Geico266
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375 in the yellow line for cylinders, 400 is the red line and too hot.
20 or 25 Degrees BTDC, That Is The Question
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375 in the yellow line for cylinders, 400 is the red line and too hot.
Tom-D
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Or the motor was assembled with the crank / cam gear one tooth off...
If were properly tested after overhaul it would not pass the Test stand requirements, nor would it make the numbers required to return to service on the aircraft.
But that doesn't mean it doesn't happen.
He wasn't comparing of any of the other symptoms of cam timing being off.
Tom-D
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Tell me where to find the info that tells you when each valve is starting to open?
Then tell me how you will move the cam with the accessory case on?
specially in an hour.
Tom-D
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yes it does.
Either this board or the red board you'll find a thread I diagnosed the dude had a tooth off on the cam, and so it was. Anything can happen regardless what a book says was supposed to happen.
Tom-D
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any aircraft engine with the cam off by 1 tooth will not make the numbers /power that it is required to. this can be noticed by the most ignorant pilot flying.
This is not the case with the OP's engine it has been flying.
Geico266
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This is too funny. What is it about regarding the timing 2.5 degrees that gets everyone's patties in a wad? This is why I love experimentals and I can do what I want without having to answer to anyone but myself. Even Lycoming issued an AD to retard the timing in certified planes 5 degrees due to excess heat.
I pick up 25 MPH in cruise, cooled the cylinders by 40 degrees, and was able to add 4-5" of manifold pressure. What's not to love?
I pick up 25 MPH in cruise, cooled the cylinders by 40 degrees, and was able to add 4-5" of manifold pressure. What's not to love?
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Correct, nor was it my assumption. To say that one doesn't get bolted onto a plane and delivered to an owner is incorrect.
Silvaire
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Um, not according to Lycoming but you're experimental so do whatever you want.
Silvaire
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First off Lycoming doesn't issue AD's but regardless, what AD would you be talking about? Because it's news to me.
Hmmmmm... Clearly you have NEVER degreed a cam in..
You do realize the crank needs to move at the same time to determine exact TDC... And the crank needs a degree wheel bolted to it for timing reference...
kgruber
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You are just making that up.
You are just making that up.
Not on the same fuel flow. That is what counts. So, you are making that up too.
RotorAndWing
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Geico266
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Not making any of it up. All facts as presented by Mike Busch. Maybe you should attend his seminars, read his books, and watch his webinars. I'll take his advice any day over yours.
http://www.eaavideo.org/video.aspx?v=2274677932001
If you want to run your cylinders at 425F knock yourself out, but get your check book out.
Whether you decide to operate the engine lean or rich of peak, maintaining cylinder head temperatures is key. “Historically, cylinders which continuously operate at higher CHTs, say, 400 degrees Fahrenheit and above, for long periods, will tend to need mechanical attention before cylinders that run in the 360s or 380s,” Townsend said.
http://www.flyingmag.com/aircraft/pistons/piston-engines-keeping-your-cylinders-happy?page=0,1
Made up the fact that there was a Lycoming AD to retard timing to cool engines? Here is the FAA Regs...
http://rgl.faa.gov/Regulatory_and_G...5683e5b86257a09004d8f38/$FILE/1E10 Rev 24.pdf
* All models except IO-360-A1B6D and -A3B6D have optional timing of 20°BTC
Of course it is not the same fuel flow that is why I was not running the same manifold pressure. I could not run the same MP without having the CHTs go to 400F. Changing the timing 5 degrees now allows me to increase MP (fuel flow) & speed while running cooler CHT's.
How am I making up anything? Maybe you should check your facts about how to run an aircraft engine.
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What pistons are in the engine, and what fuel are you running?
Geico266
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9 to 1 pistons, 92 Octane car gas. I had the same temps with 100LL.
Something is not right.
Geico266
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I changed the timing 5 degrees, how is that so difficult to accept?
Modern engine has timing advance up to 37 degrees at altitude. Racing engines are set at 30 degrees, but only get one year out of them at Reno.
I am amazed that so many are so negative. Its pretty simply. If you are having high CHT's (and the baffling is adequate) move the burn event farther away from TDC. Pretty simple.
Why not experiment?
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Tom-D
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Hmmmmm... Clearly you have NEVER degreed a cam in..
You do realize the crank needs to move at the same time to determine exact TDC... And the crank needs a degree wheel bolted to it for timing reference...
Real aircraft certified engines already have the degrees marked on the crank or fly wheel. Plus the fact the both major manufacturers have the cam and crank gears covered by a accessory case, which must be removed prior to removing the cam/crank gear assembly.
So you place the degree wheel on the crank. then what? How are you going to tell if the valve opening is in time with the TDC of the engine?
Tom-D
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And the crank needs a degree wheel bolted to it for timing reference...
Tell us why you would need a degree wheel to tell when the piston is at TDC when all you need to do is find compression stroke, and bring it up to the TDC mark on the crank/flywheel.
Tom-D
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When you move the timing to the advanced position more than design, the fuel burn is held in the combustion chamber longer and will transmit more heat into the cylinder head. If you retard the timing the fuel burn rate will still be heating the fuel air mass as the exhaust valve opens. either way you are destroying the engine. That's why I don't experiment.I changed the timing 5 degrees, how is that so difficult to accept?
Modern engine has timing advance up to 37 degrees at altitude. Racing engines are set at 30 degrees, but only get one year out of them at Reno.
I am amazed that so many are so negative. Its pretty simply. If you are having high CHT's (and the baffling is adequate) move the burn event farther away from TDC. Pretty simple.
Why not experiment?
Geico266
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Directly from the Federal Regs.
http://rgl.faa.gov/Regulatory_and_G...5683e5b86257a09004d8f38/$FILE/1E10 Rev 24.pdf
* All models except IO-360-A1B6D and -A3B6D have optional timing of 20°BTC
20 degree timing is an acceptable option for cooling some Lycoming engine CHT's.
EGT's are not nearly as critical as CHT's.
http://www.eaavideo.org/video.aspx?v=1316946190001
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kgruber
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Tom-D
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That doesn't alter anything I've said, choose your failure head cracks or burned valves.
Silvaire
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Silvaire
As pointed out that's not an AD. Also should be pointed out that the asterisk after the 25 denotes all models except the two listed in that column There is another column to the right of that and several other sections of other models to which the note does not apply. I believe the applicable engines are the 200 hp angle valved models.
Once again, you're experimental and can do what you want and I don't think that you'll listen to anything that doesn't come from Savvy anyway but it seems to me you are addressing this perceived "problem" by permanently derating your engine. Couldn't you do that by simply running at reduced power? That way you'd still have the full rated power for emergency or high demand circumstances.
I changed the timing 5 degrees, how is that so difficult to accept?
Modern engine has timing advance up to 37 degrees at altitude. Racing engines are set at 30 degrees, but only get one year out of them at Reno.
I am amazed that so many are so negative. Its pretty simply. If you are having high CHT's (and the baffling is adequate) move the burn event farther away from TDC. Pretty simple.
Why not experiment?
Because you should not have been having that much issue. Without you being in a destructive regime of operations, that change in timing should have caused a 15° reduction or so in CHT at the same new, higher power setting.
mtuomi
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If the engine is healthy, 2,5deg retard at 2700rpm will increase EGTs by about 15f. You have some other problem.
Hmmm... Maybe a dial indicator on a push rod to tell valve opening in relation to crank degrees..
...On second thought..... Never mind, as you have NO CLUE on cam inspection. timing and checking lift....
unsafervguy
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i suggest that you you read the TC for your motor. 500 is the redline. the other numbers are made up by mike bush. I try to keep mine below 400 but the redline is 500.
as i said before, find the reason that you are running hot, not just turn down timing and throw away HP.
bob burns
Geico266
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Dan Thomas
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What is a TC? Type Certificate? No such animal on experimental engines.
Yeah, but your "experimental" engine is just a decertified type-certified engine, made of all the same parts which are made of the same stuff it was made of before it was decertified. If Lycoming says 500°F is the CHT limit, then that limit applies to your engine, too. Calling it experimental doesn't change the metallurgy nor any physical limits of the engine. Sure, guys take certified engines and use them in homebuilts and run them at higher RPMs to get more HP, but at the cost of engine life and reliability. You have some serious compression in that engine that might be causing detonation and CHT issues that were rectified by retarding the timing. Using Mogas, especially, is questionable with that compression level.
The TCDS for your engine is on the FAA website. Lots of good info there.
Lycoming recommendation for cruise is to keep them below 400°, preferably 370°. The problem with over 400° is you may have hot spots that reach above 420°, and that is where you start damaging oil. You could potentially damage the oil enough in 20 hrs to lose lubricity, now you're spinning a bearing. Most spun bearing "engine blew up" events are preceded by an overheating event.
475-500 and you are looking at structural integrity of the head, not to mention detonation, issues.
unsafervguy
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the fact is if you could not run more than 18'straight and level at 25 degrees you have a cooling issue not a timing issue. your baffling may be tight but something is not right. the inlet ramps are important in that cowl. also the inter-cylinder baffles need to be right and sealed. increasing fuel flow and decreasing timing are bandaids that throw away HP or fuel, not solutions. there are thousands of planes flying with that setup running 25 degrees and running cool. find the real problem not just mask it. I went through it with mine and found the solution to my cooling problems.
bob burns
bob burns
kgruber
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RV-8.........OH!!! "High performance." Hang on to your hat!
Just do zoom climbs.............all will be good.
Just do zoom climbs.............all will be good.
Silvaire
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What is a TC? Type Certificate? No such animal on experimental engines.
You're the one who quoted it and posted the link. Out of curiosity what model do you have?