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Old 08-26-2021, 05:29 PM
jettshawn jettshawn is offline
Join Date: Aug 2021
Location: Morgan
Posts: 2
Default Gettin Hot

Hello all, i recently bought an Rv-9a with 300 hours on it. Super excited but need help, and maybe you can point me to the correct thread. This plane runs hot on take off and climb. After 15 seconds from take off with a climb rate of 5-800 fpm at 5000' elevation, i go right to 420 degrees fast, if i shallow the climb to 2-300 fpm and pull power i can get it to stay under 425. My setting is almost full rich on take off but at 5000 feet field elevation, it doesnt run great full rich. It is carbureted and only producing 10 gph on take off mostly full rich. it has the Titan 0-340 in it. I understand that this engine can operate at 425 on take off and cruise, i have the same engine in my carbon cub, it just goes to that temp almost instantly. I flew it yesterday and the temp was 58 degrees outside on take off and it still went high quick. Note, this is only on 2 of the 4 cylinders. Any ideas on how to cool this beast down on take off? Maybe not enough fuel, maybe a different cowling ect.. Thanks in advance
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Old 08-26-2021, 05:51 PM
Steve Melton's Avatar
Steve Melton Steve Melton is offline
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 3,532

it's too hot but you know that. it usually take me 10 minutes to get to 350F on a hot day at 700 ft MSL, the take off elevation you have will make it hotter. if I remember correctly I am 13 or 14 GPH at full rich. the first thing I would do is check the timing. advanced timing will cause CHT to be high. if it's not the timing then verify you have the correct carb settings with continental. if it's only two of the four cylinders, verify the inlet air dams in front of the cylinders are at the proper heights and make sure your baffle seal are tight.

at 5000 ft elevation you should be leaning for take off.
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 900+ for all

Simplicity is the art in design.
I was born an airplane nut. I have no explanation for it.
My Artwork is freely given and published and cannot be patented.

Last edited by Steve Melton : 08-26-2021 at 05:57 PM.
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Old 08-26-2021, 06:12 PM
hoyden hoyden is offline
Join Date: Jul 2011
Location: Minneapolis, MN
Posts: 50

I had a similar issue with my IO-360 RV-6. Taking off my CHT would be going through 400F by pattern altitude. I immediately would then adjust for LOP so it wasn't a big issue. FF WOT was 15.9 GPH. I sent the FI to AFP for overhaul and had them boost the fuel flow to 18 GPH. Problem went away and now I can climb WOT till the cows come home. I would suspect a 160 HP 320 would need about 16 GPH.
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Old 08-26-2021, 06:56 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,863

Check ignition timing, yes, but it sure looks like it needs a richer micture. And fix baffle leaks, air dams, etc to even out the CHTs.
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Old 08-26-2021, 07:19 PM
YellowJacket RV9 YellowJacket RV9 is offline
Join Date: Oct 2012
Location: Clearwater, FL KCLW
Posts: 1,330

I have found that at WOT, the mixture distribution is poor, and two cylinders end up much leaner, and thus hotter, than the other two. I am able to even them out a bit by slightly cracking the throttle back from WOT. I also drilled the jet on my O-320 (150hp) carb out a couple steps, and now get around 12GPM on takeoff. I frequently fly on 90 degree days at sea level, and I can find myself pushing over 400* if I keep up a steep climb for a few thousand feet, but I very rarely do that. I can throttle back a bit or lower the climb angle and keep temps under 400.

Before doing anything drastic though make sure your baffles are *really* well sealed - there are a number of good threads on here about that topic.

Chris Johnson
RV-9A - Done(ish) 4/5/16! Flying 4/7/16
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Old 08-26-2021, 07:21 PM
Kyle Boatright Kyle Boatright is online now
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,679

Which two cylinders get warm? How warm/cold are the other two? Does your airplane have air dams installed in front of #1 or #2?

My opinion is that the first thing you should do is check your baffling. Make sure the baffle seals seal all the way around (they should be bent towards the middle of the engine to make a seal against the cowl). You should see light witness marks (sections of your seals that appear polished) that indicate a good seal. Make sure all minor gaps (even tiny ones) are blocked. Turn the lights off in your hangar and get a friend to shine a flashlight up through and around your baffles while you're watching from the other side. If you see any gaps, fill them with RTV.

Presumably you have the inlet ramps on the top cowl? Do your baffles seal properly to keep air from escaping around or through the ramps? The baffle material flaps that seal between the cowl inlets and the baffles... got those? How tight are your baffles against your cylinders? Are there gaps where the baffles stretch 1/8" or 1/4" away from the cylinders? All of those things matter.

The bottom line is you want to get every bit of cooling out of the air that's flowing into your cowling. If you don't, you'll have a warm engine.
Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
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Old 08-26-2021, 08:06 PM
BillSchlatterer BillSchlatterer is offline
Join Date: Jan 2005
Location: Arkansas
Posts: 601
Default Questions

Couple things:

First, A models always heat up funny because of all the nose gear weldments affecting the exiting of cooling air. Most A models...Most, not all, will cool a lot better if you climb at 130 to 140 MPH.

Second, you don't say if you have P-mags or not. If you do, be sure the jumper is set and then retard the timing 4-5 degrees on both mags. That will make a large difference and you will see little difference in effective power.

Third .... You don't say but I assume this is a fixed pitch prop. If it's constant, pull the RPM back to 2400 just off the ground.

Hope any of that helped!
Bill S
Got the Grin :-)
7a Ark KORK
Dues Paid 5/26/21
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Old 08-27-2021, 09:39 AM
jettshawn jettshawn is offline
Join Date: Aug 2021
Location: Morgan
Posts: 2
Default Thank you

Great information, i do have a fixed prop. It is going into the annual this weekend and i will check all of this. Thanks a ton
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Old 08-27-2021, 11:14 AM
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DanH DanH is offline
Join Date: Oct 2005
Location: 08A
Posts: 10,360

Some of the quoted fuel flows are excessive. As a reasonable rule of thumb, minimum fuel flow for full rated power can be found by determining chart HP for the MP and RPM, then dividing by 12 for GPH at a BSFC of 0.5 lbs per HP per hour. Dividing by 10.75 will be a bit over 0.55 BSFC. Much more is just a dirty way to reduce power.

Here the OP is at 5000 feet field elevation (low MP), swinging a fixed pitch (not 2700 RPM), so HP is quite a lot less than rated max, and required fuel flow will also be less.

Titans have taper fin cylinders. More than a few got cylindrical baffle wraps. Although not optimum, cylindrical wraps can be used if the builder installs tapered closure plates at four points noted below. Failure to do so creates a huge pressure leak.
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Dan Horton
Barrett IO-390
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Old 08-27-2021, 01:21 PM
lr172 lr172 is offline
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 6,732

Originally Posted by BillSchlatterer View Post
Couple things:

First, A models always heat up funny because of all the nose gear weldments affecting the exiting of cooling air. Most A models...Most, not all, will cool a lot better if you climb at 130 to 140 MPH.
I have a 6A with a 160 HP 320. On the hottest of days, I never go above 380 until I am above 6 or 7000' and that is due to the thinner air and my ignition advance ratcheting up with the lower MAPs. I lean to best power once at pattern altitude and still don't get above 380* down low. I climb at 100 MPH to pattern altitude, then 130 or so after that.

I don't think it is correct to say ALL A models have issues with cooling.

N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 08-27-2021 at 01:25 PM.
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