does anyone know what the exhaust temp is at it's hottest spot?

 

Depending on how hard you run it, the EGT can reach close to 2000 degrees near the motor. 1000-1400 or so is normal for regular riding. Depending on other variables, it could be lower or higher and the hotspots will be closest to the motor, turns in the pipe, and sometimes the catalytic convertor, but newer higher flow cats tend not to heat up as much as the older ones.

The actual hottest spot could be significantly hotter than that, if you could find a way to measure it.

 

egt gauge

 

thanks for the help guys.

 

Not questioning your answer but isnt the melting point of Aluminum like 2000 degrees?

 

Yes, even lower actually. Pure aluminum has a melting point of about 1300 degrees. Aluminum alloys are used in the motors. I couldn't tell you the exact makeup but most alloys contain zinc, copper, and silicon to raise the heat tolerance.

 

Ty i am calling you out on this, When you mix metals in an Alloy such as Aluminium,silicon and copper,(most engine cast parts) the overall melting point is reduced, for example AL @ 1220F mixed with Cu (copper) 1984F, the overall melting point is reduced. I don't have a Phase diagram to show you, but it is what happens, The reasons alloys are used is for light weight, and cheaper manufacturing cost, The alloys are used typically to add strength to the aluminum.nothing really to do with heat.

"Why dosn't it melt?" you may ask Well it is simple really, Aluminumis a goo dheat conductor, and it actaully dissapates heat rapidly. One thing i deal with, with jet engines is exhaust temps of around 3500F and themetals touching them usually read about 65% of that. just to fill your details a little more.

 

Yes, what he said. Conductivity was the word I should have used. The silicon increases the heat conductivity of the aluminum, right? Or are the other elements there for strength alone?

 

Chemical Oxidation
1350 - 1475 F
730 - 800 C

Annealing furnace
1,100 - 1,200 F
590 - 650 C

Fluidized-bed combustor
1,600 - 1,800
870 - 980

Natural-gas fired heating appliance with draft hood
360
182

Liquefied-petroleum gas-fired heating appliance with draft hood
360
182

Gas-fired heating appliance, no draft hood
460
238

Glass melting furnace
1,200 - 1,600
650 - 870

Oil-fired heating appliance, residential
560
293

Oil-fired heating appliance, forced draft over 400.000 Btu/h
360
182

Conventional incinerator
1,400
760

Controlled air incinerator
1,800 - 2,400
982 - 1,316

Pathological incinerator
1,800 - 2,800
982 - 1,538

Gas turbine exhaust
700 - 1,100
370 - 590

Diesel exhaust
1,000 - 1,200
540 - 650

Ceramic kilns
1,800 - 2,400
982 - 1,316

Dude based on this chart ima have to ask how a motorcycle exhaust temp would be in the same catagory as incinerators and higher than glass melting?

 

Aluminum alloys, are usually just for strength, and less $cost$ for the most part. if it was pure aluminium it would actually dissapate heat faster, that is what i deal alot with in the jet engine world, For security reaons i can't disclose materials but, we actually try to create coatings that hold heat, if exhaust temp is 3500F we want the metals in that part of the chamber to heat up as much as possible. basically creating a more efficiant engine. In a 3500F combustion chamber the inside of the surrounding wall is more like 1900F. break that down to motorcycle engine and a 1200F combustion chamber the surrounding wall is probably around 600-900F. This is partialy due to a thin layer of gasses that act as a protector/insulator for the metal.

as far as what BBOI says, nothing special going on in a JET engine or furnace, they run of similar fuel. For example "jet fuel"= K1 kero.(basically) it just burns cleaner. And furnaces for example are creating constant heat, engines fire rapid cycles, cycle 1 combustion cycle 2 moves air, even though it is very, very fast it actually allows these metals to cool slightly between combustion cycles.

three thing to know about Turbine engines "suck, bang, blow"