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Juho · Joined: 03 Oct 2018 Posts: 377 Location: Finland

Ive seen many posts about using 931 head and high cr pistons on na application, but couldn't find any other builds than ideolas stroker. I want to get a new engine to build and drop in at some point. Thinking of buying a turbo head, forged conrods and vw flattops. I want to stay 2.0 liter. What kind of power figures you think could be achieved from a setup like this?

morghen · Joined: 21 Jan 2005 Posts: 8879 Location: Romania

Mittelmotor has a bolt on kit for the NA.
No reason to have forged rods or other pistons as long as you're running that heavy flywheel and valvetrain.

I was also planning a light 2L based build.
I was thinking 2.1L with bigger but lighter pistons, lightened but original: crank, rods, tappets, valves, flywheel.
That would be a great engine to drive but its a lot of work and money to do it...so i cheaped out and went the lazy way of the supercharger.
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Juho · Joined: 03 Oct 2018 Posts: 377 Location: Finland

morghen · Joined: 21 Jan 2005 Posts: 8879 Location: Romania

What are your power goals and whats your budget?
NA clutch, TT and gearbox hold in excess of 200HP...proven by Raceboy on his turbocharged NA.
90mm is impossible i think, 88mm is largest if i'm not mistaken.

I run 0.2bar on my supercharged 924 and while powerwise its probably no more than a 20hp net gain, the torque and the way it gets out of corners is impressive.
Cost-wise you cant beat a charged application.
If your budget is big enough a lighter internal NA with a 2.1L is probably the cleanest way. But if you factor in a cost the supercharger is the cheapest and easiest as you can do it yourself in an afternoon, the turbocharged is next but still cheaper than a custom NA engine.

For the bolt on kit you'll have to phone them, but iirc the total is about 4-5k...but with proven and tested parts.

Juho · Joined: 03 Oct 2018 Posts: 377 Location: Finland

ive got a m45 sitting under my bed lol. idk i kinda just want to build a ”race engine”. Also i want that 7k rpm lol. itbs/carbs are nice also. and i think u can build the 2.1 for alot cheaper than 4-5k.

Juho · Joined: 03 Oct 2018 Posts: 377 Location: Finland

also a small turbocharger setup with manifold turned upside down and a pipe going straight to intake would be cool, sadly this isnt possible with tilted engine.

Cedric · Joined: 27 Aug 2004 Posts: 2608 Location: Sweden

Have a chat with "gegge", also a 924 veteran, as he is called on the forums, he built something similar to what you are talking about , sounds really cool

https://youtu.be/ZEepQkhJKV4
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1980 924 Turbo
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Juho · Joined: 03 Oct 2018 Posts: 377 Location: Finland

i really want to get a new engine that i can paint and make it look really nice, impossible to find 924 engines in finland though

Cedric · Joined: 27 Aug 2004 Posts: 2608 Location: Sweden

Engine building is nice, its not always about maximimizing power. 924 engines are often really cheap over here, maybe you need to come over and pick one up when things calm down

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1980 924 Turbo
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Juho · Joined: 03 Oct 2018 Posts: 377 Location: Finland

maybe, cruise to sweden costs next to nothing, where are the engines usually posted up for sale? I couldnt find any on blocket. Ive been looking for a engine for like 6 month and none has come up sale in Finland :/. And i really want to get a new engine because i can keep driving my car and its a blank canvas.

Could i buy a audi 100 engine and a slap a 931 cylinder head on that, because ive seen plenty audi 100 engines for sale here

Juho · Joined: 03 Oct 2018 Posts: 377 Location: Finland

speaking of supercharger, something like this would be cool also but sadly i dont have tools to fabricate (or skill haha)

morghen · Joined: 21 Jan 2005 Posts: 8879 Location: Romania

I'm working on a bolt on kit...you just need a Lidl tool set to make it work on your 924...you can go back at any time...it should not take you more than a few hours to do it.
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Juho · Joined: 03 Oct 2018 Posts: 377 Location: Finland

would have to go back to efi, not a big deal though i have parts ready, just need a engine

Cedric · Joined: 27 Aug 2004 Posts: 2608 Location: Sweden

TJC · Posted: Mon Jun 15, 2020 11:45 pm Post subject:

I would also be interested in hearing from anyone with information/experience building an engine using the 931 head but running Weber carbs or ITB's...but preferably the Webers.

I have a complete Series 2 931 engine, less turbo and ignition to play with and it would be nice to shoot for getting 150-160 honest horsepower out of one. Knowing that the D-Prod engines used here in the States pumped out about 180 with their injection setup it shouldn't be too difficult I would think.

I think it would be fun to have in a light weight mountain/canyon cruiser and perhaps more reliable/less costly than a turbo. Oh, and of course they certainly do sound so nice too!!!

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'95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!

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