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  #1  
Old 12-10-2019, 03:16 PM
219PB 219PB is offline
 
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Location: Victoria, Tx
Posts: 375
Default Tuning of fuel injection systems

I would like to start a thread on tuning of electronic fuel injection systems such as EFII or SDS. I have an EFII system and I am assuming that my questions below would be applicable to SDS as well.

Let me start by saying that I DO NOT WANT THIS TO BE A THREAD THAT BASHES ANY ONE OF THE SYSTEMS! There are several us out there that want to have a communal discussion on the various strategies around tuning the systems without all of the drama that has derailed other threads in the past.

I have an O2 sensor installed and I initially optimized the fuel flow at each RPM setting based on the air/fuel ratio readings.

With that all done, here are my questions to the group to see how you might have addressed it.

1. When I take off at 2600 rpm, my engine is developing good power but after about 30 seconds my CHT climb to 425 very quickly and keep climbing if I do not richen the mixture significantly. After I richen it, the aircraft still climbs well so I leave it there. Do others just program the ECU to richen the fuel mixture every time the engine is operating at 2600?

2. I cruise at 2300 rpm at 25 Hg and lean the engine aggressively. I am seeing 170 mph at 7.5 gph with CHT's at 380 or below. My typical practice is once I am configured for cruise, is to manually lean the mixture with the electronic knob. Then I have to return it to "normal" for the decent. Should I tune the engine to run this lean automatically at 2300?

3. When I am in the pattern and cross the number on the downwind leg, I will pull the power to idle and get some popping in the exhaust. If I richen the mixture, the popping with stop. I have been adjusting the MAP curve to richen the mixture as the MAP goes down but my plane in getting painted right now and I have not finished working it out yet. How has that worked out for others?

These are the issues that are affecting me directly at the moment. I am looking for how others have addressed these issues and would like to discuss issues that others are having. Might be something that I have not thought of yet.
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RV-6A Airworthiness Inspection 8/10/19
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  #2  
Old 12-10-2019, 04:52 PM
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Toobuilder Toobuilder is offline
 
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For the take off event, what is your typical AFR and ignition timing?
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  #3  
Old 12-10-2019, 05:27 PM
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Paul, do you have gold ECUs? If so, what version of software do you have? Can read that in the bootup screen.
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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- 436.1 hrs. on the Hobbs,
RV10 95% built- Sold 2016
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http://sdsefi.com/cpi2.htm



Last edited by rv6ejguy : 12-10-2019 at 05:29 PM.
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  #4  
Old 12-10-2019, 05:53 PM
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M McGraw M McGraw is offline
 
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Paul,
Most of what you describe sounds like an engine running too lean and possibly with too much advance.

When I was setting up my EI/EFI system I fixed the ignition timing to the Lycoming dataplate until I had the fuel flows established. That way any high CHT should be a result of poor baffles or inadequate fuel flow. Later, I slowly advanced the ignition to get my desired profile. I would look at advance and fuel separately.

My AFRs are set at 12 to 12.5 at RPMs from 500 to 1500. Above 1500RPM my AFRs are set to 11.5 to 12.0 (these are recommended by my system's manufacturer).

Below is a link to a past post by Dan Horton. The part in the middle about checking your full throttle takeoff power with the mixture knob zeroed is very important.

http://www.vansairforce.com/communit...1&postcount=10
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Last edited by M McGraw : 12-10-2019 at 05:56 PM.
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  #5  
Old 12-10-2019, 09:08 PM
219PB 219PB is offline
 
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Quote:
Originally Posted by Toobuilder View Post
For the take off event, what is your typical AFR and ignition timing?
I believe that was set to 14:1. The plane is in the paint for the last couple of months. Hope to get it back in a week or two.
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  #6  
Old 12-10-2019, 09:12 PM
219PB 219PB is offline
 
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Quote:
Originally Posted by Toobuilder View Post
For the take off event, what is your typical AFR and ignition timing?
Sorry, forgot to finish the reply. I did not change the factory timing settings. Did not even get to that screen. I really would like to spend some time, even pay someone experienced with he tuning of these units, to provide some insight.

Was instructed to start by modifying the fuel map to get the recommended AFR.
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  #7  
Old 12-10-2019, 09:14 PM
219PB 219PB is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
Paul, do you have gold ECUs? If so, what version of software do you have? Can read that in the bootup screen.
I do have the gold units. I do not have access to the plane right now as it is getting painted. I did do an update around August with the latest firmware supplied. Will update this thread when I get the plane back.
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RV-6A Airworthiness Inspection 8/10/19
Phase 1 testing complete
In paint shop
My Builders Website
Victoria, TX
2019 Dues Gladly Paid
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  #8  
Old 12-10-2019, 10:52 PM
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14:1 is pretty lean for takeoff power so that's a contributor. Let us know what the timing is doing - that's another big one. Assuming you are a standard compression PV engine, you should be under 25 degrees total advance. What's your typical DA at your home airport?
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
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RV-8 - Flying
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1984 L39C - flyable, available for sale
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  #9  
Old Yesterday, 07:15 AM
219PB 219PB is offline
 
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Quote:
Originally Posted by Toobuilder View Post
14:1 is pretty lean for takeoff power so that's a contributor. Let us know what the timing is doing - that's another big one. Assuming you are a standard compression PV engine, you should be under 25 degrees total advance. What's your typical DA at your home airport?
My DA is usually 2-3K. My engine is a 360 with 8.5:1 compression. I need to get into the system to see how the timing is managed. Will do when I get the plane back.
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RV-6A Airworthiness Inspection 8/10/19
Phase 1 testing complete
In paint shop
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  #10  
Old Yesterday, 08:26 AM
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DanH DanH is online now
 
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Quote:
Originally Posted by 219PB View Post
I have an O2 sensor installed and I initially optimized the fuel flow at each RPM setting based on the air/fuel ratio readings.
Learn to use EGT indications also. They will remain accurate long term.

Quote:
1. When I take off at 2600 rpm, my engine is developing good power but after about 30 seconds my CHT climb to 425 very quickly and keep climbing if I do not richen the mixture significantly.
What Mike and Marvin said.

Quote:
2. I cruise at 2300 rpm at 25 Hg and lean the engine aggressively. I am seeing 170 mph at 7.5 gph with CHT's at 380 or below. My typical practice is once I am configured for cruise, is to manually lean the mixture with the electronic knob. Then I have to return it to "normal" for the decent. Should I tune the engine to run this lean automatically at 2300?
Tune to produce rated power for all RPM/MP combinations, with LOP set manually. LOP is reduced power "dial-a-speed" or "dial for dollars", depending on your view. The system you have will allow a rather wide choice of how far LOP you want to be. For example, I might use one lean setting for high, fast cruise, and a much leaner setting for loafing around the local area down low on a nice Sunday evening.

That said, the real issue with setting your zero knob position for LOP cruise at 2300 is how to make the transition from best power to LOP. If I understand correctly, programming a best power mixture at WOT/2600 and a LOP mixture for 25/2300 will have the system "smoothing" or extrapolating everything in between. No serious study here, but I suspect you would be undesirably lean in the 75-85% power area.

Ross, you've thought about this point more than I have. Got a scheme?

Quote:
3. When I am in the pattern and cross the number on the downwind leg, I will pull the power to idle and get some popping in the exhaust.
Set whatever makes you happy. The popping won't hurt anything. Richer will make it go away, as you note. Or you could try going even leaner. Many automotive EFI's deliver zero fuel on the overrun. Might make airplane passengers nervous, but it will work
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