ORIGINAL: Red B.
ORIGINAL: da Rock
Do you have the numbers for that? What is the difference in power?
After Googling for some performance figures :-) I found the following figures to be rather representative of what one may expect from these engines using 15% nitro and rather typical propeller sizes:
OS46AX, APC 11x6, 11.7 krpm
Saito 82a, APC 14x6, 9.2 krpm
According to the manufacturers the OS has the edge with 1.65 bhp at 16000 rpm vs. 1.5 bhp at some unspecified RPM for the Saito.
Because we often use propellers that give RPMs below peak power RPM only some fraction of the peak power is available.
Using Pe Reivers [link=http://home.wanadoo.nl/pereivers/prop-power.xls]prop-power spreadsheet[/link] I found that my RPM measurements are equivalent to power otuputs of 0.9 bhp and 1.1 bhp for the OS and Saito respectively. The static thrust would be 6 lbs for the OS and 8.5 lbs for the Saito.
My interpretation is that the Saito develops its peak horsepower at RPMs that are much closer to the RPMs listed above than is the case for the OS, thus a larger fraction of the peak bhp is available from the Saito compared to the OS.
In my experience the figures above seems reasonable and when comparing my own OS46SF and Saito 72 engines that weigh about the same I have observed that the Saito provides more static thrust, shorter take offs and faster climbs compared to the OS even though the OS have a higher peak BHP.
For high speed aircraft, where high rpm and high peak bhp are both of importance I would choose to use the OS.
/Red B.
Excellent.
That illustrates both our posts very well.
It's to everyone's advantage to take a sensible look at all the details. Since you've provided a comparison between two specific individual of the two general types, let's go a step further.
Which is heavier?
Which is more complex and might require more maintenance.
Which has more power for it's displacement.
Which has more power for it's size/weight.
Which is more expensive.
Heavier? They're about the same. Since the original basis for comparison used equal displacement, what does either a Saito 46 weigh or an OS100? The smallest Saito is almost a 60size. Comparing 45s to 60s is a stretch. The closest OS to a 100 is the 91FX and it's about 24oz.
More complex? The 4C
More power for it's displacement? The 2C
More power for it's weight? About the same? Is this true of all 4C's?
Expensive? The Saito is over twice the price of the compared 2C.
If the original topic was "what is the difference between an OS46AX and a Saito82, we'd have that topic covered.
But truth is, I hope everyone sees the general differences as well as getting an extensive discussion that illustrates the detail needed to compare two very specific engines. You'll very often benefit from shopping around. And looking very closely at every detail of the choices.