High Compression Piston Questions

[chad021]

I want to be able to run pump gas without having to mix race gas with it. What is the highest compression I can go without having to do so. Also what kind of piston has worked good and is built best for the price. And is there any kind of jetting work needed to be done? And how much will I gain from it?

 

[87warrior]

the best piston ive had it a je piston its kinda pricey but they are good and hight in compression and run on pump gas

 

[yamarider]

The highest compression you can go is 11:1. The very best pistons are made by JE and CP from what i've heard, but for the money I think a Wiseco is a good way to go, but they only go up to like 10.25:1.

 

[chad021]

how noticeable will the gain be going from a stock warrior to the high comp piston?

 

[yamarider]

You'll probably notice that the engine responds quicker to throttle, and revs up faster because the new piston is lighter. The power gain isn't that great on it though, i'd estimate 1-2 hp, so you might not feel a gain in raw acceleration and speed.

 

[ronbo422]

I've been hotrodding smallblock Chevy's for a few years and my old engine builder stated that 1 point gain in compression, ie 9.2:1 up to 10.2:1, will increase HP by 2-3%. That's not alot on a single-cyl. engine, but in a 500HP smallblock it adds up. A stock Warrior is 9.2:1, I think. Up your compression by almost 2 points with an 11:1 piston (and YES, JE's are awesome pieces) and your looking at a total of 5-6% increase. If stock HP is 20 then you'll gain about 1 hp. Not bad since it's there waiting for you to take it, so to speak. Since HP is nothing but a magical number derived from torque (HP= TorquexRPM/5252) then your torque output will be higher too.
I'd like to build my Warriors 350 up to a stroked 430, utilizing the longest rod possible. A long rod will allow the piston to dwell longer at TDC. The longer the piston dwells at TDC the more "umpf" it'll have once it leaves TDC on the power stroke. A combo like this wouldn't be built for reving to the moon, but it would give you tremendous low/midrange torque.
Then there's always the intake manifold to tweak as well.

~Ronbo

 

[89warrior]

Any one know where i can find a JE 11:1 Piston for the best price?

 

[DeathShadow]

It actually depends on the motor too... YFZs can run all the way up to 12.5:1 with no problems on pump gas...

On another note I found the JE piston to be MORE heavy then the stock cast piston...

 

[chad021]

so with a heavier piston i would be sacrificing a few rpms, would this be really that noticable or would it be forgotten because of the gain

 

[DeathShadow]

so with a heavier piston i would be sacrificing a few rpms, would this be really that noticable or would it be forgotten because of the gain

You would sacrifice the ability to build RPMs as quickly (acceleration). The weight of the piston makes the difference comparable to a bus on the end of your rod vs. a car. The stroker pistons for the Warrior (slipper design) ARE lighter and have a much more shallow skirt area - they are great for reving (the same style in the YFZ and many other high performance motors).

I didn’t notice it to much though.

 

[yfm350rider14]

i run pump gas wiht my 12to1 je piston they said it was fine

 

[boxhead]

The main factor is actual cylinder pressure, some motors may have higher pressures than others. If you need to run race gas you'll exceed about 190 to 200psi. The pressure is on a cold crank also...

 

[warriorman11]

what do you guys think about the je 366 big bore 12:1 piston kit... would i have to mix race fuel with it

 

[imtarnished]

if you would have to mix it would be because of the compression, not because of the displacement (the 366 kit). Though you will hear others say otherwise, 11:1 is the highest you can run safely on pump fuel, from what i've read on here atleast.
~Bill