3 replies to this topic

[cradley-heathen]

having considered the opinions to get some more useable power in my metro i am now wondering if turbo-ing it might be viable?

 

the engine is a stock 998, low mileage unit which im thinking i may as well leave in now as the cost of building a 1275 based unit from scratch is possibly a bit much at the minute.

 

im not after ultimate power, just a bit more clout for everyday driving (and the soundtrack would amuse me too im sure)

 

would a standard 12g940 head give me a chamber volume suitable to lower the c.r. suitably for turbo charging?

 

im pretty sure i heard before it would be ok but could i leave the standard 998 cam in?

 

what turbo would i need to use ideally? and what car/model would it be from? how much can they be picked up for?

 

and otherwise am i just looking at fitting a fuel return line, electric fuel pump, regulator, oil feeds for turbo? (would it be a water cooled turbo?)

 

and as for a carb would i be ok sourcing a hif from a metro turbo? or would this be a little large for a small bore/relatively tame 998 turbo setup?

 

thanks for any help guys, just trying to work out what might suit my needs and budget best!

[Ferretboy221]

There are a few basic factors you need to consider:

 

What piston type you have fitted ie flat top - dished etc.

 

Head chamber capacity - standard cam 4180 is about 25cc

12g940 is about 22cc standard.12g195/12g206 cooper 998 heads are 28cc as standard - double check.

 

Comp ratio that you end up with doesn't want to be any more than 9:1 

 

rough calculation (you need to measure all of this v carefully):

Cylinder volume (swept) ie 998 divided by 4 = 249.5cc

plus compressed area volume ie any space at the top of the stroke - 1cc piston top area below bore top 2.8cc head gasket volume + Combustion chamber size.

so CV + CA divided by CA = 249.5 + 1cc + 2.8cc+ 25cc (CAM4180 head) divided by 28.8 = static compression ratio of 9.6:1 

 

correct rising rate fuel regulator with proper turbo type fuel pump ie not a facet type one.

 

Turbo type is a very open subject  - what ever does the job you want really. t2/ gt15/gt17 etc......

 

Hif 44 turbo carb is the usual carb choice with needle to suit the 998.

 

Cam wise the favourite is the NA MG metro cam.

 

There's lots more and im sure a more experienced Turbomini's person will take over with more relevant details i recommend reading the 998 section of www.Turbominis.co.UK

Edited by Ferretboy221, 06 September 2013 - 07:58 AM.

[mad mk1]

There is some good reading on here


http://www.turbo-mini.com/62147.html

[6joshh6]

I'd have a look through the turbo-mini website, these two articles in particular are going to be useful http://www.turbo-mini.com/62147.html and http://www.turbo-min...7257/index.html . Regarding your compression ratio, to use a 12g2940, you would need to have an overall ratio of around 9 to avoid it going pop although 8.5 or so would be better as you could turn up the boost more, which makes more sense rather than limiting yourself before you've even put the thing together. To get that sort of compression ratio, assuming you have an earlier 998, you wouldn't have to modify the standard head, to use a 12g940 you'd have to open the chambers out slightly, a standard 202 would need skimming slightly, or the 12g295 would need skimming by quite a bit. However if you have a later 998 or don't mind fitting the flat top pistons, you could simply install an unskimmed 12g295 and have it right without any need to modify.