is the cylinder bore.
And adding the matching piston dome did something similar to piston crown area - increased it a lot. This put piston temperature up, discouraging people from increasing bores and decreasing strokes for a long time. In , here came Pole Leo Kuzmicki, working for Norton. If you imagine the tall piston dome as being made of fudge, he essentially pushed it down, forcing it outward, closer to the head surface everywhere except where valve clearance was needed.
In those regions he brought the piston as close to the head as mechanically possible, creating OHV squish for the first time.
As he pushed the top of the piston dome down, he created room above the now-flat piston top in which intake motion could persist all the way to TDC without being damped out by friction between moving gas and close-by metal surfaces. He transformed the old, slow "half an orange peel" combustion chamber into a faster-burning, much more compact chamber that was basically just the valve cutouts plus spark-plug area.
The greatly improved Norton would have defeated the new Gilera-4s in GP racing that year, but Dunlop tires came apart on a couple of fast tracks and prevented what would otherwise have been runaway wins. Norton came back in and did the job - beating a potentially much more powerful Gilera. People today, in the 4-valve era, forget this great lesson - that just cramming a bunch of mixture up into a tight, badly-shaped combustion chamber and setting it off does not equal power.
Or, as the late Keith Duckworth put it, "People are mesmerized by airflow, never reflecting that they must burn all that air and fuel they are getting into their engines. In place of Weslake's tangential intake, he biased his intakes to produce downdraft so that air flowed from the intake valves, across to the far cylinder wall, then down to the pison, across its crown, and back up the near cylinder wall.
This, which he called "barrel motion",, is now called "tumble". The problem today is that too few builders realize there must be room in the combustion chamber for the turbulence needed for fast combustion. They just add material to the piston wherever it is easiest until they get the The piston now comes so close to the head that there really is NO combustion space.
Any tumble-generated turbulence is damped out as the piston rises close to TDC, so they are having to use very long ignition timings for best torque. In some cases, like the truly terrible 5V Yamahas, the compromise really bites, so you can have either acceleration from high compression that kills flame speed on top, causing weak peak power or top-end by lowering the compression enough to get back some top-end flame speed , but not both. When I asked Claudio Domenicali at Ducati how they have been able to shorten stroke again and again and still have competitive engines, while both Suzuki and Kawasaki have made new, shorter-stroke models that were slower than previous longer-stroke versions, he replied, "I cannot speak for other manufacturers, but in our case, we use a device like a small anemometer, placed in the cylinder.
Then we vary the intake downdraft angle and port sizes until we get the tumble motion that our experience shows to be necessary. Anyway, that is the modern combustion chamber conundrum in a nutshell. Another problem is a social one. Racers don't mind being considered "advanced", but no one like to be thought "retarded".
But where combustion is concerned, the more ignition timing your engine needs, the worse its combustion is revealed to be. Some people just can't get past the old idea that needing a lot of ignition advance is good. The reverse is true. A classic example of a bad engine is the old Honda twin of the s. Its tall piston dome and degree valve angle made it into a heat-gatherer, and air just hates to go into a burning hot cylinder.
It is delightful to be rid of air cooling at last! I have to go on another trip weekend after this, but am resolved to write the vaporization article you have asked for thereafter. I've just finished writing a "engines book", so there is more time available for other things.
Update from Jim to Kevin. I forwarded your info to Ron Jewel who has accepted that lower compression might be better if it rids the combustion chamber of much of that annoying dome. As the following graph shows, very little low end torque as lost, but torque and power from HP peak to rev limit was greatly improved that's where Kenny needs the extra power on mile flat tracks!
This is a great improvement, but the Honda and Yamaha s that RLJ mods both with smaller combustion chambers and flatter pistons at And Ron notes that his Superflow Flowbench indicates all three brand ports being nearly identical after porting is completed. So work remains to be done perhaps in the combustion chamber to copy the shape and dimensions of the others to make the Kawasakis match the performance of the Hondas and Yamahas. I had a fellow dyno tune on my shaft dyno of course a Kawasaki KZ turned into a cc NHRA pro stock dragbike that seems to have a similar dilemma.
This drag engine has a huge cast MTC head with hemi combustion chambers that are each surely chock full of dome at TDC to obtain the diesel-like compression ratio these guys run. Perhaps what we have learned from your history lesson, and from RLJ's and my own actual experience can help the ProStock bike owner find the 50 extra HP he needs to be competitive!
Thanks much for the great help, as always. The drag race guys historically want a lot of compression to snatch the tire loose and get that foot time. This may be the place where a person has to decide whether a really big project is warranted- i.
That graph is eloquent! It says what I have tried to explain to myslef and others in the past- that torque gains from compression at low revs can esily turn into slow combustion, heat loss, and fading torque at higher revs. They have also reshaped their combustion chamber while slightly reducing compression ratio. Octane cheating either intentional or otherwise seems worse this season than ever before!
Why do we suspect that? We can hear pump gas detonation on the dyno more this year than in years past! Often, when we experience unusual detonation we can buy 93 octane from another gas station, and the knock goes away. Is your state or province any different? How can we hear detonation occurring on the dyno?
Sean Ray learned about listening to engine knock several years ago at Delphi where he is employed as a calibration engineer. They drilled a hole in the control room wall, bolted the copper tube to the Hyundai engine and inserted the other end into the control room, just dangling in the air.
Sean brought the copper-tube deto sensor concept from his Delphi engine dyno cel to DTR several years ago. We now listen for detonation here and usually can abort any test before engine damage occurs.
Three or four audible clicks and we quit the test. Last season Sean and Tim Bender ran over max power dyno tests on one mule race engine for Hentges Racing, and lost zero pistons because Sean could hear clicks and abort. During similar max power testing in years prior to the copper tube, Tim used to bring a box of pistons and a jug of muriatic acid to clean the bores after seizing.
Back then it was more wrenching and less testing. This means that a few more intermittent clicks of deto can be heard and tolerated by the engine before really bad things happen. Four-stroke piston seizures from deto are rare. Instead, when continual deto makes spark plug ground straps red hot, preignition can occur which can create the worst damage! Then, instead of blowing headgaskets we might see studs being pulled out of the crankcase threads, conrods bend or break and cylinder and head gasket sealing surfaces fried into junk as though attacked by a plasma torch!
Tune those high boost engines! With proper tuning for the available octane, stock fasteners and headgaskets will survive incredible power increases! But now, after this dyno tuning session Gary can probably run his sled anywhere with any octane gas.
So adding boost, especially with no intercooler, is almost guaranteed to create knock. With psi boost, my Whipplecharged 5. The knock-induced retarded timing severely limited the power increase.
As shown in the following graph, HP is improved from midrange to top end. And note the precision of the control of fuel flow by the Power Commander.
Note that torque has not yet peaked at But if I stayed into the throttle the torque and HP peaks would surely have gone beyond 10,, totally unnecessary with a big boosted engine like his. So Gus is going to lengthen the pipes enough to bring peak power down into the RPM range. DA is a combination of baro pressure, temperature, and humidity water grains per pound of air.
Then using just the altitude half of a Mikuni Pocket Tune sliderule, perfect jetting can be maintained. Muffler testing, HiJacker testing, all with stock turbo outlet pipe. We have an all-motor class in the Lakeracer division! Also Tuesday we're doing all the Cats, plus hilldrag sleds the Michael Koz and Jeff Cerio need to sneak in for a quick tune.
Also Ron's brother Randy tuning his HO for max power on pump gas. But decent air for tuning a race bike! For long term DTR members I need to clarify the difference, and for new DTR members I need to explain the channel information in our dyno printouts, and what each channel means to us. Those are perfectly accurate.
And since the speed of sound increases with temperature, the HP peak in the field may be at lower RPM trail riders on-off-on throttle or at higher RPM lake runners or mountain climbers who might spend minutes at WOT. Complicated initially but it takes into consideration the twisting force and how quickly it can be done RPM. HP is what we need to create acceleration and maintain top speed.
STPTrq Clb-ft this is the twisting force, or torque that the crankshaft is exerting at any given RPM, corrected to 60 degrees sea level barometer But my spindly legs can only muster 3 RPM!
Not bad for a 62 year old. It takes HP to create acceleration. FuelAB- fuel flow into the engine in pounds per hour. But combining the two flow readings is necessary for computing BSFC. Polaris uses this type of system.
Early adventuresome guinea pigs including all of the current eastern US aftermarket sled modifiers and I proceeded to just tune engines blindly to max HP and beyond until engines seized. But after our th piston or so, we realized that there was a pattern to this destruction if we went too far beyond max HP. Fuel flow is meaningful information and we finally understood that our race engines would make best power at. But today, with modern race engine configuration two stroke race engines can make best power closer to.
They use high velocity, turbulent coolant flow to maximize heat transfer from hot engine parts to cold heat exchangers. This reading can show leaner than the mechanical reading if oxygenated fuel is used. The math is done by the computer and SCFM is shown. If backpressure is lower, then power might be sacrificed. But then there is less possibility of detonation-producing active radicals being packed back into the combustion chamber by the pipe s return sound wave s.
Also a 20 year old Black Magic triple made out of three twin cylinders on an old triple crankcase. Great fun for me since we haven't tuned any of these for many years! I first met Paul about 40 yrs ago when he came into my welding supply to see if he could borrow a small cylinder of oxygen. I can't recall the outcome of that adventure.
Five minutes later, the Superbee was back in my parking lot--idling on maybe seven cylinders and with the hood buckled from the exploded air cleaner. True story, with no embelishment needed!
Also doing their own muffler testing on a prepro XF turbo Hope the DynoCams will be running! 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. Certainly controversial for those of us who are used to seeing.
Sure, there are lots of powerful engines winning races with. From what I've seen here, yes! There are some odd articles by Kevin Cameron in our archives.
But in those old scanned issues in the archives is a treasure trove of meaningful information. Two monkeys with an instrumented dyno, and lots of tuning parts can create excellence! But we kept at it until we had relative perfection. The race team and Kevin came here several times to test and tune incredible Yamaha TZ 90ish HP at the output shaft bikes.
Those were enjoyable, educational as much for me as for them! Over the years, Kevin would occasionally even consult with me on particular issues about what I might have experienced on my dyno. It should be done methodically on a repeatable dyno with copper tube connected to the engine to listen for knock. Photo shows how we dyno tune quads, with measured fuel flow gravity fed from a Holley float bowl to the carbs. I like those new 50mm carbs too! Now the bike is fast. Expecting RWHP with 96 cubic inches, hence the need for larger injectors.
Here's the aforementioned dyno starter drive sysem! Now we can remotely start engines from either driveshaft. That's a Polaris sled ring gear bolted to a custom fabbed aluminum flywheel. Bring on those little vintage race engines! Below is a photo from inside the cold room, showing the three condenser units--each connected to one of the compressors outside the left wall.
Just visible behind the condenser stack is a 10" diameter air intake pipe that draws "makeup" air from the roof of the building. As the engines consume air via an insulated duct from the opposite wall to the engine's airbox inlet , replacement air is drawn in to the area directly behind the condensors.
So we've put that session on hold until we figure out what is causing the grief. We're thinking now that it is exhaust temp creating this strange loss in power after some reasonable time at WOT. The probe in the muffler may be getting up to some temperature, and then the ECU drops the power level and causes underrevving.
So could they be lowering the exhaust valves slightly to choke off airflow? At any rate, Billy has eliminated the power dropoff by advancing his ignition timing with his buds computer.
Rusty is planning to do the same with his stocker, and test it this weekend. Now, advancing the timing reduces exhaust temp the fire stays inside the combustion chamber instead of blowing out the exhaust ports, hopefully making more cylinder pressure and torque , and maybe Billy advanced his enough to heep the muffler temp below the threshold temp.
We'll know more about this phenomenon next week, and hope we can reschedule the Etec test session. When it comes to making best HP without detonation, cool engines rule. Some engines need lots of heat to run cleanly.
Among worst were the Vmax 4s with those awful racked Mikuni carbs. Those who tried running with the F thermostat removed were rewarded with F coolant temp and continual gurgling from poor vaporization. But most engines will run cleanly and happily with F coolant temperature, and will make way more power than they will at F.
If we can get that engine to run at F or even cooler, it will be a better machine. Joe from Boyesen Engineering sent me a billet prototype high-flow water pump impeller to test. If we can increase coolant velocity and turbulence through the engine, and supplement heat exchanger capacity, F or cooler is surely within reach!
I subscribe to Cycle World magazine primarily to read Kevin Cameron's monthly one page TDC column, and to try to absorb detailed technical articles he writes that appear in about every other issue.
According to KC, turbulent high velocity coolant is vastly more effective in removing heat from combustion chamber "domes" than lazy slow moving coolant. Worse yet, is any area of stagnant coolant that rests against the domes' coolant side surfaces with slow or no movement which can create dangerous detonation causing hot-spots. Kevin describes large coolant volume cylinder heads as antique "bathtub" design. Shrink-wrapped covers create small but ample passages for high velocity coolant flow over the combustion chambers.
Some of the aftermarket snowmobile cylinder heads I see on the dyno look like bathtubs to me. On typical dyno tuneups especially this time of year it's more time and cost effective to dyno sled engines with their own coolant, letting the 7.
To maintain consistancy, I like to measure head surface temp with an infrared gun before each dyno run. On most sleds, head surface temp runs about 20 degrees F lower than coolant temp, but this is not as important as doing each dyno run with similar engine and pipe temperature. What I notice on some aftermarket cylinder heads is that ending surface temp after second dyno runs is sometimes much higher than what we usually see with stock heads. In the past I have dismissed this difference in being caused by different material finish shiny machined and anodized or powder coated billet instead of die or sand cast surfaces causing different infrared gun readings.
How bad is this? Kevin Cameron had suggested to Tim that the golf-cart-like transfer ports on the Exciter engine limited its potential.
So Tim decided to widen the engine to allow room for larger transfer ports that he would create out of material welded on to the sides cylinders. This meant having the Crankshop build him a wider crankshaft, then saw a crankcase and cylinder head in half, then weld in an inch or so of material to allow bore spacing to be wider, accomodating normal-size transfer ports. Tim's problems began when the one-piece cylinder head was widened and welded back together.
The Exciter 's coolant normally enters the front of the head in the center, then is forced around each combustion chamber surface, then rejoins as it exits the rear center of the head at the thermostat housing. Unbeknownst to Tim and me, this allowed stagnant water to lay on the combustion chambers instead of flowing over them. On the dyno, even with lots of water flowing to cool the engine, we never could create low BSFC without detonation.
But the engine made more HP than before and Tim was anxious to test the engine in his race sled before going to the annual big oval race at Eagle River.
I went with Tim to a nearby frozen lake where the night before he had snowblown an oval track on the shallow end. When he began doing laps with his dyno-tuned engine Tim encountered detonation with the same jets, same gas as we had dyno'd with the day before.
Jets that were dandy for 15 seconds on the dyno were causing deto on the track after 20 seconds. The 48mm carbs required about 15 sizes larger jets to be deto-free, and that extra fuel drowned the HP added by the larger transfers. This was perplexing to both of us. At the end of the day, Tim's high HP wide engine was no faster than the narrow golf-cart Exciter race engine he had run previously. With his other race engines, winter dyno jets were within a few sizes of what he needed for 20 laps.
That evening, one of us remembered the widened cylinder head. I like to think that I came up with the solution to the problem, but it probably was Tim. One of us called the other, and we discussed the possibility of a problem with combustion chamber coolant flow.
Tim went to the shop at 10pm, and upon inspection found that there was an open passage in the widened area for coolant to flow directly from the front center head inlet to the rear center outlet! He mixed up some Devcon epoxy filler and goobered that unintended passage closed. As intended, coolant would once again be forced to the outsides of the head, pass over the chambers then rejoin at the rear before exiting the engine. The next day back at the lake, Tim was able to jet down all of the 15 sizes and then some and the HP was back, deto was gone.
More races would be won. Bottom line--stagnant coolant was surely the culprit. I'm not suggesting that all billet replacement heads are low velocity bathtub design--in each case I don't know what sort of internal passages were created by the person who programmed the milling machine to carve out the "tub". But my opinion is that before an aftermarket head is installed in might be good to compare coolant volume between the stock head and the replacement head.
If the replacement head has larger capacity than the shrink-wrapped stocker I would question the design and ask why the volume is greater.
If the answer is "to help cool the engine" The factories' sled engine designers surely use dyno software that measures coolant flow in GPH, and that figure along with temperature rise in the coolant around each combustion chamber is necessary to correctly design the cooling passages in any cylinder head, either OEM or replacement. When it comes to snowmobile cylinder heads, cool-looking and big is not necessarily better. I won't be making jokes like that anymore! The driveshat had separated at both ends--from the rubber vibration dampener at the engine, and the automotive ujoint coupler at the absorber end.
But most importantly no one got hurt. Do I need a stronger driveshaft? Trying to assess this mess, like a forensic detective, I think this is what happened There just seems to be more torsional vibes with the big triples. But that didn't register with me never had that happen before , and it should have. Brain failure one is I should have removed my adaptor, cleaned the tapers and started over. Not everyone has that.
And that center self aligning bearing what's left of it is designed for the linkage of helicoptor rotor assemblies. The aluminum part is custom made on CNC machinery. New parts are on the way here. We cooled the crankcase for a few minutes before the next run. I bolted from the control console, grabbing one of the 25 year old, but previously unused Halon fire extinguishers, and ran into the dyno room and with two pounds of Halon completely extinguished the fire.
But with the fire extinguished, there was still a substantial amount of oil left on the dyno table beneath the sled. That unburned oil, instead would surely have been spewed and drizzled in front of the smooth rubber track with instant loss of traction and directional control!
Without these features, the fire on the dyno table and the potential real-world scenario could have been much, much worse. Why not add some sort of diaper-like oil catcher like the top fuel racers use? It would be wise to deal with the inevitable spewing oil ahead of time. From now on, people bringing heavily boosted engines to DTR must endure a pre-test fire drill. The new system is up and running perfectly. All new electronics, computer circuitry, and control console that took a couple of weeks to install properly.
The operating system is quite different from the old 24 years old , and has taken some getting used to. I used my HTG Edge triple to verify the new system. Tuned to max power on pump gas on the system, it made HP. As Brett gauranteed, the engine made HP on the It's just math--torque and RPM, but it made me feel real good to see it myself on my own sled that has dyno runs on the , and now 90 on the new system during training.
And now instead of manually adding torque to make up for the 6. Remember--the computer system in the console was designed 30 years ago, and times and speeds have changed.
The recorded data 10x per second and the new stuff records x per second. Sean and I are experimenting with dragrace acceleration tests that now can be viewed on the "real time" graph. Some of that cooling system is sitting on the dyno table visible on the engine room webcam. Also water vapor in the outside air will be removed by the evaporators. Tuning EFI sleds for winter operation in 75 degree F air is useless.
Because of that I've recommended all EFI sled owners wait for cold air before dyno tuning--so that meant a logjam of sleds to tune as soon as winter arrived. So having winter air for tuning regardless of the weather forecast will be a dandy thing, as we should see shortly. Expect this system to be installed and operating this month. I wil have a mule engine on the dyno to baseline perfectly with the current system, and then make sure we get the same accuracy with the new equipment and electronics.
Two weeks ago Woody's Performance Center from Maine Woody's photo appears on the homepage with his mad Methanol Supercharged Apex brought a perproduction Apex for assessment. This session was done on Yamaha's behalf, and as such they have requested the results be posted mid August.
You Yamaha guys are going to enjoy this data. Rob S will be here to tune ignition. I bought a 6. While I enjoyed the variable speed rear wheel drive, the engine pissed me off.
I've been mowing lawns for over 50 years. But this new 6. It just annoyed me. Recently I ran accross this website https: Testing is being done on the SF sled driveshaft dyno connected to the output shaft of the YZ trans. The toothed belt sprockets are mounted on 1. Like any gear reduction, this drive system converts a certain percentage of the engine power into heat from friction.
This loss has been accurately measured, and compensated for in our dyno calibration process. Since HP loss from friction increases exponentially as the square of engine speed, the following percentages must be added to raw calibration torque numbers to be correct at the RPM where peak horsepower occurs.
Also figured into the friction loss is a GMN overrunning sprag clutch that is used in the electric start system on the engine drive shaft. The net weight value of the arm itself is The raw torque value of the hanging scuba tank is That is reduced by the It had to be a cheater. During the Shootout we make on-site real-time comparison of stock vs trail mod difficult since we public address and listen to ' results of stockers and ' results of aftermarket trail mod sleds.
But after getting back home and assessing ' results of stockers I can see clearly the supposedly stock hp Xfire was much more powerful than that. Once again, mia f'ing culpa. But even though the Unlimited Class results are tainted by this, the class and class results are as they should be. When we decided at the last minute to have an unlimited stock class to differentiate from the 's we included the two big Arctic Cats-- Z1 turbo and the Crossfire They were already bringing a trailer-full of Cats and Yamahas to dyno certify, and a second trailer was a lot to ask.
There should be no incentive for them to cheat one over one another since they were the same brand. So we allowed Big Moose to keep the sleds, no dyno certification and lock-up, let them run in the Unlimited Stock class amongst themselves. AC lobbied for some miles on the Z1 for breakin and we concurred that that was acceptable, and Big Moose was allowed to run the sled on the trail for the breakin miles AC requested with no supervision.
The Z1 was surely left stock--the timed performance was commensurate with power to weight ratio. It's reasonable to let those Z1 results be included in the Shootout.
But for now, in the interest of fairness to everyone including the very important aftermarket participants, the Crossfire results should be deleted. He indicated no knowledge of this cheating by Vince. I can accept that, because I'm sure that Phil and Jon Martin both have IQ's high enough to realize the negative results of this buffoonery--make the Z1 look slow so no one will want to buy them? Make their Crossfire sleds look slow? George Taylor and I had stressed to all dealers the need for a flawless Shootout and this is what we got.
Kevin Cameron Emailed a few times: This is fascinating about the plugs loosening. I will ask in aircraft engine circles to see if they are familiar with this. One interesting point is that at least some versions of the BMW cc 4-cylinder turbo F1 engine had a small, spring-loaded relief valve in each cylinder. That indicates that they had some bad events that needed radical measures to control them.
I've seen insulators broken by deto. I think your idea about yielding of the threads is the explanation, but with the added notion that each pressure spike causes some pretty stout sound waves to rattle back and forth many times through the metal.
It might be the cumulative result rather than the single spikes. Much the same explanation as why ignition-side flywheels may slowly work their way off the crankpin in engines turning higher-than-stock rpm. The force of vibration isn't enough to push the wheel off the pin, but the general disturbance of the flywheel, being set vibrating, lets it work loose.
Some of the early castings used on testing of the engines destined for the B cracked and in some cases whole pieces of the heads were broken loose so they fell out once the sheet-metal cooling air baffles were removed. They always had piston temperature problems until they adopted only postwar toroidal oil jet manifolds in those engines. Those guys that make the vehicle shakers, MTS, also make a device they call a "gun banger".
I am suspecting that a lesser pressure in psi, but applied to the whole inner combustion chamber surface, would deform it enough to perhaps loosen the threads. BMW must have had some good reason to fit their race engines with those relief valves. Do you suppose they had this trouble? I suspect that only very high BMEP engines have this problem. Imagine combustion proceeding, and the flame front moves out from the central plug.
Ahead of it, the unburned charge is being compressed. When the sneeze comes, it will be a hum-dinger. I joke with sled owners here that even with all of our fine dyno instrumentation, we still stick our noses into the engine room, and when our eyes just begin to water from some noxious smell, then we know all is perfect, and there is very little extra HP to be gained with leaner mixture.
I think the gas you smell is nitrogen oxides making acid with atmospheric moisture, rather like sulfur dioxide makes sulfuric acid with moisture. The hydroxyl radicals are short-lived - I don't know if they even make it out of the engine.
They are the trigger for deto, and what lead oxide product of burning TEL does is act as a negative rate catalyst. In our old barroom analogy, the lead oxide is the big bouncers who go up to the most excited troublemakers in the room and quietly whisper what they'll do to them if they make ANY trouble. It only works up to a certain level of excitement, after which the trouble starts no matter how many big bouncers are in the room. How do you make pistons last even a moment at such power?
That would make a good setup for 40, feet, if the air wasn't too thin up there to cool the rad. That was the big problem with the B - above 20, the air was too thin to cool it properly, so on the trips to the Empire they had to run in auto-rich to fuel-cool the engines.
Have I mentioned that the top s in GP racing now make a bit over hp? Not many secrets can be left! Also, I see that your turbo sled bmeps are very high, so I have asked if any of the air racers have had the plug-loosening experience. A Merlin in air racing, making hp at rpm, is at psi. Those toluene-burners in s F1 were at psi for qualifying and for the races.