What the hell?

**The Pastor** · 6th September 2011, 21:37

Originally Posted by Sable

Look at this http://www.trademe.co.nz/motors/moto...-401752880.htm

He's taken a high k's GB400 commuter, put on pipe wrap, a crappy mismatched tracker seat, shitty paint, open exhaust and ditched the airbox for a pod. With a CV carb.
Guess how much he wants for it. WTF

You're going to have a heart attack when you see my custom,

no airbox / filter at all, and lots and lots of that wrap.

The price, imo is reasonable. I doubt the parts + bike value would addup to 6k, then factor in his time....

Where is your custom bike?

**scumdog** · 6th September 2011, 21:43

Originally Posted by renegade master

then factor in his time....

Time is never added to the cost if it's your own....

**The Pastor** · 6th September 2011, 21:54

Originally Posted by scumdog

Time is never added to the cost if it's your own....

clocks tell time

you buy clocks with money

therefore, time is money

**sidecar bob** · 7th September 2011, 07:59

So everybody missed the simple fact that fuel is converted into motion & heat & the more heat you can store the less fuel is wasted being converted into heat & is either saved or converted into motion.
Why does a car run shit when it is cold unless the mixture is richened & where does that extra fuel go?
It is consumed in the process of warming up the engine & cooling system & once the engine is warm the mixture can be leaned out.
There is only one thing that warms the engine up, & that is fuel.

**steve_t** · 7th September 2011, 08:49

Originally Posted by sidecar bob

So everybody missed the simple fact that fuel is converted into motion & heat & the more heat you can store the less fuel is wasted being converted into heat & is either saved or converted into motion.
Why does a car run shit when it is cold unless the mixture is richened & where does that extra fuel go?
It is consumed in the process of warming up the engine & cooling system & once the engine is warm the mixture can be leaned out.
There is only one thing that warms the engine up, & that is fuel.

What does the calorific value of fuel have to do with header wrap?

The engine doesn't function efficiently until at operating temperature because 1. the parts haven't expanded to their operating size, thus allowing blowby and loss of compression and energy, and 2. the oil is very viscous when cold so the moving parts have more friction to overcome, 3. fuel is most efficiently combusted when it is in vapour form. Fuel vapourises in a warm cylinder but remains in droplet form in a cold one.

OK, how's this? Why do performance cars have Cold Air Intakes or Water Injection systems?

**jonbuoy** · 7th September 2011, 09:30

Engines will make more power if you can squeeze more fuel and air into the combustion chamber, a cooler fuel and air mix takes up less room than a hotter "expanded" mix. I´ve always found once warmed up bikes/cars feel a bit pokier on cool mornings. Put in your own figures into the calculator:

http://wahiduddin.net/calc/calc_hp_dp.htm

**sidecar bob** · 7th September 2011, 09:41

Originally Posted by steve_t

What does the calorific value of fuel have to do with header wrap?

The engine doesn't function efficiently until at operating temperature because 1. the parts haven't expanded to their operating size, thus allowing blowby and loss of compression and energy, and 2. the oil is very viscous when cold so the moving parts have more friction to overcome, 3. fuel is most efficiently combusted when it is in vapour form. Fuel vapourises in a warm cylinder but remains in droplet form in a cold one.

OK, how's this? Why do performance cars have Cold Air Intakes or Water Injection systems?

My post absolutely missed you completely didnt it.
Im not raving out my arse about someting I think MIGHT be the case. Im just reciting basic physics.
We could go on all day about it. Cold air is a whole other topic & in no way related to why an engine runs mor efficently when hot.

**jonbuoy** · 7th September 2011, 10:05

Expanding (useful heat) gasses push the piston down, the piston won´t be pushed down harder because the piston or combustion chamber is any hotter. The heat won´t accumulate and make each stroke more powerful. The only thing that will push the piston down harder is more expanding gasses (useful heat). The useless heat passed onto the block head and pistons is wasted.

As long as the engine is warm enough to let the tolerances open up, oil to flow, water vapour burn off and fuel atomise correctly that's warm enough. Thats part of the reason Alloy Cylinder heads came about when Cast Iron blocks were still being used, Cast Iron heads don´t dissipate the heat so well.

**imdying** · 7th September 2011, 10:07

Originally Posted by sidecar bob

Why does a car run shit when it is cold unless the mixture is richened & where does that extra fuel go?

Because the fuel can't atomize correctly so a percentage doesn't make it as far as the combustion chamber, the increased amount is the amount required to compensate for that effect; any excess either puddles in the inlet tracts or goes out the exhaust.

Originally Posted by sidecar bob

There is only one thing that warms the engine up, & that is fuel.

No, that would be combustion.

BTW, an engine does not "run more efficiently when hot", it runs most efficiently at the temperature that it was designed to run most efficiently at. Fancy that.

**bogan** · 7th September 2011, 10:14

Originally Posted by sidecar bob

We could go on all day about it. Cold air is a whole other topic & in no way related to why an engine runs mor efficently when hot.

It's a little bit related, power output is proportional to the temperature differential (and thus pressure change) between what comes in the intake valve, and what goes out the exhaust. If you keep the cylinders hot, you get hotter air out, and a bigger differential, if you keep the intake charge cold, you get a bigger differential too!

**jonbuoy** · 7th September 2011, 10:35

http://www.importtuner.com/tech/impp...r/viewall.html

**steve_t** · 7th September 2011, 12:16

Originally Posted by sidecar bob

My post absolutely missed you completely didnt it.

Looks like I wasn't the only one. Please clarify

**huff3r** · 7th September 2011, 13:24

Originally Posted by jonbuoy

http://www.importtuner.com/tech/impp...r/viewall.html

http://www.epi-eng.com/piston_engine...efficiency.htm

Like I said before, look up thermal efficiency. If you read through the article and actually understand the physics involved you will see that there is a significant loss of calorific energy to the engines cooling system. If you did not need to cool an engine (i.e there were no expansion of metals or melting to worry about) then the engine would run most efficiently with no cooling whatso-ever, particularly if it were well insulated to keep all of the extra heat from combustion in. Theres only one place for the heat to go if that were to happen, and that is into another form of energy, likely to be more useful.

Yes I realise the website is based on aero engines, but it is the same concept for every engine. Unfortunately engines can only be run up to a certain temperature before things go wrong, and thats where the cooling system comes into play. If the engine bay is warm, and the cooling is efficient, then a good balance is easier to maintain. A lot of performance engines are therefore run at a higher temperature than the average, an example being BMW engines which run at close to 90degrees, where a Ford Telstar runs at just under 70degrees.