Talk:BMW M20

K-Jetronic

Did some of the eta engines come with K-Jetronic? The eta section contradicts itself later on where it claims all eta engines used Bosch Motronic instead. Lavenderbunny (talk) 00:30, 4 March 2008 (UTC)

Actually, the first reference to K-Jet talks about the head design, only the 2nd one is talking about engine management specifically. But the question remains whether early 325e cars used the Motronic or K-Jet. Information is conflicting: http://forums.bimmerforums.com/forum/showthread.php?t=1705552, http://bmwfans.info/parts/catalog/E30/4-doors/USA/325e-M20/LHD/A/1984/august/browse/fuel_preparation_system/ versus http://en.wikipedia.org/wiki/BMW_5_Series_(E28)#European_model_range (same engine in 1981-1988 528e listed as motronic) and http://84.45.115.78/e30zonewiki/index.php/Motronic (search for "042"). Maybe it differs between USA and Europe? — Preceding unsigned comment added by 1292simon (talk • contribs) 08:36, 20 January 2012 (UTC)

Tuning

Did any M20 come with a more restrictive airbox than the 325i? 1292simon (talk) 14:00, 20 January 2012 (UTC)

Using internet forums for sources

http://en.wikipedia.org/wiki/Wikipedia:Verifiability#Self-published_sources states that "self-published media, such as... Internet forum postings... are largely not acceptable as sources". Detailed information on the M20 is scant, except for forum quotes, so I think this is a case where forum sources need to be accepted. If there is a citation method that acknowledges a source is not normally considered reliable, please let me know and I will be happy to update the links. 1292simon (talk) 03:29, 22 January 2012 (UTC)

In most cases, citations from the most popular E30 forums have been used, therefore if the information is questionable it is likely to have been challenged in the thread. Where conflicting opinions have been expressed in the thread, the article acknowledges the range of opinions found. Therefore, please do not removing forum citations without reading the source material or providing an alternative.1292simon (talk) 03:44, 22 January 2012 (UTC)

Typ932, I requested some discussing here before you reverted my edit again. Can you please do the right thing this time, so we can avoid a revert war1292simon (talk) 21:08, 22 January 2012 (UTC)

Please read the rest of the section you refers to which clarifies which situations self-published sources can be used. It does not include cases where reliable information is rare or hard to come by. The information is also problematic in that it seems to violate WP:NOT in that Wikipedia is not a tuning guide. --Daniel 16:03, 23 January 2012 (UTC)

I think this is very clear case, both content and citations are not inline with Wikipedia rules. -->Typ932 ^T·C 17:19, 23 January 2012 (UTC)

Thanks for the info, Daniel J. I guess the whole Tuning section will have be removed then, which is a shame because I know many people who have found it useful 1292simon (talk) 02:01, 24 January 2012 (UTC)

Hey guys, does anyone know where the M20 tuning guide went? (if anywhere) It was quite a useful overview of what almost everybody who searches for M20 wants - Michael — Preceding unsigned comment added by 124.170.7.99 (talk) 05:32, 6 February 2012 (UTC)

It was deleted by User:Typ932 per the discussion immediately above. It does remain in the edit history however. --Daniel 06:13, 6 February 2012 (UTC)

External links modified

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External links modified

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M20B27 initially used Jetronic?

Does anyone know if there were B27 engines that used Jetronic instead of Motronic?

A part number for the early B27 DME is 12141286697. These links suggest this is Motronic: [1], [2], [3].

This page states that the early 325e uses an L-Jetronic control unit, however it has the same description for the 325i (which definitely uses Motronic), which suggests there is a mistake. Cheers, 1292simon (talk) 23:17, 25 March 2017 (UTC)

Horsepower units, specs table

Hi Johannes, could I please get your advice? Do you think the primary unit for this engine would be kilowatts (these BMW documents from the time describe the engine using kW first: 1, 2, 3, 4)?

Also, I am hoping for some feedback please on updating the specs table as below (same format as the M51 article but with displacement added).

Version	Displacement	Power	Torque	Years
M20B20	1,991 cc (121.5 cu in)	90 kW (121 hp) at 6,000 rpm	163 N⋅m (120 lb⋅ft) at 4,000 rpm	1976-1982
		92 kW (123 hp) at 5,800 rpm	170 N⋅m (125 lb⋅ft) at 4,000 rpm	1982-1984
			174 N⋅m (128 lb⋅ft) at 4,000 rpm	1984-1987
		95 kW (127 hp) at 6,000 rpm	164 N⋅m (121 lb⋅ft) at 4,300 rpm	1986-1992
M20B23	2,316 cc (141.3 cu in)	105 kW (141 hp) at 5,300 rpm	190 N⋅m (140 lb⋅ft) at 4,500 rpm	1977-1982
		102 kW (137 hp) at 5,300 rpm	205 N⋅m (151 lb⋅ft) at 4,000 rpm	1982-1983
		110 kW (148 hp) at 6,000 rpm	205 N⋅m (151 lb⋅ft) at 4,000 rpm	1983-1987
M20B25	2,494 cc (152.2 cu in)	126 kW (169 hp) at 5,800 rpm	226 N⋅m (167 lb⋅ft) at 4,000 rpm	1985-1990
		125 kW (168 hp) at 5,800 rpm	226 N⋅m (167 lb⋅ft) at 4,300 rpm	1987-1992
M20B27	2,693 cc (164.3 cu in)	92 kW (123 hp) at 4,250 rpm	240 N⋅m (177 lb⋅ft) at 3,250 rpm	1982-1987
		95 kW (127 hp) at 4,250 rpm	240 N⋅m (177 lb⋅ft) at 3,250 rpm	1987-1988

Regards, MrsSnoozyTurtle 02:10, 11 September 2021 (UTC)

This is actually a bit complicated, because BMW has used both SI and MKPS when the engine was presented at the Frankfurt IAA in 1977. As far as I'm concerned, the two (and only) models with MKPS as primary units were the carburetted 1990 cm³ models (122 PS) and the 2136 cm³ K-Jetronic models (143 PS) which both have "nice" SI power ratings (90/105 kW). All other models come with SI units first. The list is not complete, BMW made the M20B20 and M20B27 versions with four different power outputs: 88, 90, 92, and 95 kW. This owner's manual from 1985 lists the 88 kW version of the engine on page 151 (this version was made for the Austrian market because of its lower insurance and tax costs). The US version of the M20B27 engine for the E28 528e has a special tuning because of its catalyst converter, the owner's manual with the 90 kW rating (which is actually 121 horsepower, (not Pferdestärke)) can be found here on page 28; unlike the other ratings – which are DIN 70020 ratings – the 121 hp rating is SAE net. I suppose the US version was never DIN-rated, but it could be equivalent to the German 90 kW version (at least the tech specs are identical), but that's just a guess. Best regards, --Johannes (Talk) (Contribs) (Articles) 23:31, 14 September 2021 (UTC)

Johannes Maximilian, thanks for all your help with this, I really appreciate it. The table above has been updated with the extra outputs you mentioned, hopefully I have understood that properly.

Oh, yes, that is quite tricky with those two early versions using MKPS but the rest use SI. Would you mind sending me the references for those two please?

As for how to format the entries in the table for these two versions, we could use "122 PS (90 kW)", but that would be very different from the rest of the table. Perhaps this is a special situation where something like "90 kW (122 PS; 121 hp)" is appropriate? Regards, MrsSnoozyTurtle 10:10, 16 September 2021 (UTC)

Hello MrsSnoozyTurtle, the 1977 press release can be found here. On page 5 they write: "Wesentliche Neuerungen sind die kleinen Sechszylindermotoren mit 2,0 und 2,3 Liter Hubraum (...) Die 2,0-Liter-Sechszylinder-Vergasermotoren leisten 122 PS (90 kW) (...) [Die Leistung des 2,3-Liter-Motors] liegt bei 143 PS (105 kW)" (=Substantial innovations are the small six cylinder engines displacing 2.0 and 2.3 litres. The carburetted 2.0-litre six-cylinder engine is rated 122 PS (90 kW) (...) [The 2.3-litre engine] is rated 143 PS (105 kW)). BMW explicitly mentions that the M20 engine is a new engine. On page 18 BMW lists the tech specs, and they are both given in in SI and MKPS units, with both systems presented in an "equally valid" way. However, it seems as if they have divided the natural number kilowatt ratings by 0.73549875 to get the PS figures. I'd argue that it's safe to use either system, and that we don't necessarily need to include MKPS here. But we should nonetheless still do that for these two models using the 90 kW (122 PS; 121 hp) unit order.

The problem with the M20 engine is that it was BMW's "standard" engine. They have made 346,943 units just for the BMW E28. The following table that I have made back in 2019 lists all of these versions; 216,469 units were 1990 cm³ versions, and 130,474 were 2693 cm³ versions.

Best regards, --Johannes (Talk) (Contribs) (Articles) 12:26, 16 September 2021 (UTC)

Post Scriptum: Bosch made various different versions of the L-Jetronic system (L, L2, L3, LE, LE2, LU, LH); I don't know exactly which version(s) these engines use except for the L-Jetronic engines with a 9.8 epsilon value (they have some sort of LE-Jetronic), and I'm pretty sure that none of the L-Jetronics used in the M20 engine were LH-Jetronic. Technically, the early Motronic systems are also L-Jetronic systems with a digital ECU (for both fuel injection and ignition management).

Model	BMW M20
Design	Water-cooled Otto-type petrol engine with cross-flow cylinder head, two valves per cylinder, belt-driven single overhead camshaft, rocker arm valve actuation
Aspiration	Naturally aspirated with resonance induction
Fuel system	Multi-point injection
Engine control unit	Bosch K-Jetronic, Transistorised battery ignition	Bosch L-Jetronic, Transistorised battery ignition	Bosch LE-Jetronic, Transistorised battery ignition	Digital ECU Bosch Motronic (DME 1.1)	Bosch L-Jetronic, Transistorised battery ignition	Digital ECU Bosch Motronic (DME 1.1)
Bore × Stroke	80 mm × 66 mm					84 mm × 81 mm
Displacement	1990 cm³					2693 cm³
Compression $\varepsilon$	9,8	9,4	9,8	8,8	9,8	11	10,2	9	10,2	8,5
Rated power (DIN 70020)	92 kW bei 5800 min−1		95 kW bei 6000 min−1		88 kW at 5800 min−1	92 kW at 4250 min−1	95 kW at 4250 min−1	90 kW at 4250 min−1	88 kW at 4250 min−1	95 kW at 4800 min−1
Max. torque (DIN 70020)	165 N·m at 4500 min−1	170 N·m at 4000 min−1	174 N·m at 4000 min−1	164 N·m at 4300 min−1	174 N·m at 4000 min−1	240 N·m at 3250 min−1		230 N·m at 3250 min−1	240 N·m at 3250 min−1	230 N·m at 3200 min−1
Exhaust gas treatment	None			Lambda-controlled three-way catalyst	None			Lambda-controlled three-way catalyst	None	Lambda-controlled three-way catalyst
References

References

Thanks Johannes, I will update the main specs table using the "90 kW (122 PS; 121 hp)" unit order for those first two versions.

Yes, it looks like there were many versions produced over the 16 years. Thanks for providing those specs with further details. It looks like the table in the article is missing the 2.0L version with 88 kW and the 2.7L versions with 88 kW (I didn't expect a 2.7L version to have such a low power rating!) and 90 kW. Regarding the 88 kW 2.7L versions, do you happen to know which models and years these were used in? Sorry if I missed it, but I couldn't find this version in the sources for that column of the table.

Also, sorry I don't understand what you mean about the early Motronic engines being L-Jetronic... this is all quite confusing! Regards, MrsSnoozyTurtle 05:27, 18 September 2021 (UTC)

BMW E30 with an 88 kW version of the M20B27 engine

The Austrian 88 kW version of the M20B27 engine has been available from February 1983 until the end of the E28 production in Germany. This is the first issue of the owner's manual addition for the 525e model (dated February 1983), and it already mentions the 88 kW version. Interestingly, the eta version (id est the 525e model) was only introduced to the German market in April 1983. The owner's manual linked in the table above was released in August 1985. The M20B27 engine was also available in the BMW E30 (325e and 325es) from 02/1985 until 08/1987, and it was also available in the 88 kW version (only for the 325e though, see this owner's manual on page 150). Both the 528e and the 325es models were only available with the 90 kW version of the engine (so none of the 88, 92 or 95 kW options were available). The eta option proved to be unpopular with E30 buyers, and BMW dropped the engine from the lineup after less than three years – this is why you never see any facelift E30s with the eta engine.

The reason why the 2.7-litre 88 kW version has such a low power rating is the Austrian tax and insurance legislation. The engine is actually much more powerful than it might seem. This is because of its relatively high – keep in mind that this is a naturally aspirated two-valve engine – mean effective pressure of 1.12 MPa. Just to put this into perspective, the 3.5-litre M30 only has 1.06 MPa, and the bog-standard 2.0-litre M20 reaches 1.03 MPa. The mean effective pressure is a rating that allows comparing the performance of engines with different displacements. Multiplying the MEP with the engine displacement and dividing by 2 (since a four-stroke engine has a powerstroke once every two revolutions) gives the work performed by the engine in Joules. If this is multiplied with the engine speed in "per second" = s⁻¹ (this is why I like engine speed ratings in "per minute" = min⁻¹), the result is a J·s⁻¹ figure, which is power (= Watt). Because of the high MEP, the M20B27 produces much more power at lower engine speeds than the M20B20, despite their identical ratings. The reason why the M20B20 is not less powerful than the M20B27 is its higher engine speed. If the redline in the M20B27 is raised from 4250 min⁻¹ to let's say 6250 min⁻¹, it outperforms the M20B20 easily.

The Bosch L-Jetronic system is only a multipoint fuel injection system with a primitive, analogue ECU – it is limited to fuel injection, it does not control anything engine. This is why all L-Jetronic injected engines either have a traditional ignition distributor or a transistorised ignition system, and why L-Jetronic injected engines typically don't have catalyst convertes. The Motronic system is more or less identical to the L-Jetronic system, except for one thing: The Motronic system has an engine ECU (not only a fuel injection ECU), and the engine ECU is fully digital. It has all functions that are nowadays associated with an ECU (progrmamable engine map, ignition angle control, fuel metering, overrun fuel cutoff, lambda control, etc.), so a dedicated igntion system is not needed. Best regards, --Johannes (Talk) (Contribs) (Articles) 16:20, 18 September 2021 (UTC)

Great, I will add those sources to the table.

Many thanks for all of your explanations, today I have learned more than I ever thought possible about eta engines, mean effective pressure and Bosch ECU systems! Regards, MrsSnoozyTurtle 06:46, 19 September 2021 (UTC)