Aftermarket turbo delema.

[bbakerco]

Hello all,

My J has an aftermarket turbo normalizer setup from a now defunct company. The system has a line that goes from the inter cooler to the fuel pump that was modified by the company to accept the line at the top of the fuel pump. See photo.  On the documentation, it’s called deck pressure sensor outlet and appears to put additional pressure into the crankcase. In overhauling the engine, I have a new fuel pump that is different than the old one and of course not modified with the above mentioned outlet.  The old fuel pump is 29 years old. So the questions are; since the system is a fixed wastegate, what is that line doing? Is it common on these types of systems. Is it necessary?  Is there an expert that knows about these systems?  We are struggling with the engine swap at this point. Thanks for any input.  

[FoxMike]

You need have the fuel pump referenced to the deck pressure.  I would not install a new fuel pump unless it had provision for a pressure line.  I bet your mechanic has already told you this.  If he has not it would be best to find a new mechanic.

[M20F-1968]

The reference line is needed.  These fuel pumps are difficult to find as cores.  Rebuild your old one.  I have used Aircraft Accessories of OK in the past.  I am sorry to say their quality control may have decreased (I'll leave it at that).    Quality Aircraft Accessories may be an option.  

John Breda

[EricJ]

Upper deck pressure is the intake air pressure after the turbo at the inlet to the fuel metering system, so the intercooler, especially its output, is an appropriate place to tap or sense that pressure.   Sending it to the fuel pump provides a means to reference the actual intake pressure rather than ambient to control fuel flow a bit better.

 

 

[smccray]

Paging @KSMooniac.  Not sure if that's the same system Scott is familiar with, but I'd bet he can help with this.

I can't help at all with the system, but I am familiar with fuel pump issues with a TN system.  I had fuel vaporization issues last summer with my bird climbing out of Houston in the summer traced back to an old fuel boost pump that needed more pressure.  Good engine monitoring made it a non issue, but the fuel system is a big deal here.

[bbakerco]

Further research and guru consulting has illuminated me to the fact that the upper deck sensor inlet is to provide additional pressure to the system for flying at higher altitudes.  Without it, the fuel pump diaphragms would cativate not provide sufficient fuel pressure.  The line from the intercooler provides back pressure to the diaphragms to keep them from cativating.  Probably part of the reason for the service ceiling increase with the system.  Found out that Tempest Aero Group can rebuild the fuel pump but because no cores exist (checked a number of places), I have to send in my existing core for rebuild.  $1,100+. ouch.   The one thing that I don't know yet is if, with a standard fuel pump in use until the rebuild if it would be an airworthiness (safety) issue or just a reduction in limitations.  I suspect that it would be both.

[N201MKTurbo]

5 hours ago, bbakerco said:

Further research and guru consulting has illuminated me to the fact that the upper deck sensor inlet is to provide additional pressure to the system for flying at higher altitudes.  Without it, the fuel pump diaphragms would cativate not provide sufficient fuel pressure.  The line from the intercooler provides back pressure to the diaphragms to keep them from cativating.  Probably part of the reason for the service ceiling increase with the system.  Found out that Tempest Aero Group can rebuild the fuel pump but because no cores exist (checked a number of places), I have to send in my existing core for rebuild.  $1,100+. ouch.   The one thing that I don't know yet is if, with a standard fuel pump in use until the rebuild if it would be an airworthiness (safety) issue or just a reduction in limitations.  I suspect that it would be both.

Wow, mine was only $900 a year ago. 
 

Call @tomgo2 he handled my overhaul. He sent it to the guys you tried, but he gets a discount.

Edited December 15, 2020 by N201MKTurbo

[carusoam]

8 hours ago, bbakerco said:

Hello all,

My J has an aftermarket turbo normalizer setup from a now defunct company. 

Not sure how defunct it is, call it semi defunct, or partially defunct... but TomGo is our go too guy for TN systems used with the IO and O360...

The part about getting a new system is the defunct part...

Servicing an existing system is the alive part...

It really helps to have a mechanic that is familiar with these systems... they can wear in really subtle ways.  Really obvious to the right mechanic standing in front of it... nearly impossible if it requires the pilot to explain it by typing... 

We have another recent example of that around here...

Yes, it would be nuts to fly with the wrong fuel pump installed... picture logging in from the FLs.... gents, about that fuel pump...

Try to become familiar with your system, while it is apart... what the upper deck pressure is, how it gets referenced... where that line goes... what parts get dirty from exhaust... and why mouse milk is used... what it is, where does it go, and how often it gets used... How fixed is your waste gate really?

PP thoughts only, not a mechanic... I don’t have a TN...

Best regards,

-a-

[tomgo2]

Hi there. I believe we spoke with Mr. bbakerco earlier this week. M20 Turbo, Inc. is a different STC than those developed by RAJAY. However, many components used by M20 Turbo STC originates from the RAJAY STCs.

It sounds like the M20 STC uses a RAJAY fuel pump. I believe the OP has come up with a workaround.

Regards,

Tom