High EGT's

33 posts in this topic

Posted

I was having high EGT issues on my initial run from 5000 rpm to 6800 rpm. It was not critical temps (1150) but higher than I wanted to make the initial flight test with. I decided to recheck the jets and order the next size. When I checked the correction chart it said I should have 160 jets for my altitude. I did not remember ordering that size originally so I check my receipt and sure enough I had ordered and installed 155's. It took me awhile to figure out that I had calculated the altitude in meters instead of feet. This is the 4th set of main jets I have bought for a Rotax and have never done that before. Needless to say a new set is on the was from Aircraft Spruce.  Flight test soon. 

Share this post


Link to post
Share on other sites

Posted

Post some pics of that puppy when ya get the graphics on!

Share this post


Link to post
Share on other sites

Posted

I got new jets in and was still running 1200 degrees at WOT. I ended up changing back to the 165 jets to get the temperatures in the 1100 range. Why I’m running sea level jets at 2200 feet above sea level I’ll never know. My mid range was also running a bit high  so I lowered the e clip a notch and now everything looks good. It’s running about 1050 degrees in the mid range.  A few more things to take care of and I’ll be ready for a test flight. :)

Share this post


Link to post
Share on other sites

Posted

Don't remember if this was discussed, but on a two stroke, running more pitch in the prop will lower the EGTs as well.  Need to have a load on the engine.  What is your static full throttle RPM?  JImChuk

Share this post


Link to post
Share on other sites

Posted

6250

Share this post


Link to post
Share on other sites

Posted

I am at 6100 static which goes to about 6600 full power on climb.  Might also be worth a tach double check.  I was running a Rotax tach early on and had similar issues. it was reading approx 300 RPM higher (compared to a Tiny Tach).  Ultimately it was a combination of my EGT gauge being off scale high (it was an older analog Westach system) and the went to a temp compensated MGL and no more issues.  Plug color is also key.

I also added a fuel/air sensor in the exhaust that confirmed I was way rich just as an added measure.

 So scrutiny of both sensors and your plug color may help here.

Share this post


Link to post
Share on other sites

Posted

LSaupe, I have two brand new rpm gauges. One is a UMA and the other is a Tiny Tach. They are reading the same rpm. The Westach EGT could be an issue beings that both of the other Westach products I had were replaced for not being accurate. I've re-jetted four Rotax engines and never had this issue. The conversion charts normally put you right were you need to be. I'm running 165 jets in this engine to get the temperatures were they need to be. 165 are the jets they call for at sea level and I'm at 2200 feet. THe chart calls for 160's. I also wonder if this could be a plugged up exhaust. Between the mud dobbers and the 2 stroke oil that was caked to the bottom of the plane this could be a possibility. I'll try another EGT, see what it says and go from there. 

Thank you

Vance 

Share this post


Link to post
Share on other sites

Posted

Damn I had a egt gauge sitting and got rid of it when I sent you the little tach . 

Share this post


Link to post
Share on other sites

Posted

Static tests are pretty much useless for determining what in-flight EGT's will be. Too many variables from diameter to blade profile to make static tests worth much. You will spend an eternity trying to figure things out that way. 

1200 is not a bad temp. it's actually optimal for most power and cleanest engine between tear downs. I would suggest leaving the stock 160's in and putting a bit more bite in the prop, enough to be confident you can get off the ground and fly around a bit without without the engine being bogged down too much. The steeper pitch in the prop will significantly reduce your EGTs. Then you can use test flights to change prop pitch till you get EGTs you are personally comfortable with and limit mid range volatility, which is really where in my opinion most of the danger of engine seizure exist.

To me static testing is only good to find out if the plane will fly without either bogging down or WAY over-revving. Everything else should be done by flying and adjusting. More bite in the prop as long as you can get enough revs to take off and actually take stock of how it does in flight, will keep you from burning up the engine from no load.

Did that make sense?

 

ChrisB

2 people like this

Share this post


Link to post
Share on other sites

Posted

When my electric Ivo died I took off at cruise pitch and it was only turning about 5800 on takeoff. Flew fine just didn’t climb like normal. 

Share this post


Link to post
Share on other sites

Posted

I'm set around 6100 on take off and get great overall performance. Previous owner had it pitched to climb and it sucked at cruise . 

Share this post


Link to post
Share on other sites

Posted

Static tests are pretty much useless for determining what in-flight EGT's will be. Too many variables from diameter to blade profile to make static tests worth much. You will spend an eternity trying to figure things out that way. 

1200 is not a bad temp. it's actually optimal for most power and cleanest engine between tear downs. I would suggest leaving the stock 160's in and putting a bit more bite in the prop, enough to be confident you can get off the ground and fly around a bit without without the engine being bogged down too much. The steeper pitch in the prop will significantly reduce your EGTs. Then you can use test flights to change prop pitch till you get EGTs you are personally comfortable with and limit mid range volatility, which is really where in my opinion most of the danger of engine seizure exist.

To me static testing is only good to find out if the plane will fly without either bogging down or WAY over-revving. Everything else should be done by flying and adjusting. More bite in the prop as long as you can get enough revs to take off and actually take stock of how it does in flight, will keep you from burning up the engine from no load.

Did that make sense?

 

ChrisB

You bring up some good points Chris. After resetting my needle position my engine temps are way down. I'm starting to think my biggest problem was in the mid range circuit. Now that it looks good I should be able to reinstall the 160's. I will run it again with the 160's and add a bit more pitch. I hope to fly this next weekend. 

 

1 person likes this

Share this post


Link to post
Share on other sites

Posted (edited)

Update: I took the Avid out for some testing this weekend. Initiate flight showed high EGT's again. Jet change didn't help. Plugs and EGT's show good colors. Ran it by Joey and he mentioned the possibility of improper sender placement. He sent me an article on the subject and a check showed that my EGT senders were just under two inches off from there intended location. The book calls for the probe to be 1 5/8 inches out from the face of the exhaust flange. My probes are currently placed 3.5 inches from the face of the exhaust flange.

I also found a leak in one of my radiators. Looks like I will have to pull them off and have them fixed and tested. Something was buzzing/vibration really loud. I need a seat cushion.

All in all the plane felt good in flight. Climbs like a home sick angel.  I still have a few things to check and adjust but all in all it was a good test flight. 

Pictures to be posted soon.

Vance

Edited by rvsimons
1 person likes this

Share this post


Link to post
Share on other sites

Posted

Remember to check that rpm on climb . All my temps were high because it was pitched for climb and it made it run higher rpms for everything resulting in higher temps. Not sure if I'm making any sense but that's what happened before I re pitched for cruise. 

Share this post


Link to post
Share on other sites

Posted

Flight two was better but still running to close to 1200 in the mid range. Idle good, WOT good, 5800 to 6100 a little high. When the engine is on the main jet the temps are good so it is with climbing. I contribute this to proper jetting and load. Temps climb in cruise when the nose is lowered and the engine unloads. I am going to try one more degree of pitch to see how it effects the high mid range. I can literally cool the engine just by starting a gentle climb. Climbing at 55 mph yealds 6400 rpm right now. More to come. 

 

 

Share this post


Link to post
Share on other sites

Posted

Still sounds like the needle range.  Do you have another needle slot to go?

1 person likes this

Share this post


Link to post
Share on other sites

Posted

No I'm bottomed out. The book said initial settings was to place the clip in slot three. I'm in slot four now. 

Share this post


Link to post
Share on other sites

Posted

Change the midrange needle or pitch it a bit more.  Thats the beauty of the IVO inflight.  Flatten for take off RPM then pitch it up in cruise and your golden. 

:BC:

 

Share this post


Link to post
Share on other sites

Posted

I need an IVO IFA. Do they still sell them. I don't see used for sale often. 

Share this post


Link to post
Share on other sites

Posted

Let an Bing expert shoot me down here, but I've raised needles a little extra by adding an extra nylon washer under the needle clip (in a Mikuni).

Share this post


Link to post
Share on other sites

Posted

Lol......I don't see why that wouldn't work. I've seen three engines with the needle installed on top of the white cup.

:lmao:

Share this post


Link to post
Share on other sites

Posted

After talking with a few guys about thier rpm at climb out I'm running a bit higher RPMs. I'll add a degree of pitch and see what happens. 

Share this post


Link to post
Share on other sites

Posted

After talking with a few guys about thier rpm at climb out I'm running a bit higher RPMs. I'll add a degree of pitch and see what happens. 

the biggest thing is how many RPM are you running flat and level WOT.  If your running a pretty high rpm flat and level then when you pull back on the power for cruise the EGTS are going to go up.  With a fixed pitch prop its a balancing act between take off and cruise performance. 

Remember, anytime you point the nose down hill pull the power WAY back.  If you let the prop start driving the engine in a descent your asking for a burn down.  Flying a 2 stroke has a bit of a learning curve.

It kind of sucks because if you look at the power curve on these max HP is at 6500 and max tq right around 6700.  It drops off pretty quick below 6500 on the HP so turning it too slow on take off and your making under 50 hp easy. 

The down side I have found on the IVO IFA is the damn electric motors don't seem to last as long as they should IMO and they are charging big bucks for a 20.00 motor.  I have a well known RC car engine builder making me a custom wound motor that I hope will provide better life and better all around service.  Hopefully I will know in another week or two.

:BC:

 

1 person likes this

Share this post


Link to post
Share on other sites

Posted

What I do is just pitch to get 6100-6200 on climb with my 582. That way I get great overall performance. My temps stay good and I get the best of both worlds. I was hoping to fly today and shoot some video of my dash during climb and cruise buuut my wife and I had our anniversary party / Halloween party last night and I'm way to tired to go out. Can't complain I've been with my wife for 11 years married 9 and have to of the best daughters you could ask for . Hopefully I'll go up this week and get some video of my dash during take off and cruise . 

3 people like this

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now