Diesel .50s (mostly)
09-19-2015, 08:29 PM
#151
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Some things of note in there, but it still doesn't answer my question. What makes the Fox .50 such a great diesel conversion when power is similar between both fuels on a big prop? I understand the principle of diesel, and I'm all for it... I'm just unimpressed with the difference in power between the diesel and glow setups. If the diesel runs 1,000rpm faster than it did on glow on the same big prop, that's one thing... Expecting a 400rpm difference or so - doesn't really make it worth the money spent on fuel and converting the engine?
To be clear - I'm not nitpicking. I'm just trying to understand what is so great about the engine..? I will say that I'm glad it still runs and I haven't wrecked it yet...
To be clear - I'm not nitpicking. I'm just trying to understand what is so great about the engine..? I will say that I'm glad it still runs and I haven't wrecked it yet...
A classic example of the avoidance of cognitive dissonance?
I know the with the new Fora and Parra .15 diesels/glow the difference on the same engine, with the same venturi hole size, prop, mounting stand, etc, and just changing heads, is negligible. This is with the diesel running 20/30/50 +dii, and the glow standard 10% nitro fuel. On 5% nitro glow the engine might be a few hundred rpm under the diesel.
I'd bet that your +400 rpm gain would dwindle away if you optimised the compression on the glow head. or used a tighter fitting head.
Certainly using a bottom sealing glow plug setup would give a much greater gain on the latter.
Last edited by qazimoto; 09-20-2015 at 12:38 AM.
09-20-2015, 01:10 AM
#152
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Hey Quick,
You had that engine singing a fine song in that last video. I presume you dropped the liner to get the compression up?
I don't know how much effect the timing change would make but I suspect, like you, it won't hurt too much at the lower rpm range. You're not looking for max power anyway are you?
I run my Diesel conversions purely for the pleasure of getting them to run and throttle well, and to be different. I'm not too worried about the cost of the fuel or the power I'm getting.
Having said that I'm getting a useful power increase. My 40 FSR gained 500 rpm on a 10X6 but that's the only prop I've tried so far. My 20 FP gained around 1000 rpm on all the props I tried between 10X4 and 10X6, a little less on an 8X6 and 9X4. The best prop on Diesel is bigger than the best prop on Glow, but that doesn't mean Diesel is better over all, depends on the model I suppose. Mind you my glow figures are with 0% nitro, so there is more power to be found there.
Have you tried your engine with the throttle fully open? It may be that it will work OK.
I have found that my engines won't throttle up to quite the same rpm initially after a long period at idle. This is because the engine has cooled down a bit and is therefore retarded slightly. It might take a second or two to regain max rpm. I find if I tune the idle on the rich side the rpm comes back quicker, also if I tune rich or slightly higher compression on the high side there is less lag.
Have you noticed that you can increase the compression past the point where the burping just stops? It's the equivalent of leaning a glow past where the 4 stroking breaks into 2 stroking. More power but the same problem if you go too far.
Dave H
You had that engine singing a fine song in that last video. I presume you dropped the liner to get the compression up?
I don't know how much effect the timing change would make but I suspect, like you, it won't hurt too much at the lower rpm range. You're not looking for max power anyway are you?
I run my Diesel conversions purely for the pleasure of getting them to run and throttle well, and to be different. I'm not too worried about the cost of the fuel or the power I'm getting.
Having said that I'm getting a useful power increase. My 40 FSR gained 500 rpm on a 10X6 but that's the only prop I've tried so far. My 20 FP gained around 1000 rpm on all the props I tried between 10X4 and 10X6, a little less on an 8X6 and 9X4. The best prop on Diesel is bigger than the best prop on Glow, but that doesn't mean Diesel is better over all, depends on the model I suppose. Mind you my glow figures are with 0% nitro, so there is more power to be found there.
Have you tried your engine with the throttle fully open? It may be that it will work OK.
I have found that my engines won't throttle up to quite the same rpm initially after a long period at idle. This is because the engine has cooled down a bit and is therefore retarded slightly. It might take a second or two to regain max rpm. I find if I tune the idle on the rich side the rpm comes back quicker, also if I tune rich or slightly higher compression on the high side there is less lag.
Have you noticed that you can increase the compression past the point where the burping just stops? It's the equivalent of leaning a glow past where the 4 stroking breaks into 2 stroking. More power but the same problem if you go too far.
Dave H
09-20-2015, 02:03 AM
#153
One important thing to remember, is that one cannot expect certain gain from every single engine. The conversions where you will see the largest gain is from engines that are a bit anaemic/timid as glow engines. These are typically limited, as glow engines, due to restrictive timing, restricted port areas, and small carbs etc. When converted to diesel and using lower revs these things are no longer limiting and then they now perform as they ought to do with respect to their cylinder volume.
Here are two examples where I have personal experience; Cox PeeWee and the Queen Bee. In particular the Queen Bee went from something fairly useless on glow to something that is well acceptable on Diesel. On glow this engine would only take a 6x3 prop (it would overheat on a 6x4) and spin it at around 17000rpm (corresponding to about 75W, and typical .049 engine power).
On Diesel fuel this engine can spin an 8x4 at 10500rpm (75W) or a 7x4 at around 13800rpm (95W), so the torque is much higher than on glow and it now provides a far more useful engine in practice.
On the other end of the scale, taking a great and well optimised glow engine (like the Parra) and converting it diesel, you will see much less difference in terms of power. But there should still be a difference in fuel consumption and the ability to handle large props (both are in favour of Diesel).
Last edited by Mr Cox; 09-20-2015 at 02:19 AM.
09-20-2015, 03:38 AM
#154
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I know from personal experience that there can be a large difference between Diesel and glow, and I'm willing to discuss evidence...
One important thing to remember, is that one cannot expect certain gain from every single engine. The conversions where you will see the largest gain is from engines that are a bit anaemic/timid as glow engines. These are typically limited, as glow engines, due to restrictive timing, restricted port areas, and small carbs etc. When converted to diesel and using lower revs these things are no longer limiting and then they now perform as they ought to do with respect to their cylinder volume.
Here are two examples where I have personal experience; Cox PeeWee and the Queen Bee. In particular the Queen Bee went from something fairly useless on glow to something that is well acceptable on Diesel. On glow this engine would only take a 6x3 prop (it would overheat on a 6x4) and spin it at around 17000rpm (corresponding to about 75W, and typical .049 engine power).
On Diesel fuel this engine can spin an 8x4 at 10500rpm (75W) or a 7x4 at around 13800rpm (95W), so the torque is much higher than on glow and it now provides a far more useful engine in practice.
On the other end of the scale, taking a great and well optimised glow engine (like the Parra) and converting it diesel, you will see much less difference in terms of power. But there should still be a difference in fuel consumption and the ability to handle large props (both are in favour of Diesel).
One important thing to remember, is that one cannot expect certain gain from every single engine. The conversions where you will see the largest gain is from engines that are a bit anaemic/timid as glow engines. These are typically limited, as glow engines, due to restrictive timing, restricted port areas, and small carbs etc. When converted to diesel and using lower revs these things are no longer limiting and then they now perform as they ought to do with respect to their cylinder volume.
Here are two examples where I have personal experience; Cox PeeWee and the Queen Bee. In particular the Queen Bee went from something fairly useless on glow to something that is well acceptable on Diesel. On glow this engine would only take a 6x3 prop (it would overheat on a 6x4) and spin it at around 17000rpm (corresponding to about 75W, and typical .049 engine power).
On Diesel fuel this engine can spin an 8x4 at 10500rpm (75W) or a 7x4 at around 13800rpm (95W), so the torque is much higher than on glow and it now provides a far more useful engine in practice.
On the other end of the scale, taking a great and well optimised glow engine (like the Parra) and converting it diesel, you will see much less difference in terms of power. But there should still be a difference in fuel consumption and the ability to handle large props (both are in favour of Diesel).
Both will usefully perform on the bench in the twin modes with up to a 3/16" venturi hole. The glow versions will probably produce much more power on crankcase pressure with a bigger hole and/or more nitro. The diesel mode will probably become difficult to tune on crankcase pressure and a larger hole.
Diesel mode then always has the potential for better economy/power, glow for more ultimate power. However by playing with the ingredients of the glow fuel significant improvements in economy with the same performance is possible. Some of these are Ethanol and Iso Propyl Alcohol.
The Cox Pee Wee's I've owned have been excellent glow engines. I don't think that restrictive porting has been it's problem, In fact most of us gave up using it as a sports free flight engine because even though it only displaced .32cc it had too much performance for the .5cc "small field" diesel models we put them in. Their life as a diesel is usually severely limited because of mechanical problems. I haven't tried it but reducing the compression ratio and exhaust duration on glow may temporarily improve performance on larger props. At least until the crankpin breaks.
Don't know about the Queen Bee, but if fitting a new head transforms your engines into the "excellent" grade then surely that's where the original problem occurred?
My claim is that like for like there's no real difference. Simply whacking on a diesel head on a glow engine isn't going to make an observably significant difference.
Last edited by qazimoto; 09-20-2015 at 03:47 AM.
09-20-2015, 04:45 AM
#155
I don't know how much effect the timing change would make but I suspect, like you, it won't hurt too much at the lower rpm range. You're not looking for max power anyway are you?
I run my Diesel conversions purely for the pleasure of getting them to run and throttle well, and to be different. I'm not too worried about the cost of the fuel or the power I'm getting.
Having said that I'm getting a useful power increase. My 40 FSR gained 500 rpm on a 10X6 but that's the only prop I've tried so far. My 20 FP gained around 1000 rpm on all the props I tried between 10X4 and 10X6, a little less on an 8X6 and 9X4. The best prop on Diesel is bigger than the best prop on Glow, but that doesn't mean Diesel is better over all, depends on the model I suppose. Mind you my glow figures are with 0% nitro, so there is more power to be found there.
Have you tried your engine with the throttle fully open? It may be that it will work OK.
I have found that my engines won't throttle up to quite the same rpm initially after a long period at idle. This is because the engine has cooled down a bit and is therefore retarded slightly. It might take a second or two to regain max rpm. I find if I tune the idle on the rich side the rpm comes back quicker, also if I tune rich or slightly higher compression on the high side there is less lag.
Have you noticed that you can increase the compression past the point where the burping just stops? It's the equivalent of leaning a glow past where the 4 stroking breaks into 2 stroking. More power but the same problem if you go too far.
Dave H
I found it concerning that the instructions on Davis Diesels website says to not hand start a diesel, but to use a starter...
http://news.davisdieseldevelopment.c...ines-fuel.html
Thanks for all of your help Dave H. I learned something new and so far its still working.... So I'm a happy camper.
Tim
09-20-2015, 05:21 AM
#156
I'm a conversion sceptic. I'm proposing that the difference in performance between diesel and glow is probably mostly just wishful thinking. Comparing like with almost (but not quite) like. It's very difficult to even get people to discuss the evidence.
A classic example of the avoidance of cognitive dissonance?
I know the with the new Fora and Parra .15 diesels/glow the difference on the same engine, with the same venturi hole size, prop, mounting stand, etc, and just changing heads, is negligible. This is with the diesel running 20/30/50 +dii, and the glow standard 10% nitro fuel. On 5% nitro glow the engine might be a few hundred rpm under the diesel.
I'd bet that your +400 rpm gain would dwindle away if you optimised the compression on the glow head. or used a tighter fitting head.
Certainly using a bottom sealing glow plug setup would give a much greater gain on the latter.
A classic example of the avoidance of cognitive dissonance?
I know the with the new Fora and Parra .15 diesels/glow the difference on the same engine, with the same venturi hole size, prop, mounting stand, etc, and just changing heads, is negligible. This is with the diesel running 20/30/50 +dii, and the glow standard 10% nitro fuel. On 5% nitro glow the engine might be a few hundred rpm under the diesel.
I'd bet that your +400 rpm gain would dwindle away if you optimised the compression on the glow head. or used a tighter fitting head.
Certainly using a bottom sealing glow plug setup would give a much greater gain on the latter.
09-20-2015, 12:44 PM
#157
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The 1/4 turn or so more compression you can get might not give you much more rpm but it might make the transition better, and might be required when you fly (float?) the engine to allow for the rpm rise when moving.
I'm slightly confused about your compression setting now. You said that the comp screw had bottomed out and you needed to lower the liner, but now you have the screw backed out about a turn? Has the ring seal improved, or maybe you are tuned at a richer setting? I might have missed something there.
Yes the use of the 'electric finger' is a bit controversial amongst traditional Dieselists but, to be fair, Davis is aiming the instructions at someone who may have no experience with Diesels. He gives an initial setting for compression and needle, which with no priming should avoid hydraulic lock. This avoids the situation where a modeller with a poor flick will fiddle with the settings rather than continue flicking and therefore never get a start. Once the compression setting is established, priming, a careful check for hydraulic lock, then a quick bump with the starter will give an instant start every time. It might not be such a good technique on a vintage Diesel though. They are mostly plain bearing engines and not many of them have a thrust washer behind the prop driver to stop it wearing on the case when pushed back by the starter. Some engines will even have the crank pin or con rod rub on the back plate if you push the shaft back, so even if you avoid bending the rod with a hydraulic lock the engine still wears badly with electric starting. No problem with a modern plain or ball bearing converted engine though.
The only time a Diesel will bite (usually) is if the compression is set higher than the starting setting, and even then a really fast flick will over come this. Look for some videos of Team Race pit stops and restarts to see the experts at work.
I don't understand your use of the term 'stink up' with reference to the beautiful and refined Diesel aroma? Is it sort of like how an Aussie will call a red headed person 'Blue'?
Great to see you making such good progress,
Dave H
I'm slightly confused about your compression setting now. You said that the comp screw had bottomed out and you needed to lower the liner, but now you have the screw backed out about a turn? Has the ring seal improved, or maybe you are tuned at a richer setting? I might have missed something there.
Yes the use of the 'electric finger' is a bit controversial amongst traditional Dieselists but, to be fair, Davis is aiming the instructions at someone who may have no experience with Diesels. He gives an initial setting for compression and needle, which with no priming should avoid hydraulic lock. This avoids the situation where a modeller with a poor flick will fiddle with the settings rather than continue flicking and therefore never get a start. Once the compression setting is established, priming, a careful check for hydraulic lock, then a quick bump with the starter will give an instant start every time. It might not be such a good technique on a vintage Diesel though. They are mostly plain bearing engines and not many of them have a thrust washer behind the prop driver to stop it wearing on the case when pushed back by the starter. Some engines will even have the crank pin or con rod rub on the back plate if you push the shaft back, so even if you avoid bending the rod with a hydraulic lock the engine still wears badly with electric starting. No problem with a modern plain or ball bearing converted engine though.
The only time a Diesel will bite (usually) is if the compression is set higher than the starting setting, and even then a really fast flick will over come this. Look for some videos of Team Race pit stops and restarts to see the experts at work.
I don't understand your use of the term 'stink up' with reference to the beautiful and refined Diesel aroma? Is it sort of like how an Aussie will call a red headed person 'Blue'?
Great to see you making such good progress,
Dave H
09-20-2015, 02:53 PM
#158
I'm slightly confused about your compression setting now. You said that the comp screw had bottomed out and you needed to lower the liner, but now you have the screw backed out about a turn? Has the ring seal improved, or maybe you are tuned at a richer setting? I might have missed something there.
Yes the use of the 'electric finger' is a bit controversial amongst traditional Dieselists but, to be fair, Davis is aiming the instructions at someone who may have no experience with Diesels. He gives an initial setting for compression and needle, which with no priming should avoid hydraulic lock. This avoids the situation where a modeller with a poor flick will fiddle with the settings rather than continue flicking and therefore never get a start. Once the compression setting is established, priming, a careful check for hydraulic lock, then a quick bump with the starter will give an instant start every time. It might not be such a good technique on a vintage Diesel though. They are mostly plain bearing engines and not many of them have a thrust washer behind the prop driver to stop it wearing on the case when pushed back by the starter. Some engines will even have the crank pin or con rod rub on the back plate if you push the shaft back, so even if you avoid bending the rod with a hydraulic lock the engine still wears badly with electric starting. No problem with a modern plain or ball bearing converted engine though.
The only time a Diesel will bite (usually) is if the compression is set higher than the starting setting, and even then a really fast flick will over come this. Look for some videos of Team Race pit stops and restarts to see the experts at work.
I don't understand your use of the term 'stink up' with reference to the beautiful and refined Diesel aroma? Is it sort of like how an Aussie will call a red headed person 'Blue'?
Great to see you making such good progress,
Dave H
The only time a Diesel will bite (usually) is if the compression is set higher than the starting setting, and even then a really fast flick will over come this. Look for some videos of Team Race pit stops and restarts to see the experts at work.
I don't understand your use of the term 'stink up' with reference to the beautiful and refined Diesel aroma? Is it sort of like how an Aussie will call a red headed person 'Blue'?
Great to see you making such good progress,
Dave H
Last edited by 1QwkSport2.5r; 09-20-2015 at 02:56 PM.
09-20-2015, 04:29 PM
#159
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It is a personal thing.
I find the smell of glow engine exhaust burning synthetic oil and nitro methane much more acrid than the (to my nose) sweeter smell of diesel exhaust. I also get an unpleasant allergic reaction if I spill raw glow fuel on my skin. Methanol is a particularly nasty poison and is readily absorbed through the skin.
Granted, diesel clean up rags do tend to hold the odour. Female olfactory senses in particular often find it most disagreeable.
To get around the clean-up issue, I use shop rag which comes in tear-off rolls. It is economically priced and it works brilliantly. I dump used rags in the bin at the field, and don't take dirty towels or cotton rags home any more. Makes for an easy life and a clean smelling car/model storage area.
I find the smell of glow engine exhaust burning synthetic oil and nitro methane much more acrid than the (to my nose) sweeter smell of diesel exhaust. I also get an unpleasant allergic reaction if I spill raw glow fuel on my skin. Methanol is a particularly nasty poison and is readily absorbed through the skin.
Granted, diesel clean up rags do tend to hold the odour. Female olfactory senses in particular often find it most disagreeable.
To get around the clean-up issue, I use shop rag which comes in tear-off rolls. It is economically priced and it works brilliantly. I dump used rags in the bin at the field, and don't take dirty towels or cotton rags home any more. Makes for an easy life and a clean smelling car/model storage area.
09-20-2015, 04:43 PM
#160
Fiery Have to agree 110% on that one standing by a running glow engine on a stand or behind on the field irritated my nose and eyes--no issue with diesel regards to all martin
OH OH post note on the" Diesel is dead posts", spoke with Bob Davis yesterday and Tower ( USA company) is now stocking the Davis half A fuel and yes Davis head
conversions for the Cox
OH OH post note on the" Diesel is dead posts", spoke with Bob Davis yesterday and Tower ( USA company) is now stocking the Davis half A fuel and yes Davis head
conversions for the Cox
Last edited by AMB; 09-20-2015 at 04:50 PM.
09-20-2015, 04:46 PM
#161
My glow fuel contains only the finest ingredients - nitromethane, castor oil, and methanol. It doesn't burn your nose like the synthetic oil usually does. It smells rather sweet to me.
The paper towel idea is a good one. I may consider going that route for cleanup as I usually use old t-shirts cut up for rags.
The paper towel idea is a good one. I may consider going that route for cleanup as I usually use old t-shirts cut up for rags.
09-21-2015, 02:10 PM
#162
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I recall some good advise from one of the old British magazines (was it Roland Graunchet?). Apparently you should spend a lot of time standing behind the model with the exhaust blowing over your shirt or trouser legs. All clean up should be done with your handkerchief which is then stuffed in your trouser pocket. Given time, the 'female olfactory problem' resolves itself about the same time as your earache stops.
You 'don't mind it much'? That's great, you're nearly there, you won't be a 'proper' Dieselist until you love it though
.
Dave H
You 'don't mind it much'? That's great, you're nearly there, you won't be a 'proper' Dieselist until you love it though
.Dave H
09-21-2015, 04:07 PM
#163
I recall some good advise from one of the old British magazines (was it Roland Graunchet?). Apparently you should spend a lot of time standing behind the model with the exhaust blowing over your shirt or trouser legs. All clean up should be done with your handkerchief which is then stuffed in your trouser pocket. Given time, the 'female olfactory problem' resolves itself about the same time as your earache stops.
You 'don't mind it much'? That's great, you're nearly there, you won't be a 'proper' Dieselist until you love it though.
Dave H
You 'don't mind it much'? That's great, you're nearly there, you won't be a 'proper' Dieselist until you love it though
.Dave H
09-21-2015, 07:38 PM
#164
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You could be right.
I've got a couple of 'proper' Diesels myself, but I'm more interested in using the conversions in sports aerobatic planes.
I used to watch planes with my Dad too.
I've got a couple of 'proper' Diesels myself, but I'm more interested in using the conversions in sports aerobatic planes.
I used to watch planes with my Dad too.
Last edited by gerryndennis; 09-21-2015 at 07:46 PM.
09-21-2015, 08:02 PM
#165
I was never much of an aviation fan though... Like I never intended to fly rc aircraft. I never wanted to get into boats either, but a couple of unrun aircraft engines changed that. The airboat fad started. Then my buddy talked me into planes, then diesels, etc. My buddy is building a twin cylinder .22ci diesel from plans. Originally was supposed to be a .11ci radial ported diesel, but he screwed the crankcases up from not having his lathe shimmed properly (squared up dead true). He was gonna build 3 identical engines. Plan B is the two cylinder. Looking forward to seeing it built and running.
09-22-2015, 06:44 AM
#166
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I just ran the Irvine .40 Diesel. Compression is 1.5 turns out from max, 9,000 was doable but mighty rattley.
Irvine .40 D
Prop==Bolly 12.5x6
Fuel==Davis ABC blend
Exhaust==MVVS .40/.49 Quiet muffler, (3245)
Max rpm=8,800, pictured
Idle==super smooth 2,000
Irvine .40 D
Prop==Bolly 12.5x6
Fuel==Davis ABC blend
Exhaust==MVVS .40/.49 Quiet muffler, (3245)
Max rpm=8,800, pictured
Idle==super smooth 2,000
Last edited by Hobbsy; 09-22-2015 at 11:56 AM.
09-22-2015, 02:36 PM
#168
I ran my Fox conversion again today. I'm getting more comfortable with making the adjustments and getting it running nice. To get absolute peak power (9,300rpm on a 12x7 APC) it wanted to be set on the edge of overcompressed. A little less than 1/4 turn from missing and burping to being just a tad rattly. The oil color was dark brown at this point. Backing the needle off and lowering compression slightly gave a top rpm of about 9,000rpm and oil color closer to a medium maple syrup color. Throttling was improved with a slightly richer idle mixture and a higher compression setting, though it seemed a little inconsistent when throttling back up from a short 5-10sec idle. Increasing the compression slightly helped but wasn't perfect. I suspect this is how this engine runs. The compression screw likes to back out from vibration, so backing it off 1/4 turn and bringing it back to the original setting helps keep it in one spot. I haven't been using the locking grub screw yet as I've had to make several adjustments while getting a feel for the engine. I'm not sure I've gotten it quite lean enough to get absolute max power from it yet, so more fiddling may get me closer to the numbers FDF has posted in the past. I am not trying to achieve what he has, but just to get a feel for where the maximum lean setting really is and getting the compression just right.
So... Max power I got was 9,300rpm on a 12x7 APC; compression screw about 1 turn out from seated. Best idle I got was 1,700rpm which gave a satisfactory throttle transition. Video here: http://youtu.be/jdYAIj3nqJ8 I was a little undercompressed still, but the engine ran smooth on top. Throttle was tested full open and also about 80% and max rpm was the same. So I'll stick with the 80% throttle or thereabouts for my maximum. It will not start cold at the previous run setting. Two flips with carb plugged with fuel at the carb and 1/4 higher compression from previous run setting gets it running with 2-3 flips at a fast idle. After refueling the warm engine, getting fuel just to the carburetor gives a 1 or 2 flip restart at a fast idle.
So... Max power I got was 9,300rpm on a 12x7 APC; compression screw about 1 turn out from seated. Best idle I got was 1,700rpm which gave a satisfactory throttle transition. Video here: http://youtu.be/jdYAIj3nqJ8 I was a little undercompressed still, but the engine ran smooth on top. Throttle was tested full open and also about 80% and max rpm was the same. So I'll stick with the 80% throttle or thereabouts for my maximum. It will not start cold at the previous run setting. Two flips with carb plugged with fuel at the carb and 1/4 higher compression from previous run setting gets it running with 2-3 flips at a fast idle. After refueling the warm engine, getting fuel just to the carburetor gives a 1 or 2 flip restart at a fast idle.
Last edited by 1QwkSport2.5r; 09-22-2015 at 02:53 PM. Reason: Added more info
09-22-2015, 02:52 PM
#170
I edited my last post adding some info to the bottom of the post.
That at is good old castor oil. I used 20% oil content in my fuel. I used the higher oil (20%) since I had the engine apart a couple times so I figured a little extra lube wouldn't hurt while the ring settled back into the liner. Compression is pretty good as of now. It never felt this nice with the old P/L/ring. So it seems to be sturdy enough.
That at is good old castor oil. I used 20% oil content in my fuel. I used the higher oil (20%) since I had the engine apart a couple times so I figured a little extra lube wouldn't hurt while the ring settled back into the liner. Compression is pretty good as of now. It never felt this nice with the old P/L/ring. So it seems to be sturdy enough.
09-23-2015, 01:43 AM
#171
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That looks pretty good to me mate, you'd have to be reasonably happy with that wouldn't you? Well done.
It would be interesting to see how that engine runs on some different props maybe 11X6 and 12X6. You could even use one of the Thrust/Horsepower graphs to work out a bit of a power curve. Why not put the glow head back on and do a curve for that as well? Lots of work for you but interesting for us. You could put it down to developing your Diesel skills further (as if you haven't got it pretty well sussed now).
You can obviousely hear what your engine is saying to you so I'm sure you'll pick up the exhaust crackle when you get close to maximum lean. It's more obvious on some engines than others though. Running Diesels lean is normally perfectly safe (they just die if you go too lean) but this is where they are running the hottest and it is possible for some engines to start to overheat. This will start advancing the engine and can lead to more heat and sounding hard and slowing down over advanced. Generally called 'going hard' or 'going over (compressed)' even though the over advanced situation is due to heat not compression. I've already mentioned this so I know you know to ignore your glow training and either close the throttle or back off compression instead of richening the needle if this happens.
That grub screw is meant to adjust the tension on the comp screw rather than lock it. There should be a nylon? Insert under the grub screw that rubs on the comp screw. The idea is you have it tight enough to stop the comp from moving by itself, but loose enough that you can easily adjust the comp.
Well done Quick,
Dave H
It would be interesting to see how that engine runs on some different props maybe 11X6 and 12X6. You could even use one of the Thrust/Horsepower graphs to work out a bit of a power curve. Why not put the glow head back on and do a curve for that as well? Lots of work for you but interesting for us. You could put it down to developing your Diesel skills further (as if you haven't got it pretty well sussed now)
.You can obviousely hear what your engine is saying to you so I'm sure you'll pick up the exhaust crackle when you get close to maximum lean. It's more obvious on some engines than others though. Running Diesels lean is normally perfectly safe (they just die if you go too lean) but this is where they are running the hottest and it is possible for some engines to start to overheat. This will start advancing the engine and can lead to more heat and sounding hard and slowing down over advanced. Generally called 'going hard' or 'going over (compressed)' even though the over advanced situation is due to heat not compression. I've already mentioned this so I know you know to ignore your glow training and either close the throttle or back off compression instead of richening the needle if this happens.
That grub screw is meant to adjust the tension on the comp screw rather than lock it. There should be a nylon? Insert under the grub screw that rubs on the comp screw. The idea is you have it tight enough to stop the comp from moving by itself, but loose enough that you can easily adjust the comp.
Well done Quick,
Dave H
09-23-2015, 04:45 AM
#172
That looks pretty good to me mate, you'd have to be reasonably happy with that wouldn't you? Well done.
It would be interesting to see how that engine runs on some different props maybe 11X6 and 12X6. You could even use one of the Thrust/Horsepower graphs to work out a bit of a power curve. Why not put the glow head back on and do a curve for that as well? Lots of work for you but interesting for us. You could put it down to developing your Diesel skills further (as if you haven't got it pretty well sussed now).
It would be interesting to see how that engine runs on some different props maybe 11X6 and 12X6. You could even use one of the Thrust/Horsepower graphs to work out a bit of a power curve. Why not put the glow head back on and do a curve for that as well? Lots of work for you but interesting for us. You could put it down to developing your Diesel skills further (as if you haven't got it pretty well sussed now)
.You can obviousely hear what your engine is saying to you so I'm sure you'll pick up the exhaust crackle when you get close to maximum lean. It's more obvious on some engines than others though. Running Diesels lean is normally perfectly safe (they just die if you go too lean) but this is where they are running the hottest and it is possible for some engines to start to overheat. This will start advancing the engine and can lead to more heat and sounding hard and slowing down over advanced. Generally called 'going hard' or 'going over (compressed)' even though the over advanced situation is due to heat not compression. I've already mentioned this so I know you know to ignore your glow training and either close the throttle or back off compression instead of richening the needle if this happens.
That grub screw is meant to adjust the tension on the comp screw rather than lock it. There should be a nylon? Insert under the grub screw that rubs on the comp screw. The idea is you have it tight enough to stop the comp from moving by itself, but loose enough that you can easily adjust the comp.
Well done Quick,
Dave H
Burned a half quart of fuel so far, gonna need more ether soon. I'm gonna cobble together another engine to experiment with that I have a diesel head that fits. That engine may self destruct though.. I'll see.
Last edited by 1QwkSport2.5r; 09-23-2015 at 07:17 PM.
09-23-2015, 04:17 PM
#173
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'My diesel head doesn't have anything to cushion against the compression screw ...'
I use a 1/16" snippet of lawn trimmer cord of a suitable diameter for a 'plug' in my Irvine diesels. I prefer the smooth surface variety, some trimmer cord is 'ribbed'. It works very well. The most difficult thing is cutting it - it is tough.
My understanding is that Davis Diesel Heads are supplied with 'buffer' between the grub screw and compression screw to maintain tension and prevent compression screw 'thread chewing'. Perhaps yours was missing.
I use a 1/16" snippet of lawn trimmer cord of a suitable diameter for a 'plug' in my Irvine diesels. I prefer the smooth surface variety, some trimmer cord is 'ribbed'. It works very well. The most difficult thing is cutting it - it is tough.
My understanding is that Davis Diesel Heads are supplied with 'buffer' between the grub screw and compression screw to maintain tension and prevent compression screw 'thread chewing'. Perhaps yours was missing.
Last edited by fiery; 09-23-2015 at 04:21 PM.
09-23-2015, 06:08 PM
#175
'My diesel head doesn't have anything to cushion against the compression screw ...'
I use a 1/16" snippet of lawn trimmer cord of a suitable diameter for a 'plug' in my Irvine diesels. I prefer the smooth surface variety, some trimmer cord is 'ribbed'. It works very well. The most difficult thing is cutting it - it is tough.
My understanding is that Davis Diesel Heads are supplied with 'buffer' between the grub screw and compression screw to maintain tension and prevent compression screw 'thread chewing'. Perhaps yours was missing.
I use a 1/16" snippet of lawn trimmer cord of a suitable diameter for a 'plug' in my Irvine diesels. I prefer the smooth surface variety, some trimmer cord is 'ribbed'. It works very well. The most difficult thing is cutting it - it is tough.
My understanding is that Davis Diesel Heads are supplied with 'buffer' between the grub screw and compression screw to maintain tension and prevent compression screw 'thread chewing'. Perhaps yours was missing.