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Cylinders Run Time & SPI Performance

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Cylinders Run Time & SPI Performance

Post  Iceberg on Wed Jan 02, 2019 12:40 am

I have  .049 cylinders except the 0 cylinder never seen one. Does anyone have any actual stats that show if the SPI cylinders actually improve performance by what amount in RPM? Do any of the 0-8 cylinders last longer than others? Interested to know. What run time is reasonable? I've heard cylinder runnng life is roughly three hours?

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Re: Cylinders Run Time & SPI Performance

Post  balogh on Wed Jan 02, 2019 1:16 am

If kept clean and well lubricated, a COX engine will work for many hours. I read that a COX factory experiment put 400 hours on an engine that still could be started up afterwards, with an electric starter though. https://web.archive.org/web/20170410030959/http://www.mccookfieldfac.com/helpful-info/cox-engines.pdf ...see 2nd page, top right.

I have a COX TD051 with tapered bore cylinder that I counted to have run near 300 hours and still runs very fast. Remember that castor varnish that builds up on the cylinder wall of a used engine can partly make up for the wear of the mating surfaces.

In my experience SPI can add 500-1500 rpm depending on the type of cylinder and other particular conditions.
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Re: Cylinders Run Time & SPI Performance

Post  MBT85 on Wed Jan 02, 2019 2:19 am

I don’t want to sound silly but what is SPI Cylinder?
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Re: Cylinders Run Time & SPI Performance

Post  balogh on Wed Jan 02, 2019 2:25 am

SPI stands for sub- piston induction where the piston skirt bottom clears the exhaust ports when on top dead center, thus allowing a puff of extra air enter the crankcase and mix with the fresh charge that thus can also carry extra fuel in it = added engine power. On the parallel thread "SPI and free porting" you find more on this as well.
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