Roy's Matra Enthusiasts pages
FAQ's: Frequently Asked Questions
- Some of the facts on the Murena seem contradictory. What is the truth?
My qualifications for this data. I have owned a Murena 2.2 from new, back in 1983, and I have been a professional technician for over 45 years, and always worked on my own cars including my Murena plus I've done lots of work on other Murena too. I have therefore 40 years experience on these cars both as an owner, driver and a technician. I have also driven it on the race tracks and had professional track tuition.
You should understand that the original magazine road tests on the Murena when Matra first provided some cars to the journalists for a group test in Morocco in late 1980, were done with pre-production cars, which often have minor and sometimes even major changes done before production (such as a slight fuel tank change & cooling system changes). In the case of the 2.2 models these were hastily modified 1.6 cars as the first 2.2 models would not start production until February 1981 nor be available to the public until May 1981 so the 2.2 cars in Morocco were prototypes and not the same as the final production version, which hadn't even been finalised at that time! Some of the facts or figures stated at the start were already incorrect and others were taken from the Tagora 2.2 specification from which the Murena differed making them wrong, yet these mistakes have been picked up and repeated far too often as the truth.
Furthermore, the very hot climate was always going to restrict the power of the engines, so things like acceleration figures were never going to match was could be achieved in a more temperate climate like northern Europe where it was expected most would be sold. The engine specification given for the 2.2 model, was the same as given for the Tagora 2.2 from which the engine had come and was assumed would therefore be the same. This shows how little many journalists (and some mechanics) understand about the technicalities of a car, because the Tagora used a longitudinal engine, and its carburettor was the Solex 32/35 TMIMA, but you cannot turn that through 90 degrees along with the engine when it is transversely mounted and still have it work correctly! The float bowl needs to be at the rear, which it was in the Tagora but in the Murena it would be on the left, so the fuel surge on left hand corners would starve the main jets and fuel well and cause cutting out, and on right hand corners it would flood the main jets and fuel well causing rich running and possible trouble too.
Yet many of the magazines stated the carburettor fitted to a Murena 2.2 was either the Weber 32/36 ADC or Solex 32/35 TMIMA and that was never the case as they would not have worked correctly. It was actually fitted with the Solex 34 CICF carburettor which was designed for a transverse installation. A similar Weber for transverse installation would have been the 34 DMTR, but these were never fitted to any Murena 2.2 from the factory. Later there were some supposedly uprated 2.2 Murena where mechanics had fitted the 38DGMS or DGAS Webers taken from Ford front engined V6 cars, expecting this to improve the performance, but a) you cannot increase the performance by simply bolting on a bigger carburettor, and b) those carbs. were never designed for transverse installation, so they gave exactly those problems that I've just explained above that the 32/35 TMIMA would have had given.
Following are most of the common major mistakes made in road tests and articles written about the Murena and published in professional magazines and books. False: The 2.2 engine in the Murena is the same as that used in Peugeot 505; the Murena 2.2 has a 2156cc version the Simca type 180 engine! (with duplex chain driven SOHC) The 2.2 cylinder head is cast iron; the head is aluminium alloy! The 1.6 has one Weber 36 DCA, or two 36 DCNVA carburettors; it has only one Weber 36 DCNVA! The 2.2 has a Weber 32/36 ADC or Solex 32/35 TMIMA; it has the Solex 34 CICF 141 carb! The 2.2 takes 9.3 seconds 0-60mph; that was the 0-100km/h time, and the true 0-60mph figure is 9 sec! The 5-speed transaxle is the same as the Chrysler 1510/Talbot Alpine; the 5-speed transaxle is from the Citroën CX! The car has drum rear brakes; it has rear discs! The rear discs are the same size but the 2.2 uses larger front discs; it is the front discs that are the same, and it's the rear discs which are larger on the 2.2 model! (again a lack of technical understanding here) The fuel tank holds 56 litres; it holds 52 litres! The vacuum storage tank is part of the chassis, similar to the Bagheera cross tube; the Murena vacuum storage tank is a proper plastic vacuum reservoir! There was a leatherette upholstery option; they always had cloth (1.6) or velour (2.2)! The driver and steering wheel were going to be in the middle; it was always designed LHD! The body work is metal; it is polyester fibre of course! The Murena S has a more aggressive front spoiler; it has exactly the same front bumper with in-built spoiler!
You will also see claims that a standard 2.2 was taken to the 'red line' whilst accelerating in the lower gears. The red line was set at 6,300 rpm on the tachometer, but the 2.2 engine peaked at 5,800 rpm and to try to get it to 6,300 rpm would have taken so long that it would be obvious that it was past the power peak and actually taking far too long, and a higher gear would be quicker. Furthermore, since all the Murena I have come across have had tachometers, that read approx. 500 rpm low around the top end, this means to get to the red line on the tachometer would be virtually impossible as you would have had to take the engine to around 6,800-7,000 rpm!
Finally, the power figures were generally wrong in all cases. Read on to understand why.
- What are the true power figures for the Murena?
From the early days of measurement and testing we, in the U.K. at least, have been used to nett bhp as the unit of power measurement, and we expect to see that used in a vehicle specification, and for comparison with other vehicles. In the U.S. they often used gross or SAE power figures which is where an engine is tested on an engine testbed without anciliaries which would sap some of the power. We used in-car measuring just as you would have yourself and the power is measured at the flywheel. If the power is given at the road wheels, that figure will be lower owing to transmission losses which can be as high as 20% for a front wheel drive transverse set up!
However, for some years now any horsepower figure given in magazines and advertising has usually been the DIN figure, even though it may have been incorrectly stated to be bhp. Many also assume bhp and DIN are the same, and I've even seen it written as 'bhp DIN' which is an oxymoron as 'bhp' and 'DIN' horsepower are not the same! Often road test reports forget to state whether the power is DIN or bhp, leaving the reader to assume it is bhp as it has always been, but DIN (or metric) horse power is in fact the same as the German pferdestärke (PS) rating NOT bhp. The PS figure will always be slightly higher numerically, and in my mind using a DIN hp figure in advertising is a sales ploy to make the vehicle look a little more powerful as people will assume it is bhp. If it is not a sales ploy to make the vehicle more powerful, why not simply use the true kilowatt rating, which are the units of measurement used when testing? To my mind they don't use kilowatts because that figure is much smaller numerically and would look worse from a marketing perspective!
The original sales literature and specifications for the Murena, tested in kilowatts, gave the following standard ISO rated figures on the Certificate of Conformite (homologation paper):
1.6 model power 65.74 kW at 5,400 rpm; (incorrectly shown as 92 DIN hp)
2.2 model power 84.32 kW at 5,800 rpm; (incorrectly rated as 118 DIN hp) and the uprated 'Prep 142' rated at 101.4 kW at 6,000 rpm (or erroneously as 142 DIN hp)
2.2 S model (based on the 'Prep 142') 100 kW at 6,000 rpm; (wrongly advertised as 140 DIN hp)
The DIN horse power figures they gave as the equivalents are all wrong and overstated (again IMHO to enhance the apparent power figure) since they have used a conversion factor of 1.40:1 as you can work out, or see from the original Matra Automobile Preparation 142 document where they provided a graph of the power and torque figures. The 140 kW figure is shown the same as 100 DIN hp, showing the conversion factor used was 1.4 to 1, which is clearly incorrect. The true kW to DIN hp conversion should be 1:1.36 and their 1.4 conversion makes the engines appear more powerful than they are in reality. The 'Prep 142' conversion is named for a figure that was actually false! In reality it should have been a Prep 138 using the DIN figure. (Matra are not alone in this and for example the McLaren 720S is named for the PS horsepower it has, not the 710 bhp figure). You can tell the Murena power figures are false from one fact alone - The Prep 142 supposedly had 142 horsepower, but the Murena 'S' is also often claimed to have 142 horsepower. How could the two have the same horsepower when the two had recorded different kilowatt power figures?!
N.B. that the PS or DIN rating (or metric) horse power is 735.5W, and is not the same as bhp or brake horse power sometimes known as British horse power which is 745.7W.
So that you will know what to expect, the true horse power outputs are:
1.6 model: 89.4 DIN (or 88 bhp) 2.2 model: 114.7 DIN (or 113 bhp)
'Prep 142': 137.9 DIN (or 136 bhp) 2.2S model: 136.0 DIN (or 134 bhp)
Why was the 'S' rated slightly lower than the 'Prep 142' even though they are essentially the same? I'm not sure but there are minor differences between the original Prep 142 kit and a genuine S, including different distributors (there was supposed to be a new distributor in a Prep 142 kit, but I have seen a number of genuine Prep 142 including the one I owned, still using the original Bosch distributor whilst the uprated engine and all 'S' models should have a Ducellier distributor) and also the fact that the Solex carbs. for the Prep 142 were stated as ADDAE (and probably when measurements were taken) yet all the 'S' have the ADDHE version and these also have red plastic trumpets fitted which alters the intake airflow. It could also have been a slight difference in the measuring equipment or conditions at the time of testing.
They were still using the wrong conversion factor however, so any horse power claims are still erroneous. The fact that the Murena 'S' only really produces 134 bhp is another reason that you can run it on the standard down-draught Solex 34 CICF with no power loss but better fuel consumption. It didn't need the twin side-draught Solex 40's - they were fitted more for the appearance and noise than anything else! And I can confirm this as I have done just that, running an 'S' on the down-draught carburettor. (same performance, better fuel consumption) Finally if your Murena 2.2 has been modified with 'twin 45' size carbs. but only has the standard or 'S' cam, or even the original Holbay 58C re-profiled cam, then it will simply drink more fuel but you will not get more power just fitting bigger carbs!
In the case of the standard 2.2 Murena, its engine was the Tagora 2.2 engine only physically modified where necessary for the transverse installation. There were no performance modifications done and therefore it should have had a very similar power output. The U.K. Tagora workshop manual states the power of the 2.2 as 82.2 kW or 110 bhp (the correct conversion factor of 1.341 between kW and bhp was used by whoever produced the U.K. manual) and therefore supports the true Murena figure of 113 bhp since the different carburettor, inlet and exhaust manifolds, air intake and exhaust systems could easily account for the small 3 bhp difference.
With a decent camshaft profile, a 4-branch free-flow exhaust manifold, and alterations to the carburettor settings, the power of the 2.2 can be easily raised to 145-160 bhp which gives the car the power and performance it deserves yet still retaining its excellent drivability and fuel consumption figures. For years I have run a 2.2 with Holbay 58C cam, better exhaust but standard down-draught carb. and get a genuine 140 bhp and 31-34 mpg overall!
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This was last updated 31st August '21