Gas engine tuning for newbies....

[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

[ivanflight]

why dont these companies hire some gurus and design a fuel injector for these engines and get rid of the carb !!!
now that would be nice!

[Tired Old Man]

I have to chuckle a bit about that one.

That's already been done but unless you're wealthy you couldn't afford it on the open market.

[stommerd27]

Not to mention the computer and wiring involved to run true electronic fuel injection would add weight and a lot of confusion also. A simple injection set up would be the pill system but then you really only have idle and wide open throttle. They might get there some day though and design a simple cost effective electronic injection system.

[hovhas]

shouldnt be that hard.

[Al Lewis]

	Quote: Originally Posted by hovhas
	shouldnt be that hard.

Not hard, just very expensive.

[bodofish]

Walbro sells off the shelf EI kits for small motors. How's that for plug and play? Pony up the $1200 and bolt it on.......

[Tired Old Man]

People seem to think all they need to do is bolt on a couple of injectors and they're off and running. Wish it was that simple. It's not something you want to do if you're trying to keep the weight and complexity down as well. Every engine size and type is different form another so each engine would require it's own injection design. Next part, what would you need for an electrical system to drive an EFI unit? There would have to be pumps and ultra fine filters, filters dense enough to drive up pump head pressure, regulators, etc, that would need a constant power supply. people complain about battery weight now. Imagine how upset they would be when adding a 6,000 mA 4s battery to power just the EFI, and recharging after every couple flights. The turbine folks already know about maintaining a serious fueling system. Us plankers don't have a clue.

BTW, to do it right is hard, and very expensive. Throwing money at a "non issue" has never solved a problem that wasn't there to begin with. Even if someone came out with a commercially available EFI system for our size engines the price would not be low enough for justification. The quantity of gas engines flying toy airplanes is not enough to perform production runs in quantities high enough to absorb the R&D costs and turn a profit. Plus, if you're flying at altitudes below 10,000' there's no real benefit to having EFI. Your carb self compensates well enough at altitudes below that to function effectively within good performance levels. I seriously doubt you would see any rpm gains between a carb and EFI with our engines at the usual altitudes they are operated at.

You just need to know how to tune a carb.... Judging by the engine break in thread, most don't. Our carbs are very simple devices and don't require a whole lot of smarts to deal with. Unfortunately there is plenty of evidence suggesting our carbs are much smarter than the people using them:7aa:

[bodofish]

Just in case you thought I was blowing smoke. This is straight from Walbros web site. There is more to it than just bolting it on but, it is EFI and it's off the shelf, they also carry the fuel pumps that run off the crank pressure just like the carbs do. Now software and an interface to to adjust the MAP may be another story. It's still not beyond the relm of possibilities.
I DON'T BELIEVE I SAID ANYTHING ABOUT BOLT IT ON AND IT'S THAT SIMPLE. Well maybe I did.... My bad.
Not many "off the shelf" anything units are plug and play for anything. And yes I have modified a number of EFI units and it is not an easy task. If it was easy they'd be installed on everyones engines!
The point is and always has been they are available for anyone that would like to put in the time and enegry.

Application: Two or Four-Stroke EFI w/Integrated ECU


Features:

• Single throttle bore
• Aluminum alloy
• Integrated engine control unit (ECU)
• Inlet air temperature sensor
• Barometric pressure sensor
• Throttle position sensor
• Reduced pin connector
• Redundant throttle spring
• Adjustable air (idle) settings
• Fuel injector
• Fuel rail Shock & vibration isolation

Options:

• Diagnostic valve
• Corrosion protection
• Carbon canister purge
• Shaft bearing type
• Mounting flange design
• Air cleaner connection
• Tamper proof adjustments

Not available for on-line purchase

[Tired Old Man]

Believe me when I say I know absolutely that you are not blowing smoke, however, just where does it inject the fuel? You might find that's rather important once you get to running it.

Bolt on is good, but might not work as well as you might prefer. The concept of EFI for our small engines is definately not beyond the realm of possibility, just fiscally impractical for the moment.

Quit laughing Al