Author Topic: Fuel mileage. Why? (Read 1932 times)

FLOYD CARTER · « **on:** January 25, 2009, 02:17:24 PM »

It seems that modern engines tend to have terrible fuel mileage when new, and then get dramatically better after a gallon or more fuel. Why is this? I cannot detect any difference in friction or "drag" in the fit after the engine has been used for a long while.

Floyd

Alan Hahn · « **Reply #1 on:** January 25, 2009, 02:26:26 PM »

Floyd,
I have seen this on the Saito 4 strokes (30 and 40) and it is pretty dramatic.

My guess it is a combination of better seal of the combustion chamber, and yes, less friction after parts wear-in and get smoother. It may be difficult to feel the difference when hand-flipping, but when the engine is running, the rpm is so much higher that even a small improvement in friction adds up. Also I wonder that when the friction decreases, it allows us to lean the engine a bit with less of the combustion process being stolen by friction. The friction causes heating of the engine and the need for a richer mixture to keep the engine cool.

FLOYD CARTER · « **Reply #2 on:** January 25, 2009, 03:04:40 PM »

Alan. Yours is the logical answer. After all, nothing changes after a lot of running, except some reduced friction. I guess we just have to live with the problem. But at $20/gallon for fuel, and the time and bother of long bench running, I would rather get good mileage right away! The problem usually is a bother because flying with a new motor means you can't do the whole pattern unless the fuel tank is unnecessarily large, then you don't need the large tank when the motor gets broken in.

Floyd

Alan Hahn · « **Reply #3 on:** January 25, 2009, 04:19:17 PM »

Floyd,
Well all I can say to that is patience! But I know what you mean. All I can say is to have a practice tug (especially a profile where it is easy to change tanks) where you can fly with a bigger tank and break in the engine in the air. At least you get some practice, even if the new plane does not. Another thing I do is if I am playing with a new setup and am not sure how much time I have, I leave out level laps---especially during the beginning after takeoff and the inverted flight. Also short a lap between easy maneuvers. Then at least you get to fly the entire pattern in relative safety.

Nothing is more disheartening as to see the engine burp and go quiet as you pull out of the 4th loop of the clover--especially with a new plane

Greg L Bahrman · « **Reply #4 on:** January 25, 2009, 05:22:53 PM »

Floyd,
I use 4 strokes on my RC ships and it takes a minimum of 1 gallon and sometimes more to reach the point where the motor will idle reliably and respond to immediate throttle input. For me it's not safe to fly the plane until the engine is broken in with a reliable idle. 4 strokes have a lot of moving parts that need to wear in properly before they will make their potential power output, start quickly, respond to throttle changes and idle. As the breakin time increases so does the mileage. The secret with 4 strokes is patience, patience, patience. Put thru their paces before this and you will have an engine that will throw props, backfire, and generally run hot, start hard and quit at the most inopportune time. I don't run them at full throttle until I have at least 1/2 gallon of fuel thru them....Patience

Russell Shaffer · « **Reply #5 on:** January 26, 2009, 09:44:42 AM »

A question - would it be feasable to run in a new engine on a drill press? Maybe remove the glow plug and keep it well oiled and just chuck the crankshaft in the drill press. Might not work for the cylinder/piston but you could remove the piston and at least loosen up the crank bearing. Or would this just be more trouble than it's worth, even if it worked?

Busby · « **Reply #6 on:** January 26, 2009, 03:05:46 PM »

Instead of using a drill press in an uncontrolled manner, polish the crank shaft with worn 600 grit wet /dry used wet,
then lap the crank to the bushing in the case lightly . This will cut down the length of time that it will take for the crank to reach its optimal clearance. You would still need to break the engine in though to get the necessary heat cycles for every thing to stabilize.
Busby

Steve Helmick · « **Reply #7 on:** January 26, 2009, 07:50:50 PM »

Well, now. I've got Don McClave's Skylark away from Dave Gardner. Because I had a nice running old .46LA, and a few NIB .40LA's, I decided to go with the .46, even though those meanies at CCMAC will make me use .018" lines. Which will require some retrimming. Don said it has a 4.5 oz tank, but I'm not getting enough laps with PM 10-22 GMA. I made a smaller venturi (.280"/K drill), and with the .156" spraybar, still no joy. It will be fine at VSC, with the .280" venturi, because of the heat and altitude. But meanwhile, I can do one of three things. 1) Make a .272" venturi. 2) Switch to 5-22 or something else with 5% pop, like SIG Champion (which I don't have in stock and don't know where I can get by Saturday). 3) Add about 5% unleaded petrol to the usual 10-22. 4) Practise until departure with fewer level laps between trix. I usually lose track anyway, so that's my plan (#4). Yup, I should probably measure the tank capacity, too.

It's said that adding petrol is right in the Merco (old GB Mercos) instructions. This was brought to light by Dave Royer, but he's probably forgotten about it by now. And actually, I think it was 8%, but why be a pig? Powerful gasoline is getting spendy again. I may try it, just to see what happens. LA's are cheap and tough. If you can't wait for an LA to break-in, shame on you! I fly 'em on the 2nd run, if it's steady and holds the needle setting. After about 10 flights, they seem to be pretty sweet, but better after a gallon of fuel.

Steve

Brian Hampton · « **Reply #8 on:** January 26, 2009, 11:58:00 PM »

The instruction sheet for my Merco 49 Black Streak says that "it has been found that adding 5% petrol can help slow running" but they're talking about zero nitro fuels. One thing they warn about several times is NOT to use medicinal castor but only something like Castrol M.

Bob Reeves · « **Reply #9 on:** January 27, 2009, 08:21:16 AM »

Quote from: Steve Helmick on January 26, 2009, 07:50:50 PM

Well, now. I've got Don McClave's Skylark away from Dave Gardner. Because I had a nice running old .46LA, and a few NIB .40LA's, I decided to go with the .46, even though those meanies at CCMAC will make me use .018" lines. Which will require some retrimming. Don said it has a 4.5 oz tank, but I'm not getting enough laps with PM 10-22 GMA. I made a smaller venturi (.280"/K drill), and with the .156" spraybar, still no joy. It will be fine at VSC, with the .280" venturi, because of the heat and altitude. But meanwhile, I can do one of three things. 1) Make a .272" venturi. 2) Switch to 5-22 or something else with 5% pop, like SIG Champion (which I don't have in stock and don't know where I can get by Saturday). 3) Add about 5% unleaded petrol to the usual 10-22. 4) Practise until departure with fewer level laps between trix. I usually lose track anyway, so that's my plan (#4). Yup, I should probably measure the tank capacity, too.

It's said that adding petrol is right in the Merco (old GB Mercos) instructions. This was brought to light by Dave Royer, but he's probably forgotten about it by now. And actually, I think it was 8%, but why be a pig? Powerful gasoline is getting spendy again. I may try it, just to see what happens. LA's are cheap and tough. If you can't wait for an LA to break-in, shame on you! I fly 'em on the 2nd run, if it's steady and holds the needle setting. After about 10 flights, they seem to be pretty sweet, but better after a gallon of fuel. Steve

You don't say how much the Skylark weighs but under the new rules I would be real surprised if you still couldn't use 15's

Steve Helmick · « **Reply #10 on:** January 27, 2009, 10:04:35 PM »

Bob...I would gladly use .015's, but VSC requires the old line sizes and pull tests. I think it's just because they haven't come to grips with the variable pull test, like your machine does. I would hope that by next year (2010), they'll get it all sorted out and will be on the same page as the rest of us. It is kinda early in the year to have the system working for such a big contest. I'm ok with it, anyway. It did require me to make a decision, and I'm not too good at that anymore.

Thanks to Brian Hampton for confirming the Merco lore and adding more details. I would think that medicinal castor wouldn't be a problem if some Klotz was used for detergent, to keep the rings unstuck. We occasionally used it in F1C's, when we failed to get organized on time. It ran just as fast, and nobody complained. About the fuel, anyway.

Steve

Alan Hahn · « **Reply #11 on:** January 28, 2009, 04:54:23 PM »

Quote from: Steve Helmick on January 27, 2009, 10:04:35 PM

Bob...I would gladly use .015's, but VSC requires the old line sizes and pull tests. I think it's just because they haven't come to grips with the variable pull test, like your machine does. I would hope that by next year (2010), they'll get it all sorted out and will be on the same page as the rest of us. It is kinda early in the year to have the system working for such a big contest. I'm ok with it, anyway. It did require me to make a decision, and I'm not too good at that anymore.

<snip.....>

o Steve

Now I may be wrong here, so I have put on my asbestos underwear, but if VSC is AMA sanctioned, I would think that they would HAVE to follow the current pull tests, just to keep within the AMA Safety Code--and their sanction insurance.

Welcome to 2009!

phil c · « **Reply #12 on:** January 28, 2009, 07:18:42 PM »

You can make any changes you want to the rules for particular contest, as long as they are spelled out in the sanction and contest publicity. If safety is involved, the AMA safety director may recommend changes. In this case, requiring heavier lines and pulls than the new current rules certainly is not a safety problem(from the lines breaking standpoint), so it would be a non-issue.

Alan Hahn · « **Reply #13 on:** January 29, 2009, 07:02:18 AM »

Quote from: phil c on January 28, 2009, 07:18:42 PM

You can make any changes you want to the rules for particular contest, as long as they are spelled out in the sanction and contest publicity. If safety is involved, the AMA safety director may recommend changes. In this case, requiring heavier lines and pulls than the new current rules certainly is not a safety problem(from the lines breaking standpoint), so it would be a non-issue.

Yes you could always pull more--especially if it is stated in the contest rules, but I don't think you can pull less than what is required by the AMA safety code---which is what I meant.

As to whether the AMA safety director reads every sanction application, I don't know.

Steve Helmick · « **Reply #14 on:** February 01, 2009, 08:05:14 PM »

As Phil said, the Contest Organizers can modify the rules, and still get a sanction, but they are required to publicize the variances from the rules in the pre-game publicity. This is why I've mentioned this particular variation several times in both forums...to help spread the word, so folks aren't surprised.

I will say that, in my opinion, it gives an extra advantage to the electrics, because they use 10g's, and we carbonators can't. They can use .015's at the same weight as I have to use .018's. How fair is that? Plus, their powerplant doesn't lose power at high altitudes, like Tucson. If they have't gotten organized enough to do 10g.'s by next year, I'm not likely to go, plain & simple.

Steve

PeteBergstrom · « **Reply #15 on:** February 03, 2009, 08:37:10 AM »

Quote from: Steve Helmick on January 26, 2009, 07:50:50 PM

It's said that adding petrol is right in the Merco (old GB Mercos) instructions. This was brought to light by Dave Royer, but he's probably forgotten about it by now. And actually, I think it was 8%, but why be a pig? Powerful gasoline is getting spendy again. I may try it, just to see what happens. LA's are cheap and tough. If you can't wait for an LA to break-in, shame on you! I fly 'em on the 2nd run, if it's steady and holds the needle setting. After about 10 flights, they seem to be pretty sweet, but better after a gallon of fuel. Steve

Steve,

I used to use white gas/Coleman Fuel (2oz per gal) to get about a 30 sec increase in run time when I was competing on a regular basis. (I got this tip from Bob emmett way too many years ago to count

) Its a bit spendy but it certainly beats having to add capacity to an existing tank. Changing venturi sizes will no doubt change the power output ... and I'm not sure you want to reduce available power to increase the flight time. Try this ... it works.

Pete

Leo Mehl · « **Reply #16 on:** February 03, 2009, 09:41:03 AM »

Quote from: Steve Helmick on January 26, 2009, 07:50:50 PM

Well, now. I've got Don McClave's Skylark away from Dave Gardner. Because I had a nice running old .46LA, and a few NIB .40LA's, I decided to go with the .46, even though those meanies at CCMAC will make me use .018" lines. Which will require some retrimming. Don said it has a 4.5 oz tank, but I'm not getting enough laps with PM 10-22 GMA. I made a smaller venturi (.280"/K drill), and with the .156" spraybar, still no joy. It will be fine at VSC, with the .280" venturi, because of the heat and altitude. But meanwhile, I can do one of three things. 1) Make a .272" venturi. 2) Switch to 5-22 or something else with 5% pop, like SIG Champion (which I don't have in stock and don't know where I can get by Saturday). 3) Add about 5% unleaded petrol to the usual 10-22. 4) Practise until departure with fewer level laps between trix. I usually lose track anyway, so that's my plan (#4). Yup, I should probably measure the tank capacity, too.

It's said that adding petrol is right in the Merco (old GB Mercos) instructions. This was brought to light by Dave Royer, but he's probably forgotten about it by now. And actually, I think it was 8%, but why be a pig? Powerful gasoline is getting spendy again. I may try it, just to see what happens. LA's are cheap and tough. If you can't wait for an LA to break-in, shame on you! I fly 'em on the 2nd run, if it's steady and holds the needle setting. After about 10 flights, they seem to be pretty sweet, but better after a gallon of fuel. Steve

Does this mean you are flying a Don McClave ARF at VSC. Shame

Alan Hahn · « **Reply #17 on:** February 03, 2009, 12:32:38 PM »

Quote from: Steve Helmick on February 01, 2009, 08:05:14 PM

As Phil said, the Contest Organizers can modify the rules, and still get a sanction, but they are required to publicize the variances from the rules in the pre-game publicity. This is why I've mentioned this particular variation several times in both forums...to help spread the word, so folks aren't surprised.

I will say that, in my opinion, it gives an extra advantage to the electrics, because they use 10g's, and we carbonators can't. They can use .015's at the same weight as I have to use .018's. How fair is that? Plus, their powerplant doesn't lose power at high altitudes, like Tucson. If they have't gotten organized enough to do 10g.'s by next year, I'm not likely to go, plain & simple. Steve

Hey Steve,
I'm stilled bummed

by the fact that the electrics are weighed--battery in while the oilers (eventually at least) will be weighed fuel-less!
I can understand why glow's don't want to have to fill the tank while being weighed--it's a hassle, but hey, I could (and do) easily remove my battery too! Also understand that my battery weighs "only" 7.3 oz in a Nobler. I am guessing that a filled up fuel tank is on the scale of ~5oz or so, so it isn't that I'm carrying around a lead brick! So if it makes you feel any better, the electrics are still being discriminated against

!

L0U CRANE · « **Reply #18 on:** February 06, 2009, 04:25:49 PM »

Steve H and Alan,

The reason for not going to the new 10g pull test at VSC, this year at least, is the same as why we'll also be using pattern points for eligible entries: - tradition.

When the 10g rule was still a proposal, a few of my concerned fellow Cholla Choppers studied the effects of pull testing models with either system. In most cases, with usual weights for models on given displacements, there were no serious differences. At least, nothing that would threaten safety. The VSC sanction request included specifying the "local variations," after a phone call confirmed that the Tech Director (I think it was, I didn't make the phone call. I trust the guy who did) was satisfied that either set of rules provided comparable safety.

One of the problem areas in comparing testing by displacement vs by weight pretty much hasn't been improved. Consider a piped VF 40 in a 48 oz model. Both '10g' and 'by displacement' would meet the specs at a 30 lb pull.

The other 'difference' between the schemes is that a model that might be pulled 45 lbs by displacement, may now be pulled somewhat less, by 10g, and by gradually increasing numbers, according to weight. Simple state of the art doesn't seem to suggest that a big 4-stroke or piped large engine powered model is likely to weigh much less than 4 lbs. The new FAI-based standard allows models up to 3.5 Kg - 7.7+ lbs. We might even see some; there have been heavier CLPA models in the past.

Alan, in the recent AMA Rulebook - not the new current one - the AMA Special Events section Electric CLPA Event specs for power and pull test were moved intact into the basic CLPA Rules. Remember, there were TWO line pull charts? One for fuel-burning engines, the other for electrics. As of this year, the REST OF US have to put up with the Electric CLPA Event pull standards.

(Unless, as often mentioned in this topic, by listing a variation acceptable to AMA re: safety, and given that any differences from Rulebook requirements are included in all advance publicity and announcements.)

(edit, adding:) Alan, no, AMA Safety people don't review EVERY sanction app, of course not. The presumption is that a Rulebook Event will be by the existing Rules. When there is an exception, which I think is much less often in comparison to the overall total of Sanction Apps, it is likely routine for AMA to either consult the equivalent of a 'policy book' or to discuss some new wrinkle that hadn't been considered before.

All the VSC Events are Unofficial, but run by AMA Safety guidance. In Classic, the flight pattern requirements of the basic current CLPA wording applies. Our exception of continuing Pattern Points merely reflects that they were a real part of the era when the eligible models appeared. It does not affect safety, so there's no AMA objection.

Alan Hahn · « **Reply #19 on:** February 06, 2009, 08:29:29 PM »

Lou,
I don't doubt that VSC won't be safe. The new rules tend to generate less pull than the old rules, except perhaps in some unusual situations.

I think it was a good idea to discuss the exemption with the AMA.

Steve Helmick · « **Reply #20 on:** February 07, 2009, 04:00:17 PM »

"All the VSC Events are Unofficial, but run by AMA Safety guidance. In Classic, the flight pattern requirements of the basic current CLPA wording applies. Our exception of continuing Pattern Points merely reflects that they were a real part of the era when the eligible models appeared. It does not affect safety, so there's no AMA objection."

I'd forgotten about the Pattern Points issue. Frankly, the statement above is confusing, because the sentance "In Classic, the flight pattern requirements of the basic current CLPA wording applies." conflicts with the following sentance. The current CLPA wording says there are no Pattern Points!

My concern is that the organizers of any contest might just decide to have more and more and more rule changes, which could be perceived as giving an advantage to those who are local. Basically, since our CLCB members voted to use the 10g pulltest and abolish PP's, why don't we use these rules and see about changing them back, if we don't think they work?

As a Judge, I can tell you that one of the worst roadblocks to progress at the circle is trying to figure out if PP's are to be awarded or not. I'm not up on the current rules (that's the new ones!!!), but recall there is something strange about how the pilot can be penalized for various infractions (level laps & completed maneuvers), and yet there are no PP's.

Well, we've certainly swerved this thread away from fuel mileage. Sorry about that!

Steve

Author Topic: Fuel mileage. Why? (Read 1932 times)

Alan Hahn

Alan Hahn

Alan Hahn

Alan Hahn

Alan Hahn

Alan Hahn