Maybe a misunderstanding of the magazine and the interviewed one as the thermodynamics don't change, these are like laws, like all other natural laws. Once the combustion duration is shorter, the pressure increase, depending on where of the crank angle it was intentionally located, runs a higher gradient over crank angle. A shorter duration need a faster combustion if the chamber geometry doesn't change while that is all happening
. Pressure is a direct result of the energy release, as temperature get instantaneously increased by the exothermal reaction. There is no delay in heat release, no delay in temperature increase it is a directly linked processional row of things happen in a very strong consequence and time row. Thence here is the room of things didn't change much since then. While...That is maybe old stuff. I was involved in an engine development of a technology which was invented in the late 80'ies of the last millennium and which is used in today's (2015-2022, maybe further) Formula 1 engines. That combustion processes was highly efficient (around 50 % at flywheel) and highly boosted (almost 100 psi) with a lambda around 2.0 (for you guys AFR 29.4:1 when AFR stoich = 14.7:1). The pressure gradient was around 116 psi/°ca and ignition timing around 10°-12° BTDC while peak pressure was around 8°-10° ATDC. Ignition delay was only a few degrees. Cylinder pressure at IGT was around 120 bar (1740 psi) and cylinder peak pressure was controlled to around 220 bar (3190 psi).
Even at those lean mixtures pre-ignition phenomena like oil induced ones can happen. We saw power cycles with 290 psi/°ca, which hammered the small eye bearing down to a thin paper.
The combustion process was designed as swirl-squish driven on this 174 mm x 190 mm engine, application is combined heat and power production: stationary, 85-95 % of the operation time at WOT and 80,000 h lifetime. Hence those engine are no lightweight, a 20 cylinder version of it has about 7 tons. The squish velocity was well above 45 m/s, peaking around IGT. These values may all sound well on the edge, but it worked very well and there are quite a lot in the field at customer sites.
There are things that don't change, but when Larry was designing his Soft Head combustion process design, it was maybe far off the daily business, but till today's business a lot of fields went ahead:
- reliability. Did you ever see a 80'ies engine running 80,000 h, whereof 90 % are at WOT?
- analysis. Today we log on these engines 300-2000 parameters to predict maintenance events. I've invented in that field a lot of stuff to help the customer to reduce cost and downtime.
- efficiency. This is no prototype, this is series
- precision. Because of the digitization we are able to control these online and to adapt it in several control fields from remote, we even see and are able to control cylinder pressure on some applications live at customer site or mobile applications like ships
- dynamic. The dynamic of a lean burn boosted need quite a good control setup like pilot control, nice closed loop control and well designed parts supporting the dynamic. Look into the Formula 1 stuff how fast they can switch from rich to lean in a massive huge parameter field. That are very complex controller strategies and ECU functionalities which are far ahead to that what Larry had available
There is much more, engine development didn't stand still, not after Larry, not after the thread start and will not stand still after my post. I am just a few minutes away of the place where the first Benz 3-wheeler run down street, where Robert Bosch released his first spark plug, where Porsche built not only 911's but also the E500 (the one with the V8 and still the best Mercedes chassis ever
) of Mercedes. Stuttgart is the center of a lot of inventions around the automotive and this is a pumping Motown where still 100's of patents each day states it is still actively pumping. I own a tiny company developing, building and tuning race engines but for the main job I work on fuel cell system like the PEMFC for mobile applications. Politically the ICE run here in Europe into the upper S-arm of the technology S. Drivetrain technology changes, we adapt as always.Within my 2-man company we are stretching the edge on the NA side and start a deep dive of my favorite, the combustion process design to keep up with the alternation of load and engine speed demand. We were already able to exceed 16 bar of BMEP over a bandwidth of 4000 rpm (4500-8500 rpm), that means 96 ftlb/Liter over 4000 rpm and at maximum 105 ftlb/Liter. In our next project we want to shift that torque curve 1000 rpm higher to be able to exceed 360 hp at flywheel. We do our best to push the limits in our side job hobby. We do all in house, head port development, combustion process development, crank drivetrain development a.s.o.. We learn from the past...
DTM (Mercedes, 320 g), Formula 1 (BMW M12, 1500 hp, 1,5 Liter, 528 g), Small Block V8 (Pankl, quite heavy), STW (Audi EA113, 320 hp, 2 Liter, 380 g)
...from our experience, knowhow and from a lot of calculation of designs by simulation and modelling. If it come true, I will have a chance to talk with the Formula 1 piston designer, who also developed the Audi S1 (Pike Peaks record < 11 min, 1987, Walter Röhrl) 3-plenum intake manifold and many more. Like Gandalf the Grew said "Things are in motion and cannot be undone!".
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