Gimmickry?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
Battling against the advance of an aerodynamically-styled opposition on its home market, GM is searching every technical avenue for a more profitable future. One of the weapons in that fight to escape a public reputation for stodge is motor sport.
The Anglo-American Ilmor Chevrolet racing V8, created in Northampton but most certainly not by Cosworth, has already established its practice pace and ability to win against the ubiquitous Cosworth DFX in the CART Indycar Championship. However, GM also needed to persuade the public that it was staying on the technical pace of developments for the road. Thus projects such as the $52 million Saginaw Vanguard computerised factory and that GM division’s promising work upon four-wheel steering (4WS).
Saginaw is not just the provider of General Motors steering systems and an increasing number of front-drive transaxles. Some years ago it was set the task of achieving profits as a supplier to those outside the GM colossus. Ironically one of Ford America’s most effective assaults on GM sales has come via the GM Saginaw-equipped Ford Taurus/Sable saloon series.
To demonstrate its prowess in steering and related fields, inside and outside GM, Saginaw recently took the unusual step of bringing some of its prototypes to Britain on a flying visit— unusual because it did not then carry on into Europe or the motor show circuit to extensively promote some intriguing work which could put the Americans on par with the Japanese.
For Saginaw came to Hendon, site of just one of its twenty worldwide factories, with one of three 4WS steering layouts it is currently investigating, installed on a Pontiac Fiero mid-engined two-seater.
Avoiding “technology for technology’s sake” is the avowed intention of GM’s Vanguard factory, and Saginaw emphasised that there are no production plans for four-wheel steering “in the near term”, whereas Japanese companies such as Honda (see page 1004) have offered 4WS to their home market since spring of this year.
GM’s prototype 4WS has been based on mechanical, hydraulic and electronic operation for a wide variety of vehicles; it is safe to understand that Lotus will not be in ignorance of Saginaw’s work and that 4WS may well be included on the Nineties’ Etna V8, senior Lotus management apparently delighted with the extra high-speed stability conferred.
Saginaw research 4WS vehicles included leisure vans, limousines and the 165.1-inch Fiero coupe flown over for assessment.
The test Pontiac was equipped with an electronic system, the layout of which is shown in the accompanying diagram. That control module contains the ubiquitous microprocessor which analyses incoming information, from speed to front- and rear-wheel angles. The processor reacts with a series of rapid instructions which save the whole plot from disappearing up its own exhausts.
The Fiero SE comes with a V6 which is not particularly, powerful for its 2.8-litre capacity, being 15 bhp down on Ford of Europe’s similar-capacity V6. However it fed enough torque to the automatic transmission to stress the Eagle NCT tyres (205/60 front, 215/60 rear) around the 5-55 mph urban layout of Hendon. You need little power to immediately feel the benefits of 4WS . . .
As the LHD machine moved away from the kerb I was immediately conscious of the rear wheels counter-steering to my lefthand lock. There was no lurch, but we left the kerbside behind far more rapidly than usual.
In this prototype a number of steering layouts were possible and my Saginaw co-driver had left us in automatic, which meant the front and rear wheels turned in opposite directions until 25 mph was reached. Then the control module instructed the position sensor to reduce what they call the “Negative Phase Mode”. As speed rose the rear wheels begun to follow the path of the fronts.
This was fascinating, because we could click back to a conventional straight-ahead path for the rears and then immediately compare that with the 4WS effect. With the rear wheels locked, it felt as if we were fighting against the car’s natural turning desires, whereas with mild angles of rear-wheel steer the Pontiac flowed naturally into 50 mph curves.
I did not expect to be impressed above parking speeds. Yet the extra stability and the lack of scrub from the rear was almost as convincing in providing another motoring dimension as my first experience of performance 4WD.
For parking manoeuvres, where the contrary use of the rears promised an obvious reduction in turning circle (from 39ft to 31ft at its best), the extra manoeuvrability was appreciated. Yet it was the extra confidence it gave around tight mini-roundabouts, and in tackling seemingly impossible street intersections, which left the stronger memory. JW