Induction & Boost


The Lotus Elan SE Turbo uses the Isuzu’s 4XE1-WT engine and IHI RHB5 Turbocharger which is capable of supplying a lot more than the stock 0.6 Bar.

There are several simple methods to increase the Elan’s stock 0.6 bar boost levels up to just below the 1 Bar fuel cut off limit set by the ECU.


Manual Boost controller (MBC)

A quick cheap method of getting more boost is to replace the Boost control valve with a simple adjustable valve. This method will let you adjust boost up to the ECU cut-off limit of 1 Bar. The metal work valve Shown above will cost about £12 and is available from SP Airtool Ltd 9041203 . You will also need 2 X 1/4″ Hose adaptors and hose clamps

Although I have used this valve for several years without causing any noticable damage to the engine, unlike the Mountain Chip it does not allow the ECU to add additional fuel at high boost levels.


BBR Tuning’s original upgrade for the Elan’s 1.6 litre Turbo engine used a Fuel Cut Defender (FCD) which was spliced into the wiring to the MAP sensor.  The Boost control valve (BCV) plumbing was removed and the restrictor was used to control the amount of boost. Once again, like the MBC, this does not allow the ECU to control the air / fuel ratio at high boost levels and there is a risk of the damage to the engine. Installation instructions

BBR now offer their Starchip Software upgrade but at £500 it’s a lot more expensive than Alans Mountain Chip upgrade.

Mountain chips


Probably the best performance upgrades available for the Elan.

The stock programming of the ECU gives the Elan’s turbo a maximum boost of .65 bar and a fuel cut-off limit set at .92 bar, giving an estimated 165bhp.

With the mountain chips installed, the ECU will allow a maximum boost of .95 bar and raises the fuel cut-off limit to 1 bar, giving an estimated 200 bhp while still having the ECU maintaining the correct air fuel ratio at any boost level.

If you want to convert to a closed loop system to take advantage of the extra performance offered by the V5 you will also need to install the Bosch 15701 Oxygen Sensor . If you have an S2 Elan the O2 sensor is already installed. If not, this sensor will plug directly into the existing wiring loom. Early cars will need an additional wire running from the bulkhead to the ECU.

The Oxygen sensor plug can be difficult to remove. I would recommend soaking it with penetrating oil for several days prior to removal. Also taking the car for a good blast down the highway and getting things nice and warm, then cool the plug using an ice cube.

Take care installing the new sensor. I would recommend purchasing an Oxygen Sensor Socket.

The various options available and more information on the chips can be found on Alan’s website



Air ducts & Induction Kits



Air filters

K&N offer a high flow drop-in air filter for the Elan’s standard trashcan air filter box. K&N p/no. E2360. Available in the US for $36 or or £34 in the UK


Top End Performance  have developed a High flow steel inlet pipe which is fitted with a K&N open filter. p/no. B050A6. The pipes are available in a wide range of powder coated colours.

The pipe, which could be better finished internally, is much better than the original Lotus hose, but unfortunately heavier. The K&N B050A6 filter is now obsolete but could be replaced by any of the models that mount to a 3″ diameter pipe. $175 direct from Top end Performance in the USA.


 Blow off Valves

A BoV is used  to prevent compressor surge, and reduce wear of the turbo. BoV’s relieve the damaging effects of compressor surge by allowing the compressed air to vent to the atmosphere, making a distinct Whooshing sound.

Although the Baily dump valve seems to be quite popular with Elan owners, it does involve cutting the hose between the intercooler and the throttle body. The Top End Performance Kit Uses a HKS bov. and a metal pipe to replace the original rubber Lotus pipe. The HKS bov is adjustable and works well with the Everest chip installed.     I have been using the TEP pipe and HKS bov for almost 10 years and can highly recommend it. You can choose to have the pipe powder coated in a range of colours.

Depending on your throttle position when changing gear, some BoV’s can be quite loud. Therefore some owners may prefer to use a recirculating dump valve which ports the excess air back into the intake, upstream of the compressor inlet.

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