Yellow P-38 build thread
09-28-2015, 04:50 PM
#377
Finished up the throttle/choke linkages and tested the engines.
Using a 3 blade 18X10, getting 6600 rpms.
The right engine starts up easily, the left one requires a starter.
Cleaned out the carb screen, L/H needles cleaned and reset to 1.5 each but still hard to start. That side got the most damage on the belly landing.
Using a 3 blade 18X10, getting 6600 rpms.
The right engine starts up easily, the left one requires a starter.
Cleaned out the carb screen, L/H needles cleaned and reset to 1.5 each but still hard to start. That side got the most damage on the belly landing.
04-18-2016, 10:43 AM
#382
PM (cont)
Jeff: had to rebuild both carbs but I still need a starter to get them going. Opening the low end for more fuel reduces my high RPM's (I hate having to start gas engines with a starter!). The 2 new zenoah's on my old C-45 twin beech started manually. Maybe some new rings would fix the hard starts!
Getting around 6700 RPM's on both engines using Metzlik 3-blade 16X11's.
Jeff: had to rebuild both carbs but I still need a starter to get them going. Opening the low end for more fuel reduces my high RPM's (I hate having to start gas engines with a starter!). The 2 new zenoah's on my old C-45 twin beech started manually. Maybe some new rings would fix the hard starts!
Getting around 6700 RPM's on both engines using Metzlik 3-blade 16X11's.
04-18-2016, 10:57 AM
#383
My Feedback: (43)
You should be able to lean the high end a smidge to regain most of the lost rpm due to being rich. As you may know, the butterfly in a walbro uncovers three jets in the venturi. Well not uncover but exposes them to high velocity air as the butterfly open. At WOT, all three jets are spewing fuel. So richening the idle needle will indeed introduce more fuel to the WOT mixture, BUT, leaning the high end should help that. You have to find that happy medium. If the G-38 are new, they will get easier to start as they break in too. Are you starting your hand flip with all three magnets before the Mag pickup? All three have to pass at a good rpm to fire a hot spark. I have to start my flip well before TDC to get all three to pass at max RPM. It feels weird to start the flip before compression, but it works on my 62, 45 and 26. It has been quite some time since I have started a 38, so this magnet arrangement may not apply???
From the Zenoah Manual, but they do not single out the 38, so I would assume it applies?
I always set my mag gap to that of a business card, too little of course will hit, too much equals weaker spark.
I am like you about starting any of my engines by hand. I only use a starter as the last resort!!
LIke I said, you probably know this with your other Zenoahs, but if you didn't it may help.
From the Zenoah Manual, but they do not single out the 38, so I would assume it applies?
I always set my mag gap to that of a business card, too little of course will hit, too much equals weaker spark.
I am like you about starting any of my engines by hand. I only use a starter as the last resort!!
LIke I said, you probably know this with your other Zenoahs, but if you didn't it may help.
04-18-2016, 11:09 AM
#384
My Feedback: (43)
I have also found that different engines like to be choked differently. My 62 is easy to flood and kicks when you get get it too wet. My G26 will not start by hand if over choked only a little bit. My 45 like to be very wet to start.
PS, if none of the stuff above work, then I am all out of ideas.
PS, if none of the stuff above work, then I am all out of ideas.
04-18-2016, 12:53 PM
#386
Sam,
Have you checked the Phenolic or plastic carb stand offs for possible cracks. From either over tightening them or from the crash.
It sounds as if there is excess air being drawn in from some where.
When i was flying the Yellow P-38's with G38's i always ran them on 18X10 three blades. The zenoah engines really like to have some load put on them to make them work better.
They really are not meant to be run at such high RPM's. They perform much better with more of a load on them to use there low end torque.
Have you checked the Phenolic or plastic carb stand offs for possible cracks. From either over tightening them or from the crash.
It sounds as if there is excess air being drawn in from some where.
When i was flying the Yellow P-38's with G38's i always ran them on 18X10 three blades. The zenoah engines really like to have some load put on them to make them work better.
They really are not meant to be run at such high RPM's. They perform much better with more of a load on them to use there low end torque.
Last edited by Greg Wright; 04-18-2016 at 01:16 PM.
04-18-2016, 02:27 PM
#387
Greg,
I checked the carb stand offs when I had the carbs off and they looked OK. They are white as I put the thinner ones on made by B&B. The two bolts needed an extra 1/2 turn or so.
I had the 3 blade 18X10 on the P-38, last season, and she was a dog in the air.
The C-45 with 2 blade 18X10's were ideal for it but the twin beech just flew around the usual flat pattern.
I usually like RPM's to be around 6500-6800 on my gas engines as that seems to give me the best performance. My Z P-61 (G-62's), F6F (GT-80) and SBD (GT-80) all run around 6500.
Sam
I checked the carb stand offs when I had the carbs off and they looked OK. They are white as I put the thinner ones on made by B&B. The two bolts needed an extra 1/2 turn or so.
I had the 3 blade 18X10 on the P-38, last season, and she was a dog in the air.
The C-45 with 2 blade 18X10's were ideal for it but the twin beech just flew around the usual flat pattern.
I usually like RPM's to be around 6500-6800 on my gas engines as that seems to give me the best performance. My Z P-61 (G-62's), F6F (GT-80) and SBD (GT-80) all run around 6500.
Sam
Last edited by samparfitt; 04-18-2016 at 02:31 PM.
04-19-2016, 07:32 AM
#391
My Feedback: (81)
Personally, I say never tach a twin. Just run each engine until they sound good and have good transition, and you are set to go; I find prop selection to be of the common choices, but I prefer 3 blades on twins to load the motors a bit, and not get a screaming RPM. I have only lost an (one) engine, one time, on one A/C, using this method. I have never put a tach to the Ki-45, and you know how good that one runs.
JQ
JQ
04-19-2016, 10:42 AM
#392
Greg,
Once I get everything fixed on the P-38, I'll have to try those needle settings as mine are usually around 1.5/1.5.
=====
Jeff,
You've got better ears then me as I need a tach to make sure I'm around 6500 RPM's.
=====
PM (cont)
Engines:
I checked to insure the chokes were fully closed.
The right engine started manually giving me 6700 rpm's.
The left engine's choke was not fully closed due to slop in the linkage. I found one screw missing and the other loose on the servo tray.
The left engine was also missing one exhaust pipe. Some 1/2" diameter water pipe and JB weld fixed that.
My kill switch in the bottom vent also came loose.
I also added my AMA and FAA info to the inside of the ignition door.
Sam
Once I get everything fixed on the P-38, I'll have to try those needle settings as mine are usually around 1.5/1.5.
=====
Jeff,
You've got better ears then me as I need a tach to make sure I'm around 6500 RPM's.
=====
PM (cont)
Engines:
I checked to insure the chokes were fully closed.
The right engine started manually giving me 6700 rpm's.
The left engine's choke was not fully closed due to slop in the linkage. I found one screw missing and the other loose on the servo tray.
The left engine was also missing one exhaust pipe. Some 1/2" diameter water pipe and JB weld fixed that.
My kill switch in the bottom vent also came loose.
I also added my AMA and FAA info to the inside of the ignition door.
Sam
05-20-2016, 09:44 AM
#396
My Feedback: (4)
Join Date: Feb 2003
Location: Roseville, CA
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Hi Guys,
Building a YA P-38 with twin DA-50R engines, one is counter-rotating. Anyone know where I can pick up a 20X10 or 22X8 3-blade, scale looking prop set for this beast? I tried Aircraft International, Solo, 3W, Biela, no luck. Needs to be a matched set, running a twinsynch. Just got the first coat of primer on it. Builder is Scott Raines in Hawthorne...
Thanks!
Building a YA P-38 with twin DA-50R engines, one is counter-rotating. Anyone know where I can pick up a 20X10 or 22X8 3-blade, scale looking prop set for this beast? I tried Aircraft International, Solo, 3W, Biela, no luck. Needs to be a matched set, running a twinsynch. Just got the first coat of primer on it. Builder is Scott Raines in Hawthorne...
Thanks!
05-20-2016, 05:28 PM
#399
My Feedback: (4)
Pull-up,
Building the same bird, same engines. I was able to get Biela 20x10 tractor and pusher props from Aircraft International. They still have them listed on their website. Did they stop selling them? Guess I need this info too. Don't want to break one and not have a replacement. I have 2, 2 blade 22-10 Biela CF props, used for breaking in counter rotating engine if you want one.
What mufflers are you going to use?
Keith
Building the same bird, same engines. I was able to get Biela 20x10 tractor and pusher props from Aircraft International. They still have them listed on their website. Did they stop selling them? Guess I need this info too. Don't want to break one and not have a replacement. I have 2, 2 blade 22-10 Biela CF props, used for breaking in counter rotating engine if you want one.
What mufflers are you going to use?
Keith
05-20-2016, 09:20 PM
#400
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Join Date: Feb 2003
Location: Roseville, CA
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RVN,
I was looking for something more scale. The Bielas on the AI site have thick bases and are probably great props but look silly on a 38. If Biela had a semi-scale pusher in 20X10 or 22X8 I would be happy, but Gerhard told me not enough demand to justify the mold cost. Guess I will use the Xoars and paint them. Best solution I have found thanks to samparfitt. Mufflers I am using can be found here:
http://www.bennettbuilt.com/shop/Muf...5_Muffler.html
Cheers!
I was looking for something more scale. The Bielas on the AI site have thick bases and are probably great props but look silly on a 38. If Biela had a semi-scale pusher in 20X10 or 22X8 I would be happy, but Gerhard told me not enough demand to justify the mold cost. Guess I will use the Xoars and paint them. Best solution I have found thanks to samparfitt. Mufflers I am using can be found here:
http://www.bennettbuilt.com/shop/Muf...5_Muffler.html
Cheers!
