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#1
03-19-2017, 06:59 PM
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280SE 3.5 Ignition Timing Problem
Hi everybody,
I'm experiencing with timing problem of my M116.980 engine. After replacing my original camshafts which has code number 46/47 with 52/53. Engine started running unstable at idle. When I move distributor to advance position,engine become more stable, if I move retard position engine becomes unstable. Therefore,when I check valve timing specifications of Camshafts 46/47 and 52/53 I realized that they have different timing values, For camshaft having code 46/47, Inlet Valve opens BTDC at 19 degrees closes ABDC 53 degrees, Exhaust valve opens BBDC 42 degrees, closes ATDC 20 degrees For the the camshaft 52/53, Inlet valve opens BTDC 26 degrees and closes ABDC 44 degrees, Exhause valve opens BBDC 60 degrees and closes ATDC 14 degrees So, could you please tell me why there are 3 different camshafts each has different valve timings for M116 3.5 engine. Secondly, Can I correct my current valve timing values which 52/53 currently installed to 46/47 by replacing woodruff keys with specific offset to each camshaft gear? If so, could you please tell me offset value? Finally, according to the valve timing values, which camshaft provides more compression? (If available, or any relation) Thank you very much for support and information in advance.. Regards, Kutluhan 
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#2
03-19-2017, 09:06 PM
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Quote:
(2) Retarding the 52/53 cams by 6-8 degrees of crankshaft angle will bring them closer to the 46/47 timing, however there will be a slight loss of torque. (3) Try setting the idle ignition timing by this method: Connect a vacuum gauge to a fitting that goes directly into the intake manifold. Disconnect any vacuum lines from the distributor. With the engine idling, rotate the distributor to the position that yields the greatest vacuum reading on the gauge. Check that total mechanical/centrifugal advance does not exceed about 36 degrees (without vacuum). The cam timing figures which you have provided are for seat-to-seat valve movement. The figures that are commonly used for comparison and for adjustment are those obtained with the valve 2mm off the seat. In the case of 2mm valve lift, 46/47 inlet duration is 192*, 52/53 inlet duration is 190*, and both have exhaust duration of 194*. Cam centerline angles are: 46/47 > 104*, and 52/53 > 106*.
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#3
03-20-2017, 11:04 AM
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Thank you very much Mr Frank about your reply and detaied information, So regarding to the information you provided, 52/53 camshafts give better performance than earlier 46/47 due to having greater compression pressure ( as intake valves close earlier). I will try to adjust idle like you explained in #3. Because, when I press accelerator at idle, unstability dissappears. But what I noticed, after car warms up, when I remove socked of air temperature sensor which is on the air filter inlet was not have any effect at idle speed however before, idle speed was dramatically lowering at the time of socket removal. This made to think that air temperatur sensor working properly. Please correct me if I m wrong. ( By the way my all sensors are new,water temp,air temperature, idle speed adjusting,..)
Currently, distributor is too much on advance position than before. Almost adjusting screw is closer to end of distributer mounting bracket guide.Is it normal? Finally, as a performance, after setting up ignition by your method, can I have any difference than before? With camshafts 52/53 better tahn 46/47? Because I will not follow step 2 due to having tork loss as you stated. By the way there are various ignition distributors for m116 3.5, which I have currently on is 0231402004. Do you think they all have different inner shaft lobes ( slight differences Between)? Because many distributor numbers. I don t know what changes? Best Regards, Kutluhan
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#4
03-20-2017, 02:21 PM
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(2) With a change in cams there will be a need to also re-adjust the idle mixture (air/fuel ratio). The idle mixture screw is on the side of the engine control unit (ECU). When the throttle plate is closed at idle, and the throttle position sensor and the closed throttle switch signals the ECU that the throttle is closed, the mixture is controlled by the idle mixture screw. As soon as the throttle is opened enough to open the idle switch, the mixture control is changed to the manifold pressure sensor. By alternately adjusting both the idle mixture and the idle ignition timing, you should be able to achieve a smooth, steady idle.
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#5
03-21-2017, 03:50 PM
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Thank you very much again for brief explanation. I will purchase ignition timing light gun plus vacuum gauge tomorrow to start adjustment.
After adjusting distributor without vacuum hose attached( at the point where I read highest value on vacuum gauge and total advance is about max. 36 degrees as you stated). Do I also need to adjust advance with vacuum hose attached? Also my current breaker point gap is around 0.035? Should it be 0.04 like all L6s or its ok? Thank you very much in advance.. Regards, Kutluhan
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#6
03-21-2017, 07:49 PM
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(2) Set the breaker point gap to .38-.39mm (.014-.015inch), not .035, or .04!!
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#7
03-23-2017, 04:01 PM
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Today I adjusted ignition timing regarding to the values you stated ,
Around 3400 rpm with vacuum attached, advance is 35 degrees At 800 rpm with vacuum , 6 degrees after TDC( value from book)? And my idle becames more stable. Thank you very much. Also about breaker point gap, I wrote wrong instead .35mm I wrote, .035. Currently I adjusted as .40mm.Because, I dont have any feeler for more sensitive adjustment. By the way, how can I adjust transmission ****ing durations ? During full acceleration, 1-2 at 60km, 2-3 at 90, 3-4 should be 150. Till 2-3 ok but mine shifts at 130km (instead 150)? If possible , Can I extend this ****ing duration to original state? Thank you very much. Kutluhan
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#8
03-23-2017, 05:53 PM
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Quote:
Quote:
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#10
03-24-2017, 02:36 PM
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The two things that most affect the shift speed are control pressure (throttle link pressure), and governor pressure. Either a greater control pressure, or a lower governor pressure, will cause a shift at a higher speed.
Both the control pressure, and to a small extent the governor pressure, are also affected by the modulator pressure. Increasing the modulator pressure will cause the shifts to become firmer/sharper/harder, but until the shifts are too firm, an increase in modulator pressure will raise the shift speed. Before changing the modulator pressure, try increasing the control pressure by shortening the link from the throttle to the arm on the right front of the transmission. Shortening that link will also affect the 1-2, and 2-3, shift points. With a 3.92 axle ratio the 3-4 shift would occur at 130KPH.
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#11
03-24-2017, 03:30 PM
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Thank you very much again for detailed expression. As you stated, I will start by shortening throttle arm linkage.If I will be able to achieve shift from 3-4 at 150km I will not go on with governor pressure. Othervise Work is little bit more complicated) I think some info exist about governor pressures on service book. Tomorrow I will try to adjust and write results. Also I will recheck ignition timing at 3500 rpm without vacuum and set 35.
Thank you very much again
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