Turbo Sizing (hey Dust, over here!)

[Aaron]

I thought I'd create a new thread for this so we don't go to 5 pages on that thread

 

If you can get the displacement, and operating speed, along with the power you're looking for (and the power developed in the NA version), then I'll be happy to make some suggestions as to turbo size, and walk you through the calcs so we all have a better understanding of turbo sizing.

 

As always before you go buy a turbo, you should call the application engineers at Garrett with all this info in hand so they can make a reccomendation for you. They do this for a living, for me it's just a hobby.

[dust]

Well, it only took the joint info from 10 people that understand turbos to get the message into my thick skull, thanks to all on this site and others off line.

 

Where I stand now is I will probably buy the tsio 360 in a few weeks and in a year or so install it in the plane. Between a few weeks from now and a year from now i will, with help, determine what is needed and have the necessary parts fabbed.

 

I have also learned that this is a turbo charged, not turbo normalized engine, so that will make a diference on the sizing of the turbo, also, it was sugested by largeprime that twin turbos might well be the way to go and on first blush, he very well may be right, seems that the exhaust plumbing might be more compact that way, who knows, surely not me at this infant stage of pre-engine installation.

 

One thing is for sure, I'll have the power I yearn for, he he he and probably a little lighter installation

[Aaron]

Why twin turbo's? I missed that conversation.

 

In auto use, some maufacturers use twin turbos to eliminate turbo lag, such as the 3rd gen RX-7.

 

people who modify RX-7's (Farrel et al.) usually dump this system and go back to a single big turbo system. Why? doubling the turbos quadruples the design headaches.

 

For an aircraft, I can't see why you'd use twin turbo, is it possible you mean "Bi-Turbo" where one turbo feeds each bank of cylinders? This is done on many cars, especially Audi's series of V6 and V8 biturbos, but controlling them can be problematic.

 

Here's an example: Wastegate adjustment. If you use turbo's with internal wastegates, they must be perfectly synchronized. If not, one bank will see slightly higher pressures, producing more power, and the uneven pulses can shatter the crank. You have twice as many intercoolers, twice as many hose clamps that can break.

 

If the TSIO-360 is already a turbo motor, then it should have manifolds already made for it's turbo, the only wrinkle is finding a modern unit that fits, or making an adapter. Making an adapter is far easier than making a whole manifold.

 

Large, why twin turbo?

[LargePrime]

again this isn't about auto's.

 

The reason I thought dust might consider 2 smaller turbos is due to plumbing. In a flat opposed cylinder arraingment it saves you plumbing bot heads intakes and exhaust all over. let me illustrate.

 

Lets assume you put the turbo on the bottom, cause thats where the most cooling is any way, and the traditional exhaust. you fab up aa exhaust that brings the heat to the turbo. Now you need to get the intake back to both heads, and keep all the heat off it you can. I havent seen the engine, but any way you do it I see your intakes running near/along your exhaust.

 

Two small turbos, one for each head would have a very simple exhaust, and straight and fast exhaust into the turbo is better. The intake would also be very simple. You will want an intercooler (dust: does that turbo motor come with an intercooler? Can you get pics?), you could put it on top and avoid the heat under the motor. Dont know about the cowling tho. (dust if you just put the motor in stock how will you do the cowling. are there picks of this motor?)

 

A second (minor) reason is small turbo's are much more common. Not to many 360CID turbo motors, but there are lits of 180CID'ish turbo engines. And lots of dollars into making them very refined.

 

I dont think the redundancy is really a point worth making. complexity (two of most everything) would probablity more than cancel it.

 

Bigger turbos are more efficient, especialy at higher Pressure ratios, an efficency we can not use with our low pressure ratios.

 

Might be a non starter. But I though it was worth suggesting

 

Again this is another cheap "gedankenexperiment".

 

Critical input is requested.

[Aaron]

So, 2 small turbo's, the compressor outlets linked together before the intercooler and throttle?

 

This is very much like the Biturbo V6 in Marbleturtle's car, except his routes the compressor outlet to the intercoolers first (1 on each side) then into a Y-pipe combining the flows, then into the throttle.

 

A few thoughts on this thought experiment:

1)the Non-turbo Continental makes 195 HP, the turbo 360-A makes 210. This implies a very low pressure ratio: At sea level the pressure ratio is around 1.1, at 10,000 feet it would be 1.5

 

2)Even though it's a 360 CID engine, the max speed is 2800 rpms. The non-turbo airflow for this engine is around 250 cfm, turbo'd that would be 400 cfm, so even for a single turbo you're in the "sweet spot" where most turbo's are designed.

 

3)Reliability-If a big single turbo fails, the engine makes reduced power. There's a chance you could have an oil leak, a coolant leak, or both; with two turbos this chance is doubled. So I would say this is all negative, there's no redundancy advantage to having 2 turbo's at all.

 

4)Ease of fabrication-I'm not 100% sure, but it's likely the motor he gets already will have an exhaust manifold hooked up to a turbo (probably why the TSIO-360 weighted in at 60 lbs heavier than it's non-turbo twin) So that's one less part that needs to be fabricated.

 

I dunno, I don't see any compelling reasons to make thing complicated, it's bad enough putting all them pistons and valves and weak crankshafts in front of a propeller

[dust]

hey guys, lighten up, you got me convinced that this is the way to go and I now have an open mind so, right the turbo is on the firewall of the plane the engine is on and I get the total exhaust as part of the engine.

I will have to make wholsale changes to what is there, so if 1 is best then 1 is best, but, two may be easier to plumb, if the wastgate is on the engine and two turbos can be plumbed to it easier than one, then whalla, two it is.

It will be a few weeks until i can get to minneapolis and they can find the engine logs and I now know that if i don't like the setup, then I can change it.

Also many have said that aircraft turbo's take allot of maint, well that clearly isn't true, at least of modern ones and that is nice to know. Thanks again and I can't wait to have the engine in hand, I mean Garage.

[Dave Clifford]

Hey Dust,

You clear out some room in your shop for that thing yet???? I was thinking,,,,,,,hmmmm,,,,,maybe you can store it where you move out the table saw, or the lathe, or the big band saw you got,,wait,,I know!! You can put it where your shaper is!! They probably take up the same amount of space!! What do you think???

[dust]

I know, I can put the shaper where my little air compressor is. your garage. he he he or would you like the table saw better

[Aaron]

Originally posted by dust

hey guys, lighten up, you got me convinced that this is the way to go and I now have an open mind so, right the turbo is on the firewall of the plane the engine is on and I get the total exhaust as part of the engine.

I'm not trying to be overly critical of anyone, were just discussing the pro's and con's here. I hope my posts didn't come across as condescending, they aren't meant to be.

[dust]

So how big is an intercooler anyway?? and exactly what does it use to cool?

[No4]

Two types, air to air and water to air.

air to air looks like a normal radiator but shiny alloy. Compressed air is ducted from turbine to inlet, cooled by passing airflow then it's off to the outlet and to the manifold. These can range from 6*4*1 for a tiddler to 40*24*4 for a monster.

water to air uses a wet radiator cooled in the airflow with a pump sending the water to a cooling bath for the induction air.

try this link.

http://www.superchargersonline.com/intercoolers.asp

What size you need depends on the boost, and therefore charge temperature rise, and outside air temp.

Then you have to ask is it worth the extra ducting drag and weight.

[Aaron]

For your application air/air would be ideal. I would suggest an all aluminum tig welded unit, such as made by Garrett or Spearco. These units don't vary much from manufacturer to manufacturer, but do make sure to buy from an established, proven manufacturer, as there are some fly-by-night outfits who slap these together with poor workmanship.

 

Looking through Garrett's tables, an intercooler which would work well for you would be about 12x12x4.5 inches, and weight about 14.4 lbs (Garrett part # 703522-6001)

 

Garret sizes these based on the following assumptions:

Compressor outlet Temp:250F

Pressure ratio=2

ambient cooling temp: 75F

available cooling air pressure drop: 1 inch H2O

 

Under these assumptions the 12x12x4.5 intercooler should be able to cool the charge air for a 275HP engine by 120 degrees F, with only a .17 psi pressure drop on the charge side.

 

You'll note all of these assumptions are conservative in your case, so this might actually be more intercooler than you need, but as long as the pressure drop, weight and drag are low, more isn't a bad thing.

 

source of info : www.turbobygarret.com

[marbleturtle]

>Then you have to ask is it worth the extra ducting drag and weight.

 

I'm finding in my own research that it is better to reduce drag than increase power in minor increments. But an intercooler can work inside the cowl even without direct exposure to the airstream since the air inside the cowl (while still warmer than the airstream) has a lower temperature than the exhaust.

 

As for two turbos... Aaron is right. The smaller twin turbos are designed to overcome "turbo lag" during acceleration which is important in automobile stop-n-go performance. For continuous power application a larger single turbo works better, even if it is routed further from the head of the exhaust.

[Aaron]

Regarding Drag reduction over increased cooling

 

Thatis one very popular philosophy, and for good readon:

"Every lb of thrust saved by drag reduction is a pound of thrust gained."

 

But let me make a few points to the contrary:

1)If you are going to turbo at any appreciable pressure ratio, then you should intercool, period. Not for increased power, but for increased reliability (less chance of detonation)

 

2)We're talking about a plane that needs an airbrake to get it to drop out of the sky- this ain't no dirty Cessna. How much drag are you saving?

 

(no offense to Cessna pilots nor to the denizens of Wichita, KS intended)

[marbleturtle]

... dirty stinkin' Cessnas... except the 172 I'm getting hours in. It can cruise at 120.

 

Anywho... you can use an intercooler in the cowl to cool the intake airflow. Heat is relative... Atlanta is not so hot after living in Houston. A warm room can still cool you down after a hot shower. The heat in the cowl is not as hot as the heat from the exhaust, so the air in the cowl can still cool the intake through the heat diffuser of an inter-cooler even if it feels relatively hot to us.

 

Airflow from the NACAMCDBA duct does its part to add a cooling air flow into the cowl. If that is not acceptable... you can pop in a few armpit scoops, mount the ic's, and hope you generate more thrust with the drop in intake temperature than drag with the airodynamic change.

 

If you follow John Slade's site, check out the progress of Greg Richter's turbo rotary. He went from obscenely large scoops to oil, radiator, and intercoolers suspended in the cowl away from the engine block. I wish I had the sense to have photographed his engine when I went up to visit him before he swapped in the turbine!

 

[John Slade]

If you follow John Slade's site, check out the progress of Greg Richter's turbo rotary. He went from obscenely large scoops to oil, radiator, and intercoolers suspended in the cowl away from the engine block.

 

MT. This comment caught my attention. Are you saying Greg removed his obscene scoops and kept good cooling? I only saw his engine early on when he had the SCOOPS. I'm interested because I'm trying it the other way - just NACA intake and a cooling fan. If it doesnt cool enough I plan to add armpits.

[Aaron]

Originally posted by marbleturtle

the air in the cowl can still cool the intake through the heat diffuser of an inter-cooler even if it feels relatively hot to us.

Sure you could just stick the intercooler in the cowl. It still will have some drag to it, if it has any airflow at all.

 

I still haven't seen a Cozy in person yet(I hope there's one at the regional fly-in in May!), so I'm only going from what photo's I can find on the web, but why not build an internal duct to direct and smooth that airflow to the required areas (air filter, radiators if any, intercooler). Ducting the flow will result in more efficient cooling and much less drag, compared to the non-ducted case.

 

Now, since I didn't have any numbers the the upper half of my post, here's a worked example as to why you would want to intercool

 

Say we have a 70% efficient compressor, and we're at 10,000 feet. The inlet air is 50F. If you compress just enough to bring the pressure to sea level, the compressor outlet will be at 132F. If you compress to 22.7 psi absolute (8 psi gauge) your inlet will be at 246F!!!

 

If you use an intercooler in these situations, your temps can be lowered to around 72F and 126F respectively. This means you don't have to back out your timing to reduce risk of knocking (detonation)

 

Now on to the power recovery aspects: We can assume that power is directly proportional to air density if everything else is constant. For the normalization case (14.7 psi absolute) intercooling gives a 11% increase in air density, so an 11% increase in power. For the 22.7 psia case, it's 20% more power, but in truth that number is hard to gauge, because the ignition would have to back out the timing with an intake at 246F (making even less power)

[dust]

Well, i gotta tell you, i am just dying to get going on this, but, can't until i get back from a business trip and the log books are found and i go to minneapolis and inspect the engine and i move my table saw into dave's garage. Two things i did find out is that there is no intercooler on the engine now and that the current turbo has the waste gate in it.

Building the cozy doesn't take a support group, but i think installing a new engine set up does.

[Rui]

Have a look at the story on the front page of the Kitplanes (www.kitplanes.com) website about the homebuilt Subaru engine a couple of guys put in an RV. They had a hell of a time with both cooling and turbo sizing. The upshot seems to be that you should always intercool and that if you aren't putting in a wastegate then you better be real sure about the relative sizes of the two sides of the turbo.

[No4]

Thanks for the garrett link Aaron, fantastic stuff. Pick a flow rate and you are away with a 2:1 compression ratio, 3 at the max. The only thing I will have to ask garrett is about the exhaust turbine. I think at 9000 feet and 25 inches MAP, the ratio would be about 4 to 1 and would have it screaming it's nuts off, and ruining the compressor performance. I'm guessing that a larger turbine would reduce the pressure difference. I wonder if this also affects waste gates and dump valves?

In your example @ 10000 I think the temperature should be 26'F(ISA), giving extra density and lower exhaust temps.

Someone was surprised about the bypass gate in the exhaust. If you are only using the turbo for altitude compensation you will be risking overboost, increasing the air temp, increasing the exhaust temp, creating back pressure on the exhaust, losing power for takeoff, and whistling and hissing away as you taxi down the ramp dumping all that boost.

With the bypass, when you reach 3500 feet you flick a switch, and you have a turbo trimmed for those conditions, with reduced risks of over boost and over heating, not to mention improved lifetime. If you are using an engine that needs boost at sea level, you either wouldn't use this at all, or you could use two turbines in harmony. I guess two turbos in parallel would double the flow but not the pressure, whilst two turbos in series would double the pressure but the flow would remain the same.The Rolls Royce Merlin (Spitfire & Mustang)had a two stage altitude compensating supercharger giving 57inches MAP for take off , then still boosting at FL450! I wonder how a cozy would feel up there? pretty frightening I'd imagine.

[marbleturtle]

JS. Greg was nice enough to let me try his Cozy III for size since I was concerned about the Cozy being a little TOO cozy for my frame. At the time I did not know enough about the design to look for specific items on his plane. I did however notice that he had a spectacular looking engine with nice an fittings and clean aluminum radiators. I did look under the plane to see his electric air brake and nose lift. I think I remember seeing the NACA but no forced air ducting. Absolutely nothing like the giant 3 scoop in the photo on your web site.

[Aaron]

Originally posted by No4

In your example @ 10000 I think the temperature should be 26'F(ISA), giving extra density and lower exhaust temps.

If you assume 26F as the ambient temp, the non-intercooled temps are 104 and 214, respectively. An engine could certainly run with a 104F temp, but the power increase from an intercooler (If the intercooler can hit, say 50F) is still around 11%

 

I, for one, an glad I never skydove over NZ. That's frickin COLD!

 

Here in Houston I remember it being in the 35-50F range year round, falling from 15-17,000ft, depending on how close the jet stream was. Of course I was a little pre-occupied at the time...

 

The Merlin engines did use a two-stage supercharger, I think with intercooling between, but keep in mind that compressor technology has come a long way since the late 30's when that system was designed. Compressor rotational speeds were limited by the bearings, and no one could do the calculations on a supersonic compressor wheel.

 

>With the bypass, when you reach 3500 feet you flick a switch, and you have a turbo trimmed for those conditions<

That sounds like a manual wastegate- do people do that? why? An automatic wastegate could keep the inlet pressure at whatever setting you dial in, no matter what the altitude, no extra switch for the pilot to forget.

[No4]

Cheers Aaron,

It's amazing what you can learn from the internet. I always thought a wastegate was on the inlet side. What i described is obviously a manual wastegate I now realise. I've never seen one, just learn't about it in CPL Air Tech.

Yes it can get quite chilly down here in The Land of the Long White Cloud. 26'F is an International Standard Atmosphere figure. In Winter, which is just around the corner for us, it goes below freezing every day, so at 10,000 feet it can be -22'F or less. The sea level air pressure also goes up to 31 inches, pretty good for the motors and wings.

I read yesterday that a Reno Air Race Merlin was running 150 inches mercury manifold pressure, and was jetting water onto the intercooler and radiator, and mixing water and methanol into the fuel to stop it detonating. I think that must make about 4000 hp. I'll really have to make that trip.

How's your Cozy going? and what motor are you intending on using?

I havn't started yet, waiting for a visa and finishing my CPL first, then right into it. I'm planning on the Volvo turbo diesel, but they havn't arrived here yet, I'll probably wait for someone to wreck one in the UK. Don't know what sort of MAP it runs, but I'm guessing it won't use much up to 140hp, then about 15inches for 200hp.

[Aaron]

-*UOTE]How's your Cozy going? and what motor are you intending on using?

Well, I'm firmly in the Mazda Camp, as a matter of fact the engine is about all I have for my cozy

 

I realize I'm a bit backwards here, but here's my reasoning. I'm going to work on the engine for a bit longer, see about getting the bugs out of that system, then I'll start on the plane later this year. I'm delaying the plane a bit until I'm absolutely certain it's what I want to do- This way if I change my mind, I can build a Kit-car instead

 

In the next few weeks I should start rebuilding what I call "Candidate motor #1" a 1988 Non-turbo rotary. Once all of it's systems are working well, I might try to get my hands on a newer turbo model, like the new renesis which weighs 60lbs less than the engine I'm currently playing with.

 

Good luck with the turbodiesel!

[LargePrime]

No4

I had just noticed the Volvo diesel. All alluminum. Should make a good candidate as a flying diesel. Do you have any other info regarding aviation uses for this motor?

dust's application would require a pressure ratio of no more than 1.5 max. closer to about 1.2.

 

Aaron

The rule of thumb in racing was for every 10 degree cooler you got 2% more power. 1% without a turbo.

Does a Renesis really weigh 60lbs less? Where did it all come from? All the dimensions are the same.

 

dust

can you find out how much that exhaust manifold weighs? Where did the intake go? What will it cost to get another new one? What does it weigh?