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Author Topic: Let me introduce my maztra  (Read 48962 times)
Bart_Maztra
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« Reply #30 on: August 10, 2007, 07:06:12 am »

The car documents of the murena says "4 cilinders" and that is now not correct. I should bring my car to the motoring goverment to get the documents changed. But i am scared that they find something they don't like, like pollution, soundlevel, handling or construction. If that happens, they will keep the documents....

The same thing with a V6, it is no "4 cilinders"
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Anders Dinsen
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« Reply #31 on: August 10, 2007, 08:34:36 am »

The car documents of the murena says "4 cilinders" and that is now not correct. I should bring my car to the motoring goverment to get the documents changed. But i am scared that they find something they don't like, like pollution, soundlevel, handling or construction. If that happens, they will keep the documents....

The same thing with a V6, it is no "4 cilinders"

There are four cylinders in total on your brake calipers, so I don't see the problem Huh
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
roy4matra
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« Reply #32 on: August 14, 2007, 04:38:44 pm »

The peugeot engine was megasquirted, and my intention was to do the same thing with the wankel. Now it is still on its original carb, but i have lots of trouble with this carb. The engine coughs, hesitates and stalls when i floor the pedal...

Hi Bart,

First I have to congratulate you on the conversion and getting it 'Mot'd.  I remember hearing about your attempt to put the rotary in the Murena, around the time you started, and wondered if it would ever be done as there was so much work involved.  But you have succeeded, well done.

Regarding the carb. trouble, have you considered this.  If you are using the carb. that was designed to work on the rotary engine in the Mazda, and it is directionally sensitive as most are, it will never work properly in the Matra unless you turn it through 90 degrees.  Carbs. are generally designed for one direction of travel, and since the engine has changed to being transverse, assuming the carb. is still as it was in the Mazda, it will have turned too and now be facing the wrong way.

There were owners here a while ago fitting Weber 38 DGMS or DGAS to Murena 2.2 hoping to get better power, but these were designed for a longitudinal engine (Ford Essex V6 engine) and could never work mounted transversely, as those owners found out!  The major problem is the fuel in the float chamber surges when driving and the ducts for the fuel are in the wrong place.

So your carb. problems may be have other sources too, like dirt or blocked jets, but the directional problem will remain even if these are cured.  If you cannot turn it easily, fuel injection may be your best alternative.

Roy
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krede
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« Reply #33 on: August 14, 2007, 05:19:40 pm »

Im curious.. how difficult to get hold of, and how expensive are spare parts for the rotary engines?
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Bart_Maztra
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« Reply #34 on: August 15, 2007, 07:26:54 am »

Directionally sensitive carburettor? I have never heard of it. But your explaination makes sense. Turning the carb 90' is very difficult. I have bought a mikuni carb (equal to solex phh) which is positioned with the airhorn facing forward. When i had this carb installed, i realised that the carb is not mounted level. Thats because the wankel engine is mounted longtudinal in the mazda and is a bit tipped back. The inlet manifold is making a angle to compensate it. Now the engine is mounted level and so the carb is at an angle. The mazda carb have two float chambers and i have set one slightly lower and the other slightly higher to get the right fuellevel at the emulsion tubes.

The minuni carb have 1 float chamber, so the level will never be right. I realised too late that the fuellevel is very critical, so the mikuni will never work right.  (reading a carb manual is very interesting)
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roy4matra
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« Reply #35 on: August 15, 2007, 09:22:41 am »

Directionally sensitive carburettor? I have never heard of it...

Not many owners realise this, and even I'm afraid to say not all mechanics either.

Quote
Turning the carb 90' is very difficult...

I can understand that, and the angle on the manifold to suit its normal Mazda application would present a major problem too.

Quote
... Now the engine is mounted level and so the carb is at an angle. The mazda carb have two float chambers and i have set one slightly lower and the other slightly higher to get the right fuellevel at the emulsion tubes.

That is clever, but would still cause problems I'm afraid since the two emulsion tubes will have different amounts of fuel in them, which will affect the air/fuel mixing.  The holes in the emulsion tube walls are set at specific heights to do their job properly.  If one now has a different fuel level to get the same overall height from ground as the other, they will not be able to work the same or correctly.

Regarding the direction of mounting I'll explain a little more so all can understand.  Under acceleration the fuel in the float chamber will surge to the rear, and when cornering it will go left or right.  Under braking it will come forwards.  The float chamber ducts that feed the various jets are positioned at the rear such that the fuel is always plentiful under straight acceleration and reasonable when cornering when you don't need quite as much, but will 'starve' when slowing or braking, which is fine as that is the time you don't need it.  It's not just the ducts, but the levels in the emulsion tubes too of course.

Now if you turn the carb. through 90 degrees as in this case where you turned the engine from longitudinal to transverse, the ducts are now on one side.  They will get plenty of fuel under cornering one way, but be starved on cornering the opposite way!  Under straight acceleration it will be slightly reduced and be similar under braking.  So you will find that cornering one way will cause hesitation or cutting out, and full acceleration forwards will be compromised unless you compensate with higher fuel levels but that will cause idle and emission problems.  I have seen it many times and there is no cure, except to change the carb. or turn it.

Quote
The minuni carb have 1 float chamber, so the level will never be right. I realised too late that the fuel level is very critical, so the mikuni will never work right.  (reading a carb manual is very interesting)

The type of carb. that might work is the vertically mounted type such as the Weber IDA or IDF which I think may not be directionally sensitive, but it would be best to confirm this with a Weber agent as I have no actual experience with them.  It might be simpler to fit something like the 28/36 DCD type mounted the correct way.  There used to be 90 degree manifold adaptors for these, for when they were used on Minis.  Or how about the 36 DCNF from a Bagheera?  The problem will be making or modifying a manifold to mount them.

Roy
« Last Edit: August 15, 2007, 09:46:08 am by roy4matra » Logged

krede
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« Reply #36 on: August 15, 2007, 09:40:05 am »

Why not convert it to fuel injection while you are at it?.... if you have the know how to fit a wankel in a murena, injection would be a piece of cake Cheesy
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Anders Dinsen
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« Reply #37 on: August 15, 2007, 11:35:59 am »

Why not convert it to fuel injection while you are at it?.... if you have the know how to fit a wankel in a murena, injection would be a piece of cake Cheesy

You were born optimistic, weren't you? Wink

Bart did run his old engine, a 1.9 Peugeot, on MegaSquirt, so he has been there already.

Quote from: roy4matra
Regarding the direction of mounting I'll explain a little more so all can understand.  Under acceleration the fuel in the float chamber will surge to the rear, and when cornering it will go left or right.  Under braking it will come forwards.  The float chamber ducts that feed the various jets are positioned at the rear such that the fuel is always plentiful under straight acceleration and reasonable when cornering when you don't need quite as much, but will 'starve' when slowing or braking, which is fine as that is the time you don't need it.  It's not just the ducts, but the levels in the emulsion tubes too of course.

I've got this picture of the Solex 34CIC which illustrates it:



The emulsion tubes are denoted "Gg", and they make a very rich mixture of fuel and air to feed the jets "K". The higher the level of fuel in the float chamber is, the richer will the mixture be in the jets.

- Anders
« Last Edit: August 15, 2007, 11:44:12 am by Anders Dinsen » Logged

'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
krede
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« Reply #38 on: August 15, 2007, 11:42:42 am »

Quote
Bart did run his old engine, a 1.9 Peugeot, on MegaSquirt, so he has been there already.

My point exactly!! Smiley ... why bother with carbs? (ducks!!) Wink
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Anders Dinsen
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« Reply #39 on: August 15, 2007, 11:46:06 am »

Quote
Bart did run his old engine, a 1.9 Peugeot, on MegaSquirt, so he has been there already.

My point exactly!! Smiley ... why bother with carbs? (ducks!!) Wink

How's your conversion going?
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
krede
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« Reply #40 on: August 15, 2007, 11:53:15 am »

I'm expecting the fuel pump today, and the map air temp and oxygen sensor by next weekend.
I'll try to have it build/run in the 27'th... or sometime that week.
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roy4matra
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« Reply #41 on: August 15, 2007, 01:38:33 pm »

Why not convert it to fuel injection while you are at it?.... if you have the know how to fit a wankel in a murena, injection would be a piece of cake Cheesy

Well I did say earlier that it may be easier to go fuel inj. and whilst I note the smiley, essentially Krede may be right!

I've got this picture of the Solex 34CIC which illustrates it:



The emulsion tubes are denoted "Gg", and they make a very rich mixture of fuel and air to feed the jets "K". The higher the level of fuel in the float chamber is, the richer will the mixture be in the jets.

- Anders

Actually to be totally accurate Anders, the items noted as Gg are the main jets, which on this carb. are mounted in to the carb. casing.  The emulsion tubes are the dotted sections higher up with the air correction jets at the top.  On Webers the main jets are pushed in to the bottom of the emulsion tubes which are pushed in to the air corr. jets at the top; unlike the Solex ones where the air corr. jets cannot be changed separately.  Also it is not strictly true that the higher the fuel level, the richer the mixture.  It is more complex than that, since you can have small, medium, large or no holes in upper, centre, and lower positions, and it it the combination of the right numbers and sizes of these holes at the correct positions that will determine the mixture and progression at all engine loads or demands.  This is why it is such an art/science choosing the correct emulsion tubes.  And the tube numbers are not logical either just to make it harder!  For instance on a Weber going from lean to rich the common tubes are F11, F15, F16, F2, F8, and F7...  On Dell'Ortos it would be 7772.10, 7772.8, 7772.2, 7772.1, 7772.14, 7772.5, 7772.7, and 7772.6!

On heavy acceleration or wide open throttle the emulsion tubes will actually be empty, with fuel pouring in the bottom through the mains, and air coming in through the air corr. jets and mixing rapidly and going out via the auxilliary venturis 'K', to the engine.  When you back off or close the throttle, the wells will fill again to their pre-determined level.  This is set by the float levels which is why they are also important.

You can see from this why the carbs. on an angled manifold with different float levels to get the two side the same, as Bart said he tried, will not work.  The lower side will have more uncovered holes than the higher side; thus altering the mixtures from side to side and the carbs. capacity to feed the engine equally.  Good diagram though - where did that one come from?

Roy
« Last Edit: August 15, 2007, 01:47:45 pm by roy4matra » Logged

Anders Dinsen
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« Reply #42 on: August 15, 2007, 02:14:20 pm »

Good diagram though - where did that one come from?

Thanks a lot for that clarification, Roy Smiley I have always thought that the main jets were the things sticking into the venturi! Wink

But, I think I understand how the emulsion tubes work now, and how important they are. Your explanation also explains how the main jets and air corrector jets are interlinked to give the right mixture over the full air-speed spectrum.

The diagram has been very helpful to me, and I found it on a service documentation page on the 34CIC which a kind person has scanned and put on: http://www.espace-murena.com/Fichiers/Carbu/Solex1.pdf
I simply cut it from there and put it on my own web page, from which the image below is directly linked.

- Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Bart_Maztra
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« Reply #43 on: August 15, 2007, 08:05:26 pm »

Here is the original carb, which is a 4 barrel downdraft. The mixture of each rotor is supplied a primairy and a secondary barrel. And each set of barrels has it's own floatchamber.



For this carb there are no other jets to source.

And the 44phh mikuni carb which should replace the original carb



I bought a new manifold for a weber dcoe which has the same dimensions as this mikuni. And i found a mikuni carb in belgium. Then i got the carb manual and then i learned that a carb which is not level will not work. Sad
« Last Edit: August 15, 2007, 08:07:35 pm by Bart_Maztra » Logged

Bart_Maztra
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« Reply #44 on: August 15, 2007, 08:31:43 pm »

EFI! Already in progress Smiley

This is the plan:
I want to mount two injectors in the mikuni manifold.





This is the easyest way to mount the injectors. It would be better to do 4 and put them in the lower part of the manifold, but there is no room around the manifold for that.
From ebay i bought a few aluminium injector mounts which will be welded in top of the manifold.



That's the story so far. Next week i go to see my "welderman" to do a trailweld on the manifold. As it is cast-aluminium it is a guess if it is wed-able or not. Nice to know before i start cutting holes in the manifold Wink
A throttlebody is also needed. To start with i gonna use the mikuni carb as thottlebody. The venturies will be removed and so i have a simple bold-on thottlebody with a airfilter.

I also need to source two injectors. They need to be around 700cc . And that is BIG. And i need a fuelpump aswell. The fuelpump i had on the peugeot engine is too small.  Need some more searching on ebay.

Here are some pics of the megasquirt EFI which was running the peugeot engine.



The white box contains some relais and fuses and it is a junctionbox who connects the controller to all the sensors, fuelpump, injectors.  The controller is located on the passenger shelf. Under the radio are some buttons and a display to keep you entertained.



The controller is a "build it yourself" kit which can be programmed by computer.






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