Explain Turbo Normalized

Kent -- Thank you for all of that
 
AggieMike88 said:
If one has the opportunity of putting either on their engine, which is the better selection? TN or TC?
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For production-certified aircraft, it's unlikely you can legally put an aftermarket turbocharger which boosts MP above SL-std on an existing engine -- too many design, engineering, and test issues. I can't imagine doing that other than a complete engine change.
 
Turbonormalized - make the engine perform like it's at sea level as long as possible until the turbo can't do it anymore. Turbonormalized systems have a critical altitude at which point the turbo can no longer shove enough air through to maintain the sea level performance.

Turbocharged - gives you better than sea level performance by boosting above what the engine would be able to produce at sea level without the turbo.

KISS
 
Even adding TN to a plane is a mountain of paperwork - as I found out a year ago when I had visions of high altitude ops but wanted a turbo to get SL power. A veritable mountain of work. The nice man at the FSDO told me flat out that it would likely take 3-4 YEARS before approval, even if I did everything as quick as they asked me to.
 
AggieMike88 said:
While not stated as such, this was the intent with the question.
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OK, I guess I misinterpreted when you said, "If one has the opportunity of putting either on their engine..." Note that replacing a normally aspirated engine with a turbocharged engine is going to be staggeringly expensive (I'm thinking like $80K for engine, labor, and STC even with the core value of the replaced engine), while turobnormalizing an existing engine might be done for half that price.
 
Dav8or said:
So basically you're saying that some turbo normalized systems are basically just ordinary manually operated turbos were the engine happens to be optimized for 30" manifold pressure operation (compression ratios and timing) with the POH telling the pilot to make adjustments to keep the MP at 30"?

I personally wouldn't buy a turbo that wasn't automatic. The pilot has enough to do already.
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It is not a big deal in my experience. Like you, I thought it would be a problem until I started flying it.

As I climb I advance the throttle to maintain whatever MP I chose for climb. In my case I usually climb at 24". I advance the throttle back to 24" every 1000 ft or so.

But the benefits of a turbo (of any flavor) are huge and, in my opinion, vastly outweigh any negatives.

My airplane is TN and has a red line of 31" MP. However, 31" is not approved for cruise flight. It is for takeoffs and max performance climbs. But 25" of MP is approved up to FL200. That's pretty stinkin' good.

And I can get fantastic true airspeeds up high even at 24" MP. At FL190 I was getting 172 to 174 KTAS at 24" MP on a recent trip. Going east I was getting an additional 10 knots of tailwind (it's summer - winds aloft are light). Cruising at 185 KGS and then hitting 210 KGS during initial descent. Too much fun.

Turbos do have a trade-off, as with anything, of higher maintenance. But to my mind turbos belong on aircraft engines even more than on cars. Our engines go way way higher than cars ever do. Why not take all our HP with us?
 
Mike,
I was looking at this for a while (TN vs TC) as well and this thread has been illuminating for me. Some casual observations that I made as I was doing some research using Cirrus as they have both models, TN up to about 2009 and then offered a TC version as well.

Hard to come up with any definitive conclusions, but these are the observations that I think are fair.

1) TN is run LOP per POH and runs cooler (20-30 degrees CHT), at 380 at cruise.
2) TN is about 10 knots faster at cruise in the FL upper teens. Helps it break that magic 200kts TAS number when at cruise. The TN is slower at less than FL10 than its naturally aspirated brother. Most of the TN cruisers, seem to fly at upper teens as a general rule (short flight exceptions) so they use oxygen as normal operating procedure. If you have kids as passengers, think twice at flying this altitude.
3) It burns more fuel that NA, but less fuel than TC.
4) Criticisms of the SR22 TN versions are that the system was a bolt on to the NA version. That means that they cylinders are run at the same compression ratio as the NA version so they see more wear than their NA counterparts. The TC engines are run lower compression. And, the exhaust systems seem to need to be replaced periodically - both sides - from the higher heat as compared to NA versions.
5) From what I can tell, TN versions seem to get to about 1000 TT and then they need to see some cylinders replaced. It is very common to see 1000+ hour Cirrus with several cylinders replaced. The bottom end of these engines seem to hold up well though so it doesn't necessarily change the overhaul TBO.
6) Maintenance - TN will require additional care - cylinders, exhausts. And, if you need to IRAN the turbos, it'll cost you an extra $12k or so to do that.
7) Cirrus offered the TC post 2009 and generally said, it is slower, burns more fuel, and runs hotter. Not sure the benefit frankly, though I was told that it gives you back (and then some) your cruise speed at less than FL10 as compared to NA versions.
 
At the risk of muddying the waters, Dynon says, "Given the same MAP and RPM, the higher you are, the more power the engine produces."

So a NA engine at MSL at 30"MAP and a TN engine at 10k MSL at 30"MAP will perform differently? I don't get it.
 
GeorgeC said:
At the risk of muddying the waters, Dynon says, "Given the same MAP and RPM, the higher you are, the more power the engine produces."

So a NA engine at MSL at 30"MAP and a TN engine at 10k MSL at 30"MAP will perform differently? I don't get it.
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Two things happen in a naturally aspirated engine. One, you have less pressure in the cylinders in the exhaust stroke so you do less pumping work. And, two, you end up with a little less residual gas in the cylinders which will effect the combustion just a bit. But not so much I would get excited.

Now, throw in the turbo and you get a whole new ball game. You now increase the backpressure during the exhaust stroke so you increase pumping work and residuals. So, you get less power than you would at the same intake manifold pressure with no turbo (and lower exhaust pressure).

But, for the most part, the difference is small considering that you couldn't get anywhere near 30 inches in a naturally aspirated engine at altitude.
 
I'm no engine expert, but I can tell you TN on an A36 is an amazing combination. Climb rate stays strong into the teens making high flight to take advantage winds an easy decision. Combined with LOP ops TN makes the A36 the easiest-to-manage high performance aircraft I've ever flown while being relatively economical in the process. Over on the Beech board I get a sense the TN pilots tend to be much happier than the TC pilots in that particular make and model.

I'm a believer in TN. There's a cost, but it seems to me a worthwhile cost.
 
One little thing Kent, with a fixed waste gate, the amount of boost is NOT constant. Only with a fully deck referenced waste gate is the boost constant.
 
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LDJones said:
I'm a believer in TN. There's a cost, but it seems to me a worthwhile cost.
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Ted's right about it needing to fit your mission to be worthwhile. If you fly out of high-altitude fields or go through the big rocks out west on a regular basis, it's a no-brainer.

However, here in the lower altitudes, you need to be flying long flights to make it worthwhile. At one point, I made a spreadsheet (I do that sometimes) comparing performance at various altitudes for a Turbo Twin Comanche vs. NA. Roughly speaking, the turbo gets there fastest if you climb 1000 feet per 18nm traveled and most efficiently if you climb 1000 feet per 20nm traveled. So, if you never go more than 200nm you'd never climb more than 10,000 feet and the turbo really wouldn't be worth it.

It only becomes worth it if you make frequent trips of 300+ nm. I'd sure like a turbo, but compared to the Ovation (which is a NA bird, it'd have to be sold and a turbocharged Bravo purchased) I'd be sacrificing a little speed and a LOT of fuel burn on my numerous shorter (50-200nm, ~weekly) trips to go fast on the couple handfuls of flights I make per year that are 300+.
 
Henning said:
One little thing Kent, with a fixed waste gate, the amount of boost is NOT constant. Only with a fully deck referenced waste gate is the boost constant.
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You're right - Lower power will result in lower boost on a fixed wastegate.

It's actually somewhat of a positive-feedback loop, which is why, for example, on a Seneca the takeoff procedure is to taxi onto the runway, push to 30" MAP, wait for it to stabilize, then push to 38" MAP and release the brakes, it'll come up to the max 40" MAP on its own.
 
Henning said:
Couldn't you put a TN kit on an Ovation?
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No STC's that I know of... I'd love for someone to prove me wrong on that, although as I stated the turbo wouldn't fit my mission most of the time. The Ovation has enough excess HP even in the normally aspirated flavor to go high when it's advantageous - I've had it to FL190 once, and to 16,000 feet several times. It'll easily do 500+ FPM to around 15,000 feet.
 
Because I do such long trips, a turbo would fit my mission, even though I'm somewhat restricted on altitudes for those missions. Even getting 24" at 11k would result in a significant speed increase, saving me time. But no STCs for the 310 that I found, and we're not trading for a T310.
 
Ted DuPuis said:
Because I do such long trips, a turbo would fit my mission, even though I'm somewhat restricted on altitudes for those missions. Even getting 24" at 11k would result in a significant speed increase, saving me time. But no STCs for the 310 that I found, and we're not trading for a T310.
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Riley had one I'm pretty sure, not sure if it was on a 520. Is the 320 a separate TC?
 
GeorgeC said:
At the risk of muddying the waters, Dynon says, "Given the same MAP and RPM, the higher you are, the more power the engine produces."
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Dynon's article is talking about a normally aspirated engine, and they are correct - If you run 15" MAP near sea level, you'll produce less power than if you're running 15" MAP with the throttle wide open at 15,000 feet because part of the engine power down low will be lost to sucking air past the throttle.

GeorgeC said:
So a NA engine at MSL at 30"MAP and a TN engine at 10k MSL at 30"MAP will perform differently? I don't get it.
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What Dynon is talking about doesn't apply to NA vs. TN in this case. Let's say you have a manual-wastegate system on the TN plane, in BOTH cases you'll have the throttle wide open and the wastegate set so that the turbo provides 30" MP at the throttle plate, so nothing is different with the throttle itself, which is what Dynon is talking about.

However, the TN bird at 10,000 feet will have some slight power losses compared to the NA bird at sea level because it has to pump the exhaust out of the cylinders against the backpressure of the exhaust turbine, and if it doesn't have an intercooler it'll also be working with air that's much hotter than ambient so it'll lose a little more power there - The density altitude inside the engine will be higher, in effect, even though we're not losing MAP the way we do when we climb in a NA plane.
 
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Ron Levy said:
OK, I guess I misinterpreted when you said, "If one has the opportunity of putting either on their engine..." Note that replacing a normally aspirated engine with a turbocharged engine is going to be staggeringly expensive (I'm thinking like $80K for engine, labor, and STC even with the core value of the replaced engine), while turobnormalizing an existing engine might be done for half that price.
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No worries. This is more of an educational series of questions versus developing a plan.

We've got a good way to go before 55WB times out or gets into Mike Busch IRAN territory (I think we just crossed 475hrs on the current motor).

As I review the for sale ads, I see listings for aircraft with TC's or TN's and didn't fully grasp what the pros and cons were. From this thread I'm gaining some good intel on the subject.
 
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Henning said:
Riley had one I'm pretty sure, not sure if it was on a 520. Is the 320 a separate TC?
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There were some Riley STCs in the past that aren't supported anymore, and the 320 is a different TC.

I'm still interested in superchargers. :)
 
AggieMike88 said:
No worries. This is more of an educational series of questions versus developing a plan.

We've got a good way to go before 55WB times out or gets into Mike Busch IRAN territory (I think we just crossed 475hrs on the current motor).

As I review the for sale ads, I see listings for aircraft with TC's or TN's and didn't fully grasp what the pros and cons were. From this thread I'm gaining some good intel on the subject.
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If you're sticking with a 182 airframe, it would be a lot cheaper to just trade it on a TurboSkylane than to try to stuff a turbocharged engine in 55WB. And I don't think there's a TN STC for a regular 182. So, if you want turbo (either TN or TC), you're going to be trading airplanes. In that case, you need to think about why you want a turbo, and then match that with the capabilities of TN vs TC in whatever airframe you decide meets your needs (and depending on whether TN is even available for it).
 
Capt. Geoffrey Thorpe said:
Ummm. No. I explained why a naturally asperated engine will produce a little more power at the same MAP/RPM at altitude.
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That's not the way I read it originally, I guess you are doing both... But it also occurred to me that what I was saying in reference to your post was irrelevant anyway, so I just removed it. :)
 
I have been flying my Turbo-normalized Twin Comanche for almost 2 years now. It has the Miller conversion with the RaJay turbos. Two manual vernier wastegate controllers. I was taught to think of them as extra throttles.

The airplane is placarded to only use turbos after WOT, so after TO, I pull back to 25" then as I climb I increase throttle to WOT. If I want to climb faster/go faster just start in with the wastegates. It takes a few seconds to get them balanced left to right but isn't a big issue. I will sometimes just take the loss in ROC and spool them up in cruise.

On decent, just slowly back out the turbos and then the throttles. You can overboost, but you can also forget to put your gear down. Pay attention and not problems, plus it is on the checklist.

There is a procedure to set them up for high DA takeoffs also.

It is nice to see 1000-1200 fpm climb at 9000 ft. near max gross on a 100 degree day. 200+ knot cruise is sweet also. It does make you think though looking at the orange glow in the louver of the left engine nacelle.
 
bburnett said:
I have been flying my Turbo-normalized Twin Comanche for almost 2 years now. It has the Miller conversion with the RaJay turbos.
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Sweet... I want a ride! :thumbsup:

What speeds do you see at 10K/15K/20K? What power settings do you use?
 
Ted DuPuis said:
There were some Riley STCs in the past that aren't supported anymore, and the 320 is a different TC.

I'm still interested in superchargers. :)
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With your flying, put together a system proposal and go to the FSDO for Exp R&D airworthiness. The Orenda powered Commander has been flying around EXP-R&D for decades now and no restrictions outside of commercial ones. Since you're a charity hauling dogs.:dunno:
 
Henning said:
With your flying, put together a system proposal and go to the FSDO for Exp R&D airworthiness. The Orenda powered Commander has been flying around EXP-R&D for decades now and no restrictions outside of commercial ones. Since you're a charity hauling dogs.:dunno:
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While I could do that and our use would be sufficient as Part 91, in PA they would have laughed me out of the office. Here, who knows, but I'm working on the superchargers idea through normal certified channels.

The idea would have made more sense before having the engines overhauled, then I could've put 10:1 550s in there. Or maybe 11:1, limit takeoff to 25".
 
Ted DuPuis said:
While I could do that and our use would be sufficient as Part 91, in PA they would have laughed me out of the office. Here, who knows, but I'm working on the superchargers idea through normal certified channels.

The idea would have made more sense before having the engines overhauled, then I could've put 10:1 550s in there. Or maybe 11:1, limit takeoff to 25".
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So you want to use a SC for normalization purposes? You gonna put a dump inline or do planetary 2 speed drive (or cooler yet, a CV type drive that is MP regulated)? Putting boost on 11:1s is tricky and temperamental at best, we've done it, but it took some some serious work on the power valve circuit of the metering block to work well, I guess with EFI it's a lot easier to get dialed in. I still need to get to play with an LS engine.
 
Ted DuPuis said:
There were some Riley STCs in the past that aren't supported anymore, and the 320 is a different TC.

I'm still interested in superchargers. :)
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Oh, btw, if an STC isn't supported anymore, can one the use that data to gain a Field Approval?
 
Henning said:
So you want to use a SC for normalization purposes? You gonna put a dump inline or do planetary 2 speed drive (or cooler yet, a CV type drive that is MP regulated)? Putting boost on 11:1s is tricky and temperamental at best, we've done it, but it took some some serious work on the power valve circuit of the metering block to work well, I guess with EFI it's a lot easier to get dialed in. I still need to get to play with an LS engine.
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If I go with the superchargers, it'll be simple and direct drive. My engines are stock 520s, so I don't have 11:1 pistons. Since I'd only be looking for normalized anyway, it could work fine.

Henning said:
Oh, btw, if an STC isn't supported anymore, can one the use that data to gain a Field Approval?
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Probably depends on how much of the data you have and the FSDO you're working with. They've been removing unsupported STCs at the FAA from the list.
 
One data point. I investigated pretty carefully and took my draw-through(because carbed) plans to the FSDO with a materials list, weights, temps, and operation docs. Met with two guys, one from engineering. They said it all looked supportable, and I got a provisional go-ahead for bench testing, no flight.

To bench test, I needed a dyno/torque-meter, engine test stand, club prop, cooling fan, calibrated fuel flow, 4pt EGT/CHT, and some other bits. This is before even mounting the engine on a plane with the turbo.

After some discussion on the phone I asked them to cut to the chase, and the best they could offer was approx 60-100 hours bench under varying conditions, some water vapor intake tests because of the draw-through arrangement, then followed by another 50 or so hours in the air no further than 6 NM from my take-off point, and maintaining glide distance to the runway. After that, I could submit my package of results, and have the engine torn down and measured for crank specs, and rod journal elongation. If that went well, after another 50-ish hours I could possibly get a one-off STC for one airframe and one engine.

They said it would be about 2-3 years, and they gave me some advise about changing to FI, and similar setup to existing aviation wastegate tech. That meant lots more stuff, and weight, and complexity. I gave up. If I were going to go TN for a plane, I would either get a supported STC or go EXP-AB.
 
docmirror said:
If I were going to go TN for a plane, I would either get a supported STC or go EXP-AB.
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Unfortunately, that is the most practical solution right there. I know I'm a hopeless dreamer, but if the Part 23 re-write ever does come to amount to anything, they really need to create an Experimental-Factory Built category that would allow owners of vintage (TBD) certified airplanes to de-certify them, make them experimentals with all the same privileges that somebody buying a completed E/AB plane now enjoys.

It makes sense, it's fair, it would be a big boost to GA and it's the right thing to do. Sadly, the forces of the universe seem to be doing just the opposite and doing the wrong thing.
 
docmirror said:
One data point. I investigated pretty carefully and took my draw-through(because carbed) plans to the FSDO with a materials list, weights, temps, and operation docs. Met with two guys, one from engineering. They said it all looked supportable, and I got a provisional go-ahead for bench testing, no flight.

To bench test, I needed a dyno/torque-meter, engine test stand, club prop, cooling fan, calibrated fuel flow, 4pt EGT/CHT, and some other bits. This is before even mounting the engine on a plane with the turbo.

After some discussion on the phone I asked them to cut to the chase, and the best they could offer was approx 60-100 hours bench under varying conditions, some water vapor intake tests because of the draw-through arrangement, then followed by another 50 or so hours in the air no further than 6 NM from my take-off point, and maintaining glide distance to the runway. After that, I could submit my package of results, and have the engine torn down and measured for crank specs, and rod journal elongation. If that went well, after another 50-ish hours I could possibly get a one-off STC for one airframe and one engine.

They said it would be about 2-3 years, and they gave me some advise about changing to FI, and similar setup to existing aviation wastegate tech. That meant lots more stuff, and weight, and complexity. I gave up. If I were going to go TN for a plane, I would either get a supported STC or go EXP-AB.
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:confused: Why do you need to go draw through with a carb? You just build a plenum box that encases the carb and have a flapper door with a seal on it that leads to the air filter, now when the turbo is online it blows the door shut and pressurized the entire induction system, carb and all, and when offline, engine vacuum sucks the door open and it breaths around the turbo.

With that set up, since it is the most common and a turbo failure won't cut off your fuel supply, it would be much easier to get approved with all the data already out there.
 
Henning said:
:confused: Why do you need to go draw through with a carb?
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We've had this discussion before. It's gravity fuel fed, no pump, with a float that is referenced to atmosphere. So, if the tanks are half full I will have ~3PSI of fuel pressure at the float. Encase the carb(and float) in a pressure box, and as soon as I hit ~6000 - bam, zero fuel pressure in the float chamber. Which means, a mechanical fuel pump, which means a rising rate pressure regulator because we can't over pressurize the float chamber either, which means a pressure line leading to the fuel pump. Don't forget, we now need two carb heat ducts for non-pressure thru the flap, and pressure through the turbo. It just never ends.

I've restored two Avantis with the blow though system and it's a real pain. Getting it tuned is also a challenge. Corvair Spyder did it right.
 
The real thing with certification is that it's both what you know and who you know, as well as which office you go to. In PA, I was told don't even try a field approval for anything, it won't happen. In the Midwest, seems like they're more accommodating. I haven't tried it here yet.

It also depends on what you're starting with. If it's an already certified part in some form, that will be a much easier start.
 
docmirror said:
We've had this discussion before. It's gravity fuel fed, no pump, with a float that is referenced to atmosphere. So, if the tanks are half full I will have ~3PSI of fuel pressure at the float. Encase the carb(and float) in a pressure box, and as soon as I hit ~6000 - bam, zero fuel pressure in the float chamber. Which means, a mechanical fuel pump, which means a rising rate pressure regulator because we can't over pressurize the float chamber either, which means a pressure line leading to the fuel pump. Don't forget, we now need two carb heat ducts for non-pressure thru the flap, and pressure through the turbo. It just never ends.

I've restored two Avantis with the blow though system and it's a real pain. Getting it tuned is also a challenge. Corvair Spyder did it right.
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Carb heat not required with the turbo on, you have full time carb heat. Why not just use an electric pump when the turbo is up? The Corvair Spyder was alright, but I could beat it with the Corvair Monza anywhere but out and out on the highway because of the turbo lag.
 
Henning said:
Carb heat not required with the turbo on, you have full time carb heat. Why not just use an electric pump when the turbo is up? The Corvair Spyder was alright, but I could beat it with the Corvair Monza anywhere but out and out on the highway because of the turbo lag.
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I doubt if an electric pump required for turbo use would pass FAA regs.
 
Henning said:
Carb heat not required with the turbo on, you have full time carb heat. Why not just use an electric pump when the turbo is up? The Corvair Spyder was alright, but I could beat it with the Corvair Monza anywhere but out and out on the highway because of the turbo lag.
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Oh yes you do. Descent with the flapper vane open, throttle part closed, on the pressure box leaves non-turbo operated. No adiabatic thermal rise, and little thermal transfer rise, it would be easy in cold weather(mountains, where I want it) to get carb ice on decel. I've been through this with a pencil half a dozen times. Blow through and carbs and airplanes just is a big hassle.

Don't care a whit about turbo lag in a plane.
 
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