Tuned Car Test A Fleeter Fiat X1/9

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More power and more fun from Radbourne’s 1,600-c.c. conversion

Based on a sophisticated mid-engine layout, mated to a 2,000 lb. plus 2-seater body, the Fiat X1/9 is an obvious candidate for the “bigger engine is better” philosophy. The baby Fiat’s superb road manners and excellent braking make it an obvious candidate for more power, coupled preferably to a little more torque to carry a body which is certainly not a flyweight by sporting 1,300 c.c. standards.

Looking back to last year’s issues, you will see the car we tried for this tuned car test was an old friend. Yes, it is the same r.h.d. demonstrator we tried from Radbourne, but for the last 7,000 miles it has been running around with 1.6-litres instead of the production 1.3-litres. The results so impressed the Anstead brothers at Radbourne that they decided to let us have a go at the car, even though they are not ready to sell such devices at present.

Before we turn to specifics it is as well to remember two useful points. First Radbourne have been selling X1/9s for some considerable time in this country (our test of the Radbourne-converted r.h.d. car last year was well in advance of the official Fiat launch in the UK) and secondly that the little 1,300 c.c. X1/9 costs £3,298 in Britain now. The work on the car that we tested would have retailed at £700 additionally on the price of a production X1/9. The Ansteads feel this is too much, and they are currently working with British suppliers to try and bring the conversion beneath the £500 mark and ensure much better parts availability/pricing.

What has been done? Basically Italian speed equipment manufacturers have provided a new long-throw steel crankshaft and pistons, while the Ansteads had the normal Fiat iron block bored an extra 2 mm. This makes the 1600 engine 88 mm., by 65.5 mm. stroke, where the normal engine is massively oversquare at 86 mm. bore by 55.5 mm. stroke. This adds up to 1,593 c.c. where once there was 1,290 c.c.

The aluminium cylinder head is unmodified since Geoff Anstend built up the larger engine himself, but it carries a mild £48 Abarth higher lift camshaft in the standard overhead position. The change in pistons has upped the c.r., which now equates to 10.5 to 1, though the alloy head allows it to run on four-star fuel with the same happiness as the normal CM’ dieests the came grade on an 8.9-to-1 c.r.

Although the exterior maniolding is all the same as before, a large Weber carburetter, of the usual downdraught twin-choke type, has been installed. From the Lancia Beta range, the 34 mm. choke DMTR carburetter replaces the normal 32 mm. twinchoke.

The only other significant change, especially when you see how good the acceleration times are, despite its adoption, is in the Radbourne 1600’s final drive ratio of 3.77 to 1 instead of the normal 4.076 to 1. This is a thoroughly worthwhile move which increases the rather “short” gear speeds and improves the high-speed cruising manners usefully into the bargain. The sheer benefit of a few extra cubic inches can he seen from the fact that the standard X1/9 takes a painful 13 1/2 sec. to accelerate front 50-70 m.p.h. in top gear, the 1600 needs only 8.7 sec. This corresponds to within fractions of a second of the time consumed by the standard X1/9 when you drop it back to third and accelerate from 50-70 m.p.h., illustrating the top gear advantage of the bigger engine beautifully.

With bigger 5 1/2J alloy wheels and 165/70 Dunlop tyres, this X1/9 seemed to stop even better than the production car, but nothing has been done on the chassis or braking side at all, the weight distribution remaining the same with only 40% on the front tyres.

Only by the occasional in-traffic acceleration flat spot does the Radbourne X1/9 betray that anything has gone on in the engine bay at all. In fact some of the production cars are worse in my experience of three X1/9s, but the cause is different. Apparently the Abarth camshaft is reckoned to be at the root of these hiccups, though the general driving manners, and smooth power delivery from upward of 1,500 r.p.m. in top suggest otherwise.

The strong point about this X1/9 is the way it combines small sports car dimensions with very easy engine response to allow exceptionally swift progress in traffic. The acceleration is not that startling by 1600 standards—it’s about the sort of thing you’d expect front a VW Scirocco, or a Lancia Beta Coupe 1600—but in such a small package with such excellent handling, it’s much, much more fun. This applies especially if you are blessed with one of Britain’s imitation heatwaves, and the car was actually not driven, or tested at the track, with the top on.

The roof removed, 7,000 r.p.m. safely at your disposal, and a clear road, are not essential to enjoy this car. No, it has too much town nippiness for open roads to be a pre-requisite of ownership—but we were lucky to enjoy motoring in this manner for much of the test. Under such conditions you notice extra power, particularly in slower corners, where the Radbourne X1/9 whips up toward the exit of a corner much faster than before, probably pulling one gear up as well, because of the extra torque. The tail will slide in the dry under hard second gear use, but as before the Fiat rack and pinion steering is more than a match for any waywardness to be cured enjoyably and safely.

Another big difference is that motorway gradients can be tackled with little loss of speed, and this ability to climb hills without changing down cuts down the awareness of that chasm between third and fourth. Without the roof 80 m.p.h. is fast enough for enjoyment and reasonable progress to be made, though the counter can be pushed to read a little over 6,000 r.p.m., corresponding to 108 m.p.h. as a flat road maximum.

In the gears the final drive has added the odd three or four miles an hour, so that at 7,000 r.p.m. just 34 m.p.h. is on in 1st, 53 m.p.h. in 2nd and a more useful 80 m.p.h. in 3rd. As before, the engine noise level increases pretty sharply over 5,000 r.p.m. in the gears, but there is only a tingle of vibration when reaching for 6,500 plus in the gears.

Oil consumption was commendable by its absence, while average fuel figures were in the 22-23 m.p.g. bracket, the result of using full throttle more often than normal, for that procedure smoothed out progress through the engine’s hiccup: besides which it was a lot of fun!

The remarkable Fiat engine seems unworried by the increase in capacity. If anything it is overcooled, running just over 120 degrees in Summer conditions and only rarely requiring the services of the electric fan. Oil pressure was just below 55 lb. sq. in., unless you had really been trying in top for a while, when the green pointer might just have swung over that figure.

Snags? They are really potential rather than actual, for I enjoyed every minute at the wheel of this car. I must heartily endorse C.R.’s recent comments about the X1/9 as a modern sports car, adding that the 1,600 .c.c. job just makes it a little more useful all round, and quite a little liver across country.

Nevertheless Radbourne are aware they could have trouble with the gearbox synchromesh in hard use: third started to baulk towards the end of our test session, though it had not been a problem in a very brisk week. I have probably made the engine hit spot sound worse than it is : an irritant, which ought in be quite easily solved, rather than the kind of vicious manners in traffic that put you right off driving the car.

I hope Radbourne are able to sell such conversions. It they add their own warranty, it can make a nice little sports into a very nice little sports car, worthy enough to put a grin on any driver’s face.—J.W.

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