All of a sudden lots more Ooomph!

Got the bike in the warm weather (tail end of summer) riding it in the
winter, the bike has more get up-n-go than when I was tooling around in
the summer. Is there a reason? Do v-twins prefer colder climes? It
has a radiator & fan...........

2000 Kawasaki 800 drifter. Bone stock.


--
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Part of it is forgetting how fast the bike is compared to the car,
and part is the higher density of the cooler air. That's why the
first few blasts in early spring are so fun when you take the bike
out of winter storage.

 

Not quite.More power requires more fuel, too. A carburetted engine
has no way of measuring O2 qty, it measures air volume, so
will run rich at high ambient temp and lean at low ambient temp,
just as it will run rich at high altitude and lean at low
altitude for the same jetting.

Fuel injected engines with either an air mass sensor on
intake (a heated wire, essentially) or an O2 sensor on the
exhaust side, make your statement essentially correct.

 

I don't know if the Kaw has a pressure sensor or not but I can tell
you that density altitude does make a 'seat of the pants` difference.
I used to ride from home on the east coast, (400' above MSL), to play
in he rockies in the summers, and even with dropping the jet needles a
notch to keep the carbs close to tune, there was a noticable decrease
in passing power, even on the Interstates short of Denver,(5000' above
MSL), let alone in the mountains proper.
If that Kaw was last tuned for winter weather, the temperature effect
would be even more noticable.
Dallas, you might check your state of tune as the weather warms up
again this spring. Don't lean her out too much, but you might be
pleasantly surpprised if you keep her spot on.
Best of Luck, Pragmatist - "R75/5 Forever!"

"Due to budget cuts, the light at the end of the tunnel has been
turned off."

 

Could be an interesting side issue here. A pilot told me once that three
enemies of lift are height, heat and humidity. All 3 lower air density.
A carburetor is supposed to respond to flow, not density, so these 3 things
should also affect the performance of a carb.

When you get up into the mountains, it burns rich because of the reduced air
density ie they respond to flow. (AFAIK fuel injection has mass flow sensors
which fix this)

Vehicles seem to run better when it's humid (like in the rain). Water is
supposed to be a good anti-detonant. At one time something that happened
was to put water injection on your motor when you popped it up. An
explanation I heard was its because the water takes on a bunch of latent
heat when it vapourizes in the combustion chamber, reducing pre-ignition.

Fair enough. But if it already exists as vapour in the air, this doesn't
apply. Its pressence just reduces the density of the air. And I would think
the %O2 to some extent.

What's my point? Uh....I'm not sure. Thought I had one when I started
this...

D.

 

My worthless unscientific addition is that my old 1981 Honda 750C ran
noticably better in humid conditions. Never knew why, I just enjoyed.

 

give extra power over short periods
was injected into the manifolds to increase pressure

 

OK, (I used to fly a Cessna back when pterodactyls still tried to
horn into the landing pattern and it was affordable so I'll try to
respond.)

Yes they do. Altitude and humidity both 'lean out` your mixture.
Humidity has less effect however as 'best power` is achieved with a
mixture slightly richer than stoichiometric because the vaporization
of the extra fuel, (or water vapor in some cases), helps turn more
heat into pressure in the cylindars instead of loosing it out the
pipes. This was the idea behind water injected engines and the reason
engines seem happier in the rain. The engine runs cooler and fuel
efficiency rises.

Right, thats why I 'drop the jet needles a notch`, (lean the mixture a
bit), going from low altitude to high on my bike. (Its easy on the
airhead beemer with the carbs right out there where you can get at em.
Suffer you rice burner jockeys!)

Right again as far as the O2 content, but the water vapor expands
better than air when heated and so still offers some benefit provided
the mixture is correct.

I didn't really have one either, just like to shoot off my big mouth.
See ya on the road,
- Pragmatist - R75/5 Forever!

 

Just in case anyone might care...
Water injection was also used for fuel economy for old commercial flights.
Some Methanol/water systems achieved fuel efficiencies of .36lb./HP/Hr. at cruise.
Pragmatist.

 

This may help a little. Just doing a simple Google search will bring up
pages of info.
http://www.aquamist.co.uk/dc/dc.html

 

My truck doesn't have too much trouble running 15psi boost on kerosene.

 

Dallas,

I've played with my dual-carbed Vulcan 1500 engine for the last few years.
Your bike is probably on the edge of running rich. Not too rich, just rich.
The colder temperature around the engine and the denser air leans the
air:fuel mix (increased air density) just enough to change the performance.
In your case, increased performance.

My limited and anecdotal experience implies that most MODIFIED/rejetted
carbed bikes run too rich. Too many dealer wrenches will unnecessarily
increase jetting when they install third party exhaust pipes.

I'm also of the opinion that extreme weather changes (heat and/or humidity)
can push the air-fuel mix to either side of the optimal ~14:1/air:fuel mix
effecting performance which is "set" by the fixed jetting versus the air
density that can vary literally from moment to moment. This variability
created the market for computer controlled fuel injection that constantly
measures several environment factors, and adjusts fuel volume as required
for optimal engine performance.

I've read that racing mechanics will rejet and change needles in a carbed
engine for the race day's weather.

JM2C. Ride safe.

Manjo 1500A9

 

If your car's engine is running at 10.5:1 (static) compression, you cant add
that much boost. If your engine is running at 8.5:1 (static) compression,
you can add more boost.

If ATM is 14.6 PSI, then at 10.5:1 that's 154.3 psi at TDC. add 6 pounds of
boost and we are now at 216.3 PSI in there. (this is assuming there is no
vacuum for the first measurement which we know is not true, )
Or, at 8.5:1. that's 124.1 PSI N/A, and 217.6 PSI with 11 pounds of boost.

A friend of mine runs 12PSI boost with 10.5:1 compression. With 91 octane,
he has to keep it under 5,000 RPM. with 104 octane, he can take it to the
redline. With the amount of time that car spends in the shop. I really don't
think its a good idea to try it.

when you look at the specs for super charged or turbo cars, you will notice
the compression ratios are always lower then the N/A cars in the same line.

 

Correction, I just remembered when I had the vacuum gauge connected to my
truck. At idle, it was pulling 25" of vacuum, at WOT, it was at zero. So at
WOT, these measurements are accurate.

 

I'm only running 21:1, and preignition isn't a problem.
(You can't burn what isn't there.)

 

A little bit of both. Remember we're talking about big old radial
aviation engines at low R.P.M. here. The methanol not only prevented
the system from freezing at high altitudes, but drew off more heat in
turning from droplets to vapor than water. The fact that the stuff
could contribute to the burn was helpful, but incidental.
The principle was to prevent knock, (autoignition of the charge), at
the high 'boost` that allowed greater B.M.E.P. and therefor higher
efficiencies from the same fuel input. In those slow turning engines,
the strokes took more time than we're used to thinking of in bike
engines, and those big air cooled cylinders were running closer to
their strength limits than we normally encounter in road engines.
Prevention of knock was critical.

As to running water injection on the road today, a system that does
all the required metering and math, plus the water tankage would
probably not be practical on bikes. For cars the idea looks promising
at first glance:
a. lower peak cylinder temp.s hence greater thermal efficieny less
wear, less NOx production.
b. less total fuel consumption hence lower total carbon output.
c. economically, the system would probably be less expensive than the
anti pollution stuff currently required.
With current engine management technology it's definately doable, but
then how would they continue to sell us all the expensive, power
robbing, emissions plumbing they spent all that R&D dough on??
**I am not anti clean air regulation, I just believe that it should be
done by efficiency, not waste.** - 'Less fuel burned = less
pollution.'
But that kind of regulation would make it tougher to sell those
bloody damned S.U.V.s of which we are all so fond.
( Oooops, - Sorry for the rant. )
Pragmatist
"Eternal vigilance is the price, both of freedom,
and a crabgrass free lawn. - The lawn is easier."

 

*snip*

Agreed. Whole heartedly.

J. Firespear

 

The way I understand it, super or turbocharging effectively increases the
compression ratio, which would tax the octane rating of the fuel. It was a
few years back when I had an active interest in this topic, like...mid 70's.
I was keen to turbo my BMW 2002 at one point. There was an European version
which was turboed, I can't recall the exact figures, but the turboed
compression ratio was something like 8.5:1 instead of 9.5 or 10.5:1
depending on the model.

At that time, the water injection thing was a cheap easy solution to the
ping problem. I seem to remember that one theory was to use a windshield
washer pump an a DP sensor to turn it on when the manifold pressure went +.
Another cheap and dirty solution was simply to vent the manifold pressure
into the water tank. When the manifold went +, it squirted water into the
intake.

Apparently they weren't that particular about how much water they got, as
long as they got enough. It was a matter of increasing the orifice or
whatever 'till the motor was happy and stopped pinging.

I'm not quite up on the current technologies, but as someone mentioned in
another post, I would think that what he called modern "engine management"
would make a difference today WRT the preignition, boost, and allow turboed
motors to run on crap gas.I know my truck has a knock sensor in it. It
doesn't seem to care what I put in there,could be aftershave for all it
knows, all you ever hear is the odd "tick". I guess it mucks with the
ignition timing and mixture to stop it or something.

But I figure there's no free lunch, as they say. So when I load up the truck
and head off east, committed to traveling a thing here in BC called the
"Coquihalla", infamous to truckers for its long steep grades, I put good gas
in it. I think it pays off, because the "Engine management" sensor/computer
technostuff knows I'm being usually kind to it and the appropriate
adjustments are made, and I believe it actually uses less significantly less
fuel, maybe even enough to pay for a pint at the next waterhole.

I have some other theories about manufacturers claims about vehicles taking
"regular gas". Everything now adays is supossed to happy on "regular gas"
When you look at the motor specs, your intuition tells you that better gas
should be put in these things. But they seem to work OK on it, so that's
what they get.

Cheers

D.

 

What are you running 21.1 in? do tell. Since most Diesel's run in that range
(+/-)
The most you can run in a Gas engine on pump gas is 14:1 I believe (you CAN,
but shouldn't)

So what "Isn't there"? fuel?

 

6.9 out of a Ford. Most current diesels run < 18:1 with open chambers.

Keep the fuel out of the chamber until you really need it.