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Trusted Contributor
Trusted Contributor

Re: G3606 A4 units

The G3600 A4 does generally run a higher exhaust temp upwards toward 1100 deg F; this hotter than the G3600 A3.  The biggest reason is the different combustion recipe on the A4.

 

If the NOx is swinging, be sure that the wastegate is not swinging.  This can make the afr swing, which will cause the NOx to swing.  I wouldn't be concerned with a swing of 5-7 ppm of NOx, especially when running at less than rated load.  If the wastegate is swinging, you might tweak the linkage a slight amount; I woud think no more than one turn either way, shorter or longer.  This might help; I would try shorter first. 

 

If the wastegate is still, then I would go through the NOx calibration procedure again and see if this helps.  

 

Best regards,

Al Hunt

New member

Re: G3606 A4 units

Question 3608A4 running in Northern Alberta high  cylinder temps. Customer says they are high at 1097F. I'm good with tuning 3600a3 and older. Still waiting on a course for 3600a4. Nox is wanting 50.00 and is running above and below that value. btu is 1042. load 78%. It's not flagging high temp alarm so not sure if its ok. Thanks

 

Pat M

Visitor

Re: G3606 A4 units

There are several A4 units in our area that have had W/G's seize in the last month or so. Doesn't seem to matter if the engine is an inline or a vee. It appears to be a clearance issue between the shaft and the bushing. Adding 0.010" clearance to the ID of the bushing once installed seems to have resolved the issues. Another contact of mine went the other way and turned the shaft down at the bushing contact area 0.010". Either way the result is the same. More cleance helps.

Contributor

Re: G3606 A4 units

Yes, sorry Al, I forgot you had mentioned that earlier. I will definitely look into the pressure and report back.

Yes, Cat did remove the dynamic adjustments of the wastegate and the choke but they added adjustement to the air fuel control which slows down both the wastegate and the choke. However, it never took the twitching away even when reduced to 10%. I started to wonder if the adjustment was just slowing the ecm down in making its calculations but not really changing the execution.

I guess I get to mess with them a little longer.
Trusted Contributor
Trusted Contributor

Re: G3606 A4 units

One thing you want to do is make sure the hydrax pressure is set correctly to 225 psi.  There is some thought that the higher pressure might contribute to the instability of the actuator.  I saw one on a G3606 this past week twitching a bit.  The hydrax pressure was set to 270 psi; reset it to 225 but don't know how it will affect the stability.  Couldn't stay on site very long.  Should be able to adjust the dynamics to settle it down but Cat took the dynamics adjustment capability off the wastegate; should put it back.  I am recommending that.

 

Best Regards,

Al Hunt

Contributor

Re: G3606 A4 units

Well, we have had the wastegate shafts replaced (awhile ago) and it helped remedy the NOx fluctuation. The only problem is, even when new, the wastegate was twitching a lot. I can't help but think the twitching is leading to failing wastegate shafts prematurely. I have not been to this particular site for about a month now but I will get over to it soon and see what is going on.

Trusted Contributor
Trusted Contributor

Re: G3606 A4 units

I don't have any inside info on the parts shortages.  About the only thing I can say is that either the parts needs orders were miscalculated or the vendor has had production issues.  It could be a bit of both.  There is a shortage of G3500 cylinder heads also, I hear.

 

Best Regards,

Al Hunt

Visitor

Re: G3606 A4 units

I agree with Al. If the W/G is sticking at all, even for 10 seconds, the air fuel ratio is not going to track well and the NOx will be thrown off. Once the W/G breaks free the control system is going to have to have to try and recover from this upset which may take a little bit. During this process the control may over compensate one way or the other causing the swing in NOx.

 

Al, do you know anything about the world wide back order on the A3 VTC and TPS W/G shafts?? are there issues with the shafts again?

Contributor

Re: G3606 A4 units

For awhile, we were pulling and rebuilding the wastegate anually but we were finding nothing wrong with them when we pulled them at 8,600 hrs. We now are only messing with them on an "as needed" basis. Nobody wants to mess with the blanket or the very unsafe position to remove them on our 3606s. It will be dissapointing if we have to repair wastegates every 2k on the A4's.
Contributor

Re: G3606 A4 units

Sorry, I wasn't as clear as I should have been. The unit I found the sticking wastegate is the same unit I started this thread about with the swinging NOx.

I was working on the unit beside this one when I heard it start struggling.

I have a short video of the wastegate twitching but I need to upload it before I can post a link. I will try to get to it tomorrow but I will have it uploaded the beginning of next week.