Aeronau-tech

I'm putting a ST G90 on a Hobbystar Mk III. I needed a muffler for it and the hobby store sold me one for a ST 61. They said it would work. Tonight I looked on the Macs site and it doesn't have a muffler for the ST G90.

Has anyone tried this, are there any mods to make it work?

BTW The ST G90 came off a 47" Ballistic OMP EDGE 540

speedster 1919

My Feedback: (3)

It will bolt up .MAC"S Not enough flow for 90 but enough for 61-75. Maybe if you drill outlet larger this will work OK. The muffler they sold you is for the G90 if it is this ST# http://www2.towerhobbies.com/cgi-bin...?&I=LXFV93&P=7

Ernie Misner

I've been told more than once that the G90 does not like backpressure much. You will know if it tends to run hot. It is strange though that the stock muffler is the same one as for the .61. I don't think Mac's makes the black one piece muffler for the G90. They do make a header pipe for it though, and it uses a larger tubing size than the 61/76 header pipe. Their tests showed that the G90 needed a larger pipe.

I am going to run the Mac's header and a mousse can muffler on my G90.

Ernie

HaveBlue

you could get a Jett stream muffler from jett engineering ..they a damn good muffler

Ernie Misner

The G90 is more of a torque than revving engine I think. It would be ineresting to see what the Jett or Ultra Thrust muffler would do though.

Ernie

Kweasel

My Feedback: (29)

The Macs muffler won't work very good on a 90. They work OK on 60s and provide lots of tank pressure, so much that it will run too rich through the midrange. A free flowing muffler is ideal.

Aeronau-tech

The Macs one piece muffler has a tube that is apx .590" OD. and 4.100" long. There is restrictor at each end of the pipe that is .277 ID. Does any body with experience in tuned pipes have an Idea? I could drill out the pipe and possibly install a piece of half inch OD.
and tig weld it in place. Any Thoughts?

buzzingb

My Feedback: (2)

What rpm does this engine like to run in? I have looked at this engine before but after running a 2300 gave the idea up. I like my engines to run in high rpms but sound like this is a torquer.

Ernie Misner

The mac's muffler is going to get really loud if you drill it out a lot. They are pretty much straight through, not much of a muffler. Try it the way it is and then open it up a drill size or two if necessary. Or you can run the stock muffler with the internal baffle removed and the exit drilled out a bit. I haven't tached my G90 yet, but most guys are getting about 10,500 with a 13 or 14x6 I believe. Write to Bax in the SuperTigre forum if you want. Run a search here on RCU. There is tons of info on the G90. Also, go to the SuperTigre web page and there is a test of the G90 there with lots of info. Let me know if you can't find the test.

Ernie