One benefit of the cold

[Rogue Wave]

I've been out and about a bit on Stevie lately and I must say the cold weather definitely has a pleasing effect on my outboard. Has any body else noted this

I presume it's cos the air is denser but it definitely seems to have more whumfff

[Ezgoing]

Is it because the engines are cooler that they appear to be able to run for longer and appear crisper?

Is this a real effect?

[ADS]

Originally Posted by Rogue Wave

I've been out and about a bit on Stevie lately and I must say the cold weather definitely has a pleasing effect on my outboard. Has any body else noted this

I presume it's cos the air is denser but it definitely seems to have more whumfff

My dad reckons that beacause its colder the spark is bigger and produces a bigger bang, therefore more power and it goes better. In the winter though I dont use the boat as often because of the weather therefore the time gap between each trip gets bigger, so if i dont use the boat for a month and then take it out I think this feels quick! When in reality its the same.


Alex

[Mollers]

Diesels run better in cooler weather hence " intercoolers". Engine room temperatures on a boat with non-intercooled diesels are critical. If the engines are "breathing" hot air it can cause dramatic power loss.The air is less dense, less oxygen = less bang etc.

[hard1]

My 4X4 not only goes better in cold damp weather, it goes much better when I clean it too...

Same for the boat....

[codprawn]

Just have a look at any aircraft operators manual - hot and high takeoff much longer than cold and low. Airliners can carry far more cargo/pax in colder conditions.

[jyasaki]

Originally Posted by codprawn

Just have a look at any aircraft operators manual - hot and high takeoff much longer than cold and low. Airliners can carry far more cargo/pax in colder conditions.

That, however, is a function of the airflow over the wings, rather than engine power. Denser air over the chord creates more lift than warmer, less dense air for a given airspeed.

jky

[Scary Des]

Originally Posted by Rogue Wave

.....I presume it's cos the air is denser .......

Yep, cold air gives you greater volumetric efficiency which is what an intercooler is trying to do.
Better still is cold air and fog (and no air filter) = whumfff whumfff whumfff Des

[MikeH]

Found this after a quick search but I once found something a bit more detailed.

Ever wonder why your boat seems like it runs better some days than others? Rest easy, friend. It’s not your imagination. Just as weather patterns have a direct effect on the feeding habits of fish, changes in air temperature, humidity and barometric pressure affect an engine’s performance — be it an outboard, inboard, two-stroke or four-stroke. Such weather-related performance issues stem from the fact that internal combustion engines are, essentially, air pumps — and in order to run at peak efficiency, they depend on a specific ratio of air mixed with fuel.

“In turn, the horsepower and torque available from a normally aspirated engine depend upon the density of that air,” says Richard Shelquist, an expert in engine mechanics and owner of Shelquist Engineering in Longmont, Colorado. “Higher air density means more oxygen molecules are available for combustion and, hence, more power. Lower air density means less oxygen and less power.”

Change any of the three factors — temperature, humidity or atmospheric pressure — and the amount of oxygen available to “stoke” your outboard changes proportionately. Altitude also plays a major role in how an engine will run. But altitude isn’t weather.

Lots of similar stuff if you look araound the web. If you ever plan to run a boat on a lake at altitude then you need to re-jet the carbs. I think they mean anything aver about 5000 feet so not applicable to the UK.

I was once told that the best day to run a boat is cold, damp during high pressure - Typical grey still winters day

[MikeH]

A bit more

[quote

All three engineers gave some weather-related examples using a 200 hp engine as a baseline. On a 77-degree day, with the barometer sitting at 29.53 in.-Hg, and 30 percent humidity, power output is 100 percent.

If humidity remains constant, but air temperature drops to 70 degrees and the barometer to 29.20 in.-Hg, power is down to 198.6 hp — a loss of 1.4 horses.

Run the same engine on a 100-degree day, with the barometer at 29.53 in.-Hg and the humidity a steamy 80 percent, and power is now down to 185 hp — a whopping 15 hp loss.

Conversely, if barometric pressure remains 29.53 in.-Hg, but air temps drop to 50 degrees and humidity plunges to 20 percent, power output jumps to 205.8 hp.

Drop the temperature to an ice-fishing 20 degrees, raise the bar to 29.7 in.-Hg, and cut humidity to 0 percent, and that 200 is now making 211.4 hp. Of course, it’s too cold to do anything with all that horsepower, but it’s nice to know it’s there, all the same.

’TUDES AND TEMPS

Even though altitude is a matter of geography, not weather, elevation plays the biggest single role in the horsepower/performance equation. For every 1000 feet you climb above sea level, there is a reduction in air density of approximately 4.5 percent, according to Marcellis. So, for every 1000-foot gain in altitude, there is a corresponding loss of horsepower, which means our 200 hp outboard gives up 9 ponies.

Water temperature also plays a role — although it’s miniscule in the grand scheme of the performance game. “Water temperature can impact power, depending on the way the cooling system is set up,” Marcellis says. “But the effect is minimal. If you have a closed cooling system with a thermostat, the thermostat will keep the engine’s operating conditions close to constant.

“On open cooling systems — like those found in our Merc 2.5 Drag — the lake water has a direct effect on cylinder-head temperature. The cooler the temperature, the denser the intake charge and the greater the power produced. However, the amount of the power change is difficult to establish, because you don’t know how much temperature change is involved.” Yamaha’s Hoshiba puts it in layman’s terms, saying, “Cool water keeps the engine cool, and allows it to draw in more air.”

[/unquote]

[codprawn]

Originally Posted by jyasaki

That, however, is a function of the airflow over the wings, rather than engine power. Denser air over the chord creates more lift than warmer, less dense air for a given airspeed.

jky

That is true but at a given altitude temp has more effect on engine power than lift.

[Rogue Wave]

I dunno about higher altitoods but it's very nice effect at sea level

[DJL]

It makes driving the car more fun in the winter too

[Rogue Wave]

you should call your boat Cold Shot

BTW are you very busy at the mment

[DJL]

Cold Shot - quite like that, it’s on the list.


Not busy at the moment - can I be of assistance?