Intercooler Install

[Buster1]

Continuing my research on 231s and am liking what I find.  Though everything seems to point to heat problems leading to early overhauls with the GB/LB engines.  Some of the birds I am looking at don't have intercoolers, but some do.  Does anyone know much about getting an intercooler installed?

One article even says a GB/LB engine past 1000 hrs is on "borrowed time" due to heat problems that Mooney eventually solved with the MB engine which came with an intercooler.  http://www.mooneypilots.com/mapalog/mapalogarticle.html

[N9937c]

My lb is at 1967 sfrm and has never even had a cylinder off. 1 quart of aeroshell in ~20 hours.

Is intercooled and speedbrake equipped but no gami's. Usually run ~65% at 160 true.

[jlunseth]

We had terrible heat problems with my 231 when I first picked it up and flew it back to Minnesota.  It turned out to be a combination of things, all very bad maintenance by the owner and/or bad work by maintenance shops.  The fuel system was I think the biggest problem, it was not putting out the 22-24.5 GPH needed to keep the engine cool in climb.  The baffles and baffle sealing was all bad also.  With everything fixed it has run like a charm, in fact the engine is the best part of the whole plane.  I do have the Intercooler, the temp gauge may not be working right (we are replacing it), but it generally only shows about 40 degrees of cooling from the Intercooler.  That is not nothing, but it is also not the kind of temps the Intercooler people adverstise (70-100 degrees).  We are replacing the temp gauge so the new one may show a better differential.

I do not have a problem with overheating anymore since the repairs were done.  Mine is the LB.  The CHT's are a little warmer when in the teens, than when lower down, that is all.  The engine is getting close to 800 SFRM.  I guess I will know more in about 500 hours, but it does not seem to be showing any signs of premature wear, excess oil use, or running on borrowed time.

It was the GB that had the reputation for burning out fast, and the major problem with the GB was said to be the fixed wastegate, the Merlyn really saves wear on the engine I think.  What you will read about the GB is that pilot engine management was a real issue, and I think that is the key to the GB or the LB, good throttle management and good engine maintenance.  The trick with the LB, Merlyn, and intercooler is to advance the throttle to a point where you will get about 30" MP at the start of takeoff and let the turbo kick in and catch up.  Then slowly advance to 36-37".  You will have plenty of power.  You don't want to firewall the throttle, and if you have the intercooler you don't want to run the MP up to the 40" marked on the factory gauge.  If you do either you will be overboosting the engine.  With the Intercooler the effective MP will be over 40" because the air coming out of the Intercooler is denser than what the gauge is set up for.

I think the Intercooler has one main effect, and that is to allow the engine to run a little cooler at higher altitudes.  There is no lack of cooling lower down, but up higher the air is thinner and a poorer heat conductor, so having help from the Intercooler makes a difference.

The LB is a very fuel efficient engine and likes to fly up high.  There is not speed advantage over the J at lower altitudes, you will typically see 140+ kts., it is up high in the teens where it really shines, and speeds are generally 170+.

It feels like a heavier airplane than the J, and is somewhat easier to land because of that, for me anyway.  The J likes to float more.  The K will float also, but when you pull the power out it wants to sink faster than the J.

[FlyDave]

Here is a great article on the 231:

http://www.mooneypilots.com/mapalog/M20K231%20Eval%20Files/M20K231_Eval.htm

Also, call Laser and ask for Robert and get his perspective on the 231. It's very interesting!

[N9937c]

My intercooler readout also reads about 40 degrees differential but this is c. not f.

larry

[jlunseth]

Yes the temp gauge is in C not F.  The rough rule of thumb adjustment is 1" per 10 degrees C, but the tables they provide are more precise and I believe the adjustment per the tables is less - 1% of MP per 5.5 degrees C differential. 

The bottom line on the intercooler from my limited experience is that it helps the engine run cooler at higher altitudes, and allows a little better climb rate to that altitude.  It is going to increase your critical altitude a little bit.  From memory, the critical altitude per the POH is either 14 or 14,500, and I generally find I can climb right up to 17,500 without having to firewall the throttle to maintain 36-37" max MP (that being the adjusted max MP after subtracting from 40" based on the temp. differential).

I have the LB, Merlyn, and Turboplus.

[N9937c]

am going to install the merlin when i change engines. seems like a good system.

larry

[dlthig]

Does a 231 with intercooler and merlyn wastegate add up to a 252?

[MooneyMike]

Give Tom at Top Gun or Paul at LASAR a call and talk to them about the K model.  I learned alot about the model - and bought a J as it fit my needs better.  If you are heading to Lost Wages, both are an easy Mooney flight away. 

Mike

[FlyDave]

Quote: dlthig

Does a 231 with intercooler and merlyn wastegate add up to a 252?

[RJBrown]

Quote: FlyDave

No, the 231 first used the "GB" engine then the "LB" engine - most 231's have been upgraded to the LB engine but many still need tops and turbo/exhaust replacements before TBO. The 252 was built with the "MB" engine - sigificant enough changes to make the engine run cooler and easier to manage.

[LFOD]

You know, I had a chance to buy a 262 for a pretty good price, I should have taken the deal. Perhaps there are one or two floating out there that you could pick up at 231 prices. That would solve many of these issues.