2 stroke thread (with occasional F1 relevance!)

[vorticism]

In the previous photo you posted you can see that there's both an atmospheric and a compressor charge entry into the intake plenum. I'm not sure why. Reed valve?

Improves off-boost throttle response - more direct route for air without having to pass through the compressor. Once boost builds, that air path is closed.

More puzzling is that the system is without an intercooler. I guess the reason why is the difficulty with preventing radiators/heat exchangers clogging with snow and a purely liquid system would add too much weight. I suppose the low ambient temps (and relatively low boost) it will operate in help but still strange to see a turbo set-up without intercooling to regain air density.

There have been some low boost supercharged engines in the production motorcycle and automotive world, so not unprecedented. If snow clogging were an issue I'd challenge the engineers to design a snow melt assisted cooling system.

[Pinger]

Snow melt is how the main cooling is done. Maybe not enough space in the tunnel for another cooler or maybe it would add too much weight for something designed to climb mountains - law of decreasing returns and all that.

[gruntguru]

what I think that I think is that I think that .....
it would (ie could) work in series
tuned length effects of expansion chamber are boosted ie proportionate to mean exhaust pressure ahead of turbine ?

To work in series the pulses would have to be able to travel through the turbine housing in both directions - which may or may not be possible.
The first positive pulse would have to pass through cleanly but as the turbine housing likely presents a change in cross-sectional area, the pulse will react to that and reflect back towards the cylinder - polarity unknown.

Despite my asking, no one has ever been able to answer the question of pulse behaviour entering a turbo - not even turbo specialists.

Pulses experience significant attenuation as they pass through the turbine. What pulsation remains is of no use for wave tuning.

[J.A.W.]

Hybrid at Jerez tests
https://images-wixmp-ed30a86b8c4ca88777 ... 0-aIcZ6634

A two-stroke - is it - Johnny? Do elucidate, by all means...

[J.A.W.]

what I think that I think is that I think that .....
it would (ie could) work in series
tuned length effects of expansion chamber are boosted ie proportionate to mean exhaust pressure ahead of turbine ?

To work in series the pulses would have to be able to travel through the turbine housing in both directions - which may or may not be possible.
The first positive pulse would have to pass through cleanly but as the turbine housing likely presents a change in cross-sectional area, the pulse will react to that and reflect back towards the cylinder - polarity unknown.

Despite my asking, no one has ever been able to answer the question of pulse behaviour entering a turbo - not even turbo specialists.

Pulses experience significant attenuation as they pass through the turbine. What pulsation remains is of no use for wave tuning.

For sure, it seems some here are conflating the 'sonic pulse/shaped-charge' effects in the anti-venturi
shaped expansion chamber, with basic exhaust-gas efflux venting.

The Rotax/BRP/Ski-doo turbo uses both, likely with the E-chamber tuning 'topped-up' by the turbo.

[johnny comelately]

Hybrid at Jerez tests
https://images-wixmp-ed30a86b8c4ca88777 ... 0-aIcZ6634

A two-stroke - is it - Johnny? Do elucidate, by all means...

No, it is the latest pipe for the MotoGP KTM works team at testing post race at Jerez

[J.A.W.]

They look like the 'sausage' mufflers - that old Pommy bikes featured ~60 years ago!

[johnny comelately]

They look like the 'sausage' mufflers - that old Pommy bikes featured ~60 years ago!

I knew you were going to say that LOL
The hot dogs
but sadly no, we are in 2022

[J.A.W.]

To be fair, at least Yamaha has decided to keep the Hinomaru flying for the Nippon 2-stroke MX 125,
against the Euro-hordes of KTM et al, with a thorough revamp of their cute but capable YZ 125:

https://dirtbikemagazine.com/2022-yamah ... full-test/

[johnny comelately]

To be fair, at least Yamaha has decided to keep the Hinomaru flying for the Nippon 2-stroke MX 125,
against the Euro-hordes of KTM et al, with a thorough revamp of their cute but capable YZ 125:

https://dirtbikemagazine.com/2022-yamah ... full-test/

and the 250/300's
courtesy of the horrendous maintenance costs of the contemporary 4 stroke MX'ers

[johnny comelately]

They look like the 'sausage' mufflers - that old Pommy bikes featured ~60 years ago!

What is a situation where you would have a 2 stroke tailpipe not quite that big but close?

[J.A.W.]

They look like the 'sausage' mufflers - that old Pommy bikes featured ~60 years ago!

What is a situation where you would have a 2 stroke tailpipe not quite that big but close?

The position of the tail-pipe is not that important in fact, other than for convenience/emissions
but length/diameter is, due to the heat effects, which alter resonance factors
(as does water injection added into the chamber).

[johnny comelately]

They look like the 'sausage' mufflers - that old Pommy bikes featured ~60 years ago!

What is a situation where you would have a 2 stroke tailpipe not quite that big but close?

The position of the tail-pipe is not that important in fact, other than for convenience/emissions
but length/diameter is, due to the heat effects, which alter resonance factors
(as does water injection added into the chamber).

It is the diameter I'm primarily meaning.
The situation is when using methanol or nitro infusions because the heat build up melts pistons

[J.A.W.]

Click on the link below to see the 'Superbike Homologation' performance pipes offered by Denco
for the largest capacity 2-stroke motorcycle sold in dealer showrooms, way back in the mid 70s.

http://suprememotos.com/uploads/postfot ... enco-5.JPG

[J.A.W.]

What is a situation where you would have a 2 stroke tailpipe not quite that big but close?

The position of the tail-pipe is not that important in fact, other than for convenience/emissions
but length/diameter is, due to the heat effects, which alter resonance factors
(as does water injection added into the chamber).

It is the diameter I'm primarily meaning.
The situation is when using methanol or nitro infusions because the heat build up melts pistons

Alcohol fuels run cool, as such usage of methanol as a race fuel allows 'classic' air-cooled bikes to
run sans the power-robbing heat-soak they suffered from by racing on petrol, back then.

EGT head-pipe probes are nowadays an essential part of establishing effective race tune parametrics
- even on the old stuff - such as in the link just above.