[NSRCA-discussion] Thoughts about lack of power of my DA150??

[PPandelaers]

Hi Jason,

 

The plane I', flying is an Extra 330S from PL_Prod (now PLF). I did do front
baffling, closed the cowl hole in front f the carb. So most of the air for
the carb is the cooling air of the engine

 

Everybody seems to agree that the RPM's are about right. My altitude is
about sea level. Nevertheless, my competition friends "claim": they are
running 5800, this was my reference.

 

The headers I'm using have a length of 310mm, so it seems that I indeed
could shorten some and see if it helps. DA has responded, I'm waiting for
the port timing, so I can rationalize the need for shortening the headers.
DA is shipping it's standard headers at  305mm.

 

I have made sure to avoid a blast in the carb vent hole for sure.

 

I have always been very sensitive when turning in the needles, so I don't
think I have damaged anything.

 

Still, with the recommended needle setting I have very poor throttle
response in the air, just far too rich in low to middle, not achieving full
power at full. I was thinking my header length had something to do with it.
But now I see, I'm at the standard length of DA_headers. So what else could
be wrong?

 

BTW: 

*	What prop are you running, what RPM"s??
*	Total distance to the rear muffler plate?  In my case the MTW
TD110k's add 310 mm to the headers.

 

Thanks!!

 

Patrick

 

 

 

-----Oorspronkelijk bericht-----
Van: JShulman [mailto:jshulman at cfl.rr.com] 
Verzonden: maandag 6 februari 2006 23:44
Aan: ppandelaers at pandora.be
Onderwerp: Thoughts about lack of power of my DA150??

 

Patrick,

 

What airplane is this in? What does the cowling look like? Baffles? Carb
area? 5600 on a Mej 32x10 sounds about right. One thing you should do is
have the low at no less than 1/2, and the high not less than 2 turns. And
when you turn the needles all the way in, do you make sure they're closed?
If so, you can distort the carb needle seating in the carb making it more
difficult to set the needles correctly. When you close the needles, make
sure you do not do it hard. The only thing with the carb tube I've found is
it makes the motor run leaner. I just make sure not to blast the carb hole
in front. I just make a cover so it can't get direct air through the hole.
My headers are 265mm long and it seems to work well.

 

Hope this helps.

 

Regards,
Jason
www.jasonshulman.com
www.shulmanaviation.com
www.composite-arf.com 

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of PPandelaers
Sent: Monday, February 06, 2006 5:27 PM
To: Discussion at Nsrca.Org; Mini IAC (Mini IAC)
Subject: [NSRCA-discussion] Thoughts about lack of power of my DA150??

Hi guys,

 

I'm wondering if you have opinions on my below assumptions. It's a mail I
have sent to DA, but no answer as of yet. 

 

Could I be right, should I rather lengthen or shorten my exhaust system?

 

Thanks

 

Patrick

 

 

 ============================================================

I'm running a DA150 on MTW, short cans TD75K, Mejzlik 28.5x12

 

 

Started running-in the engine a couple of months ago. >From day 1, I got
5600 RPM.

Now, 50 liter gas down, no change at all in RPM :-(  I get exactly the same
RPM on a 32x10 2-blade.

I'm experiencing great difficulty in adjusting the engine. I don't seem to
be able to get full power, particularly not in the air. I get the feeling I
don't even get the 5600 in the air.

Tried about anything you can imagine, with adjusting needles, soldering a
little tune on the diaphragm cap, measuring pressure where it should be
done.

 

 

Let's forget about air behaviour, I would expect significantly higher RPM,
even on the ground. Motor is not sagging when I keep it running full
throttle, I baffled the engine, cooling is adequate.

 

Here's what I think is going wrong, I would really like to get your opinion
on it.

At 5600 RPM, I think I get some refection of the exhaust system exactly
during the intake timing.  If this is so, I just can't get enough mixture
inside the cylinder. 

At low RPM, it's always running rich, if I want to improve that, I have to
tweak the "L" as low a 3/8 (instead of the 5/8) . The high needle is not
sensitive at all, it's like it doesn't matter where you put it. With the
low, at 3/8, starting a cold engine takes several restarts.

 

The distance of piston to the first wall in exhaust systems is about 630mm

 

*        Could I be right? 

*        How much would I have to lengthen or shorten the exhaust tubing? 

*        Secondary questions: 

o       How many degrees is the intake open, 

o       When does the intake open: How many degrees from exhaust opening
(piston moving down) till intake port opens? 

*        What RPM should I expect on the Mejzlik 28.5x12. 

 

 

 

Your advise would be highly appreciated!!!

 

Patrick

 

 

 

 

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