anybody have any tach readings on a ST 90 ringed engine?

Today I saw a review on the G90 in a few years old magazine RCM&E.
APC 13x6@11900
APC14x6@10300
APC15x6@9200
APC16x8@7300

Numbers are on the stock muffler and 0% nitro 18% halfsyntetic oil.

Hope it help a little

IMO a 16X8 is way to big for a ST90. I think even a 15X6 is pushing it.

I run a 14X6 MA on mine and get 10300 as well on 5%

I would try maybe a 15X4 or 14X8 but nothing bigger

I run my ST G90 on home brew 5% nitro, 20% castor, the second tank .. very rich she turns a MA 12 X 8 scimitar at 12,400... tried to tach her a few days ago with my new TNC... but that turned out to be a non event... first time ever I had fuel streaming out of the carb...

It is mounted to a f90 and it is great. I have a few cases of heli fuel so it drinks 30%.
Zinger 14x4=11,700
Pro Zinger 15x4=10,500
APC 16x4=10,000
Slimline pitts had the stacks removed in a landing gear stress test I belive the motor needs more back pressure, When one hole was pluged I gained over 200rpm with the 15x4.

I have her mounted on a H9 P-47 and I've run only about 3/4 gallon through her so far. I'm running a 13x6 MA prop with 15% nitro/18%castor-synth blend. It has a slimline pitts muffler with one exhaust pipe crimped shut. I have the low end idling between 2500 and 2700. At full throttle I am getting around 11150 to 11200 rpm. I live in Central Florida so we're pretty close to sea level and the atmosphere here is HOT and STICKY.

I also ran a 14x6 MA prop, but I cut the nitro to 10%, and am getting around 10500 . I've been thinking about going to a 15x6, do you think that would be too much prop? I'm interested in more vertical pull than top speed.

Dave

I've been experimenting with a well run ST G90 and found some interesting results.

Fuel: Powermaster 10%
Prop: APC 14x4w

Stock configuration: rpm: 10,500

Swap carb to Magnum 91/108 rpm: 11,500
Swap stock muffler to Ultrathrust rpm: 12,500

Magnum carb = $37.00
Ultrathrust muffler = $74.00

Bottom line: The carb swap is a no-brainer ... for $37.00 add 1,000 rpm
The muffler is a little expensive but adds another 1,000 rpm over stock. If you have an old ST G90 laying around, give it a try. Transition is great with the Magnum carb. Power with both mods is awesome... and it sounds like a high performance dirt bike!

I am going to flight test the modified ST in my Aeroworks Edge 540T 40/60 tomorrow. AUW is 6lbs.

Flight Report #1:
Engine would not run consistantly. I believe the problem was too much boost/heat using the Ultrathrust muffler. The bench runs were great with that combo, however, it was a totally different story in the plane. By the way, I switched to a Magnum 91/108 carb which has proven to work very well in the G90.

Back to the Bench:

I removed the Ultrathrust muffler and installed my OLD Jtec manifold with dual pipes. The result was a loss of 400 rpm and lower head temp. I also found that the McCoy 4 stroke plug seems to improve low-end performance. Max rpm with APC 14x4w is now 12,100

Flight Report #2:

Success! Maiden flight went very well. The modified ST G90 performed flawlessly. I was getting 12,100 rpm with a APC 14x4w which provided truly unlimited vertical. Most flying was done at 1/2 to 3/4 throttle. KE flight was extremely neutral. I didn't notice any tendency to pitch in KE flight. Upright flat spin was good but inverted was better. I have not tried 3D yet, however, the modified G90 has great thrust and throttle response. I had to cut the flying session short due to weather conditions. I'll post more as I get more flying time on the Edge.

I recently upgraded to a Jett muffler and saw a boost to 10,800 on a 14X6MA

With a 13X6 APC I am getting around 11,200

I was really hoping to get a bigger boost with an $80 investment in a muffler.

Still running 5%

Gringo Flyer,
Are you running this engine in the correct rpm range for this tuned muffler?

I was told that I would get my best performance between 11 to 12K

I was hoping to get there on a 14X6

Just curious. How are you runing an ST 90 on 30%. Did you modify the head shim to avoid detonation or overheating.

Hi All,

I have a question for everyone on the post. I have a new G90 that runs like a top. It's still not broken in yet so I expect at least a 200 RPM increase on a 13x6 from 11000 to 11200 with 11500 peak.

I don't know how the mag article got 11900 on a 13x6 stock. That seems way out there.

Anyways, here is the question. A Magnum 91 FS for 150.00 (on sale) will turn a 14x6 at 9800 on 15%. You can prop the G90 with a 14x6 and get 10300 or so. Is the G90 really worth it. Why not just get a cheap 4 stroke if you want to run a 14x6 since 10300 is probably overloading the G90 anyways?

This is the question I am asking myself anyways.

Gringo Flyer,

Any heat issues with the 14x6? I was wondering since they recommend running the motor around 12k.

The ST90 will not overheat if you use big props. It has bigger cooling head than most 90-sized engines. I run APC 16x8 @8400rpm on mine and use a quiet pipe to get the best performance at that rpm. I did not use the stock muffler more than i few tanks so I dont remember if it would overheat the engine on the oversized props?.

I have a couple G90's. They were Italian made before the factory shut down. Had them close to six years.

They both came with the Super Tiger 40,46, & 51 carb. One of them has about a gallon and a half through it.

15% Rich's brew fuel, mid 30's temp, 1,000 ft elevation, APC 14-6
W/ the 40,45,51 round sided spray bar carb 10,000 rpm
W/ the 61,75,90 carb spray bar installed in the carb body -- 10,500
W/ the ASP old style 91/108 carb 11,000

I ran a 15-8 on it some but don't remember the rpm but I think was around 8400. The engine didn't over heat but had a slow spool up.

Dave Gierke from Model Airplane News contends that their toque peak is below 8,000 and you should run a big prop like the 15-8.

I like the MAS and APC 14-6 on them myself

I tried the 13x6 and 14x4 zingers today and I think I liked the 14x4 better. The 13x6 seemed to have less thrust and definitely more speed but I really don't need the speed with an Edge 540. I'm going to try a 14x5 and 6 to see what I like the best. I will probably try out the ASP carb upgrade soon just to see what the extra power is like.

Horizon no longer lists the ASP AR91/108 carb for some reason. May have to try Hobby people or Just Engines?

Hobby People's URL

http://www.hobbypeople.net/gallery/280005.asp

This carb has a spring steel sleeve inside so it can be used on the old style Magnum XL91. The sleeve is easily removed if you so desire. I left mine in the carb.

But, you are saying that it will fit the new G90 as well. I wonder if they are all the same size as OS?

Yes, the Magnum 108 carb fits the Super Tiger G90 like it was made for the G90.

The OS 7D will also work but they are so expensive that they are not cost effective.

I'm going to call peak rc tomorrow and see if they have the Sayne 108 carb. I'm hoping it will be even cheaper. Sayne is the maker of Magnum and I think the Magnum and Sayne motors are dups.

Right now, I've got my G90 set up so it transitions perfectly. I hope the Magnum carb transitions as well. The extra 1000 RPM will be great though.

Do you have any idea why there is such a big increase in RPM with the Magnum carb? I wonder if it is just a question of throughput.

The ASP/Magnum/SC/Sanye 108 carb has a very large bore.

Anyone have a tach reading with a 15x6 on the ASP carb?

The Magnum 108 carb has a 11.5mm bore.

With the old style Magnum 91 spring steel bushing, it has a 9.5mm bore

The bore on the Super Tiger carb is 8.75mm but it has a flat sided narrow spray bar that makes it effectively larger.

If your Super Tiger 90 has a round sided spray bar, it is the carb for the 40, 45, 51 engines.

The only difference in the big and small Super Tiger carbs is the spray bar.

Well, I went with the 15x6 APC and am happy for it. My H9 P-47 has more vertical, sounds better (not screaming anymore), and actually slows down enough to land the danged thing without nosing it over. I tached it today and at full throttle and still running fairly rich I'm getting 9100. She's idling around 2100 and purrs like a kitten. I use 10% nitro with an 18% Synth/castro oil mix.

Dave

I tried the Magnum carb and the results are good. I got at least 700 more RPM maybe more. The transition is great. The only problem I am having is cooling with the really tight cowl I have. I don't think there is much I can do about the cooling so I may sell the carb. If anyone is interested I may make a pretty good deal. The Magnum carb only has a few flights on it.