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  April 1973 Road and Track

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Back to Basics

Track testing nine Showroom Stock Sports Cars, the entire field
in SCCA newest class. Not a fair group, exactly,
but certainly sporting.

    THIS COMPARISON TEST is not the ordinary sort of comparison test. In the normal course of events the staff selects a group of comparable cars—economy sedans, say, or sporting GTs on the basis of roughly equal size, price and intent. We put them through a standard series of tests and vote on which car performs normal transportation and entertainment functions best.
    We are not going to do that here. This group of cars is a big one and it varies widely indeed when considered on the basis of price or even what the maker intended the car to be. The tests to which the cars were submitted are not the usual tests; some were invented for this occasion. And we did not decide which cars to have in the group.
    The Sports Car Club of America did that. Goaded by members who believe that a sports car club should have events for road-going sports cars, the SCCA has created a new racing class: Showroom Stock Sports Cars. The sports cars will run with the Showroom Stock Sedans that began racing in SCCA last year and will compete under the same basic rules, their essence being that the cars must have full safety equipment (roll bars, safety harnesses, fire extinguishers, etc) but otherwise be raced exactly as they come from the dealer’s showroom. Not even optional wheels or gear ratios are allowed. As an equalization factor all cars may use 165-section radial tires,

any DOT-approved brand but in the diameter that fits the stock wheels be they 13-, 14-, or 15-inch. Having created the class, the SCCA filled it with a selection of models, which must be either 1972 or 1973 model year. The eligible cars are: Fiat 124 Sport Spider; MGB; MGB-GT; MG Midget; Opel GT 1900; VW-Porsche9l4 1.7; Triumph GT6; Triumph Spitfire 1500, and VW Karmann Ghia.
    Before we discuss inequities or cars which should be on the list but aren’t, we must understand that the intent of the class is to have fun, to provide racing for club members in a wide variety of cars. The SCCA doesn’t mind one bit that all the major sports car makers have at least one model on the list. And this class is not supposed to prove anything about the merits of the cars.
    The original plan was to have a $3000 price ceiling, but that failed because there weren’t enough cars on the list. The limit was raised to $4000—with special dispensation for the 914—while the less expensive cars were retained. If there are too many imbalances the SCCA retains the right to delete models. Or if another model comes to mind—say the Saab Sonett—it can be added to the list.
    So this is not an equal group. Some of these cars are going to be faster than others. With that in mind, perhaps we should agree now that there will be no proclamation involving the
winning car.

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     To say that a modern, expensive sports car with a large engine can outrace an older, cheaper sports car with a smaller engine wouldn’t require tests anyway.
    What we will look at is the particulars: what each car will do on a race track and why it does it. When we compare cars that way, we’ll learn something about both the cars and racing.
    One more item about equality. Last August R&T tested nine brands of radial tire. Tires are not the same; a Datsun 240Z would corner at 0.745g on Michelins and O.7l3g on Yokohamas, and would stop from 60 mph in 138 ft on Pirellis and 151 ft on Bridgestones. Tires make a difference and there’s no sense comparing a Fiat on Michelins to an MG on Dunlops. This is a car test. To eliminate the tire factor, then, we obtained a spare set of wheels for each of the nine cars and fitted each wheel with a Semperit STT M 401 I65SR, in 13, 14 or 15-in. diameter. The Semperits performed very well in the August tire tests, so we knew they’d make each car do its best while ensuring that we were testing only the car.

The Tests

BECAUSE THE cars in the group were picked by the SCCA to be raced against each other, the tests involved here are strictly for track purposes. No consideration was given to daily use; no worry about trunk space, door width or miles per gallon. We wanted to see what the cars would do on the track.
    The first checks were preliminary, part of our normal test procedure, measuring acceleration from rest to set speeds and set distances. That’s the standard way cars are compared, with 0-60 mph and the standing quarter-mile times and so forth, and we thought we should have these figures for reference.
    But those standard figures mean little on a track. SCCA races are begun with rolling starts, usually at 40 mph or more, for safety reasons. A racing car never makes a 0-60 run unless it’s coming out of the pits or the weeds. What matters on the track is acceleration out of corners and down the straights.
    To measure that, we went to Riverside International Raceway, specifically to the exit of turn 7A. This is a slow right-hander, the second half of an ess, leading onto the back straightaway. The speed out of this turn naturally varies with the cornering capability of the car—a point we’ll cover next—but for a stock sports car the average speed past the exit is about 40 mph. Each car was taken through the turn in 2nd gear as fast as it would go and then accelerated through the gears to the markers warning of the end of the straight. Each car was timed from the exit both to a bridge at midpoint and to the

markers. We reasoned that this, the amount of time it takes to cover the straight, means more than times from rest to speed.
    Cornering power was measured two ways. First was our standard skidpad, timing the cars around a circle of 100-ft radius with the tires set at pressures which our experimentation showed would improve cornering. That’s what anybody racing a car would do first, especially if the rules forbid doing anything else.
    Next we built a “square circle.” This is a racing technique. On the skidpad were placed four corners, each marked with a pylon on the inside and two pylons on the outside, like the gates on a slalom course. Steady-state cornering power is a valid test of a car and certainly useful for comparisons, but driving through a corner is a question of transients. A car must be driven into a turn, around it and out of it, passing from straight ahead to the limit of lateral adhesion and back to straight ahead. The corners were located close together, so that a car’s acceleration and brakes wouldn’t be a factor: No sooner was a car pointed straight again than it was time for the next turn. Each car was driven around the square as fast as possible and timed. The round skidpad measures a car’s steady lateral capability; the square circle measures speed through a real-world corner.
    The braking test was also based on the demands of racing. Full stops are not supposed to be required, but braking from high speed to cornering speed in the shortest possible distance is needed. The less distance needed to stop, the more distance that can be covered at speed.
    Each car was accelerated to 80 mph, then braked at the maximum usable deceleration (meaning with good steering control) down to 40 mph, with our fifth wheel and electronic counter recording the distance covered while the brakes were on.
    And there was a test for practical top speed. There aren’t many race tracks with enough space for cars of even this moderate power to reach their true maximums. Some tracks have longer straights than other tracks, though. and here top speed is important; so the nine cars were taken onto Riverside’s far corner, turn 8, and given a running start down the long, long hill past the kink and onto the drag strip, surely as long a run as these cars will ever have in competition.
    The final and ultimate test was timed laps around a circuit. By this time we knew which cars were quickest off the mark and to top speed, which cars went round corners best and which stopped quickest. So we laid out a course, using Riverside’s turns 7 and 8 and the two straights that connect them. A loop,

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73 ghia
mostly, with a fast sweeping turn leading into a decreasing- radius right that exits into a banked left, down the hill into a sharp right, a left and another right, then uphill to the sweeper. All the elements, then, that a car would face on any track.    We also had a variety of drivers: those staff members who either drive in races or have graduated from driver’s school or both, plus contributors and former contributors with equal qualifications. One of the latter drivers even wins races.

  The Results

BEFORE THE race, though, let’s go back to the first of the series of tests. In Fig. 2 are listed the results of the normal times-to-speed and distance tests.
    In daily driving as on the track, times to distance mean more than times to speed. In that light the cars can be ranked on the basis of their quarter-mile times and we found that acceleration

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from rest is a function of power-to-weight modified by gearing: we have the Fiat, the most powerful car in the class, crossing the line first; then come the 914, the MGB, the GT6, the Opel, etc. The GT6’s relatively tall final drive gears put it behind the MGB despite the MG’s greater weight. The gap is not as wide as the spread in power-to-weight would lead one to expect, however. The Ghia has half the power of the Fiat and is the slowest of the nine, but even so it lags by only 2 sec at the finish. On the basis of a normal road test, we’d have to say that the difference in performance is not extreme. But let’s move to the track. In Fig. 3 we have the times from turn 7A to the shut-off markers at the end of the straight. There are three times for each car;

 the total from corner to marker, from the corner to the bridge, and from the bridge to the marker. Interestingly, the order has changed. The lightweight Opel has moved front fifth place at the drags to first past the marker. The GT6 is as close behind the Opel here as the Opel was behind the GT6 from a standing start. And the Fiat has moved back to third. Yet the power and weight hasn’t changed at all. But the use of gears and engine speeds for this test is different. The Opel has a tall final drive. Note that it’s especially quick from the corner to the bridge: it came through the corner at peak torque in second gear, with plenty of space left on the tachometer, and was peaking in third as it reached the shut-off marker. Thus it didn’t have to be dropped into a relatively dead top gear for the stretch.

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73 ghia

Same for the GT6, except that its gearing is taller still, meaning that the 0T6 is still pulling strongly when it goes past the marker—so strongly that it nearly closes the gap on the Opel.
    This works both ways. The Fiat is wound tight in second at the corner and uses 3rd and 4th gears for this distance. The MOB only needs 2nd and 3rd but it can’t match the Fiat’s power, the MGB-GT is heavier still, and so on. The 914 particularly suffers here as it comes with an overdrive 5th for the open road and a very low first gear for city starts. From a standing start it gets a great leap forward and a good elapsed time for the quarter mile. But once into the upper gears, the lack of power and engine speed hurts it.
    And the Ghia Pure lack of power. For the first segment of this test it’s merely slow, lagging behind the others but not by much. At the bridge, though, the Ghia is shifted into top gear and acceleration becomes merely perceptible as the gap widens.
  What all this means is that if all nine cars came through turn 7A in a pack three wide and three deep, by the end of the straight they would no longer be a pack. They would be a string, with 6 sec between first and last.
  But, you may think here, what about cornering power? Surely these cars must vary in cornering power and this must influence the speed down the straight. Faster in, faster out, so to speak

Yes. But. In Fig. 4 we have the skidpad figures, taken (as mentioned) with tire pressures adjusted to give each car its maximum grip. Our first finding in this test was that the cars weren’t all that far apart, not the way one would expect.
    We knew from driving the cars on the road that the MGs were harshly sprung. that the Fiat was soft and comfortable, that the 914 seemed both firm and comfortable. We would have projected from theory and racing practice that the 914 would have been very good. And if we listened to folklore we would have expected the Triumphs with their swing axles and the Ghia with its leaning front suspension to be both tricky and slow.
    But it didn’t work out this way. The MOB—live axle, leaf springs, coal-cart suspension and all—went around the fastest. Then came the soft Fiat. The sophisticated 914 tied with the Spitfire, Midget and Opel. The extra weight of the MGB-GT counts against it and the Ghia is at the back again. In its favor, though, was the security with which the Ghia reached its maximum. The rear wheels jacked up a bit but the old-style front suspension ensures that Ghia’s steady-state cornering is done in an attitude of understeer, even to the inside front wheel lifting off the ground.
    As an adjunctive lesson, we learned that some cars can gain more from adjusted tire pressures than others. The Fiat, the MGB-GT, the MOB and the 914 gained the most. But the Midget gained only a tiny bit and the Spitfire didn’t gain at all. More pressure simply made it skitter over the high spots.
    But just driving around corners isn’t our main interest here. In the squared circle, remember, we put each car into, through and out of four turns.

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73 ghia

    The results of that are in Fig. 5. For once we don’t have a new name at the top of the list: The MGB was best here, as it was going around the normal circle. But the MGB-GT tied with it. That’s a surprise, the explanation for which is buried ‘way back in the specification table. The MGB-GT has more weight on the rear wheels, is in fact tail-heavy whereas the MGB has a forward weight bias. In this test, then, a car which can be coaxed into or naturally tends to oversteer does well. In a tight turn, the understeering car must be forced around, front wheels scrubbing off speed. The oversteering or neutral car can be pointed, wagged and straightened out. The 914 has gained on cars which it formerly only equaled. And look at the Ghia—better than both Triumphs and the Fiat! The latter car looked especially poor in this test. It understeers and rolls and does not do well in sharp changes of direction, despite its good showing on the normal circle.
    The 914 has the mid-engine’s low polar moment of inertia as well as what we judged to be the best and most precise steering. With enough power at a high enough speed, the tail can be provoked into a slide. And the front end darts toward
the inside of a turn the instant the throttle is closed. So the car could be hurled about with great gusto. We let it drift wide under power into the turn, whipping it sideways by lifting off and flinging the tail around with more power as the inside front wheel bounced off the ground. It all felt great and looked spectacular, but all that flamboyant flinging about only scrubbed off speed and tire tread. The best times for the 914 came with the car driven carefully and tidily.

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73 ghia

The Opel displayed a chronic problem: in a tight turn the inside rear wheel lifts, the engine races, the tire spins and the car just sits there until the speed and the wheel both drop. The Opel didn’t come out of the turns fast, then, because it couldn’t power out.
    Only in the braking test did the cars perform according to expectations. Fig. 6 shows the 914 best, slowing from speed in the shortest distance. That’s what you’d expect from four disc brakes and a slight rearward weight bias.
    The Opel, MGB-GT and Fiat were as easy to control as the 914 was but didn’t have the stopping power. The MOB’s weight distribution hurt it more than its lighter weight helped it. The GT6 swerved under maximum pressure and the Spitfire and Ghia both tended to lock up wheels if pushed.
    And we discovered an interesting thing about which perhaps we shouldn’t tell you. The Fiat has vacuum assisted brakes, too much assisted in our opinion. This makes controlling the brakes difficult, so one of our guest drivers popped under the hood and pinched the vacuum line shut. What the SCCA technical inspectors would say about this we don’t know. But it did make the Fiat’s braking easier to modulate.
    This test had the widest variation among the cars. If we can assume that the cars are all bunched up on the straight, heading fast for a slow corner, then the car which needs the longest distance to slow down must be the first one to get off the power and onto the brakes. From the bunch, then, the Ghia drops out first, then the Spitfire, then the Midget, and so on.
    This is compounded in that the cars don’t slow down from the same speed. As we’ve seen from the acceleration figures, they won’t reach top speed at the same time. And as we see in Fig. 7, the top speeds reached by a downhill run from the far corner of the track vary from car to car. The Fiat, for example, hit 5500 rpm in 5th, below the redline. And the 914 never needed 5th at all. At the other end, the Spitfire, Midget and Ghia are going as fast as they can go, albeit not very fast.
    Now we have all the measured data on acceleration, handling and braking. We know which cars are the quickest from rest and from slow corners, which cars go around corners and through turns better than their competition, which cars stop shortest and which go fastest on the long straight. For a bringing-together sort of test, we wanted to find out just how important each of these factors is: is cornering power as important as engine power, does good braking make up for lack of speed?
    So we arrive at Fig. 8, the lap times for our road course. The times shown are the result of many laps by several drivers, each one of whom was doing his best in whatever car he had at the time. These figures don’t quite speak for themselves.

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    All they tell you is which cars went around the Circuit faster than which others, Why and how come from subjective assessments from the drivers, given in the order of increasing lap times.

Triumph GT6—does everything well. Plenty of power, gearing that lets the power be used in these conditions and good brakes. The car’s natural understeer brings it around the fast sections under control, and the power lets the driver fling the car around the tight turns.

Opel GT—has power, like the Opel sedans that overwhelmed the Showroom Stock class last year. And it corners and brakes fairly well. What hurt the Opel GT was the lifting inside wheel. The engine couldn’t be used fully until the car was pointed straight ahead and cruising through the turns in 3rd gear was as quick as sliding and spinning in 2nd.

VW-Porsche 914—is listed first in a tie with the MGB because the fastest driver in the group said that if he just had enough time to figure out how the 914 would go best he could beat the MOB and the GT6 and Opel. You don’t get to the winner’s circle saying “if’ but if the handling had been more flexible or easier to learn, then maybe the 914 could have made up for its lack of power. The 914 was a bit of a disappointment. MGB—has more than tradition going for it. It feels harsh and clumsy but doesn’t look that way on the clocks. The MOB’s secret of success is that a driver can use everything the car has. Fiat 124—is perhaps the best of the boulevard racers. It has a lovely engine, a lot of power and soft suspension. It under- steers, but the Fiat was in fact the only car to spin during the test. We learned that the Fiat went best when driven gently around the fast corners and wound to redline on the straights. MGB-GT—take everything said about the MOB and add weight. The good behavior through tight turns is caused by the same heavy tail that makes the coupe a handful in the fast turns. Now we know why all the MOBs in production racing are convertibles.

Spitfire—lap times aren’t everything. The Spitfire is better balanced than the GT6, and it’s more fun.

Excellent throttle response, so while the Car’s attitude varies with power, the power can be properly controlled. The Spitfire just lacks speed. It’s deceptive, for though the Fiat felt slower than it was, when our drivers climbed out of the Spitfire they went right to the timers expecting to have set a record or two. They didn’t, but they enjoyed trying.

MG Midget—won nobody’s heart. The lack of speed was expected but the stiff and vague steering, the roll oversteer, the mushy front end and the general feeling of cramped obsolescence were things we had forgotten. The Midget won’t win races because it doesn’t go fast.

Karmann Ghia—even slower than the Midget, but at least more fun. Or maybe it’s just the underdog aspect. Either way the Ghia has a good ride and proper steering, and it can be driven on the ragged edge without incident and with drama: what fun to watch it lift its inside front wheel just like a Porsche 9llS! The Ghia is out of contention here. It won’t win, but neither will it be disgraced.

    What have we proved? In terms of values, in deciding which performance factors are most important on the track, the deciding factor seems to be power. Power alone won’t do it: witness the Fiat. But when we check the results and find that the two quickest cars down the straightaway finished one-two in lap times, with the best-handling MGB and best-braking 914 tied for third place, we are forced to conclude that getting from corner to corner quickest will do more for a car than getting through corners will.
    Well, what of it? We already knew that the SCCA organizes production sports car racing to provide an equal chance for different makes and that Showroom Stock Sports Car racing is supposed to be for the man who wants to race his car, win or not.
    For those who must win in Showroom Stock, the GT6 is most likely to do it. For those who can afford a dual-purpose car and like to be comfortable going to and from the track, the Fiat or the 914. For fun, the Spitfire. And to prove that VW does make a sports car, the Ghia.

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