Anyone done an A/B dyno test with flipped pistons?
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Anyone done an A/B dyno test with flipped pistons?
Interested if anyone has actually compared actual dyno runs with the old 'flip the pistons around' trick
I'd think it maybe would effectively increase the R/S ratio and aid with filling the cylinders at higher rpm, but would that be enough to overcome the added dynamic load.
no way to really know unless someone dyno'd it
I'd think it maybe would effectively increase the R/S ratio and aid with filling the cylinders at higher rpm, but would that be enough to overcome the added dynamic load.
no way to really know unless someone dyno'd it
Re: Anyone done an A/B dyno test with flipped pistons?
Tested it. It makes zero difference. Waste of time.
There's a Mahle white paper, "Pistons and engine testing," that goes over optimal piston offset in great detail. Suffice it to say that any modern piston has been optimized by the makers and is consistent with what we found first hand. Page 154.
There's a Mahle white paper, "Pistons and engine testing," that goes over optimal piston offset in great detail. Suffice it to say that any modern piston has been optimized by the makers and is consistent with what we found first hand. Page 154.
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Re: Anyone done an A/B dyno test with flipped pistons?
Did that very test for Chrysler in the early 90's using a 360 Magnum engine. Centered, .030" offset, .060" offset and .090" offset.ELS wrote: ↑Sun May 29, 2022 7:47 pm Interested if anyone has actually compared actual dyno runs with the old 'flip the pistons around' trick
I'd think it maybe would effectively increase the R/S ratio and aid with filling the cylinders at higher rpm, but would that be enough to overcome the added dynamic load.
no way to really know unless someone dyno'd it
Cylinder wall friction is slightly different in most cases so, the lower the rod ratio the more it will differentiate.
There is a power difference but, it is minimal ... certainly not enough to reverse the pin offset and listen to the pistons slap and hurt the skirt.
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Re: Anyone done an A/B dyno test with flipped pistons?
well I was most worried about the added friction.Walter R. Malik wrote: ↑Sun May 29, 2022 9:15 pmDid that very test for Chrysler in the early 90's using a 360 Magnum engine. Centered, .030" offset, .060" offset and .090" offset.ELS wrote: ↑Sun May 29, 2022 7:47 pm Interested if anyone has actually compared actual dyno runs with the old 'flip the pistons around' trick
I'd think it maybe would effectively increase the R/S ratio and aid with filling the cylinders at higher rpm, but would that be enough to overcome the added dynamic load.
no way to really know unless someone dyno'd it
Cylinder wall friction is slightly different in most cases so, the lower the rod ratio the more it will differentiate.
There is a power difference but, it is minimal ... certainly not enough to reverse the pin offset and listen to the pistons slap and hurt the skirt.
and also something I read in a book called an oil wedge, basically when the piston rocks to one side, if there's a ton of oil on the cylinders it can form a wedge and stal the piston... sounds real bad, but the book didn't elaborate on what happens when that happens, just that it shouldnt
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Re: Anyone done an A/B dyno test with flipped pistons?
Reverse offset pins present less cylinder wall friction. Some inline engines actually offset the crankshaft instead.ELS wrote: ↑Sun May 29, 2022 10:21 pmwell I was most worried about the added friction.Walter R. Malik wrote: ↑Sun May 29, 2022 9:15 pmDid that very test for Chrysler in the early 90's using a 360 Magnum engine. Centered, .030" offset, .060" offset and .090" offset.ELS wrote: ↑Sun May 29, 2022 7:47 pm Interested if anyone has actually compared actual dyno runs with the old 'flip the pistons around' trick
I'd think it maybe would effectively increase the R/S ratio and aid with filling the cylinders at higher rpm, but would that be enough to overcome the added dynamic load.
no way to really know unless someone dyno'd it
Cylinder wall friction is slightly different in most cases so, the lower the rod ratio the more it will differentiate.
There is a power difference but, it is minimal ... certainly not enough to reverse the pin offset and listen to the pistons slap and hurt the skirt.
and also something I read in a book called an oil wedge, basically when the piston rocks to one side, if there's a ton of oil on the cylinders it can form a wedge and stal the piston... sounds real bad, but the book didn't elaborate on what happens when that happens, just that it shouldnt
http://www.rmcompetition.com
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Specialty engine building at its finest.
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Re: Anyone done an A/B dyno test with flipped pistons?
I think the advantages here are not a power difference in a single A-B dyno test, but how the pistons / rings / bore hold up over thousands of miles. Test an engine with them flipped after 3000 racing miles, and you may see a difference.
-Bob
Re: Anyone done an A/B dyno test with flipped pistons?
Here's the Mahle pdf. They've tested it all. Page 154 is the info on pin offset, along with graphs of various pin offsets with the frictional differences.
https://fdocuments.in/document/pistons- ... tml?page=1
https://fdocuments.in/document/pistons- ... tml?page=1
Re: Anyone done an A/B dyno test with flipped pistons?
thanks! I was looking for that and couldn't find it.dannobee wrote: ↑Mon May 30, 2022 6:47 pm Here's the Mahle pdf. They've tested it all. Page 154 is the info on pin offset, along with graphs of various pin offsets with the frictional differences.
https://fdocuments.in/document/pistons- ... tml?page=1
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Re: Anyone done an A/B dyno test with flipped pistons?
If I am not mistaken, Engine Masters also tested this and found no real substantial difference
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Re: Anyone done an A/B dyno test with flipped pistons?
This would he an A-B test, looking at the Mahle data and other sources, I suspect the difference as I said above would be after running. I heard Ilmor tests the NASCAR LS engine out to 20k miles. I bet you start seeing differences when you start carrying mileage out like that, or in. LeMans engine or even NASCAR engines with the mileage they need.malibuguy79 wrote: ↑Tue May 31, 2022 11:20 pm If I am not mistaken, Engine Masters also tested this and found no real substantial difference
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Re: Anyone done an A/B dyno test with flipped pistons?
That thing is INCREDIBLE... Answered my question on how much piston oil squirters reduce piston temps in about 20x more detail than I was asking.dannobee wrote: ↑Mon May 30, 2022 6:47 pm Here's the Mahle pdf. They've tested it all. Page 154 is the info on pin offset, along with graphs of various pin offsets with the frictional differences.
https://fdocuments.in/document/pistons- ... tml?page=1
Saving THAT one for later...
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Re: Anyone done an A/B dyno test with flipped pistons?
Same as long rod v/s whatever.hoffman900 wrote: ↑Wed Jun 01, 2022 10:51 amThis would he an A-B test, looking at the Mahle data and other sources, I suspect the difference as I said above would be after running. I heard Ilmor tests the NASCAR LS engine out to 20k miles. I bet you start seeing differences when you start carrying mileage out like that, or in. LeMans engine or even NASCAR engines with the mileage they need.malibuguy79 wrote: ↑Tue May 31, 2022 11:20 pm If I am not mistaken, Engine Masters also tested this and found no real substantial difference
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Re: Anyone done an A/B dyno test with flipped pistons?
Looks like some people have good results
https://www.rideapart.com/news/256853/f ... explained/
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https://www.rideapart.com/news/256853/f ... explained/
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Re: Anyone done an A/B dyno test with flipped pistons?
Off set crank to cylinder centerline has been used for a long time. Can't be all that great, not everybody adopted it, I'd imagine preignition and detonation damage would be more significant with the crank offset. Also rising combustion pressure would have a hard time chasing the faster cylinder enlargement with the piston accelerating so quickly from min volume.
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Re: Anyone done an A/B dyno test with flipped pistons?
It was very informative.NewbVetteGuy wrote: ↑Wed Jun 01, 2022 7:01 pmThat thing is INCREDIBLE... Answered my question on how much piston oil squirters reduce piston temps in about 20x more detail than I was asking.dannobee wrote: ↑Mon May 30, 2022 6:47 pm Here's the Mahle pdf. They've tested it all. Page 154 is the info on pin offset, along with graphs of various pin offsets with the frictional differences.
https://fdocuments.in/document/pistons- ... tml?page=1
Saving THAT one for later...
Adam