Individual Throttle Bodies

After some research I decided to upgrade Tigger with individual throttle bodies. Basically this means that each cylinder in the engine is being fed with an air intake that is specifically tuned. The advantage of the ITBs is that the air intake is configured using horns that direct the air into each cylinder which replace the plenum - the length of the horns is specifically chosen to create a standing pressure wave between the outside world and the cylinder air intake. This pressue wave is then effectively forcing air into the cylinder (as opposed to sucking it in through the plenum). This produces slightly more power and engine torque whilst having the benefits of more reliable engine starting and stable tickover. The upgrade has a couple of implications:

• The air intake horns add width to the engine block that have to be accomdated.

• A re-map of the ECU is required.

As a result of that second point, the upgrade was beyond my capability - however, I have heard of people doing the mechanics and then managing to drive to a garage with a rolling road to get the remap done.

I went to Northampton Motorsport who gave me the options of having the air intake completely within the bonnet (possible for an SV chassis but produces less power / torque improvements) or cutting the bonnet to have the air filter pulling cold air. Aditionally there is an option to have a Carbon Air Box but this also pulls the air from within the engine bay resulting in less noise (important for track days), but not as great a performance increase.

I opted for an external air filter and handed Tigger over to the experts. They needed the car for 2 weeks which was a bit of grind, but I couldn't have been more pleased with the results. Aesthetically the Air Filter poking it's head through the bonnet does a great job (IMO) of balancing the primaries and exhaust on the right hand side, and just looks great.

The performance increase can be seen in the graphs below - a modest step up of around 20bhp which kicks in at 4,000rpm.

Before (Red) and After (Black) Power & Torque Curves

The remapping is quite an intensive process. Six runs were undertaken on the dyno and an entire tank of petrol was used in the process. Each run takes the car through the gears upto maximum revs each time and getting upto 130mph - see the video below:

Dyno Run

As for driving after this upgrade - the car now starts on the first turn of the starter; the induction noise is a delight at low revs; and the power that kicks in at 4,000 revs feels unstoppable.