Thread: SR16VE pistons, how far can I skim off the top?

So, I been searching on the forums all day, trying to find some info on skimming pistons. I keep seeing posts saying sr16 (non1)'s are 13:5.1 or 13:2.1 in a ve. And n1 pistons are 12:5.1 or 13:1.
Just looking for the true info..

Also, I read on a thread that skimming 1mm drops .5 of compression in a ve. So skimming 1mm off a 86mm 13:1piston will make it 12:5.1?

The true reason for this post is this, I now have sr16(non n1) pistons in my ve. Im looking to drop my compression (shooting for 12:1-12:5.1. I'm trying to avoid buying new pistons. Is it safe to skim 2mm of the top of a sr16 piston? Will it completely ruin or weaken the piston? I know I'm not the first one that ever thought about it.

Any ideas or advice would be greatly appreciated.

Sorry, but I just couldnt find any info on this anywhere.

Compression ratio is exactly that, a ratio. If you skim 1mm off a piston that started with 2:1 you are not going to have a .5 change. Likewise if you skimmed 1 mm off a piston with 40:1 compression ratio you might get 20 point reduction.

You need to find the volume of the combustion chamber, the total volume of the piston dome, and then calculate the total volume of material removed.

Or you could ask someone who as already done it and can give you some anecdotal evidence.

worth a go. put in your figures.

Engine Size and Compression Calculator

41.8cc sr16/20 chamber volume
sr16ve piston crown 9.6cc
sr16n1 piston crown 7.5cc

put in your chosen head gasket in inches not mm.

n1 pistons should be around 13 to 1 . real world i always thought they were about 12.5 to 1.

You can use them just make the notch for the oil squirter and you are set just make sure to have 93 octane gas and tune the ecu for them!!

Thank you guys for the info. I know it depends what kind of piston and head you are using in order to calculate the exact compression. I just dont have the tools nor knowledge to measure these type of things. Payu, Ive read on some of your posts as well, I know you guys been running straight 16ve pistons on 93 but I was want to lower mine just in case I go out of state for a week or two and they dont have 93. This is my daily driver so I need something more reliable.

I have seen two engines here in nz crack pistons that have been shaved. (one was coated) weather if its because they were shaved is a different story.

If it was my build i would hunt for n1 pistons rather than skim the sr16ve ones

Depends on where the crack is at and how it went throughout the part. Got any neat pictures?

It can be tuned on 91 too!!

Ive shaved and notched sr16 pistons... the notched pistons lasted much longer

also I measured my sr20ve chamber to be 40.5cc's at the time. so err on the side of caution when doing "calculations" :thumbup:

Did you use a standard metal ve gasket?