998 options on a budget..
Turbo Mini Forums

Right this maybe a long shot but, i have a 998cc engine that i want Turbo'd. I have a few heads lying about
* SPI 12G940b
* Leaded 998 CAM4180
* 948 2A629

So far i have ported the 998 and stripped all the valves and studs out of it, as its unleaded this will mean i need new valve seats and stem seals, what i would like to know is if i only need to replace the exhaust valve seats and stem seals? and what other modifications can be done to this head?

Could i run my 12G940B with a carburettor? but running a 1275 head will this mean i need to modify my 998 block ( if so whats needed?) and also relocate my water temp sensor to a sandwich plate on the thermostat housing?

Also i have a 948 Cylinder head off of a Morris Minor, what would i be able to do with this head, or would it be pointless spending money on it?

ALSO! Can i run an Escort Tdi Turbo? if i make my own exhaust manifold or modify the existing one to make it fit? and will i be able to plum the existing metro plenum and pipe work to it?

Tricky one i know lol but any help would be gratefully appreciated

Chris

Edited by the.eliminator on 5th Aug, 2010.

Austin Mini Designer Stage 1 N/A 1098

Future build- 1275 with Gen' ERA Turbo setup

never done a 998 turbo, wil_h is the man to ask,
i think you'd want a head from a cooper ? a 295 casting?
which has better ports and chmber shape from standard,
or else so im told you need to 'pocket' the block to allow a 12g940 to be used,
you can use any turbo that will fit but,its better to use a proven item that someone else has used in the past, GT series seems to get a good report and if you can find a good one i sspect a T2 will be ideal.......

The idea with the 12g295 is that you lower the compression ratio in the engine to a suitable so that you minimise the risk/possibility of pre-ignition (pink) and detonation from the hot intake gas from the heat of compression. Ideally you'll need an intercooler but you can get round it by running a richer fuel mixture - the extra fuel doesn't get burned but is used as a heat absorbant and evaporates through that heat absorbtion and thus cools the air!

T2 is the one to look for as its smaller and spins up quicker but there are a few variations. The R5 GTT is the most popular. the T3 is very slow to spool up (4k RPM for usable boost)

You can use any of your heads, the minor head is effectivly the same as the early 998 head. what ever way you go (other than 12g295 - standard not skimmed) you'll need to open the chambers to allow suitable CR.

I'm in the process of trying to find out if you really need to lower compression to run a T2 at a lower boost. If it were fuel injected there would be no hesitation and it would be viable as you can monitor knock and pink and adjust timing to suit and counter act. but with carb's and a dizzy... it should be interesting...

Forgot to say that deseil turbos arn't really suitable for petrol cars, they are designed differently as desiels have a much narrower band of usable power. Someone might correct me there - im sure someone on here as tried it!

Do a search on diesel turbos. It is irrelavent of what they were originally designed for, they all have a map. Using the map to match the turbo to your application is key, not the original use of the turbo.

The T2 of an R5 GTT is a good choice on a 998 with about 10psi. More than that and they are not very efficient. The T2 is quite old hat now and difficult to source in good condition. Look at things like the GT15. Have a search for what Wil H is using on his sprint.

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.

Worth remembering that the 12G940 will increase CR on a 998 due to a smaller size of chamber 21,4 vs 24,5

Rusty by nature