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Post by jondorb1 on Sept 27, 2011 20:39:09 GMT -5
I'm leaning toward the Great Plains 2276. Does anyone have experience with this engine? Any drawbacks? Same questions for the Nikasil cylinders. Jon
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pttim
New Member
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Post by pttim on Sept 30, 2011 11:22:31 GMT -5
Gaston uses a 2276, when I flew with him we climbed a 900 feet per minute. I beleive he made flower pots out of his Nikasil cylinders.
Tim
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Post by n3480h on Sept 30, 2011 19:35:53 GMT -5
Flowerpots!!! ;D ;D ;D
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Post by maddog on Oct 2, 2011 18:52:17 GMT -5
Just trying to remember back to sonerai.net, but I seem to recall that the problem with Nikasil cylinders was the copper gasket between cylinder to case not having enough surface area.
mb
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Post by martinroy6100 on Oct 3, 2011 9:12:39 GMT -5
Folks:
I have 125 hours on my 2276 with the "flower pot" cylinders, they work great. My two cents is they are critical to even tension on the head bolts. I check mine every ten hours for the first fifty and now at annuals. My head temps stays at around 300-325 at cruise all the time.
Martin Roy
N61QC
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hans
Full Member
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Post by hans on Oct 3, 2011 10:18:55 GMT -5
Folks: I have 125 hours on my 2276 with the "flower pot" cylinders, they work great. My two cents is they are critical to even tension on the head bolts. I check mine every ten hours for the first fifty and now at annuals. My head temps stays at around 300-325 at cruise all the time. Martin Roy N61QC Using the alu/nikasil cylinders is something I contemplated some time back. One question I could not get answered was the next one: The VW manuals specify a head bolt tension that is in part based on the fact that the cast iron cylinders expand while heating up, i.e. the final tension that the head bolts see with a running engine that is warmed up is quite a bit higher than that the head bolts was torqued to. As alu expands differently I would expect that alu cylinders require a different head bolt torque than that of a cast iron job, yet I never saw these different torque values specified anywhere... Do the alu/nikasil cylinders come with corresponding amended torque data? cheers Hans |
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Post by martinroy6100 on Oct 3, 2011 11:27:32 GMT -5
Hans:
I asked Steve and he gave me the same number, but as I was concerned after hearing about Gaston I checked the head torque multiple times. They needed an adjustment the first two ten hour intervals after that they were good. They did take a while to get the rings seated but I believe it was due to using Marvel Mystery oil in the fuel, I stopped and they seated, or maybe it was just time? I think that Aluminum expand more, so the tension would be greater? If things change I will pots my issues.
Martin Roy
N61QC
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hans
Full Member
Posts: 166
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Post by hans on Oct 4, 2011 7:50:50 GMT -5
Hi Martin, you're right, check out this table: physics.info/expansion/Aluminum seems to expands a bit over double the amount of iron at the same delta-T. On a table like this one I based my expectation that the torque value to apply might possibly be different. With alu cylinders the rings get a much higher load, perhaps these should be different from the ones used with iron cylinders? In Gaston's situation, it might have been a case of overloaded rings? cheers Hans |
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Post by o2koold on Oct 4, 2011 8:23:57 GMT -5
Hi Hans,
I believe that Gaston stated the problems was not the pistons/cylinders, but the custom made shims used to set his compression ratio. His shims somehow caused the cylinders to wedge in place and they were destroyed in the attempt to remove them.
Scott
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hans
Full Member
Posts: 166
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Post by hans on Oct 4, 2011 11:02:28 GMT -5
Hi Hans, I believe that Gaston stated the problems was not the pistons/cylinders, but the custom made shims used to set his compression ratio. His shims somehow caused the cylinders to wedge in place and they were destroyed in the attempt to remove them. Scott that would be consistent with my above assumptions, i.e. that the rings/shims in between the cylinders and the case see a considerably higher load when used with alu cylinders that are torqued down to the value normally used with iron cylinders. How do Porsche solve this issue, if it really is one? I'll have to check my documentation... Hans |
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Post by o2koold on Oct 4, 2011 13:18:57 GMT -5
Hans,
I don't think there is an issue to solve, short of a slight compensation on head stud torque. From the thread on the sonerai.net, Gaston had a machine shop locally make his shims. If I remember correctly, they did not have the same clearance the the shims he later purchased for CB performance for his rebuild. If he shows up, I hope he will comment, I could be all wet here. I hope I am not, I have a set of these on a 2276 that I hope to having running in the next few months. Of course, I have been hoping this for the last few months. Where does the money keep going?
Scott R
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hans
Full Member
Posts: 166
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Post by hans on Oct 4, 2011 15:24:39 GMT -5
...Where does the money keep going?... Entropy has it's way, indeed...  |
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Post by maddog on Oct 4, 2011 20:25:10 GMT -5
This sorta reminds me of ABC motors for RC aircraft www.mecoa.com/faq/abc/abc.htmand hearing about shotgun cylinders (choked) to get more compression/power. mb |
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Post by gaston on Oct 11, 2011 20:59:47 GMT -5
Hi Guys
My 2276 is still running very strong and it's been performant and reliable...
Scott was right ,stating the problem I had with my nikasil was not with the barrel but with the narrow shims provided with the kit that cut a groove in the soft magnesium case and hence losening all head studs.
new .250 inch wide shims were installed after the case was refaced and the problem was definitively solved...
I'm really pleased with the performance, at gross weight, it often climbs over 1000 ft/min
but now my variometer is junk and I miss to see the needle in the 1000' min.
PS no more head bolts torque variation with the large shims...
Gaston
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