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Static RPM for IO-360-A1A


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I’m wrapping up some major upgrades to my M20F.  I added an EI 30 P+C.  I have a couple issues with it.  During full throttle run up I got 2550 RPM.  Is that about normal?

 

The other issue is high fuel pressure.  Pressure is jumpy in the high 20’s and will hop up to 30.2 psi.  I don’t think it’s adjustable.  I know the pump is a new one from Tempest.

 

The plane is new to me and I am wrapping up the upgrades and can’t wait to start flying it!

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Someone else will have the exact number, but static rpm is supposed to be around 2600-2650.  Low pitch stops set ok?  There’s a thread about this from a few months ago.  It shouldn’t be the governor as the gov doesn’t control the prop until around 50knots on takeoff to hold 2700.  Is the tach correct?  Theres an app to double check it.

The new fuel pump will probably sit right at 30 (which is green/yellow cutoff) at the top of the pressure gage.  I changed mine 6 months ago and it did that on the ground.  No fluctuations though.  Maybe air near the pressure sensor?  In flight, mine is about 25psi.  Supposedly it will come down a couple psi as it wears in.

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Some recent engine OHs for IO360s were having difficulty with the mechanical fuel pump over pressuring...

There are threads around here that covered what to do next...

Messy data for fuelP gauges is often a set up issue...  air bubble in the right place, right size...

If you are using the EI gauge and getting messy FuelP data... we have an EI guy... @oregon87

PP thoughts only, not a mechanic...

Best regards,

-a-

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As someone who just recently had their governor ovehauled....

It could also be the high RPM set-screw on the governor that limits control cable travel. That one's pretty easy to investigate. +1 to get a second instrument (my IA loaned an optical tach) to verify how close the ship's tachometer is to reality.

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The new engine monitor is already using an electric tachometer, so the data is likely correct.

I’d start with backing the governor high speed stop screw out several turns to see if this brings the RPM higher.  Typically 1 turn of the stop screw represents about 25-30 engine RPM.

The older manuals were a little vague on static RPM, I’d be looking for 2650 static and 2700 on the take off roll.

Clarence

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I just installed the EI CGR-30s too.  Did you use the connectors they provided?  They are very problematic for me.  I am still chasing loose connections where those were used.  I feel like I get something else start fluctuating every flight.  Right now as I'm typing this my #2 CHT has stopped working.  I am slowly working on changing the connectors out to better connectors as they start failing.  I got fluctuating fuel pressure in flight too.  I went to replace the connectors and also found a really slow fuel leak.  Hopefully this helps any. 

As for the tach, I had some issue too; but I had also put on a new governor so I don't think I can offer any help.  I can tell you the EI tach is accurate.  It matches an optical tach almost perfectly.  As long as it's stable, you can trust it.  I'd say check your governor if you didn't do any prop work.

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EI tech support has been great.  They pick up when you call and have been most helpful.  I used the lower number resistor on the tach.  It is a bit jumpy below 1000 rpm.  I think I’m going to let it ride for a bit.  I tried not to use the EI wire crimps if I didn’t have to.  I did use them on the egt’s and don’t have any problem with that yet.  

I had the prop IRAN inspected and wasn’t sure if I was getting enough rpm static.  I fly from a 2400’ strip and want to be sure I’m getting full power.

Also did the 500 hr. Mag inspection.  I will do a compression check and verify the timing again.  Time to wrap the annual and fly.

 

 

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People tend to realize problems when upgrading from analog gauges to digital.  Could it have been like this previously and you are just now seeing the actual numbers?  Where any changes made to the prop/engine/governor/control cable  that would cause lower than normal static RPM?  Does the RPM increase on the takeoff roll to 2700?  What brand of propeller?

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If the indication is jumpy high, additional isolation should be added, or the existing isolator should be swapped for one of a larger value.  Conversely, if it is jumpy low or doesn't stabilize until higher power settings are selected, there may be too much isolation on the inputs.  I recommend verifying RPM accuracy with an optical tach just to put to bed the possibility of an instrumentation error.

In regard to troubleshooting fuel pressure, apply a known, regulated pressure and observe the instrument.  They should match and be relatively steady.  We always suggest to review the connections as a first step in jumpy indications.  Let me know what you find as I will be happy to help further troubleshoot if you think the issue is instrument related.

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Don't know where you are based but if you are at a high altitude airport that will impact the high RPM numbers due to lower HP available.

For your short airport DO check the RPM with another instrument (even a phone app would help) before you try flying. 

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