MG Midget Turbo
I’ve had various MG Midgets over the years, usually modified to give that little extra ‘zip’ in performance. My latest Midget has a Heritage bodyshell and I’ve owned it for approximately 5 years.
Over this time the car has been gradually modified, the main improvements being a Frontline suspension kit which has greatly improved the handling of the car due to the 2 degree negative camber. This suspension modification I would recommend to every Midget owner. My little MG also has a 5 speed gearbox conversion based on the Toyota gearbox. The Toyota box was chosen instead of the Sierra gearbox as the installation requires fewer bodywork modifications and also because the Toyota clutch mechanism is hydraulically operated, while the Sierra box uses a cable operated clutch. This five speed gearbox conversion has made long distance journeys and motorway driving much more pleasurable due to the extra fifth gear which reduces the amount of work the engine has to do and this means that high speeds can be achieved without the engine revving it’s ‘little socks’ off.
At some stage a 3:7 ratio back axle will be fitted to drop the engine revs even lower for even more relaxed cruising.
Based on rough calculations and depending on the rolling radius of the wheel and tyre, at 4800 revs in 5th gear with a 3:7 back axle, the estimated speed will be 105 mph, which will be quite astounding from a humble little Midget.
My Midget’s A-series engine was originally modified using;
* a single 1 & 3/4″ carburettor, rather than a Weber, as it was much quieter and more economical;
* an Oselli modified head;
* a Marina 1300 crank;
* a 266 cam;
* electronic ignition, to aid starting in cold damp winters and also help the fuel economy.
But since these engine modifications have been made there has been a lot of interest in ‘shoe-horning’ modern K-series engines into MG Midgets, and I had been toying with the idea of doing the same. The benefits of having a such modern engine would be better economy, the ability to use ‘green’ fuel and also more performance. The drawbacks with fitting a K-series are the major bodywork alterations necessary to make the engine fit and also the expense of obtaining such an engine.
Meanwhile, a friend of ours was in the process of rebuilding his Midget using a Heritage bodyshell, Frontline suspension kit, 5 speed Toyota gearbox conversion and telescopic rear dampers but for the engine he had decided to try to use a Metro Turbo unit instead of all the other options available to him. On investigation he found that using a Turbo turned out to be the most economical way of getting a ‘quick’ engine (over 100bhp easily) into his Midget.
In my view this type of conversion would be more in keeping with the Midget as it is based on an A+ series engine rather than using a later modern engine with completely different dimensions.
We, (my father – who is my in-house mechanic and myself) kept an eye on the progress and the problems encountered when fitting the Turbo engine into the Midget. However, the conversion turned out to be very successful as I discovered when I tried to catch my friend’s Turbo Midget while going around Castle Combe. He was also obviously much quicker up the hill at the MGCC Luxembourg weekend event. So now I was convinced that I wanted a to fit a Turbo unit in my car and not the ‘K’ series engine.
So, the hunt was on to find a Metro Turbo engine plus all the ancillary bits and bobs such as the in-line fuel pump and regulator, anti run-on valve, ECU unit, wiring, exhaust manifold and the turbo unit itself.
| We finally found one in Cambridge, which was then delivered to home and the work began. Firstly the engine was cleaned externally, then stripped down and all the internal parts were thoroughly cleaned. A cheap Marina 1300 engine was also bought and the crank was used from it, to make the turbo engine in-line rather than transverse. | The big end caps were line bored to ensure perfect fit with the Marina crank. A Kent cam MD500 specially designed for the turbo engine was purchased and this was fitted into the engine. A crankshaft spigot bush was also fitted to marry up with the Toyota gearbox. |
The head was modified to accept unleaded fuel by having harder valve seats fitted because leaded petrol will be phased out soon.
Various holes were drilled and tapped to mate the engine back plate to the block, also holes were drilled and tapped for the front mounting plate.
An ‘S’ bend exhaust pipe was created to connect the turbo manifold with the standard exhaust pipe with no further modifications to the bodywork.
The fuel system had to be modified as the pump was in line and constantly pumping, so it was necessary to fit a return pipe to take the excess fuel back into the tank.
A number of wiring loom changes were made to include the ECU, various solenoids and the electronic ignition (Metro Turbo). The standard radiator and pipework was retained and plans are now afoot to re-route the pipework to provide space for an intercooler which will help the turbo run more efficiently and have greater boost!
| Due to the height of the turbo unit above the engine the bonnet needed modifying by adding a power bulge. We considered using the ‘C’ teardrop but this was not deep enough so we produced our own bulge out of fibreglass. If any of you out there needs a fibreglass tear drop shaped power bulge we can produce one for you! The above description is a very simplified explanation of all the work involved and there are numerous other items to tend to, however they are reasonably straightforward. After a few teething problems with dirt in the fuel, the engine is running well and the performance is good. The only trouble now is that the brakes aren’t powerful enough. So we are looking at the idea of converting the rear drums to a disc set up. If you are thinking of using a Turbo engine in your Midget , I recommend that you have the suspension modified and the brakes uprated as the set-up of the standard car is not really able to cope with the extra performance and you could be in the ditch before you know it! However once all the appropriate modifications are complete a Turbo engined Midget can be great fun to drive and also safe in the right hands! |
Power bulge necessary the clear the higher Turbo unit |
Miss T Fisher