Some thoughts regarding SR16VE pistons on other SRs
Hi everybody, long time no posting.
I was working on a SR16VE engine stroked up to SR20VE. The plan is to use the stock SR16VE pistons to gain some CR, but it is limited to pump gas only, which in my country up to a CR of 12:1 is almost reasonable. (97 OCTANE RON standard)
Since there is a lot of opinions regarding the true CR's and dimensions of the SR16VE pistons, i decided to model it on solidworks to get an educated guess
After an afternoon of drawing the piston's crown on Solidworks, this is what i get:
On first place, i built the model based on photos uploaded to solidworks and actual piston measurements (had it on my desk)
I built first a crown modeling from the upper line of the fire ring up to the piston dome's end. Then i build a reference volume from the same upper ring to the pistons base plane (this is the part of the pistons that lines up with the block surfaces)
Since the dome and the valve reliefs sum and rest volume to the total of reference volume, the difference between the crown volume and the reference volume would show the actual dome/valve reliefs group as a total and definitely number.
After modeling, this were the results:
Because this is a representation of the actual piston, numbers can differ a little, but it's close enough to estimate.(For you OCDs ones and perfectionist, I feel your pain... damn you heisenberg!)
Finally, Having the correct numbers it was time to estimate possible CRs!
Since i don't have the actual number for the compressed oem gasket thickness, i tried to figure out how much could be.
I measured a used one, it gave me 1.4mm, but under load, should reduce to something close to 1 mm.
Cylinder Head Chamber size was measured and give me a solid 41.8cc (41800 mm^3)
With these numbers on mind, it was time for excel figures...
First I tried to check for the SR16's oem CR;
YES!, very close to the official declared number
Then it is time for a SR20VE;
Ouch! waaaaay to high for pump gas, maybe for you low budget Q16/C16's guys...
So we had 2 options here;
Shave the pistons or using a bigger Gasket
Shaving Pistons:
Pro's: Cheap as hell!
Con's: weaker piston. (OEM has 6-7mm of thickness on the dome area)
In my experience, going up to 1.5 mm is safe for a SR20DE engine, however VVL engines have smaller chambers which leads to higher CR's
If you wanna go this way, is under your own risk, you will have 4.5mm of thickness on the piston head. Anyway, this is the result;
This could be close enough, but piston strength may be an issue. You are free to try by yourself and share the results!
In the otherwise, we can go with a bigger head gasket:
Pro's: More expensive solution than shaving, but not really expensive.
Con's: Will affect a little the cams timing.
Using a 2mm gasket, this was the result;
That's the number we were looking for!
So finally, i have a clear address to head to.
Hope it helps to someone planning going from 1.6 to 2.0 with the same pistons.
PS:
Here is the EXCEL file, so you can check by yourself what suits better for you...
http://photos.turbotronics.cl/SR16%20PISTON%20CALCULATOR.ods
Greetings!
I was working on a SR16VE engine stroked up to SR20VE. The plan is to use the stock SR16VE pistons to gain some CR, but it is limited to pump gas only, which in my country up to a CR of 12:1 is almost reasonable. (97 OCTANE RON standard)
Since there is a lot of opinions regarding the true CR's and dimensions of the SR16VE pistons, i decided to model it on solidworks to get an educated guess
After an afternoon of drawing the piston's crown on Solidworks, this is what i get:
On first place, i built the model based on photos uploaded to solidworks and actual piston measurements (had it on my desk)
I built first a crown modeling from the upper line of the fire ring up to the piston dome's end. Then i build a reference volume from the same upper ring to the pistons base plane (this is the part of the pistons that lines up with the block surfaces)
Since the dome and the valve reliefs sum and rest volume to the total of reference volume, the difference between the crown volume and the reference volume would show the actual dome/valve reliefs group as a total and definitely number.
After modeling, this were the results:
Because this is a representation of the actual piston, numbers can differ a little, but it's close enough to estimate.(For you OCDs ones and perfectionist, I feel your pain... damn you heisenberg!)
Finally, Having the correct numbers it was time to estimate possible CRs!
Since i don't have the actual number for the compressed oem gasket thickness, i tried to figure out how much could be.
I measured a used one, it gave me 1.4mm, but under load, should reduce to something close to 1 mm.
Cylinder Head Chamber size was measured and give me a solid 41.8cc (41800 mm^3)
With these numbers on mind, it was time for excel figures...
First I tried to check for the SR16's oem CR;
YES!, very close to the official declared number
Then it is time for a SR20VE;
Ouch! waaaaay to high for pump gas, maybe for you low budget Q16/C16's guys...
So we had 2 options here;
Shave the pistons or using a bigger Gasket
Shaving Pistons:
Pro's: Cheap as hell!
Con's: weaker piston. (OEM has 6-7mm of thickness on the dome area)
In my experience, going up to 1.5 mm is safe for a SR20DE engine, however VVL engines have smaller chambers which leads to higher CR's
If you wanna go this way, is under your own risk, you will have 4.5mm of thickness on the piston head. Anyway, this is the result;
This could be close enough, but piston strength may be an issue. You are free to try by yourself and share the results!
In the otherwise, we can go with a bigger head gasket:
Pro's: More expensive solution than shaving, but not really expensive.
Con's: Will affect a little the cams timing.
Using a 2mm gasket, this was the result;
That's the number we were looking for!
So finally, i have a clear address to head to.
Hope it helps to someone planning going from 1.6 to 2.0 with the same pistons.
PS:
Here is the EXCEL file, so you can check by yourself what suits better for you...
http://photos.turbotronics.cl/SR16%20PISTON%20CALCULATOR.ods
Greetings!
Last edited by PuPPiesOnAciD
on 2016-01-28
at 03-18-18.
Originally Posted by nismos13silvia 
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