All the F1 engines are now greater than 50% TE and at best are probably more more efficient than the Wartsila. Mercedes were claiming 50%+ seven or eight years ago and all the engines have improved significantly since then. Pat Symonds lecture doesn't give a number for TE but includes a lot of fascinating insights.
Link

je suis charlie

Large stationaries are advertising upper 40s while meeting emissions, but operating points well over 60% are achievable. Anything that has to pull the entire lug curve will always be lousy for efficiency compared to modern high-speed stationaries optimized for an operating point, 2-stroke low-speed beasts notwithstanding.

Large stationaries are the low speed and very large medium speed engines. On they're own they're only approaching 50%. The slow speed can get above 50% in shipboard applications where the have lots of cogeneration loads. High speed engines mostly have not made it to 40% yet.

Note that I am working off antiquated but accepted definitions. Low speed < 250rpm < medium speed < 900rpm < high speed.

Pretty sure the best Wartsila has circa 52% TE - shaft power only.

je suis charlie

The various Scandinavian Hot Bulb engines ran in the most effective way, and in reality what is most efficient is what is most effective. That being said Volkswagen drove a hybrid Golf prototype across the USA and claimed 500mpg, somehow they built a steam boiler into the exhaust system, and injected SC steam into the combustion chamber. Definitely a one-off.

Can’t find the link to VW Golf, did anyone else see this news story? —-think it was ~2015. Apparently this is an over unity result . . . series hybrid hydraulics vehicle might achieve over %50 equivalent TE, with gas engines, IDK.

It might be hard to find because your MPG is so far off.

https://www.motortrend.com/news/a-volkswagen-golf-...

The year was right.

Also, that was a production vehicle (and one whose technology was later to be implicated in the "dieselgate" scandal). That sort of low fuel consumption isn't due to any revolutionary technology, more due to simply driving slowly and steadily so as to be as efficient as possible.

There was no "steam boiler" in the exhaust system of that vehicle (I believe it was BMW who did that experiment). Although it wasn't specified, the car would have used either the 6-speed manual or 6-speed dual-clutch automatic, in both cases having fully mechanical transmission to the wheels. No "series hybrid hydraulics" ... that's less efficient than electric+battery, and if you're doing steady speeds, that's less efficient than gears and shafts.

Wikipedia has an article about the Turbosteamer with links to further information. https://en.wikipedia.org/wiki/Turbosteamer

Does not appear to be worth the aggravation.

Thanks for the responses. Turbosteamers and hybrids, oh dear. In terms of maximum preservation of thermal angst, Top Fuel dragsters must be the winner each and every time, those phonons are all cleanly morphed into earth shaking euphoria. Perfect unity mach8ne!

The valve springs of a top fuel engine are the most fascinating part to me. It seems like it should be the lowest stressed part for such a few cycles of fatigue yet they get some of the most attention including polishing of the wire. I don't think even NASCAR does that. There must be a reason but it's super secret.

Is it easier to finish Ti alloy?— must admit that these springs exist is news to me. With no traditional coolant system and valves never closing, all the heat goes into the guide and springs, so maybe Ti is getting near critical temps?
For giggles I calculated TE of a top fuel dragster at 0.007929%, beat that!

What - you didn't add the shredding of rubber and clutch discs into your useful energy output?

je suis charlie

https://www.youtube.com/watch?v=mUq-K9jcaB8

Brian,

Here’s the very poor wikipedia link to this unusual combustion: ddt
https://en.wikipedia.org/wiki/Deflagration_to_deto...
18:1 mechanical CR, boost up to 5.5 bar, lambda over 1.3 and fuel with no aromatics.
I’m assuming the Detonation is preferably at peak RPM when piston speed is greatest, and special cooling squirter to prevent meltdown of pistons, although how they still don’t melt? Diamonds?
IDK.
—To draw from the earlier Achates Thread:—-Is this suited to opposed pistons, as Tug mentioned, there’s a 2x expansion, so better suited to a faster combustion? The above video makes me think that the Achates OP is a detonation diesel, based on the timeframe, I know that a number have been said to exist. Could this be one? Any opinions?

The video above is surely just the tip of the iceberg, the small part of development that they feel they don't need to keep secret.

Ever-so-slightly-educated guesswork follows. (Purely mine.)
They're running on the verge of detonation, but still keeping rate of combustion finite so that it is a progressive almost-self-ignition and not a simultaneous ignition everywhere in the combustion chamber.
They're not relying on in-cylinder charge motion as much as conventional production engines do - they're getting the speed of combustion via the plasma-jet ignition and the almost-but-not-quite detonation. The flat-pancake shape of a F1 cylinder (due to the extreme bore/stroke ratio) doesn't lend itself to tumble charge motion that is typical of production 4-valve-per-cylinder engines.
Completing combustion very quickly, in a small number of crank degrees and while the compression is high, cuts down on the time available for heat transfer to the pistons.
The big bumpy cams necessary for high-RPM peak power leads to lower dynamic compression ratio at lower revs, so detonation at lower revs probably isn't as much of a problem - the effective compression ratio will be lower because the volumetric efficiency is lower. These engines will not have friendly, smooth, daily-driver-suitable torque curves.
Running high lambda keeps peak combustion temperature down.
They're probably doing some in-cylinder stratified-charge trickery to keep the mixture next to the piston as high lambda (lean) as possible to act as an insulating layer.
High lambda (high dilution) plus completing combustion very quickly so that the burned charge is more fully expanded, cuts down on exhaust-gas temperature.
Cutting down on heat transfer to the pistons (and head) is an important bit of improving engine efficiency.

A nuisance with Achates is that you can't put the injector and spark plug in the center of the chamber, because there's a piston there instead of a cylinder head. Not saying it can't be done, but it would need a re-think of the combustion process.

BP. Good insights, and thanks for the ‘guesswork’.

—-One tiny morsel from this presentation, is that MGU machine can directly power the crankshaft, if the batteries are at capacity. The fuzzy diagrams show a ‘blackbox’ so guessing what this means, or that I interpreted it correctly. But sounded like indirect coupling of turbo to crank,
—-Regarding the lambdas: 1.3 varying up to 1.5, and potential for 2.0. I have no knowledge of combustion properties at these temps and pressures, or these fuels. 1.3 is uncommonly lean.

Yes, they're recovering some output power from the exhaust turbine under some conditions.

Lambda 1.3 or thereabouts is probably the average for the whole chamber. If they're doing what I suspect - using direct-injection to deliver a shot of fuel through the last half-or-thereabouts of the intake stroke and first part of the compression stroke - my suspicion is that via clever injection timing and nozzle aiming, the top (let's say) half of the cylinder will be as close to lambda 1.0 as they can get (a bit of this is what works its way into the "prechamber" and the rest of it is next to the cylinder head) and the bottom (let's say) half of the cylinder will be way, way lean. Inevitably there will be mixing but this way the top part of the charge (starting at the spark plug / prechamber) can burn quickly and work its way down through the more dilute charge closer to the piston, with the last bit of boundary layer next to the piston acting as insulation for at least the first part of the combustion process.

Spark plugs don't like igniting mixtures leaner than roughly lambda 1.2 under normal conditions, and in a conventional engine, power loss starts getting out-of-proportion due to slow and incomplete combustion short of that. But, heating that mixture close to its self-ignition temperature via higher compression helps combustion along.

- Detonation melts pistons not because the gas temp is higher but because thermal protection provided by the boundary layer is scoured by shock waves. So yes they are not running in detonation.
- They are almost certainly achieving a form of HCCI (or SAHCCI) at some operating points and in some portion of the chamber.
- Bore is 80mm and stroke is 53mm. Not as oversquare as earlier F1 engines.
- Inlet cam is very short duration to produce EIVC Miller cycle. This will not reduce dynamic compression at low rpm as much as LIVC.
- The spark plug sits in the pre-chamber environment which will be at lambda 1.0 or richer.

je suis charlie

Yes, and the pre-chamber environment is lambda 1.0-ish because the vicinity of the combustion chamber outside the pre-chamber is lambda 1.0-ish, at least for the part of the compression stroke up to the point of ignition (which is only a few degrees before TDC). There's no dedicated injector for the pre-chamber because the rules only allow one injector per cylinder - so they have to be doing it via stratified charge through injection timing and nozzle-aiming trickery.

If the rule makers were using the unlimited budget of F1 to develop new engine technology for the rest of us the single injector rule was a smart trick to make the technology more applicable to on the road use. Directing charge into pre-chambers is nothing new.



On the subject of detonation, I have heard NASCAR and motorcycle engine manufacturers utilizing their high piston speeds to outrun the shockwave from detonation. It was some years ago that I heard this and can't provide any sources.

Peak piston speed ~40 m/s
Speed of sound (detonation front) ~1000 m/s

je suis charlie

B.P.
Yes, duration and timing of (a late) injection pulse would be critical to get Lambda 1 in the pre-chamber.

je suis charlie

The piston may need only establish some distance. The key may not be to outrun the shockwave all together but to meet it at a lower energy level. Where was that Yamaha link again? They were pioneers on this type of stuff.

Here is spark ignition side by side with an hcci, c.2007
https://www.youtube.com/watch?v=oNCBbcINHuk

Here is readable summary of these technologies:
https://www.ni.com/en-us/innovations/white-papers/...

Have thought hcci to be a detonation combustion, although have never seen it called this, I am looking for arguments that it’s not.

High efficiency dilute gasoline engine at Southwest research institute:

HEDGE is . . .”dedicated to the development of pre-competitive technologies that will be needed to cost-effectively achieve future emissions and fuel consumption requirements for world markets.”

Is pre-competition before or after F1?

I think "pre-competitive" means research-stage, before individual companies start doing their own variations and calibrations on it (i.e. in competition with each other and with other technologies).

HCCI has been at a research stage for so long, and without resolution of some fundamental difficulties, that I have my doubts that it will ever get any closer to production than Mazda's Skyactiv-X system, which is spark-assisted and uses stratified charge to achieve fast but smooth (non-detonation) combustion.

Lean combustion is a non-starter for production applications for NOx reasons. It is not possible to get the NOx low enough merely via lean-burn to comply with current and foreseeable emission standards without aftertreatment, and NOx aftertreatment for lean-combustion applications involves SCR and AdBlue / DEF the same as diesels are using, and nobody wants that aggravation and expense.

HCCI is combustion propagated by flame front(s) at multiple locations simultaneously.

Detonation is combustion propagated at much higher speed - usually sonic velocity via a shock wave.

je suis charlie

http://www.epi-eng.com/piston_engine_technology/de...

“Engines don’t ‘detonate’ ! 'Detonation' requires either a phase change as part of the exothermic event or a diverging nozzle. Auto-ignition ahead of the flame front in SI (spark-ignition) engines is sonic, not supersonic. Therefore "detonation" is not the proper term. Either "auto-ignition" or "knock" are correct descriptors, knock referring to the audible sound emitted from sound waves traversing the combustion chamber at less than sonic velocity."

—This above is a rewrite of the Allen Cline article on knock, that many are perhaps familiar with. The only adjustment is switching terms from ‘detonation’ to ‘auto-ignition’.
also, S.Onishi, c.1979, atac paper, refers to hcci as ‘abnormal combustion’

—Plasma assist comb., PAC, from the F1 vid., might be microwave assisted? Here are some images:
https://cefrc.princeton.edu/sites/g/files/toruqf10...

—-hedge engines, dilution is of oxygen radicals via egr. (Not of the fuel air ratios)

This has pictures of ceramic coated pistons: https://www.wireilla.com/engg/ijmech/papers/5216ij...

There are some number of articles available that discuss various sintered ceramic coatings for hcci thermal control, and some others reporting material toughness young’s modulis and also ablation resistance of various compositions, But can’t find anything on how practical ‘thermal-barrier-coatings’ are for daily drivers, and what happens when it chunks off —it probably doesn’t. Either way, if spark plug is shrouded in a pre-chamber with injector, combustion chamber mechanical damage could be manageable with sustained knock.

GM used ceramic barrier coatings on the pistons of their turbocharged 6.5L diesel engines made from 1993-2000. Most manufacturers seem to be diverging from that practice and adopting steel pistons. Everybody seems to have gone to Mahle Monotherm pistons.

Bear in mind that the Formula 1 situation is extremely optimised for full-load operation high in the RPM range, and its operation is extremely contingent upon fuel chemistry. Those engines are not designed for efficient part-load operation (typical of daily-drivers), or smooth idling with impeccable low-speed driveability, or compliance with Euro 6 or US EPA Tier III emission standards, or cold-starting in -30 C, or driving 10,000+ km between engine oil changes, etc.

Mazda's spark-assisted HCCI system is likely as close as such a system will get for a daily-driver application ... and it doesn't operate in SA-HCCI mode all the time ... and it doesn't appear to give a fantastic improvement in consumption over the regular Skyactiv-G engine, which is already pretty good ... but not earthshatteringly better than the consumption of a reasonably optimised normal port-injection variable-valve-timing four-banger. Friend of mind has a VW Golf with the 1.8 TSI four-banger, and it does pretty well in daily driving. Direct-injection, turbocharged-intercooled, VVT.

Auto engineers know about ceramic coatings. If the benefit exceeded the cost, they'd be in production - and there have been some. If they're not used in a particular application (most), at this point in time, it isn't because nobody thought of it before ... it's because someone looked at it and established that the benefit (if any) wasn't worth the cost. Keep in mind that a ceramic "thermal barrier" coating, or manufacturing parts from heat-resistant ceramics (been done), doesn't stop all heat transfer to and from the surface. If it slows heat transfer through the surface, thus leading to the surface temperature being higher, thus leading to the temperature of the charge being higher at the end of the compression stroke, thus increasing self-ignition (detonation) propensity, thus forcing the compression ratio to be dropped and/or ignition timing to be retarded ... was it worthwhile?

Cylinder heads are made of aluminium nowadays. Aluminium conducts heat quickly. Maybe that's by design ... to cut down on hot-spots that lead to pre-ignition or self-ignition (detonation). The aforementioned Formula 1 engines, the Golf 1.8 TSI engine, the Mazda Skyactiv-G or -X engines, all use aluminium cylinder heads. Changing to a less thermally conductive material, like cast iron ... isn't something that is a foreign concept to engine designers. They use aluminium because the benefits outweigh the costs.

This ain't simple ... and the engineers ain't stupid.

Here is the GM 6.5 example. An interesting detail, the piston is not part of the combustion chamber. This engine has pre-chambers.

Diesel engines aren't subject to the detonation and pre-ignition constraints, so if there's an application for thermal barrier coatings or less thermally conductive materials (e.g. steel pistons), it's there. And they don't rev high, so if the piston is a bit heavier because it's made of steel, no big deal in that application.

Diesel engines with prechambers have gone the way of the dodo. Direct-injection engines are more efficient due to lower heat losses in the chamber. The old GM indirect-injection (prechamber) 6.5 was replaced with the direct-injection Duramax.

The prechambers in the F1 application are really small, a few percent of the total chamber volume, so the thermal losses aren't meaningful in the big picture ... benefit outweighs the cost.

I wouldn't say the pre-chamber has gone the way of the dodo. We were just taking about F1 using a pre-chamber. Also, many industrial diesel engines have spark ignition gas options now which use pre-chamber. The PC is dead for diesel but it's becoming relevant for every other fuel.

Pre-chamber diesel engines do have a big advantage, they have a wider power range do they run more like a gas engine. I recently blew the 6.2 diesel in my truck which is why I'm building that 6.5. I already committed to making room for a center mount turbo so I could easily fit a Duramax but the direct inject diesel engines don't have the RPM range to make a 3 speed automatic with 4.56 gears drivable. I would have had to make many more changes to accomodate the narrow DI powerband.

not really on topic of thread title but on topic of GM 6.2/6.5 and automatic transmissions ...

Years back a roadracing buddy bought a used GM G-van cheap because it was a non-runner with a blown-up 6.2 non turbo. At the time of buying it, it had a (I think) THM350 installed in the vehicle, and I believe it came with a blown-up 700R4 loose in the back.

From what he could tell, the trans blew up first, and rather than repairing and upgrading the 700R4, the previous owner dropped in the 3-speed non-overdrive. What the previous owner didn't do, was figure out what to do with the THM350 vacuum modulator on this diesel engine, so they left it unconnected. This, of course, told the transmission to operate as if the engine were full throttle all the time, upshifts at whatever max upshift speed the valve body was calibrated for. That blew up the engine. At that point the previous owner determined that they were in over their head, and Jack bought the blown-up remnants.

He had the 6.2 and the 700R4 rebuilt with upgrades to beef up the transmission, and drove it for years afterward; we split a ride to Road America in that van.

Those were the days. Another racing buddy had a Ram van with a 225 slant six and single-barrel carb. Yet another had a Ford cube van with a 7.3 non-turbo; quite a rocketship (not). Yet another had a Ford cube van with a 460, which decided to quit running on the way back from Mid-Ohio due to a broken wire inside the distributor ... on the Ambassador bridge in Windsor in the queue for passport control. "Oh, this again. I know what's wrong." Nothing like attracting the attention of border patrol by opening a toolbox and working on your vehicle in the forecourt of passport control ...

Your story rings true. There is a vacuum pump and modulator to simulate a carburetor on my truck as well. I have the TH400 transmission. I had a hard time finding a modulator so I had to drive for quite some time with full throttle shifts only. Part throttle shifts were hard and nearly smack your head on the back window. I trained myself to floor it at the shift points to prevent that.

It's on topic though. My 1.25 ton truck with the 6.2 diesel, no overdrive, and 4.56 gears with 31 inch tires managed 18 mpg. It didn't really manage 65 mph but now with the 37 inch tires that won't be a problem. The fire ring on the head gasket fretted through the block and killed it. The 6.5 I bought to replace it bad the same problem which is why the top deck is so clean in the pick I posted.

The 6.5 has a turbo but also has different pre-chambers. I have no idea what the milage will be. Maybe I'll report back when it's done.

Recently was looking at a non-compliance 6.5 in CA, original owner gifted this gmc3500 rather than attempting to sell out of state. Needed plugs and radiator cap, and looked like it never had any maintenance in 20 years, but loads of truck for the money. It’s probably in Mexico now.

Back to this detonation versus ‘knock, auto-ignition’ and hcci: have found a parsing of detonation into slow and fast, from the textbook ‘Combustion’, by Glassman & Yetter, which states: “ . . . it’s a common error to confuse explosion and detonation.” Which is self-ignition by thermal initiation, versus a shockwave propagation. Detonation is not correct term, but knock is, for HCCI.

Here is a 20pg oil industry paper which doesn’t beat about the hedge;)
https://www.npc.org/FTF_Topic_papers/6-Low_Tempera...
“LTC is in essence controlled knock” (page 18)
“ alphabet soup of acronyms . . . HCCI, PCI, PPCI, CAI, RCCI, etc. <used> to describe the different approaches <to> low temperature combustion (ltc) <which> signify the different ways researchers are choosing to establish and control the basic requirements for this “flameless” combustion. (not laminar deflagration)” (page 12)

Quote (Factoter)

Therefore "detonation" is not the proper term.

We're in the weeds here but.. yes it is. Detonation in an engine is dangerous to the engine because of the damage which can be done by the shock wave. The presence of that shock wave is what defines 'detonation'.

Quote (Factoter)

Detonation is not correct term, but knock is, for HCCI.

Stop it. 'Knock' is a colloquial term - coined because an engine that's undergoing detonation makes a noise that sounds like something is knocking on something else with a hammer. 'Knock' is not an engineering term.

When you hear an engine 'knocking' there absolutely is a supersonic shock front inside the cylinder which is slamming into the cylinder wall, piston, head, whatever and probably damaging them.

Do diesel engines not detonate? Is there no shockwave produced? I'm talking single injection event engines, multi-injection changes everything.

When they are operating correctly, no. When their are problems, yes - a diesel engine can experience detonation and the associated mechanical damage just like a gas engine can.

Diesel engine situation is a little different. There is a normal ignition delay between the start-of-injection and the start-of-combustion which results in some portion of the fuel burning in premixed fashion which is responsible for the audible chatter of a diesel engine, but (A) it isn't the end-gas near the piston rings, it's in the vicinity of the injector - depending on how long the ignition delay is, (B) it isn't the entire fuel-air charge igniting like this, just a piece of it, (C) the charge is not homogeneously mixed at the time that this happens - so it doesn't all ignite at once. The normal ignition in a diesel engine starts with a rapid rate of pressure rise, but it should not be a detonation.

Diesel engines knock louder upon cold start because the ignition delay is longer.

Injection timing set too far advanced results in louder knock because (1) the temperature in cylinder is lower at the time of start-of-injection because the compression stroke isn't finished yet, (2) the longer ignition delay results in more fuel being in-cylinder and partially premixed by the time ignition happens. And yes, excessive ignition timing advance certainly can break stuff.

Newer modern-tech diesel engines are a lot quieter because the rate of injection is much more tightly controlled. It's not uncommon to split up the injection cycle into two parts - a small initial pulse that premixes and ignites followed by the main injection event that burns progressively.

I was steering towards the shockwave not being the only cause of damage. In the diesel engine there is a shockwave at the start of ignition but as BP said, it's a small portion of the charge burning and the cylinder pressures are still low. The rapid combustion during detonation causes a spike in cylinder pressure and the associated temperature. The shockwave things the boundary layers. One can have a shockwave, a knock, without damage. Maybe we should use detonation to imply a combination of shockwave and heat.

In a properly functioning diesel engine there is no shock front.

The shock front is what separates normal combustion from detonation.

Tug? (And anyone else) what is your opinion on Ether, starting fluid use in Diesel engines? Starting fluid happens. —-to make a colloquialism of it. Buy can it be used safely, should it be?

SwinnyGG. You make some strong points, particularly the knock-down on knock. To defend the use of knock above isn’t really necessary since it was used in that particular article to talk-the-talk so to speak. Literature on the subject uses acronyms that are listed above, never knock, and the distinction being drawn dividing detonation into 2 categories is academic, it doesn’t apply to us here, rather the moon and stars are witnesses I believe.

Starting fluid + glowing glow plug = bad news.

Dimethyl Ether, DME, definitely should be used as a fuel, or additive because:
“<it> has one of the highest well-to-wheel efficiencies with light and heavy-duty DME-fuelled vehicle efficiencies as 19% and 22.5%, respectively”

DME is made from methane and syngas from biomass, and in terms of CO2, is possibly one of the cleanest fuels, by virtue of carbon neutrality. Here is a wheel-to-wheel comparison that shows how it can blast electric vehicles from contention: https://gmobility.eu/what-is-well-to-wheel/

... the main difficulty being its boiling point at atmospheric pressure of -24 C means that you are starting over in terms of distribution and end-use.

Any sort of combustion engine that burns "a fuel" (no matter what it is) with air, and farts out its products of combustion, is going to have to deal with NOx.

Meanwhile ... I'm 22 km from home with my EV parked outside. The low-charge-warning was on when I got here (having not bothered plugging in the last three days), but the GOM says I have plenty of charge left to get home, where I can plug it in.

Diesel engines used to come with attached ether tanks just for starting. Modern direct inject diesel engines have rendered ether obsolete. If your engine can't start without ether it's already broken. Ether isn't going to break it more.

Welcome to the, “Ether isn’t going to break it more?” NoobTube Challenge!

I’ve seen mechanics do cold-starts, spraying abundant ether, total abandon, and also the reverse where mechanics act like it’s live grenade . Thanks for the word on this.

Warning, not on topic!

For example, I had to start this engine that has been ingesting salt water. There was still residual water in the intake manifold so I had to use ether to get it going.



The owner warned me about breaking piston rings. They leased me a boat that didn't run. I was damn well going to make that engine start so I could start earning revenue again.

I really despise this series of engines.