Scooterotica

sideout wrote:http://www.matweb.com/search/datasheet. ... 001&ckck=1
620-650 for aluminium alloy.

Things to take into account is the position of the probe from the exhaust port and the fact that not many egts are calibrated in situ. I know mine's not

Another aspect is how long you keep the exhaust gas temperature above 620 degrees. There has to be enough time for the piston crown to heat up to its melting point. The cold charge each cycle will help to take the heat away, up to a point

Personally, I'm much happier running an egt gauge on my Mugello 186 and have adjusted the jetting according to the results I've seen.

(apologies for the slight thread highjack )

Cheers,

Nigel

Exactly Nigel.
With the gauge follow the instructions as to probe distance and depth. Thats very important. Now the idea is to prevent the crown reaching its melting point of course.

Nick- yes but other issue may arise... But try wearing a suit as a suite might look silly

With the little knowledge I have of Aluminium alloys and how they react to heat I know there is a point that the metal stops absorbing heat as before and instead changes state prior to becoming a liquid.

Aluminium has what is sometimes refered to as a "Mushy State", this is the point that the aluminium stops being a solid and begins to become not quite a liquid but not exactly a solid this is where the EGT needs to tell you not to go. The mushy state is the point the piston crown will start to deform or even form a hole in the piston, which under compression of the firing stroke can cause small bits to be blasted away at every firing stroke once the heat range necessary to reach the mushy state for a certain Aluminium alloy piston has been reached.

Some pistons having a slightly higher or lower near melting point than others. When a piston reaches this state the temperature sender may even show a loss of heat as the Alloy instead of heating changes state to a mushy substance. Somewhere around 620- 660C is the mushy state, and approximately 660 degrees C (1220.666 °F) or above, is the liquid melting point for pure Aluminium.
That is, Aluminium becomes a liquid at or above this temperature, but with the adition of other elements (Aluminium alloys) this may be exceeded, but not usually by much...
Just thought I would add some of the little I know to whats been mentioned in this here post...

So what is the safe running temperature for an EGT.????

I edited my post as I checked some old notes I have, and the figures I had given for the melting point of pure alloy was 6 degrees C out, but I knew the 666 was in there somewhere but its in degrees F.

I always refered to it as the Devils metal but the rest seems about right, with some alloys begining to go mushy at a lower temperature than others.

well that 666 sounds like the number of the beast to me mister J1 ,,,cheers for the spec. That saves a few pistons But there you go.. some science from someone who knows. Its the gas that heats the motor. Measure the gas and keep the motor safe.

Good to that if we all put our heads together we may learn about the new technology that bestowes us ,thanks to the forum once again.

J1MS wrote:With the little knowledge I have of Aluminium alloys and how they react to heat I know there is a point that the metal stops absorbing heat as before and instead changes state prior to becoming a liquid.

Aluminium has what is sometimes refered to as a "Mushy State", this is the point that the aluminium stops being a solid and begins to become not quite a liquid but not exactly a solid this is where the EGT needs to tell you not to go. The mushy state is the point the piston crown will start to deform or even form a hole in the piston, which under compression of the firing stroke can cause small bits to be blasted away at every firing stroke once the heat range necessary to reach the mushy state for a certain Aluminium alloy piston has been reached.

Some pistons having a slightly higher or lower near melting point than others. When a piston reaches this state the temperature sender may even show a loss of heat as the Alloy instead of heating changes state to a mushy substance. Somewhere around 620- 660C is the mushy state, and approximately 660 degrees C (1220.666 °F) or above, is the liquid melting point for pure Aluminium.
That is, Aluminium becomes a liquid at or above this temperature, but with the adition of other elements (Aluminium alloys) this may be exceeded, but not usually by much...
Just thought I would add some of the little I know to whats been mentioned in this here post...

So what is the safe running temperature for an EGT.????

I edited my post as I checked some old notes I have, and the figures I had given for the melting point of pure alloy was 6 degrees C out, but I knew the 666 was in there somewhere but its in degrees F.

I always refered to it as the Devils metal but the rest seems about right, with some alloys begining to go mushy at a lower temperature than others.

ive looked into this alot over the last couple years and the melting point is 720c , anyone who says a egt isnt worth it on a tuned lammy spec a rb is very wrong not only will it tell u were u are under jetted it will tell u when u are getting near that magic number !!! so u can back off or wind the throttle open to let more petrol in to cool it down this high temp should only happen at crusieing speed over 6000 rpm if it happens at moderate to slow speeds /rpm then the bike/carb is prob badly setup

Just checking to see if my notes were still up to date, and came up with this from the internet... http://wiki.answers.com/Q/What_is_the_m ... f_aluminum

This melting point is the temperature the aluminium would have to reach to melt, and not the heat of the exhast gasses, which will be much hotter as the alloy has to absorbe heat from the gasses to reach its running temperature or possibly melting temperature.

yes i should hav said 720c on a egt is the temp needed on the egt for the piston to be getting near 660c

Chris CSPE wrote:if your interested in a powerfull tsi for fast road and rallying with plenty of torque give me a call
on 07791220193. C.S PERFORMANCE ENGINES

didnt you build ws9's engines...

i think he used to but they dont get much call for tuned scoots there,i think
they just stick to there quality rebuilds,i think stuart owen has since enquired
about doing some engine builds but had his offer declined

lamy150 wrote:i think he used to but they dont get much call for tuned scoots there,i think
they just stick to there quality rebuilds,i think stuart owen has since enquired
about doing some engine builds but had his offer declined

Sorry mate we only do engines for our own customers and have never spoke to WS9 on the matter check your source next time is my advice. We often get linked to other shops round the country with all the scooter rumour merchants around its a bit boring really.