Andreas Miko

Here are the new figures.


SR16VE pistons in DE motor 11.8 to 1 compression
SR16VE pistons in VE motor 12.5 to 1 compression


I use to say that the SR16VE piston in a VE was about 13.6 to 1 compression. I was making this calculations from the SR16VE N1 head. As we know the SR16VE N1 head is shaved down 1mm to get the compression to 11.8 to 1 vs 11 to 1 compression in the regular SR16VE.

So if we shave 1mm of the top of the SR16VE piston the compression will be about 12 to 1 compression.

You can also get SR16VE pistons and make the valve notches 1mm deeper and that will take out the same amount of metal as removing 1mm of the top of the SR16VE piston so this should also net 12 to 1 compression.

If you do any of these mods when done send the piston to swain to be coated on the top.

To add to this if you make the headgasket .5 mm thicker than stock the compression will be about 12 to 1 compression with SR16VE pistons in a SR20VE motor.

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hachi_boroku

Any reason we can't just do what Nissan did and shave the regular SR20VE head 1mm to bump compression from 10.3:1 to around 11:1? Granted, adjustable cam gears (at least one) will probably be needed to get the cam timing ideal.

tunerguy

And then we end up with a huge squish clearance making the motor more prone to detonation. Not only that but we weaken the piston crown and move the rings higher up on the piston exposing them to more heat.

Why not just get correctly designed pistons that work?

Sabre 200 Gxi

Damn. Another reason why that built motor of mine wasn't performing.

I had 16VE pistons, 1mm deeper valve reliefs, and a 1.5mm head gasket. Miko any idea what CR that probably ended up with?

ps: Is a domed piston like the 16ve or a flat top with pockets better? (Assuming you manage to get the same CR)

Andreas Miko

You dont understand what I am telling you. The crown of the piston does not get thinner. Please take a look at a SR16VE piston and you will understand what I am shaving.

I did also say you could put in the piston and just put a slightly thicker gasket and get 12 to 1.

If someone could get a pick of a SR16VE piston I will try and brake down what I am saying,

Andreas Miko

The compression with the 1.5 mm gasket with Sr16VE pistons would be about 12.2 to 1 compression.

If you made the valve notches 1mm deeper after that the compression would be about 11.5 to 1 compression.

danilo20

Can you run 12.1 comp on sr20ve on 93 octane gas daily driver?

Thanks for the info

Andreas Miko

yes you can

payu

Opssssss....

Andreas Miko

did you put opsss

of did you mean oopssss

payu

you got it....
I am not a wizard jejejeje......

CenturyI

I was just about to ask if you can run 12:1 compression on 93. I think this whole thread was a sign. haha.


Thanks Miko

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Andreas Miko

I think the best options to get 12 to 1 compression with SR16VE pistons will be.

shaving 1mm off the top of the SR16VE piston

or

Putting on a headgasket that is .5mm thiker.

CenturyI

Would these have any clearance issue if I upgraded the cams? Or would the 1mm off of the top take care of that?

Andreas Miko

The top of the piston has nothing to do with valve notches, The valve notche give the clearance and the Sr16VE pisotn was designed with the deepest valve notches because it was designed for the higher lift cams of the N1 and the shaved head of he N1 because the valves got closer because because of it.

tunerguy

Please specify if the fuel octane rating is ron or mon posting as lots of countries get 93 RON which is similar to like 89 PON in the USA.

There is now way on Gods earth that a engine will run on more than 11.5:1 on the 93 RON we have and even then you are pushing it. Det will set in when the motor builds a bit of carbon.
Mapped a car yesterday on 93 Ron compression is around 11.5:1 and it pings like a bitch with more than 12deg adv under 2000rpm, max timing at 8000rpm 24 deg.

FastNX

Can you please show your calculations? Or at least the cc numbers you used to calculate?

I did this and I got 13.5:1.

I took the SR16VE as 11:1 and then changed the displacement and got 13.5:1 for 499.5cc displacement per cylinder. I used 41.8cc as the combustion chamber volume.

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mpg9999

They are talking about PON (RON + MON /2).

Andreas Miko

I am not where I have my calculations at this moment, but look at this.

DE 9.5 to 1 piston in a VE is 10.3 to 1 ( These are facts )
Standard SR20VE piston is 10.3 to 1 ( These are facts )

SR16VE piston in a DE is 11.7 to 1 ( These are facts )

20V piston is 11 to 1 ( still has a slight dish and some valve reliefs )
DE 10 to 1 in a VE is 11.3 to 1 ( completly flat no notches )


There is a direct corolation between the VE and DE which is about .8 more in compression.

If the SR16VE piston is 11.7 to 1 in a DE ( which is the thruth, example S14 200HP Autech car runs the SR16VE pistons with this compression.

You should get 12.5 to one with these pistons in a SR20VE.

I also got intouch with Clark Steppler about my finding and he backed up my figures with his calculations.

I only found this out by getting a few pistons and started shaving 1mm of of them.

#1 piston 1 mm off the dome
#2 piston 2 mm off the dome
#3 piston 3 mm of the dome ( this left me with a flat top piston with deep valve notches

The #3 piston with the valve notches added in had more ccs to it than the 20V piston because the valve notches are so deep in the SR16VE pistons