T Total: Lotus and the M.G. XPAG engine

Introduction

The engine series are neither technical treatise or Haynes Manuals. This information is readily available in published form or on the net.

Rather our study concentrates on how and why Chapman and his colleagues’ sourced engines and their contribution to Lotus success and sales.

In his selection of major mechanical components Chapman added both performance to a sophisticated chassis and extraordinary added value.

Lotus were not a major engine manufacturer until quite late on. Despite this they used and adopted a range of mainstream engines to extraordinary effect.

Chapman and Lotus practice provides inspiration for all Industrial Designers /Specialists in their search for urgency and added value.

Our study focuses heavily on the fitment of these engines along with a visual representation. We debate the appeal to owners / racers and the beneficial publicity accredited to the manufacturers.

We believe that subscribers will be well able from this base line to research specific topics according to their needs.

Subscribers might like to see complementary A&R articles including:

Lotus Mk.VIII

• The 1172 Formula
• Lotus Mk.VI – several themed
• Lotus Seven – -do-
• After Market Suppliers-Aquaplane, Elva ohv conversion etc.
• S.U. Carburettors-All Choked Up
• Coventry Climax Engines
• Austin Powers –Austin Engines
• Ford 1172 engines
• Ford Consul engine and pre cross flow , crossflow
• Cosworth engines
• Coventry Climax
• Heads you Win:Laystall-Lucas and Lotus

T Time

The following comparative data helps explain the importance of the MG engine;-

Standard Engine Data

Marque	Model	Bore	Stroke	CC	Net BHP	Rpm	C’Ratio	Carbs
Austin	7	63	68	848	31.5	5500	8.3	1	Zenith
Austin	A35	63	76	948		4750	8.3	1	Zenith
Austin	Sprite	63	76	98	42.5	5200	8.3	2	S.U.
Ford	Popular	63	92	1172	36	4500	7	1	Solex
Ford	Prefect	81	48	997	39	5000	8.9	1	Solex
Ford	Consul	82	79	1703	59	4400	7.8	1	Zenith
Hillman	Minx	79	76	1494	53	4600	8.5	1	Zenith

Statistics taken from the net:-

XPAG	1250cc	MG TB OHV engine 11HP.
XPJM	1140cc	Morris 10/4 ohv engine 10HP.
XPJW	1140cc	Wolseley 10/40 ohv engine 10HP.
USHM	918cc	Morris Minor MM SV engine 8HP.
XPEG	1488cc	MG TF OHV engine 13HP.
MPJG	1292cc	MG TA engine ohv 12HP.
MPJM	1292cc	Morris 12/4 OHV engine 10HP.
MPJW	1292cc	Wolseley 12/48 OHV engine 10HP.
APHM	803cc	Morris Minor MM OHV engine, 8HP.
APJM	948cc	Morris Minor 1000 OHV engine 10HP.
TPBG	1549cc	MG VA ohv engine 12HP.
TPDG	1705cc	MG ‘Cream Cracker’ TA engine.
QPJG	2322cc	MG WA ohv engine 18HP.
QPHW	2561cc	Wolseley 18/80 ohv engine 18HP.

XPAG standard engine data

XPAW standard engine data

Bore: 66.5mm Stroke: 90mm Capacity: 1250cc Firing Order: 1342 Spark Plugs: Champion L.10.S Compression Ratio: 7.25:1 Valve timing: inlet opens 10 degrees BTDC, closes 57 degrees ABDC. Exhaust opens 52 degrees BBDC, closes 24 degrees ATDC. Valve lift: 8mm inlet & exhaust Tappet clearance: .019 hot Ignition timing: TDC Carburators: Twin 1 1/4″ SU B.M.E.P.: 125@ 2,600 RPM Safe maximum RPM: 5,700 Valve crash: 6,000 Capacity of combustion space: 45cc Cylinder head thickness: 3.0177 Thickness of head gasket: .045 Capacity of head gasket: 4.5cc Top Gear overall ratio: 5.125:1 MPH / 1,000 RPM: 15.84 Tyre size: 4.50×19 Octane Rating: Minimum requirements for knock free operation = 74 octane. For maximum power = 82 octane

MG Engine performance comparisons from Robson

Marque	MG	MG	MG
Model	TD	TF	MGA
Years	1949-53	1953-54	1955-59
Prod ‘No’s	29,664	6,200	58,750
Engine	Nuffield XPAG-type		BMC B series
cylinders	4 in-line		4 in line
valves	ohv		ohv
cc	1,250cc		1,489cc
bore/stroke	66.5x90mm		73.02×88.9mm
bhp	54@5200rpm	57bhp@5500rpm	68-72bhp@5500rpm
gearbox	4 speed		4 speed
max.speed	80mph		100mph
0-60mph	19.4sec		15sec
standing 1/4m	21.3sec		19.3sec
o’all fuel consum’	30mpg		28mpg
Marque	MG
Model	TF 1500
Years	1954
Prod ‘No’s
Engine
cylinders
valves
cc	1466cc
bore/stroke	72x90mm
bhp	63bhp@5000rpm
gearbox
max.speed	85mph
0-60mph	16sec
standing 1/4m	20.5sec
o’all fuel consum’	30mpg

Figure 1.Image from the net .This handbook would have guided tuners in the 1950’s and its likely Lotus owners with MG engines would have studied.

Figure 2.Exploded parts drawing from the net. The editors believe this image is more revealing than a photograph, where much of the engine is concealed from view. This also helps explain the construction and performance inherent in design.

Brief Tech spec from Buckley and Rees

MG TC/TD/TF

Engine: In line four

Capacity: 1250-1466cc

Power: 54-63 bhp

Transmission: 4 speed manual

No Built: 10,000 TC. 29,664 TD. 9,800 TF.

Figure 3.Editor’s photograph of i. Lotus Mk.VI fitted with Laystall improved M.G.engine and ii. MG engine in Y type saloon .This might have been the source of MG equipped Lotus cars?.

The MG Y-Type is a small saloon and limited production open four-seat tourer that was built by MG between 1947 and 1953.

When production ceased, 8,336 “Y” Types had been produced, 6,131 of which were “YA”s, 904 were “YT” Tourers and 1,301 were “YB”s.

Engine [edit]

The power unit was a single carburettor version of the 1,250 cc engine used in the latest MG-TB. This engine, the XPAG, went on to power both the MG-TC and MG-TD series. The MG Y Type saloon developed 46  bhp at 4,800 rpm, with 58.5 lb. ft. of torque at 2,400 rpm, the YT Tourer (with the higher lift camshaft and twin carburettors) develop 54 bhp (40 kW). With the exception of only the Rover Ten, which managed 2 additional bhp, the “Y” Type had more power than other British saloons of similar size. Indeed at the time many manufacturers were still producing side valve engines.

MG Gearbox

The Racing Engines Price list produced by Lotus in August 1955 quotes a price of £54 for MG.TC gearbox complete with remote control.

Figure 4.Image from the net. The MG engine was a performance engine that was accentuated by a standard matching complementary 4 speed gearbox that was compact and reasonably light. Significantly it was 4 speed compared with Ford 3 speed unit.

Figure 5.Further image from the net of item advertised as TA gearbox

T for Two

Taylor describing the Lotus Mk.VIII comments:-

“Since Peter Gammon had been enjoying such success with his M.G. powered Mk.VI the M.G.XPAG looked an attractive choice.

Chapmans prototype was built from M.G.and Morris parts, with a Laystall –Lucas light alloy cylinder head and twin SU carburetors and developed around 85 bhp at 6200rpm”

Images of Lotus with MG engines

Vis Mk.VIII

Morland includes 2 examples of the Lotus Mk.VI with excellent photographs.

Form and Function

Subscribers are invited to examine this sketch in conjunction with existing working drawing of Lotus Mk.VI

Figure 6.Editors sketch drawing of M.G.XPAG engine in front and side elevation

Performance figures [approx.]: taken from Lotus Mk.VI sales brochure

ENGINE		STANDARD	MEDIUM	HIGH
Ford 10	Degree of tuning	Normal/Perfect	Limits of 1172 Formula	Special cam etc.
	Maximum speed	75 mph	88 mph	94 mph
	Petrol consumption	45 mpg	48 mpg	40 mpg
	Standing 1/4 mile	21 secs.	19 secs.	17.5 secs.
Ford Consul	Degree of tuning	Normal Consul	Twin Carbs etc.	Special cam etc.
	Maximum speed	99 mph	106 mph	113 Plus
	Petrol consumption	40 mpg	42.5 mpg	38 mpg
	Standing 1/4 mile	18.8 secs.	17.4 secs.	16.5 secs.
M.G	Degree of tuning	Normal 1250	Max.of 1250	1500 Special cam etc.
	Maximum speed	104 mph	113 mph	120 mph
	Petrol consumption	40 mpg	42.5 mpg	38 mpg
	Standing 1/4 mile	17.8 secs.	16.5 secs.	15.8 secs.

Lotus Mk.VI –MG-Laystall

Laystall tuned engines gave a performance advantage. A dedicated A&R articles outlines their contribution.

Figure 7.Editors sketch of Laystall tuned engine in Lotus Mk.VI

Lotus Mk.VI: UPE 9

The editors attribute considerable credit to this car and the early establishment of the Lotus reputation and mystique. This car and its driver dominated a season and wiped the board often against much more expensive and sophisticated machinery.

Admittedly UPE 9 was possibly built to a very high specification with components and details not incorporated in the more mainstream Ford 1172 cars.

Possibly much of the success of UPE 9 could be attributed to its specially prepared MG engine.

Later Chapman would use the MG engine in the Lotus Mk.VIII

He gave this car an extraordinarily aerodynamic body designed by Costin in order the limitations of a mass-produced engine could be compensated for.

RAC British GP. Silverstone, 17th July, 1954

No.	Car	Chassis	Registry	Engine	Type	Size	Cyl.	Turbo
1	Buckler
2	Kieft		LDA 1	Climax	FWA	1100 cc
3	Kieft			Climax
4	Lotus Mark VI
5	MG Special			MG
6	Morris Minor			Riley
7	Osca MT4	1134	MO24307	Osca	no:1123	1100 cc	L4	N/A
8	RWG			MG
9	Porsche 550	09		Porsche		1100 cc	F4 2v DOHC	N/A
10	Lotus Mark VIII			MG
11	Lotus Mark VIII	8/01	SAR 5	MG		1500 cc	L4
12	Lotus Mark VI		UPE9	MG		1500 cc	L4
13	Lotus Mark VI		NUF 100	MG
14	Connaught ALSR	12	MCA 200	Lea Francis		1500 cc	L4	N/A
15	Lotus Mark VIII			Connaught		1500 cc	L4
16	Cooper Disco Volante			Connaught		1500 cc	L4
17	Cooper T29			MG
18	Gordini T15S	0018S		Gordini		1500 cc	L4
19	Kieft AJB
20	Killeen K1	K1		MG	XPAG	1500 cc	L4
21	MG TD Special			MG
22	MG			MG		1500 cc
23	MG		…AH.	MG
24	Lister	BHL1	MER303	MG		1500 cc
25	Tojeiro			MG
27	Leonard			MG		1500 cc	L4
29	Lester T51		MG 6850	MG
30	Osca MT4			Osca		1350 cc	L4	N/A
31	Tojeiro			MG
32	Turner
33	Porsche 550			Porsche		1500 cc	F4 2v DOHC	N/A

Entered cars that did not arrive:

No.	Car	Chassis	Registry	Engine	Type	Size	Cyl.	Turbo
26	Leonard			MG
28	Leonard			MG

Learning Opportunities

Our learning /educational opportunities are intended to be challenging thought provoking and requiring additional research and/or analysis.

These opportunities are particularly designed for a museum/education centre location where visitors would be able to enjoy access to all the structured resources available in conjunction with any concurrent exhibition.

In this instance we suggest the following might be appropriate:-

• Outline MG marque history – what are the origins of the engine?
• What speed records did MG undertake? How might this have developed the engine?
• What were the likely donors for the MG powered Lotus in period?
• What were the advantages of the MG 4 speed gearbox?
• In addition to MG engine identify other significant specification of UPE 9 that gave it such edge?
• Was UPE 9 “credible” in terms of performance /race results? What was the contribution of the owner driver?
• What other manufacturers / marques used Mg engines in specialist brands?
• Identify other significant Lotus cars that used MG engine, numerically and race results wise / publicity – how important was the contribution?
• Estimate the cost effectiveness of the MG engine over other alternatives
• To what extent did Chapman need to give the MG engine an aerodynamic body to compensate and compete against better funded marques?

Exhibitions, Education and Economics

In the museum context the editors believe that commercial considerations are both necessary and complementary with its educational objectives.

For these reasons our suggested outline Business Plan includes provision for promoting products and services which share Chapman’s ideals of mechanical efficiency and sustainability. In addition we propose merchandising that explain and interprets the social and cultural context of Chapman’s designs in period. It’s suggested there will be catalogue for on line purchasing.

In this instance the following are likely to prove both educational and entertaining: –

• Lotus’s “T” time
• Suited Lotus down to a T
• T Total
• Lotus :Crossing their “T’s”
• Lotus with a capital “T”

Conclusion

The MG engine powered the Lotus

It therefore powered racing and road cars.

It was a superb piece of industrial design ; functional and utilitarian .

It was successful in racing gaining publicity and inspired modification, tuning and a generation chassis designers.

The engine was attractive to owners and generated sales. Exports were possible because of the international spares availability.

These mass-produced engines were robust, inexpensive, widely available and spawned aftermarket components industry. Furthermore, they invited experimentation, and helped facilitate competition and design diversification. Thus assisting and elevating British motor racing :design , engineering , manufacture and of course drivers.

In the case of the MG it contributed significantly to a generation of sports racing cars and race formula in the early to mid 1950’s. It had considerable appeal in the USA.

The engine has continuing legacy and relevance and being such a significant piece of industrial design is fully worthy of analysis and appreciation.

Added value is an extremely important of Industrial Design, Chapman exploited to maximum effect and its principles are significant for a young entrepreneur’s with low capital wishing to enter the market.

Reference:

Classic Cars. Buckley and Rees.Southwater.214.

ISBN: 9781780193977

The Cars of BMC.Robson.MRP.1999.

ISBN: 1899870415

The Lotus Book. Taylor .Coterie.

Lotus Seven. Morland.

Please note the editors of the A&R attempt to give the broadest spectrum of references but not all are available for consultation in an article. However by noting their existence it may assist students in their research.

*Items in italics non A&R library books.