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04-11-2011 | 10:18 AM

#19

DarZeelon

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From: Rosh-HaAyin, ISRAEL

RE: anybody know the difference?

Quote:

ORIGINAL: madman75

Ed,
You seem to be somewhat of an expert on these matters. Which is the way to go? The .91 or the 1.08? It seems the Magnum is pretty much the same as the ASP. Am I right on this? Why is the .91 rated to 17,000 rpms and the review stated that 13,800 rpms was achevied? I have seen conflicting info. on the rpm numbers for the 1.08. I have seen up to 10,000 at one place and up to 17,000 another. What's your take on this and what have you seen from the 1.08's you have? I have seen info. where OS did the same thing with their .91 engines. Basically ''punching out'' a .61. It seemed to work for OS for a while. I'm just trying to find out the best route to go. So, whats your take on the Magnum .91 as compared to the ASP 1.08 considering the 1.08 is 5mm wider and 100 grams heavier?
Oh, I did some more checking on the shipping. There is a cheaper shipping available for $21 that is for 6 to 21 days delivery. That would put the HK 1.08 at $99.

MadMan,

The manufacturers' HP rating and RPM are , for all practical purposes, lies.

It is possible that such an engine, on the highest possible nitro (and shimmed to tolerate it); on a tooth-pick prop and with an ideal tuned-pipe system, could achieve the rated figures...

But in its unmodified form, with usable, affordable fuel and with its standard muffler; it cannot even be expected to come close to them.

Please read the [link=http://www.modelairplanenews.com/ME2/dirmod.asp?sid=&nm=The+Magazine&type=PubPagi&mod=P ublications%3A%3AArticle+Title&mid=13B2F0D0AFA0447 6A2ACC02ED28A405F&navid=&tier=4&id=5687A613FD1B465 6848EF02416CE7FEF&PageId=4AF907D8C43F4CD18CB07D708 BF47082]additional info[/link] from David Gierke .60 engine shootout, MAN May 2003 issue.
Compare the actual HP numbers, to what the manufacturers say...

Serious manufacturers who appreciate the intelligence of their customers, give you a go/no-go number, RPM on a certain prop and with a certain fuel.

- - - - - - - - -

A punched-out .91 engine (in a .61 size-frame) generally has narrow bypasses and is more inclined toward low-RPM power - that's the ASP .91...
A 'real' .91 engine, is larger and the ASP (and OS) 1.08 has larger everything and will run at higher RPM, making more power.

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