Exhaust gas temperture

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Exhaust gas temperture

Post by Truckedup » Mon Oct 15, 2018 9:49 am

Having a discussion on gas engine exhaust gas temperature causing blueing of motorcycle exhaust pipes....Most say it's a lean mixture, some say a rich mixture....For this issue its a moderate part throttle like street riding, not full throttle racing......Some of you might have EGT gauges on engines with real life experience on this ? Thanks
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Re: Exhaust gas temperture

Post by pcnsd » Mon Oct 15, 2018 10:05 am

Steels heat blue at temperatures between 550F and 625F. The exhaust gas exiting your chamber is significantly hotter. How is this anything but expected outcome? The only pipes I have seen that didn't blue were double walled.
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Re: Exhaust gas temperture

Post by Truckedup » Mon Oct 15, 2018 11:07 am

pcnsd wrote:
Mon Oct 15, 2018 10:05 am
Steels heat blue at temperatures between 550F and 625F. The exhaust gas exiting your chamber is significantly hotter. How is this anything but expected outcome? The only pipes I have seen that didn't blue were double walled.
Pipes don't always blue because the airflow while ridding cools them.My LSR race bikes run wide open for 1-1/2 miles but don't really blue the bare steel pipes unless the bike does a lot of idling....Some exhaust pipe manufacturers say to avoid excessive use of the choke to avoid blueing....
Some say a lean mixture results in lower exhaust temperature? Some say just the opposite...
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Re: Exhaust gas temperture

Post by cgarb » Mon Oct 15, 2018 11:26 am

Not enough total timing will make them glow orange...lol. Also the plug wire looms melt and the water temp gets hot real fast.

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Re: Exhaust gas temperture

Post by n2xlr8n » Mon Oct 15, 2018 1:59 pm

What I've noticed on my cars is that during steady state cruising with say, 20* total, my EGTs were relatively high.

When I added 3 degrees, they went down.

My experience is that ignition timing has more of an effect on EGT than AFR.
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Re: Exhaust gas temperture

Post by David Redszus » Mon Oct 15, 2018 7:00 pm

n2xlr8n wrote:
Mon Oct 15, 2018 1:59 pm
What I've noticed on my cars is that during steady state cruising with say, 20* total, my EGTs were relatively high.

When I added 3 degrees, they went down.

My experience is that ignition timing has more of an effect on EGT than AFR.
Absolutely correct.

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Re: Exhaust gas temperture

Post by Truckedup » Mon Oct 15, 2018 7:36 pm

Thanks!
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Re: Exhaust gas temperture

Post by Truckedup » Mon Oct 15, 2018 7:51 pm

Truckedup wrote:
Mon Oct 15, 2018 7:36 pm
Thanks!
How would lean or rich affect EGT at higher power ? Lean is hotter?
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Re: Exhaust gas temperture

Post by MadBill » Mon Oct 15, 2018 9:50 pm

One dark zero degree winter's morning many years ago I fired up my Vincent V twin then went back indoors to suit up. When I came out a few minutes later I noticed the front pipe glowing dull red right down to the junction with the rear. I opened the front idle screw 1/2 turn and the glow went away...
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Re: Exhaust gas temperture

Post by 77cruiser » Mon Oct 15, 2018 10:14 pm

Watch the muffler on a Briggs when you turn in the mixture screw with it running WOT.
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Re: Exhaust gas temperture

Post by Truckedup » Tue Oct 16, 2018 6:28 am

MadBill wrote:
Mon Oct 15, 2018 9:50 pm
One dark zero degree winter's morning many years ago I fired up my Vincent V twin then went back indoors to suit up. When I came out a few minutes later I noticed the front pipe glowing dull red right down to the junction with the rear. I opened the front idle screw 1/2 turn and the glow went away...
That Vincent have Amal Monobloc's? Opening the idle mixture screw makes the idle mixture leaner...
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Re: Exhaust gas temperture

Post by Truckedup » Tue Oct 16, 2018 6:33 am

MadBill wrote:
Mon Oct 15, 2018 9:50 pm
One dark zero degree winter's morning many years ago I fired up my Vincent V twin then went back indoors to suit up. When I came out a few minutes later I noticed the front pipe glowing dull red right down to the junction with the rear. I opened the front idle screw 1/2 turn and the glow went away...

That Vincent have Amal Monobloc's? Opening the idle mixture screw makes the idle mixture leaner...Or the manual magneto advance,if fitted, could have been left in the retarded position...
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Re: Exhaust gas temperture

Post by David Redszus » Tue Oct 16, 2018 11:32 am

Truckedup wrote:
Mon Oct 15, 2018 7:51 pm
Truckedup wrote:
Mon Oct 15, 2018 7:36 pm
Thanks!
How would lean or rich affect EGT at higher power ? Lean is hotter?
If the air/fuel ratio is very close to optimum (for specific weather conditions) then a slight change in mixture will produce an almost imperceptible change in EGT.

If mixture is either excessively lean or rich, the burn will occur at a later crank angle. An early burn, as with advanced timing, will reduce EGT but will raise chamber temperature. Late timing, or late burn, will lower piston temperature but will raise EGT.

EGT is difficult to measure accurately and has little effect on a four stroke engine. But EGT is quite important on a two
stroke engine in order to properly tune the pipe scavenge.

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Re: Exhaust gas temperture

Post by MadBill » Tue Oct 16, 2018 3:32 pm

Truckedup wrote:
Tue Oct 16, 2018 6:33 am
MadBill wrote:
Mon Oct 15, 2018 9:50 pm
One dark zero degree winter's morning many years ago I fired up my Vincent V twin then went back indoors to suit up. When I came out a few minutes later I noticed the front pipe glowing dull red right down to the junction with the rear. I opened the front idle screw 1/2 turn and the glow went away...

That Vincent have Amal Monobloc's? Opening the idle mixture screw makes the idle mixture leaner...Or the manual magneto advance,if fitted, could have been left in the retarded position...
No, it was a '53 Black Shadow with 1 1/8" separate float Amals, which had fuel control idle mixture screws. Also it had an automatic advance mag.
Felix, qui potuit rerum cognscere causas.

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Re: Exhaust gas temperture

Post by Truckedup » Tue Oct 16, 2018 7:45 pm

MadBill wrote:
Tue Oct 16, 2018 3:32 pm
Truckedup wrote:
Tue Oct 16, 2018 6:33 am
MadBill wrote:
Mon Oct 15, 2018 9:50 pm
One dark zero degree winter's morning many years ago I fired up my Vincent V twin then went back indoors to suit up. When I came out a few minutes later I noticed the front pipe glowing dull red right down to the junction with the rear. I opened the front idle screw 1/2 turn and the glow went away...

That Vincent have Amal Monobloc's? Opening the idle mixture screw makes the idle mixture leaner...Or the manual magneto advance,if fitted, could have been left in the retarded position...
No, it was a '53 Black Shadow with 1 1/8" separate float Amals, which had fuel control idle mixture screws. Also it had an automatic advance mag.
Today no one starts up a Vincent and walks away unless there's an armed guard standing over it.. :D
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