Exhaust Section

[wayne]

I've been wanting to do this for a loooong time. Did some restoration for a friend and this was part payment.....sacrificed his old pipe.

I'm yet to split the inner pipe, the stainless wreaked havoc on my cutting discs and I've got to buy some more to finish the job.

But in the meantime:

[wayne]

Okay, perhaps I've done everyone a diservice now. Despite being told that there was no wadding in the pipe by someone who claimed to have sectioned one about 10 years ago, there IS wadding.

Still, I've had pipes chromed with no problems in the past.

Perhaps that bloke wasn't mistaken, perhaps they had wadding in some and not in others.

However, this is an early model pipe from a steel oil line M model and with the large diameter pipe "stingers". They went to small diameter stingers, I believe, to reduce noise. Therefore if they had wadding in this early model pipe, I suspect that they had it all the way through.

The wadding as it appears has come apart, there is a wire wrapping that's uncoiled. This is how I found it in the pipe.

Note also that the perforated "Stinger" in the tail is usually wrapped with some sort of thread like wadding material which has been removed for the photo. But the stinger is of course removable unlike the inner wadded section.

[Jess]

Very nice Wayne...

Thanks for sharing and doing us all a service.

Cheers

[timpa136]

Interesting, I've never seen the internals.
I don't see the high pressure flapper valve that they advertised for sure in the A models that bypassed a big portion of the baffle for performance. Well built insides for sure.Thanks Wayne.

[wayne]

I came across mention of this so called flapper valve in early test reviews and then mention of it seemed to disappear. But as you say, apparently not in this pipe at least.

Also I note that you could fill up the very tip of the pipe with insulation material as long as you left a hole for the stinger to slide down into.

I've been wondering about doing that but didn't want to disturb the cool air flow. I can see from the section though that the cooling air is "captured" before the last 6" and funneled into the stinger.

In another thread I detailed packing the tour kit exhaust extensions and noted a reduction in noise. I think I might try packing the end of the pipe as well.

[Deleted]

Hi mate,

No wonder it was such an expensive bike in it's day, the pipe is quite elaborate. From what I can see I agree with you with the amount of wadding in it really wouldn't worry the chrome platers. Can you tell us, where the wadding is wrapped is that stainless or steel?

Mike

[wayne]

Hi Mike and welcome to the board. The inner pipe, despite its rusty appearance is pretty much all stainless. The wadding was wrapped on the inner perforated tube.

The only part of the inner pipe that is not stainless is a 1 cm wide strap that you can see in the very last picture. In the photo it has a shiny bit on it with two spot welds (which is a part of the outer pipe that I couldn't cut away). All it does is support the inner pipe concentrically right at the back.

The outer perforated tube is called, officially, the "Spark Arrestor" and is the bit that is held into the end of the pipe by 4 screws and it is removable.

[HGH 770N]

Spot on info , Wayne , Thanks

I will show photos to a stainless pipe maker and see it he could re skin pipes.

There are a few guy's over here that have no issues in re-choming these pipes,
I will try the extra wadding in my early pipes and see what happens.
Best
Rog

Attachments:

[stevejones]

I took the wadding off the spark arrestors on mine very early on in the piece. it made it sound great (My young mind thought at the time) and you got great flashes of flame out the pipes on the over run. Guess i was young and silly then.

[wayne]

So they really were "spark arrestors" ?

One guy in the general circle of riders back in the day thought it was great fun to flip the kill switch on the RE5 and this caused a huge backfire. Certainly got our attention but probably doing all sorts of subtle damage.

[wayne]

For info, I packed the rear of the pipe with the same material I used in the add-on cones, Rockwool, an acoustic household insulation made from spun Basalt.

Waste of time. While packing the cones did reduce noise by a measurable amount by DB meter, packing the pipe itself did nothing from the rear at both idle and 4000 rpm. Perhaps the noise footprint from the side might be improved, I didn't check. Don't bother with it.

[ap951]

thank you for doing this Wayne, I've long wondered just what exactly was inside and you gave me an education

Bill

[wayne]

Here's some more exhaust trivia. I had to cut up a badly damaged pipe to fit in my garbage bin and answered a question that's disturbed me for some time. It's there in the preceding photos but not at all obvious.

I've picked up some pipes and they make a clunking sound. Some don't. The clunking was happening somewhere in the first third. Given that the supports are mostly welded, what can possibly be going on ?

Probably just this. The inner pipe is not one piece. just after it curves out of the exhaust manifold and starts to run straight, the inner pipe is cut and is actually two sections. It's joined by nothing more sophisticated than a smaller diameter inner tube which is only a tight fit in one end. Perhaps it's welded into that end, I can't see. The back half of the pipe merely slips over this and the whole thing is spaced away from the walls of the outer pipe by 4 small tubular bits of metal that are only solidly attached to the inner pipe.

Given some years of heating and cooling etc, it gets a little sloppy around that join and if you rattle some pipes, you'll hear it. Nothing to worry about.

This is the back half, you can just make out the edge of a heat shield in the bottom right of the photo (reference it to previous shots of the full pipe):

[ski]

Thanks for taking the time to section one of the exhaust pipes. Being able to see the inside of the system, clarifies how it actually works and helps to understand how previous misconceptions of 'scavenging' can come about. The system does in fact, scavenge, but not in the way scavenging occurs in a normal exhaust system. A normal exhaust system should operate efficiently/correctly with no pressure or a maximum of 1 psi. An optimal system should actually operate with a vacuum. As the exhaust gasses pass through the system, they cool. This means that the same number of molecules can occupy less space in cool exhaust than in hot exhaust since molecules expand when heated and contract when cooled. That causes a vacuum as the molecules cool and contract which also causes an acceleration (forward motion from the entrance of the exhaust to the exit of the exhaust) that allows the gasses that were originally under pressure to now 'pull' gasses from the front of the system reducing the amount of pressure at the manifold. In a optimal system, this causes the exhaust gasses to be pulled from the combustion chamber instead of exiting due to pressure. Exhaust gasses under a vacuum exit faster that gasses being forced out through pressure leaving less of that gas in the combustion chamber and allowing for more air and fuel from the intake event to enter the chamber resulting in more energy from the combustion event. HOWEVER, our system scavenges cold air from outside the system, not exhaust gasses within. The cone you can see in the pictures at the rear of the system causes a venturi effect which draws cold air through the intake at the front of the pipe and through the outer exhaust pipe shell to cool the shell. This only applies to the exhaust system of an RE5 since no one else ever used this type of system. The RE5 system is optimal when the bike is in motion as colder, more dense air at the intake is pushing on the intake. Ever notice how you can smell more exhaust when you're sitting at idle? It's because the pressure pulses from the exhaust overcome the venturi effect and force exhaust gasses out the intake at the front of the pipe. You can actually pack the intake grate with steel wool which will lessen this effect and quiet the bike, but will reduce the cooling effect on the outer shell. I've done it myself, but it was originally done by someone else who pointed it out to me. The steel wool burns out fairly fast due to the exhaust gas temps so it's not very practical. Given these two types of scavenging for exhaust in regards the the RE5, you can see how someone might confuse them. The colder air from the intake isn't being mixed with the hotter air from the exhaust until just prior to the exit of the exhaust from the system so the effect of actual scavenging (in regards to a normal/closed system) is negligible at best. If the cold air was mixed with the hotter exhaust gasses at say, the halfway point or sooner, they might increase the scavenging effect in the combustion chamber but would also affect the cooling effect of the outer shell.

[h2e Al In Aus]

I love this site so much info , and smart guys that just show everyone what they know and find out , thankyou guys