We have had the VVC control on the Emerald M3DK ECU for several months now but to date only on the Turbo Technics supercharger conversions. In fact, the software was written for the TT pressure-charged engine having both vacuum and pressure readings on load. Unlike the normal Alpha-N system which takes load from a throttle potentiometer the VVC software is using a Manifold Air Pressure (MAP) sensor.
We have had a lot of enquiries about the VVC ECU from normally aspirated Elise 111S and Caterham owners, but not unreasonably, everyone wants to see the result before they invest in a new ECU. My honest opinion has been that if the engine is not modified then gains over the stock ECU were unlikely to be had. The Caterham had more of a chance because it runs a non-Rover exhaust manifold so the stock ECU calibration may well have been out. Now we have taken our first steps into aspirated VVC ECU development and it looks encouraging. The car in question was a Lotus Elise 111S which is about to be modified with a ported head and a different exhaust cam – a route already proven by Dave Andrews of DVA Power. While the engine was still standard we wanted to fit an ECU and get some power figures.
This car was ideal for us because although the engine was box stock it had been fitted with a Janspeed style 4-2-1-exhaust manifold and “sports” cat, plus an ITG air filter. Using the TT software as a starting point we only mapped the engine for full throttle, having first taken an “as received” power run. 162bhp is more than the factory quote for this engine so the exhaust and inlet mods were doing something.
Only having done a few VVC engines we have no set procedure for mapping them as yet. With the aspirated engine I have a system which is akin to shelling peas but with the VVC engine you have cam timing and injector timing to play with as well as fuel mixture and spark timing. It looks like the cam setting is really critical in that it has a big influence on cylinder filling. You need the cam setting right before you optimise the fuel and the spark, but you need a reasonable fuel and spark setting before you can optimise the cam duration! It goes around in circles and takes a lot longer than mapping a “normal” engine.
Early results look like it is worth the effort. If you compare the graphs the M3DK gains everywhere over the stock ECU – apart from 6500rpm onwards. Our missing headline number was a bit of a mystery until we realised it was an injector sizing issue. The TT software has a second set of injectors in the system and ECU is configured to work with this set up.