Saito specs from manual:

SPECIFICATIONS
Disp 36.3cc (2.20 cu in)
Bore 38mm (1.49 in)
Stroke 32mm (1.26 in)
Weight (Engine only) 44.2 oz (1253 g)
Weight (Muffler only) 3.0 oz (85 g)
Weight (Engine Mount only) 9.6 oz (270 g)
Weight (Ignition only) 3.7 oz (105 g)
Total weight (all inclusive) 60.5 oz (1713 g)
Crankshaft M8x1.25
Cylinder AAC
HP 3.5 approximately
Fuel Efficiency 30cc/minute
Propeller Size Dia. 18–19 x Pitch 8–9; Dia. 20x Pitch 8
Benchmark Propeller APC 18x6W @ 8,300
Practical Ground RPM Range 1,700–9,000

Originally Posted by Aeroplayin

Nathan, what 40cc are you using and is the 1300g you are reporting the engine, ignition, and muffler weight? I'm trying to decide if I can put a Q80-7M on 10S in a 78 so that when the 78/87 MXS comes out, I can use it.

From what I see right now, the 78 with the Hacker A60-16M, and the A60-MM mount, is only 6100g total. The Q80 may only add 71g and I should be able to move the 3 cell 1400mAh Rx battery and BEC-Pro back to compensate.

This would give me the same Kv, but a motor that can spin a 22x12W or a 23x10 Mejzlik to 3700W easily, and at 6-plus minutes. It's already spinning a 24x10TH to 4400W and only 116A now.

you would even save some weight due to very small standoffs.
apart from that it doesnt sound right to me.
i had a q60 in there and now the pletti evo. its more than enough power. with that weight you speaking about you could go with a very big battery instead.
also a 23x prop is too big.
then again, i would like to see it

I never use terms like 'too much power', or 'more than enough power' because it is just too subjective. Enough power is as much as you can put on the plane and still balance it, fit it all under the cowl, still swing the prop without getting green tips from the grass, and still support a battery capacity for a realistic flight time.

The plane won't support "too much" power. If you don't like the upper limit of the plane's power, then limit the throttle curve or prop down. Eventually some of us will feel comfortable enough with the plane to want to put the bigger prop back on. Rarely do guys fly the plane for a few months and decide that the pull-out is just too good.

We don't leave anything on the table when it comes to power.

yes, there are personal preferences in desire of power.

however, the type of plane the 78extra is, you dont want jumping the plane around caused by very little stick input.
and you dont want loosing neutralty due to a too big prop.

Yeah, I've heard about people complaining about torque and precession affecting the attitude of the plane, but there are videos of all of our setups and you won't find visual evidence of this happening. I'd like to see this actually happening from someone with the same setup that feels it is happening. Of course, I have not yet put a 23 inch prop on the 78, but I don't intend to. I may try it on a 87 MXS, but with the Q80 on 10S, the 23 won't be the only option. It will only be an Extreme option, which is always nice to have, and not many will have with a lesser motor.

ok, i agree and its interesting.
but, where is the sense? (all the half kg lesser motors can swing a 22x12)
are you basicly looking for a new home for the q80-7 ?

I live in Florida. Although the temps rarely get above 91 degrees here where I live near the Gulf (all readings in F), the flying field can get much warmer. The A60 currently operates at between 161 and 170 degrees now, when the temps are between 68 and 78 (typically). My guess is that the Q80, which is an open design and built to manage more Amps than I would need on the 87 MXS, will operate more efficiently. This means that although I will produce the same 3500 to 3700 Watts on the same number of cells, with the same current, I will be operating at 20 to 30 Amps less than the motor was designed for.

The other reason is that the MXS will have a wingspan that is 9 inches longer. I suspect that this increased drag will affect the power output of the A60, which is already operating at its limit, while the Q80 will probably not feel it.

It is also only a 70g difference (2.5 oz) when you add the A60-MM cage mount that will not be needed with the Q80. I will still need to weight the standoffs, but there are ways to keep the weight close.

hmm yes...the heat of florida summer

imho best motor money can buy if you want great power for either 78extra or 78mxs is the pletti evo 30-9, florida summer wont hurt it
http://www.plettenberg-motoren.com/g...tschrauben.htm

probably selling the q80-7 will just give the cash for it

Yes, I have the plettenburgs bookmarked and I was considering them for the next project, which is a bit bigger. They say the 26x10 will use the same current (118A) and produce 37 lbs of thrust as my Q80 on the 24x10 producing 32 lbs, and on the same volts. That, I would like to see.

Originally Posted by Aeroplayin

Nathan, what 40cc are you using and is the 1300g you are reporting the engine, ignition, and muffler weight? I'm trying to decide if I can put a Q80-7M on 10S in a 78 so that when the 78/87 MXS comes out, I can use it.

From what I see right now, the 78 with the Hacker A60-16M, and the A60-MM mount, is only 6100g total. The Q80 may only add 71g and I should be able to move the 3 cell 1400mAh Rx battery and BEC-Pro back to compensate.

This would give me the same Kv, but a motor that can spin a 22x12W or a 23x10 Mejzlik to 3700W easily, and at 6-plus minutes. It's already spinning a 24x10TH to 4400W and only 116A now.

the 40cc is a crrc pro 40 its a kit engine where you build it but on theire website it says 1300 as a dry weight i think this is including the muffler but not certain this does not include the rcexcel ignition and ignition pack but for a kit engine the power is amazing there is a link here for their websitehttp://www.crrcpro.com/product_show.asp?id=225

when im next at at spacebats (this weekend) i will check the weight including ignition pack and everything

Originally Posted by Dead

Thanks Nathan!

Is your 40cc a 2 stroke?

yes

Originally Posted by Dead

DLE lists 1800 RPM and 18 to 20" prop.

Saito lists 1700 to 1900 RPM on 18 to 20" prop.

But the DLE lists a 20 x 10 and the Saito lists a 20 x 8

on the 40cc im running a 19X10 but will move up to 20X10 when we get the plane its currently idleing at 1800rpm and top rpm we are getting about 7000 to 7500(havent fired it up in a while) with 97 octane fuel we are getting about 4hp

Looks like a fun project and a great way to learn about engines. Keep us informed on the props you settle in with and how the power feels. I posted in the 78 thread about my consideration of the Evolution 45cc for this plane, but the weight was a bit high, driving the Reynolds number to a level I don't think I would be happy with. I can duplicate, and actually exceed, the power with the A60-16M and the 22x10 Xoar. The Castle logger is showing between 3550 and 3700 Watts with this setup and the all-up weight is still 6088g (13.46 lbs).

The engine is really smooth and really no delay in the throttle response