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03-18-2018, 05:55 PM
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Join Date: Mar 2015
Location: Greenville SC
Posts: 178
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I will look at the fuel flow and other suggestions. The only thing I changed was the two p-mags. There is something amiss. May take some searching but should find a solution
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Tim Crouch
RV-9A N626TC
"Merlin"
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03-18-2018, 06:18 PM
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Join Date: Apr 2012
Location: West Fargo, ND
Posts: 1,073
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Did you install the jumper (piece of wire) between pins 2 and 3, or not?
This jumper runs the A curve, which is retarded more than the B curve. Another option is use the B curve and use the EICAD program on your computer to set the timing the same as your standard Mag by setting the max advance to 25 degrees.
Mine ran hot at first and I brought it back to Normal settings, during this process I also switched my top baffle seals from Vans standard material to McFarlane cowl saver material. I was able to make one continuous piece along each side and the back, vs. segmented pieces. I also had a gap at the front inlets, outboard edges, and with the new material, made sure they tucked behind the sides of the inlets. Despite hours of baffle and jetting work, this was the smoking gun; what I thought was a good seal, was not. CHT?s run cool now and have advanced the timing back to 31.4, so far...
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Derek Hoeschen
EAA Tech Counselor
RV-9A #92103 - N803DK
G3X, Superior XO-320, Dual Pmags, Catto 3B
www.mykitlog.com/dbro172/
1974 Bellanca Super Viking - N16AW - Flying
RV-8 #83565 - N184DK - building
1968 Mooney M20C - N6801N - Sold
1956 C-182 - N744W - Sold
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03-19-2018, 06:27 AM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Tim is based about eight miles from me and when he installed the P-mags, I used the EICAD program from E-mag to set the Advance Shift to a -1.4 degrees on both his P-mags (I also lowered his Max Advance by 1.4 degrees), which puts them at 25.2 degrees for takeoff. As with any custom configuration on the P-mags, do you not install "the jumper".
After talking with Tim on the drive in this morning, I do not believe his issue is with the P-mag or fuel delivery. The reason being is that if either were the issue, then all the CHT's would be high due to bad timing or a lean mixture. If he was injected, I would imagine it is possible that a jet could be clogged forcing #3 to run lean.
That brings us to two possible issues, either a baffle seal around that cylinder or a leak on the intake tube for #3. He is going to inspect the intake tube gaskets and hopefully install the cowling and inspect the seals with his borescope. (His prop is out for an inspection, so no flying for a week or two.)
I will also stop by his hangar later this week and verify the P-mag timing is correct. It was correct when we left the hangar after I set them but it never hurts to verify such things.
A thought for all of you installing P-mags but are not planning on an EICommander; Tim does not have an EIC but he did bring the connections for one into his cockpit and terminated them with two female DB9 connectors under his panel. This allows for easy adjustment with the EICAD program. Should he ever buy an EIC, he can simply make a Y cable that goes from both DB9 connectors to the EIC's DB15 connector.
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Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Last edited by N941WR : 03-19-2018 at 06:31 AM.
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03-19-2018, 06:54 AM
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Join Date: Mar 2015
Location: Greenville SC
Posts: 178
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Just a little more information. when I did my first test flight with the P-Mags at cruise I was running the following.
8,000 ft OAT 32
RPM 2270 Manifold 21.9
CHT #1- 326
#2- 348
#3- 345
#4- 354
__________________
Tim Crouch
RV-9A N626TC
"Merlin"
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03-19-2018, 09:27 AM
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Join Date: Oct 2009
Location: Victoria, BC, Canada
Posts: 3,932
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Quote:
Originally Posted by Taltruda
Pretty sure your carburetor has an enrichment valve at wot.. try climbing out at full power, it'll run cooler. You're probably thinking that you are being more kind and gentle to the engine by pulling it back, but in reality, you're leaning it and probably adding stress (heat ).
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#canconfirm. My -6 has conventional mags, but I was struggling with high CHT's on climbout for a while before someone clued me in that throttling back early wasn't the answer. Staying at full throttle kept my temps in check until I was ready to level off and cruise.
Keeping the nose down and climbing at higher airspeed and lower vertical speed also helps... It's great that we can go up at 1500-2000ft/min but doing so reduces airspeed, airflow over the engine, and its ability to carry heat away.
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Rob Prior
1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
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03-19-2018, 09:55 AM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Tim, please confirm ;
1. This happened after installing pmags. No other changes to the aircraft.
2. It only happens on climb.
3. It only is effecting no. 3 cylinder.
Question-------are you still running aircraft spark plugs or did you switch to auto plugs?
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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03-19-2018, 09:57 AM
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Join Date: Jun 2005
Location: Cedar Park, TX
Posts: 3,156
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This thread was started with respect to an O320 that probably has a MA-4 carb which operates quite differently than the carb that you would expect to see on a O360. With the MA-4spa, it is my understanding that throttle position doesn't effect the "enrichment" circuit as it does on the larger carbs.
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Scott Card
CQ Headset by Card Machine Works
CMW E-Lift
RV-9A N4822C flying 2200+hrs. / Cedar Park, TX
RV8 Building - fuselage / showplanes canopy (Done!)
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03-19-2018, 10:18 AM
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Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 2,189
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A friend and his carbureted RV-6 recently had the same issue with one P-Mag. We built the cable to connect it to the computer and re-programmed the P-Mag to reduce the Adv Shift and Max Adv (as well as Max RPM). Current settings are as follows but we're still tweaking.
Adv Shift: -1.4
Max Adv: 36.4 (this is affected by Adv Shift so current max is actually 35)
Max RPM: 2816
Temps are now well under control with no noticeable power loss.
Someone above mentioned the P-Mag is not configurable. It certainly is but not to the extent of some other systems.
Cost of making the cable is about $10 and takes less than an hour. You can run it though the firewall to allow changes by a co-pilot while flying or just tie it down in the engine compartment for ground adjustments. PM me if you'd like more information.
__________________
Ray
RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ AFP FM-150 FI, Dual PMags, Vetterman Trombone Exh, SkyTech starter, BandC Alt (PP failed after 226 hrs)
Catto 3 blade NLE, FlightLines Interior, James cowl, plenum & intake, Anti-Splat -14 seat mod and nose gear support
All lines by TSFlightLines (aka Hoser)
Last edited by Raymo : 03-19-2018 at 10:23 AM.
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03-19-2018, 10:23 AM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by Raymo
A friend and his carbureted RV-6 recently had the same issue with one P-Mag. We built the cable to connect it to the computer and re-programmed the P-Mag to reduce the Adv Shift and Max Adv (as well as Max RPM). Current settings are as follows but we're still tweaking.
Adv Shift: -1.4
Max Adv: 36.4 (this is affected by Adv Shift so current max is actually 35)
Max RPM: 2816
Temps are now well under control with no noticeable power loss.
Someone above mentioned the P-Mag is not configurable. It certainly is but not to the extent of some other systems.
Cost of making the cable is about $10 and takes less than an hour. You can run it though the firewall to allow changes by a co-pilot while flying or just tie it down in the engine compartment for ground adjustments. PM me if you'd like more information.
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That is exactly how I configured Tim's P-mag's. (See my post above.)
Regarding your RPM limit, I would raise that up one notch to just over 3,000 RPM. It is easy to hit 2816 and when you do, the ignitions will stop firing, dumping raw fuel into the exhaust. When the prop slows down and the ignition starts firing again, that raw fuel in the exhaust will light off with a LOUD bang. That causes the pilot to need to change their underpants as soon as they land.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Last edited by N941WR : 03-19-2018 at 10:27 AM.
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03-19-2018, 10:33 AM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by scard
This thread was started with respect to an O320 that probably has a MA-4 carb which operates quite differently than the carb that you would expect to see on a O360. With the MA-4spa, it is my understanding that throttle position doesn't effect the "enrichment" circuit as it does on the larger carbs.
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You are correct Scott. In talking with Tim this morning, he (and I) was thinking it has the enrichment circuit. I'm not convinced it is a fuel delivery issue. If that was it, then all four cylinders would run hot, not just one.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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