Engine Displacement - Cylinder Boring for New Pistons

[Gotch]

His compression ratio will also increase, that should be good for a couple of more ponies.

Sponsored

 

[Myx]

His compression ratio will also increase, that should be good for a couple of more ponies.

I had no idea. Looking for a calculator to figure out the theoretical increase in compression ratio now. ? Je Piston's how to is a little involved though.

How to Calculate Engine Compression Ratio and Displacement

 

[Gotch]

I had no idea. Looking for a calculator to figure out the theoretical increase in compression ratio now. ? Je Piston's how to is a little involved though.

How to Calculate Engine Compression Ratio and Displacement

It won’t be much, a couple of 10ths increase. ECU should be able to compensate even with tune. Just something to watch when you get your motor back together.

If you want to know exactly, you’ll need to find out the cc of the combustion chamber and add the thickness of the torqued head gasket.

 

[Oddwayne]

His compression ratio will also increase, that should be good for a couple of more ponies.

I thought compression would only change if you change the rod length, bigger dome on the piston, or taking off material from the head or block. How does the oversized piston increase cr? I’m not familiar with that method.

 

[Gruber]

I thought compression would only change if you change the rod length, bigger dome on the piston, or taking off material from the head or block. How does the oversized piston increase cr? I’m not familiar with that method.

of course it won't, unless the cylinder is only honed as far as the rings go.

If this is done just so that the cylinder is not enlarged at all in the dead space (above the cylinder at TDC) then....

Assuming 10.6 is the geometric compression ratio and the displacement volume is 1498 cc, the dead space is 156.04 cc.
If the displacement volume only is now increased to 1519 cc, the new compresion ratio will be 10.73, an increase of 1.27% over the stock. This will require a tiny bit more octane to keep the knock and ignition exactly as before, and then there will be a tiny increase of torque/power, but I expect it will be less than 1.27%, because it seems like the relative power increase should be less than the relative increase of the compression ratio.
I'm sure someone has figured how much increase of max power can be expected from a given increase of the geometric compression ratio.
If the fuel octane is not increased, the ignition would retard a liitle, and the increase in power could be very negligible.

 

[Oddwayne]

of course it won't, unless the cylinder is only honed as far as the rings go.

If this is done just so that the cylinder is not enlarged at all in the dead space (above the cylinder at TDC) then....

Assuming 10.6 is the geometric compression ratio and the displacement volume is 1498 cc, the dead space is 156.04 cc.
If the displacement volume only is now increased to 1519 cc, the new compresion ratio will be 10.73, an increase of 1.27% over the stock. This will require a tiny bit more octane to keep the knock and ignition exactly as before, and then there will be a tiny increase of torque/power, but I expect it will be less than 1.27%, because it seems like the relative power increase should be less than the relative increase of the compression ratio.
I'm sure someone has figured how much increase of max power can be expected from a given increase of the geometric compression ratio.
If the fuel octane is not increased, the ignition would retard a liitle, and the increase in power could be very negligible.

I don’t think you would need to go up in octane for .1 increase in cr.

 

[bcrichster]

I had no idea. Looking for a calculator to figure out the theoretical increase in compression ratio now. ? Je Piston's how to is a little involved though.

How to Calculate Engine Compression Ratio and Displacement

I like using this one, it's been decent so far. And also Honda engine specific!
https://www.zealautowerks.com/horsepower.html

 

[kshawn]

Nothing had to change about my tune when I switched to a built block with JE pistons

 

[kshawn]

I’ve had .25 bigger pistons in my h22 when I refreshed it, it did not do anything. It’s so small a difference. In theory yes the cylinder are wider but it’s very neglible. It’s just to have a smooth cylinder wall surface. On a side note I would like to see more on this topic. Once people start to really bore out these blocks and throw in bigger cams, we’ll start seeing much bigger builds without meth, c16 ect.

I want to see what those cams do when you port. So far they seem to do nothing with the stock head.

 

[Gruber]

I don’t think you would need to go up in octane for .1 increase in cr.

Of course you wouldn't. You only would if you wanted to take full advantage of your theoretical power increase of maybe about 1 hp... those with extremely sensitive butts and those who measure acceleration to a hundreth of s second may have a reason...

 

[Myx]

Of course you wouldn't. You only would if you wanted to take full advantage of your theoretical power increase of maybe about 1 hp... those with extremely sensitive butts and those who measure acceleration to a hundreth of s second may have a reason...

You have described me to a T. Or to a hundreth of a second, depending on how you look at it.
I literally test my mods at the track to look for 1/100th of a second improvements and gains/loses in mph by .5 mph increments.

 

[CAPTS]

not only pistons, it'll be much better with the rods too & you should get 10:3:1 instead of 10:6:1

 

[Myx]

not only pistons, it'll be much better with the rods too & you should get 10:3:1 instead of 10:6:1

I have a set of Saenz rods in as well.

I actually wanted to weigh the stock pistons and connecting rods vs the JE Pistons and Saenz Rods for comparison. Just to have the data available and share. I am a huge fan of reducing rotating mass. It won't benefit me as much with engine internals as it would a manual transmission because once I hit my rpm peak, the engine will continue to rotate at the same speed (Rather than falling to a lower rpm in the next gear and having to accelerate all over again to peak rpm).

Still, that first initial speeding up of the engine to peak rpm is very important to me personally. Not so much for most people.

 

[Gotch]

If you are lightening the rods and pistons, the crank needs to be rebalanced or you’ll stress out the stock crank. Same goes if mass is increased on rods or pistons.

 

[Oddwayne]

I want to see what those cams do when you port. So far they seem to do nothing with the stock head.

On na motors, having bigger cams don’t do much unless your increasing the cr, to some degree of course, but I’m not sure about boosted applications. Hopefully people will start venturing in internal work instead of using alternate fuels. Fingers crossed. I’ve asked those at Brian crower and there’s a shop working with them now with something

Sponsored