[Pete Muller]

They are almost unrelated, except for each having 4 wheels.

The biggest difference by far is that a kart has a solid rear axle.  This means that a kart needs to become a 3-wheel vehicle in order to “turn in” to a corner.

That constant transitioning from 3 to 4 to 3 to 4 wheel vehicle is why karts have track-to-wheelbase ratio, caster, kingpin inclination, scrub radius, and many other things that are totally unrelated to automobiles.

PM

[Pete Muller]

Sorry David — I *have* to stick Fullerton in the list even though he’s British.

– Terry Fullerton

– Lynn Haddock

– Kyle Adkins

All 3 of the above come from eras when the driver did it ALL — tuned the engine (probably even built it), set up the chassis, raced it, cleaned it, transported it, etc.

Fullerton might have been the best driver ever — the only guy that Senna couldn’t really beat in karting.

Haddock?… well, in my opinion he gets the nod for being the most complete.  Build engines, modify engines, build/modify and set up chassis, tune everything at the track, and win National Championships in Sprint, Road Race, and Dirt (more than any other driver in U.S. karting history, I believe).  And for good measure:  take on Jr. Drags and mop up the National field with his daughter in the driver’s seat.

I HAVE to include Kyle Adkins, as he may be the only driver I ever saw that seemed to be able to actually defy physics when he was really motivated.  I saw him do things in a kart that seemed absolutely, completely impossible, and have yet to ever see anything like it from any other driver.

All of them unbelievably great, IMO.  If pressed though, it surely must be Haddock because he was great at *everything*!  (and still is at many of them).

PM

[Pete Muller]

My gut feeling is that much/most of the “work” is probably done in the first 45° or so of crank rotation.  So at high revs, there is probably more to gain by keeping the port open “long enough” than is lost by reducing the number of degrees of crank rotation where work can be done.

Flame speed of around 90’/sec (1,080″/sec) means that it takes less than a millisecond to burn all the mixture in the combustion chamber, and probably 1/2 a millisecond to burn most/all the mixture in the dome.

At 12,000 rpm (a convenient number to assign for peak horsepower, it takes about 5 milliseconds for a complete turn of the crank.  Ignition probably happens around 22°-30° BTDC (depending on engine/tuning), so it’s a safe bet that the mixture has all burned by 45° or 50° ATDC.  (and “most” of the mixture has likely been burned by 10° ATDC).

So in a nutshell, as the revs go up, the *time* between the port events (transfer opening to exhaust closing, which is probably the most important) gets shorter.  Raising the exhaust brings that into a better state of tune.

Looking at this just as a “port height” thing is probably not ideal though, since the exhaust pipe, crankcase volume, and many other things enter into it.  I’ve seen engines with low exhaust ports rev insanely high, and I’ve seen engines with high exhaust ports put out monster peak torque numbers at “typical” revs.  Yes… very generally speaking, (in karting) we’ll see higher exhaust (and often more blowdown) in a high-revving engine (one that puts out peak horsepower at higher revs), though there are many ways to get there.

PM

[Pete Muller]

Ric,

Absolutely correct — here’s what happens:

Retarding the ignition timing drives the exhaust temp up significantly, which *increases* the speed of sound.  This causes the exhaust pipe to “act” like it’s shorter than it really is (allowing the engine the engine to rev higher).

Ideally, the exhaust would be adjustable, and the ignition timing would stay the same or even be advanced a touch at very high revs, but since most classes have a fixed exhaust rule, retarding the timing tricks the engine.

PM

[Pete Muller]

I have come to the conclusion over many years that higher compression makes more power through the entire range (within limits, obviously… there comes a point where things start breaking!).

I believe that the “perception” that raising compression increases low/middle rpm power while hurting (or not helping) top end power (or even limiting peak revs) has to do with typically inadequate fuel metering.

I don’t think there is any question that peak fuel demand *per*cycle* is at peak torque.  Generally, I feel what happens when people test higher compression is that they have to richen the mixture to keep the engine rich enough through peak torque (aka: peak heat).  The fuel demands at high revs (past peak horsepower) fall off quickly, and the amount of additional fuel being provided at peak torque when compression is raised is simply a bit too much fuel at/near top rpm.

Of course the exhaust pipe and ignition timing can enter into the picture as well, however I feel the perception discussed (I’d even call it a “myth”) has come about due to poor mixture control.

PM

[Pete Muller]

Reverse it?  Personally, I don’t feel that’s possible.  Probably the main reason is that the number of years that the majority of racers have been in the sport has declined by a significant amount.  When we got into the sport, it “seemed” like the vast majority of people had already been racing for many years — I’d have to guess something around 5-10 years in the sport was typical.

I believe that number has declined significantly (for the “majority” of racers).  That makes “selling” the idea of taking the sport back to simpler and less-expensive times a difficult sell.  People jump in and out much quicker these days (and have for the past 15 years or so).  They get enthused about the image, the speed, the cutting edge “stuff”, and by the time it hits home that this is really expensive and complicated, they are probably on their way out of the sport.

Vintage racing has some great attributes, but I see it as more of a “show” and “demonstration event” in some ways (though there are admittedly some people that take it pretty seriously).

I have some ideas on the direction I would take it “technically”, but once again, this is a tough sell.  I’m not optimistic.

I will say one thing — I had direct-drive Yamaha kart for a number of years:  hardest Bridgestone tires available, no bodywork (nerf bars and front bumper only), very very simple.  It would lap a typical 45 second sprint track maybe 1 or 2 seconds slower than a fully modern setup on sticky tires with bodywork and clutch.  Without exception, everyone that ever drove it came back with a huge grin and said:  “this is what karting should be” (especially after I told them that my total cost to play with it for about 20 days at the track was a fraction of what they spent on one race weekend).

Got any ideas David?

 

Pete

[Pete Muller]

Well, as good a thread as any to express these opinions…

To put my take in perspective, realize I started kart racing in 1975.

Without exception, it’s my opinion that 3 things have taken karting to where it is today:

1) Sticky tires

2) Bodywork

3) Attempting to make it (or call it) a “stepping stone to big-time racing”

All three of the above have made karting more complicated, more expensive, reduced track time, turned it into a bash-fest, and generally put it out of reach to the “average guy” wanting to go racing.

I was *heavily* involved in the sport during the time when the above 3 items happened or became prominent, and they took karting so far away from its original intent, it’s really sad.

Sticky tires not only increased tire costs by 10x per season, they also dramatically decreased the *effective* width of the track, and significantly reduced length of any braking zone (greater traction for braking, and higher corner speeds).  End result? — more expense, and less close racing.

Bodywork added labor, cost and complexity to building/preparing a kart, and turned sprint karts into bumper cars (and enduro karts into heavier karts that went faster on the straights but were way less fun to drive).

And finally, attempting to turn karting into something it’s not (a “stepping stone” to whatever) did one thing:  Add Cost.  The people with exceptional talent will make it to big-time racing if they work at it hard enough, with or without karting being a “stepping stone”.  Also, heavy promotion costs money, high-profile costs money, advertising costs money, and karting never was or will be a spectator sport — who pays these costs? (it only takes 1 guess).   “Selling” karting as a “shortcut” to big-car racing does absolutely nothing for 99% of the people at the event (except empty their wallet).

I lived and raced through the changes in our sport, and saw what the results were.  My view is not only from the inside (karting), but I was also involved in motorcycle racing (and car racing as a mechanic) at a variety of levels.

Pete

[Pete Muller]

Hmm… sounds like the price has almost doubled, even *after* inflation:

According to a “calculator” I found for inflation, that grand in 1990 would be $1826 today.

 

PM

 

[Pete Muller]

Bob,

Unfortunately, the answer to your message title is probably “no”.

Up until about the mid-70’s (yes: 40 years ago!) karting was pretty simple.  There was one main sanctioning body (the IKF) and about a dozen classes (pretty much the same classes in sprint racing and road racing).  The classes were roughly along the lines of engine types/mods, and most of the “senior” classes were run at 2 weights (50 pounds apart).  It was very, very easy as you could go anywhere in the U.S. (sprint or enduro/road-race) and you knew you could race.  The infiltration of special interests began in the late 70’s, and Kirt described it perfectly.  I don’t believe it will ever change.

Best bet is always to see what’s popular and well supported in the area where you will be racing.  In the “old days” (ugh), kart racers traveled a lot more (gas and hotels were cheap), but that’s changed now.  Local clubs tend to get pulled and pushed around on class rules by the people that support the club.  Human nature, I suppose.

Jump in and have fun!

PM

[Pete Muller]

I’m with Steve: I enjoy playing with high-technology ideas and solutions, however karting’s down-turn in participation was actually brought on by the feverish attempts to make it a spectator sport (aka: “stepping stone to higher levels of racing”).

Class fragmentation, sticky (expensive) tires, bodywork, and the above mentioned attempts by various “promotional organizations” to make karting into “something bigger” have clearly contributed to the steady decline of participation in the sport.

Additional challenges have been things like the price of real estate (tracks), insurance costs brought on by an increasingly litigious society, and the price of travel (gasoline, etc.).

For my money, a direct-drive KT-100 powered sprint kart with no bodywork and running fairly hard tires is the ultimate “fun for the dollar” machine. To me, racing is racing… doesn’t really matter whether I go around a corner at 60mph, or 45mph, as long as we’re all in the same equipment.

That said, your development project is a really neat combination of some existing technologies with some new thinking, which has led to a really clever solution. As Steve mentioned: it’s a great idea for use on a dyno.

fwiw…
Pete

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