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rlaird
Joined: 10 Jan 2006
Posts: 373
Location: Houston
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 Posted: Thu Feb 18, 2010 8:51 am Post subject: Valley Engineering Big-Twin - Any one flying with one? |
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On Thu, Feb 18, 2010 at 10:15 AM, Mike Welch <mdnanwelch7(at)hotmail.com (mdnanwelch7(at)hotmail.com)> wrote:
| Quote: | Rick N,
Oops, I misspoke about the "Big Twin". It isn't the half-VW I said it was. It is the Generac V-twin. (I said my knowledge was vast, I didn't say it was accurate!!)
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So, are you saying that you are vastly inaccurate? 
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IMO, if you require a turbo on a Generac just to make it worthwhile to power a plane, you're much better with off with a 503!! For the Generac to be a successful airplane engine, there needs to be a hellava lot more engineering and development on it.
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Jimmy is apparently out earning his dollars for the day, so, speaking as someone who has flown his plane, and seen the Generac installation (and the 503 he had, before it, and the HKS he now has), I can say this (and I'm Jimmy will correct me if I state anything wrong):
His plane flew fine with the 503, just as scores of FSII owners know. He was looking for 4-stroke reliability and decided to try the Generac, and spent a lot of resources making sure it was done right. He also swapped out props as directed by the Valley Engineering people. Final result was, it was essentially underpowered, compared to the 503. Now, if he flew out of the 3000 ft asphalt-runway, and never landed at anything shorter or rougher, he probably would have stayed with it. But he flies out of a fairly rough turf runway that is very short, so he needs a good bit of power to consistently get in and out of there safely. The Generac was mounted flat on the mount, but it was remarkably smooth. But, even being a smooth engine doesn't mean he didn't need the Lord mounts. The rough field translated to the mount and the engine with detrimental effects.
With the HKS, he is now a very happy (if poorer) aviator.
-- Robert
[quote][b]
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_________________
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Robert Laird
formerly: MkIIIc w/ 912ULS & Gyrobee
current: Autogyro Cavalon w/ 914ULS
Houston, TX area
http://www.Texas-Flyer.com |
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Jimmy Young
Joined: 24 Nov 2007
Posts: 182
Location: Missouri City, TX
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| Posted: Thu Feb 18, 2010 11:51 am Post subject: Re: Valley Engineering Big-Twin - Any one flying with one? |
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List,
I did a few in-detail posts of my experience with the Valley-Generac Twin V, they should all be in the archives.
To clarify a few comments made today,
1) Valley Engineering does not cut down the flywheel in any way on their version.
2) They (Valley Eng.) do suggest to mount the engine direct to the airframe. My opinion is, not a good idea. Even though it's a fairly smooth engine, it's not smooth enough to do that, at least it wasn't for me.
3) I tried 4 different props. A 3-blade 72" IVO, 2 blade Culver 76" 39 degree pitch, a 2-blade 76" Culver 41 degree, and a 2-blade 78" Culver, either 41 or 39 degree, can't remember. There were subtle differences between each, nothing substantial. I got a little better cruise speed with the 76" 39 degree over all the others, but cruise speed was not the problem I was trying to overcome, it was lack of adequate climb rate, and none of them solved that.
4) Yes, today I am broke, own an HKS, and am very happy with it.
I also had a bit of a rum-rum harmonic issue going on as well with the Twin V, and Larry Smith at Valley told me they had that problem solved with a different redrive ratio. Also, the last time I spoke with Larry they were trying out a different cam grind to get more power out of the Twin V, and at that time they had given up on the turbo ideas.
They are very good folks at Valley Eng., even took my engine back at a fair discount. They worked hard with me to try and make the engine perform to my satisfaction. Bottom line was, the Twin-V was not enough power for my application.
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_________________
Jimmy Young
Missouri City, TX
Kolb FS II/HKS 700 |
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