02-01-2018 01:33 AM
01-29-2018 09:15 PM
01-29-2018 08:48 PM
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.
01-29-2018 04:33 PM
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.
11-25-2017 01:07 PM
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.
11-25-2017 12:20 PM
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?
11-24-2017 11:09 PM
11-24-2017 11:06 PM
11-24-2017 10:55 PM
The A4 uses a different wastegate than the A3, but is similar in construction. The A4 is running about 10 psi more inlet manifold pressure and is running hotter exhaust temps than the A3. So I think the A4 WG environment is more severe than the A3. If you had that long a WG life on the A3, then I say you are the exception. Most customers had to service the A3 WG from 5K-8K hours. I had one customer who said he could set his calendar; WG service right at 5K hrs, just like the OMM. And your A4 are at 3K. The A4 OMM says Inspect the WG at 5K hrs, just like the A3.
If the WG stuck any, it would certainly affect the NOx as the ECM is using the air flow to maintain air fuel ratio against the required fuel flow to maintain desired engine speed. And this may just be telling you what the service interval might need to be at your site conditions, since you found another WG stuck.
11-24-2017 10:27 PM