my mg midget turbo
Turbo Mini Forums

im new to this site so hello everyone,
i need a bit of help with me and my dads turbo'd midget, weve put everything on it the turbo, carb, exhaust, head etc and had it running, it was all ok, it leaks a bit of oil but thats a seal that we no needs replacing, what weve done is we had the 1293 engine (which had been bored out by the last owner from 1275) and baught the turbo off ebay, we bolted it on and started it up, was running fine (only taking it upto about 4000rpm) and then on the way back from out test run my dad took the rpm a little higher(to about 5500-6000) and we just lost half the power. after struggeling to get home i took the head off and the head gasket had gone between cylenders 1 and 2. we never baught some metro turbo pistons and were thinking that because the pistons that are in it are only slightly dished(not as much as metro ones)that the compression ratio was too much for it to take, is this true? is it just because we took it to high rpms that the gasket blew? should we put the metro turbo pistons in or is there something else that we can do to help lower the compression without having the engine out to replase pistons?
thanks for any heelp on the subject,
Steve

What have you done with the ignition system? If you have left it standard the chances are there is too much total advance which has lead to detonation and this has taken out the head gasket.

Ideally you need to lower the compression ratio as well. This can be done by enlarging the chambers in the cyl head. A user called Benross on this forum does this at a good rate. As a start you need to know what compression it is currently.

What boost pressure is it running?

erm we dont realy no its probably the standerd ammount that a metro turbo puts out it wont be much also our boost gage is connected up to the pipe that goes from the dump valve to the manifold is this the correct place to put the boost gage pipe? yes the ignition system is standerd, can you recomend a ignition system that will help stop detonation? thanks for the help and ill be in contact with benross soon
thanks again
Steve

Standard boost will be 4psi-ish.

The easiest way of sorting the ignition is to lock up the centrifugal advance mechanism inside the dizzy. Then set the ignition timing to 25 degrees fixed timing. This will give you a "safe" timing setup although will compromise low end pick up and fuel economy.

A far superior alternative is to use the MegaJolt mapped ignition system. This allows you to retard the timing with reference to boost pressure. Use the search function to learn more about it.

ooh coinsidence, i was looking at this about half an hour ago http://www.turbomidget.connectfree.co.uk/nographics.htm