Red box

[aviatoreb]

Yes, CHT. Wrong abbreviation. I'd like to know if flying in cold air really does lower CHTs to the point that they would not correlate with ICPs. This is where the direct indication would be nice. I don't think there are any studies or any way to prove at what temperatures CHT no longer provides an indication of pressures both on the high and low side. 

 

I bet that ICPs still correlate to CHT even in arctic air OAT conditions but no one has done the study to state how to shift the table.  It is easy to keep my CHTs to 350 or 360 even on the hottest of days in my we'll baffled rocket, so on an arctic day, I just think it is easy to forget that is possible when the hottest CHT is 310 or so on an arctic day that there could be any high ICP issue.

 

I bet such a table could be made, just that no one has bothered.  I bet it would be simply a matter of experimentally determining how much the table shifts.  I have flown many times in as low as -10F OAT on the ground - and so much colder at altitude - and obviously my CHTs are much cooler at all power settings than if I depart on a hot summer's day in the south at 95F OAT on the ground and even in hot climbs my airplane has excellent cooling, but I do see a difference in CHTs between 95F and -10F OAT.  In the winter I am working to keep the CHTs warm, with climbs with flaps closed and so on.

[Cruiser]

At 10500, definitely. At 6500, maybe. You are close enough. Remember, the red box has fuzzy edges.

[aviatoreb]

John, that's probably the only concrete truth to engine management

 

I have a question though about the 65% and the rest of the numbers used in the red box concept.  I am sold on the concept and I use it, but 65% of what?

 

My TSIO520nb was certified for 310 and 325hp applications, as were the cylinders, and RAM even has an STC (for the C340 and C414 application) to boost the power to 335hp.  But in my application the engine is derated to 100% power = 305hp.

 

.65*335=218, .65*325=211, .65*310=201.5, and .65*305=198.

Or said another way, 218hp is 71.5% of 305hp.

[MooneyCFII]

OK let's clear the air. The more I read this post the dumber I get. If I run WOT 2450 to 2500rpm leaned out to smooth of rough Cht around 380 to 400 degrees and any where from 6500 to 10500 am I in the red or not?

 

I don't know. I don't have your engine manual or PoH in front of me and I can't see your EGT. You really should take out your POH or engine manual and do the numbers. Given that you have a pilot's license, learned to navigate, know how to work W&B problems, etc., I know you can pull out your manual and figure out percent-of-power and then figure out where your mixture is relative to the Red-Box/Red-Fin.

 

But if you insist on someone pulling numbers out of the air, here are my guesses. (Disclaimer -- if you fry your engine based on what I write here pulling numbers out of the air you are on your own.) Your engine is running between 75% - 65% power depending on the altitude you select, at 6500' you are closer to 75% power and should run no leaner than 150F degrees RoP or richer than 40F degrees LoP. At 10,500' where power is closer to 65% you should run no leaner than 100F RoP or leaner than 20F LoP. So look at your EGT and figure out what where you should put your mixture control.

 

Now, as to figuring out percent-of-power, if you are running rich of peak (RoP), percent of power is a function of available air. After all, when running RoP, you have excess fuel and only those fuel molecules that can match up with oxygen molecules can burn to produce power. Once you use up all the oxygen, no more fuel burns even if you add more fuel by running a richer mixture. MAP and RPM determine how much air gets into the engine so they determine percent-of-power when operating RoP. So, What does the POH or engine manual tell you about percent-of-power for your power settings? 

 

When running LoP you have excess air/oxygen and more (all) of the fuel molecules burn. So when you are running LoP the percent of power correlates more closely with fuel flow. 

 

So the process is pretty straight forward:

1. Find your percent of power from the book or maybe use the percent-of-power function from your engine monitor. (I discovered by accident that my EDM930 knows the difference between RoP and LoP percent-of-power and changes the percent-of-power display depending on whether I have selected ROP or LOP operation in the lean-find function.)
2. Now find the red box that goes with that percent of power.
3. Figure out the width of the EGT danger-zone for that percent of power.
4. Adjust your mixture to keep the EGT outside the danger-zone.
5. Cross check with CHT to be sure the engine is keeping its cool. 

I know, I didn't give you an easy answer. Sorry. I know it can seem confusing initially but it is pretty straight forward if you tackle the concepts head-on. OTOH, if you aren't willing to think and learn, you probably should take up something other than flying -- politics maybe. 

[MooneyCFII]

I have a question though about the 65% and the rest of the numbers used in the red box concept.  I am sold on the concept and I use it, but 65% of what?

 

My TSIO520nb was certified for 310 and 325hp applications, as were the cylinders, and RAM even has an STC (for the C340 and C414 application) to boost the power to 335hp.  But in my application the engine is derated to 100% power = 305hp.

 

.65*335=218, .65*325=211, .65*310=201.5, and .65*305=198.

Or said another way, 218hp is 71.5% of 305hp.

 

Different versions of the "same" engine that produce different maximum power really are different engines. There are usually differences in compression, valve timing, crankshaft and rod "beefiness", etc. So use the rated power for YOUR engine, not other versions that you think are the same engine. 

[bonal]

Dude that was way too harsh. I under stand all the concepts and formulas listed here the fact that I want to keep learning is born out that I bother to ask. My POH is very limited on the subject as is my EGT gauge. I guess since I can't afford a fancy engine monitor you might think I should not be a member of this community. I am a very thoughtful pilot and only want to get better. I have some choice words for your comments that only apply face to face

[bonal]

I appreciate the information you posted why ruin it with a cheap shot

[MooneyCFII]

You'd think that, after doing email on mailing lists for 35 years I would learn that it is not possible to make a joke without someone assuming I am trying to give offense. I wasn't and I am sorry. My comment was tongue in cheek. I assumed that since you were here and asking, you would understand that I understand you are seeking assistance. It was not intended as a cheap shot at you ... unless you are a politician too.

 

That being said, there is some onus on you to seek more information if you feel the PoH is not complete. The quality of information in the PoH is all over the map even with different years of the same airplane. My Piper PA-16 "Clipper" came to me with a "PoH" that was nothing more than 3 sheets of single-sided paper stapled together, most of that having to do with W&B and nothing on the engine other than maximum HP spec at red-line.  Other airplanes had quite adequate engine operation charts and diagrams in their PoH. But none of them were what I would call complete.

 

When I buy an airplane almost the first thing I do is go get the engine manufacturer's manual for the engine in the plane. There is a wealth of information that the engine manufacturer gives to the airframe manufacturer that the airframe manufacturer leaves out of the PoH. (After all, the engine manual may be bigger than the aircraft's PoH!) One of the most useful, if not understandable, is a nomograph that lets you calculate percent of power and fuel burn from OAT, pressure altitude, MAP, RPM, and mixture setting. I usually take that and make myself a table to use in the plane for common altitudes and power settings. (I do this for common weight-and-balance conditions too.)

 

And I don't expect you to have fancy instrumentation. In fact, I have found that when operating my 231, I primarily set the mixture using two things: fuel flow and the seat of my pants. I get up to altitude, set my MAP and RPM to yield 62% power, then do the Big Pull on the mixture control until I feel the sudden deceleration that comes with getting on the lean-side of peak EGT and then fine-tune the fuel flow. I then cross check with TIT to ensure that I went past peak EGT by the expected amount. I find the "Lean Find" of my fancy engine monitor to be of questionable usefulness. (Actually it is useful for finding the GAMI spread when determining if I need GAMI-jectors for that particular engine but after that, not so much.) After that I should see my CHT quickly settle to expected values. If they are lower than usual, I have probably over-leaned and am too far LoP. If they are a bit high, I need to lean some more. For this I check using TIT and approach peak TIT from the lean side. Other than the TIT, I don't think I have paid attention to an actual EGT value in a long time, except for trying to troubleshoot a problem like a fouled plug, bad mag, or induction leak. 

 

So I am not assuming anything in the way of special hardware. I do think your airplane should have some sort of EGT indication and probably should have CHT for all cylinders but beyond that, the fancy stuff only really helps with trouble-shooting. Of course, having a fancy engine monitor gives you more information about what is happening. But people have been flying their airplanes successfully for over a century without a lot more information than oil pressure, oil temp, and their ears.

 

Perhaps the best way to ensure you are not going to hurt your engine is to fly it such that it runs at 65% power or less most of the time. Then mixture, red-box, red-fin, etc., just doesn't matter. And for someone flying behind a normally aspirated engine, the easiest way to do that is to fly high. Fly above 10,000' behind a normally-aspirated engine and you just aren't going to have to worry about damaging it through mixture mismanagement. And if you are going to fly low, pull back on the go-knobs and save fuel. Fuel burn decreases faster than TAS does. About the only time it matters is when you are fighting a headwind and need to fly down low. 

[MooneyCFII]

Oh, I forgot to add a link to this useful article:

 

http://www.oshkosh365.org/saarchive/eaa_articles/2012_12_08.pdf

[bonal]

What I find is there are many opinions that tend to contradict. any trip over an hour and I am at 9500 or above depending on winds and based on my POH I am at 76% and 25 deg lean of peak. This I knew I was just trying to get a handle on the whole red box thing.

As for politics no, I am way too conservative even for Texas.

[aviatoreb]

Different versions of the "same" engine that produce different maximum power really are different engines. There are usually differences in compression, valve timing, crankshaft and rod "beefiness", etc. So use the rated power for YOUR engine, not other versions that you think are the same engine. 

 

Not true in this and some cases.  Same TSIO520NB - exact version.  Only difference can be the adjusted timing.  All part numbers are identical.

 

Here is another example: The IO550G in the Ovation 1 was certified with the M20R airframe at 280 horsepower and later the Ovation 3 M20R uses the same IO550G to get 310hp.    But no worry, there is an STC to adjust your Ovation 1 IO550G to output 310hp.  I am not positive but I believe the only hardware change is the prop and otherwise it is the same engine - identical. So what is the Ovation 1 owner with an original 280hp engine supposed to think when deciding what is 65% power? 182hp or 201hp?

[carusoam]

Brian,

How well does your JPI HP% calculation line up with your POH numbers?

It's been a couple of years since JPI and the competitors came out with HP calculations...

LOP numbers were fairly easy to match. ROP numbers did not match all engines under all conditions.

Depending on the individual...

1) memorize a nomograph

2) use the MAPA method. f(RPM + MP). f()= 'function of'

3) memorize a few key points...

Back in the day, I would have memorized and been able to use a couple graphs. (Not so much anymore)

Can you rely on the JPI numbers to set your HP to 65%.

I have a couple short flights that I make regularly, using 5,500' (or so) alt.

It would be nice to set HP from memory or MAPA method and confirm that with a JPI reading.

I can rely on 65% HP to stay out of the fuzzy red box...

Can I rely on JPI and others to tell me if I'm at 65% hp?

Or is the HP display nearly a parlor trick, and, experienced aviators still rely on their memory to avoid the fuzzy box?

I'm interested in your thoughts on this.

Best regards,

-a-

Edit: Thank you Erik (we're writing simultaneously)

I have the IO550(n) with 2700rpm limit. It is a replacement for the original IO550(g) with 2500 rpm limit.

(g) has 280 hp in it's original set up

(n) has 310 hp in it's current set up. Different cylinders, different governor than (g).

[MooneyCFII]

When I was young and flying my father's 182, we had a fancy new Alcor EGT. Wow! High tech! (And in 1968 it was high-tech.) Alcor said, "Best power, 75F rich of peak EGT; normal operation 50F rich of peak EGT; best economy 25F rich of peak EGT." I believed it. I ran that airplane at 50F rich of peak EGT. Of course, if I leaned it the traditional way, i.e. pulled back on the mixture until it got rough and then enriched until it was running smoothly again, I also ended up at 50F rich of peak EGT, so that seemed like the right thing to do. Probably the thing that really saved me was that I lived on the west coast and to go anywhere I had to get up above 10,000' no matter what.  Frankly the fact that most normally-aspirated engines have no trouble making it to TBO suggests that it really isn't as critical as I think people are now making it out to be.

 

Where it becomes more critical is with the turbocharged engines. Flying the earlier Mooneys was about economy more than speed. Then the 201 came along and suddenly we kicked-butt on the Comanches and Skylane RGs. We were neck-and-neck with the Bonanza crowd. The 231 came along and suddenly Mooney was SERIOUSLY in the speed biz. (And there were a lot of blown-up TSIO-360-GB1s along the way too -- shame on Continental for that.) The way to eke out that last 5 knots in order to have the fastest airplane in the air is to run the engine at high power in cruise. That means 75%-80% power. And turbocharging will let you do that at altitude. Now the whole red-box/red-fin thing becomes really important. If you don't pay attention to the mixture you can and WILL shorten the life of your engine. And it doesn't help that the PoH encourages high-power engine operation to achieve the high speeds. After all, the manufacturer wants you to be happy with the lightning-fast speed of your fancy new airplane. Of course, the warrantee is going to run out long before the engine needs to be overhauled at what would ordinarily be mid-TBO so what do they care? (OK, maybe they aren't that callous but their motivation IS different than the owner's.)

 

(I would love to see a paragraph in a POH that tells the truth about lower power settings, engine longevity, and reduced maintenance costs.)

 

Now we know more about engine operation and we have better tools. We know that operating these high-powered engines to get max performance CAN shorten the life of the engine. But now we have ways to see what is really going on in order to prolong life. We should use them. But, in the end, it really does come down to this: reduce the power and your engine will last longer. You will pay less for fuel and maintenance. Period.

 

I was thinking about launching into how TAS doesn't change a lot from 8000'-12000' at wide-open throttle (WOT) with a normally aspirated engine but Norm's articles are good. Read those.

[MooneyCFII]

Not true in this and some cases.  Same TSIO520NB - exact version.  Only difference can be the adjusted timing.  All part numbers are identical.

 

Here is another example: The IO550G in the Ovation 1 was certified with the M20R airframe at 280 horsepower and later the Ovation 3 M20R uses the same IO550G to get 310hp.    But no worry, there is an STC to adjust your Ovation 1 IO550G to output 310hp.  I am not positive but I believe the only hardware change is the prop and otherwise it is the same engine - identical. So what is the Ovation 1 owner with an original 280hp engine supposed to think when deciding what is 65% power? 182hp or 201hp?

 

Apropos to this, yesterday I was on the tour of the Mooney factory as part of the MAPA fly-in. The gentleman from Mooney who was leading our tour group gave a comment on this that was quite interesting. We were looking at a nearly-completed Acclaim when he mentioned that the engine was derated to 280 hp. Someone asked why it was derated and he said that the engine has been made to produce anything up to 400hp with just tuning. He also said that the maximum continuous rated power of ANY of the engines regardless of maximum power output is 265hp. How does this map to the desired percent-of-power? Frankly, I don't know but it seems telling that, no matter how much they are rated for in take-off configuration, they all have the same METO (maximum except take-off) power. 

 

What this tells me is that the REAL answers are in the engine manufacturer's documentation. Once again I recommend getting the engine manual and studying that for more in-depth information. 

[MooneyCFII]

Brian,

How well does your JPI HP% calculation line up with your POH numbers?

It's been a couple of years since JPI and the competitors came out with HP calculations...

LOP numbers were fairly easy to match. ROP numbers did not match all engines under all conditions.

Depending on the individual...

1) memorize a nomograph

2) use the MAPA method. f(RPM + MP). f()= 'function of'

3) memorize a few key points...

 

I have not checked mine over the entire range. The engine manufacturer only provides data for RoP. I checked some data points there and it seems pretty accurate. The caveat here is that JPI has you calibrate the monitor based on actual numbers and temperature (as I recall; I did it about 1.5 years ago) during initial set-up and if you don't, it will likely be way off.

 

Also LoP seems reasonable given the expected power reduction for a given MAP and RPM when operating LoP vs. RoP but I can't say for sure. But it seems like it is right within about 3%. 

 

I started to write about using rate-of-climb to determine available HP but figured that might be more than people want to read right now. 

[carusoam]

ROC will add to the complexity...

But, since you mentioned it.....

I currently climb at full power, leaning within the blue box. (Maintaining Approx 200dF ROP).

Maintaining 120 KIAS to control CHTs

There is a particular altitude that it may make sense to consider to go leaner...

Throttle full forward, prop all the way in, climbing towards the heavens...

Power in the N/A engine declines with altitude...

Leaning in the blue box...

CHTs are in control...

When the JPI indicates 65%, or less...

Would you consider leaning to LOP settings, mid climb?

I thought about this before, then realized that there isn't much to be gained for a few minutes of flight. I don't usually fly into O2 levels.

The O's POH has been "blessed" with LOP performance numbers. But, climb performance numbers are only ROP. Blue box for the old Os, white box for the G1000 crowd.

It makes for a good theoretical discussion at least.

Best regards,

-a-

[rbridges]

I use full rich/full power on take off.  After a few thousand feet, I may start leaning it back, but keep my CHT<360 to play it safe.  is it a bad idea to lean any during the climb?

 

BTW, how did you guys find peak EGT?  is there a # that people use as peak, or did you actually have to find it on your particular plane?

[aviatoreb]

Different versions of the "same" engine that produce different maximum power really are different engines. There are usually differences in compression, valve timing, crankshaft and rod "beefiness", etc. So use the rated power for YOUR engine, not other versions that you think are the same engine. 

 

 

Apropos to this, yesterday I was on the tour of the Mooney factory as part of the MAPA fly-in. The gentleman from Mooney who was leading our tour group gave a comment on this that was quite interesting. We were looking at a nearly-completed Acclaim when he mentioned that the engine was derated to 280 hp. Someone asked why it was derated and he said that the engine has been made to produce anything up to 400hp with just tuning. He also said that the maximum continuous rated power of ANY of the engines regardless of maximum power output is 265hp. How does this map to the desired percent-of-power? Frankly, I don't know but it seems telling that, no matter how much they are rated for in take-off configuration, they all have the same METO (maximum except take-off) power. 

 

What this tells me is that the REAL answers are in the engine manufacturer's documentation. Once again I recommend getting the engine manual and studying that for more in-depth information. 

 

Brian, you have given opposite answers contradicting yourself and then told me to go study my engine manual in depth to figure it out.  Maybe you could choose not to answer all the questions, at least the ones for which you don't know the answer.  No it is not necessarily crankshaft difference, and so forth if we are talking the same exact engine, and no this answer to my question is not in my engine manual since the engine manufacturers don't discuss the red box.

 

So I ask again, perhaps to our good friend from APS from Australia?: with the fact that many engines have different max horsepower ratings (their 100%) certainly between different airframes but even within a given airframe such as the IO550G in the M20R -  and often not a small difference - so which hp number should one use when deciding the % of max horsepower?  E.g in the M20R should one use the 0.65*280=182hp in the Ovation 1 and then 0.65*310=201.5hp as the 65% before and after the power re-rate STC?

[aviatoreb]

In the absence of some authoritative source saying otherwise, Erik, I would use the maximum rated horsepower for your particular engine installation. Wouldn't you agree?

 

Absolutely I would agree - err on the side of conservative - that's what I do.  I am just curious what someone like Darin would say. Someone who has been to "the test stand" at GAMI.

[mike_elliott]

What I find is there are many opinions that tend to contradict. any trip over an hour and I am at 9500 or above depending on winds and based on my POH I am at 76% and 25 deg lean of peak. This I knew I was just trying to get a handle on the whole red box thing.

As for politics no, I am way too conservative even for Texas.

 

In a carbureted "D" model, running LOP is happens chance at best. If you really are, fantastic! Most cannot get a carb'd lyc to run smoothly LOP because of the induction system. With your engine, your fuel flow times 14.9 will give you the approximate HP you are producing. Divide it by 1.80 to find out your percentage  power. (This is only true LOP, not ROP. ROP, use the POH settings) But I digress, if you are 25 LOP at 9500', you are running a very efficient power setting and IMO, very safely

[Cruiser]

In the STC'd IO550G they got 310 HP by increasing the RPM to 2700. Maximum RPM in cruise is limited to 2500 @ 262 HP.

 

The O1 has a max RPM of 2500 for that rated 280 HP (not sure about a cruise limit)

The O2 has a max RPM of 2500 for a rated 280 HP with no cruise limit

The Eagle has a max RPM of 2400 for the rated 244 HP with no cruise limit.

Continental rates the IO-550-G maximum continuous operation of 280HP @ 2500 RPM

 

So, three different aircraft with all the same exact engine (IO550G) plus the factory spec and three different MAX HP ratings. At least two of which have higher than the 265 HP limit stated in an above post.

 

Eric, I think you have a very valid point.

[bonal]

Agreed, as I am just doing what the POH specs out. I lean until I see peak EGT then lean unil it drops 1 hatch mark on the gauge which the POH says is 25 degrees. Keeping an eye on CHT in my normal cruise altitude range I am between 79% and 71% HP I just didn't know what all this red box stuff was all about since there is no mention of the term in my POH. I am getting great performance and my fuel burn is 8 to 9GPH. I went over all my power and mixture settings with the guys at LASAR and my CFI (who has been their ferry and test pilot for over a decade) and they all say I'm doing it correctly. And with respect Brian I want to learn all I can and Mooneyspace is a great resource for me as a still new pilot.

[mike_elliott]

Agreed, as I am just doing what the POH specs out. I lean until I see peak EGT then lean unil it drops 1 hatch mark on the gauge which the POH says is 25 degrees. Keeping an eye on CHT in my normal cruise altitude range I am between 79% and 71% HP I just didn't know what all this red box stuff was all about since there is no mention of the term in my POH. I am getting great performance and my fuel burn is 8 to 9GPH. I went over all my power and mixture settings with the guys at LASAR and my CFI (who has been their ferry and test pilot for over a decade) and they all say I'm doing it correctly. And with respect Brian I want to learn all I can and Mooneyspace is a great resource for me as a still new pilot.

I'm not so sure you are lean of peak now that you describe your process. You are lean of peak on the one cylinder you have an EGT probe on, but might be ROP or at Peak on the other 3. Or it could be the probe is on the leanest cylinder and you are in fact LOP on all 4, with the gauged cylinder (#3 I believe on your engine) being the leanest. (that would be an ideal situation for you not having an engine monitor, but frankly, I don't see that happening often on the O360, more often #2 is the leanest) Your horsepower setting wont be between 79 and 71% at 8-9 GPH LOP it would be more along the lines of 66-74%. But with all that said, at 9500 feet, you are probably very safe if your fuel flow is anywhere close to even across all cylinders and your fuel burn is around 8 GPH. If not, it would be a vibrating monster that you wouldn't want to run at those settings. Since it isn't, that tells a story. Your MP will be about 21" or so at this altitude.

[MooneyCFII]

 

 

 

 

Brian, you have given opposite answers contradicting yourself and then told me to go study my engine manual in depth to figure it out.  Maybe you could choose not to answer all the questions, at least the ones for which you don't know the answer.  No it is not necessarily crankshaft difference, and so forth if we are talking the same exact engine, and no this answer to my question is not in my engine manual since the engine manufacturers don't discuss the red box.

 

 

So I ask again, perhaps to our good friend from APS from Australia?: with the fact that many engines have different max horsepower ratings (their 100%) certainly between different airframes but even within a given airframe such as the IO550G in the M20R -  and often not a small difference - so which hp number should one use when deciding the % of max horsepower?  E.g in the M20R should one use the 0.65*280=182hp in the Ovation 1 and then 0.65*310=201.5hp as the 65% before and after the power re-rate STC?

 

No, I did not contradict myself. I probably should not have posted the anecdote from yesterday at the Mooney factory because that was confusing. Percent of power is based on the rated power of your engine in your airplane, period. If the POH says your engine produces 280hp then your engine produces 280hp regardless of what a similar engine in another installation produces even if you think they are the same engine. That is my conservative answer. (You know, the one you give to the examiner when you are doing an oral.)

 

That having been said, after I read the POH I read the engine manufacturer's manual. After examining that data I may choose to deviate from the POH. 

 

And, no, your engine manufacturer doesn't talk about the red box. Some engine manufacturers say don't run LoP and yet we do and we know it is safe to do so. 

 

It is not unusual for airframe manufacturers to derate an engine, usually by limiting max RPM. In that case the red-box would remain approximately the same because ICPs are more dependent on MAP and induction air temperature (the density of the induction charge) than they are on changes in RPM. (And yes, I am aware that, with fixed ignition timing and at lower RPM the combustion event will complete at an earlier crank angle and that may lead to a difference in ICP due to the volume of the combustion chamber being slightly less but, by and large, MAP *is* the more dominant parameter.) So an engine that is derated by RPM should still have its %power calculated relative to the rated power in the installation. (Which is what I said at the beginning of this message.)

 

So all of this is a guideline. The "red-box" is not absolute. We do know that if you are going to push your engine harder and run at a higher percentage of power, you have to be more conservative about mixture manage and run it more rich on the RoP side or more lean on the LoP side than if you are running at lower power. Conversely, you can climb higher or pull back the MAP and not worry about the details.

[carusoam]

And use the engine manufacturers guidance on % HP

In some cases, Rocket Engineering can supply a load of engine information

Brian,

So do you use the JPI % HP calculation? Or no? (jersey option)

What method do you prefer for %HP calculation? (Personal choice, no wrong answer)

Best regards,

-a-