Truckracer

My Feedback: (19)

Looks like a good FAQ Pe! I'll look through it later today when time permits. Regarding laying blame on ethanol for Walbro carb deterioration, I would add this. Here in the central US, we have been using a 10% ethanol blend for decades ... not just a year or so as in other parts of the country. Yet, carb deterioration seems to be a more recent problem. I own, use or have access to many small engines that are quite old and were fed a diet of ethanol mixed (and non-ethanol) fuels all their life ... with no carb problems. As you know, most saws, trimmers, etc. will live their whole life without the insides of the carb being touched. Yet more recently, diaphram problems seem to be more of a problem in all of these sorts of engines. Perhaps ethanol is the problem or part of the problem ......... I'm not sure. Perhaps it is the mix of ethanol and other fuel ingredients .... not sure about that either.

Question for Walbro experts .... in what years were the diaphram materials changed? I still have several engines (in saws) running with the old rubberized, cloth looking diaphrams and they still look and feel perfect. RC engines here are 1 to 15 years old, all with original diaphrams.

My unscientific opinion why I have not had carb problems when other people around the country have, when ethanol is present in most locations is this. I simply believe that gasoline in my part of the USA doesn't have as many of the exotic ingredients in it as it does elsewhere. It would be interesting to hear from some of the engine mfgrs. if they see more carb problems from certain parts of the country.

Pe, you refer to Aspen from time to time .... what is Aspen?

Roger S.

altavillan

My Feedback: (1)

I picked up a couple Walbro carb repair kits the other day from the local saw shop. The kits do not include the rubberized style fuel pump gaskets. You get a choice of fiber glassed or the purple plastic type of pump chamber gasket. And acording to my saw guy they will not be making the rubberized gasket.
Wouldn't switching to higher octane gas be better for our engines during the summer months? Especialy here in Ca. How much ethanol are we getting in our fuels out here in ca?

pe reivers

Aspen is a pure alkylate fuel that was develloped to save fish populations in Nordic lakes. It has a quite narrow evaporation track, and an AKI of 94 (pump octane). The typical gas smell is absent, and it is non-toxic. In a way it resembles Coleman fuel, but has a much higher knock index.
In some engines I found starting more difficult, especially when hot, so now I use premium Euro Leadfree ( 95 RON ) again in all my engines. Cold starts always were very predictable and easy.
In my chain saw, the fuel is better than gas. Even when stored with the saw all winter, first start of the saw with the old fuel still in the tank was just like it had been run the day before.
It's use is supported and encouraged by Husqvarna, who assisted in de devellopment of the two stroke mix. I mix four stroke alkylate with my own oil of choice.
http://www.aspen.se/Aspen_(eng)_Aspen_Petroleum_Environmental_petrol_D XNI-3296_.aspx

pe reivers

Dirtybird,
Coleman mentioned burning valves when using their fuel in engines. I just copied their statement.

About detonation:
Small 2.5cc glow engines will detonate if compressed too high. I suppose, using this as a lower limit for gas engines, that ALL gas engines will detonate if effective compression is larger than the allowed compression for a certain octane rating. See the FAQ section 7.
Don't believe everything you read.

Big_Bird

My Feedback: (1)

I sure must be missing out. I've been using the ethanol laced fuel ever since they converted over from MTBE here in Texas. I fly a lot and with a variety of gassers from 2.2 cuin to 6.4 cuin. I have not had any problems. I buy gasoline from several different stations in the area. I am not one of the everybody who blames ethanol for gasser problems.

OK, time to put my hard hat and vest on because I'm going against the grain.

pe reivers

Nobody on this forum is quite sure where the old type carb problems originate from.
--Fact is, that some time ago Walbro published a tech bulletin in which they stated that their materials were not made for Methanol. Since then, they changed the pump membrane material, and the needle tip material in order to resist the newly formulated fuels.
--Fact is, that a lot of users did experience problems.
You are not alone in not having problems. I too found some carbs to have membrane hardening quickly, whilst others seemed to resist my fuels well. Maybe due to the oil-gas combination(s) used? That is why truckracer posted like he did.

Tired Old Man

My Feedback: (1)

Personally, I haven't had any issues with parts breaking down due to fuel types in the last couple years. There was a period a few years back where if I left an engine stored for a few months with fuel in the system is was guaranteed that the needle tips and rubber parts would require replacement before using the engine again. That hasn't happen for some time though. The solution at the time was to flush the fuel system with alcohol. Didn't do the residual lubrication in the engine much good though.

pe reivers

Neither did I, just with old carbs. I mean OLD.
Until recently on a test engine from China with Walbro carb. The pump petals curled in a few days. Needle settings started to wander off and had to be opened, until in the end the engine would just run off the choke prime before it stopped. A repair kit with mylar pump membrane fixed that.

http://www.mvvs.nl/MVVS/images/walbr...ech%20talk.gif

captinjohn

If I have a carb with parts that may harden by setting..ect.. I spray silicone spray in them. It seems to keep em working real good. I also spray any groments and other rubber parts with silicone spray. Works like a charm keeping them flexible. Have done this for over 20 years!!! Capt,n

dirtybird

My Feedback: (5)

I don't believe everything I read- even those from Europe. Its just that I have read that in many places- that detonation does not occur in small engines. I expect that if you raise the compression high enough it would occur in anything. But then I note that nobody uses gasoline in diesels. But only in small engines do they need to add ether to make them work with kerosine. If you could just use gasoline why fool with ether?
FWITW I have used coleman fuel in my ZDZ 80 for sometime with no ill effects. I don't use a pipe

Tired Old Man

My Feedback: (1)

Talk to RTK about detonation in small engines. After replacing a cylinder I'm pretty sure he'll disagree with you. He heard the damage taking place.

The follow on to all this should be interesting. Engineer versus engineer. The gauntlet was tossed in the post above...

RTK

My Feedback: (1)

The one thing I do know is that if you lug an engine, on a hot day, and are a tad on the lean side, pushing it hard, you will start to hear a funny noise, kinda like shaking a bag of large rocks, there will also be a noticeable power loss. I would advise anyone that hears and notices above mentioned power loss to stop immediately, if you try and make that odd noise again it will be too late

dirtybird

My Feedback: (5)

I read that that if you lug an engine, on a hot day, and are a tad on the lean side with a glow engine you just might destroy it but I have never done it. The alcohol fuel used in a glow engine has a really, really high octane rating.

RTK

My Feedback: (1)

Mine was a gasser that I burnt.
To date I have only destroyed bearings in glow engines, never scored a cylinder Yet. But then again I haven't flown glow in over a year. If I put my mind to it I am sure I could

Tired Old Man

My Feedback: (1)

I have a better idea. Since you don't believe it's possible for detonation to occur in a small engine, take about 400 engines and start running them for numerous continuous hours at various mixture settings, with various oil mixes, with various fuel types and octane ratings, including diesel and several jet fuel concotions, and do all this in a 120 plus degree enviornment. Develop about 50,000 hours of running time on those engines and get back to me on how many experienced detonations and under what conditions. We've already done this (and more) so your results won't come as a surprise. But at least you will not have read it but will have experienced it first hand, perhaps making you a believer instead of a perprtual skeptic.

dirtybird

My Feedback: (5)

Say I would like to do that. Would you like to finance it?
Have you published your results somewhere? Oops sorry, Pe says I shouldn't believe what I read.
It would be helpful if you did publish your finding somewhere along with an indication of your test methods and recorded data.
Otherwise its just. whats that word they use in courtroom dramas?, heresay or something like that.

pe reivers

Dirtybird,
Just keep on running your ZDZ engine on coleman fuel, and report back here in due time, without shame or loosing face. It is a big man that can admit defeat.
I know that ZDZ, being a European engine, will need a better octane fuel, and Coleman does not fill the bill. You will need at least 89 octane (pump rating), though I would use 91 octane in these engines.
If you are careful, and keep the plugs black from overly rich mixtures, and keep throttle application low, and cooling flow high, you just might get away with it.
OTOH, if you are just being stubborn. So be it. A man has got the right to make his share of <.....>. You fill in the appropriate word yourself.

Tired Old Man

My Feedback: (1)

Dirtybird,

Have you ever looked first hand at a government declassified report? Notice how they always seem to have those blacked out sections in just about every place you really want to see? Those are admissable as evidence too, but unfortunately a lot of information is sensitive, restricted, and proprietary, and may not be released for another 50 years or so.

Yes, I know the results of private money spent in private testing should be open for everyone to see and use, with no back compensation to the originator for information obtained from that research. Don't happen that way and you darn well know it. Sometimes you have to go a little on trust. If you have to have absolute proof of everything you would complete and/or accomplish nothing.

dirtybird

My Feedback: (5)

Unfortunately I crashed the aircraft it was on so I guess we will never know unless I get around to building another. I don't fly ARF's. Well that's not true either. I do have a ARF but its smaller. That ZDZ is too big. The props cost too much.
Yep, I am being stubborn.

dirtybird

My Feedback: (5)

I have seen a few classified government reports. At one time I held a security clearance. I learned that performance figures for model airplane engines are not exactly top secret.

bubbagates

My Feedback: (32)

Me thinks someone needs to listen. Certain folks on here are pretty knowledgable when it comes to these engines. The've done all the research and testing as well as practical experience.

Tired Old Man

My Feedback: (1)

DB,

It's not the basic performance that's the issue, it's how that performance can be applied, and limitations designed into any given product. We've covered this ground before and it's still a no go with me. Much of what's done with model engines goes so far beyond regular modeling as to be incomprehensible for many. We have no desire to enlighten them on our dime. They don't now, nor ever will, buy our products or pay our bills.

dirtybird

My Feedback: (5)

The why do you bother to post here? People with technical baxckground will not believe when you have no data to back up your statements. "Trust me I know best." We have all been burned by that statement.
Its the basic performance we are interested in. We couldn't care less about how you apply it. Or your product.

Tired Old Man

My Feedback: (1)

If you had held a secret clearance as you state, then you already know why praticulars will not be provided. As for the technonerds that won't believe, I don't really care. They won't believe anything, even with a full print out, unless they can find a way to take credit for the information. Even when they are dead wrong! Fact of life is that most (not all) engineers of any type come out of college with the beginners engineering degree convinced that only engineers know anything (generally perceived as EVERYTHING) and only engineers can provide useful data. They will argue for months with a handful of numbers telling you that ketchup is blue, then two months later tell you that due to new data ketchup has morphed to the color yellow. This while they are looking at a plate with red ketchup on it. So why bother.

Tell you a little story about one of the best experiences with an engineer I've ever had. This was back in 1980, when solar energy was beeing aggressively marketed in California and I was in sales. Made an appointment with a nuclear engineer to dsemonstrate our wares. At the time the Feds were offering a 40% tax CREDIT with no cap on the purchase of a solar water system. Let's leave the cost amortization time out of this. The State was offering a 15% tax credit to go along with the federal one, and the area utility was providing a 4% finance program in the form of a second T.D. that took back seat to everything. We weren't selling hot water or solar, but a real nice government funded, utility financed 55% tax CREDIT. The solar heated hot water was just a bonus in th elong run.

Now this engineer just could not get it through his head that what he was looking at was a means to substantially reduce his extremely high tax load over the next few years because the credits exceeded his liability and could be carried forward. All he was interested in was nitpicking the tiniest numerical efficiency data in comparison to other products that were also available. After 6 hours with the guy I gave up. I had an appointment next door the next day with his neighbor, who owned a small retail store.

Next day I meet the neighbor and explain the system and all the benefits, including the financial ones. The guy needed a new roof, so that was added to the sale since it would support the domestic water system. He also had a pool and wanted to heat that but he needed some type of rack to hold the collectors. So he got a new back porch and wood framed overhead awning to hold the pool collectors. By the time all was said and done ho got all his water heating needs, a new back porch, awning, and roof as part of the deal. All financed at 4% for 20 years with the total cost reduced 55% by the state and federal government through tax credits, and eliminated his tax liability to both agencies for the next 6 years.

The engineer was so smart, and made sure to let me know he knew more about what I had and did than myself, that he never saw the forest for the trees.

From where I'm at you can take it or leave it. Means nothing to me either way and my feelings aren't bothered in the least. You may have had a clearance and perhaps have outlived the limit of the restrictions. OTH, I respect and obey the conditions and restrictions associated with what I do, and people outside that circle have no importance or right to anything data developed there. You need to go back and review the conditions associated with that old clearance, as well as others that may have been applied by the employer.

dirtybird

My Feedback: (5)

It seems to me you are a bit resentful of engineers. Did an engineer steel your girlfriend?
When I was in college my finance ran off with a baseball player. To this day I can't stand that game.

I have to admit engineers tend to be a bit cliquish. Most of them have spent a lot of hard work and money to get that degree. They resent someone invading their turf that don't have the credentials. I got my education paid for by being a hired assassin for three years. I spent three years in the armed forces in WW2. A friend of mine, a mechanical engineer,got his paid for by spending a year on the front lines in Korea.. I am not saying you can't do the work of an engineer without a degree but it sure helps.
Most engineers are quick to spot a phony. One of the traits of a phony is saying I know best but I can't say why.