Why is there 1 carb per cylinder when a car has one carb for multiple cylinders?

Got trumpets?

 

I'd rather have a K&N than nothing at all. The shite that gets sucked in
will cause bore and piston wear.

 

Hello? Dyno runs are NOT representative of real world riding
conditions. If you have an inertia dyno and you rev up the engine and
get a run at the rollers, you shoot right through the flat spot with no
problems, just like drag racing or straight line street runs.

You need an complete engine tuning package for road racing that lets
the engine pull its way out of the torque valley when it's stuck down
there in a slow corner and you're between optimum gears.

Some modern engines have specially treated connecting rods to allow
over-revving in 2nd gear to avoid shifting up and down in medium speed
corners. Every extra shift wastes about 1/2 a second and that counts
when you're trying to get your lap times down.

 

Why does this thread have to go on and on and on in
rec.motorocycles.tech?

The newbie question has been asked and answered.

The original poster said he was quite satisfied with my explanation of
why motorcycles have multiple carbs instead of one carb on a manifold.

 

Because you replied to it YTC.

 

It does have gauze and paper K&Ns. They're a bit battered and really
need replacing.

 

Now that I didn't know.

They do? Which ones?

And why should over-revving in second gear be any different from
over-revving in any other gear?

You sure you're not confusing this with the little electronic gizmos
that prevent over-revving so you don't wheelie the eff out of it in
first and second?

 

Because the rest of your assertion was questionable?

Specifically, this onbe:

"OK, so you have a twin cylinder machine with separate pipes and that is
a major clue as to why you don't have the dreaded inline four flat
spot."

You're saying that four-into-one exhausts have flat spots, and I rather
disagree with that.

You also said that only Yamaha's EXUP solves the problem. Also
questionable.

You also said that other Jap manufacturers have copied Yamaha's EXUP
system, and I pointed out that Yamaha's patent lawyers prevent them from
doing so. Other makers have their own variations on the theme, but the
EXUP is an original. You snipped that bit.

 

The freeway doesen't come to my front door, I have to ride about 2 miles
north on a 35Mph road with many traffic lights to catch it. And several
times during the week I have to go to customer sites where the freeway
is only part of the way there.

I think the operative word here is "helps" and you have to have a midrange
torque vally to begin with for airbox fun and games to make a difference.
For bikes that don't, the airbox does very little.

Ted

 

If that's the case, I stand corrected.

 

Indeed so. Apologies.

 

Somehow I doubted you were mad enough to have only trumpets.

 

You are welcome to use my knowledge of the history of high performance
engines in one of your free lance articles. Don't be shy about it. It's
all been published before.

Ask Kevin Cameron. He knows.

Piston ring flutter was the problem that limited upper RPM limits until
Honda came out with ultra thin low mass piston rings in the 1960's.
Wiseco jumped onto the thin rings and made thin ring pistons for the
general public's Yamaha 250's in the mid-1960's. Now thin ring pistons
are in all the high performance machines.

Then the problem was connecting rod breakage at around 13K RPM. Suzuki
solved that problem with expen$ive Carillo I-beam con rods. But, at
$1000 a set, a
street bike/box stock racer wouldn't be regarded as such a bargain,
they wouldn't fly off the show room floors if they cost $5000 instead
of $4000.

Though the Yoshimura GXSR-750 that was first seen in 1985 had a 13K red
line with
about 130 horsepower, the GSXR that Americans received was
electronically limited to a peak of only 11K RPM and riders were lucky
to get 80 or 90 horsepower out of it.

So Suzuki found a way to upgrade the rods inexpensively in the early
1990's.

It's probably the same process that Yamaha used on the 600cc R6,
carburizing or flame hardening the surface to a shallow depth.

In the theory of strength of materials, loads are carried on or near
the surfaces of the structural members, so surface hardening makes
sense in theory and seems to work in practice.

Now that the piston ring and connecting rod problems are solved, the
issue that limits
engine life is cracking around the piston's wrist pin bosses, according
to K. Cameron.

Most gear boxes have a first gear spaced much further apart than the
other 4 or 5 gears. There is like a 30% RPM drop shifting from 1st to
2nd gears, then a 15% drop between 2nd and 3rd, etc.

By the same token, shifting down from 2nd into 1st increases the RPM by
30% and the rider has a hard time controlling the throttle and traction
when the crankshaft flywheels may suddenly slow the machine down. First
gear is generally unusable in a slow corner because of crankshaft
inertia slowing the machine too much.

Norton Manxes needed a really tall 1st gear in their 4-speed
transmissions in order to be usable on a race track and they were tuned
to run "on the horn" with the intake horn and exhaust megaphone working
together at a critical RPM.

The rider had to stay "on the horn" by slipping the clutch in slow
corners and when first leaving the starting line at the beginning of
the race.

Honda tried increasing the number of gearbox ratios so their peaky
tuned engines would always have a gear available that the rider could
select to keep things perking inside the buzzy little engines. The FIM
outlawed excess gear sets, so the only thing left was ridiculously tall
first gears, or over-revving the engine past the torque peak in a lower
gear to avoid shifting.

On many GP and AMA national road race courses, the motorcycles will be
running in either 2nd or 3rd gear through most corners, and revving
past the torque peak to avoid upsetting the chassis when shifting gears
with the machine leaned over.

You can see what gear the motorcycle is in and what RPM and speed the
motorcycle is going in a box at the top of the screen. The world
champion and national class champions are only in 4th, 5th and 6th
gears on the longest straights.

Nope. There are RPM limiting or ignition advance limiting circuits on
some machines, but the riders over rev their engines in the lower gears
to avoid shifting while leaned over.

 

OK, let's end it right now.

The reason that there is 1 carb per cylinder is that two or three
would be silly.

There, now we can all happily go back to our lives....move
along, folks, nothing left here to see....

Bob M.

 

Yes, yes, yes.

I really don't know how to make you understand that strengthening
conrods is something that is of benefit in *any* gear, not just second.

 

This is true. The manufacturers have only really started optimising
airbox performance, and "tuning" them, in the last decade or two.

For older bikes, they were simply... well, a box to put the air filter
in.

 

<VVBG>

 

Using the patented Mavis Beacon "Hunt&Peck" Technique, Bob Myers

Agreed. V-Maxes are *very* silly.

--
Wicked Uncle Nigel - Podium Placed Ducati Race Engineer

WS* GHPOTHUF#24 APOSTLE#14 DLC#1 COFF#20 BOTAFOT#150 HYPO#0(KoTL) IbW#41
SBS#39 OMF#6 Enfield 500 Curry House Racer "The Basmati Rice Burner",
Honda GL1000K2 (On its hols) Kawasaki ZN1300 Voyager "Oh, Oh, It's so big"
Suzuki TS250 "The Africa Single" Yamaha GTS1000 Honda ST1100 wiv trailer

 

butbutbut - didn't Honda build a big single with two carbs at some
point?[/QUOTE]

That's nothing. They built a v8 with four cylinders.

 

I saw an old British single in the seventies with a butterfly valve between the
header and the megaphone. It was open at high engine speeds for power and shut
at low engine speeds or when passing PC Plod, if the rider remembered in time.