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Author Topic: 2.2 dip in acceleration.  (Read 21232 times)
Oetker
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« on: April 14, 2008, 08:42:27 am »

Driving my Murena at 2500 rpm I notice a dip in acceleration when I floor the pedal.
The car hasitate for a second and then accelerate ok.
Carb, sparkplugs cables is new, and ignition is adjusted at 9 degree before udp.
Al vacume is controled and ok.
I think the carb need some adjustment but have no idea where to do it.
Any idea how to tackle this?
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I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
Anders Dinsen
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« Reply #1 on: April 14, 2008, 09:56:25 am »

Is the accelerator pump working properly? It is driven by a linked lever on the left side of the carburettor. There's a small adjustment screw between the two parts of the lever allowing you to set how fast the pump diaphragm is operated when the throttle is opened.

Start with that - as the carb is new, it may be adjusted incorretly.

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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Oetker
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« Reply #2 on: April 14, 2008, 10:06:16 am »

I know that works ok but I wil try to experiment with that first.
The last ower puted the new carb on, but have no idea how well he adjusted it.
All settings I have done sofar are by hearing and smelling and looking at the smoke of the exhaust.
Apart from the accelration problem the car runs fine and uses 11 km/litre with easy driving.
Color of the bougies are fine, light brown so not to lean or to rich.
I tought the adjustment of the accelerationpump is only for low rpm when driving off.
Will try out.
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I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
Anders Dinsen
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« Reply #3 on: April 14, 2008, 11:30:43 am »

I know that works ok but I wil try to experiment with that first.
The last ower puted the new carb on, but have no idea how well he adjusted it.
All settings I have done sofar are by hearing and smelling and looking at the smoke of the exhaust.
Apart from the accelration problem the car runs fine and uses 11 km/litre with easy driving.
Color of the bougies are fine, light brown so not to lean or to rich.
I tought the adjustment of the accelerationpump is only for low rpm when driving off.
Will try out.

With that km/l number it sounds like the carb is perfect overall, so that's good.

I googled for accelerator pump and this came up:

"When you open the throttle, the airflow increases immediately but the fuel (being more dense than air) takes a moment to catch up with the increased airflow. This would result in a lean mixture for a few moments (the car would hesitate), so the carburetor has an accelerator pump built into the side of it which supplies a shot of fuel to ensure smooth acceleration. The accelerator pump connected by a linkage to the accelerator; when acceleration is required, the pump squirts a spray of fuel directly into the throat of the carburetor to momentarily increase the fuel-to-air concentration."

source: http://www.vw-resource.com/accelerator_pump.html

I think that more or less answers your question: the pump is needed throughout the rpm range.
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Oetker
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« Reply #4 on: April 14, 2008, 12:23:46 pm »

Ok, thanks Anders.
I try to experiment a bit with the acc.pump adjustment.
Think it wil be the problem.
Its a matter of balance to keep it as low as possible but also have power right away when you put youre foot down.

regards Herman
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I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
roy4matra
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« Reply #5 on: April 17, 2008, 04:14:04 am »

Driving my Murena at 2500 rpm I notice a dip in acceleration when I floor the pedal.
The car hasitate for a second and then accelerate ok.
Carb, sparkplugs cables is new, and ignition is adjusted at 9 degree before udp.
Al vacume is controled and ok.
I think the carb need some adjustment but have no idea where to do it.
Any idea how to tackle this?

If the carb. is new, make sure it is the correct one.  There have been a number sold by HB Pieces (or it might have been when it was still Delcourt) that are similar but they are actually wrong.  This may be the cause of your problem as these are fixed jet carbs. which means there are no adjustments except idle mixture and revs.  It could have a fault with the pump jet or feed but check those numbers first.

Correct carb. numbers are on my FAQ pages.

Roy
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Oetker
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« Reply #6 on: April 17, 2008, 07:34:38 am »

I have no record of where the carb comes from but try to find out what is mounted.
Its the last problem concerning the engine.
Apart from this problem it runs perfect.
Made a test drive this week, about 400 miles, and it was a real pleasure.
This was the longest drive since 1990 for the car.
Since that time it did only 200 miles a year.
Still a lot of small jobs to do, but I didn't pay the world for the car €4000 and it was with mot (NB: its taxfree in the Netherlands).
Thinking about GPL, and then is the carb not so impotant.
Ther is a firm overhere that has build it in a 2.2 Murena and it increased the power to S spec.

http://www.iwemalpg.com/Matra_Murena22.htm

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I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
Oetker
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« Reply #7 on: April 05, 2009, 08:42:47 am »

Finaly found the solution to the problem.
During experiments I noticed that if I have the ignition 10 degree before UDP, there is the sound of premature detonation during acceleration.
Last week I picked up a new distr.cap and rotor at Car-joy for the 2.2.
They didn't fit Huh
I removed the ignition to see what was mounted.
It took me 2 hours to get it of Sad
This was the ignition mounted.



After some researsch, I found out this is a systeem for a Tagora.
Searching the box with spares, I found this one.

This is a Bosch 0237002069, wich is the right one for the 2.2.
Why is this in the box with spares, and not on the car?
Mechanical it was ok, and the Hall sensor works fine.

I puted it on the car with the new rotor and cap, and after some adjusting on carbs, this was the result.

http://www.youtube.com/watch?v=f6b1P7eakSk

In driving I have the feeling I gained 30BHP.
The car is very responsive, and for the first time since I own the car I have the feeling it is ok.
Think Tagora ignitions don't belong on the car, no matter what people tell you.
« Last Edit: April 05, 2009, 09:04:55 am by Oetker » Logged

I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
krede
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« Reply #8 on: April 05, 2009, 02:34:39 pm »

Great job on finding the error..

But..
Seriously SERIOUSLY!! you need to think of a different solution with your air filter!!!
It is mounted at the worst possible spot!!
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Oetker
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« Reply #9 on: April 05, 2009, 06:38:28 pm »

Yep, I know.
It was puted on during experiments.
It is a hororable color to.
Wil bring it more down with some tube, and change it to black one.
Since the old filter is out there is lots of space.
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I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
Anders Dinsen
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« Reply #10 on: April 14, 2009, 12:30:58 am »

Think Tagora ignitions don't belong on the car, no matter what people tell you.

Glad to hear you found the problem. Ignition is at least as critical as carburation! But I find it odd that the Ducellier couldn't do the job and that you had pinking with it advanced to 10 degrees. This distributor must have failed - one of the advance springs could be broken causing it to go into max advance too early? There may be small performance differences between the Ducellier and Bosch dizzy's depending on the carburettor and state of engine tuning, but these should be small.

And if you think about it, the Tagora ignition should work just as well as anything else fitted on that engine. The carb is different, but this is because the engine is rotated in the Murena and the direction of travel on the carb has to be correct for it to work correctly during acceleration and cornering.

Have you checked the Bosch distributor? You can do it with it on the car, but you have to remove the pickup coil to get a look. It's also a good idea to lubricate the parts down there so they won't seize up. I have a few photos of the internals of the Bosch here:

http://gallery.dinsen.net/v/biler/Matra/technical/carb/dizzy/

/Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Oetker
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« Reply #11 on: April 14, 2009, 11:06:34 pm »

Indeed it's strange.
I took the Ducelier/Tagora apart and couldn't find anything wrong with it.



I can have no other conclusion then something has to be different compared to the Bosch ignition.
I still have pinging if I adjust to 10 degree before UDP.
I only hear it if I put my feet down to the floor.
If I keep it between 8-9 no pinging.
I use 98 superplus but if I put octane booster pil in, pinging is less.
Car is running smooth now, and before I changed ignition it wasn't
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I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
Anders Dinsen
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« Reply #12 on: April 15, 2009, 08:15:21 am »

Nice photos. It looks a bit rusty, but if the parts are moving freely, that shouldn't be much of a problem. Except that the rusty parts indicate poor maintenance. These parts should be oiled to prevent sticking.

It sounds like something else might be wrong when you have pinking even with a good dizzy and 10 degrees static advance. I'm running 15 degrees static without any pinging on 98 RON.

Have you checked advance as revs increase? Are the plugs correct? Do you trust your advance light?

Carbon fouling in the combustion chamber could also be a cause of the problem.

/Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Oetker
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« Reply #13 on: April 15, 2009, 09:11:46 am »

When I bought the car 1.5 year ago not much was driven with it.
Since 1990 only a few thousend miles.
I suspected carbon and puted in a horsepill to clean it (brakefluid).
I changed the sparkplugs to BP6ES (adjusted 0,6 mm distance).
Last year I drove 5000 miles, mostly on the highway, so I presume it is clean now.
The sparkplugs look light brown so not to lean or to rich mixture.

The Ducelier looks rusty, but anything works like it should.
Mayby the weights or springs are different., I don't know, all I know is that the car runs a lot better.

I am not shure what you mean with advance, but I adjusted ignition with a strobo light.
Od thing, the car pings the most on Shell V power.
Are they using methanol dopes in the product?
For the time being it works ok, but I am thinking to put the car on GPL, because the future fuels will kill the engine.
« Last Edit: April 15, 2009, 09:15:46 am by Oetker » Logged

I feel like Jonah, only my fish looks different.
Murena 2.2 Red 1982. Murena 1.6 black on places.
Anders Dinsen
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« Reply #14 on: April 15, 2009, 10:58:10 am »

Strange about the Ducellier dizzy. The curves are slightly different, but not much. It could be the wrong dizzy? But why bother - you have a good one now!

I meant stroboscope, yes.

Also strange about Shell V Power, which is what I run too. V Power is rated 99 RON here in Denmark. I also run 98 RON from a local station. Only few stations have anything higher than 95.

I don't worry much about fuel availability. I think we will be able to find 98 RON for some time to come for old hobby cars! Wink

/Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
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