Twin carb on a 16?

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maxgreenwood
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Twin carb on a 16?

Post by maxgreenwood »

Does anyone know if a twin carb setup is possible to fit on the 16 engine?
I gather it was done on the Bx sport, just wondering what it would take
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Re: Twin carb on a 16?

Post by Tim Leech »

They have a twin choke solex so no great benefits . The twin carb set up on a Sport won't fit a rhd car because of the steering column.
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Re: Twin carb on a 16?

Post by Way2go »

Tim Leech wrote: The twin carb set up on a Sport won't fit a rhd car because of the steering column.
:?: Is the 16 engine the other way round to a 19 then? :? My inlet manifold is at the front.
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Re: Twin carb on a 16?

Post by Tim Leech »

nope, its the suouped up exhaust manifolds.
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maxgreenwood
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Re: Twin carb on a 16?

Post by maxgreenwood »

I'd heard somewhere the distribution of fuel isn't that uniform- the middle two cylinders get a healthy dose as the carb sits right on top (shorter journey) but the outer two lose out a bit.

This maybe nonsense! I do find it hard to imagine engineers being happy with that. Just curious anyway, I don't know much about these things (as you can probably tell) :)


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'92 16TXS (m), Dark metallic green, 74k
'90 16TZS (m), White, 86k
'89 19TRS auto, Olympic Blue, 133k
'88 Saab 900 8v Turbo (auto) 107k Red with Tan leather, lovely drive and well maintained.
'07 Hyundai Santa Fe 2.2 CRDi 85k (m). Practical family wagon
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Re: Twin carb on a 16?

Post by mat_fenwick »

It's all a question of compromise, and what's deemed an acceptable balance of price/performance/efficiency when it was designed. A single carb feeding multiple cylinders won't give an idetical mixture to all cylinders, although will be 'good enough' to do a satisfactory job on a lower performance engine. That said, a carb fed engine is never going to have a perfect mixture over the entire rev/load range anyway as there is no feedback loop, which is where injection systems and lambda sensors come in...

Fitting twin carbs might help with the even distribution of fuel over the cylinders, but it's not all you have to consider unfortunately! The larger the carb(s), obviously more air will flow but also the slower the air speed for a given volume of air. This causes problems at low speeds i.e. poor throttle response. (That's the purpose of a twin choke carb - one opens at low throttle positions to give small carb performance when pulling away, and both open beyond a certain point to give better performance at the top end.)

Given that a 1.6 will need less volume of air than even a standard 1.9, I'd think the Sport manifold and carbs would be significantly oversized and hence reduce efficiency.
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Re: Twin carb on a 16?

Post by citsncycles »

From looking at Hilary's sport when I was at the Westons the other day, those carbs are impressive, although first glance down the back of the engine has me puzzled about the clearance issues for RHD cars.

I agree that sport carbs would probably not be suited to a 16, but you could probably build a similar set up with a couple of Weber DCOE's (for example). It may end up turning into an expensive project though as you may end up having to modify the exhaust and possibly change the cam shaft to get anything like the full benefit.
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Re: Twin carb on a 16?

Post by MULLEY »

If you want to make it go faster, just fit nitrous, that'll make its overtaking urge more impressive ;)
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Re: Twin carb on a 16?

Post by maxgreenwood »

Ok I'll write that naive idea off then!
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Re: Twin carb on a 16?

Post by mds141 »

The Talbot Sunbeam was fitted with a twin Weber set up on the 1600 Sunbeam Ti. If you can get hold of a Weber catalogue and cross reference parts numbers, you might come up with a solution.
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Re: Twin carb on a 16?

Post by citsncycles »

It all depends on what your budget is I suppose. There are after market efi systems out there which can be set up with a laptop, but I'd imagine the complete set up will be so expensive you may as well just stick a bigger engine in!
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Re: Twin carb on a 16?

Post by Tinkley »

Going further back the Simca 1204S had twin Wbers too. I wondered about trying 2 carbs on my 16 but I actually expect that converting the ignition to full electric with individual coil packs would probably be better and more fuel efficient. All my m/cycles except the LE Velo had full electronic ignition and coil packs and that means this mode was available from the early 70s'!.

Kitch reckons the fuelling is the problem on the 16 and other petrols. He may be right, but I am not convinced it is the only reason. My bikes were fine on carbs admittedley one per cylinder, though the Gilera had a twin choke for its 558cc cylinder.
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Re: Twin carb on a 16?

Post by citsncycles »

Can't really comment on the fuelling on petrol BX's as experience is limited, but I do know that the GS's tend to run better with a Weber rather than Solex carb, and the BX's tend to have Solex carbs. I gather rebuild kits for Solexes are expensive too.

It may be worth looking at other cars fitted with similar engines to see how they're set up. For example there are a few 14's out there that have had their Solex set up replaced with a Weber from an AX GT
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Re: Twin carb on a 16?

Post by Thread Bear »

Well if it is a 16 laid out like my TRS the air tract is appalling. So the thing probably is not going to get enough air. That will be in proportion to revs. The manifold looks crap to start with and it shoves the downdraft against the bonnet. So I can see every reason to bin that lot if there was a viable option.
The exhaust manifold is not the worst but goes from an acceptable two to one into a tiny pipe. Seems a Citroen thing to have tiny exhausts. 1.9 TZD has the same issue and the answer is on the shelf. So easy mod there, switch to elements of the GTI exhaust. Could create something more interesting, but not sure its worth it as it would be simpler to buy a GTI.
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Re: Twin carb on a 16?

Post by Tinkley »

Actually I thought the 16 had a large exhaust!. On the Morini cylinder head a small exhaust valve (2 valve Heron Head - 18mm exhaust 23mm inlet 2X 172cc cylinders) was found to contribute massively to improved torque with almost no effect on top end. Yes, I know it is a bike engine but the basic design was copied by both Jaguar and Porsche...
I expect Peugeot made the same link. The air inlet is not ideal but the only real problem is the classic lean burn one on warm up on cold days. Basically the inlet tract gets to an awkward temperature for icing after about 1 to 4 miles and then the engine likes to die. Not unique to Pugs though our Mariner 25 HP outboards (twin cylinder) at the sailing club are exactly the same, once started on a frosty morn, run for 5 minutes or they will run on one or not restart.

Some people found the inlet tract on the BX 14s got too hot and added another thick spacer to stop early vapourisation in hte carb. I believe the really early ones had a thinner 'gasket' than the later ones.
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