The Lotus 98T was a development of the Lotus 97T of 1985. Of the four chassis built three were assigned to Ayrton Senna, now in his second year with Team Lotus, and one to team mate Johnny Dumfries. Designed by Gerard Ducarouge and Martin Ogilvie the chassis featured a lower monocoque than the 97T as a result of a regulation change stipulating a reduction in fuel capacity to 195 litres. The powertrain consisted of the new Renault EF15bis turbo V6 engine driving through a Hewland gearbox. The EF15bis was to appear in two forms, the standard engine and the "D.P." engine which featured pneumatic valve springs for the first time. At the end of the season Renault introduced the revised EF15C which in addition to the D.P. valve gear also boasted common rail fuel injection and much revised water cooling through the cylinder head reducing the likelihood of pre-ignition (detonation). Power figures for this period of F1 history are largely speculative as most engine manufactures freely admitted that their test beds would not have a sufficient power rating to measure the 1.5 litre turbos output at above 4 bar boost. It is generally accepted that the Renault EF15 produced between 1,200 bhp (890 kW) and 1,300 bhp (970 kW) at 5.5bar boost. The gearbox came in two variants, a conventional five speed and a new six speed. The six speed was very much a development gearbox and was largely unreliable. While Senna opted to run only with the five speed, Dumfries was tasked with testing the six speed. Both gearboxes featured Hewland internals within a Lotus designed casing. Other notable innovation of the 98T included a two stage ride height adjustment, water injection through the intercoolers, an early form of barge board (also present on the 97T) and an advanced (for the time) fuel consumption micro computer. During the 1986 Formula One season the Formula One paddock was very much alive with speculation as to the legality of the Lotus 98T. The increasing rumours prompted Peter Warr, then Lotus team manager, to issue a press statement calling for the rumours to stop or for the teams to officially protest the car. No protest was lodged.

Main unit processes all parameter inputs, determines proper fuel injector and ignition timing, outputs injector and IAC drive directly and controls remote ignition driver. Operates 8 injectors on a 4 cylinder engine to provide a good idle quality and plenty of fuel flow while under boost. I am using 240 cc/min injectors near valves and 450 cc/min injectors up high in the manifold. CPU is a Parallax Propeller which features 8 cores. Really a nice piece. Most code was written in Parallax's Spin language. Only the serial interfaces required assembly code. I actually started with Parallax's free full-duplex object and extended it to handle two full-duplex interfaces in a single core. Fuel algorithm loops at > 100 Hz while clocking CPU at 24.576 MHz. CPU can be clocked at a faster rate (80 MHz) but I decided to be conservative since I am operating a commercial temp range IC in an automotive environment. I created all of the fuel and timing algorithms. Engine runs extremely well. Driveability is excellent. The beauty of making my own ECU is that I can tweak the algorithms or add new features whenever I want. Functions performed by the various algorithms include the following: Start fuel control Post start enrichment Run fuel control vs rpm and MAP Engine temperature compensation Air temperature compensation Throttle opening enrichment and timing advance Closed loop idle speed control (IAC drive) Closed loop Lambda at idle Timing control vs rpm and MAP Redline, launch and shift RPM limiters using fuel cut Runaway boost limiter using fuel cut (actual boost control is pneumatic) Realtime display of selected parameters User input of control parameters and tables with nonvolatile storage of changes Data logging Data download to external computer via serial interface Control parameter and table download to external computer via serial interface Chassis is machined from 6061-T6 aluminum alloy. Made it fit some remnants I had bought.