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  #591  
Old 10-23-2020, 04:02 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
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Ok, 1000F after the turbo probably means 1200-1300 before which is in the ballpark of where I'd expect it.

I think you have an EM-4 ECU. If you have V17 software, there are a couple choices for WB voltage scales. Check and see which your PLX uses. Some are 0-5 some .5 to 4.5.

Best to believe the PLX gauge for now if you have their display.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #592  
Old 10-23-2020, 05:45 PM
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charosenz charosenz is offline
 
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Location: Longview, Wash
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Quote:
Originally Posted by rv6ejguy View Post
Ok, 1000F after the turbo probably means 1200-1300 before which is in the ballpark of where I'd expect it.

I think you have an EM-4 ECU. If you have V17 software, there are a couple choices for WB voltage scales. Check and see which your PLX uses. Some are 0-5 some .5 to 4.5.

Best to believe the PLX gauge for now if you have their display.
Thanks for the info. Good to know. I think they're real close. Good for now.
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  #593  
Old 10-26-2020, 12:06 AM
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charosenz charosenz is offline
 
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Location: Longview, Wash
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Default engine stumble

I have a whopping 6 hours on the hobbs now.

This are going well. I am fairly confident I need more pitch on the prop. I will probably do more testing before increasing from 20 to 23 degrees. But it wont be long.

I also believe I know what the cause of the engine stumble. While I have not been able to recreate it, I believe it was my blow off valve cracking open when I exceeded the setting. I took the plane up to 8000ft today to see what the cruise was at altitude, but unfortunately the gearbox just gets too warm (over 180F) when I go past 4500 rpm. today when I was at 8k I took it up to 37 inches MAP to see if the BOV would crack open but it did not. 38" is my self imposed MAP limit.

Since the gearbox was already creeping past 185F I decided against pushing it any higher. The maker of the gearbox (Viking) wants it back to look it over and I am going to send it too him as soon as I get a good stretch of rainy weather but until then I am going to take it easy and get more hours on my Phase1.

I feel confident I will be adding an oiler cooler to the gearbox. But that is another rainy day project. I may also add a 2nd blast tube to the box.

Moving the air inlet over to the cold side did wonders. I rarely see it over 120F. When I actually duct a blast of air over to the intercooler shroud I am sure it will drop at least another 20F. Another rainy day project.

Charlie
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  #594  
Old 10-26-2020, 06:58 AM
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rv6ejguy rv6ejguy is offline
 
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Good progress Charlie.

I might suggest removing the BOV altogether. They don't serve any useful function, are just dead weight and another possible liability. I've never used one in 40+ years of turbocharging engines including race stuff.

With regards to the gearbox temps, what kind of OATs are you flying in?
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #595  
Old 10-26-2020, 08:40 AM
BillL BillL is offline
 
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Default Compressor Surge?

Charlie/Ross I have not read the specifics of this "stumble" condition, but be aware it could be compressor surge. That is when the exit plenum air pressure builds beyond the compressors ability to move adequate mass flow and there is back flow across the compressor for an instant. You would need to look at the compressor maps to see if it is getting close to the surge line, and even if close it is no guarantee that it is ok.

I have been close to large diesels that had surge issues in a test cell and the blowback will knock your hat and glasses off 6 feet away. It can eventually break something if left to perform that way for extended events. Typically recirculating compressors extend that margin.

Not saying the BOV is not the problem or is needed, that is another issue entirely.
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I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.

Last edited by BillL : 10-26-2020 at 09:49 AM.
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  #596  
Old 10-26-2020, 09:50 AM
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Charlie, are you running a V trim TO4 compressor and Stage 3 T3 turbine with .63 A/R?
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #597  
Old 10-26-2020, 11:49 AM
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charosenz charosenz is offline
 
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Ross, Bill,

OAT as varied between 60F to 35F.

I will have to dig out some paperwork for those turbo numbers after I get back from the airport tonight.

Got the comment on the BOV. The stumble has only happened 2 may be 3 times for just a second or two. I have not experienced it again. Even after going up to 37ish MAP, and 5000rpm.

The first time it happened I was climbing and just after turning in to the crosswind leg. When it happened I immediately reduced power and lowered the nose and headed back to the airport. It went away immediately.

The second time I was on downwind. Again it went it happened I immediately reduced power and it went away. I wish I could tell you what MAP I was at when this happened, but I cannot. I was not looking at the MAP GA when it happened and I was more focued on flying. At that instant. It might have happened when I reduce power, I just cannot say. I will do some more testing in the next few days.

You guys have 1000 time more experience that I do, but for what it is worth, I think BOV cracking open, or compressor surge may be it. If compressor surge happens when you back off of a "higher" MAP settings it may be the cause as well.

I do appreciate the help, thank you.
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Last edited by charosenz : 10-26-2020 at 11:53 AM.
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  #598  
Old 10-26-2020, 01:32 PM
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rv6ejguy rv6ejguy is offline
 
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I found your earlier post listing the wheel inducer and exducer sizes and turbine housing A/R. If those are the same now, that would indicate these trims. In which case, you should be nowhere near the surge line in flight which is at about 40hp eq mass flow at 1.1 pressure ratio.

Climb or cruise power puts you miles away from surge, in the middle of the islands around 65-70% compressor efficiency.

If you pull the throttle back slowly, any chance of surge is minimal as the N1 rpm drops immediately.

Surge will manifest itself with chirping or stuttering sound as the air comes back out the through the compressor blades. Intermittent surge doesn't hurt anything but I've never encountered it in my plane in 18 years of flying it with similarly sized components. My turbine A/R is .82 on a 2.2L engine. The .63 should be fine for your smaller engine.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #599  
Old 10-26-2020, 02:10 PM
BillL BillL is offline
 
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Thanks for checking that, Ross, it seems it is all ok. Modern compressors have more margin and with compressor housing recirculation, makes it even less likely. Surge on large turbos on diesels sound differently than you describe, sometimes like a heavy POP as the air reverses through the compressor. The engine never changes, boost drops a little and recovers in an instant.
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RV-7
Lord Kelvin:
I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.

Last edited by BillL : 10-26-2020 at 02:14 PM.
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  #600  
Old 10-26-2020, 03:14 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by BillL View Post
Thanks for checking that, Ross, it seems it is all ok. Modern compressors have more margin and with compressor housing recirculation, makes it even less likely. Surge on large turbos on diesels sound differently than you describe, sometimes like a heavy POP as the air reverses through the compressor. The engine never changes, boost drops a little and recovers in an instant.
The V trim compressor is very old, maybe something like 40 years now but can still work well if matched right.

Surge on automotive sized turbos is usually encountered only on rapid closed throttle assuming they are reasonably well matched and the turbine A/R is not too tight. I've only seen one sustained instance in a car with a way too big compressor tied in with a way too tight A/R turbine housing. The engine refused to accelerate at all above 3000 rpm regardless of throttle.

With regards to BOVs, none of the professional IMSA, Trans Am or F1 turbo cars back in the pre '90s were ever equipped with them to my knowledge and they serve no useful purpose on most aircraft where you never go from full power to idle in less than 1 second. Never used on Sport Class Reno racers where MAP may exceed 100 inches.

If it ain't there, it can't fail... My 2 cents.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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