Is hopping up a MG TD off or on topic?

They even called it Powerful

December 1951 Science and Mechanics magazine<TABLE width=650 bgColor=#ffffff><TBODY><TR><TD align=middle>
<TABLE width=550><TBODY><TR><TD vAlign=top align=middle>
[SIZE=-1]
<CITE>Andy White taking the MG around a sharp turn near the top of Mt. Washington.</CITE>[/SIZE]

</TD></TR><TR><TD vAlign=top align=left>[SIZE=-1]KNOWN as "the world's fastest small car"-and part of a family boasting a long string of speed records to support that claim, the MG T.D., a 2-passenger sportster that has found wide acceptance in American circles, lived up to its reputation for high performance in the Motor Vehicle Research trial run. It is in no way comparable to the two family-type cars tested at the same time. Its engine's high-pitched whine serves notice of the MG's ability to show its heels to almost anything-of the same power-on the road.[/SIZE] <TABLE width="100&#37;"><TBODY><TR><TD width=200> </TD><TD vAlign=top align=middle>[SIZE=-1]<CITE>Checking location of oil filler cap in M.G.</CITE>[/SIZE]</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE><TABLE width=550><TBODY><TR><TD vAlign=top align=left width=250>[SIZE=-1]<SPACER TYPE="BLOCK" WIDTH="15">Designed strictly, therefore, as a sports automobile with a rakish appearance appealing to the youthful spirit in all men, the MG lacks the comfort of a family sedan of the type most American owners are accustomed to. Andy White, who drove it "like a mountain goat" up Mt. Washington's tedious twists and steep inclines, reported that it answered the steering wheel like a racer-an immediate response that sometimes had him clinging to the wheel on curves. The driver, once he has folded his legs and gotten inside, finds he has plenty of operating room, in spite of the fact that he is sitting almost against the 54.4 hp engine. This power plant is standard for the T.D. model and it is not especially fitted for racing events.
<SPACER TYPE="BLOCK" WIDTH="15">This particular car had been driven slightly more than 14,000 miles before the test, therefore conceivably might have been beyond the point of peak performance, especially if it had been used in competition. [/SIZE]</TD><TD> </TD><TD vAlign=top align=left width=250>[SIZE=-1]Nevertheless, it performed beautifully, plunging up Mt. Washington at an average speed of 39.5 mph, with top speed of 47 mph. Two-thirds of the climb was accomplished in second gear and one third in third gear. Low and high gears were not used. Driver White calls it the best car-in its size and horsepower-for mountain driving that he has ever seen.
<SPACER TYPE="BLOCK" WIDTH="15">As for fuel economy, the MG averaged 35 at 30 mph, 33.25 mpg at 40 and 29.5 mpg at 50. Its light weight -.2,016 pounds, ready for the road - probably is an important factor here. In the acceleration tests, the car went from 0 to 50 mph in the exceptionally fast time of 14.9 seconds - there's no doubt this car was built for sparkling performance. Its pickup from 0 to 60 mph is measured at 23 seconds. And its best cruising speed or harmonic balance point - is around 67 mph.
<SPACER TYPE="BLOCK" WIDTH="15">One feature that caught Andy White's eye was the complete tool kit housed in a neat compartment under the hood. A sturdy jack and lug [/SIZE]</TD></TR></TBODY></TABLE>
</TD></TR></TBODY></TABLE><TABLE width=650 bgColor=#ffffff><TBODY><TR><TD align=middle>
<TABLE cellPadding=6 width=550 border=BORDER><TBODY><TR><TD vAlign=top align=left width="60%"><TABLE cellSpacing=0 width="100%"><TBODY><TR><TD align=middle>MG Sportster Performance</TD></TR></TBODY></TABLE>
[SIZE=-1]DATE OF TEST:- July 19, 1951
MAKE OF CAR: MG T.D. 2-passenger sportster
DRIVER: Andy White
WEATHER CONDITIONS: Temperature 71&#176; F., humidity 63%, wind 13 mph
MILEAGE AT START OF TEST: 14,721 miles

[/SIZE] <TABLE cellSpacing=0 width="100%"><TBODY><TR><TD align=middle>TEST DATA</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD vAlign=top align=left width="60%">
[SIZE=-1]FUEL ECONOMY (in mpg): (checked with velocity flow meter, gas volume meter and Mile-O-Meter, a vacuum gage; level road)
North Run ..............................
South Run .............................
Average .................................
ACCELERATION:
(timed electrically)
zero to 50 mph .......................
zero to 60 mph .......................
HARMONIC POINT (or Optimum Cruising Speed): .......
TOP SPEED:
speedometer ..........................
actual ....................................
SPEEDOMETER ERROR (at Top Speed ............................
Hill Climbing:
(on 8-mile incline with grades of 12% to 29% up Mt. Washington)
(a) Top speed and gear ............
(b) Pct. of time in gear .............

BRAKING EFFICIENCY:
(checked with standard brake efficiency meter)

AIR-FUEL RATIO: ..................




IGNITION COIL OUTPUT: .......
[/SIZE]</TD><TD vAlign=top align=middle width="40%">[SIZE=-2]Miles Per Hour[/SIZE] <TABLE width="100%"><TBODY><TR><TD>[SIZE=-2]20[/SIZE]</TD><TD>[SIZE=-2]30[/SIZE]</TD><TD>[SIZE=-2]40[/SIZE]</TD><TD>[SIZE=-2]50[/SIZE]</TD></TR><TR><TD>[SIZE=-2] [/SIZE]</TD><TD>[SIZE=-2] [/SIZE]</TD><TD>[SIZE=-2] [/SIZE]</TD><TD>[SIZE=-2] [/SIZE]</TD></TR><TR><TD>[SIZE=-2] [/SIZE]</TD><TD>[SIZE=-2] [/SIZE]</TD><TD>[SIZE=-2] [/SIZE]</TD><TD>[SIZE=-2] [/SIZE]</TD></TR><TR><TD>[SIZE=-2] [/SIZE]</TD><TD>[SIZE=-2] [/SIZE]</TD><TD>[SIZE=-2] [/SIZE]</TD><TD>[SIZE=-2] [/SIZE]</TD></TR><TR><TD>[SIZE=-2]36[/SIZE]</TD><TD>[SIZE=-2]35[/SIZE]</TD><TD>[SIZE=-2]32.5[/SIZE]</TD><TD>[SIZE=-2]28[/SIZE]</TD></TR><TR><TD>[SIZE=-2]36.25[/SIZE]</TD><TD>[SIZE=-2]35[/SIZE]</TD><TD>[SIZE=-2]34[/SIZE]</TD><TD>[SIZE=-2]31[/SIZE]</TD></TR><TR><TD>[SIZE=-2]36.12[/SIZE]</TD><TD>[SIZE=-2]35[/SIZE]</TD><TD>[SIZE=-2]33.23[/SIZE]</TD><TD>[SIZE=-2]29.5[/SIZE]</TD></TR></TBODY></TABLE>
<TABLE width="100%"><TBODY><TR><TD>[SIZE=-2]14.9 seconds[/SIZE]</TD></TR><TR><TD>[SIZE=-2]23 seconds[/SIZE]</TD></TR><TR><TD>[SIZE=-2]
67 mph[/SIZE]</TD></TR><TR><TD>[SIZE=-2]
83 mph[/SIZE]</TD></TR><TR><TD>[SIZE=-2]79 mph[/SIZE]</TD></TR><TR><TD>[SIZE=-2]
4 mph[/SIZE]</TD></TR></TBODY></TABLE>

<TABLE width="100%"><TBODY><TR><TD>[SIZE=-2]
47 mph in third[/SIZE]</TD></TR><TR><TD>[SIZE=-2]66% in third, 34% in second, none in first or fourth[/SIZE]</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD>[SIZE=-2]60% (at 30 mph stopping distance is 50.2 ft.)[/SIZE]</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD>[SIZE=-2]
1 &#189;-to-1 at idle, 14-to-1 at inter- mediate speed, 14&#190;t-to-1 to 15- to-1 at top top speed (lean mixture)[/SIZE]</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD>[SIZE=-2]20,000 to 23,000 volts (American cars have 12,000 to 18,000)[/SIZE]</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE><TABLE cellSpacing=0 width="100%"><TBODY><TR><TD align=middle>DRIVER'S OBSERVATIONS</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD>[SIZE=-1]ROADABILITY: Excellent, virtually no wander, steering wheel response is fast, due to this being a racing-type vehicle, clings to curves. [/SIZE]</TD></TR><TR><TD>[SIZE=-1]RIDING COMFORT: Fair, this is not a family-type car, therefore comfort is not stressed.[/SIZE]</TD></TR><TR><TD>[SIZE=-1]INSTRUMENTS: Fairly easy to read in day operation, difficult at night because of poor lighting; panel light dimmer helps to improve vision. [/SIZE]</TD></TR><TR><TD>[SIZE=-1]ACCESSORIES: Steering column is adjustable; tool kit in own box under hood, glove compartment can house radio; celluloid side windscreens are detachable; spare tire mounting is easily accessible-outside car at rear; both of individual seats are adjustable for angle of back and forward or backward. [/SIZE]</TD></TR></TBODY></TABLE></TD><TD vAlign=top align=left width="40%"><TABLE cellSpacing=0 width="100%"><TBODY><TR><TD align=middle>SPECIFICATIONS</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD vAlign=top align=left width="10%">[SIZE=-2](a)[/SIZE]</TD><TD vAlign=top align=left>[SIZE=-2]ENGINE: 4-cylinder, overhead valves Bore: 2.56" Stroke: 3.541 Brake hp: 54.4 at 5,200 rpm Compression ratio: 7.25-to-1 [/SIZE]</TD></TR><TR><TD vAlign=top align=left width="10%">[SIZE=-2](b)[/SIZE]</TD><TD vAlign=top align=left>[SIZE=-2]TRANSMISSION: 4 forward, 1 reverse, gear shift.
Rear axle: ratio 5.125-to1 (top gear)[/SIZE]</TD></TR><TR><TD vAlign=top align=left width="10%">[SIZE=-2](c)[/SIZE]</TD><TD vAlign=top align=left>[SIZE=-2]EXTERIOR (see drawing):
Wheelbase: 94"
Weight: 2,016 (ready for road)[/SIZE]</TD></TR><TR><TD vAlign=top align=left width="10%">[SIZE=-2](d)[/SIZE]</TD><TD vAlign=top align=left>[SIZE=-2]INTERIOR:
Headroom: 35"
Hiproom: 44&#189;" (full width of interior)
Legroom: limited (distance from seat cushion to floor, 52") [/SIZE]</TD></TR><TR><TD vAlign=top align=left width="10%">[SIZE=-2](e)[/SIZE]</TD><TD vAlign=top align=left>[SIZE=-2]STEERING:
Lock to lock: 2&#189; turns of steering wheel
Turning circle: 31' 3"
Adjustable steering column[/SIZE]</TD></TR><TR><TD vAlign=top align=left width="10%">[SIZE=-2](f)[/SIZE]</TD><TD vAlign=top align=left>[SIZE=-2]VISIBILITY:
(For 5' 8" driver)
Driver's eye to road between left headlight and hood: 18'
Driver's eye to road over center of hood: 30' (approx.)
Driver's eye to road between right headlight and hood: ; 20' 10&#189;" [/SIZE]</TD></TR><TR><TD vAlign=top align=left width="10%">[SIZE=-2](g)[/SIZE]</TD><TD vAlign=top align=left>[SIZE=-2]MISCELLANEOUS:
Battery: 12 volts (electric fuel system)
Tires: 5.50 x 15
Springing: front, independent; rear, semi-elliptic
Parking brake located to driver's right between the seats
Electric windshield wiper
Spare tire mounted on rear[/SIZE]</TD></TR></TBODY></TABLE>
<TABLE cellSpacing=0 width="100%"><TBODY><TR><TD align=middle>ADVISERS ON TEST PROCEDURES</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD>[SIZE=-2]PROF. DEAN FALES, chassis construction authority, Massachusetts Institute of Technology, Boston, Mass.[/SIZE]</TD></TR><TR><TD>[SIZE=-2]DR. JOHN M. COLONAS, chief engineer, Commercial Filters Corp., South Boston, Mass.[/SIZE]</TD></TR><TR><TD>[SIZE=-2]LEONARD BELL, Ignition authority, "Mallory Electric Co., Detroit, Mich.[/SIZE]</TD></TR><TR><TD>[SIZE=-2]HENRY PRATT, authority on automotive fuels, American Oil Co., Baltimore, Md.[/SIZE]</TD></TR><TR><TD>[SIZE=-2]FRANK THILOW, service and lubricating engineer, American Oil Co., Baltimore, Md. [/SIZE]</TD></TR></TBODY></TABLE>
<TABLE width="100%"><TBODY><TR><TD vAlign=top align=left width="10%"> </TD><TD vAlign=top align=left>[SIZE=-1]MOTOR VEHICLE RESEARCH herewith certifies that these are the true and accurate findings in tests conducted on the automobile named under the conditions specified. [/SIZE]


[SIZE=-2]A.J. White
Motor Vehicle Research
Gale-Hall Engineering, Inc.[/SIZE]</TD><TD width="10%"> </TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>
</TD></TR></TBODY></TABLE><TABLE width=650 bgColor=#ffffff><TBODY><TR><TD align=middle>
<TABLE width=550><TBODY><TR><TD><TABLE width="100%"><TBODY><TR><TD vAlign=top align=left>[SIZE=-1]wrench that really work were among the comprehensive array of tools-something of a novelty to the American driver. In addition, the MG's. driver reported, "at last we have a real adjustable seat, one that can be adjusted both for the angle of the back and forward or back for leg space. That's important in any car."
<SPACER TYPE="BLOCK" WIDTH="15">One drawback in the MG is the lack of adequate vision, from the driver's position to the road in front of the car. The driver sits so low that an object less than 26 ft. 8 in. ahead of the bumper cannot be seen over the center of the hood. Looking between the left headlamp and the radiator cap, the driver can see the road at a distance of only 18 ft. while the distance on the right side, between headlamp and radiator cap, is 20 ft. 10&#189; in. from driver's eye to the road.
<SPACER TYPE="BLOCK" WIDTH="15">Members of the New Hampshire state highway patrol participated in the speed tests, achieving a top of 83 mph on the MG's speedometer. The runs, made over a 1&#189;-mile stretch of the New Hampshire turnpike, revealed a speedometer error of 4 mph in this particular car-about the degree of accuracy found in most American speedometers. Incidentally, the New Hampshire turnpike has a surface that is almost ideal for many types of open road testing and the mileage measurements between bridges are accurate within 1/10th of a foot.
<SPACER TYPE="BLOCK" WIDTH="15">One instrument that is not common on U.S. built cars is the 5 in. tachometer mounted on the MG's easy-to-read dash. This counts engine revolutions, of course, enabling the driver to keep an eye on power plant operation. The MG's 4-cylinder, overhead valve engine turns up its peak horsepower at 5,200 rpm, which puts it in the high speed class. Coupled with that is a rear axle ratio of 5.125-to-1 in top or fourth forward speed. The engine's compression ratio of 7.25-to-1 compares favorably with that of American automobiles, most of which are below that figure.
<SPACER TYPE="BLOCK" WIDTH="15">The MG's engine is easily accessible for repairs and [/SIZE]</TD><TD vAlign=top align=middle width=270>[SIZE=-1]
<CITE>Lon Bell holding on the racing type of emergency brake in the MG located at the driver's right.</CITE>

<CITE>Checking the MG seat change mechanism, which permits you to adjust either the back or the actual seat. </CITE>[/SIZE]
<TABLE width="100%"><TBODY><TR><TD>[SIZE=-1]bad feature, in the test crew's opinion, was the arrangement of brake, clutch and accelerator pedals. The pedals, they agreed, should be further apart to prevent overlapping of the 2 pedals by the sole of the foot.
<SPACER TYPE="BLOCK" WIDTH="15">One impressive thing about the tough Mt. Washington run was that the MG, as well as the other two cars, came through the 8-mile grind without a single mechanical failure. Wheel-slippage was practically non-existent on all three-and in this case of the MG, which had some pretty "bald" rear tires on it during the test, this reflected particular credit to the road hungry feel of perky and powerful little sportster. [/SIZE]</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD vAlign=top align=left>[SIZE=-1] servicing, but the test crew found the sharp little hood latches hard on the hands. And, they also found the hood must be brought down absolutely straight to prevent banging into the chrome headlamps. The electric windshield wiper on this '51 T.D. had a small follow rod that pinched fingers unless the driver was careful in turning it on and off. Another [/SIZE]</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD width=180> </TD><TD vAlign=top align=middle width=366>[SIZE=-1]<CITE>Lon Bell and Andy White with the two performance motors and broke- motors mounted in the MG just prior to running the tests. </CITE>[/SIZE]</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

 

Performing Midgets

<TABLE cellSpacing=0 cellPadding=10 width="50&#37;" bgColor=#ffffff><TBODY><TR><TD></TD></TR><TR><TD><TABLE width="100%"><TBODY><TR><TD vAlign=top align=left width="50%">[SIZE=+4]T[/SIZE][SIZE=-1]HE M.G 'Midget is a car that has had a very long and successful life, and in one or other of its many forms it has been owned, loved and longed for by a large number of people interested in motoring. In the various forms in which it has appeared since its introduction its character and general conception have remained unchanged. However, many detail changes have been made through the years in the interests of performance, comfort and economy. During this process the car has, to a certain extent, grown up. For example, the power unit has a capacity of 1,250 c.c. compared with 847 cc. at the beginning, in 1929. The present model, known as the TD, also has independent front suspension and two leading shoe brakes, to name only two chassis features. Although the body is now larger it still [/SIZE]</TD><TD vAlign=top align=left width="50%">[SIZE=-1]retains the family likeness of its ancestors, and the car not easily mistaken for any other marque.
In view of its popularity, and, the type of owner for which it is designed, there is no'doubt that where several M.G. owners are gathered together the subject of the performance of their respective cars will be freely discussed.
The question of tuning for increased performance is one on which much has been said, and is something that can lead to either success or disappointment. In either case it is likely to be costly in both time and money. With this in mind the M.G. company have very wisely carried out a considerable amount of development work to guide the owner in his quest for improved performance. Brief details of a number of different tuning stages have been listed in [/SIZE]</TD></TR></TBODY></TABLE></TD></TR><TR><TD><TABLE width="100%"><TBODY><TR><TD></TD><TD>[SIZE=-2]When tuned to Stage 5 the 1 1/2-litre engine in supercharged form develops 97 b.h.p., yet with the exception of valves and springs its components are standard. The Shorrock supercharger is belt driven from a pulley attached to the crankshaft in place of the starter dog, and it is supplied with oil from the main engine supply. External piping connects the oil filter mounted below the dipstick to the oil pump, which can be seen below the dynamo.[/SIZE]</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

 

<HR> <TABLE width="100&#37;"><TBODY><TR><TD vAlign=top align=left width=0></TD><TD vAlign=top align=left width="100%">[SIZE=-1]a booklet issued by the manufacturers, called Tuning for M.G. Midget Engines.
Now, it must be pointed out that although the manufacturers are in a-position to say what should be done, and also to supply the special components required for some of the stages, they are not able to supply new cars in a tuned form or to tune owners' cars, as this would, of course, interfere with normal production. However, if it is known what to do and what not to do there is a good chance of success. More important even than this, perhaps, is a clear idea of what the ultimate result is likely to be when the tuning is finished. Consequently, The Autocar has, over a period of several months, exhaustively road tested a TD M.G. in its various tuning stages from standard production to Stage 5.
Before any tuning is attempted it must be decided for what purpose the car is required; also-and this will to a certain extent be inter-related with the first consideration- what type of fuel is available to run it on. The fuel question is of vital importance, and until this has been decided very little tuning of any kind can be done. Each type and blend of fuel has what is known as a highest useful compression ratio; therefore, unless the octane rating of the fuel will permit, there is no point in increasing the compression ratio, which is one of the best-known methods of increasing performance. Another method of increasing engine output is by supercharging, which may also in some cases be accompanied by an increase in compression ratio. Apart from the fundamental changes of the type mentioned, there are two other ways of improving engine performance. One is to reduce the friction between the moving parts, and the other is to improve the volumetric efficiency or breathing. These two items are not brought about by any form of magic, but by hard work and skillful use of tools, much patience, a basic knowledge of what can be done and cannot be done, and still more hard work.

Making the Most of the Power

A stage-by-stage treatment-of the engine will be given later, but before this is done there are other aspects of the tuning that must be considered. Briefly, the performance of a car depends on the power required relative to the power that is available. Now, assuming that the total weight is not affected much during the tuning, and also that the body shape remains unchanged, the curve showing the power required to drive the car will remain the same.
To determine the required overall gear ratio it is necessary to have a knowledge of both the power required and the power available if the best overall performance is to be obtained. If the gear ratio has been determined for a car powered by an engine that develops, say, 54 b.h.p., as in the standard TD M.G., it is obvious that if the power out- put is increased to any marked degree some modification to the overall gear ratio will be required. If this is not done the engine will have exceeded its maximum safe working speed in r.p.m. before the maximum speed is reached corresponding to the power available. This means that for a given car, if the b.h.p. is increased I the m.p.h. per 1,000 r.p.m. of the engine on top gear must also be increased, and to do "this the gear ratio must be lowered [Thus providing a higher gear.-ED.] or a similar effect produced, for example, by fitting larger diameter tyres to the rear wheels. Modifications made to the axle ratio on the M.G. are listed in Table 1, and a graph shows the effect on the performance [/SIZE]</TD></TR></TBODY></TABLE>

 

<TABLE width="100&#37;"><TBODY><TR><TD vAlign=top align=left width="50%">[SIZE=-1]in the indirect ratios produced by these changes. The effect of weight is important in tuning, but it should be remembered that it is the total drag that affects the maximum speed, 'and the weight that affects acceleration. However, if the weight is not kept to a minimum the resultant loss of potential acceleration may mean that the car must slow down for a comer or because of other traffic, before its maximum speed is ever reached; also, the lighter the car the less work there is for the brakes.
The car used for these tests was first submitted in standard trim. It was put through its paces, and, in fact, given the normal Road Test routine, including several hundred miles of normal road running to enable the driver to get to know the car as regards both performance and feel. In standard trim the Midget is a very satisfactory car. On looking back, after having driven it when its maximum speed was around the 100 mark, it would perhaps be thought slow by those interested only in sheer performance. Yet the ultimate maximum speed is not the only consideration, and in standard form the car recorded a mean maximum speed of 72.5 m.p.h., and this from an engine of only 1-41-litre capacity. On Pool fuel the engine is very smooth and flexible, so that the car is quite suitable for use when frequent stops and slowing down are demanded, as well as for fast open-road cruising.

Stage One

Perhaps the most noticeable increase in performance, yet one that keeps the car still very much an everyday vehicle as opposed to one that is used for special purposes, is the initial tuning modifications from standard to Stage 1. This is a simple tune-up and consists of raising the compression ratio to 8.6 by I (by means of machining -3/32 in off the cylinder head face), polishing out the ports, fitting larger valves and [/SIZE]</TD><TD vAlign=top align=left width="50%">[SIZE=-1]consequently stronger valve springs, and replacing the 1.25in diameter twin S.U. carburetors with 1.5in diameter components, fed by the twin fuel pumps. Modifications to the chassis consisted of lowering the axle ratio from 5.125 to 4.875, to I and fitting an extra set of dampers. Also, purely for the personal comfort of the driver, who was not in favour of driving with the windscreen flat with air temperatures around freezing point, a glass plate type of defroster unit was fitted to the windscreen.
The first impression on driving the car in Stage I form was the very considerable increase in liveliness that it has, and under test conditions this impression was confirmed. The maximum speed was increased by 5 m.p.h. and there was also a marked improvement in the acceleration figures through the gears. Acceleration times in one gear from constant speeds, however, were, generally speaking, longer. Now this fact is interesting as it shows one of the fundamental things about tuning that is sometimes overlooked; that is, as the top end performance is increased, the bottom end power and consequently some of the flexibility also are often lost. For example, if the valve throat diameter is increased to improve the breathing at the top end the gas speed at low engine speeds will he reduced. This means that the pulling power and flexibility at low speeds on top gear will perhaps not be very good, and in consequence more use of the indirect gears must be made. In turn this may result in an increased fuel consumption. This trend can be seen throughout the whole of the tests, and confirms a phrase in the tuning book, " Power costs Money."
Now although there is a very definite gain, in performance this is not obtained without some loss in smoothness. However, it must be remembered that at this stage the car is still running on Pool fuel. During the tests some pinking was noticed, but this can be reduced to a minimum by using the indirect gears and not letting the engine slog away at low [/SIZE]</TD></TR></TBODY></TABLE>

 

<TABLE width="100&#37;"><TBODY><TR><TD vAlign=top align=left width="50%">[SIZE=-1]speed on top gear. The car is quite happy in city traffic generally, yet it should be recorded that on one occasion only, in very dense slow-moving traffic, it did show signs of getting hot. On all other occasions, including fast main road and hilly journeys, as well as during the actual performance testing, no trouble of this kind was experienced. With the extra set of spring dampers fitted the car has a much firmer ride at high speeds at the cost of some increased vibration over rough surfaces at low speed. For Stage 2 the compression ratio is further increased to 9.3 to I by machining a total of 0.125 in off the cylinder head, which is the absolute maximum that can safely be removed. As in Stage 1, large valves are used, and the twin 112-in bore S.U. carburettors were tuned to suit, the 50 per cent alcohol fuel. At this stage the engine develops 69 bh.p. at 5,500 r.p.m. as compared with 54 b.h.p. at 5,200 r.p.m. when in standard form, or 60 bh.p. at 5,600 r.p.m. with the Stage I tuning. Compared with Stage 1, perhaps the most notice- able thing about the behaviour is the very considerable in- crease in smoothness, yet the gain in maximum speed is not nearly as marked for the 9 b.h.p. increase as it is between the standard engine and -Stage I for an increase of only 6 b.h.p. This is, of course, brought about by the shape of the[/SIZE]

[SIZE=-1]power required curve, and shows the effect of wind resistance as the speed is increased. The acceleration figures from a standing start through the gears show an overall improvement; accelerations on one gear from constant speeds are slightly worse. The fuel consumption is considerably increased, but this is not surprising, because of its high alcohol content. It is possible to run in this stage of tune on 80 octane fuel. This would enable the car to be used for normal running in countries where this type of fuel is available. Both Stages 3 and 5 of the tuning are in- tended for competition use only, and will therefore be dealt with together later. Adding a Blower Next, then, we come to Stage 4, which consists of super- charging the engine in standard form, but using the 4.875 to I axle ratio (as fitted in Stages I and 2). In this form the engine is blown at 6 lb per sq in by means of a Shorrock supercharger, which is belt driven from the engine crank- shaft, and for this stage it is fed by a single 1.5 in S.U. carburettor. For test purposes 80 octane lead-free aviation fuel was used, although it is possible to run on 70 octane fuel, at the expense of a slight reduction in output. In the past there has been perhaps a feeling that when a car is supercharged it, at once becomes messy, unreliable, and likely to blow up at the slightest provocation. This may have been true in the past, when some of the problems connected with supercharging were not fully understood, but it certainly does not apply to the Stage 4 M.G. The general improvement in , filling and distribution brought about by the blower results in an overall improve- [/SIZE]</TD><TD vAlign=top align=left width="50%">
[SIZE=-1]ment in performance as regards both maximum speed and acceleration compared with Stage 2. On the other hand, the fact that it does not have such a good bottom end as the standard engine is reflected by the acceleration figures from a constant 10 and 20 m.p.h. on top gear. It must be remembered that the change in axle ratio will affect the result slightly. However, compared with the general improvement in performance this effect is of little moment, as a driver could overcome it by use of the gears, yet it does show what is perhaps the major difficulty in tuning; that is, to obtain an overall increase in power output with-, out losing the bottom end or engine flexibility. In this supercharged form the car is quite suitable for normal road use, but the fuel consumption is, of course, increased as compared with the unblown engine; also, as the oil supply for the supercharger is taken from the engine, the sump must be replenished more frequently than when the engine is unblown. The supercharger is quiet in operation. In fact, it is not until the engine is really starting to rev that the familiar whine is heard at all. No difficulty in starting from cold was experienced. The stages dealt with so far cover tuning suitable for a car that is used to some extent as a normal road vehicle, In the next issue the two remaining stages will be considered that are intended purely for competition work and not suit- able for normal use. General impressions and results will also be discussed. [/SIZE]
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<TABLE width="100&#37;"><TBODY><TR><TD vAlign=top align=left width="50%">[SIZE=+4]S[/SIZE][SIZE=-1]OME of the general problems connected with tuning have been considered, together with results obtained with those stages that are suitable for normal road operation if the correct grade of fuel is available. To complete the picture there remain two further stages which are really suitable only for competition work, although during tests the car was driven on the road in both these conditions for a considerable distance.
At Stage 3 the car has the character and, perhaps, the temperament of a racer. This is not surprising, as the engine now has a compression ratio of 12 to I obtained by using a cylinder head of standard dimensions in conjunction with special pistons. Large diameter valves are, of course, fitted, and the 80 per cent alcohol fuel is metered by twin I 'I'M S.U. carburettors. At this stage starting from cold is best performed with the aid of a rope and a tender car, unless there happens to be a team of strong men available to push. However, once the engine is warm starting can easily be performed with the standard starter motor, and in such [/SIZE]
</TD><TD vAlign=top align=left width="50%">[SIZE=-1]circumstances, during the test, the response was almost instantane'ous. With 78 b.h.p. at 5,750 r.p.m. now available, it is necessary to change the rear axle ratio to 4.55 to I to make effective use of the new-found top end power without over-revving the engine. These modifications produce an increase in maximum speed of 3 m.p.h. compared with Stage 4. They also give a noticeable improvement in the acceleration times from a standing start through the gears, in spite of the change in axle ratio. On the other hand, acceleration times on any one gear do not show any improvement; in' fact, they are, if anything, slightly worse.
The car is very pleasant to drive at this stage provided that the lack of bottom end flexibility compared with that available with the engine in standard form is remembered, and the car driven accordingly. It is also very important to maintain the correct engine temperature, as the cool [/SIZE]
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<TABLE width="100&#37;"><TBODY><TR><TD vAlign=top align=left width="50%"> </TD><TD vAlign=top align=left width="50%">[SIZE=-2]For Stage 3 (l2 to 1 compression ratio) large twin S.U. carburettors are used. These are supplied with fuel by the twin electric fuel pumps mounted on the scuttle, piped so that both pumps supply both carburettors. This is necessary to prevent possible starvation of fuel, as the excessive temperature caused by a weak mixture could produce extreme overheating. [/SIZE]</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD vAlign=top align=left width="50%">[SIZE=-1]running qualities of the alcohol fuel can, in certain circumstances, cause over-cooling, which may result in lumpy running at low speeds, accompanied by some hesitation when the throttle is opened. During this test, which was carried out at an air temperature of 59 deg F, it was found necessary further to blank off the radiator for the acceleration tests in constant gears, although for other tests the single aluminium sheet fitted, as shown in one of the photographs, was entirely satisfactory. Mixture strength is of the utmost importance at this stage, as any weakness could easily cause overheating, which could have very serious results. Under normal conditions, this would not happen, but a temporary starvation could take place if the car were driven with only a very small quantity of fuel in the tank, and fuel movement during rapid cornering, for example, permitted air to enter one of the fuel lines. It is therefore advisable to keep a considerable quantity of fuel in the tank to eliminate this possibility. [/SIZE]

[SIZE=-1]The final test in this group is Stage 5, which consists of the 9.3 to 1 compression ratio engine, supercharged at 6lb per sq in by means of a Shorrock blower. As in Stage 3, the car is fitted with the 4.55 to I rear axle ratio, but oversized tyres are used to give 17 m.p.h. per 1,000 r.p.m engine speed, compared with 16.258 m.p.h. per 1,000 r.p.m for Stage 3 with 5.50-15 in tyres.. With 97 b.h.p. available under the bonnet, the little T.D. really does go like a bomb, [/SIZE]</TD><TD vAlign=top align=left width="50%">[SIZE=-1]and when driven on the road it has been responsible for a number -of puzzled expressions on the faces of drivers in cars that it has passed, and who did not know that the car was tuned. Considering the type of body, which does not cheat the wind as well as some, the maximum speed of 96 m.p.h. (approximately I m.p.h. per b.h.p.), with the hood and side screens in position, is very good. It can be further increased,' to just over the 100 mark if the car is &ted with a full tonneau cover and an aero screen. What it would do with a full streamline body must be left to the imagination, or to Goldie Gardner. Normal racing car drill must be performed as regards plug changing at Stage 5. Often the engine could be started from cold by the normal starter motor, although this was difficult at times and the rowing method had to be used. Starting from hot could easily be performed at all times with the starter. Because of its potential maximum speed this Stage 5 test was carried out in Belgium on the Jabbeke motor road. On the road itself, which is excellently surfaced, the car ran 'very well indeed. However, on some of the smaller roads leading off the main highway the pave is very uneven, and on these surfaces some irregularity in running was noticed, but this stopped again as soon as the car returned [/SIZE]

[SIZE=-1]-to a smooth road. This is interesting, and may have been caused by frothing of the alcohol, the condition being accentuated by the firmness of the suspension when fitted with the additional dampers. Under normal conditions the standard clutch was quite satisfactory in dealing with the much increased power output, yet under the strenuous conditions of the repeated standing start acceleration tests slip was experienced, but only at this stage. There are a number of points that arise from an examina- [/SIZE]</TD></TR></TBODY></TABLE><TABLE width="100%"><TBODY><TR><TD vAlign=top align=left> </TD><TD vAlign=top align=left>[SIZE=-2]An exploded view showing the mechanism of the eccentric vane type supercharger fitted to the M.G. engine. The inlet elbow is arranged to suit the three- bolt flange on the large carburettor used for Stage 5. In the centre of the inlet manifold at the bottom is the super- charger blow-off valve. Lubrication is provided by oil piped from the engine to the union that can be seen behind the rear end-plate of the supercharger[/SIZE]</TD></TR></TBODY></TABLE>

 

<TABLE width="100&#37;"><TBODY><TR><TD vAlign=top align=left width="50%">[SIZE=-1]tion of the results of these tests. First, before any tuning is undertaken at all it must be decided for what purpose the car is required. There is absolutely no point in tuning for its own sake with no ultimate aim in view; also an engine should not be tuned more than is necessary to give the desired result, as this would only unduly stress the components and also increase the fuel bill. Perhaps one of the things that is most noticeable is the way that engine flexibility at the bottom end is lost as the top end power output is increased. This loss, of course, can be compensated for by modifications in driving methods, which will result in an overall gain in performance, but again this will mean in- creased fuel consumption. This is perhaps best illustrated by reference to the graphs showing acceleration times on any one gear, and from rest through the gears. It will be seen that as the tuning proceeds it is possible to make the car go progressively more quickly if the gears are ,used. On the other hand, if the gears are not used the acceleration time from, say, 10 to 30 m.p.h. on top gear will get longer as the tuning proceeds, until at stage 5, for ex- ample, the car tested would not run satisfactorily below a speed of 25 m.p.h. on top gear, with the result that no figures on this gear at a speed below 30 m.p.h. were recorded. However, this was the only stage at which acceleration times for speeds of 70-90 m.p.h. on top gear could be recorded. This again emphasizes the fact that as the power available at the top end is increased by tuning, flexibility at low speeds is reduced. In other words, you cannot have it both ways. of this power being used in overcoming, wind resistance. becomes more and more noticeable. This is illustrated in the graphs showing the m.p.h. per, b.h.p.- engine output.. From these it can be seen that for the standard engine 54 b.h.p. gives a mean maximum speed of 72.5 m.p.h. An increase of 17 b.h.p. (to Stage 4) increases the mean maximum speed by only 9.5 m.p.h. [/SIZE]</TD><TD vAlign=top align=left width="50%">
[SIZE=-1]Again, at Stage 5 the engine develops 97 b.h.p., which represents an increase of 43 over the standard engine; this 43 b.h.p. results in an increase in maximum road speed of 23.5 m.p.h. at the top end, most of this power being used in overcoming wind resistance. That is why for a given body style the increase from the standard to Stage 1, which results in a gain of 5 m.p.h. for 5 b.h.p., is not repeated in the same ratio farther up the range. Stages 2 and 4 give rather similar results, and show two ways of obtaining somewhat similar outputs. Both the high compression ratio engine in Stage 2, and the supercharged standard compression ratio engine of Stage 4, can be driven on the road for normal transport with somewhat similar performance. What, then, should decide which arrangement of tuning should be used? For road operation the differences in output are not sufficiently great to be noticed under normal conditions. In fact, acceleration times through the gears from 0-50 m.p.h. are almost identical. However, above that speed the supercharged engine is at a slight advantage, though it is rather more thirsty than the unblown ver- [/SIZE]</TD></TR></TBODY></TABLE>

 

<TABLE width="100&#37;"><TBODY><TR><TD vAlign=top align=left width="50%">
[SIZE=-1]sion. This is interesting, because Stage 2 is using a 50 per cent alcohol fuel, whereas the supercharged version (Stage 4) runs on 80 octane lead-free aviation spirit.
For competition purposes handicap arrangements would obviously tend to militate against the use of a supercharged engine in any other form than Stage 5, as both Stages 2 and 3 could produce results similar to or better than those from the supercharged version at Stage 4, without penalization [/SIZE]
[SIZE=-2]The left-hand piston is of the standard production type used for Stages, 1, 2, 4 and 5, while on the right is the special piston used for Stage 3, which, in conjunction with a standard cylinder head, gives the compression ratio of x2 to 1. [/SIZE]
[SIZE=-1]from a competition angle. On the other hand, supercharging the engine according to Stage 4 does enable a very considerable increase in power output to be obtained with very little actual modification to the power unit, whereas the other stages require a number of internal modifications. It is therefore quite simple to convert the standard engine to Stage 4 and back to standard conditions again without obtaining a new or modified cylinder head, as would be required for most of the other stages. It must be remembered that modifications to the axle ratio are necessary to get the maximum output from the various stages of tuning.
To enable all stages of tuning to be carried out it is necessary to have at least three cylinder heads and two alternative sets of pistons, as well as three sizes of carburettor and special valve gear, and with these components available the [/SIZE]</TD><TD vAlign=top align=left width="50%">
[SIZE=-2]To obtain a compression ratio Of 9.3 to I (as used in Stage 5) the cylinder head is machined to form a compact combustion chamber. A standard piston is used.[/SIZE]
[SIZE=-1]M.G. can be tuned to suit a very wide number of requirements. The general design and the construction of the power unit as a whole are sufficiently robust to enable these large increases in power output to be obtained without fear of component failure or general lack of reliability. Yet it must be realized that, as the tuning is increased and the components become more highly stressed, so will the rate of wear and tendency towards unreliability be increased. This is only natural and does not reflect in any way on the design; if fact, it speaks very well indeed of the engine design when it is realized just how much power can be extracted from it without modifying the basic components such as the crankshaft or connecting rods, for example.
Obviously, any owner wishing to tune his car will have his own ideas as to how far he wishes to go, but, briefly,' from the tests it would seem that Stage I tuning would suit the requirements of most people who want their Midgets to go rather faster than average without too much of an increase in the fuel bill. Stages 3 and 5 shoulid be reserved for competition work only, while Stages 2 and 4 can be used for either road or competition work at the expense of an increased fuel consumption, and in a car used for road work, only provided that the correct type of fuel is readily available. [/SIZE]
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Is that the Shorrock C75b Supercharger or the larger one?

About 25 years ago I bought all the leftover C75b parts from a guy who Dragraced Brit Bikes.
I was going to Supercharge my Abarth Racecar, but before I got around to doing that they changed the rules on me.
And because after the rulechange the Blower would have put me in a class where I would not have been cometitive, I never got around to using them.
I bet I have enough parts for about 3 complete Blowers, + a bunch of virgin unmachined Cases, Ends, Vanes, etc...

 

very interesting, yes very interesting. but beyond my current abillities. but cool none the less.

 

I've even thought about building a Triumph Bobber, just to have something to hang one of those Blowers on...

 

notice the bonneville picture in the top left.

 

Im about to fire up my "B" in a couple weekends. Fresh engine, Elgine 286 cam, Harland Sharp 1.625 roller rockers, oversize RimFlow valves, 38cc combustion chambes aprox 10:1 comp. port matched, Maniflo intake and exhaust. Aldon Distributer, MSD AL6, TWM ram pipes, 2"exhaust.... The list goes on.

 

Metatshapes...
If you're interested in selling any of the Shorrock parts that you have send me a PM and I'll hook you up with a friend of mine. He's bought a bunch of Shorrock parts and may be interested in yours.

 

but it doesn't say whether or not you primed the oil pump

i would imagine it is going to sound very healthy. what year B are going to stick this enraged lawnmower engine in?

 

Thank you very much for posting those articles. I really appreciate it.

My TD just arrived. I need to get plates for it during lunch today. I took it for a short spin, though, and loved it.

 

the TD looks great, a real nice clean version of mine. I was "researching" and just hit pay dirt. figured that i would throw them up here.

I have been using the TD as my daily for about a month off and on. Get yourself a service manual and follow it religously. I spend my time at 50 - 55, just motoring down the road in no rush.

Congrats again!!

 

the black wheels and beauty rings really help, what tires are on it (radials or bias)?

 

A friend has one or two blowers...

 

i counted a wee more than 2, but not much.

and a TC!

 

Sorry for the poor photo but its the best one I have. This my late father-in-law, Merl Francisco, in his V8-60 powered TD at Palm Springs in (I think) 1955. The car started out stock but the engine blew. A V8-60 was a lot cheaper than the parts to fix the MG engine. As time went by more and more MG parts were replaced with American parts.



Kurt O.

 

That's a great photo and story, Kurt O. Very cool.

FB, the tires are bias ply Goodyears. For now, at least. I think they're going to need to be replaced in order to pass inspection because they look a little dry rotted.

The previous owner bought the car in 1987. Who know how old the tires might be? Curiously, some are 5.60-15s and two are labelled 6.00-15L. Does anyone know the difference? They both measure about 25.5 inches in diameter.

 

tread width I would imagine. when the sunshines again I will put tires on the TD, but I am debating between bias and radials. On an open wheeled car there is less of a debate...but here i am torn.

 

Hey man I say go for it, i have a 74 mg midget body i am working on, wanting to make it an ol skool rod! I am going to be powering it with 2000 cc pinto engine and trans! stout lil engines. I thought about the td too, just probably really hard to find!

 

great photo! the pegasus seams to be a traditional decal, i had always thought of it as a porsche thing (the little bastard).

any more cool pictures hanging around?

Kurt, hope your safe down there in socal.

 

The Pegasus is the Mobil Oil logo.

I'm trying to decide between radials and bias tires for the TD also. The only car I drove with radials was a 68 Buick LeSabre and I hated them.

I'd like a larger diameter tire, but still narrow. The TCs had 29-inch tires, which really fill the fenders. 25.5" ones are part of the reason TDs look so good lowered, I think. (It turns out my TD is already lowered.)

 

you know I was thinking that it sat a little lower.

try this site for tires, i don't know about the prices.

http://www.rogerkrausracing.com/tires.shtml