A 231 question

[timpercarpio]

We're transitioning from a 201 to a 231 and should pick it up late next week. In reading a report on MAPA it states that with an intercooler you should use 252 power settings. Our airplane has a Merlyn wastegate and an intercooler. Here's the quote.....

So what do you do for power settings if you have a 231 with an aftermarket intercooler installed. I can tell you one thing you better not do - use the original power setting charts for your engine for setting power. With an intercooler, a reduction in manifold pressure is required to keep from over-horsepowering the engine. This reduction is necessary for both takeoff, climb and cruise and technically should vary as a function of the amount of cooling being generated by the intercooler.

Again, if you don't make this adjustment downward in manifold pressure settings with an intercooler, you'll be pulling more horsepower than allowed from the TSIO-360 engine by Continental. Aircraft performance will be up if you fly original manifold pressure settings, but so will fuel flow. One thing will be down -engine life expectancy. You can't pull extra horsepower from the TSIO-360 without repercussions to engine reliability and reductions in engine TBO.

Here's what I tell MAPA members who have an intercooler installed on their 231 - find a M20K 252 power chart and use it for your engine. Takeoff and climb your intercooled 231 at 36" manifold pressure, 2700 RPM and 1400 degrees TIT. Cruise that same airplane at the power setting we designed the 252 to be cruised at, which is 28" manifold pressure, 2500 RPM, Peak TIT plus 50 degrees rich. Use these settings and your intercooled 231 will be a happy camper and a good performer.

What do you 231 drivers think?

Thanks,

Tim

[Geoff]

This is very good advice. If the inter cooler installation was done properly the MAP gauge should have been remarked with the proper red line which is a good start. The POH should include the new power chart.

Pilot control of power and temperature are very important in the 231.

[Geoff]

It is the place to start until you begin to experiment with the LOP operations.

[timpercarpio]

Thanks, how do you run LOP?

[Parker_Woodruff]

Hi Tim,

 

I'm glad to see that you're upgrading in airplanes...I wasn't sure what your plans were when I saw your plane for sale on Controller.

 

Lean of Peak operations are an incredible bonus when flying the 231.  However, some engines on the M20K will take some work to get that done.  Make sure your induction is tight first before going further.  Then you'll want to make sure that the spark is good (I recommend using Tempest Fine Wire spark plugs).

 

Finally, you'll want to do a GAMI lean test.  The process is described here:

 

http://www.gami.com/gamijectors/leantest.php

 

Once the fuel injectors are all distributing fuel flow evenly, LOP operations shouldn't be a problem.  A lot of people will tell you that LOP is nearly impossible with the TSIO-360.  This simply isn't true, but the engine does need to be in good shape between fuel, air, and spark.

Where are you picking the airplane up from?

[timpercarpio]

Parker,

Thanks, that is all good information that we will definitely follow. We're getting the airplane from Florida, N5767T. I'll post some pictures when we get it and get comfortable with it.

We miss your presence at Falcon Insurance. Hope you're doing some flying.

[rainman]

Tim,

I've been flying my intercooler equipped 231 for over three years as described to you. 36" max 2700 rpm on climb, 28" 2500 rpm in cruise. I do find that in the summer I need to trail a bit of cowl flap above 17K to keep the CHTs below 390. Enjoy. Ray

[timpercarpio]

Thanks, Ray.

[carusoam]

Do you fine gents use the <65% hp setting safety net for safe LOP ops in the 231?

This is a nice easy way to get started with LOP in the N/A world...

Just wondering,

-a-

[Parker_Woodruff]

Do you fine gents use the <65% hp setting safety net for safe LOP ops in the 231?

This is a nice easy way to get started with LOP in the N/A world...

Just wondering,

-a-

For the GAMI tests, absolutely.

That or the big pull to get quickly thru the "red box" and to a fuel flow that will be in that 65%

With GAMIs? I would typically run about 11.2 GPH. Post-Encore conversion that's just under 70% power. Pre-conversion, that's about 73%.

Ran as high as 12 GPH LOP with cool temps. That's 75% or 78% depending on which TSIO-360

[jlunseth]

Weeelll, Parker had a 252, and there are some significant differences between the 252 and the 231 in terms of running LOP.  There are differences in the induction system and the MB was an improvement over the GB or LB which is in the 231.  The MB engine also has an automatic wastegate controller, so if you set MP at let's say 28 inches, and you pull the engine over to the lean side, you still get 28".  The GB and LB had a fixed wastegate as they came from the factor, meaning the wastegate was pre-set on the ground to spill a certain amount of the air output from the turbo.  Many are modified with the Merlyn aftermarket wastegate, which is a differential controller.  But regardless of whether the engine is in the factory configuration or has the Merlyn, it is not an automate wastegate the same as what is on the MB.

 

The bottom line is that if you simply pull the 231 engine over from the rich side to the lean side, manifold pressure will fall because the output of the turbo reduces, and it falls fairly dramatically.  You can open the throttle to restore the MP to whatever level you had it at, but frankly at that point you have pretty much no idea whether you are at peak, or LOP, or ROP, or some cylinders are one and some are the other.  From what I see on my monitor when I try this (I have a JPI 930 and GAMI's), you are either at peak, or perhaps 10 or 12 degrees LOP, and some cylinders are probably still at peak or ROP.  If you are trying to operate at 75% power or thereabouts, that is not a good situation.  If you are at or below 65% you are ok, but who wants to operate a turbo at or below 65% ?

 

There is a fallacy in the concept of the GAMI injectors.  That concept is that if you tune the injectors so that the mixture is the same to each cylinder, then when you pull the engine over 20 degrees or so LOP from the last cylinder to peak, you are assured that all cylinders are LOP and operating in a safe range.  The problem is that the injectors can be tuned to provide an even mixture only at a specific power setting, and they will more or less maintain even mixtures at other power settings only if the airflow is relatively the same at the other cylinders. In an untuned induction system, the relative air pressures among the cylinders will change depending on the power setting.

 

The 252 would frankly be a much better choice than the 231 (which is what I have) if your ambition is to run LOP at standard cruise power settings (i.e. in the 75% range).  The problem with the Bravo, as I understand it, is pretty similar.  Probably better to stay ROP, but some people have had some luck with LOP ops in the Bravo.

[231LV]

Oh yea! I've been flying my 231 for 10 years...LOP all the time...mine has an intercooler...the advice you picked up is correct...limit yourself to 36 inches of MP and you will be fine...2500 rpm and you should  be able to run on 10 gph...up high...175 KTAS...sweet airplane!! if you could afford it, the 252 is a better plane but about $50 to $80k more....the 231 is a great traveling plane 

[apriav]

Could I talk anyone into lending me a copy of the 252 power charts (for an extended time period). I have been doing the math as I fly. Would like to take the guess work out.