Lower MP after intercooler installation

[CaptnJ]

Thought this might spark some debate, I found this in the middle of a long thread on Beechtalk about the pros and cons of the TSIO vs TN. George Braly of Tornado Alley Turbo & GAMI fame had this to say about intercoolers. I was wondering how the 231 guys with intercoolers have anything to add, maybe someone with before and after install experience.

Anyway here's what he said...

For a year, I spent a good portion of my time re-engineering an intercooler installation and obtaining FAA approval for the changes. Very careful instrumentation and measurement. I have more recently done more of that with a different engine on the engine test stand (see www.engineteststand.com).

I learned a lot. I am a strong supporter of intercoolers, so some of what I am going to say may sound strange at first.

So, here goes: Frankly most of the conventional wisdom on this subject - - like a lot of the now famous LOP/ROP discussions - - is simply not true.

The practical application results in an outcome that is rather different than everybody anticipates. It is largely a myth that 30" of MP AFTER the intercooler gets you more HP than 30" of MP BEFORE adding the intercooler. In fact, a poorly executed intercooler installation can - - and often does -- result in LESS horsepower at sea level than the same engine without the intercooler.

I don't know who started the whole theory of de-rating an engine after an intercooler, but it sure as the devil was not somebody who was measuring the actual engine torque - accurately - - rather, they were just following the theory as you outlined it and making the calculations, etc. (And, yes, I have heard a story about one after market intercooler outfit that claims to have put a torque meter on before issuing the reduced MP instructions based on that result... but until I see the data, I will have a very hard time with that notion.)

The big problem is that in the euphoria over the large and very beneficial drop in Induction Air Temperatures (IAT) that one gets with an intercooler, the "engineers" forget all about something else: How much of the "good stuff" (ie, good, cold, high density air) you can get into the cylinder on each intake stroke - - also depends on how much of the BAD STUFF (ie, exhaust products) you got out of the cylinder on the previous exhaust stroke.

The ratio of the new "good stuff" to the theoretical maximum "good stuff" is called the cylinder volumetric efficiency Ve. Normally aspirated engine values are up around 85 to 92% of the cylinder's displacement - - although with turbocharged engines, the number will substantially exceed 100%.

When you add an intercooler to a turbocharged engine - - and leave the MP constant - -, you place a restriction in the intake plumbing. That means that the compressor discharge pressure is now two or three (or 4 or 5 or 6 in one case) inches of Hg higher than the wide open throttle MP!!!

In order to generate that extra pressure, the compressor has to work harder. And that means that the turbo has to work harder. And that means that the wastegate is closed a bit more. And THAT means the exhaust back pressure increases and that reduces the cylinder volumetric efficiency.

Result? The improved number of molecules you get into the cylinder due to the denser air is just about perfectly offset by the reduced Ve. Thus, no net increase in useful airflow through the cylinder. And the result of that is no net increase in horsepower at the same MP.

Now... having said THAT - - in my view, it is almost criminal for anybody to operate a turbocharged engine without an intercooler.

There are excellent old SAE research papers that show a HUGE improvement in the detonation tolerance of these engines by use of even a modestly efficient intercooler. These improvements are not trivial. They are substantial.

Installing an intercooler means that you are very very much less likely to inadvertently cause detonation during a moment of inattention during a busy high power climb in an IFR environment - - when you accidentally fail to have the mixture rich enough. Lots of other benefits.

For the same reasons, it lowers peak cylinder pressures substantially and that seriously promotes reduced exhaust valve temperatures and greater valve and cylinder longevity.

Last, and this is something almost nobody appreciates, adding an intercooler results in much better fuel atomization by your fuel injectors during high power operation.

Like I said, the "conventional" wisdom on this subject is seriously flawed.

The benefits of intercoolers are sort of over promoted for the wrong reasons and vastly under promoted for the right reasons all at the same time.

They are generally a good investment.

Regards, George Braly - Tornado Alley Turbo & GAMI

[jlunseth]

This is a known issue and has been a discussion point about intercoolers.  An intercooler is a radiator, it accepts an incoming flow and passes it across multiple metal elements to which the flow (whether air or coolant) passes heat, and thus is cooled.  As with everything in aircraft there is a balance between weight (and reduction in useful load) and accomplishing the desired outcome.  If weight were no issue the intercooler could be a massive plenum that would cool the air maximally with little flow restriction.  Since weight is an issue, the goal is to achieve good cooling with acceptable weight loss, and thus there is some flow restriction caused by the installation of the intercooler in the exhaust line.  I see both CDT and IAT on my instrumentation, and have long since gotten over the "wow factor" of seeing a drop in temperature of over 100 degrees at cruise.  It varies depending on OAT, alt, etc., but the differential temp. is usually somewhere between 75 and 125 degrees, enough that the 280 CDT redline on the factory (nonintercooled) engine becomes irrelevant.  The temperature of the air entering the cylinders is never going to approach that number in the intercooled configuration.  So there is no question that intercoolers help TC engines.

 

Whether and how much to adjust MP from what is stated in the factory POH tables as a result of the lower temperature, has always been a debated issue. Adjustment tables are provided by the manufacturer, and there is no way of knowing whether they were created by putting an engine on a stand and actually testing, or whether they are simple Charle's Law calculations (the volume of a gas decreases as temp. decreases, and therefore pressure decreases although the number of molecules stays the same). 

 

The main issue I have with George Braley's data - and I am sure it is accurate data - is that it was not developed by testing my small bore engine.  The test data is for a 470 cu. in. engine, so I surmise that would be the TSIO-470 that is in the Beeches.  So while the data says there is a valid question, it does not say that for my engine Mr. Braley's data has a valid answer.  There are simply too many variables.   Nature of the induction system and how well "tuned" it is, location and type of the injectors, length and nature of the exhaust system and how well "tuned" it is, what the effect of the operation of the Merlyn wastegate is (the GAMI people concede they are not familiar with the Merlyn). 

 

What seems to be the case, and I have heard this from many people with much experience with Mooney TSIO-360's, is that the answer, viz. the MP needed to produce a certain amount of HP, is less than what is shown in the factory tables for the nonintercooled engines, but more than what the intercooler companies suggest with their adjustment tables. 

 

I am just like Mr. Braley, "show me the data."

[chrisk]

My plane doesn't have an inter cooler, but I have wondered about the MP reductions for full power.   I'm thinking about takeoff at sea level.  The turbo is not providing that much of a boost, and the airflow through the cooler is reduced.  Is 36 inches with an inter cooler really the same as 40 with out one?  And does it change if your taking off at Leadville, since the turbo is working harder?

 

And yes, I would love an inter cooler on my plane, but not for what it cost to add one.

[carusoam]

Welcome aboard Cap'n J.

Temperature, pressure, flow and restriction to flow.....

Even an engineer needs his own data from his own machinery to know exactly what's going on.

The source (Braley and co.) of the data is as good as it gets. How you use (or mis-use) that data is what counts.

In the turbo vs the N/A argument, there is no perfect machine. The compromise is TN with inter coolers....

How you use the technology equates to how long the cylinders last.

How much spare cash you have to spend on fuel and cylinders, and turbo and exhaust parts...leads to how much you want to pay attention to these details.

My favorite three (and a half) A/C to compare...

Long body A: Bravo with inter cooled turbocharger.

Long body B: Ovation with N/A

Long body C: Acclaim with pairs of turbos and inter coolers.

Long body D: Porsche converted automotive engine (non-starter)

************************

The Ovation (310 hp) is off the ground in the shortest distance, climbs well, runs LOP in the O2 levels.

Bravo has a longer ground roll, can't run comfortably LOP, but does well as high as you want to go.

Acclaim is not as spry off the ground, but is known to be the fastest factory built, four seat, piston powered airplane.

*******

To get high altitude performance with machine reliability for the normal human being... Use a turbo with a controller and inter cooler.

The additional performance comes at the cost of complexity and ground roll and FF.

And if you get it wrong, a hand full of dollars may be required.

Take your pick,

-a-

[RJBrown]

My plane doesn't have an inter cooler, but I have wondered about the MP reductions for full power.   I'm thinking about takeoff at sea level.  The turbo is not providing that much of a boost, and the airflow through the cooler is reduced.  Is 36 inches with an inter cooler really the same as 40 with out one?  And does it change if your taking off at Leadville, since the turbo is working harder?

 

And yes, I would love an inter cooler on my plane, but not for what it cost to add one.

The cost of not having an intercooler may be more than cost of buying one.

Limited performance and/or shorter engine life are two costs that are hard to quantify.

But heck your a flatlander you don't really need a turbo any way. Just fly it like a 201 and you'll be just fine.

[jlunseth]

My plane doesn't have an inter cooler, but I have wondered about the MP reductions for full power.   I'm thinking about takeoff at sea level.  The turbo is not providing that much of a boost, and the airflow through the cooler is reduced.  Is 36 inches with an inter cooler really the same as 40 with out one?  And does it change if your taking off at Leadville, since the turbo is working harder?

 

And yes, I would love an inter cooler on my plane, but not for what it cost to add one.

 

You are right in theory, in practice most of us just use 36 or 37" and once we get that set, we just leave it there.  There is some turbo lag, so you don't just put the throttle at a point and that's it.  You put in something that will get you in the high 20's, then slowly add power to 36".  With the lag involved, you don't want to be trying to move the throttle around any more than you need to on takeoff.  The airplane is picking up speed from zero to around 120, so flow is going to be improving and it is not useful to try to anticipate at what point on the runway the diff. temp. should be what and the MP should therefore be what.  I use 36" and have had no issues with takeoff distance anywhere, and that includes at Leadville.  I went to Leadville a couple of years ago as part of a Mooney PPP.  Completely uneventful in a turbo.  The only "event" was that I made the mistake of thinking I should use a different starting strategy because of the altitude, and whatever it was (I don't remember) it didn't work, so I just used my normal start, she started right up and purred like a kitten.  36" MP was plenty for takeoff. 

 

Generally speaking, TAS will be higher so you will cover more ground both landing and taking off, but also generally speaking those mountain runways are longer than what we are used to in the flatlands, so you just wait until the aircraft wants to fly, or quit flying in the case of a landing, and don't rush it.  Power wise, the takeoff with a turbo is identical to what you would do at sea level. 

[fluffysheap]

I don't know who started the whole theory of de-rating an engine after an intercooler, but it sure as the devil was not somebody who was measuring the actual engine torque - accurately - - rather, they were just following the theory as you outlined it and making the calculations, etc. (And, yes, I have heard a story about one after market intercooler outfit that claims to have put a torque meter on before issuing the reduced MP instructions based on that result... but until I see the data, I will have a very hard time with that notion.)

...

When you add an intercooler to a turbocharged engine - - and leave the MP constant - -, you place a restriction in the intake plumbing. That means that the compressor discharge pressure is now two or three (or 4 or 5 or 6 in one case) inches of Hg higher than the wide open throttle MP!!!

In order to generate that extra pressure, the compressor has to work harder. And that means that the turbo has to work harder. And that means that the wastegate is closed a bit more. And THAT means the exhaust back pressure increases and that reduces the cylinder volumetric efficiency.

Result? The improved number of molecules you get into the cylinder due to the denser air is just about perfectly offset by the reduced Ve. Thus, no net increase in useful airflow through the cylinder. And the result of that is no net increase in horsepower at the same MP.

 

It's an interesting case to make.

 

The important thing is to compare the increase in the density of the intake charge going into the manifold, to the pressure drop over the intercooler.  The cooler the air, the more power.  The greater the pressure drop, the less power.

 

Suppose the air temperature around the intercooler is the same as the temperature of the air coming out of the turbo.  Obviously, in this case, the intercooler is doing no good, but you still get the pressure drop.  So the intercooler is hurting in this case.  It isn't as odd as it might seem - Mazda RX-7s and Nissan Z's of the 1980s had their intercoolers mounted on top of the engine (the turbo models had a slot in the hood where the intercooler took in air), and if the car wasn't moving, the intercooler was surrounded by hot air from the engine and was actually more of an "inter-heater."  But once the car got going above about 20 or 30 mph, the outside air would blow through the slot and properly cool the intake air.  A turbo-normalized engine at sea level is another example.  At sea level, the turbo's not doing anything - the air is already at the right pressure.  But the intercooler still creates a restriction in the intake.

 

Now, for an opposite thought experiment, suppose you managed to build an intercooler that had no pressure drop at all.  (It isn't possible, but let's pretend).  In this case, you'd still get the cooling effect, but no additional restriction.  That would mean the air density on the cold side is higher than the density on the hot side.  Since we've already stipulated that the pressure is the same, that means that air needs to flow more quickly on the hot side to keep the overall mass air flow the same*.  That is to say, this hypothetical super-efficient intercooler actually sucks the air out of the turbo!

 

Real intercoolers are somewhere in between.  They have a pressure drop, and they also have a temperature drop.  So the question at that point becomes whether the loss of intake efficiency due to pressure drop is greater or smaller than the gain due to the cooler, and thus denser, air.  An intercooler that cools the air more than it restricts it would increase power, and one that restricts more than it cools would decrease it.  It's not going to be possible to assign one magic efficiency value to an intercooler because it will vary based on conditions.  It would be a pretty lousy intercooler that was a net negative for most situations, but I suppose it's possible.

 

The improved number of molecules you get into the cylinder due to the denser air is just about perfectly offset by the reduced Ve. Thus, no net increase in useful airflow through the cylinder. And the result of that is no net increase in horsepower at the same MP.

Sure - for a turbo-NORMALIZED engine, at sea level.  30"MP after intercooler is probably slightly less power than 30" without it, because at that pressure, the turbo isn't heating the air, so there's nothing to cool!  If you've got an intercooler like the really bad one in his example, that drops 6" of pressure, then suddenly instead of what amounts to a naturally aspirated engine, you've got a turbo that's needing to make 36".  And that's going to take some power.

 

But I would doubt his claim that backpressure is responsible, or at least mostly responsible.  I would say that the increased temperature of the intake air is probably more of a factor.  Even after the intercooler, you're probably going to have air that's at least 30 degrees hotter than what it would otherwise be, and we all know what 30 degrees will do to your density altitude.

 

But if the engine is boosted even at sea level, rules change.  Intercooled is basically always better than non-intercooled then.  And even that normalized engine, once you go above sea level, is really a boosted engine, where the MP redline just happens to be 30".  The intercooler's better there too, although one that drops 6" of pressure probably isn't helping much.

 

* I'm not sure the best way to explain this, but if anyone doesn't believe it I'll try.

[jlunseth]

Well, just to be clear here, 30" of MP is 30" of MP.  MP is measured in the induction system, after the intercooler, so while there is a pressure drop across the intercooler, the engine does not experience lower pressure at a setting of 30" MP because the intercooler is there, it experiences the same 30" whether there is an intercooler or not.  That is so because the pilot sets that pressure at 30". 

 

That 30" is cooler air than if an intercooler were not present, and therefore contains more molecules, but it is still 30".  What Mr. Braley is talking about is the work that the engine must do to produce the cooler 30" of MP.  Nothing is free in an engine, and cooling the air has a price.

 

If he had data for the TSIO360-GB/LB installed in our 231's, and for the Merlyn semiautomatic controller, that would be interesting.  What he has, is data for a completely different engine setup and there is only so much extrapolating one can legitimately do.  You can say "this is an issue," you can't quantify what its actual effect is.

[CaptnJ]

What I think is interesting is the difference between a conventional wastgate set up and a Merlin, because the Merlin is trying to balance the upper and lower deck pressures. It almost solves the pressure drop across the intercooler automatically. What it can't account for is the volumetric efficiency issue that Mr. Braly notes, the increase in exhaust back pressure because of waste gate positioning. I might be overthinking this, my main intrest is the increase in engine efficiency and possibility of being able to run the engine at higher power.

Because TIT seems to be the limiting factor LOP on the TSIO engines, probably due to the lower compression ratio pistons (less cooling of the exhaust gases during the expansion phase compared to the TN engines), if you could run a high enough MP, and lean enough mixture ~100 LOP, would you be able to see higher power settings like the TN guys? Approaching 85% LOP. The best I have seen for FF is about 10.3 gph LOP 67%. CHT has never been a problem, all under 365, TIT is the show stopper, although I stay around 1600deg. This seems to be what I have read elsewhere about this engine. I don't have an intercooler on my aircraft and while I would like to install one they seem expensive and hard to come by.

Now obviously running high MP results in high CDT temps exasperating the problem, so the intercooler is nessesary to run the engine this way, I don't currently try to operate this way. But the higher MP also means more cooling air in the combustion chamber, and a leaner mixture, theoretically. I am mostly trying to determine if this is even a realistic idea on the TSIO-360. I have read about a guy running WOT with a TSIO 520 no intercooler, I think that's 36" MP, he states he's done this for ~700 hrs. taken with a grain of salt, this is the internet after all, haha

Does anyone with an intercooler see substantial reduction in EGT/TIT temps with an intercooler ie. does the 100 deg IAT drop result in a 100 deg TIT drop?

I do think it is odd the Mr. Braly writes about detonation and valve life as the best thing about intercoolers, he also has shown in the past how monumentally difficult it is to create detonation in aircraft engines when CHT is under control. His company TAT seems to use intercoolers as a performance enhancement allowing higher power settings. He also commonly states valve issues are a build problem not a pilot problem, if CHT are under control. I'm not really arguing the point as I'm definitely not qualified to debate with him about engines, just seems odd coming from him.

I would also love to know if the Acclaim guys can operate the TAT way, I think those are TN engines, right?

Thanks for the responces

P.S. I know it looks like I'm some sort of Beech lover, all this TAT stuff, and they are nice, but I love my Mooney, and it would be great to be able to smoke a 300 HP plane with 210. They just seem to have a much larger body of knowledge, maybe more turbo aircraft out in the wild, or maybe more just more "experts". "You can always tell a Beech pilot, you just can't tell them much" JK

[jlunseth]

The Merlyn does not solve the pressure drop across the intercooler, the pilot does.  The pilot sets the MP, the Merlyn only sees to it that, once set by the pilot and if all other things remain equal, the MP will stay where the pilot set it.  So if a pilot sets 30" MP in an engine without an intercooler, and then adds an intercooler and takes the plane up again, and again sets the MP at 30", there may be a drop in pressure across the intercooler the second time, but the MP will be the same both times because the pilot set it the same.  The Merlyn does not set the MP.

 

I would not attempt to operate a turbocharged aircraft at 85%HP and LOP.  The problem is that the red box becomes so big that if you are keeping detonation under control, you probably can't get 85% to begin with, and if you are getting 85% you probably are not keeping detonation under control.  You can only lean the mixture so far before the fire starts to go out.  The GAMI/APS people would likely tell you the same thing.   I don't know anyone who advocates operating a turbo LOP at 85%.

 

The GAMI/APS people also teach that controlling CHT does not necessarily mean that detonation is under control.  That comes from Mike Busch.  There are scenarios, such as where an engine is set up with superior cooling, or where the aircraft is flown in very cold temps (such as we have here in MN right now), where detonation can occur and yet CHT's will appear to be under control.  I think that as a rule of thumb, Mike Busch's CHT control theory is fine in a Mooney, because I don't know any that have truly superior cooling, and is also fine if you are flying in temps above, say, 15 dF. 

[KSMooniac]

I would also love to know if the Acclaim guys can operate the TAT way, I think those are TN engines, right?

 

I haven't flown an Acclaim, but technically they are NOT turbo-normalized...some stupid marketing decision by Mooney called them that.  They are actually boosted engines with low compression pistons, but have the HP originally capped at 270 hp and that is why they were called TN in my opinion.  Stupid stupid stupid.  They should've bought a firewall-forward package from TAT and made a phenomenal Mooney instead of doing what they did.  They probably would've gotten it to market quicker and at less cost, and run away from all of the other piston singles in the market.

[CaptnJ]

The Merlyn does not solve the pressure drop across the intercooler, the pilot does. The pilot sets the MP, the Merlyn only sees to it that, once set by the pilot and if all other things remain equal, the MP will stay where the pilot set it. So if a pilot sets 30" MP in an engine without an intercooler, and then adds an intercooler and takes the plane up again, and again sets the MP at 30", there may be a drop in pressure across the intercooler the second time, but the MP will be the same both times because the pilot set it the same. The Merlyn does not set the MP.

Your absolutely right, the Merlin is only magic in name, the pilot sets the MP, what I meant was it references the upper deck pressure and the manifold, to keep them the same, one reference before the intercooler and one after the throttle plate, I think.

But because we have no way to know what that upper deck pressure is ( no UDP gage) I guess I can't very well set the waste gate to that pressure.

"The Merlyn upper deck pressure control (aka automatic wastegate) is an automatic pneumatic device that operates based on the difference between the upper deck pressure and the manifold pressure. Functionally, it works by balancing the pressures."

I would not attempt to operate a turbocharged aircraft at 85%HP and LOP. The problem is that the red box becomes so big that if you are keeping detonation under control, you probably can't get 85% to begin with, and if you are getting 85% you probably are not keeping detonation under control. You can only lean the mixture so far before the fire starts to go out. The GAMI/APS people would likely tell you the same thing. I don't know anyone who advocates operating a turbo LOP at 85%.

Here is the power setting for some different TAT installations, this stuff is what got my mind going in the first place, pretty impressive

They vary from 81.9 % to 89.4% in their highest power configuration. 300 HP (FF x 14.9)

"THEREFORE, we suggest that, in general, in cruise, that the engine be operated with the throttle in the WOT position, and the horsepower be controlled by appropriate use of the mixture and propeller governor controls as follows:

Initially, set the propeller governor to produce 2500 RPM.

Set the mixture to a fuel flow that produces a TIT of from 50 to 100°F lean of peak TIT.

"Whirlwind System II"

Typically, on a (TN) IO-550 at WOT, this will be from 15.5 to 17.0 GPH.

Typically, on a (TN) IO-520 at WOT, this will be from 14.5 to 16.0 GPH.

"Whilwind System II with Rammer II"

Typically, on a (TN) IO-550 at WOT, this will be from 16.0 to 17.5 GPH.

Typically, on a (TN) IO-520 at WOT, this will be from 15.0 to 16.5 GPH.

"Whilwind System III with Rammer II and scoop"

Typically, on a (TN) IO-550 at WOT, this will be from 16.5 to 18.0 GPH.

Typically, on a (TN) IO-520 at WOT, this will be from 15.5 to 17.0 GPH.

NOTE: Do not think that you are "helping" the engine by using less than WOT and then select the fuel flows from the list above. This will simply result in the engine operating at much richer mixture with much higher CHT's."

The GAMI/APS people also teach that controlling CHT does not necessarily mean that detonation is under control. That comes from Mike Busch. There are scenarios, such as where an engine is set up with superior cooling, or where the aircraft is flown in very cold temps (such as we have here in MN right now), where detonation can occur and yet CHT's will appear to be under control. I think that as a rule of thumb, Mike Busch's CHT control theory is fine in a Mooney, because I don't know any that have truly superior cooling, and is also fine if you are flying in temps above, say, 15 dF.

Yes I agree that's why I was wondering if anyone is able to get to 100 deg LOP w/ a TSIO 360.

This whole thread for me is to see what is theoretically possible with the TSIO 360. Pretty much everyone one this board has much more experience operating their AC than I do, I've only had it flying for a few months. There are also lots of different configurations of this aircraft too, GB LB, intercooler, Merlin. So lots of variables to play with, obviously I would love to have a LB, intercooled, Merlin, or better yet an SB if that were possible.

I just always think about trying to get the most performance from what I have available to me, having a turbo is fun but is it faster?!

The standard answer is yes but... only if you go higher. Can we optimize our operation of the engine to get both, faster high and low?

[CaptnJ]

*edit

[carusoam]

They confused the customers as well....

I thought...

A Continental IO550(g) was the same engine, cylinders, and pistons as the TNIO550(g) with different exhaust details.

280hp @ 2500 rpm... @S.L. Or whatever level the TN system can maintain as SL...

These details came out while I was studying for the engine rebuild vs A/C change of mission test.

When they changed the cylinder design, the IO550(g) became the IO550(n). There was an increase in rpm to 2700 as well. Output went to 310 HP.

An IO550(g) can be bumped up to 2700 rpm (STC required, technically), but it is still a (g).

Are you sure? ( question directed to Scott from KS ). I'm challenged by marketing now.....

To run reliably/ smoothly LOP it is best to have a constant A/F ratio which requires

Balanced fuel injectors

Balanced air flows

Continental makes good FI's, my stock ones would run 100dF LOP at lower altitudes.

Continental also makes good intake pipes, equal length, equal/gentle curvature.

The Bravo has a very nice engine, but without the balanced curvy intakes, it is challenged to run LOP. Most people that buy this plane want to go fast first, then improve efficiency as a second thought. Then give up on LOP...

The POH of the IO550 clearly defines LOP. I would expect that the TN-IO550 SHOULD be able to as well.

One question for the OP: do you have the curvy balanced intake like or similar to the IO550?

Why there is no simple answer...

To get all this correct, would require the understanding of non-steady state flow of compressible gases under varying temperatures, and pressures.

If you need a new intake, you will quickly realize that there is no free lunch. Then you will also realize that the ideal intake doesn't fit under the existing cowl.

I think Erik (Rocket Proff) had a similar discussion a while back...

Best regards,

-a-

[carusoam]

For the eyes...

Inter cooler picture...

http://en.wikipedia.org/wiki/Continental_IO-550

N/A...

http://www.tcmlink.com/EngSpecSheetDocs/IO550N.pdf

Best regards,

-a-

[CaptnJ]

Unfortunately both the GB and LB are the log and runner style, not the tuned style of the newer engine. I have read good things about GAMIs fixing the FA ratio even with the log style, mine are on the way

[jlunseth]

Well, on the WOT operation thing.  Just remember that there is a big difference between a TN or normally aspirated engine on the one hand, and a TC engine such as the TSIO-360-GB/LB that has a semi-automatic wastegate controller on the other hand.  The TN and NA engines can never be operated at more than 100%HP.  Well, I guess in theory a NA could operate at an airport below sea level with a high ambient pressure and provide a little more than rated horsepower, but that would be an exception and a small excursion compared to a TC.  The TN is regulated so the turbo never produces more than sea level pressure.  A TSIO-360 is never operated at WOT except above critical altitude (15k for the non-Merlyn, much higher for the Merlyn). If you were to operate the engine at WOT at sea level you would probably produce somewhere in the neighborhood of 120% of rated HP before the relief valve opens to try to stop you from blowing the engine.

 

Thus, what is the equivalent of WOT in the TSIO?  I guess that would be the 36 or 37" the pilot uses to establish 100%HP on takeoff.  The problem with the idea of just leaving the throttle there and using mixture alone to reduce power, is two fold.  First, MP will fall as fuel flow is brought back, and it will fall quite substantially as the engine gets over on the lean side.  It is not like an automatic controller where if you set MP at 32", the controller keeps it at 32".  If you want to keep it at 32" or whatever number you pick, as you bring the mixture back, you the pilot must add MP.  The Merlyn will not do it for you.  Second, you now have no idea where you are operating the engine with respect to peak EGT's.  None.  By making simultaneous mixture and MP changes, whatever peak was you have changed it.  So how do you assure that the engine is LOP enough to avoid detonation? 

 

All that said, there was a fellow on Mooneyspace a couple of years ago who said he was operating his TSIO-360 that way, setting 100%HP on takeoff and then just bringing the mixture back with the BMP.  Have not heard further about that technique, and don't know how his engine is faring.

[aviatoreb]

Wow - welcome to mooneyspace George!