What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Phase 1 engine temperatures

S

stevengrasley

Member
Hello all,

N783RV RV-7A flew for the first time on 10/1/2013 after 18 months of building and 3 months of final prep and getting a DAR It was an exciting day and seems like ages ago already.

Things are going well but did have a high temp (434F) on #1 during climb out with others at 400-ish during that first flight and others since. I've been flying to focus on engine break in for the first 15 hours. Will get to the rest of the real testing after 15 hours. I dont need to be in a big hurry. I've trimmed the air dam and modified my climb out to focus on temps but I wanted to see what others have to say.

I'm in Marathon FL in the Keys so it's basically 90 degrees every day. DA generally around 2,000'. So that presents an immediate challenge for high performance tightly cowled engines. I have an O-360 with the Sensenich FP which I know puts a heck of a load on the engine for climb. Seems the best approach is to lean for DA, use full throttle to jump off the runway climb out at 5-10 degrees pitch up with IAS somewhere 100-120 knots throttling back to about 3/4 while turning crosswind and then working temps with pitch/air speed/mixture during climb to stay around 400-420. In cruise I can get LOP and ROP performance temps of 360-400 depending on lots of parameters. Suffice it to say I'm happy with cruise and cruise climb temps. But initial power climbs require very careful attention to temps. I built it exactly to Vans plans with no mods.

What experience do others with O-360/IO-360 FP set ups have to offer? I did transition training in a 7A with an O-360 and CS prop in hot July in Minneapolis and never really saw 405 degrees. Is the FP the real factor or something else.

Steve
 
You should not be leaning for full throttle take off at DA = 2000'. This is just asking for trouble. Even with a broken in engine. Read the engine operating book, see what DA they recommend leaning at (at full power). Probably 5000' or higher.
For break in of a new engine keep the mixture full rich and the manifold pressure high (don't go above 6000'), and the airspeed as high as needed for cooling (shallow climbs). Since you want high manifold pressures (run 75% power) I would not attempt LOP operations until break in was completed.
 
You didn't mention if you have a Van's cowl or one of the aftermarket cowls with a cooling plenum.

Assuming you have the Van's cowl, have you sealed EVERY potential air leak with high temp RTV? Is your airseal sealing or are there gaps? Are your ariseals curved in towards the engine or did they get blown out to the sides? Are your inter-cylinder baffles tight? Are your cylinder wraps that go under the heads tight?

Who's (I)O-360 do you have? I'm guessing it is a 180 HP parallel valve engine. Do you have ECi tapered cylinders and if so, did you take that into account when you put your baffles on?

Just a few questions and each one of those items need to be addressed to get your CHT's down.
 
What's very common is that the carburetor jet is not rich enough. Virtually everyone I know that has a carb'd RV has had to swap jets or ream their existing jet out. You engine builder can do this.

I had high CHT's at take off until this was done. I also did not have a very noticeable EGT peak at cruise. The engine was just not getting enough fuel.

RVs have efficient induction system and pull a lot more air than most certified installations. This means more air and a leaner mixture. Change the jet, and don't lean at take-off!
 
Mags or Electronic Ignition? If you are advancing the spark (EI), you'll be running hotter - I have found it better to run fixed spark for break-in. Before I would start drilling jets (I know many do, but I know many, many more who don't), I'd concentrate on running full rich for high power settings (as Bob says) - and fly first thing in the morning when the air is cooler, until you get a good break-in.

Usually, with a new engine these days, the break-in and subsequent CHT drops happen pretty fast - the first few hours. If you haven't seen that at 15 hours, how is your oil consumption? If it is high - you might have glazed the jugs at this point.

High power (which means high fuel consumption) and good cooling in the first few hours are what you need. And yes - make sure you have good baffle seals, etc.
 
CHT

I have almost the same setup, and have gone out of Marathon also. No need to climb out at a steep angle, fuel flow at full power/full rich should be 17-18 gph on a carbed 360. Timing no more than 25 degrees! My constant speed should not be a factor as long as you keep the climbs fast and shallow, also nice to see in front in the airport environment. :)
 
GeneL,

Yeah. I've now flown for 12 tach hours and am getting things dialed in. My procedure has settled to full throttle full rich with 5-7 degrees pitch up at about 120 knots during climb out and temps all now stay around 405 but #1 always a little warmer. As soon as I level or cruise climb temps go below 400 and stay there. I trimmed #1 air dam about 3/4" which brought #1 down nicely. I have a full blown SkyView system which is really nice to be sure I keep the power 70-80% for break in. Kind of boring to just rip around at 150 knots but rather be sure the engine is properly broken in. In general things are going well. Just wanted to see what feedback I could get from the crowd. The Lycoming gang told me that 420-435 for short term climb out should not be a big worry. But no higher. I'm sure Mike Busch would disagree. We'll see you around Marathon one of these,days.
 
One more thing Gene...full throttle full rich is showing 18.1 gph on my system. That's right on the button with the Lycoming specs.
 
N941WR said:
Assuming you have the Van's cowl, have you sealed EVERY potential air leak with high temp RTV? Is your airseal sealing or are there gaps? Are your ariseals curved in towards the engine or did they get blown out to the sides? Are your inter-cylinder baffles tight? Are your cylinder wraps that go under the heads tight?

Who's (I)O-360 do you have? I'm guessing it is a 180 HP parallel valve engine. Do you have ECi tapered cylinders and if so, did you take that into account when you put your baffles on?

Just a few questions and each one of those items need to be addressed to get your CHT's down.
Click to expand...

I side with Bill's suspicion. At 12 to 15 hrs it seems your CHT's should be coming down ... certainly to something below 420 to 435. My first inclination would be to check for air leaks somewhere in the baffle/cowl/intake area. From what I've seen/heard, few RV's see those kinds of CHTs after break-in.
 
Hi Steve-
It sounds like you have a carbed 360. What I have found is that the fuel distribution between cylinders can vary greatly depending on whether you are at partial throttle versus WOT. This is apparently common for carbed engines--the fuel distribution just is not often very good. What this means in practice for me is that at partial throttle my #3 and #4 generally tend to run the hottest but at WOT my #1 and #2 run the hottest. I'm starting to learn how to manage temperatures in various phases of flight by shifting between WOT and partial throttle. Given that you may still be in break in you might not be able to manage your temps this way right now, but you should be able to once everything is nicely broken in.
Hope this helps.
 
Next time the cowl is off put a spanner on the intake tube / cylinder clamp flange bolts and check they are tight. Also check the rubber hose clamps on that cylinder. A small air leak will give a substantial CHT rise.
 
Bill,

I have a Van's cowl. I have sealed all gaps and holes with RTV using the dark hangar flashlight method. I have even sealed around the engine and baffle behind the spinner. Baffles seals are good based on marks left on cowl and the seals. In a couple spots I had questions I used a blue marker on the seal to see off tell tale blue is left on the cowl and I believe I have all seals working well. I'll have a close look at the inter baffle and cylinder wraps. I have a new Lycoming purchased through Vans. Thanks for your thoughts and any more you are willing to offer.
 
I'm starting to get a better handle on it

Well, after some more flying and trimming the air dam on #1 by nearly an inch things are performing better. I keep climb out more shallow, speed up, and a little less than full throttle and I can keep things under 400. But I'm nearly convinced the issue is that the mix is lean at full throttle at low altitude, especially on #1.

On the ground with full mixture I can get EGT's to trickle up on #1 and #3 at mid throttle when I would expect they should stay dead low. The only way this happens is with leaning. So, tells me that things are too lean at low altitude. And mixture distribution is not perfect as I can see with the variations in EGT on the ground but it's an O-360 right? So less than perfect distribution is going to be expected. However, in the air at cruise things are much closer and more even.

This weekend I noted that I can do a full power full rich climb from 3000-8000 without a problem. Hmm? I'm looking more carefully at everything and have some data logs from my Dynon system to evaluate. But I'm starting to think that jetting is going to be the solution.

Anybody with thoughts on jetting would be appreciated. Or, any other thoughts for that matter would be appreciated.
 
You must log in or register to reply here.
Back
Top