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  #31  
Old 05-06-2018, 08:50 AM
M McGraw's Avatar
M McGraw M McGraw is offline
 
Join Date: Dec 2012
Location: Greenback, TN
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Default Update

Hello Rob,
My last update focused on testing at fixed timing (20BTDC). I have done significant testing on variable timing both ROP and LOP. I need a few more months to make sure my data is repeatable.

What I can say is the timing curve for ROP is very flat so increasing timing does increase performance, but Iím not certain it is enough of an increase to justify the unknown reduction in detonation margin.

LOP results are trending much better and I do like what I see; however, I really need to make certain my data is repeatable.
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  #32  
Old 05-06-2018, 10:07 AM
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jetmech jetmech is offline
 
Join Date: May 2007
Location: Fairfield, CA
Posts: 96
Default 1st flight

Yesterday I took to the air for a first flight.

Congrats Sir great job and the fun is just starting!
looking forward to seeing the EFII map you post
Lee
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  #33  
Old 05-06-2018, 11:42 AM
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rv6ejguy rv6ejguy is offline
 
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Default

Be aware that most of the modern SDS setups are using different injectors with different flow rates in different placements and orientation from the rebranded setups. Fuel maps will not be comparable as a result.

Ignition maps won't be comparable either unless on the same engine, CR and fuel (and be sure to verify actual ignition timing and Magnet position). Some builders have found actual ignition timing has been advanced 1-3 degrees when checked from the pre-set values.
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Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 422 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
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  #34  
Old 07-31-2018, 10:34 AM
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M McGraw M McGraw is offline
 
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Location: Greenback, TN
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Default Update at 175 hours

I have been testing variable timing for quite some time. It appears my aircraft does best at about 9500PA (11,500DA), 65%PWR173KTAS@11.2gph. Below is a comparison of our return trip from Air Venture 2018. I cannot identify a speed advantage of 125ROP over 100ROP. The screenshot below is at 100ROP at 20BTDC. I have tested ROP timing and found that 23BTDC is optimal; however, the speed increase was not worth the unknown detonation margin for me.


This second screenshot is three minutes later at approximately 30LOP and 27BTDC, 64%PWR169KTAS@9.2gph. The LOP curve proved very very flat. I tested significantly more advance than 27BTDC, but again my tolerance level for running a $40,000+ engine is conservative. When I go LOP I loose about 10kts; however, advancing the timing recovers a significant portion of that loss while saving 2 or more gallons per hour. The leaner the mixture more advance is required. This is simply a snapshot in time. I have gone as far as 175LOP with the engine running smooth at incredible fuel flows; however, the speed was not so incredible.


There is a post from approximately 2 years ago by a Vans pilot (Scott M.) who got 169KTAS at 8.8gph with fixed magnetos. I pay a penalty for increased weight and drag of larger landing gear. My future plan is to compensate with a cowl flap. With CHTs in the low 300s there is ample cooling drag margin to gain what I suspect will be ~5Kts or 0.5gph.
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Last edited by M McGraw : 07-31-2018 at 10:55 AM.
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  #35  
Old 07-31-2018, 10:56 AM
Tom Martin Tom Martin is offline
 
Join Date: Jan 2005
Location: Ontario, Canada
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Default

Here is the RV14 using stock mags last fall on my way to Arizona.

I have been a long time user of one electronic ignition/ one mag, on my previous planes but went with mags for simplicity on the RV14. Both systems have advantages but the numbers on this comparison look pretty similar to the posted images above. The engine is the stock Van's supplied IO390.



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2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
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  #36  
Old 07-31-2018, 11:04 AM
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M McGraw M McGraw is offline
 
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Default 0.5gph

Tom,
That post does align with my suspicion of an ~5kt or 0.5gph penalty for larger landing gear and heavier build. Changes to the original design are not free. There are build decisions I would reevaluate with experience; however, I am willing to accept the penalty for larger gear and the associated friction drag. Another builder posted 169kts at 9.6gph, but acknowledged a heavy left wing which infers additional trim drag. Also, when we compare different airframes we assume each has calibrated fuel flows and airspeeds.

Addendum: I do not believe 11,500DA is the most advantageous altitude for variable timing. higher and leaner will increase the margin. Comparing aircraft with different drag and weight is difficult. I would consider the comparison of a singular airplane under different conditions more reliable.
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Last edited by M McGraw : 07-31-2018 at 12:05 PM.
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  #37  
Old 07-31-2018, 02:43 PM
Tom Martin Tom Martin is offline
 
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Location: Ontario, Canada
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When making changes to my aircraft I always fly beside a buddy before and after the change. We note his power setting for the first flight and then he flies that same setting for the "change" It is very clear if there have been any differences in speed. Using this method you get away from differences in temperature, pressure etc. I used the gps triangle system for many years but the differences in power due to temperature alone made the comparisons difficult.
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Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger flying #153

Fairlea Field
St.Thomas, Ontario Canada, CYQS
fairleafield@gmail.com
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  #38  
Old 07-31-2018, 03:29 PM
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rv6ejguy rv6ejguy is offline
 
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Thanks for posting your timing findings Marvin. The TAS vs. FF seems pretty good with the draggier gear. If it's costing 5 knots then you are burning maybe about .5 to .8 gph less than Tom for the same TAS.

Hopefully you'll find a few knots with the cowl flap. That will be interesting to see too.

175F LOP, wow.
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Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 422 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm



Last edited by rv6ejguy : 07-31-2018 at 03:57 PM.
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  #39  
Old 07-31-2018, 04:01 PM
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DanH DanH is offline
 
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Default

Quote:
Originally Posted by M McGraw View Post
I cannot identify a speed advantage of 125ROP over 100ROP.
That aligns with dyno sources.

Quote:
The screenshot below is at 100ROP at 20BTDC. I have tested ROP timing and found that 23BTDC is optimal; however, the speed increase was not worth the unknown detonation margin for me.
If it helps, other than short experiments, I've been at 23 since the first dyno run.

Quote:
This second screenshot is three minutes later at approximately 30LOP and 27BTDC, 64%PWR169KTAS@9.2gph. The LOP curve proved very very flat. I tested significantly more advance than 27BTDC, but again my tolerance level for running a $40,000+ engine is conservative.
I was out at 35 BTDC, at 16.5K and 30 LOP for a bit last week. Not desirable. Higher CHT and OT, and 5 knots slower.

I'm beginning to suspect flat advance curves are a characteristic of the angle valve. Looking forward to your data.
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  #40  
Old 07-31-2018, 05:32 PM
larrys larrys is offline
 
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Location: Colorado Springs
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Default 14

Awesome!
I am building faster now!!
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