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March 2011

After hardly getting a look in these past couple of years, I've been fairly busy on the Chesil over this winter

After experiencing fuel system problems a couple of times at the Le Mans Classic last year albeit in 43 degree heat and stop-start traffic, I decided to re-appraise it - despite it apparently working fine for several years.

My conclusion has been that in the very hot ambient temperatures the fuel in the return lines got so hot it started to vapourise and prevented fresh fuel gravity feeding from the tank above, which in turn caused the the pump to overheat.

In ordinary temperatures and ordinary running enough fuel is consumed by the engine for fresh fuel feeding the accumulator to keep things sufficiently cool. But not in the hottest weather i've ever experienced...

So out goes the gravity fed fuel accumulator, to be replaced by a swirl pot fed by a low-pressure pump. And in comes a return line back to the tank so that the low-pressure pump is continually refreshing the fuel in the swirl pot by that in the tank.

That way, the whole volume of the tank would need to heat up for me to experience a repeat of the problem.

As a further measure I'll also add a heat insulating gasket between the manifold and throttle bodies reducing the thermal transfer into the fuel lines in the first place.

So, the fuel system has changed from this:

to this:

And the photo below shows the new pump, filter, and swirl pot, located under my fuel tank.

Whilst the fuel tank was out I redesigned the tray that it was mounted on in an effort to lower it about a centimetre both to make the filler cap look flush with the bonnet and. more importantly, to make space for the return line under the bonnet.

The before and after picture below shows the subtle but worthwhile improvement to the height of the filler cap itself.

July 2011

Attended the Brooklands auto/aero jumble with the Speedsters Club, which was my first real trip out in the speedster this year (The camper van continues to be used most of the time). I spent some of the day before fine tuning the cold start settings of the ECU and also the acceleration enhancement (The engine would go momentarily lean after each gear change when accelerating hard)