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  #121  
Old 08-17-2020, 01:24 AM
rightrudder rightrudder is offline
 
Join Date: Mar 2014
Location: Laguna Hills, CA
Posts: 1,853
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[accidental double post]
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Doug
RV-9A "slider"--sold in July 2021
Flew to Osh in 2017, 2018 & 2019!
Donation made for 2021
You haven't seen a tree until you've seen its shadow from the sky -- Amelia Earhart

Last edited by rightrudder : 08-17-2020 at 01:28 AM.
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  #122  
Old 08-17-2020, 01:26 AM
rightrudder rightrudder is offline
 
Join Date: Mar 2014
Location: Laguna Hills, CA
Posts: 1,853
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James, congrats on getting your RV-6 flying!

I too was having trouble keeping the CHTs down when climbing out in 100-degree ambient temps, but it now runs significantly cooler with baffle modifications made to the No. 2 & 3 cylinders. It gets airflow past the "zero fin depth" part of the cylinder and cools the lower part. This thread has some examples. I did something very similar to post #15.

https://vansairforce.net/community/s...d.php?t=163788

Try everything else that you and others have mentioned first. Another option is a cowl flap (which I have), but I found the baffle changes were more effective.

Good luck!
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Doug
RV-9A "slider"--sold in July 2021
Flew to Osh in 2017, 2018 & 2019!
Donation made for 2021
You haven't seen a tree until you've seen its shadow from the sky -- Amelia Earhart

Last edited by rightrudder : 08-17-2020 at 01:28 AM.
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  #123  
Old 08-17-2020, 11:15 AM
jamlip jamlip is offline
 
Join Date: Jun 2017
Location: Palm Springs, CA
Posts: 141
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Thank you Doug - that is interesting reading.

Guess I need to go hunt down a 60s Cherokee to inspect. For the time being, I may do the washer mod, if it hasn't beed done already.

One thing that occurred to me after going through this with my friend Brett Zefting (also of this parish, just finishing-up an RV-8) is that I may have just spent too long running this thing on the ground.

To be honest, I was kind of freaked-out about flying it. There's something about jumping in a homebuilt aeroplane of unknown provenace, that you didn't build yourself, and that hasn't flown for over a decade, and firing yourself into the sky.

So I ground ran it for a while whilst I re-familiarised myself with the EFIS, then did a long taxi down to the 13 end of PSP's huge runway, then sat there and went through my preflight checklist twice, then waited for an Embraer to land, and then took off. The engine was hot from the moment it left the ground. I assumed it would cool down as I flew, but it was 115F OAT with 22% humidity, and it just didn't. I diverted into Thermal, which, as the name implies, is also an extremely hot place, and then flew home.

Probably should have picked early morning on a cooler day, but I'd be waiting another month or so for that to happen.
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Palm Springs CA
1992 O-360 CS RV-6
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  #124  
Old 08-17-2020, 05:52 PM
Lars Lars is offline
 
Join Date: Nov 2005
Location: Davis, CA
Posts: 1,191
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I have a coupla thoughts about it, having seen that plane in person, and having spent a bunch of time recently tinkering on your ex-4. Emags can be too advanced, for sure. Though I'll bet that's only part of it. I'm too lazy to try to type out all the thoughts that are going through my feeble brain, but if you are interested, give me a call if you can stand talking to a boring old guy. I'll PM my #.
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Lars Pedersen
Davis, CA
RV-7 Flying as of June 24, 2012
1120+ hours as of August 17, 2021.
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  #125  
Old 08-18-2020, 02:04 AM
jamlip jamlip is offline
 
Join Date: Jun 2017
Location: Palm Springs, CA
Posts: 141
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Just back from another midnight cool-ish-air hangar thrash.

I dropped the oil. It's pretty discoloured and there is a slight glittery appearance, like you'd see at a 25 hours change. This oil has done about and hour, if you include all the ground runs and taxiing.

I removed and cut open the filter. No sign of anything untoward. This was the largest chunk I could find.



I've packaged up an oil sample to send to Blackstone. I'm not sure what they'll tell me apart from '"it's burnt to heck", but at least it starts a trend for future monitoring. If there is a future for this motor.

Threw a boroscope in the cylinders. The walls look glazed, although they're the blue-top Nitrided ones, so they do tend to. I noticed this when I first inspected the cylinders about a year ago. The edges of pistons three and four looked a tad rough, like they could have detonation damage, but again, could be just freaking out.

I'll aim to do a leakdown test tomorrow. That should answer those questions.\

At some point I'd like to do a write-up on how this all came to happen. It was a series of things aligning, like the swiss cheese effect that usually precludes accidents.

Anyway, more to come. Stay tuned if you like reading about people doing stupid ****...
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Palm Springs CA
1992 O-360 CS RV-6

Last edited by jamlip : 08-18-2020 at 02:08 AM.
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  #126  
Old 08-18-2020, 02:20 AM
jamlip jamlip is offline
 
Join Date: Jun 2017
Location: Palm Springs, CA
Posts: 141
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Quote:
Originally Posted by Lars View Post
Emags can be too advanced, for sure. Though I'll bet that's only part of it.
I've dialled the Emags back five degrees so I should now be running 29 degrees advance. Noticed the intake tube nuts were slightly loose, which made me wonder about a lean condition. That might a bit of a reach.

The baffling on the engine is actually pretty nice. I would like to do the mod to get air down the back of cylinder 3.

That's enough for now, off to bed. More shennanigans tomorrow night...
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Palm Springs CA
1992 O-360 CS RV-6
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  #127  
Old 08-18-2020, 06:22 AM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 1,135
Default Maybe timing...

Quote:
Originally Posted by jamlip View Post
I've dialled the Emags back five degrees so I should now be running 29 degrees advance. Noticed the intake tube nuts were slightly loose, which made me wonder about a lean condition. That might a bit of a reach.

The baffling on the engine is actually pretty nice. I would like to do the mod to get air down the back of cylinder 3.

That's enough for now, off to bed. More shennanigans tomorrow night...
I forgot to add this detail...

I used dual Lightspeed Plasma III's on my IO-360-A1B6, and I had specified a 22 adv timing ring. After chasing cooling issues for the better part of a year, I decided to return to a 20 adv timing ring ---> CHT's dropped 15+F and Oil came down about 10 with no measurable difference in airspeed.

The recommended timing for this engine is 20, and has been since the mid-1970's. I decided to tweak it a little and go to 22 because the cousin of this engine, the -A3B6D, is set at 25. I figured that all things being equal, a 2 advance couldn't hurt...

I don't know how eMag's set or derive their timing -vs- fixed/magneto/BTDC stamped on the data plate. I seem to recall that most 8.5:1 CR, 2700 RPM Parallel Valve Lyc's are set to 25 BTDC, increase the CR and decrease the advance... 22 for 9:1, 20 for 10:1 and so on...
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RV-7 (Flying)

Last edited by bjdecker : 08-18-2020 at 06:22 AM. Reason: clean up...
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  #128  
Old 08-18-2020, 02:00 PM
jamlip jamlip is offline
 
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Location: Palm Springs, CA
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Hi Brian,

Interesting, I hadn't queried why they were able to run so much advance. So I just called Emag and asked the question. The answer was 'because we have the control to do it'.

I understand that they are experimental systems on an experimental aircraft, so if they work, they work, and if they don't, then its up to you to find a solution.

The Mags are timed to fire at 26 degrees advance, advancing up to 34 degrees with increasing RPM (controlled by vacuum). The mags are timedin reference to the TDC mark, and they didn't recommend going below -6 degrees. Instead they suggested pulling the vacuum pipe to keep the advance static (at 26 degrees), like a traditional mag would be.

I'm going to start with -5 degrees and vacuum advance attached, and then go from there. That'll obviously give a base setting of 20 degrees, and 31 degrees advance. If that doesn't work, I'll plug the vacuum as suggested.

Either way, I wish I hadn't just fitted these and trusted they'd work out of the box - I should have done my own checks. It is an experimental aircraft, regardless.

You live and learn (and sometimes the lesson is expensive).
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Palm Springs CA
1992 O-360 CS RV-6

Last edited by jamlip : 08-18-2020 at 10:35 PM.
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  #129  
Old 08-19-2020, 02:22 AM
penguin penguin is offline
 
Join Date: Jan 2005
Location: England
Posts: 1,132
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James,
Is is not at all uncommon for 6s to run somewhat hot. I guess you have no idea what temps it ran at before you bought it? I've been running P-mags since 2004 and doubt you have purely a timing issue, if you even have a timing issue at all. I would look at the mixture and ensure you are running sufficiently rich. Fuel flow should be in the 16gph range. Difficult to check for sure until you can get to in a medium power cruise and start to lean out looking for a 150F rise in EGT from full rich.
Assuming your baffling is directing all the air through the cylinders you may have to add louvres to increase the cowl exit area to get sufficient air through the cowling. When I added louvres to my O-320 powered 6A CHTs dropped 40F and oil 20 to 30F with ambient temps of 80.
Pete
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  #130  
Old 08-20-2020, 07:03 AM
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bjdecker bjdecker is offline
 
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Location: Georgetown, TX
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Quote:
Originally Posted by jamlip View Post
Hi Brian,

Interesting, I hadn't queried why they were able to run so much advance. So I just called Emag and asked the question. The answer was 'because we have the control to do it'.

I understand that they are experimental systems on an experimental aircraft, so if they work, they work, and if they don't, then its up to you to find a solution.

The Mags are timed to fire at 26 degrees advance, advancing up to 34 degrees with increasing RPM (controlled by vacuum). The mags are timedin reference to the TDC mark, and they didn't recommend going below -6 degrees. Instead they suggested pulling the vacuum pipe to keep the advance static (at 26 degrees), like a traditional mag would be.

I'm going to start with -5 degrees and vacuum advance attached, and then go from there. That'll obviously give a base setting of 20 degrees, and 31 degrees advance. If that doesn't work, I'll plug the vacuum as suggested.

Either way, I wish I hadn't just fitted these and trusted they'd work out of the box - I should have done my own checks. It is an experimental aircraft, regardless.

You live and learn (and sometimes the lesson is expensive).
Except you're 1 degree too far advanced @ 26...it should be 25 per the "book"
(https://www.lycoming.com/sites/defau...2060297-12.pdf)

Is 1 degree going to make a difference? Well, 2 did in my case - so I dunno...

There's also a jumper option to adjust timing curves, Bill Reppucci and others have experience with this.

Good luck!
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