Cummins has used the designation L for several engines, some of which are of unrelated design. The Cummins L-series engine is a straight-six diesel engine designed and produced by Cummins. It displaces , and began production in 1982 as the L10 at the Jamestown Engine Plant in Jamestown, New York. After lengthening its stroke from 136 to 147 mm, its displacement was enlarged to 10.8 litres and the engine renamed M11, later ISM.

The ISL 9 and L9 engines are not related to the L10 engine, but instead based on the smaller C-series engine, with the 135 mm stroke of the C8.3 enlarged to 144.5 mm, together with 4 valves per cylinder, giving it 8.9 litres displacement.

The L10 displaces , and was available in either a vertical form, for upright use in trucks and buses, or horizontal form, for underfloor use in buses and trains. The L10 was Cummins's first competitive offering in the British bus market, as their earlier production had been too large and heavy. However, its high oil consumption and leaking gave it a troublesome introduction to the British market.

By 1994, it had been developed into the M11, and in 1998, Cummins ceased production of the old L-series engine. After the L10 was modified into the M11, the ISL9 was introduced to operate in the same market segment as the L10 had, yet with a better power-to-weight ratio, by enlarging the piston stroke of the older C8.3 engine. The Cummins L10 also has a sister engine which runs on compressed natural gas (CNG). That engine was introduced in 1992 as the L10G, then replaced by the L Gas Plus in 2001, and then by the ISL G, which is based on the C-series engine, in collaboration with Westport Innovations in 2008. The ISL engines were manufactured at plants in Rocky Mount, North Carolina and Darlington, England.

In 2016 onwards, the name ISL9 was simplified to L9. This L9, which is a stroked version of the C8.3 engine, bears no resemblance to the L10. The M11 engine is a stroked version of the L10.

In February 2023, Cummins announced that both the L9 and the X12 would be replaced by the X10 engine, which is slated for introduction in 2026 for the North American market.

Models

{| class="wikitable"

!Maker

!Name

!Displacement

!Fuel

!Years in production

!Found in

|-

| rowspan="4" |Cummins

|L10

|10L

| rowspan="4" |Diesel

|1982–1998

|

  • Rigid transit buses
  • Articulated Farm Tractors

|-

|ISL

| rowspan="3" |8.9L

|1999–2007

| rowspan="3" |

  • Rigid transit buses
  • Articulated transit buses
  • Diesel-electric hybrid motorcoaches
  • Rear-engine Type D school buses

|-

|ISL9

|2007–2017

|-

|L9

|2017–present

|-

| rowspan="5" |Cummins-Westport

|L10G

|10L

|CNG

|1992–2001

|

  • Rigid transit buses

|-

|L Gas Plus

| rowspan="4" |8.9L

| rowspan="4" |Natural Gas<!-- Do not change to CNG/RNG/LNG. -->

|2001–2008

| rowspan="4" |

  • Rigid transit buses
  • Articulated transit buses
  • some CNG motorcoaches

|-

|ISL G

| rowspan="2" |2008–2018

|-

|ISL G NZ

|-

|L9N

|2018–present

|}

Diesel-powered urban bus

: at 1300&nbsp;rpm, electronically governed at 2200&nbsp;rpm

: at 1300 rpm, electronically governed at 2200&nbsp;rpm

: at 1300 rpm, electronically governed at 2200&nbsp;rpm

Natural gas-powered urban bus (L Gas Plus, ISL G, ISL G NZ, L9N)

: at 1300 rpm, electronically governed at 2000&nbsp;rpm

: at 1300 rpm, electronically governed at 2100&nbsp;rpm

: at 1300 rpm, electronically governed at 2000&nbsp;rpm

;Firetruck/motorhome/truck<!-- what makes these "popular", and to whom, and by what verifiable source can we claim this in a Wikipedia article? -->

: at 1300 rpm, electronically governed at 2100&nbsp;rpm

: at 1300 rpm, electronically governed at 2100&nbsp;rpm

: at 1300&nbsp;rpm, electronically governed at 2200&nbsp;rpm

References

  • Cummins website
  • Cummins Westport (CNG) website
  • [https://web.archive.org/web/20171201131459/https://www.leegapower.com/worldwide-manufacturing-locations.htm]