Engine runs rough with Turbo Engaged

[TNIndy]

I have a 67 M20F with a Rajay Turbo. I've owned the plane for a couple of years but haven't been using the turbo because of an oil leak in the turbo system. Long story......in summary I had the turbo bench tested, it tested fine and we ended up replacing a check valve. Now that the oil leak is finally fixed, I have been trying to use the turbo. The engine runs rough with the turbo engaged. I get boost and increased speed but the roughness is noticeable. Previously I assumed I was fowling plugs because of oil making it to the cylinders via the turbo.  

Also, I have an Electroaire system with Tempest fine wire plugs. The other four are massive electrode.

It doesn't seem to make a difference if I am running LOP or ROP

I appreciate any thoughts or suggestions

[tgardnerh]

Do you have an engine monitor? If so, what's the GAMI spread when it's running smoothly, and then what is it when it's running rough?
Do the cylinders peak in the same order with and without the turbo going?

Could you have an intake leak? I imagine that on an injected engine it could cause the affected cylinder to run lean when MP is less than ambient pressure, and rich when MP is above ambient pressure.


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[TNIndy]

GAMI spread is usually right at 1 GPH. I will have to see if the spread is more with the turbo engaged. I am getting GAMI injectors installed in August so that will improve. Cylinders do peak in the same order whether the turbo is engaged or not. I hadn't thought of an intake leak but we can easily check that on the ground. 

[tgardnerh]

Another question that might be revealing about whether its the turbo system or the higher MP is whether it runs smoothly with turbo engaged and partial throttle.
EG you go to 8k, note the MP and FF, throttle back to drop the MP by a few inches, close the waste gate to get MP back, and then re-lean to the same FF. If its still as rough as before then I *think* that would rule out any cause after the throttle.


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[LOCOLJ]

These systems are pretty simple, and they tend to run without too much trouble.  I would check the upper deck lines, and make sure they are connected and/or not broken, and check the air box where it is connected to.  There are some special seals for the injectors so make sure they are in good shape. If you are seeing good GAMI spreads during NA operation, I would  think a lower induction leak would show up there as well, and a leak at the airbox would show low boost not necessarily  roughness when the turbo is engaged.  I had quite a few leaks at the airbox and the turbo ran but did not have super good boost.

[M20F]

RayJays don’t have intercoolers so you are pushing really hot air into the cylinders.  You need to run really rich (I am almost 12GPH at 190). I don’t believe the electro air is approved for turbos and if it is variable timing you will have a bad day if you lose your manifold sensor.  That being said with unpressurized mags weird things can happen at altitude.  
 
What altitude are you noticing the roughness at?  Mine is pretty solid to FL190 and starts to get progressively wonky after that. 

[Fly Boomer]

12 hours ago, M20F said:

That being said with unpressurized mags weird things can happen at altitude

If the OP is at higher altitude when trying the turbo, this seems likely.

[Fritz1]

the electroair gives you up to 15 degrees of timing advance when MP drops below 24", engaging the turbo most likely drives the timing advance back to zero, this may explain some of the roughness, but probably not all of it, make sure you have the right plugs in the electroair, may need long reach plugs, I removed the electroair from my turbo engine, many pros and cons, among them timing advance hardly ever being used on turbo engine which runs above 24" all the time besides descent and landing

[M20F]

1 hour ago, Fritz1 said:

the electroair gives you up to 15 degrees of timing advance when MP drops below 24",

And when your manifold sensor breaks and drops to ambient when you are at 29” at FL190 it’s going to advance and you will have a bad day.  

[TNIndy]

On 7/16/2023 at 10:16 PM, M20F said:

RayJays don’t have intercoolers so you are pushing really hot air into the cylinders.  You need to run really rich (I am almost 12GPH at 190). I don’t believe the electro air is approved for turbos and if it is variable timing you will have a bad day if you lose your manifold sensor.  That being said with unpressurized mags weird things can happen at altitude.  
 
What altitude are you noticing the roughness at?  Mine is pretty solid to FL190 and starts to get progressively wonky after that. 

I haven’t tried it above 10,500. I’ll look back at my engine trends to see how rich I was running but I feel certain I wasn’t as high as 12 GPH. I appreciate your help

[TNIndy]

 

On 7/16/2023 at 9:16 PM, M20F said:

RayJays don’t have intercoolers so you are pushing really hot air into the cylinders.  You need to run really rich (I am almost 12GPH at 190). I don’t believe the electro air is approved for turbos and if it is variable timing you will have a bad day if you lose your manifold sensor.  That being said with unpressurized mags weird things can happen at altitude.  
 
What altitude are you noticing the roughness at?  Mine is pretty solid to FL190 and starts to get progressively wonky after that. 

My mechanic suggested that I swap out my remaining 4 massive electrode plugs with Tempest fine wire. All roughness is gone! Now I need to determine the correct mixture with the turbo engaged without CHT’s creeping up.