The Porsche 924 Owners Club

Dedicated to the Porsche 924
The Porsche 924 Owners Club
It is currently Thu Aug 13, 2020 6:19 am

All times are UTC [ DST ]




Post new topic Reply to topic  [ 74 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8  Next
Author Message
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Thu Jun 11, 2020 2:30 pm 
Offline
Club Member

Joined: Wed Dec 24, 2014 1:14 pm
Posts: 25
Model: 924 Carrera GT
You could always whizz the plugs out and use one of those thin, bendy camera attachments you can get for smart phones and take a peek. My two middle cylinders, the ones where the ring lands broke, would have shown noticeably darker crowns from the extra oil getting into the cylinders so would have given a clue. Mind you, being 6 bar down on the compression test was a bit of a no brainer ... !!

Close examination of the cylinder head flame face showed very small damage pockets inside of the bead, presumably from mixture pre-igniting in the squish space. I don't know if you can manipulate those bore cameras to look back upwards at the cylinder head - you can certainly see the piston crowns.


Top
 Profile  
Reply with quote  
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Sat Jun 13, 2020 7:36 pm 
Offline
Club Member
User avatar

Joined: Sat Feb 16, 2013 7:44 pm
Posts: 367
Location: Somerset
Model: 924S
Apologies if links to these videos have been posted on the forum before. They were on another car forum I visit and I thought they might be of interest to those who use forged pistons.

How it's made - Omega forged pistons - Part 1 https://www.youtube.com/watch?v=Jr6qk5wCPEQ

Also parts 2 and 3.

_________________
---------------------
1986 Porsche 924S
DS3 PureTech SS130 ( my daily drive )
Audi TT Roadster ( the bosses drive )


Top
 Profile  
Reply with quote  
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Fri Jun 19, 2020 11:24 am 
Offline
Club Member

Joined: Sun Jan 21, 2018 11:22 pm
Posts: 203
Model: 924 turbo S1
Ok these guys, https://www.neilbainbridge.com/, can get the following made in two weeks (I believe they come with skirt coating as standard, note the piston surface option). Looks like they’ve done them before.

Is this a plausible spec for an S1 924 turbo rebuild please (noting I sent them a piston)?

Do others want to join in for better pricing? If not I’ll order myself ASAP, I don’t want to wait around much more nor make this too complicated.

—————
Hi, this is what is available in 86.50mm and also in 87.00 please check information and tell me how many you would require and I can cost accordingly as.

For an order of 4 pieces the price is £375 each (without hard anodizing) or £405 each (with hard anodizing).

Best Regards

86.50 Piston Weight 517 Grams + - 5
87.00 Piston Weight 534 Grams + - 5


Attachments:
8056954D-2CE2-4541-9CFE-E0BA7FBC18A8.png
8056954D-2CE2-4541-9CFE-E0BA7FBC18A8.png [ 94.37 KiB | Viewed 576 times ]

_________________
Porsche 924 Turbo S1 1980 two tone green with tartan interior (project).
Lotus Europa S2 in Bahama yellow (running).
Top
 Profile  
Reply with quote  
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Fri Jun 19, 2020 2:30 pm 
Offline
Club Member
User avatar

Joined: Sat Jan 30, 2010 11:13 pm
Posts: 16835
Location: Somerset
Model: TheOnly Way Is Turbo
incl VAT?

_________________
Steve - Joined: Sat Jan 30, 2010 10:13 pm......think I have lost far too much time in this forum.........
1980 924 Turbo Series 1 - Alpine White & Guards Red
Omega forged pistons, lightened and balanced bottom end, ARP studs + Cometic MLS HG, Piper fast road cam, K27/26 3257 hybrid turbo, 951 ducted FMIC, Custom intake manifold, Mittelmotor dizzy & cam pulley, Adj boost - dyno’d at 239.5 rwhp @ 1.05bar, Zeitronix ZT2 & Phormula KS4 knock sensor, 944 turbo all alloy radiator, Hayward & Scott custom tapered race exhaust, GAZ Gold coilovers, Fuch'ed up, Quaife LSD
2017 VW Passat Variant GTE Advance
2015 Nissan Leaf Tekna


Top
 Profile  
Reply with quote  
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Fri Jun 19, 2020 3:40 pm 
Offline
Club Member

Joined: Wed Dec 24, 2014 1:14 pm
Posts: 25
Model: 924 Carrera GT
A few comments. This is the Mahle catalogue entry for the S1 piston -https://catalog.mahle-aftermarket.com/eu/product.xhtml?eid=965704&r=0.48358096364204184.

1) note the standard gudgeon pin is 24mm, NB proposal is 22mm. Note tolerance for the pin bore in the piston is 23.996 to 24.000. My old Mahle's have the gudgeon pin "gap" ( ie distance between the pin bosses on the piston which the conrod fits into ) as 31.5mm, the NB proposal has 24.5mm. I haven't got any conrods to hand so I don't know if this narrower gap is a problem. Does the deal include getting special race style narrow conrods with smaller pins? Note standard length pins are 64mm whilst these pistons only take 52mm.

2) the compression height of the NB proposal is 43mm, standard is 45mm. Effectively, the pistons will sit 2mm more inset into the bore than standard, rather like the JE Pistons MM supplied me. With a piston bowl volume of 36cc and this "pancake" of combustion volume above the piston at TDC, the CR will be about 7.5:1. Presumably that CR is your goal?

3) the lower compression height and other geometry ( eg shallow combustion bowl ) give the piston height at 70mm, standard is 75.6mm. I don't think that's a problem re piston noise.

4) Rings on the nb proposal are 1mm top, 1.2mm 2nd and 2.8mm oil control v 1.5/1.75/3 on Mahle std. They seem typical of modern practice eg the JE Pistons are the same. Do you know which ring make you're getting with the pistons?

5) the NB proposal is 534gm for a 87mm piston whereas my 87mm Mahle std S2 pistons were 508 gm, so they are going to be pretty strong as forged pistons.

They seem an excellent price compared with my JE Pistons - just be sure what you need to do about the conrods and what rings are included in the deal.

Hope that helps - Colin


Top
 Profile  
Reply with quote  
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Fri Jun 19, 2020 3:46 pm 
Offline
Club Member
User avatar

Joined: Sat Jan 30, 2010 11:13 pm
Posts: 16835
Location: Somerset
Model: TheOnly Way Is Turbo
Have you cc'd the head so you know what 'actual' CR will likely be?

_________________
Steve - Joined: Sat Jan 30, 2010 10:13 pm......think I have lost far too much time in this forum.........
1980 924 Turbo Series 1 - Alpine White & Guards Red
Omega forged pistons, lightened and balanced bottom end, ARP studs + Cometic MLS HG, Piper fast road cam, K27/26 3257 hybrid turbo, 951 ducted FMIC, Custom intake manifold, Mittelmotor dizzy & cam pulley, Adj boost - dyno’d at 239.5 rwhp @ 1.05bar, Zeitronix ZT2 & Phormula KS4 knock sensor, 944 turbo all alloy radiator, Hayward & Scott custom tapered race exhaust, GAZ Gold coilovers, Fuch'ed up, Quaife LSD
2017 VW Passat Variant GTE Advance
2015 Nissan Leaf Tekna


Top
 Profile  
Reply with quote  
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Fri Jun 19, 2020 3:49 pm 
Offline
Club Member

Joined: Sun Jan 21, 2018 11:22 pm
Posts: 203
Model: 924 turbo S1
Hmm apparently not including VAT. Thanks for the other tips. Not done anything on the head yet. I’m happy with standard ish compression.

_________________
Porsche 924 Turbo S1 1980 two tone green with tartan interior (project).
Lotus Europa S2 in Bahama yellow (running).


Top
 Profile  
Reply with quote  
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Fri Jun 19, 2020 3:56 pm 
Offline
Club Member
User avatar

Joined: Sat Jan 30, 2010 11:13 pm
Posts: 16835
Location: Somerset
Model: TheOnly Way Is Turbo
If the heads been skimmed it will raise compression. There is a limit on material loss through skimming.

Raised compression is a good thing on an S1, it will give you better throttle response.

_________________
Steve - Joined: Sat Jan 30, 2010 10:13 pm......think I have lost far too much time in this forum.........
1980 924 Turbo Series 1 - Alpine White & Guards Red
Omega forged pistons, lightened and balanced bottom end, ARP studs + Cometic MLS HG, Piper fast road cam, K27/26 3257 hybrid turbo, 951 ducted FMIC, Custom intake manifold, Mittelmotor dizzy & cam pulley, Adj boost - dyno’d at 239.5 rwhp @ 1.05bar, Zeitronix ZT2 & Phormula KS4 knock sensor, 944 turbo all alloy radiator, Hayward & Scott custom tapered race exhaust, GAZ Gold coilovers, Fuch'ed up, Quaife LSD
2017 VW Passat Variant GTE Advance
2015 Nissan Leaf Tekna


Top
 Profile  
Reply with quote  
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Tue Jul 14, 2020 8:21 pm 
Offline
Club Member

Joined: Sun Jan 21, 2018 11:22 pm
Posts: 203
Model: 924 turbo S1
Still waiting for new forged quotes... have quote for cast Mahle ones. Sigh. The Mahle detailed spec sheet I got sent might prove handy.

_________________
Porsche 924 Turbo S1 1980 two tone green with tartan interior (project).
Lotus Europa S2 in Bahama yellow (running).


Top
 Profile  
Reply with quote  
 Post subject: Re: 924 turbo series 1 forged pistons
PostPosted: Tue Jul 14, 2020 9:52 pm 
Offline
Club Member
User avatar

Joined: Mon Jan 04, 2010 11:24 pm
Posts: 17594
Location: Gloucester
3D printed pistons?

https://www.pistonheads.com/news/ph-fas ... 2-rs/42751

_________________
To travel hopefully is a better thing than to arrive - RLS

1984 924 N/A RUBY RED METALLIC - 924 of the Show, National 2018
1988 924S Guards Red - sold
1986 924S Guards Red - sold
1984 924 N/A Black - sold
1980 924 LE MANS#1 - sold
1980 924 LE MANS#2 - sold
1977 924 Martini - sold


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 74 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 43 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
© 2009-2020 The Porsche 924 Owners Club - Powered by phpBB