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Author Topic: How to make a correct adjustment of the ignition timing on the2.2?  (Read 1635 times)
variator
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-83 Matra Murena 2.2


« on: May 02, 2015, 12:34:02 pm »

I have assembled manifolds and sport exhaust on the car and after that it has begun shooting in the muffler when it runs downhill.
Requires this exhaust system another ignition timing, or is it the case that any misfire setting become more audible with the sport exhaust??
I know that it shall have 10 degrees pre-ignition, but should the ignition be measured by a particular rev. speed or should the vacuum to advancing mechanism be disconnected?

Cylinder no. 1 was the one closest to the flywheel?

Best regards
Terje
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2001 Saab 9-5 2,3T, 1981 Porsche 928, 1981 Honda cb 900 F, 1968 Triumph Trophy TR6R, 1986 Yamaha RD 350 YPVS
Jon Weywadt
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« Reply #1 on: May 02, 2015, 02:16:43 pm »

If I recall right I set mine to 10 degrees at 1500 rpm. i have had a few exhaust detonations right atribute that to a stuck choker and the fact that my new Holbay 58C cam has some overlap. Since replacing the choke cable, so it no longer sticks partly closed, I have had no more exhaust detonations. I have not adjusted the timing, so it is probably correct. I will, though, get it tuned precisely after I readjust the valve clearance. That will happen after I have driven 1000 km with the current settings.
Holbay power rocks  Grin and screw the gas mileage. Cool
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Matranaut par excellence Cool
GP
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« Reply #2 on: May 04, 2015, 09:04:52 am »

Just dugout my Autodata sheet trying not to wake up the household on this beautiful bank holiday Monday in the U.K. (Failed, oh farn!)

Basic Ignition timing with vacuum disconnected 10-12deg at 850 r.p.m.

I have twin sidedraught, sport manifold and sexy cam and have it set up on a rolling road with 12 deg. as this works best for me. I also have the vacuum advance hose disconnected permanently.

A buddy of mine had all the loud bangs and flames and eventually found that the new cam fitted had been fitted slightly out!
« Last Edit: May 04, 2015, 09:13:31 am by GP » Logged
roy4matra
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« Reply #3 on: May 06, 2015, 12:54:26 am »

I have assembled manifolds and sport exhaust on the car and after that it has begun shooting in the muffler when it runs downhill.
Requires this exhaust system another ignition timing, or is it the case that any misfire setting become more audible with the sport exhaust??
I know that it shall have 10 degrees pre-ignition, but should the ignition be measured by a particular rev. speed or should the vacuum to advancing mechanism be disconnected?

Cylinder no. 1 was the one closest to the flywheel?

Best regards
Terje

Ignition timing is 10 degrees BTDC idling (hot) with vacuum pipe disconnected.  Best idle I've found is 900 rpm but don't rely on the Tachometer in the car as they can be inaccurate.  No.1 is next to the flywheel as stated.

As a general rule popping in the manifolds can be due to mixture strength - too lean and it will spit in the inlet and too rich will cause popping in the exhaust.  However, check that the gaskets between manifold and head are air tight too.  A manifold gasket leak will also cause trouble.

Since every engine can be slightly different, sometimes you can get a better set up with the timing a degree or two advanced or retarded, and this is best done on a rolling road, but without access to one of those you could try it manually on the road.

Roy
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variator
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Posts: 95


-83 Matra Murena 2.2


« Reply #4 on: May 06, 2015, 10:40:38 pm »

Thanks for the answers guys!

It may seems like the car run a bit rich after I got rid of all vacuum leaks.
Which way will the adjustment screw on the carburetor be turned to get it to go leaner?

Which way is right can certainly be heard when idling speed increases?

Regards Terje
« Last Edit: May 06, 2015, 10:46:00 pm by variator » Logged

2001 Saab 9-5 2,3T, 1981 Porsche 928, 1981 Honda cb 900 F, 1968 Triumph Trophy TR6R, 1986 Yamaha RD 350 YPVS
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