A-Series budget turbo. Good idea or waste of time?

[metroman]

Okay, I've been given a Metro Turbo head, carb, manifolds and a dead turbo on a Marina block.

The block seems to be in good condition with zero wear to the bores and apparently a sound bottom end. It's also a low compression spec unit with the dished pistons so 8:1 comp.

The Metro parts are all good except for the turbo which has been taken apart and not put back together right. It's also siezed.

My plan is to check the bottom end of the block for wear in the bearings, clean it all up and reassemble. I'll also relap the valves and rebuild the carb and give it all a good checking over. A friend has nearly finished restoring a Minor so we are planning on putting it in that on the grounds that he finds a replacement turbo.

Is this a total waste of time that'll just see the pistons burnt through in minutes or is it a bit of a myth that you need to run super special pistons with a turbo? The compression will be lower than a standard Metro Turbo and we won't run silly boost.

Cheers

James

[cobblers]

The block and crank on the gearbox in sump A serieses is different to the longditudinal ones, so I don't think you'd be able to put the engine in the Minor without quite a bit of work.

Doh, missed the bit about marina block and crank. Ignore me, I'm an idiot!

[sparkyt]

From what I can tell your only going to need special pistons and con rods to get the compression lower to run a turbo but you already have low compression so all should be good as you say your only going to be running the little turbo ..I've just spent 40 min googling your question I'm board at work

[metroman]

Thanks for the fast replies. I was hoping you'd say that! I'm sure that even with standard boost it'll be quite scary enough so stupid power isn't the aim, just a good running engine is all that's needed (and already more than his gearbox can take I'm sure ;D)

[metroman]

turbocharged-midget.tripod.com/id1.html

[TurboDieselWeasel]

Try it... If you blow it, it's blown ;D But unless you try it, you'll never know. If noone would risk anything, we'd still live in dark caves, afraid of everytjing...

I've been told the low-comp SPI pistons in my engine wouldn't last with 10.5:1 compression - well, they did. Untill the bore were so worn the engine basically lost all compression ;D That wasn't a turbo - but... Well, I tried it.

Turbos are sensitive, though. Don't go mad with boost and make sure it's very well set up and tuned, before you boot it A wide band o² sensor will help.

More info can be found on turbo-minis.co.uk - they'r also Metro-friendly ;D

[metroman]

I think this has to be tried! I'll get on turbo - minis when the build starts in the summer. I'll try and borrow an o2 sensor if I can, hopefully it won't be far from standard Metro spec so won't be too bad to set up but that's a little way off...

[chairchild]

They'll work fine for sensible boost and power levels


If you want to start chasing silly power... just get a more modern engine there first! lol, waaay cheaper!

[TurboDieselWeasel]

Mar 19, 2012 18:38:52 GMT metroman said:

The block seems to be in good condition with zero wear to the bores and apparently a sound bottom end. It's also a low compression spec unit with the dished pistons so 8:1 comp.

Just to make sure; we are talking about a A+ 1275cc engine, right? These always got dished pistons! It's only the 998 that had flat top pistons...

It's a good idea to actually measure the compression ratio of your engine! Who knows what pistons found theyr way into the engine over the decades... Are there any number on the pistons?

[scruff]

What he said, measure it. Do some maths and see what your compression really is.

The 924 turbos run compressions of 7.5:1 (Series 1) and 8.5:1 (series 2) with no intercooling.
It is perfectly possible to run higher compression but you have to be more careful on the ignition and mixture to avoid detonation.

Rich and retarded is safe!

Wideband O2 would be great but if you can work a soldering iron you can lash up a simple gauge that will work on a narrow band, but it will only tell you rich or lean rather than a AFR. Still nice to know you are rich and 'safe'

[RetroWarwicK]

running 5-6psi on a standard engine wil be fine. just depends on how worn the engine is really. was gonna suggest you google the turbo mg midget.....you just need to be sensible.

i'll be doing essentially the same thing to my mgb eventually - using a mgb usa spec manifold, turbo'ed hif44, maestro turbo plenum and a garrett gt15 off a saab.