PMC IMP engine first run

GailInNM · Mar 5, 2009

In the late 1960's a small compression ignition engine called the PMC IMP was introduced. In the time since it's introduction no one ever said it was a good looking engine. In fact the most glowing report on it just said that it "ran". So I of course had to build one or three.

It was a compression ignition engine with a 0.314 inch bore X 0.488 inch stroke. This gave a displacement of 0.038 cubic inch or 0.62 cubic centimeter.

I will do a sort of work in process thread on this, but in the mean time this shows the first run which was a few hours ago. Actually it is the second run as the first run was spent getting the settings approximately right.

For those who want to see some of the work in process photos, and just can't wait, they can be viewed at
http://s338.photobucket.com/albums/n404/NMSteam/IMP/
There is no annotation on any of the photos as this will be covered the the WIP thread. It will be a few days before I will be able to start that thread.

Gail in NM,USA

[youtube=425,350]8x3PalJlz0w[/youtube]

Maryak · Mar 5, 2009

Gail,

Fantastic engine and smooth as silk once you got the compression set. RPM ???

Best Regards
Bob

cfellows · Mar 5, 2009

That is really cool, Gail. Great looking engine!

Chuck

GailInNM · Mar 5, 2009

Thanks Bob and Chuck.

Bob, I have not put a tachometer on it and it would be unfair to do so yet for two reasons. First off it has less than ten minutes time on it. Second, the prop on it is a big club more suitable for an engine of two to three times the IMP's displacement. I wanted a heavy club to make starting easier and wanted to keep the RPM down until I get a little more time on it. The prop is a 7x4 and a more suitable prop will be a 6X3 or there abouts. It is a long stroke engine so it will not have a very high RPM. Stroke/bore ratio is about 1.56 : 1 so it is way over square.

I would have put a tach on it for fun, but a sand storm was starting to blow in so I folded up and came inside. I live in an area almost as dry as some of the parts of OZ these days. It did rain in November and there were a few snow pellets in January that would hit, bounce and then evaporate before the came down again.

I probably won't be able to run it again for a few days as I will be busy.

Gail in NM,USA

steamer · Mar 5, 2009

Nice looking engine Gail!.....I want to see build pictures! ;D :bow:

I have read a bit about building compression ignition, but I am very curious as to your approuch....

Getting the piston fit just so appears to be crucial.

Dave

GailInNM · Mar 6, 2009

I had a little time yet this morning so I put another 15 minutes on the engine.
Got the tachometer out and measured 9060 RPM with the 7X4 propeller.
Put on a 6X3 propeller and got about 10900 RPM.
I showed a little over 11000 for a few seconds, but I am not sure that was real.

Not too bad for 0.038 cubic inches.

I think with the long stroke/small bore ratio that 11000 RPM will be about the limit on this engine.

Also, I live at about 5300 feet (1600 meters) elevation and that knocks off a fair amount of power, although it should not affect the max unloaded RPM a lot.

Now it's time to scrub the ether off my body and go off to a business meeting. I would not want anyone to think I was playing with ether for a different, but currently quite popular, purpose.

Gail in NM,USA