chris de jon

Good Day,
I have a problem with my Magnum 180 FS. It has around 50 flights and I use 17% synth + 2% castor. No nitro. I use on board glow up to 1/3 throttle.

I am using a Master 16 x 8.

The max revs I can get are 7800 on the ground before it leans and dies. The HS needle is about 1.25 turns out.
When tuning I noticed that pressing in on the needle increased revs. I have wrapped the threads on the needle with teflon and placed some fuel tube over the needle at the inlet junction.
Pressing the needle now does not change the revs.
The LS needle is about 3 turns out and with the pinch test speeds up at idle.
The transition is good from low to max (the 7800 revs).
Blowing into the fuel tank inlet tubing while blocking the muffler pressure tubing would indicate no air leaks.

I have checked the valves and they are ok.
Compression is good.
The HS needle is level with the fuel tank stopper.
Could some one please help me to obtain more revs.
Cheers
CDJ

asmund

I have removed both headshims, reset the valve gaps and drilled the outlet of the muffler to 9mm and added a velocitystack to the carb. All these mods will release more power. Also this engine really loves nitro and will respond really well if you feed it some 15%.
Se my post regarding my ASP 180 fs

liquid_TR

16x8 Prop on a 180 4 stroke??

first, put a bigger load on the engine.
second, try some nitro! At least 5% nitro in the mix, or even better, 10% nitro would get you very nice running characteristics with higher top end.

Flyboy Dave

My Feedback: (21)

....I had to remove a head shim from my 1.20 Magnum because it had
low comprssion from new. I also raised the nitro level to 20%, and the
engine came to life. I picked up about 1500 RPM....

....it made a huge difference. [sm=teeth_smile.gif]

Dropping down in pitch on the prop will increase revs as well.

FBD.

Edwin

My Feedback: (2)

Is this engine a recent installation or has it always been in the airframe. I had this exact problem awhile back on a zero with a saito 180. My problem turned out to be too much head pressure. With a 24oz tank sitting about 1" too high I could only get to half throttle before it would die. Changed the tank to a 15oz, same engine, ran fine through the entire throttle range. But a 180 with a 15oz tank is a pretty short flight so I swapped the 180 with a 120. Thats what it flys with now. Tank placement was pretty much fixed, couldnt lower it or move it anyplace else.
Edwin

Flyer95

My Feedback: (1)

Which Master prop are you running? They have standard master nylon, master classic and wooden props. The classic turns higher rpm and the wooden turns lower with the standard ones somewhere in between.
It seems like your engine is about 1000rpm short of average numbers that I have seen in review and tach.readings for that engine.
On a Saito180 I usually run APC 18x6w/17x8/ or MenzS 18x6 and they all give about 8500rpm +- 200rpm depending on the prop. and weather conditions. My homebrew fuel is 10% nitro "recommended" and 20% oil 50/50 castor/syntetic mix. Been running many gallons of this fuel for a few years now in all my fourstrokes and no engine cleaning have been needed.

chris de jon

Hi and thank you for responding.
I did not reply sooner as I had more testing to do.
Asmund:
Your 180fs figures are very impressive.
You said no Nitro gave you 8100 on 18x6 and a Volk 17x4 at 8800
As mentioned in my post I am only able to get 7800 to 8100 on a 16x8 It is a Master Classic with no nitro.
I ran a Volk 17x4 and got no improvement at all.
Could you please let me know the basics of your setup. So that I may compare.

Tank size I have changed from a 20 Oz to a 16 oz in case draw was a problem, and also had no improvement
Fuel I am running 16% cool power and 2% castor
How many turns of the main needle is your motor
My main needle is just over 1 turn out
My LS needle is about 3 turns out.

I have reset the tappets and checked them many times .102mm is tight .
I have now replaced all the O rings in the needle and manifold.

I have blown out the jets with a syringe
A new F series plug did not change anything.
I mixed a new batch of fuel and that also has not altered anything

As mentioned I do not run Nitro as it is hard to get here.

I was under the impression that nitro only improved transition and idle. These are both pretty good. It is top end I am after. Does nitro improve top end?

This is not a new installation it has about 50 flights now and was fine until a week ago when it just sagged off. My model likes the 16x8 and flies well at about 8500 so that 600 or so that I have lost really makes a difference.

I am coming to the opinion that maybe the tolerances on my motor are not as good as yours as nothing seems to improve it.

I would love to know what has caused the change and any more input to try to improve the engine performance would really be appreciated.
Cheers
C de J

liquid_TR

Of course nitro gives higher power output, when the compression ratio is compensated for..

The side effects are easier to tune engine, much better idle and faster throttle response.

why do you think boat racers use 40 - 60% nitro in their fuels? not for transition

Flyer95

My Feedback: (1)

If your engine used to do 8500rpm on a 16x8 and now only does 7800 on the same prop. then something has happened with it. 8500 on a MA-classic 16x8 is not bad but 7800 is low and makes me think maybe this one is simply worned out or have burned valve seats and leaking valves ? or fuel draw problems? Does it have good compression when turned over by hand? I think ASP recommends a good amount of castor oil in the fuel for these engines.

martenson

Might even be worn or damaged valvesprings, does it sound as it used to?
Pistonring, valve seat, valvesprings this is just some of the thing to check.

Good Luck

Edwin

My Feedback: (2)

Sounds like time for a tear down. I would look for a bunch of carbon buildup around the valve seat and on the valve stem. Carbon cleaning is a high time maintenance proceedure for me. But, I dont think that would produce the kind of symptom you're seeing and 50 flights (or so) shouldnt build up that much carbon. Just my opinion.
Edwin

Sport_Pilot

Top fuel dragsters do a quarter mile in less than 5 seconds and 300 MPH. Yeah boy, does nitro improve top end!

Sport_Pilot

Another thought, take off the intake manifold and check if it did not suck in some debris. I recall someone finding an insect in there at one time.

martenson

A topfuel engine on methanol gives circa 3500hp and on nitro over 8000hp.
I know, I'm working on one now

Edwin

My Feedback: (2)

And another thing, I keep a can of carb fixit in a can (wd-40). Sometimes crud gets through the fuel line and jams up in the needle valve area. It doesnt take much. Pull the needle valve out and spray wd-40 through the carb. I'm pulling straws here. Either way, I would do a tear down anyway just to check out overall condition.
Edwin

asmund

Hi, sorry for my late reply[sm=red_smile.gif] My engine is mounted sideways with the cylinder to the right (from behind the plane) I use a relatively small tank, I think it is 15 oz. To improve power I have removed BOTH headshims (reset the valve gaps) and drilled the exhaust outlet to 9mm . I don`t know what my main needle is at, I just tune it for peak rpm and then back off a little, the LS needle is set for crisp transition and good idle.
This engine really loves nitro and 15% is recommended if you can get it. Nitro makes the engine stronger on top as well as improves idle and transition. The removal of both headshims will make your engine produce more power with both 0% and 15% nitro fuels.

Try the mods I have mentioned here and then report back your tach readings.

I tached my engine yesterday on a blend of equal amounts of 15% fuel and 0% fuel, giving something like 7-8% nitro and I still got 9000 rpm on MenzS 18-6, but a Volk 18-6 dropped to 8100 rpm.
I have seen many times before that the Volk props are alot harder to turn than other brands, so low numbers are to be expected on Volk`s