998 Turbo basic spec
Turbo Mini Forums

Finally decided to put my fire breathing Turbo Mini build on the back burner for now and build myself a turbo daily driver.

It's gonna be a Clubman Estate with a 998 turbo.
As it's gonna be a daily load lugger(I might even be towing with it) it'll need bagloads of torque rather than big bhp.
Will be done on a budget as well and must have Mirage Manifolds as I don't want to cut up the bulkhead.

Could anyone suggest a basic spec?
I already have a standard Metro Turbo cylinder head.Would this be any good for it?I also have a Toyota CT9 turbo for it and it'll be using MegaJolt for sure.


Thanks a lot lads.

Tom

Warning:Stig in Training

Well the spec of my 998 road engine will get you very close to what you want.

The spec is an R5 T2 with 9.2:1 CR and an MG metro cam, all on a mirage manifold with Metro Turbo carb and fuelling plus an intercooler.

For lower down torque you might want to use the standard 998 cam.

I know nothing of that turbo, but the first thing to consider is will it fit on the mirage manifold?, I suspect that the elbow won't. So you're kind of wasting money on a mirage setup if the turbo dosen't fit and the elbow is wrong!

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Worth noting that Wil has a 12G295 head. You could use the 12G940, but it is extra hassel getting the block pocketed.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Thanks lads.
Wil,I know it wont fit but I am in no way capable of making my own manifold so I need something to start with.The Toyota turbo has a square flange with rounded corners.It's easier to adapt that flange to a mirage manifold rather than build a whole new manifold.
Would be great about the cam though.Less stuff to buy

Ben I was wondering if it was possible to backcut the valves and machine the seats to save the pocketing,like Keith Calver did in his article in Mini Expert magazine.
However I was thinking that maybe this would make the valves too thin,possibly making them run a lot hotter than usual and leading to pre-ignition/detonation.

Finally off what engines did the 12G295 come?

Thanks again lads

Warning:Stig in Training

It all comes down to what you have or can get your hands on. If you have a 940 then use it. In standard MG form we had 140 bananas in the TT. It will work fine on the road. Yes you can do what Keith did instead of pocketing, I prefer pocketing though. If this is a daily drive though and low boost it will be fine I guess.

The 295 is an ideal head, but difficult to find unskimmed. They are off 998 coopers and MG migets.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Why do you prefer pocketing? Doesn't it ruin the exhaust flow?I know this is just a road engine but I'm curious

998 Cooper.Oh.

Guess I'll be using the 940 then.

And another thing.By how much should the pockets clear the valve and should the "floor" of the pocket behorizontal or angled?

Cheers

Warning:Stig in Training

I think as long as you keep the pockets as far clear of the top ring as possible is the most sensible - and make sure there are no sharp edges to the pocket, in the bottom or on the edges into the cylinder/ around the top of the cut out head gasket side.

I have a 295 under the bench - anyone know the before skimming thickness?

If Carling made Mini engines
it would probably be like this one!

2.750" rings a bell for some reason but not 100%.

this one measures 2.665"?

If Carling made Mini engines
it would probably be like this one!

John, not sure about the unskimmed thickness, but they should be 28cc chambers iirc.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

unskimmed they should be 2.750", but i dont think its a hard and fast rule

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Right so far it's a 9:1 CR,940 head,CT9 Turbo on mirage manifolds,Pocketed block.
What about cam?
WHat do you lads think of Wil's suggestion of using the standard 998 cam?

Also what about pistons?Will I have to get flat tops to get the CR right, because of the larger 940 chambers?


Cheers again

Edited by El Potter on 29th Mar, 2008.

Warning:Stig in Training

The 940 chambers are smaller than the 998 ones.

With 6cc dished pistons you'll need around 24cc chambers whatever head you use

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Smaller? wow I never knew that.
Thanks for the heads up Wil

Warning:Stig in Training

You'll need to do some volume measuring, no good guessing. Remember to include any pocket volume in the calcs.

Righto Tom.
Better remove and tear down the engine first though

Warning:Stig in Training

Try the 12G202 heads from the 1100 and some of the rileys I think. I have mine on a warm 998 with a 0.030 overbore. The big thing with these heads is de-beaking them and making sure you have the chamber size doent blow out in the overall equation(I have 9:1 for my set-up).

Fairly plentiful here too so easy to get hold of one.

Hooroo

Rob Forsyth
Miniot!

can you open up a standard 998 head big enough to make it worth using or is it just not worth it?

Too much trouble looking for one of those heads Rob.
I've got a couple of the 1300 heads, the 12G940s so it's not worth buying another one eh.

Got to wondering about the cam though.
Seems every one who asks is being pointed to a N/A Mg metro cam.
I was going with the standard 998 cam but I'm confused now.
I'm primarily looking for lots of low down torque as this will be a daily hack to carry stuff in.
Which is best?

Warning:Stig in Training

Standard 998 cam will be good for your purpose

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Ok Wil. Thanks mate.

Warning:Stig in Training

Yepp there are many ways to skin a cat Potts. I use the 202 here as they are plentiful and you dont have to do too much to them to make them work well - loads easier than pocketing the block for a 1300 head and the likes.

The cam specs are the Russell Engineering RE13 cam, 1.3:1 roller rockers(had 1.5:1 but kept breaking the springs...lol), .030 over, 9:1 comp and basically standard apart from a Dellorto 40DHLA and a Lukey muffler.

The turbo is going ahead now and have a small turbine from the US and I have come across a manifold for it as well(locally sourced from Sydney) and this is the turbo - remembering this is a play around motor - just for the sake of building one...

http://cgi.ebay.com/ebaymotors/MOTORCYCLE-...emZ150302817653

I picked it up for a song while our dollar was near 98 c US - arrived in Oz with $600 outlayed. Glad I bought it a while back and not now - would have cost me over $1000 australian!!

Will get some pics up as I progress.

Hooroo

Rob Forsyth
Miniot!