compression comparison and exhaust color
 

What is the average compression ratio of a diesel? What about glow? I'm just wondering how much more compression I'm putting in my engine if I convert to diesel. What color is the exhaust? I've read that it is blue, like glow, and I've read that it's a dark chocolate color. Thanks.

RE: compression comparison and exhaust color
 

The exhaust smoke looks like glow. The oil residue is sort of a dark carmel.

Yes there is more load but it isn't a problem. Hydro locking while starting is a big problem! Running over compressed can be hard on the engine too.

RE: compression comparison and exhaust color
 

Thanks for the reply. As far as compression, I'm really looking into how much more compression there is going to be.

RE: compression comparison and exhaust color
 

http://www.rcuniverse.com/forum/m_6173596/tm.htm

RE: compression comparison and exhaust color
 

There will be more compression. Only thing that matters is if there is the right amount of compression for it to run right. Remeber it is adjustable. How about somewhere between 11 to 18 to one?

RE: compression comparison and exhaust color
 

That sounds about right.

RE: compression comparison and exhaust color
 

Compression ratio and color both depend on the fuel mix you are using.

It used to be a standard that the fuel residue should be a light amber color if compression is correct. The more compression, the darker the residue. This may no longer hold true because of the many and various fuel components, and perhaps the metalurgy used in the engines.

If you always approach optimum compression by first decreasing, then increasing to optimum, you stand less chance of running over-compressed. You will find that there is often a "flat" range between where performance increases or decreases. The low end of that range runs cooler, and the high end of that range runs hotter.

Years ago some had problems with throttled diesels because if idled for awhile, then brought to max, you would find that the engine had cooled enough to take it off the optimum compression setting. By running with a little more compression, the throttle would work better.

Also, prop unloading will change compression needs in some cases. Trial end error will yield optimum setting. I tend to run it on the low end of optimum. In my mind, it saves the engine. Perhaps I am wrong.

George

RE: compression comparison and exhaust color
 

Using commercial fuels, I like for the residue to be from colorless to light caramel or honey colored. When I started running my Tower 40 on the bench with commerical fuel, It would give a black exhaust regardless of compression. As I ran the engine more and flew it, using the same fuel, the exhaust gradually changed to colorless.

As to the compression issue, I have run a glowplug K&B 4011 on 10% Sig Champion glow fuel turning an APC 11 x 5 at 9,700. Filled the tank with Davis 1/2A fuel. Attached the battery to the glow plug, started the engine, let it warm up for 20 - 30 seconds, Turned the needle in 1 1/2 turns, and it ran smoothly and turned the APPC 11 x 5 at 9,700. Did the glow plug contribute any heat with the battery off? I don't know. Another K&B 4011 would run undercompressed and come up to speed when the battery was reattached. I am not convinced there is a gap between usual glow engine compression and low end diesel engine compression.

RE: compression comparison and exhaust color
 

I can see some overlap in compression ratio, especially in larger engines with large amounts of ether. 1/2A fuel is probably 40% or more ether so you could probably get a lot of engines to run on it.

RE: compression comparison and exhaust color
 

Most of my 2 stroke conversions had very little glow time and some none ,right to diesel and they ran lots of smoke and dark oil out the stack, as the hours ran up they run much cleaner very light exhaust and in most no dark oil Of course as they ran in the compression screw was backed out and leaner thus cleaner martin
a couple I could feel NO OIL uot the stack so i riched it a little till I got some it cost 200-300 rpm or so but felt a little safer

RE: compression comparison and exhaust color
 

My opinion is that the booster adds plug heat for starting but the plug only retains some heat from combustion when the booster is disconnected. As you already know, the glow plug heat is generated by a catalytic reaction with the alcohol in glow fuel when the booster is disconnected.

George

RE: compression comparison and exhaust color
 

Sorry I took so long to get to this question. All small engine run much cooler due to there small mass leading to a excess loss of heat, just the opposite of large engine with their greater mass have trouble getting rid of heat. This as you might expect effect how they burn fuel. now you know why cox 049'3 need 30% nitro to perform at their best. In keeping with these facts a small diesel will have a caramel colored exhaust if run with castor lube while a .40 sixe diesel will have a black exhaust. Know i'm talking about the oil residue not the smoke. When you burn alky the by-products are carbon dioxide and water vapor thats why the it's white just like those pretty thing up in the sky the diesel is like your car when you burn a hydrocarbon fuel you have smoke that is gray or black the latter is work and it is wispy. If you check out YOU TUBE and type in DIESEL REVO you will see what I'm talking about. Oh for thta guy that wanted to know about speed of response and power this video put that quest to rest as racing experts that have viewed the video stated its a rocket ship. For those of you that are new to this forum please understand diesel is not experimental it a very mature commercial product and the fuel is very available so you don't have to make any. Remember modelers that use glow don't make there own fuel they buy it and they don't try to improve on their engines they use them.

Some of the last words of this post were removed by the moderator

RE: compression comparison and exhaust color
 

ugo

RE: compression comparison and exhaust color
 

your sample looks like a urine sample I don't know what your doing but i don't think you read my last post. Keep the crazy fuel stuff to yourself it will be better and safer if you do, don't you think?

RE: compression comparison and exhaust color
 

ugo

RE: compression comparison and exhaust color
 

Two of your statements, which you seem to think are undeniable fact....

1)Model diesel fuel is readily available... in some countries that may well be true... at a price and often with the addition of shipping charges. In other countries (there are some apart from yours)
it is both very difficult and expensive to obtain.

2)Model diesel engines are a mature technology. Yes they are, but you seem to imply that that's it,
and there is nothing further to do but buy conversion heads and use the fuel that is provided by people like you. Mature it certainly is BUT that doesn't mean that it can't be improved, especially the fuel..... there are always more ways of doing things than some would have us believe.

Years ago diesel engines, for road vehicles, were quite primitive. Get behind a big rig on a steep hill and you were crawling as he slowed right down. That was mature technology AT THE TIME !
Look at todays diesels and the advances in performance that have taken place, along with lubricants and fuel additives.

This forum is open to all ideas as it says.... Everything Diesel. It is not reserved for you to tell others they shouldn't be posting here as that gives the impression you are just trying to protect your own commercial interests.

One moderator for the forum should suffice, especially as he is seen to be doing a good job !
Or did we have an election ?

FACT.... model diesel engines run very well on commercial fuel.
FACT.... they also run very well on alternative fuel mixes and there are guy's who have done it for
years so it is not something either new, or unknown.

There will always be those who run to a commercial fuel supplier, there will also be those who know that a "better" fuel can be made far more cheaply. I haven't seen anyone who is devising and posting information about fuel mixes suggest that commercial interests should be kept out of the forum and taken elsewhere. Is that because we have nothing to either hide or fear ?

Reg

The beginning of this post was removed by the Moderator

RE: compression comparison and exhaust color
 

ugo

RE: compression comparison and exhaust color
 

There's been a few posts deleted along about here for personal attacks. If your post is missing you now know why.

Lets keep it to a civil discussion.

Even something as thin as a sheet of paper has two sides. Discussions often have two sides also.

This an international site. We in the USA must remember that commercially available model diesel fuel may not be easy to obtain in some other countries? However in the USA, it is cheaper and less bother (safer also) to just buy your model diesel fuel commercially.

W8ye - Moderator

RE: compression comparison and exhaust color
 

For a knowledgable person in the USA, commercial diesel fuel is not hard to come by, nor all that expensive. It is also entirely possible to mix good useable fuel with a little effort scrounging around. What is quite unlikely is that you go down to your LHS and buy diesel fuel off the shelf at a reasonable price. It is also unlikely that you will meet anyone at the flying field who really knows diesels.

I do disagree with Bob, from my experience running a dieselized Tower 40, about exhaust color. As I said above, the first runs, with Davis 1/2A fuel :eek: had a really black exhaust regardless of compression setting. I had the engine maybe 10 years before I ever built an airplane for it, and ran it on the bench many times. Over time the exhaust cleared up. When I started flying it, I was getting carmel exhaust which became clear as I flew the engine more. I flew it on both 1/2a fuel and Davis plane fuel. Really couldn't tell much difference.

I suppose breaking in the engine has something to do with it. I put a couple of hundred flights on that engine diesel, and perhaps another 500 or more flights glow. It still has good pinch, starts right up and runs fine.

A friend, who knows diesels, mixes his own fuel using John Deer Starter for the ether. His engines run fine and have black exhaust. We think it is due to compounds in the John Deer fluid.

RE: compression comparison and exhaust color
 

This forum for R/c universe oh and by the way it was to be to help with their engines and interest models to get into diesel.

Most people don't know it but in England were you live commercial diesel is very available so if you want to make your own your just plain cheap. You should be out their flying not being the mad scientist brewing up unpredictable witches brew.


Parts of this post were removed by the moderator

RE: compression comparison and exhaust color
 

I must jump in here and at this point and in a way this is connected with the subject of this thread . . . .

It is part of the very nature of many modelers to want to experiment and build their own and be cheap at times. In the past, I've been into Ham Radio and this very same nature to do your own thing exist amongst a lot of the Hams also. If a person is not of this nature, he's generally not much of a hobbyist or has some deep pockets.

I would like to thank Mr Davis for helping to get the diesel part of this forum started and for his support to the diesel airplane modeling community over the years.

W8YE Moderator

RE: compression comparison and exhaust color
 

I inderstand that you originally got this forum going. That was a worthy act.
It is however labelled as Everything Diesel, it's interesting that one of the longest series of posta were about trying to find an alternative to ether. That thread aroused a lot of interest.

Some of the interest came from those who live in countries where commercial model diesel fuel is either very difficult or impossible to get hold of. It is sad to find that there are people who want to use, or try diesels and are prevented by not being able to get fuel for them.

As you stated, in the quote above, diesel fuel is readily available in the U.K. That is indeed true, but not the whole story. My nearest hobby shop is a 90 mile round trip. He can only supply 1 litre tins of diesel. He tried to get me a gallon but Model Technics would not supply him unless he put in a "special order" for several hundred £'s worth of fuel. Buying in 1 litre quantities is more expensive.

OK so I decide to get my fuel by mail order, only 2 companies are licenced to send it. 1 imperial gallon costs the equivalent of $66 with a mailing cost of another $20, so I am paying $86 for my gallon of fuel. I can go and personally get 1 gallon of glow fuel for around $16.

If I can't get the cost of the diesel fuel down then I wouldn't use them ! Here in the home of the diesel, the U.K, the majority of people use glow engines.... I wonder why ? There would probably be a lot more who would try diesel and possibly find they like them BUT as soon as they look at the price of fuel they go and buy a glow engine.

I AM out there flying, and I am doing it at 1/3 the cost of the commercial fuel. I would have done a lot more flying but this summer has been exceedingly wet, however conditions are good at the moment. I also , recently, got 36 minutes flying with a PAW .15 on a 2oz tank of 10% ether fuel !

I am not playing the crazy scientist.... olive oil was used as a substitute for castor in aero engines in WW1. Non-ether fuels (never mind low-ether) have been used in the UK for many years. A guy I went flying with ran a PAW 19 on completely etherless fuel, just paraffin and 2 stroke oil for years.
He started the engine up and ran it for me so that I could see it was still O.K.

Coincidentally, like the moderator of this group, I also got involved in Amateur radio. Passed the exams and morse test and hold a full licence. I enjoyed building a lot of my own equipment... much more fun than buying something off the shelf and the sense of achievement is worth it !

My interest in RC planes started with building a kit, graduated to building from plans and I am now scratch building from my own designs...... never, ever bought a finished model or even an ARTF and don't have any interest in doing so.Model plane kits are currently going the same way as model diesel users.... they are rapidly vanishing.

Reg

RE: compression comparison and exhaust color
 

ugo

RE: compression comparison and exhaust color
 

Hi Merugo, I usually stick my thumbnail into the exhaust and look at the color on my thumbnail. You don't really nead a picture of my oily thumbnail. :D

RE: compression comparison and exhaust color
 

Sorry you did not read a number of my earlier posts which clearly stated that we sell all over the world and have supplied forulas for over 32 years to the jungles of africa but it must be stated for the record that when someone makes afuel that causes others harm that person that wrote the words and poseted them becomes the teacher iand s is subject to lawsuit. So you can understand why its a bad idea to post experimental things over the internet.

Bob Davis
Davis Diesel