Chris,

 

The A controller which has the temp probe will run different that the B controller without one as you might expect.

 

The B controller is probably calculated for a “Standard sea level day” temp like 59.9 F.  So if the A controller is seeing a colder temperature than the standard day, it would generally have more fuel flowing to compensate for the denser (colder) air than B controller.  That means you might need to enrich with the B controller to compensate for the denser 47F air you are encountering.  So I don’t really see any thing to be concerned with at this point.  Now if there  is an extreme difference then there could be an issue, but I don’t see one otherwise.

 

Ed

 

 

Good progress today.  Bottom line is I found that one of the temp probe wires was disconnected.  While looking into everything, I also swapped the two vacuum leads at the EC2, just in case there was an issue with one of them (like it was pinched or cut) but that had no effect.  I have also reset all modes of the EC2 (1,2,3,4,6,7&8).

 

Now both A and B run the engine without surging, then only difference is that I need to set the mixture a lot leaner for A and richer for B with the OAT at 47*.  I assume that is normal, but don’t really know. 

 

I think my next step is to start tuning the EC2 again.

 

CHris

 

 

Could you provide more details, Chris.  RPM where surging occurs, manifold pressure, staging point, etc.

 

Most of the time if you have a surge it is caused by the engine encountering a leaner region at higher rpm.  This causes the engine to die back until it hits a richer region, where it again picks up power and increases rpm into the lean regions, repeat ad infinitum.

Here are some possible causes (assuming the A controller is really OK):

 

 

1.  The A controller may simply have its MCT set too lean at some higher rpm.  When you enter the surge region, try enriching your mixture by turning your manual mixture knob to the right.  IF this improves or increase the rpm at which the surge occurs then I would suspect a MCT table needs enriching.

 

2.  If the A controller had a restriction in its manifold connection/line then it may not see the increase in manifold pressure (and thereby enrich the fuel mixture) soon enough to make the adjustment and the engine runs lean.

 

 

3.  One set of your injectors (most likely the secondary) are not turning ON as they should.  However, with most engines with near equal size injectors in primary and secondary, the engine should run up to 6000 + rpm on just one pair.

 

4. Its possible you have some sort of fuel restriction but the fact that it runs OK on the B controller would seem to indicate that is not the problem in this case.

 

 

Here’s a couple of other things you might try

 

1.       Try setting your “A” controller’s MCT back to the Default settings and see if that helps (check your manual on how to do this)

 

2.       Make sure the temperature probe for Controller A is not accidentally getting grounded.  The A controller will run without the temp probe connected, but not certain what problem it may see if it is grounded.  Best to check to make certain.

 

 

 

Let us know how it goes

 

Ed

 

 

 

I am still trying to get the engine to run smooth.  It has been surging on me.  With fuel pressure steady, the mixture and the RPM jump around a lot (I haven’t started taking exact readings yet, still trying to reduce/eliminate surging). 

 

Today I tried swapping around the vacuum lines, and as an afterthought, I selected the B controller, and the engine smoother out, and RPM jumped up considerably.

 

So I am wondering what the difference is between the two.  What are the extra things that A looks at that B doesn’t?  This will help me figure out a troubleshooting procedure.  Maybe I can isolate the faulty component.

 

I looked through the EC-2 manual and couldn’t find anything listed.  Maybe I missed it.

 

Chris

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