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  #31  
Old 01-04-2005, 05:07 PM
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Your most pobably right for a rotory guy on a t61, but i'm the lone continental guy, and i am just attempting to pull 31.5, my rated 210 hp on my tsio360
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  #32  
Old 01-04-2005, 05:48 PM
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Default Turbo matching on Cont

The T61 would be even worse on your engine, way too big. A TO4E super-40 would be a pretty good match overall, not too good below 5000 feet but great in the range of 10,000 to 25,000. Pretty hard to get a good match everywhere with this range of altitudes.
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  #33  
Old 01-05-2005, 01:00 AM
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Quote:
Originally Posted by rv6ejguy
The T61 would be even worse on your engine, way too big. A TO4E super-40 would be a pretty good match overall, not too good below 5000 feet but great in the range of 10,000 to 25,000. Pretty hard to get a good match everywhere with this range of altitudes.
Can you elaborate a little more regarding the T61?
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  #34  
Old 01-05-2005, 11:24 AM
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Default T61 compressor

I worked all the numbers for a 13B and Cont 0-360. This compressor is suited to engines more in the 320-360hp range at higher altitude due to its narrow map and relatively large flow rate. It will work on these engines below 10,000 feet and low manifold pressures but it is not operating in a very efficient part of its map even here. For instance on the 13B at 40 inches and 5000 rpm/ 200 hp, it is already to the left of the surge line at 15,000 feet.
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  #35  
Old 01-05-2005, 12:03 PM
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Quote:
Originally Posted by rv6ejguy
I worked all the numbers for a 13B and Cont 0-360. This compressor is suited to engines more in the 320-360hp range at higher altitude due to its narrow map and relatively large flow rate. It will work on these engines below 10,000 feet and low manifold pressures but it is not operating in a very efficient part of its map even here. For instance on the 13B at 40 inches and 5000 rpm/ 200 hp, it is already to the left of the surge line at 15,000 feet.
Right now I'm interested in finding the right one for the Continental O-360.

Looking at the spreadsheet, we need a corrected suction flow of 41 lbs/min at 25000 ft at 2800 rpm. That's a pressure ratio of 3.36. The TO4E super-40 doesn't cover that. What am I missing?


dust,

Here's a TO4E super-40 for $450.

http://www.turbocalculator.com/map-t...er%2040%20Trim

A T-61 is $650

http://www.turbocalculator.com/map-t...=Garrett%20T61
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  #36  
Old 01-05-2005, 12:55 PM
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Default Compressor maps

I think several people on the post are confused about compressor maps. I'm not working from the spreadsheet as there are certain unknowns on the VE which require additional calculations. Approx engine mass flow for 210hp is 26 lbs./min. This is the figure to match the compressor to.

Additionally, it is important to run not just max power and climb power numbers but also in a cruise condition at altitude as this invariably runs the compressor closer to surge as mass flow and hp is reduced. Unfortunately, to obtain at least 60% compresor efficiency at SL and staying right of the surge line above 15-25,000 feet on many applications is often difficult. We generally accept lower compressor efficiencies near SL as the PRs are low and intercooler effectiveness is high, dropping charge temps into the reasonable range. Matching a compressor well for aircraft used below 13,000 feet is generally easier.

For the others reading this post, low compressor eficiencies result in higher compressor discharge temps. Running the compressor near, on or to the left of the surge line is to be avoided. Surge is essentially a condition of stalled or reversed flow through the compressor and the engine will not run properly if this is encountered. The characteristic sound you hear on turbocharged engines when closing the throttle abruptly is surge and the air is actually flowing backwards through the blades making a chirping sound. This can damage the compressor at high boost if it is severe enough. Some lay people attribute this sound to the wastegate opening (incorrect) as the wastegate is closed when the throttle is closed. Some auto engines fitted with blowoff valves make a different sound, more of a whoosh or hiss as the throttle is closed. These valves are fitted to eliminate surge.

Last edited by rv6ejguy : 02-19-2006 at 09:43 PM.
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  #37  
Old 01-05-2005, 01:18 PM
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I am not confused at all, have gone over them with a few very informed people and what you are saying is just not adding up, i wish it did, but all of the other experts agree that the airflo must be corrected for altitude and you are not doing that.
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  #38  
Old 01-05-2005, 02:48 PM
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Quote:
all of the other experts agree that the airflo must be corrected for altitude
... except for me! But I'm no "expert."

I thought the pressure ratio on the turbo map accounted for that! 45 lbs at sea level was 1.5 ratio (IIRC)... 45 lbs at a higher altitude was just a higher pressure ratio moving you up the map. But NNNOOOOOO... nobody listens to MT. uh uh. Nope. Not one bit...
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  #39  
Old 01-05-2005, 03:03 PM
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Default Turbos

Well, I won't debate it. Been building turbo race/ street engines professionally for 25 years and flying/testing our turbo RV6A for a year. Someone might find something interesting on our site : http://www.sdsefi.com/air9.html
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  #40  
Old 01-05-2005, 03:20 PM
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Quote:
Originally Posted by rv6ejguy
Well, I won't debate it. Been building turbo race/ street engines professionally for 25 years and flying/testing our turbo RV6A for a year. Someone might find something interesting on our site : http://www.sdsefi.com/air9.html
You know your stuff on the ground - i think you should open up your thought process to go sky high.

The ambient pressure at altitude does not allow the turbo to grab the same amount of air at altitude with each revolution as it does at sea level, the effect is that at each revolution it is pumping much less air than it would at sea level, that is why the size of the turbo is much larger than you would put on a car at sea level for the same performance.

In laymans terms, as that is just what i am a struggling layman.
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  #41  
Old 01-05-2005, 03:49 PM
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Default Turbos

Been matching turbos for homebuilt aircraft for almost 9 years now. All are working well that have flown to date. Have resized 2 for others who had problems with their originals which were too large and they had surge issues in cruise at reduced power settings.

Anyway, interested in John's numbers when he gets a chance to record them and anyone else who is actually flying anything turbocharged.
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  #42  
Old 01-05-2005, 04:20 PM
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Well, not flying yet, just trying to make the right decisions before i start flying. Garrett tech support, turbo calculator and our spreadsheet ALL basically agree.

Do NOT want to argue, just want to learn and make the right decisions. Sorry you just want to tell me what is right and then expect me to ignore the manufacturers advice. Just can't roll over that easy without more information.
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dust

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  #43  
Old 01-05-2005, 06:03 PM
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Default Airflow

Just sharing my real world experience with people, like anything else you read, you can discount it if you wish.

Hell, I could be wrong too! If so, I appologize to everyone for wasting their time. The Garrett engineers are certainly the real experts since they develop the stuff. If they tell you a T61 will be a good match, I'd listen to them too if they show you the calcs.

The airflow assumptions typically made by many people matching turbos to modern auto engines are just that- assumptions. The often used 80% VE is way off for any modern 4 valve or rotary engines for instance and more suited to '70's- 80s era V8s with lame camshafts and poor cylinder heads. It is easy to verify actual airflow on a dyno or calculate it from hp obtained on a dyno. A Stock Subaru EG33 at power peak is 114% for instance and over 120% at torque peak. Using 80% like is recommended by Turbonetics for matching this engine would result in the mass flow numbers to be off by up to 50%! The whole calculation is invalid at that point. After making hundreds of dyno pulls over the years on my own dyno and other's I can say this for a fact.
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  #44  
Old 01-05-2005, 08:20 PM
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Quote:
Originally Posted by rv6ejguy
The often used 80% VE is way off for any modern 4 valve or rotary engines for instance and more suited to '70's- 80s era V8s with lame camshafts and poor cylinder heads. It is easy to verify actual airflow on a dyno or calculate it from hp obtained on a dyno.
What are the VE's expected to be on a mildly ported 13B?

Also, I know you shouln't be at or to the left of the surge line, but can you explain what exactly happens at surge?
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  #45  
Old 01-05-2005, 09:32 PM
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OK, guys. Slow down a bit here.

I think VE means Volumetric Efficiency ...... but what does THAT mean, and why does it matter?
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