ESE's works engine tuner

[kel]

Close, but it's the matching racing stripe of Kel's hat, his t-shirt and the back of his leathers that make it.

The things that other people notice. Would seem I have a subconscious predilection for blue with white stripes

The wrap starts 4 inches down the header pipe and is primarily there to shield heat from the crankcase, gearbox and the gearbox oil cooler Did not notice any real change in power delivery on the dyno (bike has lost almost 1 hp but thats down to a lack of maintenance)
The ducting currently only comes as far forward as the triple clamp with sections cut out to allow the forks to turn. Eventually the number board will be molded and extended so there is a continous ducted path to the cyliner and head. Ideally the cylinder would be completely enclosed with the duct extending/exiting into the low pressure area behind, but the head is hard up against the RS frame rails so not possible. See the old NACA papers for design and test data.
Also to note is that the wheel guard has an upwards curve at the back (kick up) so the air is directed to the cylinder rather than being dragged down by the spinning wheel.
Motor was sand blasted and had a copper plate base gasket formed into a cylinder shroud.
Bike hasn't suffered heat stroke since these mods, but then it's only making 27hp.

[RomeuPT]

There is only two main reasons to be using thermal wrappings on 2T pipes.
The first as was done by Aprilia was to stop the radiated heat from getting at the crankcase/gearbox.
Then the second is to reduce the effect of cool air flowing over the pipe and lowering the wall temp.
This is also done by many race teams by having carbon shields over the exposed parts of the pipe hanging out in the breeze.
Another is mainly due to the second one, but as the pipe heat is retained by the wrapping - the effective tuned length is shortened
due to the increase in wave speed - and this can be used to increase the overev power.
But then this really indicates that the pipe is too long to start with.
Bikes like the RZ/RG500 need to have longer pipes on the rear cylinders, as there is no cooling air over them - unlike the bottom ones that
are cooled by air thru the fairing, but also by the air down the sides.
But as there is never a free lunch, the retained heat due to wrapping will maintain that heat over a much longer period and
this then also looses a heap of bottom end power as well.

An unwrapped or uncoated pipe will drop its wall temp quite rapidly on the overun into corners ( titanium does this even better ) and gives
a natural increase in lower end power when getting back on the gas.
All this is very hard to replicate on the dyno - except to say that I have tested several pipes on the dyno with air flowing over them, and the customer has subsequently had them coated
( usually for the visual effect only ) and then reported that the pipe had lost all its bottom end.
After being given stick for doing it wrong, they grit blasted the ceramic coating off the pipes and they responded exactly as originally designed.

Last issue is be aware that wrapping the header up near the flange is a very bad idea - it overheats the return plug of A/F sitting in the duct - and Mr Deto arrives quickly afterward.

Will this mean that doing an alloy or copper exhaust flange with cooling fins may increase some power? Or even most cylinders would benefit from a longer exhaust duct surrounded by water cooling?

Rule of thumb for the lenght of the duct seems a little more than the piston diameter, what can you say about this wob? Thanks

[wobbly]

Yes, cooling the flange certainly works a treat.I havnt tried it using fins etc, but have modified engines that allow access to water easily, back behind the flange face.
I have drilled pairs of holes directly from the flange face back into water, and then cut slots in the Ex flange and the cylinder flange face to cool down the spigot.
This has a remarkable affect, and if it was done properly like we see in the Jetski world that have water all around the duct right up to the flange
face, then the positive effect would be even more marked.
No I dont think having a "long " cooled duct is the go - we are simply trying to keep the slug of A/F in the area adjacent to the piston relatively cooled
down, so when its rammed back in at the last moment, we dont have hot gases combining with those above the piston and causing deto.
Coupled with this we are wanting to use as much energy in the expelled gases to be doing work in the pipe, not wasted heating up the radiator water system.

[speedpro]

Given the time the slug of gas is in the exhaust duct before it returns to the cylinder I'm curious just how much it is affected by a hotter or cooler duct/header. It seems there would be very little time available for the cool slug of fresh fuel and air to actually absorb any heat. Back to back tests is the obvious method to determine an actual benefit from cooling. Additional coolant circuits that could reduce the cylinder temp in general seem a more lilkely explanation to me

[TZ350]

I put together a bit of a photomontage of Neil’s many many projects i haven’t put them in order yet. One word describes Neil ...........Prolific

http://www.kiwibiker.co.nz/forums/al...p?albumid=4864

if you can't see the album don't blame me.

Its worth the visit ......

[Frits Overmars]

Also to note is that the wheel guard has an upwards curve at the back (kick up) so the air is directed to the cylinder rather than being dragged down by the spinning wheel.

Is that wheel spinning backward? That would be very bad for the tire .

[kel]

Is that wheel spinning backward? That would be very bad for the tire. Or are you riding backward? That would be very bad for the other riders.

I realise it sounds completely counterintuitive, but you can't argue with the thermal images. Maybe the air flow was sticking to curve of the original wheel guard

[Frits Overmars]

I put together a bit of a photomontage of Neil’s many many projects i haven’t put them in order yet.
One word describes Neil ...........Prolific http://www.kiwibiker.co.nz/forums/al...p?albumid=4864.

Its worth the visit ......

Amen to that!

[seattle smitty]

Interesting to hear the effects that Wobbly saw with the thermo-wrap, and that seem not to have happened very noticeably in Kel's experience. Wobbly, one of the happy situations for outboard racer is the ease of making pipes and altering pipes. Currently most of the motorcycle-sized (125-1100cc) racing engines are opposed-twins or opposed-fours with the cylinders crosswise to the boat, carbs in front, expansion chambers pointing straight aft, supported with brackets. Not only far simpler to build than bike pipes, but we can incorporate sliding sections into them, typically a section about 4 1/2" long right back of the flange that bolts to the cylinder. Coming off a corner, with engine revs down, we have the pipes slid back to maximum length (they're cockpit-controlled, usually via a foot-pedal or a lever). As the boat gains speed heading down the straightaway and the revs come up, we pull the pipes forward, shortening them. Aren't you envious?!!

What's more, since we have a whole lake-full or river-full of water to put to use, we also have a push-button on the dash to spray some water into the pipes to make them act like they are even longer. Outboards have no transmission, and can always use some help getting the boat on-plane and accelerating up to where the pipes start to come in tune. So during that plane-off period we're injecting the water into the beginning of the diverging cone to slow the waves down and make a low-rpm pipe. Alky-burning outboards gradually started using expansion chambers from the early-'60s (other guys continued with open megaphones and often big percentages of nitro) and by the late-'60s were starting to get into slider-pipes, with the water injection coming into widespread use a little later.

So that's a long way of saying that where the thermo-wraps might cost you the bottom of your powerband, in outboards we are able to cheat our way around that to some extent.

Actually, with quite a few 2-stroke bikes you could build-in some adjustability like ours (and for all I know maybe some of you have tried this long-since). This would be by putting a sliding section in the fat, straight-sided section between the diverging cone and the baffle cone, something that the kart racers were doing by around 1970 or so (don't know if they still do it). The karters had a rule against this being driver-adjustable in the middle of a race, which is just as well (for them or you), but the sliding section meant the pipe was easy to adjust between heats, and you could get a lap-times comparison.

As to the inadvisability of using wrap on the first several inches of the pipe, something the snowmobile racers might have been the first to discover the hard way, I have been exchanging PMs with TZ350, who was trying ways to address an overheating problem (about 980 pages back; geez, I have a lot of reading to do!!). As I said to him, welding just one or two cooling fins on the first several inches of the front of the exhaust header pipe as it comes out of the flange could easily double the surface-area of the header-pipe for heat-shedding purposes, if that helps . . . .

[koba]

Thanks for all your helpful replies re Devcon for transfer ports.
I'm sorry that I forgot to mention the the motor is water-cooled and the cylinders I am modifying are cast iron.
Does that make a difference to the choice of compound?

I have a tub of the Steel Devcon if you want to use some.

[lodgernz]

I have a tub of the Steel Devcon if you want to use some.

Oh thanks Malcolm. I'll talk to you on Sunday at the track.

[wobbly]

Re the cooling of the spigot.
As we already know that wrapping a header will instantly cause deto from overheating the slug, then the heat uptake in that area for sure
has enough time to wreak havoc.
So by inference a cool duct would also have time to cause a positive effect.
But I well know assumptions are errors waiting to be revealed, so hard evidence is needed.
I just happen to have that, as I have been drilling holes and cutting slots into the flange faces of KZ2 castings the results are easily seen and repeatable.
On track the simple mod reduced the egt by around 30*C - a jet size spot on.
So now we run 1 jet leaner over the original dyno baseline weather corrected RAD, and can run all day at 640C with no deto.
Absolutely impossible previously.
The bulk cylinder water temp is the same as before at 45*C exit, but on the dyno it is now possible to touch the flange bolted to the cylinder,after a hard all
gear run up.
Previously it was way too hot to do this.
At the time I didnt recognise that I could have leaned it down on the dyno - and make more power, but on track the data log was immediately conclusive.

I am sceptical about cooling the header with heat radiating plate fins or whatever, as this would be detracting from the pipe heat energy available - BUT, it may be a workable
compromise if the duct cannot be kept cool enough - for whatever reason.

[Yow Ling]

So how far down the header does the mixture extend before being pushed back into the cylinder ?
A bit of an open ended question as different states of tune and different porting will have different outcomes.
Are we looking at 50mm past the flange or something else?

[wobbly]

It varies obviously but back in the days of being able to run leaded racegas, and nowdays in bikes only where Avgas is allowed
we see the white lead burn mark in the header from 50 to 100mm down the length.
So I would surmise that there is sufficient unburned,cool A/F mixture in that part of the header that is absorbing heat to the point
that the wall temp is low enough not to show any burn mark.
The dividing line is always VERY clear, a real start/stop line to the hot/cold areas of the header.

[Frits Overmars]

... one of the happy situations for outboard racer is the ease of making pipes and altering pipes. Currently most of the motorcycle-sized (125-1100cc) racing engines are opposed-twins or opposed-fours with the cylinders crosswise to the boat, carbs in front, expansion chambers pointing straight aft, supported with brackets. Not only far simpler to build than bike pipes, but we can incorporate sliding sections into them, typically a section about 4 1/2" long right back of the flange that bolts to the cylinder.

Like so, Smitty ?

with quite a few 2-stroke bikes you could build-in some adjustability like ours. This would be by putting a sliding section in the fat, straight-sided section between the diverging cone and the baffle cone

There are several options in lengthening a pipe. You can move the end cone, or you can lengthen the header, like on the trombone pipe in the video below.

The gas pressure generates a force that is proportional to the cross section area of the moving part and proportional to the pressure difference at either side of that area. For a moving end cone this force can be up to 4 times larger than for a sliding header. That is one reason to go for the trombone system rather than the moving cone system.

The second reason: sealing. The circumferential gap that has to be sealed, is three times shorter for the trombone system. That means three times less leakage and three times less friction.

The third reason: say you wish to lengthen the total length of the pipe by 10 %. If you do it by moving the end cone, you will also enlarge the pipe volume by a little over 10 %.
But in a good pipe configuration the header length is about 1/3 of total pipe length, so in the trombone system, lengthening the pipe by 10 % will be done by lengthening the header by about 30 %. That gives a far greater variation in the pipe's Helmholtz frequency than a 10 % volume change.

It is true that the length percentages of all pipe components should be in a rather fixed relation to each other. Varying the lengths of all components by the same percentage would be the theoretical optimum, but that is not feasible.
Lengthening the belly will disturb the optimum relations, as will lengthening the header. So the pipe in its lengthened version will not be the optimum for the low resonance rpm dictated by the length. But it will be a hell of a lot better than using an exhaust power valve that spoils the 180° effective exhaust timing, necessary for true resonance.
And a pipe shortened beyond its optimum may not show the optimum length relations between its components either, but it will be a lot more effective in overrev than artificially raising the exhaust gas temperature by retarding the ignition, or by weakening the mixture strenght through closing a power jet, which has the disadvantage that not all inhaled air is used for combustion.

Trombone pipe: http://www.youtube.com/watch?v=0odVz...ature=youtu.be