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VM Empire Where the VM-68's and PMI-3 Come out to play

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Old 04-22-2009, 01:20 PM   #11 (permalink)
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Originally Posted by Menace View Post
Again, these are just the pics, to whet the tinker appetite.
I'm all wet and starving!

I'm really impressed so far, you have done a good job explaining everything and posted pictures too. Something most posters have yet to master.

I look forward to your discoveries regardless of the outcome.
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Old 04-22-2009, 03:25 PM   #12 (permalink)
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Thankee!
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Old 08-23-2009, 01:12 AM   #13 (permalink)
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Gang,

Sorry for the four-month delay. Been extraordinarily busy with work and travel, and have had precious little time until recently even to pop in here, let alone to a field to put the new valve to the test.

However, I did manage to scrape together about two-and-a-half hours at a field last week (thanks in large part to the pestering of Onehitwonder, whom I was visiting briefly). There are still numerous variables that have yet to be nailed down, and so all of this should be viewed with the highest suspicion at present. I personally don’t believe a word of it, and I was there. But Onehit is nearly wetting himself for me to report something, so here goes.

The short and dirty version is that the valve APPEARS to be an improvement over the stock version.

There was an APPARENT velocity spike of fairly significant proportions with the new valve vice the unmodified, and efficiency also APPEARED to be none the worse for this increase in velocity. This MAY translate into a POSSIBLE improvement in overall efficiency once everything is fully examined and all the dust settled.

Again, at present this is little better than the typical noob, "My new denim-lined barrel totally added like three miles to my range, dude," drivel. Most of the “testing” time was spent laughing at the initial results, and in general just enjoying a bit of relaxation at the first outing in a long time.

So. More rigorous testing is coming, and I'll put hard data with the final report, to be (dis)confirmed by any who wish to test it for themselves. It may be another month or so, but if we are all still kicking around with VMs we (hopefully) have learned something of patience, eh?

Cheers,

M
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Old 01-27-2011, 12:15 AM   #14 (permalink)
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Gang,

As if the previous update wasn't late enough, I've just gotten a reminder that I still haven't posted any results on the mod. My apologies for the delay. It's been a really rotten interval, and I've been out to play only three times since the last posting nigh a year and a half ago. Been hammered with work, more work, tragedy, loss and grief, and still more work.

As such I've never had any chance to test this thing at all properly and rigorously (wide variety of conditions and paint, multiple markers, etc.), and may not any time soon. Three casual outings and a case or two of paint will have to suffice for now. It can't be helped. So very, very sloppy by any standards. Hopefully others will be able to take it up and do some more testing and playing with it. Bear also in mind that this marker was tested all by its lonesome. Sold off the second-to-last VM a few years ago (), and so don't have another to compare it with, which would help tremendously in testing, vice merely switching the modded and stock valves out in a single marker. So there is no particular reason to expect the same results in yours. However, I can now say with some confidence that this mod should at worst make no harmful changes (see warning below), and at best should be noticeably (albeit slightly) helpful, if you do it correctly.

So here's the short and skinny. What I didn't tell anyone from the beginning was that when I sunk the set screws into the valve body, I deliberately ran them down into the chamber itself, in order to decrease the chamber volume. The reasons for this should be clear enough.

**Amateur tinkerers/newby-types beware: Your VM is a piece of history. It doesn't need any modification to be a wonderful and fun marker. Keep it as is. You don't need this mod. The improvements you may get with it are so slight that no one but you will ever notice, if at all. This is not for the careless, the clumsy, the imprecise, the faint of heart. If in doubt, let someone else do this, or better still, don't do it at all. At the very least, do this on a spare. Or just pretend you did it, tell your friends about your sweet mod, spray lots of paint, and live a life of fun and ease. The valve stem moves in the bonnet/guide with a significant degree of mechanical tolerance. In lay terms, it wiggles laterally. This in turn requires tolerances with respect to the set screws in the valve body. If you do not understand this, or lack mechanical judgment, stop reading, go play with your stock marker, and be happy. If you do understand this, but do not measure, test fit, and measure again, then you will either impinge on the valve stem or not impinge enough on the chamber. And if you impinge on the stem itself, you deserve the wrath of the VM gods, which is of course what you will get in the end. You have been warned.**

In short, all things considered, I noted a jump of about 30 fps (not particularly helpful, save in colder weather, but interesting nonetheless) and overall gas savings/shot increase of about 10% over the stock valve.

So. Not exactly a magical barrel and, on a gas hog like this, little more than a drop in the bucket, but a fun project and a nice little boost nonetheless. And bear in mind this is what I noted on MY marker. My VM has multiple mods on both the upper and lower bolts, as well as on the spring and elsewhere, any and all of which may likely influence the effects of the valve mod in ways that would be quite different from a stock or differently modded VM. So while there is no particular reason (assuming you have the necessary skill set for this) to see any loss of performance, there is no reason to assume that you will see the same, or better, or even any improvement at all. Again, lots more testing is needed, and I simply don't have the time (and plural VMs) as of now.

If you want to pick my brain on any of the technical stuff or anything else, you are more than welcome to pm me, and I'll share all that I have. I'm truly sorry that I wasn't able to do a better job with testing on this one. You guys deserve it. So, mea culpa on that score.

Cheers,

Menace
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Last edited by Menace; 01-27-2011 at 12:18 AM.
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