ESE's works engine tuner

[Vannik]

Is he deliberately running a very lean mixture? That would not make the piston of a turbocharged engine very happy. Have you got information beyond the paper, Neels?

No extra info, sorry.

[andreas]

Fuel need not be a problem; one can inject as much fuel in the exhaust system as one likes. But what about oxygen?
In his paper ( https://www.kiwibiker.co.nz/forums/s...post1131186140 ) Lennarth Zander only states that the exhaust gases contain air; there is no explanation how this air could pass through the combustion engine without all of its oxygen being consumed.
Is he deliberately running a very lean mixture? That would not make the piston of a turbocharged engine very happy. Have you got information beyond the paper, Neels?

"The afterburnerassistedturbocharger system makes it possibleto ”over scavenge” the engineto lowerthe exhaustport temperaturewhilethe pre turbinetemperaturecanbe maintainedat a decent800 degCtemperature. Not bad for an engineputting outaround50 [kW]."

Frits, maybe this is what he means. Copy paste didnt work so well, but it's to be found further down in the text.

[SwePatrick]

It pops and bangs a little before it´s cleaned up, then it pops and bangs when it hits the revlimiter.(13000rpm)
I sat down in seat and had only about 12psi in rear tire to get some traction on 4th gear(i actually tested a thing)
The smoke laid thick in the house for a couple of hours, but burnt rubber is a good smell



I tested new carb jetting as i had a HUGE hole in fuel delivery just before it hit the pipes, now it seems good.
Special grinded the metering rods and changed the emulsionpipes.

[Norman]

"The afterburnerassistedturbocharger system makes it possibleto ”over scavenge” the engineto lowerthe exhaustport temperaturewhilethe pre turbinetemperaturecanbe maintainedat a decent800 degCtemperature. Not bad for an engineputting outaround50 [kW]."

Frits, maybe this is what he means. Copy paste didnt work so well, but it's to be found further down in the text.

I think that he in this particular set up is using an afterburner and "port injection" (not TPI) or carburator (in actual test). Then he states that an oxidation catlyst can be used to increase exhaust temperature before turbine if the exhaust/short circuit is lean/air. I am thinking that if a DI system is used, the short cut will be mostly air.
On the set up picture from the Charlmers presentation it looks as if they are using one intercooler and then a water cooled charge air section. I can imagine it is important to keep the inlet temp down. The quite large compressor to carburetor intake tract on the test set up must also affect pressure build up. Should be quite easy to optimize by using one charge air cooler (small) and a low temperature radiator circuit with a dedicated pump (of course all about where the engine is to be used)
Interesting concept and of course still room for much optimization.

[Frits Overmars]

"The afterburnerassistedturbocharger system makes it possibleto ”over scavenge” the engineto lowerthe exhaustport temperaturewhilethe pre turbinetemperaturecanbe maintainedat a decent800 degCtemperature. Not bad for an engineputting outaround50 [kW]."
Frits, maybe this is what he means. Copy paste didnt work so well, but it's to be found further down in the text.

If I understand you correctly, the engine runs on a normal air-fuel mixture (Lambda somewhere between 0,8 and 0,9) and the air that makes it to the afterburner was blown straight through the engine before exhaust port closure. That sounds plausible and simple .

It reminds me of a proposal by Keith Duckworth (or was it Colin Chapman?) back in the day when two-strokes were not yet forbidden in Formula 1. He envisaged a two-stroke engine with an extremely high exhaust timing, feeding a turbocharger that was geared to the crankshaft. Whether the crankshaft was going to drive the turbo or the other way around did not matter; what mattered was the power generated by this compound layout. I don't know why Duckworth did not take the idea further. Maybe it was the specific fuel consumption that put him off, or maybe he got the rulebook thrown at him.

[Muhr]

I guess it's not a regular catalyst we'm talking about? To me, a catalyst is just a lump of stainless steel with honeycomb structure dipped in palladium or something similar. Wondering if he is thinking of something similar below.
https://patentimages.storage.googlea.../US3220179.pdf
https://www.researchgate.net/publica...ication_detail

[andreas]

If I understand you correctly, the engine runs on a normal air-fuel mixture (Lambda somewhere between 0,8 and 0,9) and the air that makes it to the afterburner was blown straight through the engine before exhaust port closure. That sounds plausible and simple .

It reminds me of a proposal by Keith Duckworth (or was it Colin Chapman?) back in the day when two-strokes were not yet forbidden in Formula 1. He envisaged a two-stroke engine with an extremely high exhaust timing, feeding a turbocharger that was geared to the crankshaft. Whether the crankshaft was going to drive the turbo or the other way around did not matter; what mattered was the power generated by this compound layout. I don't know why Duckworth did not take the idea further. Maybe it was the specific fuel consumption that put him off, or maybe he got the rulebook thrown at him.

Colin Chapman it seems. Was it a uniflow? I found random discussion here: https://www.f1technical.net/forum/vi...10966&start=15

[SwePatrick]

I guess it's not a regular catalyst we'm talking about? To me, a catalyst is just a lump of stainless steel with honeycomb structure dipped in palladium or something similar. Wondering if he is thinking of something similar below.
https://patentimages.storage.googlea.../US3220179.pdf
https://www.researchgate.net/publica...ication_detail

As i understand, it is just regular ones, but small cores.

[Vannik]

A "normal" catalytic converter as on gasoline fueled passenger cars are "three way" catalytic converters requiring stochiometric AFR.

The oxidation catalytic converter is a different type that operates in an excess level of oxygen, typically found on diesel engines.

[41juergen]

A "normal" catalytic converter as on gasoline fueled passenger cars are "three way" catalytic converters requiring stochiometric AFR.

The oxidation catalytic converter is a different type that operates in an excess level of oxygen, typically found on diesel engines.

And the trick is how to use the washcoat to get the fine precious metal particles distributed and "in place" during the catalysts life time...

[Flettner]

A prick of a thing to start.
Technique, exhaust port just open, then boot it, Left boot.
Two from two today, two attempts, two successes. E85, smells nice.
No turbochargers here.

[Muhr]

As i understand, it is just regular ones, but small cores.

So the question is what is your stinger temp...
https://liu.diva-portal.org/smash/ge...FULLTEXT01.pdf

[Muhr]

A "normal" catalytic converter as on gasoline fueled passenger cars are "three way" catalytic converters requiring stochiometric AFR.

The oxidation catalytic converter is a different type that operates in an excess level of oxygen, typically found on diesel engines.

Could it not be that he is referring to something like this: https://emis.vito.be/en/bat/tools-ov...ytic-oxidation
He also chooses to use the term EBK which in Swedish is the abbreviation for after burn chamber

[SwePatrick]

So the question is what is your stinger temp...
https://liu.diva-portal.org/smash/ge...FULLTEXT01.pdf

High enough

Video below prooves that often people overthink things, it´s a normal cat with a small 3hp engine running way rich (colder exhausts) and it lights up quite easily when rich.
And,, people running lean to light them up......



Some info:
https://www.open.edu/openlearn/scien...-section-1.5.2

[sniemisto]

I’d like to share my dyno result (Derbi D50B0) with new head insert even though it’s not pure back to back test as 1. old head had leak and 2. I changed squish from 0,5 to 0,4mm.

Peak was moved 400 rpm lower and some over rev power was lost. Dashed line is new one:



More than half of over rev power was gained back and little for peak with ignition adjustment. 1 degree more advance on peak power and 1 degree later timing for over rev. Dashed line is with new advance curve:


I made also some testing with different reeds. Test was done with 10mm spacer between block and crankcase and with no changes to ignition or jetting. I had been running with CR85 reed block and boyesen fiberglass 0,49mm petals. Malossi VL18 0,32mm carbon fiber (dashed line) was only better at over rev and worse in before.
Original Honda 0,41mm petals (dotted line) had also better over rev compared to boyesen with slightly reduced top:


Honda petals looks bit different than normal fiberglass, they look like fiber reinforced plastic.