Supercharged 998 Engine Build Help
Turbo Mini Forums

Hi all,

First of all, I hope this is posted in the right place. Now...at the end of next week I am going to start my engine rebuild for my suck through supercharged 998, and I was wondering if anyone could tell me about any changes, etc that needs to be made to this spec:

1. 998 engine
2. Pocketed
3. 1275 High Performane head, worked to lower compression ratio.
4. HIF 44 Carb
5. Supercharger
6. Grey clutch and AP plate
7. High capacity 998 oil pump
8. High capacity 998 water pump
9. 998 crank, fully worked
10. 998 + 40thou dished pistons
11. 1.5 roller tip rockers
12. 256 Cam
13. Oil cooler
14. Straight cut drops, for a 998
15. Centre pick up
16. Megajolt ECU
17. Lightened duplex Timing Gear
18. Charge cooler (If it can be fitted)
19. A Paul Wiginton Gearbox Baffle Tray
20. Lightened & balanced con-rods with up-rated bolts
21. Steel centre main strap
22. Lightened and balanced flywheel
23. Smaller pully for more boost, about 10psi
24. Silicone hoses
25. 2 Core Radiator

I also have a few questions too ask:

1. What is the biggest you can pocket a 998 block too? I want to be able to fit the biggest 1275 head on.
2. What cc in my dished pistons should I really be looking for?
3. Which head gasket should I use with a 998 block, and a 1275 head?
4. What compression ratio should I be aiming for.

Thats all I can think of at the moment. Wil_h has answered a lot over on TMF, but been as there are a few more people over here with forced induction now how, I thought I would post ovre here too.

Cheers

Edited by 1987_ParkLane on 14th Apr, 2009.

Well for a start, what sort of supercharger do you plan on running?

Eaton m45?

And what kind of boost do you plan on running?

Edited by Oli on 7th Apr, 2009.

this should help you out no end
http://www.turbominis.co.uk/forums/index.php?p=search

good choice of cam and rockers .but a 276 cam with normal rockers would work as well,(use the 1275 fuel injected 276 cam timing if available for a 998..)

try the m45 with stock pulleys 1st ,you may get a suprise boost wise .

it sholud make more than 10 psi on a 998 with stock pulleys.

dont bother with the whole worked crank rods etc ,just not needed ,balance the flywheel if you must, but still not really needed .

grey clutch cover not orange .

8.2 to 1 cr ,with no intercooler .if going blow through ,them you could run an intercooler ,then cr 8.6:1.

no need for centre strap or lightened cam gears .no need for straight cut drops .

deff need for 4 pin diff and straight cut box if over 120 lbs/ft and some grip .

regards
robert

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

You're right Robert. 6000rpm is about 10psi on a 998.

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

www.twin-turbo.co.uk

Cheers robert and, again, wil_h, some good info there.

So what sort of cc pistons and head chambers would he need to get 8.2:1 CR??

Cheers James, another good question I forgot to ask.

Off the top of my head on a 998 with the pistons coming flush with the block & 6cc dish, BK450 gasket & 25cc chambers the compression will be about 8.29-1.
This isn't taking into account ring land vol, {Wil may be able to advise on this} But it gives you a rough idea as there's not a huge amount of volume contained here.

WWW.TURBO-MINI.COM

Thanks for that Phil

Also, anyone know any pros/cons of using a 45 DCOE Webber Carb with this set up?