ESE's works engine tuner

[Storbeck]

Hi TZ,

That’s very interesting.
The theory is, when you get it right. With a head start, about 2deg . The gases from the outer edges arrive at the exhaust duct nozzle at the same time as the gases from the lower bridge area as they have a shorter path.

This is a little bit confusing to me since the exact same theory didn’t worked with triple exhaust port and ended with having auxiliary ports lower than main port !?

I was thinking the same thing.

[bad'rule]

Jamathi, Thank you for your idea , they have been proven to be reliable and,it even won in the race too.
Bonus on easier sleeve changing there.

I will give it a try on these one and with what Wobbly suggest for thickness.




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[Niels Abildgaard]

Some students and I visited a gokart engine manufacturer (Dino) in Middelfart ,Denmark many years ago
They used centrifugal cast iron for cylinder liners,modified on fridays, and many copies were sold on mondays if they had won on saturdays.
If the reason for aluminium and nikasil being prefered today is better heat transfer,then unplated bronze bearing metal could be cheaper for one offs.
Has it been tried and why not?

[wobbly]

The triple port geometry is optimized by creating the highest amplitude , shortest duration wave front into the duct , and this means the main port is out at maximum width around 70% of bore.
This is not only the optimum width for ring life but also creates the least path length difference whilst giving the maximum Blowdown area at EPO.
Once this initial wave is established into the duct , heading for the diffuser , the Aux ports , being lower and having considerably less pressure delta across them
subsequently play more of a part in simple Blowdown pressure bleed, rather than creating another high intensity wave with a much longer path length.

In a T port you are stuck with the large path length difference , no matter what the geometry ,so you have a choice of the outer , longer path timing being below , equal to ,or above.
All are a serious compromise , but one ameliorates the shapes down side better than the other two.
In a 3 port the geometry happens to be the least compromised with the outer edges being lower.

[Grumph]

Some students and I visited a gokart engine manufacturer (Dino) in Middelfart ,Denmark many years ago
They used centrifugal cast iron for cylinder liners,modified on fridays, and many copies were sold on mondays if they had won on saturdays.
If the reason for aluminium and nikasil being prefered today is better heat transfer,then unplated bronze bearing metal could be cheaper for one offs.
Has it been tried and why not?

It's one of those awkward trade-offs. Phosphor bronze would probably be too soft to run steel rings against. The harder Bronzes - like Admiralty Bronze
can be quite brittle.
Cost wise,there's probably not a great difference between plated alloy and bronze. The price of Copper currently makes bronze quite expensive.
Plus you'd have to buy it as hollow bar - which is very thick wall so you'd have a lot of wastage.

[speedpro]

Or Ken Steadman at PHOENIX FOUNDRY LIMITED could probably cast sleeves to a size you want. He could also customize the alloy which I know he's done on at least one job.

[dutchpower]

Mahle 138 should be AlSi18CuMgNi 😉

Mahle 138

G - ALSi18CuNi

[husaberg]

Some students and I visited a gokart engine manufacturer (Dino) in Middelfart ,Denmark many years ago
They used centrifugal cast iron for cylinder liners,modified on fridays, and many copies were sold on mondays if they had won on saturdays.
If the reason for aluminium and nikasil being prefered today is better heat transfer,then unplated bronze bearing metal could be cheaper for one offs.
Has it been tried and why not?

Aluminium pistons and aluminium bores popularity I believe is more than just heat transfer but also as their expansion rates are closely matched which as well as matching heat transfer helps stop the transfer of aluminium onto the iron cylinder

[Frits Overmars]

Aluminium pistons and aluminium bores popularity I believe is more than just heat transfer but also as their expansion rates are closely matched which as well as matching heat transfer helps stop the transfer of aluminium onto the iron cylinder

Just how closely do you want the expansion rates of piston material and cylinder material to match? The ideal would be 1 to 1 if piston temperature and cylinder temperature were equal.
But they're not. The piston gets a lot hotter than the cylinder, so its expansion rate should be lower, like a steel piston in an aluminium cylinder.
It does work on foulstrokes. The problem is that the dome surface temperature of the steel piston would be sky-high, and two-strokes do not like that.
Foulstroke manufacturers get away with it by cooling the piston from below with multiple oil jets. In crankcase-scavenged two-strokes we cannot have that luxury.

[lohring]

Very small racing engines have used chromed brass sleeves with ringless high silicon aluminum pistons. This seems to work for up to around 15 cc engines, but ringed pistons work better with the same materials in larger sizes. Quite a few 2 to 10 cc engines were made with cast iron ringless pistons in cast iron sleeves. Really small engines have been built with hardened steel pistons in steel sleeves. Careful machining is needed to make these combinations work.

Lohring Miller

[Frits Overmars]

We use alloys with a silicon content of over 30% for pistons: https://www.rsp-technology.com/
The silicon keeps the expansion coefficient under control. The downside is that alloys containing so much silicon will eat milling cutters for breakfast.
https://www.youtube.com/watch?v=ZwbEuzJCnqI

[katinas]

.....then unplated bronze bearing metal could be cheaper for one offs.
Has it been tried and why not?

I tried a liner made out of aluminum bronze (with 6% of iron and nickel) without coating, it works fine without any siezing, but it wore out quickly. Ater that bought RG7 bronze, but never tested.

[Muciek]

Here guy have cast a cylinder from aluminium like used in Porsche/Audi/BMW/mercedes engine blocks (ALUSIL) and honed it with special paste afterwards, wait week or two so he will probably get it running.

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

Whole road to getting a good casting https://www.youtube.com/watch?v=sX7W...BJRRCuP1DnEGov

[pete376403]

Here guy have cast a cylinder from aluminium like used in Porsche/Audi/BMW/mercedes engine blocks (ALUSIL) and honed it with special paste afterwards, wait week or two so he will probably get it running.

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


Whole road to getting a good casting https://www.youtube.com/watch?v=sX7W...BJRRCuP1DnEGov

Sound the same as Chevrolet did with the Corvair blocks - cast in high silicon aluminium, then the bores were etched with acid(?) to erode the ally and leave the siiicon as a wear suface for the rings

[Frits Overmars]

Sound the same as Chevrolet did with the Corvair blocks - cast in high silicon aluminium, then the bores were etched with acid(?) to erode the ally and leave the siiicon as a wear suface for the rings

Yup. And some Porsches. And some Mercs. And probably others.