Thread: Let's talk Big Bore/Short Stroke vs. Small Bore/Long Stroke Boosted

Realized this today Cory, I did some measuring on the standard pistons I have. They are roughly 32mm from center of wrist pin to the top of the piston when I believe the most I can use is 29mm.

For the stock engine it would be :
136.3(rod) + 43(half stroke) + 32(compression height) = 211.3mm

My motor would be 136.3+46+(X)=211.3
Meaning that the highest compresion height I could use is 29mm. Is this correct?

My next question is can I mill the dish out of my piston and just make it a slug to reach this compression height? The dish on these pistons is roughly about 3mm deep. Of course I would probably still have to have valve reliefs cut as well. I guess I need to see exactly how much material there is in the center of the piston and see if valve reliefs would leave enough material to play with.

Any 4 clylinder making that power or close to that power is going to be a very touchy setup def not for the faint hearted

The RWD SR guys are the ones that like to go stroker motor for whatever reason...but thats because they dont like or know how to set up their heads properly to rev out to 8500-9k. Here is my take. It all depends on what powerband you want to have. Good thing about stroker motors of course is the increased displacement without the real need to bore or sleeve the motor. Helps spool time, don't need to rev as high to make a decent powerband which can help the motor last longer and less worries about grenading oil pumps or having harmonics issues and bearing issues and other issues related to engine oiling.

However be prepared to limit the rpms alot lower such as about 7500 at the most on a 92mm stroke.

Nothing wrong with stroking a motor.

I will say this though, most of the evo guys that did 2.4L strokers on their 4g63's went back to 2.0L's due to having the capability to rev higher and give them a longer powerband and also with their gearing they needed it when getting up in the traps.

Doing some math for future reference. You math guru's correct me if I'm wrong.

Basics:

I was trying to figure out how much compression I would have if I used factory rods with the 92mm crank and what piston I could get away with. Our motor is 1998cc's so 1998/4=499.5cc's per cylinder. I want to find how many cc's I'm adding by going with a 86.5mm bore, so I need to find out how much .5mm=cc's. 86/.5=172 so 172cc's=.5mm. .5mm=2.904cc's. With this being said, I'm adding 2.904(4)=11.616cc's. So, just with a 86.5mm piston your motor will now be 2009.6.

I've been looking at stroker kits and what rods/pistons they are running. All of the pistons are custom of course with the pin height being higher making for a lower compression height. Most of the 92mm strokers use a 5.364 rod while our factory rods are 5.366, a .002 difference which isn't much. However, I'd like to keep my compression as high as possible and every little bit helps. I've been looking at a set of wiseco's to base things off of. They are:

Engine: SR20DET + 92mm Stroker Crank
Compression Ratio: 9.0:1
Dome CC: -17
Gasket Thickness: 0.036
Head CC: 45
Pin Size: 22
Compression Height: 28.95
Rod Length: 5.364
Stroke: 3.622
Bore: 87.00
Bore Size: +0.040

I'm trying to find out a way to get closer to 11:1 compression, or at least 10.5 without going custom pistons. I'm trying to find a way to figure out exactly how to find what my compression will be with the 5.366 rod, 92mm stroke, these Wiseco's, and the thinnest headgasket possible.

I'm still contemplating maybe using the 86.5 pistons I have and milling the tops. There is roughly 2mm of dish on them which would put me at 30mm compression height and I'm pretty sure I can take another 1mm off and still have plenty of material and keep my top compression ring.

I've been doing more research and from what I've read, you don't want less than .180 in the thickness of the piston top. I'm going to do some measuring when I get the chance and see if it's possible to mill the tops of these pistons. I like the idea of keeping my top compression ring as well. I could run a thicker headgasket to help but that's last on my list.

Just get a set of custom pistons, problems all solved ...

free machine work...why?