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S1 931 (1980) Piston Options?

 
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Harhmless  



Joined: 09 Sep 2015
Posts: 14
Location: Buffalo, NY

PostPosted: Sun Feb 14, 2016 8:32 am    Post subject: S1 931 (1980) Piston Options? Reply with quote

Hey guys,

I know I've found some information on here about pistons before, but I'm to the point where I'm going to need to make a call. I'm setting up the car as a track ready street car with the end goal of about 350 hp in mind.

What options do I have for pistons at the stock bore, and maybe a size up? I have to have the block checked over but my guess is I'm going to have to bore it a bit to make it work, as I have a little bit of damage to one cylinder wall.

Cheers,
Hayden
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1980 931 (US) - Elise
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ideola  



Joined: 01 Oct 2004
Posts: 15462
Location: Woodstock IL

PostPosted: Sun Feb 14, 2016 10:41 am    Post subject: Reply with quote

Best bang for the buck (in my opinion) is a full set of Diamond pistons. For the money, it includes custom slugs in any bore and dish desired, includes fresh wrist pins, spirolox retainers, and TotalSeal rings. There are a few off-the-shelf options out there (flat tops), but they will end up costing the same amount of money by the time you include rings and wrist pins, and will not have ideal compression height, dish geometry, or quench characteristics as the Diamond slugs designed specifically for the 931.


You will be hard-pressed to find oversized OEM slugs, and OEM 931 rings are not available, at least not at anything resembling a reasonable price. However, we do have TotalSeal rings available for OEM pistons, and can have these custom made in any bore desired. These are of a superior material than the OEM rings and far less expensive.

Pistons alone will not get you to your desired power output. To achieve 350BHP, you are going to need some serious thermal management (intercooling + modified coolant circuit) in order to handle the boost required to hit those numbers. Strongly recommend a revised K26/7 hybrid turbocharger to achieve greater efficiency at high boost.

You will also almost certainly need to address the biggest constraint on this motor: the head. Consider the big valve kit, plus a high lift cam.
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1448
Location: Somerset, UK

PostPosted: Sun Feb 14, 2016 7:23 pm    Post subject: Reply with quote

Or talk to Mittelmotor who have a package of off the shelf GTS spec parts, including Pistons rods turbos IC's etc. etc, which have been proven to all work together and achieve 350-400bhp in their FIA Historique race cars
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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