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Home > Help Needed / General Tech Chat > Compression question

jameswildcooper

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Leicester

9th Dec, 2011 at 02:15:28pm

Quick question...
Im running +20 pistons so 1293, they have 18 cc dish and my head is running 20.5cc.
What compression overall am i roughly running?

eden7842

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leicestershire

9th Dec, 2011 at 02:19:36pm

U need to know the deck hight, as 1 thou can make alot of differnce to the end figure

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

jameswildcooper

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Leicester

9th Dec, 2011 at 02:38:28pm

Its a standard metro turbo block.


John

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Mongo

Barnsley, South Flatcapshire

9th Dec, 2011 at 03:11:31pm

what pistons are they?

If something is worth doing, it's worth doing half of.

jameswildcooper

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Leicester

9th Dec, 2011 at 03:46:12pm

Omega forged

John

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Mongo

Barnsley, South Flatcapshire

9th Dec, 2011 at 03:53:23pm

So they run 30thou down the bore on an unskimmed block.

So your compression would be:-

7.98:1 assuming you have 1cc for ring lands.

If you skimmed the block to bring them flush you would have 8.46:1

If something is worth doing, it's worth doing half of.

jameswildcooper

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Leicester

9th Dec, 2011 at 04:06:17pm

Ok thanks. Havnt touched the block yet. I was hoping to run about 7.9 with it on my blow though surcharged set up running 14psi


theoneeyedlizard

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The Boom Boom speaker Police!

Essex

9th Dec, 2011 at 05:32:36pm

7.9:1 ??

Why so low. Are superchargers really that bad?

In the 13's at last!.. Just

jameswildcooper

756 Posts
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Leicester

9th Dec, 2011 at 06:03:40pm

I just got told by Neil at Slark who is doing the kit that would be best. just going off what I've been told tbh.

eden7842

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leicestershire

9th Dec, 2011 at 06:15:23pm

what does johnny run with his sc set up?

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

jameswildcooper

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Leicester

9th Dec, 2011 at 06:58:18pm

He hasn't got his anymore i don't think, but sure he was running Bout 8.0 at 14psi

almichie

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Wiltshire

9th Dec, 2011 at 09:20:04pm

With or without intercooler? That's the question. Dont eaton Superchargers add a lot of heat to the inlet temp?

The screw type of compressor isn't as efficient as an aero dynamic type, meaning it'll add more heat. Plus boyles law means over a million degrees of inlet temp. Maybe this could account for the low CR?

On 7th Nov, 2011 apbellamy said:
 Shaft seems nice and snug


On 24th Mar, 2012 apbellamy said:
no no no no, you need more boost! you can never ever come on here and say I have enough boost, that's just silly.


On 29th Mar, 2010 Star Mag said:
these give no problems with good head

jameswildcooper

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Leicester

9th Dec, 2011 at 10:30:37pm

With a cosworth intercooler hopefully *smiley* engine is being built slowly atm and get charger kit next month....

eden7842

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leicestershire

9th Dec, 2011 at 10:52:54pm

Is it the same kit as johnnys?

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!
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