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MG Midget and Sprite Technical - Breather material

At the third time of asking I think I have got my midget back to operating condition

Some may remember I took my Midget apart because the existing clutch (standard size uprated) was slipping when I gave my Turbo assisted engine the boot.

I decided to modify the clutch to fit a 7 1/2 inch and whilst out I intended lightening the toyota gearbox adapter plate and fit a rear oil seal.

The machinist messed up my back plate and things got worse after that. However I think I have now sorted everything and with the engine in for the third time the engine runs and clutch engages and disengages on request. As can be seen on the photo I just need a couple of blue hoses and some elbow grease to polish up my intercooler pipes and all should be well.

However I still need to do a couple of things.

I need to find a screw cap for my plastic clutch reservoir (if anyone has one please) and more importantly?

I am making a large breather to fit where my dissy used to be. The question I want to ask what material has anyone used to act as an oil seperator within the breather? Metal pan scourer perhaps ?

Robert (Bob) Midget Turbo


What did the machinist mess up?. I do machining for people and if I mess up I expect to sort it out, not happened yet for a customer supplied part, only the odd whoops when made from new so just time and material taken to replace.
David Billington

I would think that you could use either plain steel wool, or stainless, or copper (available at wood working supply shops). Because it will be soaked with oil almost all of the time is why I am supposing it won't really matter what material is used.

In any case, don't use brillo pads, because they are infused with soap (unless you rinse all of that out first!).

Norm Kerr

I've repacked separators on other engines with stainless pan scourers, works a treat. Ordinary ferrous will rust eventually as and when they fill with condensation goo.
David Smith

What is the silver box sitting behind the washer fluid bottle?
Trevor Jessie

Can someone explain what a turbo does? (i know it makes the car go faster, but how does it do that?)
and why is there turbo "lag"?
Seth Brecklin

Seth, googling will give you as much info as you could possibly need, but effectively a turbo consists of two fans on a single shaft, one of which the exhaust runs through, which spins it, the shaft, and the other fan - which pumps air into the engine. More air, when combined with more fuel means bigger bang and more power.

Turbo lag is basically because the speed the turbo is spinning at depends on the amount of exhaust gases, so when at low throttle openings there isn't much exhaust and the turbo barely spins and doesn't create any extra power. When the accelerator is pushed, it takes a moment for the exhaust gases to build and spin the turbo to create pressure in the intake. This is exacerbated by the fact that the amount of air pumped goes up by the square of the speed of the turbo impeller (fan).

By the way Bob, love the car, any further information would be cool even though I'm going down the supercharged route with my Midget (I am also building up a turbo rotary mazda). Are you using a complete metro turbo setup just with an intercooler, or are you using a different turbo? What sort of boost are you running, and what are you doing for spark? Power numbers when you get them would be good too.

Also, what are you doing for engine breathers, have you had trouble with them?

Bob, funny you should start that this thread i'm about to do a similar thing, i have an ali dizzy hole bung & a 3/4" S/S adapter on my desk at the moment waiting to go onto the lathe.
I am going to use one of my spare morrosso oil seperators from the bung to the catch tank.

I like you air filter, which make is it? any chance of a picture of the mounting bracket.

Brad 1380

oooh, good point about engine condensation periodically soaking the breather mesh with moisture.

I agree with David then, about using stainless "wool".

Norm Kerr

A little background for Seth... Turbochargers, or more properly "turbosuperchargers" were originally developed for aircraft engines so they could still provide adequate power at altitude, where the air is thinner. Here's a nice shot of a P-38, in which you can see the turbos mounted just behind the engines:

To tell the truth, I don't know all that much about the history of turbos in relation to car engines. I just know that my 2010 Cooper S has one, and it most definitely adds to the fun!

Gryf Ketcherside

So many questions, but first Thanks Dave "Smiffy" I seem to think you had suggested that material some time back.

David Billington.

Yep the machining was poor. I had the Toyota plate from Frontline many years back. The thickness of this plate was 12mm, and I wanted to reduce it's weight a little plus the PM oil seal could only marry up correctly with the original plate thickness of 7.5mm. Rather than use my normnal Machinist I had a friend at work do it in our machine shop. He owed me one for an electrical job I had done for him previously. Instead of machining an area in the middle of the plate down to 7.5mm somehow communication was poor and the centre of the plate was cut away completely and the outer edge reduced to 7.5mm, jesus I almost wept! I had only 3 datum points left to try and rebuild the plate which we eventually did best we could. The real niggle was contacting Tim at Frontline to source a new one. They no longer stock them and have no engineering drawing!! I reminded him of his promise to customers some years ago which was, when we no longer manufacture these parts we will post all information and drawings with the MGCC!! Seems like he forgot to do that! Thanks!

Trevor Jessie

It is my breather catch tank


By utilising waste energy in the exhaust system to spin an air pump. The pump forces fuel mixture into the cylinders at a more rapid rate (twice the pressure would mean twice as much fuel and air for the same flow) than by atmospheric pressure alone. The pressure of this pump governs the ultimate power.


Yep Metro turbo with intercooler. Present PSI 20 achieved by using a different waste actuator. Before present clutch uprating would slip clutch if booted at 90mph+.:)
Bob Turbo Midget England

& the air filter is...?
Brad 1380

Sorry got called away and couldn't finish my reply. Why does work always interfere in our hobby??

Andrew the ignition system I use is Weber Alpha

Brad the air filter is a very cheap rip off of most cone filters and I bought it from my local motor shop, I bet many others stock similar. :)
Robert (Bob) Midget Turbo

This thread was discussed between 08/09/2010 and 09/09/2010

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