Mooney 231 Slow Climbout

[natdm]

22 minutes ago, A64Pilot said:

I’m not aware of any accidents on go around attributed to not having flaps down on a small single engine airplane, of course large Commercial Jets must have flaps and slats down and some have died from not doing so, or retracting them early, but that’s not us. We climb better as in faster with zero flaps

I’m more talking about students doing touch and go’s and forgetting to put flaps up, then dumping them and losing lift. Not go-arounds.

 

I’ll wait for the plane to lift on its own and retract flaps after gear next time. 

[A64Pilot]

18 minutes ago, natdm said:

I’m more talking about students doing touch and go’s and forgetting to put flaps up, then dumping them and losing lift. Not go-arounds.

 

I’ll wait for the plane to lift on its own and retract flaps after gear next time. 

By lift on its own I mean hold a little nose up, if the trim is down she will never fly off by herself.

It’s hard to talk about on the internet where I could show you what I mean easily.

Problem with telling you where to place trim is your CG could be different of trim indicator be rigged slightly different.

Have you noticed an approx airspeed where you break ground?

 

 

[Shadrach]

On 9/22/2022 at 5:06 PM, A64Pilot said:

If he was LOP with a fuel flow of 8 GPH he should using the 200 HP lycomings number of 14 hp per gph be making 112 HP, much less than 75%.

Now a turbo should be more efficient than a non turbo so it ought to do better than 14 HP per gl, but I have no idea. I’m not even sure of the 14 HP for NA.

Point is though that unless the charts specify LOP, the % power if run LOP will be lower than a ROP chart will indicate

 

 

On 9/24/2022 at 5:14 PM, A64Pilot said:

That would be about what I would expect, just a little better than the non turbo Lycoming.

So 13.7 is 110 roughly, or 52% power roughly, which would make his cruise speed about right?

I don’t think anything is wrong with this airplane, it’s climbing at over 1000 FPM 400 feet after takeoff, sound prett good to me, 

 

It’s the opposite. Fuel efficiency tracks compression ratio.  The 8.7:1 Lyc will make about 15 hp per gph. The 7.5:1 TSIO360 about 13.7. The Lycoming is more thermally efficient.

[natdm]

47 minutes ago, A64Pilot said:

By lift on its own I mean hold a little nose up, if the trim is down she will never fly off by herself.

It’s hard to talk about on the internet where I could show you what I mean easily.

Problem with telling you where to place trim is your CG could be different of trim indicator be rigged slightly different.

Have you noticed an approx airspeed where you break ground?

 

 

I typically add some back pressure to the yoke at rotate but it doesn’t take off quite at that time. I’ll check tomorrow (doing a few airports) and report back. Might record it too. 

[A64Pilot]

54 minutes ago, Shadrach said:

 

 

It’s the opposite. Fuel efficiency tracks compression ratio.  The 8.7:1 Lyc will make about 15 hp per gph. The 7.5:1 TSIO360 about 13.7. The Lycoming is more thermally efficient.

I know compression ratio, but the turbo is shoving in a much more dense charge due to it being under pressure so that it’s effective compression is higher, that’s one reason they need higher Octane fuel on average, the higher the boost the higher the Octane required of course. Of course they are often lower compression so that they can run more boost.

Fuel efficiency to a point does track compression ratio in an NA motor, but I’m pretty sure a forced induction motor breaks some rules

Then a turbo is a more efficient motor, due largely to it taking what’s normally waste energy (heat) and putting it back into the motor so to speak when it’s on boost.

99% sure the reason all OTR trucks are turbocharged is for greater fuel efficiency, same for even ship motors, I believe every motor that the most important consideration is fuel efficiency is turbocharged, even the ones where weight and size aren’t important.

Could be wrong though

I thought the “number” to use to calculate HP when LOP for our IO-360 angle valve Lycomings was 14? I have no reference, just actually what I’ve heard here.

[Shadrach]

11 hours ago, A64Pilot said:

I know compression ratio, but the turbo is shoving in a much more dense charge due to it being under pressure so that it’s effective compression is higher, that’s one reason they need higher Octane fuel on average, the higher the boost the higher the Octane required of course. Of course they are often lower compression so that they can run more boost.

Fuel efficiency to a point does track compression ratio in an NA motor, but I’m pretty sure a forced induction motor breaks some rules

Then a turbo is a more efficient motor, due largely to it taking what’s normally waste energy (heat) and putting it back into the motor so to speak when it’s on boost.

99% sure the reason all OTR trucks are turbocharged is for greater fuel efficiency, same for even ship motors, I believe every motor that the most important consideration is fuel efficiency is turbocharged, even the ones where weight and size aren’t important.

Could be wrong though

I thought the “number” to use to calculate HP when LOP for our IO-360 angle valve Lycomings was 14? I have no reference, just actually what I’ve heard here.

there is a spreadsheet for calculating LOP Horsepower in the downloads section of this forum.

8.7:1 = 15.14 

8.5:1 = 14.89

7.5:1 = 13.73

7.3:1 = 13.53

Compression ratio drives thermal efficiency. Those OTR trucks are turbodiesels that are running compression ratios in excess of 16:1 or higher.

I think that if you look at any of the boosted, turbocharged aero engine POH’s and compare fuel flow directly to horsepower, you’ll find that they’re  less efficient than they’re higher compression, normally aspirated brethren. 

[Will.iam]

4 hours ago, Shadrach said:

there is a spreadsheet for calculating LOP Horsepower in the downloads section of this forum.

8.7:1 = 15.14 

8.5:1 = 14.89

7.5:1 = 13.73

7.3:1 = 14.53

Compression ratio drives thermal efficiency. Those OTR trucks are turbodiesels that are running compression ratios in excess of 16:1.

I think that if you look at any of the boosted, turbocharged aero engine POH’s and compare fuel flow directly to horsepower, you’ll find that they’re  less efficient than they’re higher compression, normally aspirated brethren. 

Something isn’t right 8.5 and 7.3 are both 14 numbers and 7.5 is a 13 number? Would not the 7.5 be higher than the 7.3 but lower than the 8.5?

[Shadrach]

2 hours ago, Will.iam said:

Something isn’t right 8.5 and 7.3 are both 14 numbers and 7.5 is a 13 number? Would not the 7.5 be higher than the 7.3 but lower than the 8.5?

I fat fingered it on my iPhone. Edited! Thanks!

[M20F]

12 hours ago, Shadrach said:

???? M20K Vy of 96kIAS is in the white arc.

You are correct!

[Schllc]

I don’t have ownership experience with the k models, but I have owned ovations and acclaims. So the comparison of the same engine with and without turbo is relevant  

The ovation up to about 400’ agl, out performs the acclaim.
After that, the turbo really kicks in and it slowly starts to out climb/perform the ovation, and by 5000’ leaves the ovation in its dust. 
I would imagine the Turbo version of the same engine in the K does the same thing. 
Some of the acclaims I’ve flown also require a temporary reduction in the ROC shortly after takeoff to reduce cht. 
From everything the OP had described, it sounds like the performance is normal to me. 

[Shadrach]

7 minutes ago, Schllc said:

I don’t have ownership experience with the k models, but I have owned ovations and acclaims. So the comparison of the same engine with and without turbo is relevant  

The ovation up to about 400’ agl, out performs the acclaim.
After that, the turbo really kicks in and it slowly starts to out climb/perform the ovation, and by 5000’ leaves the ovation in its dust. 
I would imagine the Turbo version of the same engine in the K does the same thing. 
Some of the acclaims I’ve flown also require a temporary reduction in the ROC shortly after takeoff to reduce cht. 
From everything the OP had described, it sounds like the performance is normal to me. 

No experience with either of those planes but my experience climbing against a Bravo in my F suggests that your 400agl number is missing a zero.

[Shadrach]

On 9/24/2022 at 3:21 PM, jlunseth said:

My thoughts. From a power standpoint rather than a temperature standpoint the fuel flow is not a concern in your scenario. Since you are rich of peak already, adding more fuel flow is not going to significantly increase power output, because ROP you already are using more fuel than can be burned in the combustion cycle. The POH required fuel flow is 22.5-24.0 and you are in that range. What extra fuel flow will do for you in AZ while ROP is keep your CHT's down and that's it. Increasing MP is what will increase power while ROP. In the 231 there is an interlink between MP and fuel flow, so if you increase MP the fuel flow will increase, the engine tries to maintain a steady air/fuel ratio.

If you look at the STC for the turboplus, there is a chart for determining what MP the mechanic should use for a given OAT when setting the max fuel flow. Generally speaking, it is around 37" and varies by some tenths of an inch with OAT. The 36" max that people tend to use for the intercooled 231 (including me) appears to come from an article in an old Mooney magazine that basically said, if you have the intercooler, use the power settings for the 252. The max power setting for the 252 is 36". In reality, based on the STC, it is 37" for the intercooled 231. There should be no harm in increasing takeoff MP to 37, and that will increase your power somewhat and will allow the fuel flow to go up somewhat. That said, I will generally pull the power back to around 36" once I am off the ground and in the climb.

Another thing to consider is that the better the intercooler is operating the denser will be the intake air, and the more power the engine will make. So in theory, the intercooler is not having much of an effect when you put in takeoff power at the takeoff end of the runway and let go of the brakes. There just is not much air flow over the intercooler and not much cooling effect. It quickly picks up efficiency as you roll down the runway. There will also be a ram air effect, so if you put in 36" at the takeoff end of the runway you are going to see the MP increase from that effect further down the runway. I am not suggesting that you try to vary your MP from, say, 37 or 38 at the takeoff end to, say, 36 at liftoff. There is just too much going on, so best to just set it around 36-37, reduce it a little if it starts going over 37, and otherwise leave it alone. The engine has plenty of power and my plane does not seem to care if takeoff is at 35 or at 37 on the vast majority of runways.

I don't think fuel flow is your issue at all. If you were concerned about high CHT's fuel flow would be the place to look, but you are well ROP and fuel flow is not going to significantly change power. I am wondering what airport you are having this problem at. KIWA, your home base, is not that high, although it certainly can be hot. But it does not have a 3,000 foot runway either. I am wondering if these longer takeoffs are perhaps at a higher altitude airport than KIWA. Your turbocharger will allow you to make full power even up at Leadville (which is just shy of 10,000), but that does not change the fact that the density altitude is quite high there and it will require a higher airspeed for the wing to generate the same lift that it does at sea level.  Most of the high altitude airports out west are significantly longer than what we would see here in the midwest for exactly that reason.

Also, I am wondering when you raise your gear. It should come up when you have a positive rate of climb, and the flaps shortly after. You will have a little nose down movement when the flaps retract so guard against that. Once gear and flaps are up the aircraft will accelerate quickly, in fact it already has been for awhile.

Here is what I do, any airport any season, if it helps. My takeoff is full rich. I start the roll with the MP roughly 50 % in (I do it by feel and don't really look), and after a short while I adjust it to somewhere between 36 and 37. If it goes slightly over 37 I don't worry about it too much. If it gets near 38 I will pull off just a little power. Rotation is 61 KIAS but I am never in a hurry, I let the plane tell me when it is ready to fly. I raise the gear when I have a positive rate on the ASI, and then the flaps. I pitch for 85 KIAS to 1000 feet above the runway. That is neither Vx nor Vy. There is some good research that Vx is too nose high and you will be in jeopardy if you have an engine failure so save Vx for when it is really needed. Vy takes too much distance so by the time you reach the altitude where you could turn back in the event of engine failure (around 1,000) you are too far away to make the airport to make it back. A speed around best glide (my 85 KIAS) is the best middle ground. The plane will be doing quite a bit of accelerating during this climb to 1,000, ram air plus increasing intercooler efficiency. You may need to monitor MP to keep it at or under 37. Somewhere after 1,000 AGL I will then slow the climb rate. I aim for about 120 KIAS true airspeed for the climb to altitude, which continues to be at 36" and full fuel flow, cowl flaps open. That can be all the way to the flight levels. 

Works for me. Then I go LOP for cruise, but that is another story. The engine is at about 400 hours over tbo right now so this does not seem to harm the engine.

3,000 feet seems to me to be a little short for high, hot, out-west operations. Haven't done any calculations, but that seems to me the equivalent of about 2,400 here in the midwest, which is approaching my lower limit unless I am really really in practice with my short field techniques, and I just don't do short field that much. What you are experiencing does not seem that unusual to me if that runway is a high altitude one.

For the other posters, the OP's comment "(indicated, not adjusted for power settings)" just means that he has not run his MP and RPM settings through the Turboplus chart to see what they are equivalent to in an engine without the intercooler. No need to do that for takeoff settings, too much messing around, and in any event during takeoff the effect of the intercooler is constantly changing (increasing).

This^^^^ post covers almost all of the important points.
 

It is very unlikely a fuel flow problem. 22.5gph is plenty of fuel to make 210hp, and if your CHTs are in check, then it’s likely enough to provide adequate detonation margins.

The reduction in MP to account for the intercooler seems like an area worth exploring. OP lives in one of the hottest climates in he country.  No sign that the induction system is leaking, but what about the intercooler’s performance?  Heat soaked airplane, hot air, low airflow at climb speeds and an engine running 4” below stock MP.  
 

Would it not be telling to compare CDT with like models? If the the intercooler is not working well then the reduced MPs mean less power.   There could be many factors at play here including technique. 

 

[A64Pilot]

12 hours ago, Shadrach said:

there is a spreadsheet for calculating LOP Horsepower in the downloads section of this forum.

8.7:1 = 15.14 

8.5:1 = 14.89

7.5:1 = 13.73

7.3:1 = 13.53

Compression ratio drives thermal efficiency. Those OTR trucks are turbodiesels that are running compression ratios in excess of 16:1 or higher.

I think that if you look at any of the boosted, turbocharged aero engine POH’s and compare fuel flow directly to horsepower, you’ll find that they’re  less efficient than they’re higher compression, normally aspirated brethren. 

I understand compression ratio, but the EFFECTIVE compression ratio of a turbocharged engine is much higher when it’s under boost than it’s static compression ratio because of course air is forced under pressure into the cylinder so your compressing pressurized air to start with, you end up with as high or higher cylinder pressure than a NA motor depending on boost, usually higher of course, depending on if your boosting to increase power or just hold sea level power at altitude. 

Just as our NA motors lose effective compression ratio at altitude

Your chart is valid for NA motors, not forced induction motors.

[jlunseth]

I should have mentioned short field takeoff procedure for dealing with a high hot 3,000 runway (or any short runway). I said in my earlier post that for a normal takeoff I put in about 50% of the MP at the start of the takeoff roll, maybe a little less than that, I am not sure it is a feel thing for me. What's going on at that point is turbo lag. The turbo is going to spin up during the early part of the roll and that is going to add quite a bit of MP, so best not to start with a lot of MP. You will feel the turbo kick in and the MP will increase and stabilize. Hopefully you are somewhere around 32-34 inches. That is the time to smoothly put in more MP until you are at 36-37" for the rest of the takeoff. You do need to watch the MP and if it climbs over 37 because of ram air, reduce it back just a tiny bit. On a normal length runway the plane really does not need more than 34-35" to takeoff well, so you have some room to work with the MP.

A short field is different. It is really important in the 231 to use good short field technique, in other words, to line up and get to just short of full power before you let go of the brakes. You do not want to be running down a short strip messing with the MP. You put in the 50% or so with the brakes on, and then, still with the brakes on, ease the throttle up to about 35-36". Don't let go of the brakes until you are there. The 35-36" will give you a little room for the ram air which will happen as you go down the runway and which will raise the MP to about 37." You will need to experiment a little to find out exactly how this will work for you in your aircraft, and the ram air will continue to cause the MP to increase a little during the first few hundred feet of the climb as the aircraft accelerates.

You don't want to make big moves with the MP stick during the run down the runway. A major reason is that the turbo has a tendency to magnify MP changes. The turbo gets its power from the engine exhaust, so if you push the MP stick in and increase the power output of the engine that will in turn cause the turbo to spin faster and increase the power even more, and vice versa if you decrease MP. Going down the runway during takeoff you do not want to make large moves with the MP stick because of this. If you have the Merlyn wastegate this up and down effect will not get out of hand, the Merlyn stops bootstrapping, but it does not stop turbo lag.

[jlunseth]

PS The reasons for putting a turbo in a car and in an aircraft are different. They are used in cars to try to make the engine more fuel efficient and/or to make the engine more powerful, but not for the reasons you might think. Running a turbo is not free, the back pressure it causes changes the way the engine operates. The main reason why turbos increase fuel efficiency in a car engine is because the engine and all the parts in it can be smaller and therefore there is less friction. The turbo produces more power out of a smaller engine. So car manufacturers have progressed to smaller engines with a turbo, that is, to 4 and even 3 cylinders instead of six or eight. A nagging problem with turbos, and in cars in particular, is that wastegate. It does what the name implies, it wastes some of the work the engine has put out, so a turbo will cause the engine to almost always do more work than is necessary. Normal operation of a car is start and stop, and turbo lag is a significant problem in that regard. Today there are a number of solutions that typical involve using something (like an electric motor) to keep the turbo spinning when you are at a stop sign.

Turbos in aircraft engines are to allow the engine, and therefore the aircraft, to operate at higher altitudes. The operation is not start stop like in a car. So to compare the IO360 and the TSIO360, the IO operates at a higher compression ratio. The lower compression ratio of the TSIO causes it to put out almost the same HP (200 in the J and 210 in the 231) even with the turbo, but with the turbo on board  you can sustain that HP output to higher altitudes and make the flight levels if you want.

[A64Pilot]

13 hours ago, Shadrach said:

there is a spreadsheet for calculating LOP Horsepower in the downloads section of this forum.

8.7:1 = 15.14 

8.5:1 = 14.89

7.5:1 = 13.73

7.3:1 = 13.53

Compression ratio drives thermal efficiency. Those OTR trucks are turbodiesels that are running compression ratios in excess of 16:1 or higher.

I think that if you look at any of the boosted, turbocharged aero engine POH’s and compare fuel flow directly to horsepower, you’ll find that they’re  less efficient than they’re higher compression, normally aspirated brethren. 

Problem with charts are most I believe are ROP, and in any High Performance motor at higher power fuel is used to keep temps in check, so yes if your turbocharging for performance and running ROP then it’s likely fuel flow is higher than a NA motor because the higher power will require more fuel to stay cool.

‘However a turbo motor LOP should be more efficient than a NA motor, if nothing else it’s using what is otherwise wasted heat energy, a turbo for example is significantly more efficient than a blower because of course a supercharger rob’s horsepower to make even more than it robbed.

[A64Pilot]

The other large difference between a car turbo and an aircraft is that in cars they are there to significantly boost HP, not so much in an aircraft, they are there to maintain HP, the difference is the amount of boost. I ran over 30 PSI boost in my Duramax, that’s over 90” manifold pressure.

It’s not uncommon in a car to almost double HP with a turbo at sea level, but aircraft engines usually operate at low boost.

You can draw some correlations between the two, but they are different, for example more auto turbos center sections are water cooled now making hot shutdowns not much of an issue.

[Shadrach]

1 hour ago, A64Pilot said:

I understand compression ratio, but the EFFECTIVE compression ratio of a turbocharged engine is much higher when it’s under boost than it’s static compression ratio because of course air is forced under pressure into the cylinder so your compressing pressurized air to start with, you end up with as high or higher cylinder pressure than a NA motor depending on boost, usually higher of course, depending on if your boosting to increase power or just hold sea level power at altitude. 

Just as our NA motors lose effective compression ratio at altitude

Your chart is valid for NA motors, not forced induction motors.

It’s not an “effective compression ratio”. What you’re referring to volumetric efficiency which indeed is increased by by the turbo. Squeezing more air and fuel into cylinders does increase volumetric efficiency, but any increase thermal efficiency is insufficient to make up for the lower CR.  Indeed it’s why reduced compression ratio, boosted engines need to run MPs well above a standard atmosphere to make the same power as their higher compression normally aspirated brethren.  significantly different It’s why a TSIO360 with a compression ratio of 7.5 needs 40” to make 210hp. while a normally aspirated 200 hp IO360 just needs a high pressure, fall morning to do the same. The fuel air ratios are significantly different between the two engines (if anything the turbo needs more fuel for detonation margins). How can a turbo charged engine that needs 37% more  MP to make 5% more horsepower be more fuel efficient if that air is blended with fuel at the same or richer ratio? It can’t…and that is why a well sorted TN system is advantageous.

Back to trucks and diesels. I don’t think anyone makes a normally aspirated compression ignition engine anymore. There’s a good reason for that. Normally aspirated diesels have lousy throttle response. They would be considered undrivable by today’s standards.

 

[KLRDMD]

On 9/22/2022 at 4:21 PM, natdm said:

I keep it a bit higher than that -- further ROP, but I could lower it. Still learning LOP and ROP, so if I do it, I try to stay at the far end of the scale. People say use TIT, vs the highest EGT, etc, I'm still not sure so I just keep fuel flow around 12.5-13gph. TIT is really low though. Am I fine to go far lower than that?

I'm happy to fly with you sometime and review LOP operations on a M20K.

[Shadrach]

32 minutes ago, A64Pilot said:

Problem with charts are most I believe are ROP, and in any High Performance motor at higher power fuel is used to keep temps in check, so yes if your turbocharging for performance and running ROP then it’s likely fuel flow is higher than a NA motor because the higher power will require more fuel to stay cool.

‘However a turbo motor LOP should be more efficient than a NA motor, if nothing else it’s using what is otherwise wasted heat energy, a turbo for example is significantly more efficient than a blower because of course a supercharger rob’s horsepower to make even more than it robbed.

This spreadsheet is for LOP only.  ROP hp calculations are based on mass airflow, not fuel burn. Theoretically all O2 is combusted when ROP so mass airflow is the most important number. Lean side is the opposite. 
Both make for reasonable estimations, but given that there are other factors involved the only way to know is with a torque meter.

[A64Pilot]

31 minutes ago, Shadrach said:

It’s not an “effective compression ratio”. What you’re referring to volumetric efficiency which indeed is increased by by the turbo. Squeezing more air and fuel into cylinders does increase volumetric efficiency, but any increase thermal efficiency is insufficient to make up for the lower CR.  Indeed it’s why reduced compression ratio, boosted engines need to run MPs well above a standard atmosphere to make the same power as their higher compression normally aspirated brethren.  significantly different It’s why a TSIO360 with a compression ratio of 7.5 needs 40” to make 210hp. while a normally aspirated 200 hp IO360 just needs a high pressure, fall morning to do the same. The fuel air ratios are significantly different between the two engines (if anything the turbo needs more fuel for detonation margins). How can a turbo charged engine that needs 37% more  MP to make 5% more horsepower be more fuel efficient if that air is blended with fuel at the same or richer ratio? It can’t…and that is why a well sorted TN system is advantageous.

Back to trucks and diesels. I don’t think anyone makes a normally aspirated compression ignition engine anymore. There’s a good reason for that. Normally aspirated diesels have lousy throttle response. They would be considered undrivable by today’s standards.

 

Do you realize modern more efficient Dirsels have dropped their compression ratio significantly, from the old VW Dirsel 23 to 1 to Mazda’s Skyactive 14 to 1 and average 16 to 1.

They did this to increase efficiency by using the turbo to pack the cylinder.

Yes I know about volumetric efficiency, remember the discussion where I said above 100% is common in an NA motor and you claimed that’s not possible.

‘There are all kinds of NA Diesels made today, but usually smaller motors where fuel efficiency isn’t as important, Turbo Diesels have taken over because they are more fuel efficient.

I know the spreadsheet is LOP, but you said go to cruise charts, and they usually aren’t LOP. So it’s tough to compare LOP NA to LOP turbo by cruise charts

[Shadrach]

35 minutes ago, A64Pilot said:

Do you realize modern more efficient Dirsels have dropped their compression ratio significantly, from the old VW Dirsel 23 to 1 to Mazda’s Skyactive 14 to 1 and average 16 to 1.

They did this to increase efficiency by using the turbo to pack the cylinder.

Yes I know about volumetric efficiency, remember the discussion where I said above 100% is common in an NA motor and you claimed that’s not possible.

‘There are all kinds of NA Diesels made today, but usually smaller motors where fuel efficiency isn’t as important, Turbo Diesels have taken over because they are more fuel efficient.

I know the spreadsheet is LOP, but you said go to cruise charts, and they usually aren’t LOP. So it’s tough to compare LOP NA to LOP turbo by cruise charts

Certainly there are challenges as the the charts I've seen aren't given in like parameters.  My POH only gives power numbers for 100ROP and full Rich (anything<75%).  The 231 gives flows at peak and 125 ROP.  We can however see that book fuel burn for my IO360 is 10.6GPH to make 147.4HP (73.7%) at 100ROP.  A 231 at 125ROP will burn 12.6 to make 147hp (70%).

I don't want to get too far into the weeds on Diesel road vehicles.  There could be many reasons to drop CR in a road vehicle.

Back to aero engines and the question I posed in my last post. How can an engine of the same displacement running 20% to 40% more MP to make the same power while using the same F/A ratio going to be more efficient?  If you're squeezing in more air, you're squeezing in more fuel.  LOP or ROP, the turbo needs more of both to make the same power.

[Shadrach]

1 hour ago, A64Pilot said:

Do you realize modern more efficient Dirsels have dropped their compression ratio significantly, from the old VW Dirsel 23 to 1 to Mazda’s Skyactive 14 to 1 and average 16 to 1.

They did this to increase efficiency by using the turbo to pack the cylinder.

Yes I know about volumetric efficiency, remember the discussion where I said above 100% is common in an NA motor and you claimed that’s not possible.

‘There are all kinds of NA Diesels made today, but usually smaller motors where fuel efficiency isn’t as important, Turbo Diesels have taken over because they are more fuel efficient.

I know the spreadsheet is LOP, but you said go to cruise charts, and they usually aren’t LOP. So it’s tough to compare LOP NA to LOP turbo by cruise charts

I just remembered that you're a Maule guy.  Do you have access to an AFM from an M-5-210C?  Same basic engine as the 231 sans the blown plumbing. Same HP, same RPM redline, different CR and no turbo.

Should be able to get a good idea of the efficiency differences of the two engines looking at the power charts for the IO and TSIO.

[DanM20C]

23 hours ago, natdm said:

I’m flying tomorrow for a bit then headed to KFKA on Wednesday (maybe Tuesday) so I’ll have some time to try what you said.

I"m not far from KFKA, only 30 miles.  If you have time I'd be happy to meet up with you and go over LOP and other 231 ops.   I fly my 231 almost exclusively LOP. 

Cheers,

Dan

[A64Pilot]

3 hours ago, Shadrach said:

I just remembered that you're a Maule guy.  Do you have access to an AFM from an M-5-210C?  Same basic engine as the 231 sans the blown plumbing. Same HP, same RPM redline, different CR and no turbo.

Should be able to get a good idea of the efficiency differences of the two engines looking at the power charts for the IO and TSIO.

Used to be all Maule pubs were available on their website for free download, but I think they turned over pubs to a company that charges now.

However it’s not likely to give you the number we are after, because I’m 99% sure they are all ROP, and if TIT is high, you run richer to cool the exhausts and are wasting fuel.

To do charts we would need LOP charts, which I think are uncommon, and NA motors don’t worry about exhaust temps, but turbo motors do worry about TIT, which of course is high EGT, just measured a little further away.

I’ve tried googling what a turbo does for bsfc and efficiency, and everything is dumbed down, can’t get a simple answer, but large ship motors for instance, they don’t care how big or heavy they are but the do care about fuel efficiency, and they are all turbocharged for efficiency, some are even two stage turbocharged, again for fuel efficiency, the Wartsilia’s for instance are often multi fuel, even gasoline or natural gas so it’s not just a Diesel thing.

Of course a turbo airplane uses more fuel than a NA airplane, because it’s going faster, but fly it right beside its NA brother it should be burning slightly less.

Just like contrary to what would make sense my IO-540 Maule flown in formation with an IO-360 burned slightly less fuel, the 540 must have been more efficient because the power was nearly identical, it wasn’t a big difference, but it was there, which still confuses me, I guess the 540 must be slightly more efficient, or he was flying out of trim or something who knows.