Ecoboost Plus 4 Plus (final Report)

I must be setting a trend with "Possum", the turboed "Plus 4 Plus", since MMC have followed suit with their turboed Plus 6. Their yet to be announced new Plus 4 will have a turboed four cylinder BMW engine.
Possum’s rolling road tuning took place on March 20 at Stanton Motorsports (just off the M4) and went very well.
Possum had been carefully run in for 250 miles. All the instruments working fine, as per the standard car, and careful brim-to-brim tank measurements saw 31.7 mpg during test drives. Touring consumption seems to be around 36 mpg.
With minimum boost (0.4 bar) the engine already felt very pokey. On the dyno the boffins from MBE Systems progressively increased boost to a still-modest 1.0 bar with fuel map to suit and the result is pretty amazing. Target figure of 240 flywheel bhp was reached (more is available with extra boost) but the all-important torque figures exceeded expectations.
Torque curve is very flat from 2500 rpm to 5000 and peaks at 3000 rpm with 280 ft lbs (standard GDI Plus 4 only manages 145 ftlbs). To sum up, very driveable, loads of low down omph and no lag thanks to the advanced Borg Warner twin scroll turbo.
One major difference from the standard Plus 4 is the smoothness of the engine, which is also quite a lot quieter since the turbo acts as a slight silencer. With a high quality 200 cell EU4 compliant cat fitted the emissions have been judged “well within limits” and it will fly through the test, according to Possum’s local Morgan dealer (and MOT test station).
Having driven a few Rover-engined Plus 8’s over the past 50 years, “Possum” feels considerably quicker – and is much lighter.
The only downsides were self-inflicted. I fitted a new and rather fierce MX5 racing clutch and lightweight single mass flywheel instead of a standard MX5 clutch and the dual mass flywheel which came with the new engine. As a result it was initially a little juddery moving off from a standstill – this is hardly noticeable now since the clutch had bedded in. If doing it again I’d go for the standard MX5 clutch which should cope fine given the light weight of the car. Also, on the rolling road, we blew off a turbo boost pipe between the intercooler and the throttle body. This was because I had to shorten some of the alloy pipes to fit and they lost their “swage” on the ends for the Jubilee clip to snuggle behind. I found an inexpensive swage-maker on E-bay so all the pipes are now very secure and have the extra security of Jubilee clips lock-wired together.
So I’m a happy bunny and can’t keep the smile off my face. Icing on the cake was my insurers only asking a reasonable £130 a year extra for the uprated car.
Possum was ordered from new with a limited slip differential and I had already fitted a panhard rod. With all the extra torque anti-tramp bars were considered advisable to eliminate spring “wind up” and those nice people from New Elms provided a pair with machined stainless spring plates which are a work of art. I took boss Tim Ayres for a brief passenger ride in the car and he emerged impressed.
Several of you have asked about carrying out your own Ecoboost conversions on GDI or Duratec Plus 4s, or having one done. If so you need to contact Tony DeSciscio at:
Finally, “Possum” will be at the Prescott “Thrill on the Hill” on Sunday August 11th – see you there.