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  #106  
Old 12-30-2004, 02:17 AM
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David Clifford David Clifford is offline
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Mike,,,,Have you figured out what I will need for my engine yet????? I'm depending on you and i'm gonna start tearing down that "funny looking thing", as dust calls it, VERY SOON.
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  #107  
Old 12-30-2004, 09:55 AM
Nathan Gifford Nathan Gifford is offline
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John,

Pardon my ignorance, but have you considered putting a tach on the turbo. I pretty sure you only need an optical probe to make it work. That way you could tell just how close you are to the turbo max speed.

Also maybe adding a t/c on the outlet of the intercooler may tell you some more about the turbo's performance. You could use a surface mount t/c on the engine's inlet tubing. There would be some lag in the temperature response, but it ought to be close to actual temps (especialling if the piping is metal).

There is also a device from Moore Industries that collects data the same way a PLC does. I believe it samples up to either 8 or 16 points and can be run to a laptop using Wonderware (Marc Z??). You may get lucky and find one of these devices on eBay.
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  #108  
Old 12-30-2004, 10:03 AM
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That's a thought. Turbine speed and heat are the critical issues, so just measure them real-time. Hmmm. I have no idea how to go about installing an optical speed sensor, but I've read that some racers do it. I do have thermocouples on the intake and intercooler. I could move one to the turbo body itself.
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  #109  
Old 12-30-2004, 12:16 PM
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Default Compressor mapping

Hi John,

I calculated a few things on your installation by hand as close as I can figure and downloaded the whole XL file. Calculated VE on a stock 13B at power peak is 93%. Some of the plots on your map have me confused. Compressor maps plot compressor output and are not concerned with compressor inlet flow. In a previous post, I stated engine mass flow is essentially equal at a given hp on a given engine. Hp plots for mass flow should run vertically on the map.

I assumed some figures here: 200hp @ 34 inches/6000 rpm or 40/5000, 250hp@41/6000, 280hp@46/6000. The compressor is poorly matched at SL for all calculated points but a good intercooler will negate some of the high discharge temps here. It is a really nice match at all plotted points between 8,000 and 15,000 feet except when using 40 inches and 5000 rpm for cruise at 15,000 feet where it is pretty much on the surge line. At 20,000 feet at all points the compressor is operating well to the left of the surge line so it would not be useable there. In no case would you be into an overspeed condition up to over 18,000 feet running even 46 inches up there. If you are flying below oxygen levels, the V1 looks fine.

The spreadsheet appears to work although some variables assumed are way off. We see compressor discharge temps much higher than predicted due to heat transfer from the turbine section by conduction into the compressor backplate area. We are currently installing a stainless steel backplate in place of the aluminum one to try to reduce this. I'll report on the findings in a couple weeks hopefully.

I'd keep those boost pressures low. While some drag racing turbo rotaries are producing 600+hp at 9500 rpm +, their lifespans are measured in seconds or minutes at those outputs. The rotary has never demonstrated a good life running high boost for extended periods. There have been many concerns with heat rejection and rotor seal life.

Watch your injector duty cycle at high boost as well. You should have a minimum injector flow rate of 44 lbs./hr. if using 4 to be safe at 280hp. Figuring on .55lbs./hp/hr. and 13 to 1 AFRs.

Ross
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  #110  
Old 12-30-2004, 12:38 PM
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John Slade John Slade is offline
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Hi again, Ross
Lots of valuable data, and I think I understand most of it.
I got the compressor map from Turbonetics web site, then overlayed what I thought was an appropriate graph of PR and lbs/min. Where did I go wrong?

Quote:
The compressor is poorly matched at SL
That might explain the apparant lower power on take-off compared with the stock turbo.
Quote:
In no case would you be into an overspeed condition up to over 18,000 feet running even 46 inches up there. If you are flying below oxygen levels, the V1 looks fine.
That's the exact number I got from Leon, with the same warnings about keeping it rich. I expect I'll use a typical cruise height of 12 - 15k at a much lower HP / fuel flow. I'll sneak up on 46 MAP at 15k and note fuel flow / HP as I go. The max boost target is just for knowing where the limit is, the "occasional" high speed run and bragging rights.

Maybe I need to cut the prop back to get the rpm up for most efficient mid altitude travel, even if this costs me a few kts at the very top end (which I wont use much anyway).
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  #111  
Old 12-30-2004, 01:49 PM
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Default compressor matching

Hi John,

I just see the tangential line on the example map. Not sure what that is. It is very difficult to get an efficient match at SL and at 18,000 feet on most engines. My turbos suffer the same fate but as I'm based at 3500 MSL and climb at 1500-2200 fpm, I'm not at SL long! More important to match the compressor for where you spend the most time which is 7-13,000 feet for most of us. The only bad thing about the poor match at SL is low compresor efficiency and higher charge temps, this is not too bad as the intercooler works well at the lower PRs near SL and we don't spend much time here anyway.

Ross
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  #112  
Old 12-30-2004, 03:11 PM
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The blue line on the compressor map is an excel plot of the data in columns D and F using the same scale as the map image. Change the MAP data in column C or the HP data in column E and the plotted line will move. By manipulating the data you can see what keeps you in the center of the island. That's how I arrived at columns H, I and J as the max boost for the three HP levels shown.
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  #113  
Old 12-30-2004, 05:53 PM
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Default Compressor match

Hi John,

Ok, I've found 3 different xl files listed on this thread but still don't think I have the one that you are speaking of so I can't say if it all makes sense when applied to the compressor map. Anyway, I say you are good to go under the conditions previously noted by running the parameters the old fashioned way.

Ross
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  #114  
Old 12-30-2004, 08:56 PM
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OK. One last try, then I'll give up on using a spreadsheet and, as you say, keep it below 46.

Here's the spreadsheet again.
Attached Files
File Type: xls turbocalculator3.xls (68.0 KB, 41 views)
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  #115  
Old 12-30-2004, 10:27 PM
Nathan Gifford Nathan Gifford is offline
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Quote:
Originally Posted by John Slade
That's a thought. Turbine speed and heat are the critical issues, so just measure them real-time. Hmmm. I have no idea how to go about installing an optical speed sensor, but I've read that some racers do it. I do have thermocouples on the intake and intercooler. I could move one to the turbo body itself.
I think someone else suggested the optical speed sensor on the turbine. I don't remember who. I think he was recommending one used by R/C turbine freaks. If I recall correctly he suggested a speck of paint on the compressor rotor.

If you go with the Moore Industries hardware, I know they make a serial unit. However, I am pretty sure they probably build an Ethernet version and that style will probably work way faster.
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  #116  
Old 12-31-2004, 12:45 AM
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see post # 1 for a great description

http://canardaviationforum.dmt.net/s...hlight=optical
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