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Author Topic: Murena 2.2 Carb upgrade  (Read 5215 times)
Abe
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Who wants a Golf anyway?


« on: March 27, 2005, 11:04:06 pm »

Hi folks,

I've been driving my Murena 2.2 for a year now, and i want to upgrade performance by installing a set of Twin-choke Dellorto DHLA 40 Carburators.
Can anyone tell me the right Venturi size for this engine?, currently i have 32mm venturis inside the Dellorto's, and it would be easy for me to fabricate a bigger set of Venturis myself, but what size should i make them?.. i was thinking of 36 mm Shocked
Furthermore i would like to know how to make a decent airbox/airfilter unit, where would i place the inlet opening best?.or are the small  XP/ piper cross filters a good idea?
The manifold will be made of stainless steel 304, with straight intake tubes

Tips are welcome Grin
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How many times do i have to tell you it's NOT! a Delorean.. those dutch.. what do they know about cars..
speed pete
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« Reply #1 on: April 01, 2018, 04:58:45 pm »

Hi Abe,
better use 45 or 48 Twin choke Webers or Dell 'Orto's  and a Politecnic / Sodéma camshaft. Only 40 Twin choke carburettors are too small and won't bring that much performance.
 For the airbox , you can copy the Murena S airbox . You can also modify a Alfa airbox , but is is rather boig and you don't have much room there.
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suffolkpete
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« Reply #2 on: April 02, 2018, 11:18:57 am »

I'm assuming you already have the Dell'ortos and want to use them.  Fitting twin carbs on their own won't make a huge difference to the performance and might actually make things worse at low revs.  You need to use an 'S' camshaft or its equivalent.  The side-draught Dell'ortos won't leave you a huge amount of space for an air box, probably best find a suitable pair of very slim off the shelf air filters.  When you've done all this, get the carbs set up on a rolling road by someone who knows Dell'ortos.
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Colin
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« Reply #3 on: April 05, 2018, 09:30:45 pm »

I agree... Just putting bigger carbs on will not do much, as the valves will still open the same amount and for the same amount of time, so the engine can not do much with the extra fuel and air avalible.
Finding hot cam shafts is so difficult that Roy got 4 made last year, by Piper, they were a bit expensive, but  my standard cam was worn beyond repair. The combination of the new cam and twin Dellorto DLHA45E carbs is good, but finding a suitable inlet manifold is also not going to be easy, my car came with a Politecnic manifold, which is just short enough to fit some air filters, but I do know or others which put the carbs so close to the fuel tank that this is not possible.
Here is my setup.
IMG_20170527_153759794_HDR by c162ujf, on Flickr
« Last Edit: April 06, 2018, 01:35:14 am by Colin » Logged
suffolkpete
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« Reply #4 on: April 06, 2018, 08:09:11 am »

Sports Cars Unlimited converted a number of cars to Dell'orto DHLA 45, the setup looked very like Colin's.  There may be a few of those manifolds kicking about somewhere.  Don't know what camshaft was used for these conversions.
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Colin
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« Reply #5 on: April 07, 2018, 05:36:52 pm »

48mm carbs will be too big, the choice is betweem 40 and 45s. My car came with 40s and now has 45s, with a 36mm choke, one can fit a 36mm choke into a 40mm Dellorto (I know nothing of Webers). My theory was that the venturi effect will be greater on a 45mm carb, with 36mm choke, this should increase efficiency, not necessarily power output. The other reason for the 45s was as we did not know what sort of performance we were going to get with the new cam, it made sense to go bigger. 40mm carbs are good for over 160bhp, and you are unlikely to ever get the 2.2 engine up that high. 
Ian Ratcliffe's engine will be the same spec as mine, but with a different manifold and (my old) 40mm carbs, so it will be interesting to see the differences in power and torque. Here are my numbers....

matra RR by c162ujf, on Flickr
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roy4matra
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« Reply #6 on: April 14, 2018, 04:59:33 pm »

Hi Abe,
better use 45 or 48 Twin choke Webers or Dell 'Orto's  and a Politecnic / Sodéma camshaft. Only 40 Twin choke carburettors are too small and won't bring that much performance.
 For the airbox , you can copy the Murena S airbox . You can also modify a Alfa airbox , but is is rather boig and you don't have much room there.


I'm sorry but I disagree with a lot that has been said in this thread.

The first thing is that the Murena 2.2 needs a much better camshaft before you start fitting bigger and twin side-draught carbs.  For instance the Prep 142 or 'S' will actually run just as well with the original single progressive down-draught Solex and give much better consumption too.  The Prep 142 and 'S' camshafts are not that great really and the original power figures were over stated.  As explained on my website, the standard 2.2 actually produced 113 bhp, the Prep 142 gave 136 bhp, and the 'S' gave 134 bhp.  I have proved that the Holbay Tornado fast road cam profile with a standard down-draught Solex 34 CICF can produce around 140 bhp and give 28 to 34 mpg which is better than either the 142 or 'S'.  If you want proof, check with Anders Dinsen who had my Prep 142 with the standard down-draught carb.

So if you want greater power than the Holbay or equivalent fast road cam profiles you will need an even better cam profile first, AND then you might need the twin 40 or 45 DCOE or DHLA twin side-draught carbs. but then you will have a further problem... and that is the manifold to put them on.  The original Prep 142 and 'S' had a specially designed inlet manifold which moved the LH carburettor over to the right and lifted them both such that the intake was above the fuel tank and the end throat was not seriously restricted compared to the others, and a decent air box could be fitted which picked up cool air low down.  This is necessary since allowing the engine to breathe the very hot air from the top of the engine compartment is bad.  The special manifold also included a coolant extension on the RH end which none of the non-genuine inlet manifolds provide, so you will have to make up something yourself.

All the non-original intake manifolds including the Politecnic one are not good enough and are a compromise which will seriously restrict the intake and therefore the power produced.  Furthermore some of these non-genuine manifolds cause fitting problems with other items such as the coolant pipe under the manifold, and dipstick tube; and all the modified engines with twin side-draught carbs. will drink a lot more fuel and will often drop into the teens when running around in urban environments.  Only on long runs with a large portion of cruising will the car produce 28 mpg or above.

The Politecnic cam was not available last time I checked - he might have your existing camshaft re-profiled but then you can get that done here and cheaper.

As for the  2.2 engines modified by SCU - I have never yet found a decent one!  They are all not much better than standard if indeed they are better - many are actually worse, and they use far more fuel too.

If you don't understand how a poor intake can seriously affect engine power then ask Titus who has seen 6-8 bhp differences for relatively simple difference in the intake system.  And you can't make and fit an airbox similar to the Prep 142 or 'S' on the twin side-draught carbs. fitted on a non-original manifold as there will be no room.  You might just a get very thin 'pancake' filter on the left hand carb. which is almost up against the fuel tank; but these are restrictive and again you will be picking up the very hot air from the top of the engine compartment.  Not only does this restrict the power (hot air contains less oxygen) but the hot air means higher combustion temperatures and they are already hot enough without adding to it.  This can be one reason for many of the failed heads or gaskets.

Roy
« Last Edit: April 15, 2018, 09:44:54 am by roy4matra » Logged

roy4matra
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« Reply #7 on: April 14, 2018, 05:05:09 pm »

Sports Cars Unlimited converted a number of cars to Dell'orto DHLA 45, the setup looked very like Colin's.  There may be a few of those manifolds kicking about somewhere.  Don't know what camshaft was used for these conversions.

Often, unbelievably, they did nothing to the camshaft which meant the twin side-draught carbs. were a complete waste of time!  You just got more noise and higher fuel consumption!

Colin's engine was an SCU modified car and it had a *standard* camshaft and twin side-draught carbs. on a Politecnic inlet manifold and I knew the car when the previous owner had it, plus another with the same mods. and it was rubbish as far as the engine 'upgrade' was concerned.   Anyone who modifies an engine for more power using bigger carbs. alone doesn't have a clue about modifying engines as far as I'm concerned.  The first thing is *always* a better camshaft.

Another thing that the 2.2 engine needs is a lightened flywheel as it is using the heavy standard Tagora 2.2 flywheel intended for the heavy saloon car!  I have modified a number of these engines now and all mine have lightened flywheels and I know the owners are impressed how that alone improves the pick up and acceleration.  One car still has the single down-draught at present with a Holbay modified cam and the performance is so much better with this combination that many don't need much more.

Roy
« Last Edit: April 14, 2018, 05:37:05 pm by roy4matra » Logged

krede
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« Reply #8 on: June 17, 2018, 10:58:56 am »

Hi Abe,
better use 45 or 48 Twin choke Webers or Dell 'Orto's  and a Politecnic / Sodéma camshaft. Only 40 Twin choke carburettors are too small and won't bring that much performance.
 For the airbox , you can copy the Murena S airbox . You can also modify a Alfa airbox , but is is rather boig and you don't have much room there.


I'm sorry but I disagree with a lot that has been said in this thread.

The first thing is that the Murena 2.2 needs a much better camshaft before you start fitting bigger and twin side-draught carbs.  For instance the Prep 142 or 'S' will actually run just as well with the original single progressive down-draught Solex and give much better consumption too.  The Prep 142 and 'S' camshafts are not that great really and the original power figures were over stated.  As explained on my website, the standard 2.2 actually produced 113 bhp, the Prep 142 gave 136 bhp, and the 'S' gave 134 bhp.  I have proved that the Holbay Tornado fast road cam profile with a standard down-draught Solex 34 CICF can produce around 140 bhp and give 28 to 34 mpg which is better than either the 142 or 'S'.  If you want proof, check with Anders Dinsen who had my Prep 142 with the standard down-draught carb.

So if you want greater power than the Holbay or equivalent fast road cam profiles you will need an even better cam profile first, AND then you might need the twin 40 or 45 DCOE or DHLA twin side-draught carbs. but then you will have a further problem... and that is the manifold to put them on.  The original Prep 142 and 'S' had a specially designed inlet manifold which moved the LH carburettor over to the right and lifted them both such that the intake was above the fuel tank and the end throat was not seriously restricted compared to the others, and a decent air box could be fitted which picked up cool air low down.  This is necessary since allowing the engine to breathe the very hot air from the top of the engine compartment is bad.  The special manifold also included a coolant extension on the RH end which none of the non-genuine inlet manifolds provide, so you will have to make up something yourself.

All the non-original intake manifolds including the Politecnic one are not good enough and are a compromise which will seriously restrict the intake and therefore the power produced.  Furthermore some of these non-genuine manifolds cause fitting problems with other items such as the coolant pipe under the manifold, and dipstick tube; and all the modified engines with twin side-draught carbs. will drink a lot more fuel and will often drop into the teens when running around in urban environments.  Only on long runs with a large portion of cruising will the car produce 28 mpg or above.

The Politecnic cam was not available last time I checked - he might have your existing camshaft re-profiled but then you can get that done here and cheaper.

As for the  2.2 engines modified by SCU - I have never yet found a decent one!  They are all not much better than standard if indeed they are better - many are actually worse, and they use far more fuel too.

If you don't understand how a poor intake can seriously affect engine power then ask Titus who has seen 6-8 bhp differences for relatively simple difference in the intake system.  And you can't make and fit an airbox similar to the Prep 142 or 'S' on the twin side-draught carbs. fitted on a non-original manifold as there will be no room.  You might just a get very thin 'pancake' filter on the left hand carb. which is almost up against the fuel tank; but these are restrictive and again you will be picking up the very hot air from the top of the engine compartment.  Not only does this restrict the power (hot air contains less oxygen) but the hot air means higher combustion temperatures and they are already hot enough without adding to it.  This can be one reason for many of the failed heads or gaskets.

Roy

I experienced exactly what Roy speaks of, first hand.
When I bought my, it was Running an "s" cam, with a pair of 40mm sidedrafts on a politec inlet manifold.
If you are not going for more than 140-150 hp, I'd say you are much better off with keeping the stock inlet manifold/carb/airfilterbox.
I had a ride in Anders car way back when he bought it, and it was just as fast, if not faster than mine, and it ran smoother as well. (though the sound of the side drafts is something else).

 
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Jon Weywadt
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« Reply #9 on: June 18, 2018, 12:47:21 pm »

A couple of years ago i had my head (on the car :-) ) refurbished. At the same time I replaced the standard 2.2 cam with a Holbay 58C, for which I got the specs from Roy. I had a standard cam re-profiled in England, but I don't recall from who and can't find the papers.
I run the standard single-barrel carb and can confirm that the cam is what makes a difference. I have not had the performance measured, but the car has much better acceleration.
I have had plans to convert it to fuel injection and have all the parts (from a Peugeot 505 Turbo i believe, which used the same block and head) including a MegaSquirt controller and fast acting lambda probe. However since I cannot do the work myself anymore it will have to be for the next owner.
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Matranaut par excellence Cool
suffolkpete
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« Reply #10 on: June 19, 2018, 11:10:35 am »

I think you probably had your cam done by Coltec Racing Engines as they were formed from the remnants of Holbay and had all the data.  However they no longer do cams as they sold their camshaft machine when they moved premises, which is a shame as they re-profiled my 1.6 cam which made a huge difference (with the standard carb)
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Classicman
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« Reply #11 on: August 04, 2018, 12:42:23 pm »


Another thing that the 2.2 engine needs is a lightened flywheel as it is using the heavy standard Tagora 2.2 flywheel intended for the heavy saloon car!  I have modified a number of these engines now and all mine have lightened flywheels and I know the owners are impressed how that alone improves the pick up and acceleration. 
Roy
[/quote]

Roy, how much do you lighten them by?  I've got my motor apart now and may consider doing this while I'm busy with it.
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Colin
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Posts: 21


« Reply #12 on: August 11, 2018, 11:28:46 pm »

Roy lightens them a lot... More than Matra did on the S. On the S the engine side of the flywheel was machined away, on the ones Roy has done, they also scallop out the clutch side's edge, as shown here...
P1010314 by c162ujf, on Flickr
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GP
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« Reply #13 on: August 13, 2018, 08:10:51 pm »

Go this link for further Flywheel lightening info:

http://www.matrasport.dk/forum/index.php/topic,417.0.html
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