RAM air removal

[PTK]

How many folks have removed the RAM air opening in the J. Looking to be painting in the next few months and thought I should clean up the cowl.

[jetdriven]

ours was removed before we bought it. They put a blocking plate inside the cowl and left the hole.

[bnicolette]

Doc.......I have yet to open mine in flight and now am curious how much it really helps on the "J".  I have heard it doesn't help much, but like I said, I have never opened mine so I have no first hand knowledge of it.  Have you tried yours and how much did it boost the MP?  Just curious.

[PTK]

Quote: Bnicolette

 

Doc.......I have yet to open mine in flight and now am curious how much it really helps on the "J".  I have heard it doesn't help much, but like I said, I have never opened mine so I have no first hand knowledge of it.  Have you tried yours and how much did it boost the MP?  Just curious.

 

[PTK]

Quote: JimR

Mine gives me about 1/3" of manifold pressure.  Maybe less.  I used it a bit right after I bought the plane but haven't used it in years.  I'd like to and will eventually get rid of it, but there hasn't been a reason to mess with it yet.

Is it legal to remove it per the service bulletin or instruction with the exception of re-fiberglassing the cowling, like Byron's apparently is?  Assuming that you extend the baffle seal all of the way across the bottom, I don't see how having the hole there will hurt anything.  If anything I would think that it would provide a bit of additional cooling airflow at the expense of a bit of additional cooling drag.  But is it legal?  I'd like to get rid of it but not have to mess with the cowling until time for paint.

Jim 

[jetdriven]

The SI 20-93 says the hole must be plugged, then refers to aceptable practices and techniques, fiberglass repair section.  I would counter that putting a metal plate on the rear of the hole constitutes an acceptable repair, the hole is blocked in th same configuration as it would be if it had ram air installed.

[201er]

I don't understand the point of removing an unharmful functional device on the aircraft. It's not like you'll gain any speed by closing it. However, I do consistantly get a 1/4" boost in MP as suggested. My point is why not? When you're in clear air and not a cloud in sight, that's a couple HP improvement for nothing. This may reflect in a couple knots. Guys spend thousands of dollars trying to optimize their speed and improve by a few knots (not to mention any names, Brett) and then overlook a device already included for it. Generally I'll be reminded to open the ram air when I am climbing through 3-5000 and losing MP. If I'm in the clear I'll go ahead and keep it open for the rest of the flight. If I encounter clouds or suspicion of contaminated air I'll close it. Then when I am ready to begin my descent, I will make my first power reduction by closing ram air before any other. It's not much but why not? Surely the push/pull of a lever is worth the extra speed when MP is at a premium at altitude as it is.

[201er]

^That's very intesting. I've never thought of it that way. Does anyone know if there is a net speed increase or decrease between flying the 201 with ram air vs its removal? Perhaps our resident physicist could do the calculations and just give us the result?

[jetdriven]

I have also read its ~1/4" of manifold pressure and if 25" means 150 HP, 23" is 135 HP (given 2500 RPM, ROP) then another 1/4" might net you ~2 HP, that might get you either another .02 GPH and <1 knot TAS (ROP), or ~10 degrees more LOP on the same FF and speed.    

Now on the pre-J models, it's a really large boost and I would keep it despite the costs.   

Jim, when they removed my ram air they did not change the weight and balance.  Do you have any data? I could use a couple pounds added to my 974 lb useful load.   

[KSMooniac]

My ears were ringing!

Yes, I removed my system per the Mooney instructions when I had my plane painted in 2009.  The paint shop fiberglassed the hole and painted it so there is trace of it on the outside, and after I got the plane back I removed the butterfly valve, seal, and cable and riveted a piece of aluminum over the hole in the induction box.  Removing the cable was a major PITA due to contortionist requirements under the panel to un-thread that cable, and then plug the hole with a bolt, nut and big washers.  I didn't have a good enough scale to precisely weigh everything, but it is in the 1-2 lb range. My AI and I chalked it up to "negligible" and figured it would offset other "negligible" additions from other changes over the years.

I agree with just about the consensus above.... doesn't *measurably* improve anything on the J besides a slight wiggle in the OEM MP gauge.  Less than a wiggle on fuel flow and airspeed.  I looked into replacing that little seal that is made out of baby seal hides or something similar during my first owner-assist annual, and then I went the RTV patch route until I could remove it.  On the pre-J models it is DEFINITELY worthwhile, but on the J they did such a good job with the induction system that it is not needed, and the best evidence of that is the fact that Mooney removed it in later years.  The benefits in my mind are sleeker appearance, cost-avoidance by ditching that expensive seal, one less push-pull cable to maintain, and a very slight gain in useful load.  I would recommend it to any J owner, especially if they're planning on a new paint job.