There seems to be a new trend in leting the engines to run faster so that more thrust is produced due to the engine being in its power peak. Sur the engine will be louder but tuned cans and muffled can get more and more popular hence the fact that smaller props for a given engine become more popular.

I plan to fly a ZDZ80RV on 80x300 can from RCS with a Mejzlik 26x10. It seems that I should get between 6500 and 7000 with this prop and muffler combo.

Question: what are the effects to the engine as far as temps, longevity, fuel consuption, etc. ?

Lots of guys around here load their engines to death and I want to be able to prove them wrong, or if it is me that's wrong, at least I will change my prop.

Thanks all.

A 26x10 should be a good prop for the 80 @ approx. 6500

Decrease-Longevity

Increase-fuel consumption

When you say higher RPM's do you mean 8000-9000?
I do not know the torque/HP curves for this engine but going with Higher RPM's would more than likely gain nothing and loose much in all of the above.

The timing/tuning of an engine will determine what RPM range is best for it. Every engine manufacture has their own preferences. It would be nice if they would publish the Torque/HP numbers. That way you would know exactly where you need to be before even running the engine. There would also be less fighting over the irrelevant HP #'s
Here is an example by Zenoah

I Know Dick's out there, he will give you the low down.

Beware, long post.

When searching for the "best" RPM there are no quick and ready solutions, because one has to consider a few things to get all elements of the system adjusted to each other.

First
Like already said, what is the power curve of the particular engine, and as important: what does the torque curve look like.
second
How does the muffler used, influence the power and torque curves.
Third
What plane is to be powered. Pylon >>>> Floater
Fourth
What prop tip speed are you after. Low noise (0.6 mach max.) or noisy (>0.7 mach)

For power, it is best to prop static between max torque, where the engine is at it's best efficiency, and max power, so the engine can unload in the air to achieve maximum power.
This power not necesseraly translates into plane performance, because propellor efficiency and plane drag factor also enter the game.
A high drag floater is better off at lower rpm near max torque. This allows a large, lower pitch prop with an equally large and relative slow propwash. This provides high efficiency despite the bulky fuselage.
A sleek narrow speed plane should use a small diameter high pitched thin bladed prop. The fuselage is not the limiting factor, so prop wash speed may be higher, and thus the end speed that can be achieved. RPM at top speed should be at peak power rpm. Tip airflow will be supersonic in many cases, so the planes are noisy by nature, even in the presence of excellent mufflers.
A 3D plane also has a narrow sleek fuselage to keep fuse drag low. Since no high speed is needed, and best prop acceleration is the goal, the prop load should be light enough to achieve peak power rpm at low speeds, in order to have best prop acceleration from reduced throttle rpm. At the same time, a high volume, low speed prop wash is required for best efficiency and control surface action, which relies on the propwash. 3d flight mostly is low and near, so sonic prop slap is a nuisance to be considered if you fly together with other pilots, or when the field has noise restrictions.

Even then, experimenting in search for best results is necessary.

Trends:
In Europe, the trend is towards lower rpm because of noise limitations, so a lot of work is being done to find a prop that allows the performance we are after at these reduced rpm, and yet achieve good 3D flight, which is becoming increasingly popular. Electric flight already took over in the small plane classes. The high torque outer rotating magnet motors are coming of age, so soon decent sized 3D planes will be electrified as well.

- and to add a little:
we fly electrics also - and use Hacker outrunners as well as our real joy- tiny CDR rewinds
these things are truly ballistic.
Properly setup-cooled and adjusted - the increase in revs will not result in decreased life - rather look for an increase.
Why?
loaded engines generate more heat and the bearings take it right up the colos .
Look at what happened to the glow stuf when the big slow turning props beacome popular - same thing.
the surface speed on the piston is actually moderate -and if people would go to oil setups which really work - the rest of the carbon/scuffing etc -would really only become related to incorrect needle settings.
3D on most gassers is really not much above 1.5-1 thrust to weight .
Get your setup propped to jump into about -- 3500+ at hover- this should put you right in a sweet spot for bouncing the throttle stick for minor flight changes
propping to hover down at 2500 (if possible) puts one way below good carb flow etc..
On the ZDZ80 - the Mejzlic is good for- say up to 24 lbs -will still hove up to 28 pounds - done it - but the setup is a turkey.
Finally as I am sure most will agree -using a properly designed tuned pipe - one can run the peak torque UP to best performance in th 7000 range.
That's what pipes do best- increase (raise) peak torque band

Thank you guys, great information.

To make me more clear, I should have said : Is it better to prop an engine at 5000 (this is where guys around here prop their 80) or at 6500-7000 for the life of the engine. Knowing my engine will perform in this range, I will use throttle management so that I will not rip the prop in level flight (a thing I do anyway for fear of flutter even if I never experienced flutter).

I should also have added that the plane and engine will fly IMAC advanced and 3D. These new sequences require ALOT of thrust...

From the answers given, my engine should be happier at 6500-7000 and the only drawback would be a higher fuel draw. No big deal, I will fly with 32oz of gas.

Thanks

EDIT: as for fuel draw, I sincerely think that throttle management can do a big difference in that area. I did 15 minute flights with a 140DZ on 30% nitro with 20oz of glow fuel with 3 or 4 oz left for landing.

3D
Do exactly what you just stated.

For some reason I had it in my mind that you wanted the 8000+ range and your freinds ran in the 6500's, sorry for my confusion.

I ran a ZDZ-80 with Mejzlik 26x10 prop and J&A pitts muffler. It would tach 6700 rpm. No issues, over 350 flights, no worn out parts inside. I know a flyer who had an on-board tach on a DA-100, it showed the engine unloaded 1000 rpm in the air on a 25x12 Mejzlik 3-blade. I would guess the ZDZ will also unload in the air and it will be in the 7700 rpm range. Another friend had the ZDZ-80 with the K&S tuned muffler (#89) and 12" header. His engine wasn't happy running the 26x10 prop (didn't sound smooth in the air). Switched to the Menz-S 27x10 - 6400 rpm and it sounded better and ran much smoother in the air. Perhaps the header length was wrong for the 26" prop and high rpm.

I was never thrilled with that model "tuned muffler"
My preferrence is the one that is front in -rear out.
6400 on the 27x10 MenzS is crankin good power tho.
One thing I found with the ZDZ - when tuning with exhaust pressure - you can run into the "overcompressed " situation that occurs with blowers on cars.
just bumping the timing back a little may fix a ragged running and or quick heating problem which reduces power.
This is simply detonation -or pre ignition (no such thing as pre detonation as it is sometimes labeled ).
I have some race gas that I am going to try -on the bench - just to see if I can bump up the cylinder pressure any more .
I won't fly this stuff - just fiddlin around.
the slight setback in timing seems to be a easy - good running fix.