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Brison 5.8 best performance

Old 09-01-2007, 11:02 AM
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Thunder8A36
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Default Brison 5.8 best performance

Hi guys:

I´m needing some help with this one. I´m test benching this engine before install it on my Aerotech P-47 wich has already a Brison 4.2.

The decision to change engine was due the problem I´m having flying the airplane here in a real tropical weather, a lot of humidity and hig temps. When I compare my fligths from here and Florida, there is a huge difference, so after a lot of tunning testings and propeller changes the best is have some power to spare due the conclusion is the loss of power and performance from USA to here.

So, my 4.2 works fine with a Zinger 22x10 and better with a 3W 22x10 those props runs static around 6400. For some scale manouvers like victory roll,military roll, chandelle etc I need to keep speed, so here is when 4.2 tends to overheat at WOT, if I rich you can feel the lower rpm at WOT and also lower speed and weak manouvers.

After break in the 5.8 I installed the 22x10 just to have a reference and start to write down all information before to swap engines. I get 6800rpm at WOT, later I change to a 22x12 and get the same 6800, later I change to a 24x10 and same reading.

I could go further with test due a particular problem came out and this I believe is due the vibration problems, the throtle body butterfly get loose and scuff to the carburator body sides so it sticks when you idle. I change carb and took the one from 4.2 wich is the same and star over again the test and same damit problem happened so I had to stop and fix carbs wich I did already and post this article before going further.

I´m not very expertise with big gas engines for airplanes besides I work with outboard race engines, maybe I´m thinking wrong and I´m asking too much for this one, but if you dont aks you dont know.So guys, what is the max RPM suitable for this engine? Which is the best range were to keep runing and get the optimal performance for such engine.

Take in consideration I cannot go bigger than 24 or 25 due ground clearance.

Will a 3 or 4 blade propeller help with vibration at hig rpms? what gain what to loose.


Lets go guys, I´m here to learn from the experts and please get focus on the 5.8 and ask me more info if you need
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Old 09-01-2007, 01:58 PM
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Wings-RCU
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Default RE: Brison 5.8 best performance

Wow, something is wrong! My 3.2 will spin a zinger 22x10 around 7100. A 22 x 8 3W prop at 7300. The 4.2 should spin a 24X10 at 6500+. The 5.8 should spin a 26 x 10 at 6500+.

Yes try a 3 blade (it will not help the vibration), check your timing & adjust the needles.

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Old 09-01-2007, 02:49 PM
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Default RE: Brison 5.8 best performance

Wings:

What is for sure is that I get less rpms here than in USA, maybe the fuel but most is due air density wich is much lower even if I´m at sea level. Same happens with outboards race engines, we get les power here.

Timing is factory set and advance is electronic due the new Revmaster electronic ignition.

DP
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Old 09-01-2007, 03:07 PM
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Default RE: Brison 5.8 best performance

Check the ignition timing. It should be set at 28 degrees before top dead center. If it's less than that you will have low rpm counts.
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Old 09-02-2007, 08:28 AM
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Default RE: Brison 5.8 best performance

At first lok and checking, the teflon ring that hold the sensor is blocked with a set screw wich is in the spot already drilled from factory, but you could be rigth, let me to install a degree wheel and have numbers in my hand.

But how much are the max rpms alouded for this engine Pat?

DP
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Old 09-02-2007, 08:38 AM
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Default RE: Brison 5.8 best performance

Prop, timing, and altitude have a lot of control over that area, but anywhere from 6,500 to 7,000 would be accceptable for me. Any more is a bonus. You're seriously underpropping the engine with a 22" prop. You would be just as effective flying the plane with a smaller engine. Go to a 3 blade prop in the correct size to provide the ground clearance you need.
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Old 09-02-2007, 12:57 PM
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Default RE: Brison 5.8 best performance

8A36,
Be sure that you baffle the cowl, so that all of the air is forced to go throuh the fins. Make sure that the cowl exit area is 1.5 times the inlet at the fins and the open cowl flaps should help draw out the air also. This should solve the overheating issues. Also as mentioned above, use a 24x12 or 26x10 prop and it should get close to 6,500 rpm. The flywheel action of the larger balanced prop sould help reduce vibration. Timing and mounting need to be good as well. Good luck.

Dave

PS: The typical carb has a spring on the throttle shaft which prevents vibration from allowing thr throttle to cruve the throttle bore. Check for this.
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Old 09-02-2007, 03:34 PM
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Default RE: Brison 5.8 best performance

DP, my favorite prop was an NX 24x12 on my Brison 5.8 powered Ziroli Corsair.
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Old 09-03-2007, 08:46 AM
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Default RE: Brison 5.8 best performance

Ken. how many rpms you get with this prop and engine combination?

David
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Old 09-03-2007, 10:05 AM
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Default RE: Brison 5.8 best performance

It's been a while but I think it was around 6500. Unfortunately I lost the plane last year at Bomber Field due to radio failure. Over 100 flights. Here is one sleightly used Brison 5.8.
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