Gas engine tuning for newbies....

[JoeAirPort]

	Quote: Originally Posted by mogley
	what should a properly tuned da50 turn with a 22x8 menz on a slim line mufffler? same question with a Mejlik 23x8 all at sealevel? thanks

I can only tell you about my DA-50 on my Menz 22x8. 7000-7200 RPM depending on which carb I had on it. I bought a replacement carb from DA to try and fix a dead stick issue. The new carb dropped my peak RPM by 200-300 RPM. No idea why, no matter what I did to the high speed tuning it would not exceed 7000 RPM. I returned the carb to DA for credit and sold the engine with the old carb on it. When DA tested it on a plane with the old carb they said it had more power than their engine that was on the plane before mine.

[rcmergler]

just one quick question for the experts, went i start my cold da it will not advance without dieing until its at operating temp, once there its killer! so does that mean my low end needs to richen just a bit?

[Al Lewis]

It means let your engine warm up.

[3ddd]

it means do not lean it out any more,if it were mine i would go rich just about a 1/16th of a turn.on all mine i like to hear just a hint of burbble at about 1/4 to 1/2 throttle

[mtnflyer14]

This thread has really helped me understand the Walbro carb, tuning, etc--thanks to all those with expertise! And, I have a question: I have an older G-38 with electronic ignition, but it has the old WTA-6A carburetor. I would like to replace it with a new carb to improve performance since I fly in Colorado Springs at greater than 6,000 feet altitude. Does anyone know if the Walbro WT-540 would be a good replacement choice? Thanks in advance.

[RV4JMMD]

Ok, heres my problem.
Setup:
75cc Aeroworks 260, ZDZ Super 80, Walbro WJ-71, Klotz 40:1, Elevation is >6000'
Menz 26X8
Top rpm is 6450
Transition is smooth but idles at 2000, it might be a little rich too. When ran at full throttle and then chopped it goes SO low it almost dies and slowly pops back up to 2000. If I lean it out enough it will not die when the throttle is chopped but then the mid range is a little rich. I tried to set up a throttle-needle mix with a servo on the low needle but that didn't seem to make a bit of differenc in performance nor could I get the idle below 18 or 1900. I havent tried a bell mouth stack. ?????????????????????????????????????????????????? ???????
The best that I can get it seems to still be a little rich midrange. I might just have to live with that. Everyones gassers up here are run RICH and I know thats not how they are supposed to run, does anyone have a video of what they should sound like??? preferably in the midrange. My top end is awesome, sounds like a Mooney but the middle is popping more than I like to hear but I would like to compare it to someone elses midrange.
Thanks.

[Pro1Foam]

Bump a good thread

[stommerd27]

	Quote: Originally Posted by RV4JMMD
	Ok, heres my problem. Setup: 75cc Aeroworks 260, ZDZ Super 80, Walbro WJ-71, Klotz 40:1, Elevation is >6000' Menz 26X8 Top rpm is 6450 Transition is smooth but idles at 2000, it might be a little rich too. When ran at full throttle and then chopped it goes SO low it almost dies and slowly pops back up to 2000. If I lean it out enough it will not die when the throttle is chopped but then the mid range is a little rich. I tried to set up a throttle-needle mix with a servo on the low needle but that didn't seem to make a bit of differenc in performance nor could I get the idle below 18 or 1900. I havent tried a bell mouth stack. ?????????????????????????????????????????????????? ??????? The best that I can get it seems to still be a little rich midrange. I might just have to live with that. Everyones gassers up here are run RICH and I know thats not how they are supposed to run, does anyone have a video of what they should sound like??? preferably in the midrange. My top end is awesome, sounds like a Mooney but the middle is popping more than I like to hear but I would like to compare it to someone elses midrange. Thanks.

Sounds to me like you are still rich on the bottom. As you lean the bottom you may need to richen the top. Sometimes it takes many run ups on the ground to get close and then some fine tuning after each flight. Take your time and get it right once good you will be suprised.
Shane

[mfuess]

	Quote: Originally Posted by RV4JMMD
	Ok, heres my problem. Setup: 75cc Aeroworks 260, ZDZ Super 80, Walbro WJ-71, Klotz 40:1, Elevation is >6000' Menz 26X8 Top rpm is 6450 Transition is smooth but idles at 2000, it might be a little rich too. When ran at full throttle and then chopped it goes SO low it almost dies and slowly pops back up to 2000. If I lean it out enough it will not die when the throttle is chopped but then the mid range is a little rich. I tried to set up a throttle-needle mix with a servo on the low needle but that didn't seem to make a bit of differenc in performance nor could I get the idle below 18 or 1900. I havent tried a bell mouth stack. ?????????????????????????????????????????????????? ??????? The best that I can get it seems to still be a little rich midrange. I might just have to live with that. Everyones gassers up here are run RICH and I know thats not how they are supposed to run, does anyone have a video of what they should sound like??? preferably in the midrange. My top end is awesome, sounds like a Mooney but the middle is popping more than I like to hear but I would like to compare it to someone elses midrange. Thanks.

You have a small air leak somewhere... probably at the carb base. Find it, fix it, tune it, and your mid-range & idle with be correct.

[nguyencuongaa]

It's important to understand that there is a reputation for glow-engines to be difficult to tune. This is a common error in thinking. With a little bit of know-how, tuning a glow engine can really be a simple, pain-free process. People that don't properly understand the basics can easily become frustrated by what should be a simple, straightforward process. Here's how you do it:
Dialing it In
For the purpose of this tutorial we are going to make some basic assumptions. First, we're going to assume that the rest of your car or truck is properly functioning and that you have everything ready to go. Second, we're going to assume that you are able to start your engine and that it at least runs for a second or so.
The first place to start with dialing in your engine is to make sure that you have your idle-speed properly adjusted. Your engine manual should give you specific instructions on setting the aperture gap to the minimum size. It's important that we get this resolved before continuing on. If your engine can't get enough air/gas flow then it won't start/run. A clockwise rotation opens the aperture and increases the idle RPMs, a counterclockwise slows it down.
Second, you should tune the low-end mixture valve. This is done before the high-end (main needle) adjustment because an improperly adjusted low-end can affect the high-end performance. Like most mixture valves, clockwise rotation will "lean" the mixture and a counterclockwise will "richen" the mixture.
To determine whether the low-end mixture requires tuning, allow the engine to warm up completely, and then allow it to idle, uninterrupted for one full minute. If the engine continues to run after the minute is up then your low-end mixture is correct and you're ready for the high-end adjustment. If it dies on you then there are two possibilities; either you are running too rich or too lean. To determine which is the case you must listen for how the engine dies in its idle test.
If the engine's RPM's rev up at the last second and then the engine dies than you are running too lean. To correct this, turn the low-end mixture screw counterclockwise (out) 1/8 of a turn (always make adjustments in 1/8 turn) and retry the idle test.
If, on the other hand, it begins to wind down and you notice a change in how the exhaust sounds in the last few seconds, then your engine is running too rich. To correct this, turn the low-end mixture screw clockwise (in) 1/8 of a turn and then retry the idle test.
Once you have passed the idle test and are able to idle for one full minute (after first warming the engine up, of course) you are ready to continue on. You may have to repeat the above process a few times until it is properly set. Remember, only adjust the screw 1/8 of a turn. It's far too easy to go too far with the adjustment. Setting changes don't always take effect immediately. You may have to run your engine for a few minutes for the full effect to take place.
Now that you have dialed in your low end, any carb mixture problems can be isolated to the high-end (main) mixture adjustment.
Acceleration is the tell-tale sign of how to tune your high end. If you hit the throttle and it takes off suddenly but then suddenly dies or loses power then you have your main mixture set too lean. Try backing (counterclockwise) the main mixture needle out 1/8 of a turn and retry. If it bogs immediately when you hit the throttle (sounds like it's choking), then it's most likely running too rich. Try leaning the mixture out by screwing the main mixture valve in (clockwise) 1/8 of a turn.The more accurate way of really dialing in the top-end is to take the engine's temperature. A properly tuned engine should run between 210° and 220° Fahrenheit. This can only really be ascertained by using and infra-red thermometer such as the type used by automotive mechanics. On-board or direct-transfer types that measure the heat from the head are inaccurate because, assuming the head is properly dissipating heat, it would reflect a lower than accurate temperature as a majority of the heat energy would be dissipated from the exposed surface of the head. By "looking" at the temperature near the core (actually, area immediately surrounding the glow plug) the temperature can be more accurately read.
The cheap but easy alternative would be to drop a bead of water down the head on the glow-plug and see whether it boils off. If it slowly simmers than it probably is running right around 212°. If it boils to quickly then it's probably too lean and needs to be richened. If it just sits there and doesn't boil at all, then its running too rich and needs to be leaned out.
An engine that is running too lean will run hotter and exceed the 220° degree limit. This can significantly reduce the life of your engine. Although it may be tempting to run your engine as lean as possible (does give a short-lived performance boost), this should only be done if you are very wealthy and like swapping engines out every race. There is no quicker way to kill and engine, honest. This is simply because as you lean the engine out, it gets less fuel to the engine, and more importantly, less lubricant. Since glow fuel is the only means of lubrication for your engine, the lack of it means certain death to your powerplant.

copy from this site

[brownstripeyshirt]

Sorry mate, you've lost me how that relates to gas engine tuning...

[Pro1Foam]

ttt