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High Temperature during take off in RV-7

givo

Member
I guess this issue has been already discussed many time in this forum . Nevertheless I?m relatively young in experimental field and in RVs so I post the following question , hoping someone is so nice to give me some suggestion .
I have problems of temperature in my RV-7 180 CV . I have two CHT , one on the most cooled , one on the least cooled cylinder .
I have also a small door on the lower cowling ( I miss the English term , in Italian is ? flabello ? ) that can be open with a servo .
With this door open , during take off also in winter with externa temperature of 30 ? 50 F? , the temperature of the less favorable cylinder goes from 350-400 ?F to 450 ?F . The other more cooled cylinder will stay around 400 ?F .
After take off I usually level the aircraft quite soon reducing power as soon as feasible and until both temperature return to 350 F? but it take quite a while .
Than I resume normal level flight at 75% power .
From now on temperature are relatively stable around 350 ?F but if I start to climb also starting from an altitude as 3000 ft the temperature of the less favorable cylinder goes to 400 ? F .
Question : there is a way to improve ventilation inside the cowling ? Shall I install second door on the lower cowling ? or may be shall I enlarge the bottom opening ? regarding the baffle they seems to sit quite tight with the cowling ? tank you for suggestions ? Giulio
 
? flabello ? = Flap or "Cowl Flap" if on the engine cowl to help cool the engine.

"flabello" = "Flap" o "Cowl Flap" Se sul cofano motore per aiutare a raffreddare il motore.
 
My engine is a LYCOMING O-360-A1A with two magnet Marvel-Schebler Type MA-4 ? 5 , standard timed I think ?
 
pefetto grazie , sei italiano ?

Sì, io sono del patrimonio italiano. I miei nonni dal lato del mio padre (Reppucci e DePresszió) sono stati da San Potito Ultra, Provincia di Avellino. Anche se sono nata e cresciuta negli Stati Uniti.

Dove in Italia vivi? (Non importa, ti vedo zona da Padova.)

(Ho anche cheat e uso MSWord per aiutare con la mia traduzione come il mio italiano è come un due anni).

Ciao
 
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My engine is a LYCOMING O-360-A1A with two magnet Marvel-Schebler Type MA-4 – 5 , standard timed I think …

È il carburatore. Io sono curioso di sapere quali accensione avete e sono essi a tempo correttamente?

(In English: That is the Carburetor. I am curious about what ignition you have and are they timed correctly?)
 
Mine was similar until I installed the gear fairings but I also had to retard the timing of my P-Mag a couple degrees to help until the gear fairings were installed.

If fairings are installed, check baffling for leaks and confirm timing is correct for the mags and/or electronic ignition.

It is fine to have 400-425 in climb but should stay below 400 (380, ideally) in cruise. Mine cylinders run 360-390 in summer temp cruise, depending on mixture setting.
 
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Are you sure that the "eyebrows" are installed in the upper cowling over the inlets? If these are missing, it will cause overheating at high AOA.
 
S?, io sono del patrimonio italiano. I miei nonni dal lato del mio padre (Reppucci e DePresszi?) sono stati da San Potito Ultra, Provincia di Avellino. Anche se sono nata e cresciuta negli Stati Uniti.

Dove in Italia vivi? (Non importa, ti vedo zona da Padova.)

(Ho anche cheat e uso MSWord per aiutare con la mia traduzione come il mio italiano ? come un due anni).

Ciao

molto bene grazie delle info , io ogni tanto vengo in US per lavoro ( pharma ) ciao Giulio
 
? il carburatore. Io sono curioso di sapere quali accensione avete e sono essi a tempo correttamente?

(In English: That is the Carburetor. I am curious about what ignition you have and are they timed correctly?)

Sorry the ignition is Unison Industries Slick Magneto , the engine has 50 hours so I suppose they are correctly timed
 
Are you sure that the "eyebrows" are installed in the upper cowling over the inlets? If these are missing, it will cause overheating at high AOA.

This is new to me ?I ?m not sure to know what "eyebrows" are ? is some device that is not standard in the kit ? some kind of conveyors that you install inside in inlets of upper cowling
 
This is new to me ?I ?m not sure to know what "eyebrows" are ? is some device that is not standard in the kit ? some kind of conveyors that you install inside in inlets of upper cowling

It IS standard in the kit. It consists of fiberglass pieces glassed in to smooth the inlet airflow above the air inlets.
 
Hi Ray , I have the gear fairings installed , I wonder how they can influence engine cooling ?.anyway I have standard Slick Magneto , I will check baffling for leaks , thanks for the info about temperature Giulio
 
Mel accennato i pezzi in fibra di vetro che vanno all'interno della mucca superiore che le transizioni (liscia) il flusso d'aria dall'ingresso al camino.

Ci sono anche i deflettori di alluminio che ottenere rivettati per i deflettori e alzarsi davanti a cilindri #1 e #2. Lo scopo di questi ? quello di spingere verso l'alto l'aria sopra i due cilindri anteriori e costringendolo alla parte posteriore due.

Che vi aiuter? a bilanciare tutte le temperature del cilindro.

Vorrei anche avere il tuo tempismo magneto controllato, solo per essere positivo che ? corretto per il tuo motore. Se ? avanzato, dire 28 gradi anzich? 25 gradi, si vedr? di CHT alta durante le impostazioni ad alta potenza.

In English:
Mel mentioned the fiberglass pieces that go on the inside of the top cow that transitions (smooths) the airflow from the inlet to the cowl.

There are also aluminum deflectors that get riveted to the baffles and stand up in front of cylinders #1 and #2. The purpose of these is to push the air up over the front two cylinders and forcing it to the back two.

That will help balance all the cylinder temperatures.

I would also have your magneto timing checked, just to be positive it is correct for your engine. If it is advanced, say 28 degrees rather than 25 degrees, you will see high CHT?s during high power settings.
 
PICTURES!

Givo:

Pictures of the inlet area please. We can see if the eyebrows are installed.

Thanks!
 
Local contact

I have a customer in Balzano who might be able to help you. Elmar Marinoni lives there, and flies a Rocket. You could ask him to have a look?

Strikler & Marinoni OHG - I do not have a telephone number. Sorry!

Good luck!
 
Quite a few of us have been there.

Rejet the carb to flow more fuel on take off.

You will be amazed how much this helps.
 
cooling

1876112485988869


I would not retard power on your climbout unless you are continuously hitting 400+ on climbout, reducing power to get the CHTs back to 350 before resuming the climb is simply not necessary in my opinion.
For better CHT cooling you can also instal "louvers" in the bottom of the cowling next to your door. Louvers can reduce CHTs a lot!
 
Good baffles

Hi,
I have a RV-7 in East of France, similar weather as where you are...
My engine is a Aeropsport Power IO-375, with fuel injection and dual P-Mags (electronic ignition). My setup probably helps with lower CHT compared with carburator and "traditional" ignition...
During the first few hours after initial flight in summer I was seing hig CHT as well, but my engine was not broken in and the weather was quite hot (above 30°C). To mitigate the hight temps I was climbing at 120 Kts indicated for better airflow over the cylinders.
Now I have about 50Hrs on the plane and the engine break-in is done, and I'm able to keep CHT below 380 most of the time.
I believe the most important is to have PERFECT baffles.
That will help create a high pressure area in the top part of the engine compartment forcing air around the cylinders for cooling.
If you do not have good baffles this will make leaks over the baffles or on the side of the cowling likely and this will reduce the high pressure on top of the engine and reducing the flow of air around the cylinders.
When I built my baffles I took very good care of blocking every little hole, and making tight rubber seals. As others have said the inlet ramps are also important to allow a smooth airflow to enter the engine compartment.
Increasing the exit area will not help cooling the engine if the baffles are not good, it will only increase drag (your cowl flap will get in the airflow, so more drag).
In summary I believe the key is the pressure diferential between the top and bottom of the cylinders. The higher the differetial the higher the flow of air around the cylinders and thus better cooling.
Good luck...

EDIT: link to a good article on baffles: https://blog.aopa.org/aopa/2017/03/29/its-baffling/

Alain.
 
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Hi,
I have a RV-7 in East of France, similar weather as where you are...
My engine is a Aeropsport Power IO-375, with fuel injection and dual P-Mags (electronic ignition). My setup probably helps with lower CHT compared with carburator and "traditional" ignition...
During the first few hours after initial flight in summer I was seing hig CHT as well, but my engine was not broken in and the weather was quite hot (above 30?C). To mitigate the hight temps I was climbing at 120 Kts indicated for better airflow over the cylinders.
Now I have about 50Hrs on the plane and the engine break-in is done, and I'm able to keep CHT below 380 most of the time.
I believe the most important is to have PERFECT baffles.
That will help create a high pressure area in the top part of the engine compartment forcing air around the cylinders for cooling.
If you do not have good baffles this will make leaks over the baffles or on the side of the cowling likely and this will reduce the high pressure on top of the engine and reducing the flow of air around the cylinders.
When I built my baffles I took very good care of blocking every little hole, and making tight rubber seals. As others have said the inlet ramps are also important to allow a smooth airflow to enter the engine compartment.
Increasing the exit area will not help cooling the engine if the baffles are not good, it will only increase drag (your cowl flap will get in the airflow, so more drag).
In summary I believe the key is the pressure diferential between the top and bottom of the cylinders. The higher the differetial the higher the flow of air around the cylinders and thus better cooling.
Good luck...

EDIT: link to a good article on baffles: https://blog.aopa.org/aopa/2017/03/29/its-baffling/

Alain.

Hi Alain , very interesting, also the link very useful , thank you
 
I have a customer in Balzano who might be able to help you. Elmar Marinoni lives there, and flies a Rocket. You could ask him to have a look?

Strikler & Marinoni OHG - I do not have a telephone number. Sorry!

Good luck!

Hi Mark ,

thanks , I know Elmar quite well , in fact we flew together with my plane to check temps ... A question .... I', m still breaking in , does this contribute to higher temps ? Thanks Giulio
 
Dear all a short update on the temperature . After the 50 hours check of the engine and break-in done , we minutely checked the baffle in order to close also the minimum hole where you can waste air .

The result was surprising .

The CHT temperature during take off are hardly over 370 F? and the difference between cylinder 1 and 4 is minimum ( before was substantial ) .

Thanks also to the good article on baffles: https://blog.aopa.org/aopa/2017/03/29/its-baffling/

we reached the determination of working on the minimum details of the baffling installation .

I also change the prop from wooden prop to a Hartzell two blade prop that has the blade shank more thin , I don?t know if it counts ?? anyway thanks to you all you really helped a lot
 
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