GB2252129A

GB2252129A - Internal combustion engines,their exhaust systems and manufacture thereof

Info

Publication number: GB2252129A
Application number: GB9101755A
Authority: GB
Inventors: Andrew Charles Palmer
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1991-01-26
Filing date: 1991-01-26
Publication date: 1992-07-29
Anticipated expiration: 2011-01-26
Also published as: GB2252129B; GB9101755D0

Abstract

A series of substantially identical internal combustion engines is produced. The exhaust system for each engine is selected from a first series each incorporating a catalytic converter 15, and a second series, not including a catalytic converter but having the same back pressure characteristics as each of the first series. Each exhaust system of the second series may have a dummy converter 16, ie constructed using the same components as the catalytic converter in the first series but without a catalyst. Alternatively each exhaust system in the second series may incorporate a resonator 17 with a restrictor 22. <IMAGE>

Description

INTERNAL COMBUSTION ENGINES, THEIR EYBAUST SYSTEMS AND MANUFAZIURE THEREOF The invention relates to internal combustion engines and their exhaust systems and to their methods of manufacture.

Whilst catalytic converters are now commonplace, their fitment on new motor vehicles is mandatory in only a few countries. In use, they demand the universal availability of lead-free petrol and this, in conjunction with their additional cost, means that there remains a demand for vehicles with exhaust system which do not include a catalytic converter.

In general, an exhaust system incorporating a catalytic converter creates more back pressure than an exhaust system which does not include a catalytic converter. This makes it difficult to produce a series of engines with all features of the design, air intake, fuel and ignition system optimised for the required performance characteristic. Even where all the parts of the engine are identical, it remains a disadvantage if the ignition timing and/or fuel injection systems have different characteristics requiring different adjustments or different programming of electronic management systems.

According to one aspect of the invention there is provided a method of manufacturing internal combustion engines and their exhaust systems, the method comprising producing a series of engines each being substantially identical and each having substantially identical air intake, fuel and ignition systems; producing a first series of exhaust systems for said engines, each incorporating a catalytic converter; and producing a second series of exhaust systems for said engines, each excluding a catalytic converter but having substantially the same back pressure characteristic as each exhaust system in the first series.

According to a second aspect of the invention there is provided a series of internal combustion engines and their exhaust systems, each engine in the series being substantially identical and each having substantially identical air intake, fuel and ignition systems, a first series of exhaust systems for said engines, each incorporating a catalytic converter, and a second series of exhaust systems for said engines, each excluding a catalytic converter but having substantially the same back pressure characteristic as each exhaust system in the first series.

The invention will now be described by way of example and with reference to the accompanying drawing which shows an exhaust system for the internal combustion engine of a motor vehicle, the exhaust system having three alternative configurations.

Common to all three configurations is a downpipe section 11 and an intermediate and rear section 12 (shown truncated). The downpipe section 11 has a flange 13 for connection to the exhaust manifold of the internal combustion engine and a flexible section or decoupler 14 which allows the engine to move on its flexible mountings.

Between the downpipe section 11 and the intermediate and rear section 12 there is incorporated one of three alternative sections.

The uppermost alternative is a catalytic converter 15 which is generally conventional. It includes a monolith having a large number of parallel longitudinal passages each coated with a catalyst, eg a gamma alumina wash coat on a ceramic monolith base with a surface coating of platinum or a similar catalyst.

The middle alternative is a dummy converter 16 and is constructed in an identical manner to the catalytic converter 15 except that the platinum catalyst and possibly also the wash coat are omitted from the monolith. Thus the dummy converter 16 will have the same back pressure characteristics as the catalytic converter 15.

The lower alternative is a generally conventional resonator 17 which comprises a perforated tube 18 to interconnect the downpipe section 11 and the intermediate and rear section 12, an outer casing 19 and a packing 21 of mineral wool. To give the resonator 17 the same back pressure characteristics as the catalytic converter 15, there is a restrictor 22 in the perforated tube which can be a separate item or comprise formations (eg longitudinal ribs) in the tube 18.

For use with the catalytic converter, the downpipe section 11 has a tapped boss 23 for a lambda sensor or a gas sampler. This can be blocked up for normal use with the dummy converter 16 or resonator 17.

The invention may be applied to compression ignition as well as spark ignition engines.

Since no adjustments or changes in components have to be made between one type of exhaust system and another, production and servicing is greatly simplified and the chance that an engine is coupled to or tuned for the wrong exhaust system is eliminated.

Claims

1. A method of manufacturing internal combustion engines and their exhaust systems, the method comprising producing a series of engines each being substantially identical and each having substantially identical air intake, fuel and ignition systems; producing a first series of exhaust systems for said engines, each incorporating a catalytic converter; and producing a second series of exhaust systems for said engines, each excluding a catalytic converter but having substantially the same back pressure characteristic as each exhaust system in the first series.

2. A method according to Claim 1 wherein each exhaust system in said second series incorporates a dummy converter comprising the same components as each of the catalytic converters in the first series of exhaust systems but excluding a catalyst.

3. A method according to Claim 1 wherein each exhaust system in the second series incorporates a resonator incorporating a restrictor.

4. A series of internal combustion engines and their exhaust systems, each engine in the series being substantially identical and each having substantially identical air intake, fuel and ignition systems, a first series of exhaust systems for said engines, each incorporating a catalytic converter, and a second series of exhaust systems for said engines, each excluding a catalytic converter but having substantially the same back pressure characteristic as each exhaust system in the first series.

5. A series according to Claim 4 wherein each exhaust system in said second series incorporates a dummy converter comprising the same components as each of the catalytic converters in the first series of exhaust systems but excluding a catalyst.

6. A series according to Claim 4 wherein each exhaust system in the second series incorporates a resonator incorporating a restrictor.

7. A method of manufacturing internal combustion engines and their exhaust systems substantially as described herein with reference to the accompanying drawings.

8. A series of internal combustion engines and their exhaust systems substantially as described herein with reference to the accompanying drawings.