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Larry's Soft Head

General engine tech -- Drag Racing to Circle Track

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LotusElise
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Re: Larry's Soft Head

Post by LotusElise »

Quite some time when the this was questioned and even much more when Larry was developing this combustion process. Anyway, during skimming the thread I was triggered, by the sentence of Larry that things didn't change much during the years, to add my two cents here also. But first...
lil289 wrote: Wed Apr 12, 2006 8:15 pm "Because the mixture is more homogenous, it gives a faster burn that lasts longer - the ignited mixture expands more slowly":?:
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 :wink:. 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...
hydra wrote: Sat Apr 22, 2006 6:20 am ...From memory, the ideal rate of pressure rise is ~30psi/crank degree. Any more than that and combustion becomes noticeably rougher and power is actually LOST...
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 :D) 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...

Image
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!".
DAMPFHAMMER engine:
2000 ccm, Honda K20 NA engine
4000 rpm bandwidth of at least 192 ftlb
310 hp@8200 rpm
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Re: Larry's Soft Head

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=D> 8)
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Re: Larry's Soft Head

Post by swampbuggy »

Thanks for the pictures L.E. , I could not help but notice the labeled as an F-1 Rod was an H-Beam Design. Is that F-1 rod a fairly recent one ? Mark H.
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Re: Larry's Soft Head

Post by chimpvalet »

That chunky F1 rod dates back to the mid-Eighties, and lived in a 1.5 litre 4 cylinder.

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Re: Larry's Soft Head

Post by LotusElise »

swampbuggy wrote: Thu Sep 22, 2022 6:59 pm Thanks for the pictures L.E. , I could not help but notice the labeled as an F-1 Rod was an H-Beam Design. Is that F-1 rod a fairly recent one ? Mark H.
This is from the Paul Rosche Formula 1 engine (started end of the 70'ies), which had the highest ever used power in Formula 1. BMW run that program after Rosche introduced roof chamber heads into BMW racing series (2 Liter NA and further) in the 70'ies. Stroke was reduced to fullfill the 1.5 Liter limit for boosted engines, that was a penalty over not having a NA induction concept. But the boost levels and fuels developed hard this time. The chemical structure of the fuel was one of BMW's best secrets. Finally a pressure ratio of around 5:1 was run. Cylinder pressures were therefore in the higher 3 digit level. The guy who designed the piston is Peter Marlow, I will hopefully meet him this year. He is a very good engine designer which influenced the 70'ies, 80'ies quite much regarding some engine design principles and innovations.

Compared to the stuff the high revving engine later in the 90'ies and 00's show, this is quite different. Bending was the focus instead of pulling forces. As I said the engine speed levels needed some time to develop significantly over 12,000 rpm. There were developments in different race series in the 60'ies, were those limits already were exceeded by squish introduction. But as always, concepts go and come as generations of engineers go and come. Knowhow transfer is not a continuous thing.

A very good book about engine history of the 10'ies till 60'ies is given by Helmut Hütten, "Schnelle Motoren, seziert und frisiert", especially the fight of the US against the European engine develop scene, their overlays and differences in development velocity. A great book, but only if you like to read German language. I don't believe it is available in English.
DAMPFHAMMER engine:
2000 ccm, Honda K20 NA engine
4000 rpm bandwidth of at least 192 ftlb
310 hp@8200 rpm
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Re: Larry's Soft Head

Post by hysteric »

The chemical structure of the fuel was one of BMW's best secrets.
Now this is a very interesting statement. Could you please elaborate further on this if possible?
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Re: Larry's Soft Head

Post by LotusElise »

hysteric wrote: Fri Sep 23, 2022 6:44 pm Now this is a very interesting statement. Could you please elaborate further on this if possible?
The rules said 102 RON that time, which lead to pre-ignition, heavy knock and other disadvantages. To be able to get the boost up BMW and others exchanced a bigger amount with toluene (maybe most of it ;)). The octane rating at standard test didn't change, but the knock behaviour did quite significantly.
DAMPFHAMMER engine:
2000 ccm, Honda K20 NA engine
4000 rpm bandwidth of at least 192 ftlb
310 hp@8200 rpm
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Re: Larry's Soft Head

Post by hysteric »

LotusElise wrote: Sat Sep 24, 2022 4:03 pm
hysteric wrote: Fri Sep 23, 2022 6:44 pm Now this is a very interesting statement. Could you please elaborate further on this if possible?
The rules said 102 RON that time, which lead to pre-ignition, heavy knock and other disadvantages. To be able to get the boost up BMW and others exchanced a bigger amount with toluene (maybe most of it ;)). The octane rating at standard test didn't change, but the knock behaviour did quite significantly.
Thank you Lotus. Fascinating stuff.
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Re: Larry's Soft Head

Post by hysteric »

Hi Lotus,

Can you please elaborate on the fuel used for this engine and what is its intended use?
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.
Thanks again.
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Re: Larry's Soft Head

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hysteric wrote: Sat Sep 24, 2022 7:47 pm Can you please elaborate on the fuel used for this engine and what is its intended use?
Toluene has quite a good MON, RON rating: 112 and 124 respectively. With the math done you have to mix 84 % Toluene with 16 % n-Heptane (0 RON-rating) to get a 102 RON rating, which was necessary to pass the RON testing. See Honda's SAE article Glover, A. R., A. Yasuoka, I. R. Galliard, and Y. Matsumoto (1993), “Optimizing Formula 1 Engine Performance through Fuel and Combustion System Development". The trick is, Toluene has a much higher vaporization temperature (around 111 °C) then the n-Heptane (around 98 °C) and therefore the rating for RON testing (intake air temperature around 53 °C) is tweaked in that way that real application is not applying to that test, because of the different conditions. The Toluol can play it's higher flame speed better than in the testing, which is about 1.8/1 compared to n-Heptane.

RON- or MON-testing is a guideline for knock behavior, but one have to consider the differences of the test conditions to that of the aimed application.
DAMPFHAMMER engine:
2000 ccm, Honda K20 NA engine
4000 rpm bandwidth of at least 192 ftlb
310 hp@8200 rpm
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Re: Larry's Soft Head

Post by hysteric »

LotusElise wrote: Sun Sep 25, 2022 12:31 pm
hysteric wrote: Sat Sep 24, 2022 7:47 pm Can you please elaborate on the fuel used for this engine and what is its intended use?
Toluene has quite a good MON, RON rating: 112 and 124 respectively. With the math done you have to mix 84 % Toluene with 16 % n-Heptane (0 RON-rating) to get a 102 RON rating, which was necessary to pass the RON testing. See Honda's SAE article Glover, A. R., A. Yasuoka, I. R. Galliard, and Y. Matsumoto (1993), “Optimizing Formula 1 Engine Performance through Fuel and Combustion System Development". The trick is, Toluene has a much higher vaporization temperature (around 111 °C) then the n-Heptane (around 98 °C) and therefore the rating for RON testing (intake air temperature around 53 °C) is tweaked in that way that real application is not applying to that test, because of the different conditions. The Toluol can play it's higher flame speed better than in the testing, which is about 1.8/1 compared to n-Heptane.

RON- or MON-testing is a guideline for knock behavior, but one have to consider the differences of the test conditions to that of the aimed application.
Thanks Lotus for an other very informative post. I guess this statement from Larry sums it up really:
I studied every technical paper relative to combustion I could get my hands on. I worked with some brilliant engineers on mixture preparation and delivery methodology.
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Re: Larry's Soft Head

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hysteric wrote: Sun Sep 25, 2022 4:53 pm Thanks Lotus for an other very informative post. I guess this statement from Larry sums it up really:
You are welcome. The interesting thing starts with another paper in mind by Shinh E. et al., The role of intermediate temperature heat release in octane sensitivity of fuel with matching of RON, which separate the effects on Octane Sensitivity, which is RON-MON, of different blends and conditions, which goes well into chemical kinetics as well as low and high temperature effects on self ignition delay and pressure-time-history. I was interested in that stuff during my Livengood-Wu model built up to forecast knock margin for my engine development, which fit quite well for gasoline blends. Understanding this helps a lot to get the right fuel attempt for the application and engine concept or vice versa ;).
DAMPFHAMMER engine:
2000 ccm, Honda K20 NA engine
4000 rpm bandwidth of at least 192 ftlb
310 hp@8200 rpm
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Re: Larry's Soft Head

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LotusElise wrote: Sun Sep 25, 2022 12:31 pm Toluene has quite a good MON, RON rating: 112 and 124 respectively. With the math done you have to mix 84 % Toluene with 16 % n-Heptane (0 RON-rating) to get a 102 RON rating, which was necessary to pass the RON testing. See Honda's SAE article Glover, A. R., A. Yasuoka, I. R. Galliard, and Y. Matsumoto (1993), “Optimizing Formula 1 Engine Performance through Fuel and Combustion System Development". The trick is, Toluene has a much higher vaporization temperature (around 111 °C) then the n-Heptane (around 98 °C) and therefore the rating for RON testing (intake air temperature around 53 °C) is tweaked in that way that real application is not applying to that test, because of the different conditions. The Toluol can play it's higher flame speed better than in the testing, which is about 1.8/1 compared to n-Heptane.

RON- or MON-testing is a guideline for knock behavior, but one have to consider the differences of the test conditions to that of the aimed application.
Volvo Touring Cars 242T's were pretty dependant on Toluene mixed with LL Avgas in the mid 80's.
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Re: Larry's Soft Head

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Tom68 wrote: Mon Sep 26, 2022 3:44 am Volvo Touring Cars 242T's were pretty dependant on Toluene mixed with LL Avgas in the mid 80's.
Seems to be it was modern that time using that quite toxic octane adder. The 240T I don't know very well, the ETCC wasn't well known here. More popular were here the STW, DTM and BTCC were also Volvo participated with the 850 Wagon. A very extrem race car (950 kg min weight made it possible) and engine. The I5 was resistaned to put enough power on the table (low stroke because of the I5 thingy, huge total valve area, not optimal ports, ...), hence Volvo decided to reduce the inclined valve angle to push up the port efficiency for the valve size (steep port angles), similar to the wedge heads of the V8 you have in the US.

Welding wasn't allowed, they cut and bolted a new design around the race class rules. From around 265 hp with the OEM head and allowed workaround an added 60 hp were released by the steep port approach and the highest power figures in the field. No Toluene, but Toluene-like class rule bypassing :lol:.
DAMPFHAMMER engine:
2000 ccm, Honda K20 NA engine
4000 rpm bandwidth of at least 192 ftlb
310 hp@8200 rpm
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Re: Larry's Soft Head

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LotusElise wrote: Mon Sep 26, 2022 7:14 am
Tom68 wrote: Mon Sep 26, 2022 3:44 am Volvo Touring Cars 242T's were pretty dependant on Toluene mixed with LL Avgas in the mid 80's.
Seems to be it was modern that time using that quite toxic octane adder. The 240T I don't know very well, the ETCC wasn't well known here. More popular were here the STW, DTM and BTCC were also Volvo participated with the 850 Wagon. A very extrem race car (950 kg min weight made it possible) and engine. The I5 was resistaned to put enough power on the table (low stroke because of the I5 thingy, huge total valve area, not optimal ports, ...), hence Volvo decided to reduce the inclined valve angle to push up the port efficiency for the valve size (steep port angles), similar to the wedge heads of the V8 you have in the US.

Welding wasn't allowed, they cut and bolted a new design around the race class rules. From around 265 hp with the OEM head and allowed workaround an added 60 hp were released by the steep port approach and the highest power figures in the field. No Toluene, but Toluene-like class rule bypassing :lol:.
Did they reduce both angles or did they use lower intake and higher exhaust valve angles by angle milling the head?
A balanced person dares to stagger, and modify ports bigger
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