Earthstar Forums

Well, I had a pretty good crack in my exhaust system. I ended up
getting the new exhaust system from Mark B at TG and had it sent to
me. Mark responded very quickly to the problem I had.

The new exhaust system is much sturdier than the old one and does
seem to be a little more quiet. It is one piece instead of two and
solid throughout, however, it did not fit very well on my particular
HKS engine and I had to do some more modifications to get it to work,
and even though I was informed I was wrong about the fit and I am
still slightly disappointed in the fit, I did manage to get it to
work.

2 things I have noticed since I put this on:

(1) I seem to have a whole lot less power than before. The mufflers
appear to larger and I understand that they are baffled, whereas the
other one was not. I test flew the plane at my homefield without
much problem. I happen to have a 5000 ft runway here so I don't have
any problems getting up after a long rollout. My rollouts are about
100-150 ft longer than they were previously. I noticed that I could
only get 4800 rpm when I went to full power at first (previously
could get 5800 before starting to rotate. OK, I now have to adjust
the degrees on the adjustable prop. I have since adjusted the tips
ending up with minus 2 degrees from my previous setting which has
helped the climb a bit, but it is still not the same as I had. My
rpms now go up to 5600 on the rollout before climb now. Cruise takes
a little more power than before to get the same results, but I can
get the rpms up to about 6100 (just below the 6200 max for 3 min
mark). It still takes me a while to get off, so I am going to adjust
another degree down and see what happens.

(2) I also now use 0.2 gal more per hour than before. This is not
really bad, but is just another indicator my performance is not what
it use to be.

I just finished a 335 mile round trip to a flyin and back, so I got
some good numbers to base where I am at now off of. My friends
strip, where we went to the flyin at, is a 1300 ft long grass field,
very smooth - I took about half of it to get up in the air and still
didn't have great altitude when I went over the trees at the end.
The only change in the engine and configuration has been the
replacement of the exhaust system and adusting the tips 2 degrees
less. The engine seems to shake a lot more at idle and startup, but
that may just be the exhaust system being solid with no give as
before, which was the part of the cause of the crack. Cruise seems to
be Ok, but I need higher rpms now than before to maintain the same
speeds I use to.

I am thinking the new exhaust system with the baffling has changed
the backpressure a good bit and is the main culprit here. Does this
sound right to the rest of you and if not, what do you think may be
another factor.

I may try to reweld the old exhaust system I have to see if the
larger mufflers and baffling make that much of a difference. I like
the new muffler better since it appears to be more solid and quieter,
but I also like the old performance a lot better as well (especially
in both climb & cruise).

At the moment I am not sure I would recommend this muffler, except
for the fact that it appears better built and that it will last a lot
longer than the other one. Kind of mixed up in how I feel about this
overall at the moment.

Jim C

Jim,

I am new to the list, so please forgive my questions...

is yours a two place Gull or a single place?

How much do you weigh and what is the biggest pay load you have
carried after full fuel?

Bill in central Florida

Whew, 2 degrees less pitch. Pitch it in the trash, or back on the truck
for a refund. 4 strokes love lower backpressure. Most GA engines are
loud for a reason, power. Those VW engines I have seen can't get off the
ground with a quiet muffler. Some run straight pipes, very loud.

Good luck

Jay D

Mine is a 2 place J2, 400lb empty. I'm about 210. I've carried another at
190 and full fuel. I run with a 503 dual carb.

George

Hey Bill,

I have a Gull 2000 single place with the HKS engine. I weigh in at
about 225 and have had about another roughly 80-90 lbs in the plane
(tent, sleeping bag, ground roll, small duffle bag for overnights and
2-3 day stays, flight bag, computer, front window cover, engine
cover, tools, small chair, tiedowns, and drinks and munchies, etc.)
I just fit them in all the nooks and crannies in the plane. My Gull
is on the heavy side to begin with since it has an all fiberglass
body and aluminum wings etc. It is a great flying machine. As it
is, I love this plane, although I would think it to be totally ideal
if I had a bit more room in the back for stowage.

Jim C

-- In ThunderGull@yahoogroups.com, "Jay D" <jdewberry@p...> wrote:
> Whew, 2 degrees less pitch. Pitch it in the trash, or back on the truck
> for a refund. 4 strokes love lower backpressure. Most GA engines are
> loud for a reason, power. Those VW engines I have seen can't get off the
> ground with a quiet muffler. Some run straight pipes, very loud.
>
> Good luck
>
> Jay D

Jay,

I was actually surprise to see how much of a difference a couple of
degrees in pitch makes to performance. Once in the air and up to
speed, she still performs very well, but not as before. Instead of
1.8 gph though I am way up there at 2.0 gph. Cruise is down a little
as well, at the same settings that is. Full power nets about 5-7 mph
less, but I don't usually go that fast anytime. Climbout is the big
difference. My climbout needs to be a little better when I am loaded
down, thus the change in pitch adjustments. The 2 strokes do have it
over the 4's in this area, no doubt about it, but if it is just the
way the muffler is designed, maybe I can deal with that. We will see.

Jim