'Mountain' enhanced boost chips for the Elan

Introduction

Kilimanjaro - crater ridgeMy interest in tinkering with the Elan's engine management programming started back when I wrote ElanScan. Understanding the ALDL (assembly line diagnostic link) required much raking around websites with information concerning the modification of GM P4 ECUs. It is possible to download the contents of the Elan's 32kb PROM 63 bytes at a time via an ALDL command and so an algorithm was written into ElanScan to do this.

After lot of work reverse engineering the PROM the boost control code was been identified and the ability to reprogram the boost control system acquired.

Boost from the turbo is limited by a wastegate, when this is open exhaust gases bypass the turbo so drive is removed from it. The wastegate is opened by an actuator that operates when the pressure in the output side of the turbo exceeds around 0.5bar (curiously a bit higher than the 0.4bar quoted in the Lotus manuals). In the Elan the ECU can actively control the boost above the passive limit, up to 0.65 in factory configuration. The extra boost is gained by limiting the pressure the wastegate actuator receives. A solenoid valve is installed in the wastegate acuator's feed line and by varying the proportion of time the valve is open (the duty cycle) the size of the leak, and therefore the boost achieved, can be varied. The ECU looks up a target boost, the value of which depends on engine RPM and throttle opening and varies the duty cycle of the solenoid valve to meet the target.

In this upgrade the tables have been modified to allow higher boost values to be employed – up to 0.9 bar. Two boost maps are offered here.

The Chips

A few characteristics of the chip are different to the original. First and foremost the boost targets are higher.
Boost map comparison

The chip's primary characteristics are listed here:

The ECU solution leaves all the safety features enabled:

Why not use a cheap MBC (with optional FCD) or an Expensive BBR kit (MBC+BBR)?

An MBC puts a fixed leak in the air line to the wastegate this increases the pressure required to open the wastegate and gives higher boost as a result. Its primitive but it works with a few caveats:

Money back if you don't like it

If you send an undamaged kit back within 30 days, for any reason, you'll get a full refund minus postage & packing costs. All UK orders are sent recorded delivery.


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