After a relatively disappointing 1987, when the McLaren-TAG Porsche (850 bhp in race and 1060 bhp in qualification) lost out nine times to the dominant Honda-powered Williams, twice to Lotus with their Honda engines, and twice in the latter stages to Ferrari, taking only three wins. McLaren secured the 1.5L V6 Honda turbo engines, one of the most powerful in F1 at the time. With the engines coming at the expense of Williams, a strong 1988 was possible. 1988 was due to be the last year for the turbo engines before they were banned, so most teams were making a concerted effort to establish themselves with naturally aspirated cars. Nichols and Murray went ahead with the design of the car on a purely turbo engined basis, which put the team at a distinct advantage over their rivals.
The lowline chassis layout was pioneered in 1986 when Murray was at Brabham. The idea being that a low car with a reduced front area of about 30% would be more aerodynamically efficient and allow more air to pass over the rear wing causing more downforce to be produced, but without excessive drag. In theory this sounded great, with cornering speeds unaffected and straight line speeds improved as less air needed to be moved by the car. In practice though, the slanted straight 4 BMW engine used in the Brabham proved troublesome in this layout with fuel starvation problems, oil starvation, and engine installation issues plaguing the BT55. While the BT55 was generally among the quickest cars in a straight line, the car suffered a lack of downforce in the corners and the oil starvation problems, added to the BMW's legendary turbo lag (often around 2 seconds), saw to it that acceleration was severely lacking compared to its rivals. Overall the cars problems made the BT55 generally uncompetitive on all but the faster circuits where top speed often counted for more than acceleration. The 80° Honda V6 engine however was smaller and had a lower centre of gravity than its BMW counterpart, so it was ideal for the low-down chassis layout (Murray had stated in an interview during 1986 about the lowline concept that it would work much better with a V6 engine). With this in mind, Murray's original design for the BT55 was revised and McLaren went ahead with his plan.
The lowline concept was not completely new to McLaren however. Murray had joined the team in 1987 where he played a small hand in helping Nichols refine his design for the MP4/4's predecessor, the MP4/3, which was completely different aerodynamically to the bulbous looking MP4/2C it had replaced. With the 90° TAG-Porsche V6 at their disposal, and new rules reducing fuel tank size from 220 litres to 195 litres, McLaren proved that the lowline concept did work, with redesigned side pods also getting the treatment (only the nose section remained as a visual reminder of the MP4/2C). The improved aerodynamics helping the Prost and Stefan Johansson to be closer to the more powerful Honda powered cars than they would have been with the older MP4/2 design, although the team was hampered by unreliability which had crept into the TAG engines. The team was able to build on this and, with the smaller Honda V6, and a further reduction in fuel tank size from 195 to 150 litres, the sleek looking MP4/4 was produced and first appeared early in 1988.
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