Another 998 Turbo Project...
#1
Posted 04 July 2012 - 07:48 AM
i know this has been done a few times and i've seen it produces good results!
So i bought a 998 complete with all ancillaries and gearbox on here for £80.... not bad
Also, i've read that the turbo 998's can produce good horses, yet still be very economical and easy to drive around city streets, you cannot get this on a 1380.
I'm planing on the following spec, feel free to correct me with certain parts, but i've done a lot of research and looked all over the yellow bible to get this right...
-12g295 cooper head- ported, polished, bigger valves etc
-standard pistons
-maybe +30 thou overbore (depending on bore condition)
-electronic ignition
-hif6 carb
-lightened/ balanced bottom end
-t2 turbo
-mirage motorsport manifolds
-intercooler
-MG metro cam
-running around 7psi
-1.5 rockers?
Thats the engine spec, obviously on top of that i will have to consider oil parts, fuel pump, fuel return etc.
I've done my research on the pistons, the standard ones are more than up to the job, also with the 295 head i was hoping that the large chambers will keep the CR low enough for a turbo so it doesn't blow the head off... and hopefully the CR will be high enough at low revs to help with lag.
This is the beast here... ;) just a standard 998 as you can see, done around 70,000 miles
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And then the gearbox will be fully rebuilt and i will add a racing clutch, cross pin diff, and possibly straight cut gears to cope with the added stress.
So for now i will be looking for some good advice on the project... for now though the engine is getting a full rebuild.
peace
x
#2
Posted 04 July 2012 - 09:00 AM
#3
Posted 04 July 2012 - 09:59 AM
For a 7psi target, any psitons will do the job. You'll need a set to take to the machine shop if you are planning a re-bore, not sure what +30s are available, +20 or +40 is more typical.
If you are using a carb, the easiest way is to use the HIF44 metro turbo one with the metro turbo plenum. You could use something else, but it's a pain.
#4
Posted 04 July 2012 - 12:37 PM
You're pretty much there. For a road car I'd forget the 1.5 rockers, they'll increase the boost threshold and not make any more power.
For a 7psi target, any psitons will do the job. You'll need a set to take to the machine shop if you are planning a re-bore, not sure what +30s are available, +20 or +40 is more typical.
If you are using a carb, the easiest way is to use the HIF44 metro turbo one with the metro turbo plenum. You could use something else, but it's a pain.
Thats great cheers, i'll definitely follow your advice, you seem to know a lot about fast turbos! so standard pistons with a 295 head will give a good all round CR?
and yeah sorry, i meant it'll be +40 so that gives 1030cc doesn't it?
Metro carb it is!
so do you think this perfectly reasonable for a reliable, nippy car? i reckon i should easily be able to get around 80bhp?
#5
Posted 04 July 2012 - 01:31 PM
I stripped off all ancillaries and then started on the head...
The head was actually really good, no dirt it was very clean and the rockers looked nice too!
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Then the Rockers came off
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It was so clean!
Then Pushrods...
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then the head came off,
There is a lip so it will need boring out, but thats not a problem!
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#6
Posted 04 July 2012 - 04:22 PM
#7
Posted 04 July 2012 - 04:46 PM
yeah thats a good point, i could always buy some dished pistons seeing as i'll have to buy some new overbore ones anyway, the price difference shouldn't be that much,A 295 has 28cc chambers, if you stick that on a 998 with flat top pistons you'll get around 9.3:1 CR, which is fine for the psi you are planning. With the extra cc, with the over bore the CR will increase slightly, but should still be ok. Personally I's just give it a +20 overbore as you won't gain anything with the extra ccs.
cheers
#8
Posted 04 July 2012 - 06:02 PM
#9
Posted 05 July 2012 - 02:58 PM
#10
Posted 06 July 2012 - 01:12 PM
#11
Posted 06 July 2012 - 01:25 PM
#12
Posted 09 July 2012 - 12:01 PM
#13
Posted 10 July 2012 - 09:43 PM
#14
Posted 11 July 2012 - 07:54 PM
But I decided that I'd do it here, this is where most of the turbo boys look.
You're doing a build yourself at the moment aren't you?
#15
Posted 12 July 2012 - 09:11 AM
Also, does anyone know the standard 998 headgasket cc? just for CR calculations
Just found the head has a crack where the stud goes in, looks like someones bottomed it out and tried to tighten it too much, but its only little, i think i'll just leave it there as the crack isnt too bad and it would be much more work to remove it, any comments?
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I may be wrong, but it looks like it has been ported a little bit more than factory spec, the middle exhaust port is also larger in comparison to the other two
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