mvvs 2.5dfs/r sort of success
08-11-2015, 05:21 AM
#26
Join Date: Jun 2014
Location: Hudson Valley. New York. USA
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Victory...
Greetings Gentlemen, and Alleluia.
I got a chance to set up the test stand yesterday evening with great expectation.
Most things were left the same from the non-runs the previous day (Sat) to minimize the changing variables.
Well, instead of 4 hours of flipping and hunting for a workable combo of compression and NV, it only took me 15 minutes to get a much much more promising burp from the engine.
I started out with a closed NV and primed exhaust and intake.
I was able to dial in the settings and get more promising burps and even purrs with the NV.
Opening the NV - it finally grabbed under its own aspiration and off she went, as designed.
So, many thanks for the interdiction and intervention to help figure things out.
Whew, that was both fun and a relief - with your help I know quite a bit more about these engines, now...
Here you go, wouldn't deny you the chance to be there for the Moment...
XXXXXXhttps://youtu.be/ZG34v6wr2JYXXXXXX
Updated Video https://youtu.be/zRpEqeBmGJw
Cheers, Peter
I got a chance to set up the test stand yesterday evening with great expectation.
Most things were left the same from the non-runs the previous day (Sat) to minimize the changing variables.
Well, instead of 4 hours of flipping and hunting for a workable combo of compression and NV, it only took me 15 minutes to get a much much more promising burp from the engine.
I started out with a closed NV and primed exhaust and intake.
I was able to dial in the settings and get more promising burps and even purrs with the NV.
Opening the NV - it finally grabbed under its own aspiration and off she went, as designed.
So, many thanks for the interdiction and intervention to help figure things out.
Whew, that was both fun and a relief - with your help I know quite a bit more about these engines, now...
Here you go, wouldn't deny you the chance to be there for the Moment...
XXXXXXhttps://youtu.be/ZG34v6wr2JYXXXXXX
Updated Video https://youtu.be/zRpEqeBmGJw
Cheers, Peter
Last edited by BrightGarden; 08-11-2015 at 06:56 AM. Reason: Update vid, new link
)
08-11-2015, 05:43 PM
#28
Join Date: Jun 2014
Location: Hudson Valley. New York. USA
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Makes all the sense in the world now, though, as usual once a mystery is solved.
I may not have all the knowledge but now I have the aroma - no masking that!
08-12-2015, 03:44 AM
#29
Join Date: Jun 2008
Location: Christchurch, NEW ZEALAND
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Well done Pete,
You would be surprised how often the liner in backwards problem comes up, more commonly with the old baffle piston engines though.
Nice video but I noticed that you might need to loosen up the contra piston slightly, the compression should drop when you adjust the tommy bar while it's running.
This is beyond my experience, but I've read that gently tapping the contra up and down the bore a few times might be enough. Remove the cylinder liner from the engine. Get a short length of wooden dowel just slightly smaller in diameter than the cylinder. Place the cylinder upright on a piece of wood, place the dowel on top of the contra and gently tap it down the bore a short distance. Turn the cylinder over and gently tap it back to the top. Repeat three or four times then reassemble (make sure the liner is the right way round
) and run your engine. Hopefully the compression should back off with the adjuster while its running now.
If your contra is still too tight then the next step is to remove it from the bore and lap it in a bit. It's very easy to get this wrong and end up with a loose contra piston so I'll stand back and let the experts talk you through that one if it's required.
Also, if you don't mind me saying, you should be very careful about leaving things lying on your bench with the engine running. One day something important will fall off and break or get lost, or something will vibrate towards your engine and get flicked by the prop towards you or a loved one, or your hand will reach out to prevent one of these things from happening before your brain can say stop. You will find that running propellers defend their airspace very vigorously, and the blood can stain a nice engine quite badly.
You've got that engine running nicely though, thanks for the video.
Dave H
You would be surprised how often the liner in backwards problem comes up, more commonly with the old baffle piston engines though.
Nice video but I noticed that you might need to loosen up the contra piston slightly, the compression should drop when you adjust the tommy bar while it's running.
This is beyond my experience, but I've read that gently tapping the contra up and down the bore a few times might be enough. Remove the cylinder liner from the engine. Get a short length of wooden dowel just slightly smaller in diameter than the cylinder. Place the cylinder upright on a piece of wood, place the dowel on top of the contra and gently tap it down the bore a short distance. Turn the cylinder over and gently tap it back to the top. Repeat three or four times then reassemble (make sure the liner is the right way round
) and run your engine. Hopefully the compression should back off with the adjuster while its running now.If your contra is still too tight then the next step is to remove it from the bore and lap it in a bit. It's very easy to get this wrong and end up with a loose contra piston so I'll stand back and let the experts talk you through that one if it's required.
Also, if you don't mind me saying, you should be very careful about leaving things lying on your bench with the engine running. One day something important will fall off and break or get lost, or something will vibrate towards your engine and get flicked by the prop towards you or a loved one, or your hand will reach out to prevent one of these things from happening before your brain can say stop. You will find that running propellers defend their airspace very vigorously, and the blood can stain a nice engine quite badly.
You've got that engine running nicely though, thanks for the video.
Dave H
09-11-2015, 02:53 PM
#31
Hi:
I also have a MVVS D7 nd I got it out of storage this week to get it running. What I learned was this:
The fuel tank must be a bit higher than the NVA. Otherwise, the fuel would drain back into the tank.
I would increase the compression until the contra would hit the piston. I would back it off until this did not happen.
I would drip THREE drops of fuel into the venturi and flip the prop. It would start this way in usually in four or less flips! When it started, it would run but be very over compressed. I would decrease the compression until it ran very well. I can not get it to start at the running position for the compression. The compression must be increased for a cold start. Hot starts? I do not need them! Lol
WARNING! When I used this starting drill, I would check to see if the engine was difficult to turn over due to being over compressed each time before I flicked the prop as fuel was draw in fuel from the nva. Many times there was too much compression. I only decreased the compression about 1/8 of a turn at a time! The engine would start easily at this setting. If it feels too tight, back off the compression.
The D7 is a great sport engine!
I hope that this helped,
Franchi
I also have a MVVS D7 nd I got it out of storage this week to get it running. What I learned was this:
The fuel tank must be a bit higher than the NVA. Otherwise, the fuel would drain back into the tank.
I would increase the compression until the contra would hit the piston. I would back it off until this did not happen.
I would drip THREE drops of fuel into the venturi and flip the prop. It would start this way in usually in four or less flips! When it started, it would run but be very over compressed. I would decrease the compression until it ran very well. I can not get it to start at the running position for the compression. The compression must be increased for a cold start. Hot starts? I do not need them! Lol
WARNING! When I used this starting drill, I would check to see if the engine was difficult to turn over due to being over compressed each time before I flicked the prop as fuel was draw in fuel from the nva. Many times there was too much compression. I only decreased the compression about 1/8 of a turn at a time! The engine would start easily at this setting. If it feels too tight, back off the compression.
The D7 is a great sport engine!
I hope that this helped,
Franchi
09-11-2015, 04:46 PM
#32
Join Date: Jun 2014
Location: Hudson Valley. New York. USA
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Hi Franchi - thanks for the share. I will get mine out again and see if it mimics your behavior. I'm thinking a side effect of high compression is starting hot and having the contra-piston stick so you can't ease compression.
As a note I just accidentally won a brand new Irvine 40 with a diesel head on ebay. I am going to be seeking some expertise in breaking this one in.
As a note I just accidentally won a brand new Irvine 40 with a diesel head on ebay. I am going to be seeking some expertise in breaking this one in.
