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ic932
Joined: 11 Feb 2005
Posts: 1104
Location: UK
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 Posted: Fri Apr 10, 2009 3:55 am Post subject: S2 pistons into stock S1 |
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I've been asked for my opinion on this subject and thought that it would be good practice to pose it here...
Any thoughts anyone? |
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Fri Apr 10, 2009 4:43 am Post subject: |
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It's possible but IMO not worth the effort. I'd understand it if original pistons were damaged or engine needs rebuild anyway but it's pointless to take a working engine apart.
Better to spend the money on efi and get much better driveability from there together with better fuel mileage and performance.
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'67 911 2.4S hotrod
'90 944 S2 Cabriolet
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'82 924S/931 "Gulf", sold 
'84 924, turbocharged, sold.
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ic932
Joined: 11 Feb 2005
Posts: 1104
Location: UK
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| Posted: Fri Apr 10, 2009 5:10 am Post subject: |
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| Raceboy wrote: | It's possible but IMO not worth the effort. I'd understand it if original pistons were damaged or engine needs rebuild anyway but it's pointless to take a working engine apart.
Better to spend the money on efi and get much better driveability from there together with better fuel mileage and performance. |
I would agree with that too, but his engine is already being stripped down and from the pics he sent me he's gonna need some new slugs. |
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Fri Apr 10, 2009 5:31 am Post subject: |
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Yeah, go for it. With proper fuel management and intercooling, there's no reason not increase the compression, even beyond 8.0:1. In some respects, if I knew then what I know now, I would have had my custom pistons from Diamond done up with a bit higher CR.
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erstwhile owner of just about every 924 variant ever made |
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Dutch924-racer
Joined: 23 Jul 2007
Posts: 1081
Location: The Netherlands
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| Posted: Fri Apr 10, 2009 6:00 am Post subject: |
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Only install them when you have an intercooler. Even better is to convert do DITC ignition.
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ic932
Joined: 11 Feb 2005
Posts: 1104
Location: UK
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| Posted: Fri Apr 10, 2009 6:22 am Post subject: |
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| Dutch924-racer wrote: | | Only install them when you have an intercooler. Even better is to convert do DITC ignition. |
Yes, I was thinking DITC conversion too. But again, that raises Raceboy's point of "is it worth it"? May as well go EFI then perhaps?
So would I be correct in saying that, by installing S2 pistons in an S1 without intercooling and/or ignition/fuel control, the motor is just gonna detonate uncontroably at full stock boost levels? |
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Shurick
Joined: 15 May 2005
Posts: 524
Location: Russia, Moscow.
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| Posted: Fri Apr 10, 2009 6:35 am Post subject: |
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| ic932 wrote: |
So would I be correct in saying that, by installing S2 pistons in an S1 without intercooling and/or ignition/fuel control, the motor is just gonna detonate uncontroably at full stock boost levels? |
Sure.
Rising the compression from 7.5:1 to 8.5:1 without any other mods on M31/01 engine will cause nothing more then knock. You need improved ignition management and any type of IC to get a gain from such conversion.
But with IC and ignition you'll get about 200 crank hp.
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'79 931 -- intercooled K26-3060-6.10 turbo @ 1.2 bar, EFI+EDIS, 951S brakes, stripped interior, 951 look.
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924turbo_sout_africa
Joined: 29 Oct 2007
Posts: 215
Location: Sout africa
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| Posted: Fri Apr 24, 2009 5:15 am Post subject: |
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well havent been on here in some time.
I did this 3 years ago when i had my motor rebuild could not get s1 pistons so i havd s2 piston put in and changed nothing the compresion whent up and well there was no knocking no pre ignition no funny things and i still run everything the same and she is still going strong. and as this is my daily drive and doing about 30 000km per year which is high if it was going to give problems it whould have done it by now.
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Porsche ...where dreams are a reality
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Shurick
Joined: 15 May 2005
Posts: 524
Location: Russia, Moscow.
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| Posted: Fri Apr 24, 2009 6:38 am Post subject: |
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I hope I was wrong in previous post. But we've got the same setup (31.01 with 03 pistons) pinging with a RON 98 octane fuel at 0.75 bar of boost, so it was converted to modern EMS and air2water intercooler.
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WBR, Shurick
'79 931 -- intercooled K26-3060-6.10 turbo @ 1.2 bar, EFI+EDIS, 951S brakes, stripped interior, 951 look.
'86 924S -- R.I.P.
https://www.instagram.com/ru_pacecar/ |
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