REFLECTOR: Engine RPM Troubleshooting / Loaner Prop?

[Ron Brown]

My comments here - Several folks have had this "problem" with Craig's 
initial prop.

I had it, Oscar in Florida, and several others.  My impression is that Craig 
will deliver you a prop that has too much pitch more often than too little. 
Apparently he can lessen the pitch on his existing props easier than 
increasing the pitch.

He turned my prop around quickly after I gave him actual numbers from static 
and wide open throttle along with temperatures and altitudes.

My first prop would (Oscar's is similar) on my IO360 would only turn about 
2250 static and wide open was 2550.  After repitching, I now get about 2450 
static and a little over 2700 at WOT at 8000 feet.  That is what I wanted 
initially (I asked for a climb prop since I am based at a relatively short 
field - 3000' and 840 MSL).

I was very happy with the performance (roll out is like starting in "2nd 
gear" versus high gear).  I didn't loose that much on top end, perhaps 3-5 
knots.

Ronnie
N713MR
173 Elite RG

----- Original Message ----- 
From: "Brett Ferrell" <reflector at velocityxl.com>
To: "reflector" <reflector at tvbf.org>
Sent: Thursday, April 10, 2008 1:42 PM
Subject: REFLECTOR: Engine RPM Troubleshooting / Loaner Prop?


> OK, I guess it's my week for hogging the reflector.  If you've been 
> following our progress at all you know we've had Dave Bertram fly our 
> plane a couple of times, and we've been fighting engine RPM the whole 
> time.  I've been getting some really good advice, but since I think I need 
> to find a smaller prop at least to break the engine in with, I thought I'd 
> come to the collective wisdom.
>
> As background, we've got a zero time rebuilt IO540D from Magnum engines 
> with high compression pistons.  It was dynoed at 306 HP by Lycon, but I 
> believe the dyno was done with mags, and then Magnum installed my dual LSE 
> plasma III ignition.  The dyno information was given to Catto, who built 
> us a 68x82" 3 blade fixed pitch prop, which for some reason we can't swing 
> better than 2150 RPM static.  On the second flight Dave got off the ground 
> in about 800 ft, and had to throttle back to hold under 160 kts, so there 
> is power there, but the RPM in flight never exceeded 2335.  The RPM is 
> coming off of the LSE, and we've prop tach'ed it, so I think it's 
> accurate, which my fuel flow gauge isn't (a Floscan 231, once the engine 
> starts it's readings go nutty).  Also, on the last flight, the EGTs never 
> exceeded 1083 on the hottest cylinder and 990 on the coldest (EFIS/one 
> tracked).
>
> So, what I'm looking to do is try to eliminate possible issues with the 
> installation in as logical fashion as possible.  Catto mentioned that when 
> Berkut couldn't develop >500 RPM from static to in-flight they found the 
> intake was choking the engine, so tonight I'll run it without any hosing 
> attached to the intake and see if we get better RPM from that.
>
> I'm also going to ship my servo back to Airflow and have them readjust it, 
> since we've diddled with it, and I think (based on the EGTs, which should 
> be I'm told 1250 or better) that we've got it way out of adjustment.  We 
> had soot on the blades after the second flight, so I think it's over rich, 
> but it could be too lean I suppose.
>
> Meanwhile, I'm looking to borrow or buy a shorter prop, so if anybody has 
> one they can loan or sell me, let me know.  We really need to get 2750 RPM 
> to break the engine in, and I wouldn't expect to get more than 2450 static 
> with our prop, and don't expect Dave to make 190 kt circles over the 
> airport till it's broken in!
>
> Brett
> www.velocityxl.com
> www.n44vf.com
>
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