ESE's works engine tuner

[Flettner]

My spies sent me this as well, email was titled "from web forums to serious competition"

Thought it might be the FOS in action?

[F5 Dave]

search Wobbly posts, he uses .8 mild steel (hot rolled maybe) given that he knows his shit about pipes , I would just copy him
1mm costs power, ceramic coating costs power, ss needs to be longer.

You can often find scrap chromated sheet that will deter rust (except where you weld). Don't use it, it will crack regularly. Don't ask how I know.

[Ocean1]

And why not the good old 306 or 316 stainless?

316 in high frequency load applications work hardens quickly around stress risers, (joints), causing cracks.

Cold drawn 1.5mm 304 is used for automotive exhaust work, but for a chamber I suspect you'd have the same problems as with 316, a little less quickly maybe but I wouldn't bother.

Corten is stiffer, so you could theoretically use a thinner section, but that stiffness also tends to focus harmonic distortion at the joints, again promoting cracking.

Mild steel might have been around for a while, but there's plenty of applications where it's still a more than effective choice of material.

[koba]

Unpainted 0.8 Mild steel also lasts a long time if it's in a race situation, if the bike isn't left in the rain between rounds and gets a bit of oil on it from time to time.

I'd expected to chop and change a bit but it hasn't happened yet.

[Frits Overmars]

1mm costs power, ceramic coating costs power, ss needs to be longer.

Ceramic coating shouldn't cost power; on the contrary. You'd just have to adjust the lengths, like you have to with stainless steel and titanium.
This graph shows the results of three pipes with identical dimensions but different materials on the same engine.

Stainless is kind a nightmare to make properly...

Then try this, Romeu. That should keep you out of the boozer for a couple of evenings .

[senso]

It is not a nightmare with the right tools..
I have seen a friend of mine roll 17-18 cones in 316 stainless in 20 minutes, ready to tack, test fit and weld, in a normal day, a pipe takes 2 hours from plate to pipe..

[F5 Dave]

Ceramic coating shouldn't cost power; on the contrary. You'd just have to adjust the lengths, like you have to with stainless steel and titanium.
This graph shows the results of three pipes with identical dimensions but different materials on the same engine.


Then try this, Romeu. That should keep you out of the boozer for a couple of evenings .

So what of the insulation properties on the header? Is that not why wrapping became unpopular in that area? My own pipes that have been ceramic costed changed considerably in peak revs for 250 size bore but much less on a 50cc. I now avoid doing it.

[Frits Overmars]

So what of the insulation properties on the header? Is that not why wrapping became unpopular in that area? My own pipes that have been ceramic costed changed considerably in peak revs for 250 size bore but much less on a 50cc. I now avoid doing it.

The first part of the exhaust duct, where washed-through fresh mixture waits to be shoved back into the cylinder, should be as cold as possible. The rest of the pipe can be isolated without any ill effects, provided the pipe dimensions are adapted to the increased heat retention.

[koba]

The first part of the exhaust duct, where washed-through fresh mixture waits to be shoved back into the cylinder, should be as cold as possible. The rest of the pipe can be isolated without any ill effects, provided the pipe dimensions are adapted to the increased heat retention.

How far down would that be?

Would it be worth some extra cooling effort here perhaps, such as finning or even water cooling?

[jasonu]

, in a normal day, a pipe takes 2 hours from plate to pipe..

Maybe in a mass production situation.

[senso]

The flange is already made(usually he makes 10 a time, to save on setup time in the lathe), the sheet is laser cut, had a custom made cone roller, and presto.

[TZ350]

The first part of the exhaust duct, where washed-through fresh mixture waits to be shoved back into the cylinder, should be as cold as possible. The rest of the pipe can be insulated without any ill effects, provided the pipe dimensions are adapted to the increased heat retention.

How far down would that be? Would it be worth some extra cooling effort here perhaps, such as finning or even water cooling?

I am very interested in this too....



At first look, it looks sensible to have a short exhaust tract to cut down on heat soak into the (air) cooling system, but this may not be the best. A longer tract or better yet a finned cooling muff around the top part of the pipe.

I would be interested in any thoughts on this.

[TZ350]

While she in doors has been doing some heavy duty shopping I found my way to https://www.treatland.tv



Here in San Francisco the guys at Treatland supply all sorts of parts to the world for building up street or performance/race Mopeds. They modify and race their own bikes.

Benji made me feel welcome and showed me around.

I have brought parts, mostly carbs from here before, they can send stuff anywhere around the world.



https://www.treatland.tv/SearchResults.asp?Search=cdi

Its worth having a look at their stock, the ignitions are pretty interesting, very small size and as well as CDI they can have a generator coil too. Carbs and performance cylinders are pretty attractive to. Any of this stuff they can send to NZ no problem, my experience is it takes 7-10 business days for delivery to your door.



A couple of the guys own race bikes that they have modified themselves.



This one has a European frame, Honda engine and an Italian cylinder/head kit, hmmm I think I remembered that right. Interesting ignition.



And old base engines. If I lived here I would be right into one of these neat little bikes.

[Frits Overmars]

The first part of the exhaust duct, where washed-through fresh mixture waits to be shoved back into the cylinder, should be as cold as possible. The rest of the pipe can be isolated without any ill effects, provided the pipe dimensions are adapted to the increased heat retention.

How far down would that be? Would it be worth some extra cooling effort here perhaps, such as finning or even water cooling?

Keeping the exhaust duct in the cylinder as short as possible to prevent the spent gases from heating up the cylinder too much was once considered good practice, and for aircooled cylinders it may still be the case; I can't say because I have no recent experience with aircooled competition engines. But for watercooled cylinders it is definitely worth cooling the first part of the exhaust duct as much as you can.
The length of this first part should be such that it can contain a volume equal to one cylinder capacity. Obviously the smaller the local duct diameter, the larger this length needs to be.
I already stressed the importance of a small duct diameter before. Here is another reason: the duct's cross area is where fresh charge and spent gases mix. Keeping this area small lessens this undesirable mixing.

[RomeuPT]

Ceramic coating shouldn't cost power; on the contrary. You'd just have to adjust the lengths, like you have to with stainless steel and titanium.
This graph shows the results of three pipes with identical dimensions but different materials on the same engine.


Then try this, Romeu. That should keep you out of the boozer for a couple of evenings .

I already did a pipe for a CR 500, a total of 40 pieces of mild steel, tired of working with cones.

Making a 14 cones pipe in 304 stainless was the maximum until now, and it takes the whole day...... if everthing runs fine!!!

It is not a nightmare with the right tools..
I have seen a friend of mine roll 17-18 cones in 316 stainless in 20 minutes, ready to tack, test fit and weld, in a normal day, a pipe takes 2 hours from plate to pipe..

roll is a thing, tack and weld in a proper way is another...