924Board.org

hadrian017 · Joined: 12 Oct 2010 Posts: 55 Location: Malta

Hi,

I have a euro 924 with N/A engine and i have converted it to dual carbs I would like to know if adding a turbo or a supercharger would be possible with minor changes and how much are the expenses

cheers

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the_mad_electrician · Joined: 16 Nov 2009 Posts: 1073 Location: Central Georgia

s/cs and turbos don't really work well with carbs
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81 924 N/A

2004 Ranger "Edge"

2005 Mazda 6

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

They can if the carbs are designed for blow-through, which the OP's are unlikely to be.
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WeiBe (1987 924S 2.5t) - 931 S3

leadfoot · Posted: Mon Feb 07, 2011 12:31 pm Post subject:

many sc applications use draw through carbs... blow through is more complicated...

sc will be more easier to adapt with current 9.3:1 pistons, but will require alot of customs parts, manifold, pulley, brackets etc... so if you can weld great.
an sc12, eaton m45 or small sc running 6psi no intercooler will give you a reliable system with around the 150/170hp and plenty of torque to boot.
It will also fit in the engine bay nicely

there are no real bolt on turbo systems apart from BAE which are near impossible to find and still require mods to the exhaust system.

also suggest if your making brackets move the alternator at the same time to the other side of the engine bay.
stu
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Anything is possible.

I would suggest not using carbs and use the stock intake and throttle body with an EFI conversion (or even the stock CIS)

However, if you're stuck on the carbs, then you'll need to research how people have adapted forced induction to the type of carb you're running.

If you want to run blow through on a set of sidedrafts, you'll likely need to make a sealed plenum to route the output of the turbocharger or supercharger to the inlet of each carb throat. Plus jetting and fuel system requirements will be quite different.

Suck through might work better, to a point. You can leverage the stock intake minus the throttle body (or gut the stock one) and mount the carb on the inlet of the turbo or supercharger. However, some of the drawback are that most have to split the two throats of the sidedraft to have one blade operated off vacuum to have decent drivability, also you can't intercool the charge as it is loaded with fuel and cooling it after the fact will cause the fuel to pool and drop out of the air.

The higher compression ratio of the euro 924's will limit the amount of boost you can run safely. If you're serious about following this path, then perhaps find a set of US-spec pistons (I'm sure someone in the states would be willing to trade) which will lower the compression ratio. Forcing the air into the cylinders causes the compression ratio in the motor to increase artificially.

There are some great sources available in print for general forced induction planning, configuration and tuning plus a number of sites available for knowledge. This quickly becomes a situation where you have to understand the underlying theory well enough to apply it to the real world situation you're dealing with.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

leadfoot · Posted: Tue Feb 08, 2011 12:36 pm Post subject:

[quote="fiat22turbo"]
The higher compression ratio of the euro 924's will limit the amount of boost you can run safely. If you're serious about following this path, then perhaps find a set of US-spec pistons (I'm sure someone in the states would be willing to trade) which will lower the compression ratio. Forcing the air into the cylinders causes the compression ratio in the motor to increase artificially.
quote]
this is static compression, you also have to look at dynamic compression which can be changed by grinding the duration of a cam and increasing overlap. Chews more fuel but can allow more boost.

I wouldn't even think about suck through turbo... and intercooling under 6psi is also a waste of time
Stu
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

Catamax944 · Joined: 14 Jan 2009 Posts: 140 Location: London UK

Find a renault 5 gt turbo carb ,it might work better.
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Tas931 · Posted: Wed Feb 09, 2011 9:27 pm Post subject:

Euro924S2 · Joined: 06 Mar 2008 Posts: 215 Location: UK

A valid point for a race car, but for a road car does draw through carbs not cause poor general drivability and make it difficult geting through the emissions needed for street use.

Personally, if your only planning on running 6psi which is limited by the standard pistons, why not use the 924 turbo CIS system which will give reliable fueling all day long at that level and is easy to plumb in allowing a quicker fabrication period.

Agreed for intercooled 200+bhp motors EFI should be your route but that's a whole different bag of worms!!! (ask me how I know!!!)

Of course there are many ways to achieve good performance - some are just better than others!!!

Cheers, john
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UK spec '83 N/A with 931 motor with Eaton MP62 'charger @ 15psi. EFI - 565cc inj. Standalone Adaptronic ECU. 951 FMIC. Ally rad. Twin throttle. Recirc valve. Custom manifolds and CAI. 232bhp

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Tas931 · Posted: Mon Feb 14, 2011 9:05 pm Post subject:

leadfoot · Posted: Wed Feb 16, 2011 9:14 am Post subject:

Min · Posted: Wed Feb 16, 2011 12:57 pm Post subject:

Tas931 · Posted: Thu Feb 17, 2011 3:51 pm Post subject:

I love the carby hating out there

for reference i'm an EFI person.

So how many years ago was maximum boost produced.... Even Corky Bell says people use the book to much like a bible (he posts on he Miata forums). While correct for the time period written in, a lot has changed he may or may not have changed his mind about carby's but my point is the book is old people need to stop using it as a gospel.

Certainly sounds like it needs better tunning/Form of cooling the charge. We use water/meth injection on the torana's and volvo Works a treat, I will be putting it on my 924 as well.

I don't need to argue with the principals of fluid mechanics, Corky Bell X decades ago nor anyone else, we have a couple of low-mid 11sec carby turbo's here (1 uses a rayjay off a john deer tractor), that are also street driven. That's good enough for what i would want out of my street car performance wise (maybe your after something else?).

Maybe 1000hp?
http://www.youtube.com/watch?v=fH3VezPiLB8

For our 924's i wouldn't be going Carb it seems like a backwards step, if you want tuning to the Nth degree go EFI, best fuel economy again EFI. For me I want to go MS. But it doesn't mean that you can't go fast in a carby forced induction car.

Min · Posted: Fri Feb 18, 2011 12:20 am Post subject: