REFLECTOR: Engine RPM Troubleshooting / Loaner Prop?

[steve korney]

"Late timing might also give low EGT and
incomplete burn (soot)."

I think that would raise the EGT's... Sound way to rich ...

Best... Steve

> From: ALVentures at cox.net
> To: reflector at velocityxl.com; reflector at tvbf.org
> Date: Thu, 10 Apr 2008 21:29:25 -0800
> Subject: Re: REFLECTOR: Engine RPM Troubleshooting / Loaner Prop?
> 
> Brett;
> 
> My sense of this is that the engine is not putting out its advertised power.
> Possibly some issue with timing or mixture.
> 
> What is the rpm for the rated 306 hp?  I'd assume about 2900.  My 20B rotary
> gives 265 hp at a prop speed of 2900.  It would spin a Catto 66" x 85" pitch
> to around 2450 static at airport elevation of 1400'. I don't recall max rpm
> in the air, but I think it was maybe 2600.
> 
>  The 68" x 82 pitch would absorb similar power; maybe a bit more, but I
> think your engine should spin that to 2500 static if it was performing
> properly.  Since one major change since the dyno run was the ignition, that
> might be something to check. Late timing might also give low EGT and
> incomplete burn (soot).
> 
> We have since reduced pitch to 80" with a smaller blade root, and I now get
> over 2500 static and bit over 2900 WOT in the air.  The lower pitch gave
> some improvement in takeoff and climb performance, and maybe a bit more top
> end.
> 
> Al
> 
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Brett Ferrell
> Sent: Thursday, April 10, 2008 9:43 AM
> To: reflector
> 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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