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compression comparison and exhaust color - 8/15/2007 4:25:56 AM   
R/Cpullerdude


 

Posts: 224
Joined: 6/7/2007
From: Camb. Spr., PA, USA
Status: offline 		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.

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RE: compression comparison and exhaust color - 8/15/2007 6:35:45 AM   
chevy43


 

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From: Santa Cruz, CA, USA
Status: offline 		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.

(in reply to R/Cpullerdude)
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RE: compression comparison and exhaust color - 8/15/2007 6:56:39 AM   
R/Cpullerdude


 

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Joined: 6/7/2007
From: Camb. Spr., PA, USA
Status: offline 		Thanks for the reply. As far as compression, I'm really looking into how much more compression there is going to be.

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RE: compression comparison and exhaust color - 8/15/2007 12:09:13 PM   
gkamysz


 

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Greg

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RE: compression comparison and exhaust color - 8/16/2007 5:56:13 AM   
chevy43


 

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Status: offline 		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?

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RE: compression comparison and exhaust color - 8/16/2007 1:33:28 PM   
gkamysz


 

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quote:

ORIGINAL: chevy43

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?


That sounds about right.

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RE: compression comparison and exhaust color - 8/16/2007 1:46:33 PM   
gcb



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Joined: 10/24/2002
From: Port Ewen, NY, USA
Status: offline 		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

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RE: compression comparison and exhaust color - 8/16/2007 6:44:32 PM   
Jim Thomerson



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From: Austin, TX, USA
Status: offline 		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.

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RE: compression comparison and exhaust color - 8/16/2007 6:57:12 PM   
gkamysz


 

Posts: 1793
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From: Crystal Lake, IL, USA
Status: online 		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.

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RE: compression comparison and exhaust color - 8/16/2007 10:09:40 PM   
AMB


 

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From: winter park, FL, USA
Status: offline 		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

< Message edited by dieseldan -- 8/16/2007 10:14:11 PM >

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RE: compression comparison and exhaust color - 8/17/2007 5:27:00 AM   
gcb



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quote:

ORIGINAL: Jim Thomerson
...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.


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

(in reply to Jim Thomerson)
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RE: compression comparison and exhaust color - 9/7/2007 2:03:37 PM   
ddd


 

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From: CT
Status: offline 		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

< Message edited by w8ye -- 9/7/2007 8:57:23 PM >

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RE: compression comparison and exhaust color - 9/7/2007 4:52:08 PM   
merugo


 

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From: rome, ITALY
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< Message edited by merugo -- 9/12/2007 6:03:35 AM >

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RE: compression comparison and exhaust color - 9/7/2007 7:01:43 PM   
merugo


 

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From: rome, ITALY
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< Message edited by merugo -- 9/12/2007 6:04:03 AM >

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RE: compression comparison and exhaust color - 9/7/2007 7:21:16 PM   
slope-soarer


 

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From: Barrow in Furness, UNITED KINGDOM
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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

< Message edited by w8ye -- 9/7/2007 8:52:52 PM >

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RE: compression comparison and exhaust color - 9/7/2007 8:48:09 PM