ESE's works engine tuner

[Sandokan]

Only the part of the exhaust duct that gets temporarily filled with washed-through fresh mixture, needs to be cooled. If we cool a length of exhaust duct, long enough to hold a mixture volume equal to the cubic cylinder capacity, we'll be all right. Cooling the remainder of the exhaust tract would needlessly raise the coolant temperature and entail a loss of exhaust gas energy, reducing the good work of the pipe.

Has it ever been tried to thermaly isolate the exhaust from the cilinder?
I suppose most heat transfered from exhaust gas is passed to the metal of the pipe by Radiating.

[Frits Overmars]

Has it ever been tried to thermaly isolate the exhaust from the cilinder?

Ages ago, with asbestos gaskets.

[Matt@TYGA]

As i´m building a new pipe for my 211cc engine, could it be worth it to build a waterjacket, say first 100mm on the header?

A friend of mine has fitted a 110cc boxer engine into a homemade surfboard. Running just straight pipes, into a silencer box, and out the back of the board. We jacketed the pipes, basically to try to keep the temperature down inside the engine compartment. How much is jacketed and how much water runs through the jacket makes a big difference on the power output.

But then again, he's also been playing around a lot with the prop pitch and nozzle diameter that it's a bit difficult to keep up with it all!

[jbiplane]

Hi guys

I produce my own cylinders by cnc milling and coat them by nikasil which works ~250 hours at 8000 rpm.
Tried to make nitrided steel liners of 40cr, survive just 50 hours.

Could anyone recommend me something better, but realistic for small production
- best possible for coating
- best possible liners material?

Valery
Aviamech llc
jbiplane@gmail.com

[Frits Overmars]

Hi Valery, there are many ways of preparing cylinder bores, but I have no personal experience with them, apart from chrome (not usable in combination with chromed piston rings) and nikasil.
But I wonder: why use steel liners? You can chrome or nikasil those too, but the contact surface between the liner and the cylinder casting will form an undesirable thermal resistance. And even if you use wet liners, the steel itself will form a thermal resistance.

[jbiplane]

why use steel liners? You can chrome or nikasil those too, but the contact surface between the liner and the cylinder casting will form an undesirable thermal resistance. And even if you use wet liners, the steel itself will form a thermal resistance.

My objective is create lightweight hybrid electric-ICE engines. The best numbers I achieved is 26hp ICE with 5kw alternator-starter which weight 9000 grammes and low resource. Want make something better...

[Tunisti]

Tried to make nitrided steel liners of 40cr, survive just 50 hours.

Could anyone recommend me something better, but realistic for small production
- best possible liners material?

Hi,

I'd recommend using GGG50 aka. EN-GJS-500-7 ductile cast iron bar. If I've understood right the steel liners have problems with lubrication, especially when used in two-stroke applications. Cast irons have self lubricity due to the graphite witch is distributed in the metal matrix. In this case the graphite is in nodular form, but it can also be in flake-like form, ie. GG25 grey cast iron. The self lubricity of grey cast iron is a bit better, but on the other hand it's mechanical properties aren't so convincing.

Of course there are these fancy spun cast industrial liners, but they're not available in Finland - so we use 3000*60mm EN-GJS-500-7 round bar. It costs about $250 including shipping&taxes, so material cost for one liner is less than $10.

About 60kg



Machining




Ports etched



I'd love to hear if someone has tried "thougher" nodular cast irons, ie. GGG60 or GGG70? I reckon that the self lubricity decrease too much, even though the mechanical properties are enhanced?

By the way, when cutting off the transfer duct openings from the liner above, I decided to do a little testing. I cut off two 25mm*25mm*2,5mm pieces of that curved wall. I tried to forge the other piece, but it just went flat and got a bit thinner at the edges, no fractures found. The other piece was bent with two pliers, first straight and after that about same amount of curvature in the "negative" direction, until it snapped into two pieces. It was hard to believe that it could take so much violence before cracking. The cheap (grey?) cast iron cylinders tend to crack at thin places if you just look at them with a wrong eye.

Sadly the track season is over in Finland. Some few months ago we built this bucket style 77cc track moped. In the video it only has about 10rwhp, since the quite DIY-style suspension was just being adjusted. We managed to build 13,5rwhp technique with worn out clinder, but got to drive it just once...



https://www.youtube.com/watch?v=QBXu6W8BLoA

Now we are waiting that the ice on the lakes is thick enough..

[wobbly]

LA sleeve and several others make blank spun cast iron liners in a huge range of sizes.
This machines really well,and works perfectly.

[jbiplane]

Thanks for advices guys. I want to make experimental liners of metal powders by plasma coating 3d printing or whatelse.
This should result porous composite structure.

Once my friend cast very porous aluminum cylinders (and cover by nikasil) which leaks oil through everythere, but were very durable.

[JanBros]

I have this idea to use a blank liner in an oversized cast iron cylinder to get it back to 50cc, and at the same time use the liner to turn the single exhaust into a double. how thick do you recon the liner has to be for the bridge in the exhaust port to be "safe" ?
or should I first weld the exhaust port so the bridge has material behind it that gives support ?

[husaberg]

Thanks for advices guys. I want to make experimental liners of metal powders by plasma coating 3d printing or whatelse.
This should result porous composite structure.

Once my friend cast very porous aluminum cylinders (and cover by nikasil) which leaks oil through everythere, but were very durable.

John Tice here and here here shows how to make the paterns for cast sleves, i believe he used to supply them for a few manufacturers.

[SwePatrick]

Has it ever been tried to thermaly isolate the exhaust from the cilinder?
I suppose most heat transfered from exhaust gas is passed to the metal of the pipe by Radiating.

I used an other approach then Frits.
Just for testing, and dragracing, no need for long serviceintervals.

Let´s see if i can explain in text:

As my duct is quite worn for the pipefitting in cylinder, i bored it out 0.5 millimeter bigger.
This way i can fit an bit of a tirehose on the part that holds the o-rings on the pipe.

I also let the hose 'hang over' the end of the fitting so it made a thermal barrier 'axial' against the duct in cylinder.
As the hos is flexible it didn´t hang freeley, it 'shrunk' and made an axial seal, hard to explain.

Well,, like putting a condom on a....

As i run methanol i had no issues with burning the rubber.

Rgds.

[Haufen]

'hang over'
putting a condom on
no issues with burning the rubber.

Rgds.

just practicing my selective reading skills

What I was wanting to ask - did you notice a difference between the isolated and the non-isolated pipe on the dyno?

[Frits Overmars]

John Tice here and here here shows how to make the paterns for cast sleves.

Quote from that forum:

After the sleeve is in & aligned a weight is put on top to hold things in place. If you don’t weight the new liner it will raise like you squeeze your tooth paste tube.

Been there, done that and learned that it doesn't work.
When the cylinder is cooling down and the sleeve is picking up heat, they grab each other at some point and from then on, the cylinder top deck will creep further down along the liner, towards the point where the two first grabbed. You'd need a giant weight or better still, a press, to move the sleeve further down in order to keep its top collar in contact with the cylinder deck.

I'm avoiding sleeves, but if I still had to fit one, I'd slide it in the hot cylinder, line the windows up and then immediately put a damp cloth on top of the cylinder,
making sure that the deck cools faster than the rest of the cylinder. That way the sleeve is grabbed at the top first and the cylinder deck won't creep down on it.

I used an other approach then Frits. Just for testing, and dragracing, no need for long serviceintervals.
As my duct is quite worn for the pipefitting in cylinder, i bored it out 0.5 millimeter bigger. This way i can fit an bit of a tirehose on the part that holds the o-rings on the pipe. I also let the hose 'hang over' the end of the fitting so it made a thermal barrier 'axial' against the duct in cylinder. As the hose is flexible it didn´t hang freeley, it 'shrunk' and made an axial seal...

Using asbestos exhaust gaskets was not 'my' approach Patrick; it was common practice back in the day when we did not yet have an environment and asbestos was considered a cure for everything.
Having said that, your condom solution works fine. We used to use a similar approach on the old Yamaha TZ-cylinders (with butyl rubber muffs instead of an inner tube, because in roadracing it had to last a bit longer than in dragracing). Especially the axial buffering that you describe was favourable because it protected the heat-softened aluminium exhaust stubs against the hammering of the pipe flanges.

[SwePatrick]

just practicing my selective reading skills

What I was wanting to ask - did you notice a difference between the isolated and the non-isolated pipe on the dyno?

Sadly i never tested 1-2-1 testing with that.
But as i added more and more tricks my powerlevel climbed upwards the whole time.
This was worth about 1.2hp
It might be worth more with petrolengines, but i haven´t tested that.
But,,, it might be that hangover and burned rubber again when pushing it too hard