Urgent exhaust heat sheild question

[DrzDick]

Since fitting an S subframe to my E, and loads of grief to make my DEP E tail pipe not hit the spring, it's now getting very close to, and sometimes resting on the engine casing (gear casing). It has already melted a slight depression in the casing from a previous occasion when the bike got "helped" over a tree by the tail pipe.

What can I put between the tailpipe tube and the engine casing to prevent contact & insulate against melting?

I have some exhaust wrap cloth tape but I wasn't sure if that would work as there would be no air circulating.

The other option I can think of is to trap a small flat stone between the two to act as a ceramic spacer.

Anyone got any ideas?

Also this is urgent as I have until tomorrow before my bike get packed into a van and shipped to another country ready for a 2 week riding/camping holiday across Slovenia & Croatia.

Cheers, Rich.

[Noble]

The engine is cast aluminum except for a few covers that are magnesium. Melting is about 1100 deg F. Trust me you are not melting any engine castings. It is possible the pipe is hitting and leaving a mark from mechanical damage. Only solution I can see is move the pipe it adding more braces to prevent the contact. A picture might help.

[DrzDick]

No pictures I'm afriad as you need the pipe off to be able to see the damage from the previous time, and I didn't take any snaps when I first noticed it. I suppose it's possible it's just alloy that has rubbed off and then deposited on the exhaust - does look a little melted though.

No real option on moving the pipe - it's taken me quite a few attempts to stop the thing from hitting the spring. Only other option would be to dent a flat into the pipe to gain some more clearance, or buy another tail pipe that is meant for the S subframe...

I suppose I'll just have to live with it for now then.

[Noble]

Some pipes do use a flat spot for clearance. A stock DRZ400E exhaust has a flat for rear shock spring clearance.

[SteveROntario]

Good hydraulic hose won't melt.

Steve

[DrzDick]

The engine is cast aluminum except for a few covers that are magnesium. Melting is about 1100 deg F. Trust me you are not melting any engine castings. A picture might help.

I have been giving the old girl a good clean up and servicing and noticed that with the previous set-up the melting has continued. This time I took a couple of snaps.

This is the melt patch

and the exhaust showing the alloy stuck too it

Would you agree that my exhaust was actually melting the casing?

I'm putting the E rear-subframe back on now so the clearance won't be an issue, until next time...

[Noble]

That is mechanical abrasion. Not melting.

[DrzDick]

Trust me, it's melting...

Abrasion would leave a smooth surface on the casing. This has an orange peel effect, like lots of mini craters, sort of like the metal has boiled.

The alloy has also been lifted off and deposited on to the exhaust, that part looks as it has been smeared with alloy grease.

The larger mark in the top picture is from when I previously saw this, the second horse shoe and the blip behind it is from my last trip after fitting the S subframe.

I've shown below...

I think we just don't appreciate how hot the front pipe runs, and my bike runs rich. If there is an area that is pressed against a casing it will loose the ability to air cool and the localised temperature will soar.

From what I've seen, Aluminium alloy is not used in exhaust manufacture except as an outer cover for tail pipes as the exhaust packing will protect it from the heat.

I think if anyone was to fasten something made of Aluminium alloy directly to there front pipe they too would find melting had occurred - care to give it a try?

Edited May 30, 2012 by DrzDick

[2WheelsGood]

I think we just don't appreciate how hot the front pipe runs, and my bike runs rich.

Running rich means it's running cooler, not hotter.

[DrzDick]

Running rich means it's running cooler, not hotter.

Yep, I just felt I should mention that before someone suggested that my bike might be running lean.

[2WheelsGood]

Yep, I just felt I should mention that before someone suggested that my bike might be running lean.

Either way, I'm with Noble. The spot in question is roughly half way through the exhaust system. There's no way it's hot enough at that point to melt aluminum. Think about it... an MRD exhaust canister is made of aluminum. If those aren't melting, there's no way your engine cases are. That spot is the result of vibration.

Look at it another way. The hottest point of the exhaust stream runs maybe 1500 degrees at wide open throttle under full load. Now that's measuring the exhaust stream itself inside the pipe up near the exit of the head... again under full load. So even if you could ride it sustained at wide open throttle for a long period of time, by the midpoint in the exhaust system on the outside of the pipe it's not even close to hot enough to melt aluminum.

[DrzDick]

Okay guys, I think we're gonna have to agree to differ here.

If you could see and touch the marks I believe you would agree they're melt marks and not abrasion. We don't know the exact composition of the magnesium alloy in our engine casings so without that can only guess at what the melting point may be. We also don't know what the surface temp of the front pipe can get too, when covered, so it's pointless trying to guess. One thing is for sure, the gas temperature is capable of exceeding the estimated melt temperature of some (or all) aluminium alloys so we can safely say it's possible?

I know that if I run the previous set up again (S subframe & DEP tail pipe) I need to do something to protect the engine casing from the exhaust pipe.

Any ideas?

Steve - hydraulic hose is a little larger for this area.

I could wrap that section of pipe in heat cloth I suppose... or get another pipe that suits the S mounting positions better.

Edited May 31, 2012 by DrzDick

[Craigo]

I suppose you have tried elongating or modifying mounting points to help with fitment..

You may have to do some indenting so that everything has clearance, You don't need much , just so it's not touching anything

[JAKOVASAURUS]

Is this a rare problem people are having? I have the same thing on my motor as OP does. I know a lot of people have the Yosh TI pipe, which is what did it to mine. I'm not really worried about it though unless someone tells me to be.

[Noble]

Holly crap. The pipe has been resting on the motor cases for a long time to wear it that bad. True it has not really hurt anything at this point but I sure would work to relocate the pipe to clear the motor cases. And just to re-affurm. it is mechanical wear (abrasion) not melting.

[JAKOVASAURUS]

Yeah it's been on there for about 7 years. Definitely shocked me to see it and I'm definitely going to find away to make some clearance. I am no chemist or metals expert but my first thought was that it was melting also. It doesn't have a "grinding" look to it and also how would it do that when the motor and pipe are fixed in relation to each other. I'm more shocked than anything that more people aren't seeing this on their bikes. Maybe it has something to do with the passenger peg eliminator that I bought.

[ohgood]

Trust me, it's melting...

Abrasion would leave a smooth surface on the casing. This has an orange peel effect, like lots of mini craters, sort of like the metal has boiled.

The alloy has also been lifted off and deposited on to the exhaust, that part looks as it has been smeared with alloy grease.

The larger mark in the top picture is from when I previously saw this, the second horse shoe and the blip behind it is from my last trip after fitting the S subframe.

I've shown below...

I think we just don't appreciate how hot the front pipe runs, and my bike runs rich. If there is an area that is pressed against a casing it will loose the ability to air cool and the localised temperature will soar.

From what I've seen, Aluminium alloy is not used in exhaust manufacture except as an outer cover for tail pipes as the exhaust packing will protect it from the heat.

I think if anyone was to fasten something made of Aluminium alloy directly to there front pipe they too would find melting had occurred - care to give it a try?

softer metal transfers to harder metal when it's rubbed against each other.

your pipe would have to be very bright orange, almost white, and no oil circulating below for it to melt the aluminum/mag/whatever.

[DrzDick]

aha, this thread has re-surfaced. I wondered if it ever would.

I'm still adamant it's melting, so that's 2 of us that have had it and we both of think it melting.

I did some checking up afterwards and came up with this info..

Properties of Magnesium alloy

States the Solidus temperature is 540 DegC & the full on melting temp of 615 DegC for those particular alloys.

Here is the colour temperature of steel chart

The header when stationary on tickover often glows amber at night - this equate to roughly 500-600 DegC I would guess?

Is it so hard to believe that when the engine is at high revs, pumping a full chamber of hot exhaust gasses each time, that the header and mid pipe have the potential to achieve a surface temperature in excess of 600 DegC if not cooled?

At the point the mid pipe touches the engine casing no cooling air can pass - thus it gets hot!

It might be that the conductive cooling of the engine casing is enough to stop the alloy reaching melting point.

It could also be that there is temperature gradient across the thickness of the engine casing which means that the surface (or contact point) is not being sufficiently cooled so the surface is melting.

It may also be that the mid pipe is rubbing the engine casing, and that once an alloy powder is made it then melts and sticks to the exhaust.

Either way... (and trust me on this) the engine casing is melting and in my case it was being transferred on to the mid pipe.

[ohgood]

get a laser thermometer.

no ?

ok, jam some pine firewood between the case and pipe (flashpoint 572F/300c) and see if it flames. i'm betting all you get is some piney smells, not even a puff of smoke. you're well over firewood's flashpoint in your theory of 1000F.

[MR Honda]

Melting , rubbing, what ever the damage...it's basically your fault for not paying attention. Starting an internet argument with people trying to help you is pointless.

More people with larger pipes do not have this problem. I had to play with my Muzzy quite a bit so it cleared everything without "dent-forming" my pipe. But I was tempted to bring out the hammer!

Next time don't let the pipe touch anything.