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 1434 Posts Member #: 8466 Post Whore Mansfield |
6th Jun, 2011 at 09:38:27pm
Just wondering what compression ratio you guys would recommend for my webcon alloy 7 port cylinder head with direct port injection, planning on running upto 16psi. I was thinking 9.75-1. Will be running phase 2 cam, nice intercooler etc. Class C 3rd Place Avon 2011 14.18 @101mph |
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 10022 Posts Member #: 1456 Mongo Barnsley, South Flatcapshire |
6th Jun, 2011 at 09:52:49pm
You'll probably be alright at that. I think for insurance purposes I would personally go a bit lower say 9.2:1 If something is worth doing, it's worth doing half of. |
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 9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
6th Jun, 2011 at 09:53:22pm
Iteresting. I did look into the subject of CR when fitting my alloy head, the theory being that you can run higher with an alloy head than with am Iron one.
Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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 1346 Posts Member #: 2340 Post Whore Dublin Ireland |
6th Jun, 2011 at 10:05:52pm
IMO it's not the meterial the head is made of that denotes what CR you can run but more the combustion chamber shape/design. On 17th Feb, 2009 Rob H said:
I find the easiest way is to super glue the bolt to the end of one of my fingers. ______________________________________________________ |
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1434 Posts Member #: 8466 Post Whore Mansfield |
6th Jun, 2011 at 10:23:56pm
I ask because I spoke to John K at SC today and he recommend upto 10-1 for upto around 14psi. I orginally was planning 9-1, so now I should be able to get far better off boost power then expected and better drivability. I know the 7 port head on my n/a needs 11.5/12-1CR with a fast road cam for best results. Paul, whats the best chamber shape? The Chambers have not been reshaped form standard just opened up the spark plug chamber to expose more of the 8mm plug into the chamber. Edited by alaskanow0 on 6th Jun, 2011. Class C 3rd Place Avon 2011 14.18 @101mph |
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 11046 Posts Member #: 965 Post Whore Preston On The Brook |
6th Jun, 2011 at 11:50:06pm
On 6th Jun, 2011 alaskanow0 said:
I ask because I spoke to John K at SC today and he recommend upto 10-1 for upto around 14psi. Sure thats not 4psi? While I have no doubt that you can run an engine at 10:1CR and 14psi boost, it is not exactly going to be reliable. The engine calibration would need to be 100% perfect everywhere, requiring hours and hours of dyno time and plenty of temperature variations. I'd be happier with this sort of configuration on a twin cam head, since as Paul has already pointed out, it is the combustion chamber that is responsible for the best part in reducing detonation. Being alloy doesn't mean it is the magic fix. There are lots of other things to consider such as the location of the spark plug, and the head to piston hight at 14 degrees ATDC anyway, has there been anyone who has built such a configuration on an alloy 7 porter with 10:1CR and 14psi boost? and if so, where the fuck is the dyno sheet and video 
On 26th Oct, 2004 TurboDave16v said:
Is it A-Series only? I think it should be... So when some joey comes on here about how his 16v turbo vauxhall is great compared to ours, he can be given the 'bird'... On 26th Oct, 2004 Tom Fenton said:
Yep I agree with TD........ |
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1434 Posts Member #: 8466 Post Whore Mansfield |
7th Jun, 2011 at 12:15:40am
Thanks for your advice Spocket, I will have to have a think before I machine the head to required cc's. Diffenetly think high CR / lower boost is the way to go for a road car Class C 3rd Place Avon 2011 14.18 @101mph |
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9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
7th Jun, 2011 at 08:11:04am
On 7th Jun, 2011 alaskanow0 said:
Thanks for your advice Spocket, I will have to have a think before I machine the head to required cc's. Diffenetly think high CR / lower boost is the way to go for a road car Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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1346 Posts Member #: 2340 Post Whore Dublin Ireland |
7th Jun, 2011 at 08:29:34am
If it was me I would start off with a standard size combustion chamber I.E. 24cc, Two reasons,
On 17th Feb, 2009 Rob H said:
I find the easiest way is to super glue the bolt to the end of one of my fingers. ______________________________________________________ |
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