MatraSport Forum

Each model => Murena => Topic started by: Matra_Hans on August 06, 2014, 02:02:48 pm



Title: Rev counter signal
Post by: Matra_Hans on August 06, 2014, 02:02:48 pm
The rev-counter in the Murena: From where does it get the signal?
I am asking because I have installed a not original engine, and the rev counter connection from the new engine's ecu does not make the rev counter move.

thanks Hans


Title: Re: Rev counter signal
Post by: Bart_Maztra on August 06, 2014, 07:09:30 pm
Rev counter is getting the signal from the ignition coil. (the - terminal)


Title: Re: Rev counter signal
Post by: Matra_Hans on August 06, 2014, 07:46:40 pm
Thanks bart.
Too bad I have removed the original ignition system.

Hans


Title: Re: Rev counter signal
Post by: JL on August 06, 2014, 08:36:44 pm
Which engine are you using and do you run coil packs to provide the spark?
Regards
John


Title: Re: Rev counter signal
Post by: Matra_Hans on August 06, 2014, 08:54:32 pm
I am running a peugeot 505 Turbo injection engine (n9te) with a VEMS ECU and a Ford ignition pack (wasted spark) but I am sure that we can find a signal (from the ecu) for the rev counter.
Hans


Title: Re: Rev counter signal
Post by: Matra_Hans on August 06, 2014, 09:07:57 pm
You can see and hear the engine here: https://www.youtube.com/watch?v=ctYrQGqC9bM
hans


Title: Re: Rev counter signal
Post by: JL on August 06, 2014, 10:30:50 pm
OK, I think that I have read that you can take a signal from the supply to the coil pack that will run the older type of rev counter. I will try to find the article just in case I have been dreaming this!

John


Title: Re: Rev counter signal
Post by: JL on August 06, 2014, 10:38:33 pm
I think this was the thing that I saw:

http://trigger-wheels.com/store/contents/en-uk/d32.html#p129

Regards
John


Title: Re: Rev counter signal
Post by: JL on August 06, 2014, 10:48:20 pm
Also read this thread it may help you.

http://www.turbosport.co.uk/showthread.php?t=178208

Regards
John


Title: Re: Rev counter signal
Post by: Matra_Hans on August 07, 2014, 08:05:26 pm
Thanks John: That was some usefull links. :-)

Hans


Title: Re: Rev counter signal
Post by: Bart_Maztra on August 14, 2014, 06:46:46 pm
Thanks bart.
Too bad I have removed the original ignition system.

I guess there still is a coil? Then hook it up to the negative terminal.


Title: Re: Rev counter signal
Post by: Matra_Hans on August 15, 2014, 06:59:25 pm
Hi bert: I am using a Ford coil pack and I am running a wasted spark setup i.e. the spark is fired during the compression stroke and an additional spark that is wasted is fired during the exhaust stroke. Therefore I have twice the number of sparks per revolution compared to a traditional distributer and coil ignition; consequently I will assume that the rev counter will show the double of the actual revolutions.
Hans


Title: Re: Rev counter signal
Post by: roy4matra on August 24, 2014, 09:00:36 pm
I am running a peugeot 505 Turbo injection engine (n9te) with a VEMS ECU and a Ford ignition pack (wasted spark) but I am sure that we can find a signal (from the ecu) for the rev counter.
Hans

If you are running a wasted spark system then usually the coil is a twin coil pack, so one 'half' of the coil pack is switched on and off but it fires two cylinders at that instant one of which requires the spark and the other that doesn't (hence wasted spark).  Then the next time it fires the other 'half' supplying the other two cylinders.

So the ECU is switching back and forth between the two coils in the coil pack.  The idea is that each coil has twice as long to recharge.  The Murena tachometer requires the signal from the negative side of a single coil which is something you are not going to get from the ECU you have as it is using two different circuits; and you cannot join the two signals without isolating them otherwise you would short the two circuits together.

However, if you took the switching signal from one coil and doubled the signal that should give you the required pulse rate to drive the Murena tachometer, provided the voltage was correct.

Roy


Title: Re: Rev counter signal
Post by: Oetker on August 29, 2014, 08:04:26 pm
Just a flash of the mind.
Isn't it possible to collect the puls from the spark plug cables with 7 windings wire around the spark cable picking up a inductive pulse.
You can switch the inductions parallel,
Some RPM gauges and fuel electronics can work wit that inductive signal.
Never tried it in a Murena.



Title: Re: Rev counter signal
Post by: northmurena on August 29, 2014, 10:54:18 pm
Hej Hans,

perhaps this can help ? ; http://shop.alfisti.net/Tuning-Styling/Alfa-164/Elektrik-Analyse/Digitaler-Tacho-Signalwandler::3466.html

It is made for speedometer but also for rev-counter and can be configurated.

Best regards
Kai


Title: Re: Rev counter signal
Post by: krede on August 31, 2014, 03:03:04 pm
If anybody has a suggestion as to the origin of the ticking sound coming from the engine (on the video) it would be much appreciated. We first thought it to be miss adjusted valve, but they appear to be fine.


Title: Re: Rev counter signal
Post by: Jon Weywadt on August 31, 2014, 08:15:04 pm
If anybody has a suggestion as to the origin of the ticking sound coming from the engine (on the video) it would be much appreciated. We first thought it to be miss adjusted valve, but they appear to be fine.
Do you have the original mexhanical fuel pump? That is a guess.
If you can get hold of a mechanics stethoscope you will be able to locate which part of the engine it comes from. Another possibility is to take a long screwdriver press the handle to one ear and the blade to different parts of the engine. It should be possible to find where it is loudest and thus where the problem lies.
Good luck..
/Jon


Title: Re: Rev counter signal
Post by: Oetker on August 31, 2014, 08:48:54 pm
Where is the video?


Title: Re: Rev counter signal
Post by: northmurena on August 31, 2014, 10:05:19 pm
@Hermann: That was/is on the first page. Had also to search for ;-)

https://www.youtube.com/watch?v=ctYrQGqC9bM


Title: Re: Rev counter signal
Post by: Oetker on September 01, 2014, 05:38:34 am
Sounds like valve or distribution but difficult to tell from a distance.
Like Jon said,
Try this or a screwdriver to pinpoint.

http://www.ebay.co.uk/itm/Automotive-Mechanics-Stethoscope-Sensitive-probe-Car-Engine-Diagnostic-Tool-Van-/160956630459?pt=UK_Diagnostic_Tools_Equipment&hash=item2579c345bb

Herman



Title: Re: Rev counter signal
Post by: Jon Weywadt on September 01, 2014, 10:06:32 am
Sounds like valve or distribution but difficult to tell from a distance.
Like Jon said,
Try this or a screwdriver to pinpoint.

http://www.ebay.co.uk/itm/Automotive-Mechanics-Stethoscope-Sensitive-probe-Car-Engine-Diagnostic-Tool-Van-/160956630459?pt=UK_Diagnostic_Tools_Equipment&hash=item2579c345bb

Herman


That is exactly the stethoscope I have.  ;D It works great.


Title: Re: Rev counter signal
Post by: krede on September 01, 2014, 08:01:47 pm
Oetker: The gear for the distributor was severely worn, with some small chunks of the gears missing (Hans perhaps you can post a picture of the gears?) but I cant see how it could make such a noise.


Title: Re: Rev counter signal
Post by: Oetker on September 01, 2014, 08:26:13 pm
Yep.saw it before.
(https://lh6.googleusercontent.com/-18BErirW3-k/VAS5-Z1UiZI/AAAAAAAAFHg/0ae64vMLjiE/s771/distri.jpg)
Expencive gear.

Edit,
The gear is  to soft.
Especialy done to spare the camshaft in worst case scenario.

Herman


Title: Re: Rev counter signal
Post by: krede on September 01, 2014, 10:15:06 pm
That looks exactly like the one from the engine on Hans engine. Let's hope we have found the cause of the ticking sound then :)


Title: Re: Rev counter signal
Post by: Matra_Hans on September 01, 2014, 10:27:21 pm
my gear for distributor looks exactly The same (:-(


Title: Re: Rev counter signal
Post by: roy4matra on September 02, 2014, 05:28:25 am
(https://lh6.googleusercontent.com/-18BErirW3-k/VAS5-Z1UiZI/AAAAAAAAFHg/0ae64vMLjiE/s771/distri.jpg)

I have seen this before too.  It was in an engine where a valve had been sticking and the piston had been hitting it.  I suspect the damage to the gear was from the shock of the impacting.

So make sure all the valve guides are good and the valves nice and free.

Also make sure you have cleaned the engine out thoroughly to get rid of all the broken hardened bits from this damaged gear.

Roy


Title: Re: Rev counter signal
Post by: Oetker on September 02, 2014, 01:49:57 pm
Is it hardened?
I can easy file/rasp a bit of the tooths.
It's porous.

Herman


Title: Re: Rev counter signal
Post by: Matra_Hans on September 02, 2014, 06:35:12 pm
Hi all.
This is my distributor drive. It looks exactly like the picture posted by Herman. But I have to my knowledge not had any blocked valves or similar as mentioned by Roy.
Luckily I do not need the distributor as I have installed a trickerwheel

Thanks to all of you for your comments and assistance.
Hans


Title: Re: Rev counter signal
Post by: Oetker on September 02, 2014, 06:44:23 pm
The damaged one from my picture came from a good running S.
Also no Valve trouble.
Thats why I think  it's the gear itself that's  not up to the task or as they told me made that way to protect the camshaft gear.

Herman


Title: Re: Rev counter signal
Post by: roy4matra on September 05, 2014, 10:09:19 pm
The damaged one from my picture came from a good running S.
Also no Valve trouble.
Thats why I think  it's the gear itself that's  not up to the task or as they told me made that way to protect the camshaft gear.

Herman

I would be surprised if it was mild steel, as it simply would not last and any swarf from the wear could get in to the engine.  So I suspect that even if it is softer than the camshaft gear to protect that and be sacrificial itself, I would still say it must be slightly harder than normal mild steel, and I would still want to clean out the complete engine to make sure there are no bits left in that could cause problems later.

Also if it were plain soft steel, then on the engine I worked on where the valve had been hitting the piston, I suspect the damage would have been different to what it was, but I can't say for certain.

If nothing was causing this damage on other engines, then why do some engines have the problem and others do not?  Quality of oil maybe?  Another reason to use the best full synthetic, as far as I'm concerned.

Roy