group buy! Wiseco Pistons

[xtreme 2]

Yea. Your goal is to have high compression, but not too high. If you are boosting the lower your compression to start the more boost you can run...

[aveodude]

If you want to stroke the motor, need larger pistons...

Not quite. You will want a different crank to stroke the motor. Larger(taller) pistons just raise the comp ratio. Larger(around) pistons with the proper machining is boring it.
And the biggest advantage of aftermarket pistons is that they are forged and damn strong. With forged connecting rods, you can throw anything at them with a proper tune without them breaking.

[gse_turbo]

+1 thanks everyone,

just as a quick recap...

• bore is the size of the pistons diameter, the larger you go the more PH the motor is capable of.

• stroke is the distance the piston travels up and down as affected by the crank (and rods), the longer you go the more torque the motor is capable of

both of these increase the displacement. by going to max bore or max stoke can raise the displacement by 0.3-0.4, basically making the 1.6 a 1.8 or 1.9 if not bigger. this can be see in the '08 Saturn Astra, it uses the same block as the 1.6 but it is a 1.8 (turbo).

before anyone gets crazy ideas, to use the turbo manifold from the Astra you would have to swap everything above the block surface, wiring and computer. the '08 1.8T is also a VVT motor which is even a bigger headache.

• compression ration also affects HP. the higher the better (in all circumstances), the tighter that the air/fuel is compressed the bigger the explosion (which is what makes HP).

now the high/low compression discusion...
for an 'all motor' application 10.0" or 11.0:1 is pretty common in non-econocar application, it provides great HP with little affect on gas mileage. a race motor will see numbers of upwards of 13.0:1, 14.0:1 and higher.
for turbo applications 8.5:1 is the most common in nearly all turbo cars. in a race turbo or turbo diesel application you can see numbers like 9.5:1 and 10.0:1.

the ONLY reason a specific CR is chosen is to prevent detonation, thats all.
the idea is that you want to match the compression ratio to the type of fuel that you will be using. the higher the octane the more resistant it is to predetonation there for if you use a 91, 93 octane or higher (race gas) then using 9.5:1 is fine and you will get more HP then if you used 8.5:1

the ONLY reason the manufacturers use 8.5:1 pistons in a production car is so the owner can run the lowest 85 octane and the engine will survive.

also if you use higher compression pistons on a turbo application. then you can use less boost then a lower compression turbo application and get close to the same HP numbers.

long story short, if you plan on enjoying your car on a daily bases then go with 8.5:1 on a turbo or 10.5:1-11.0:1 for all motor.

if you plan on running down the drag strip and that's all then go with 9.5:1 and higher and high octane.

basically you are not only affecting HP but longevity of the motor.

[gse_turbo]

wow I type slow! some three or four post went up in the time it took me to type that

[gse_turbo]

And the biggest advantage of aftermarket pistons is that they are forged and damn strong. With forged connecting rods, you can throw anything at them with a proper tune without them breaking.

+1 many people are surprise to hear that when someone says "I through a rod" that its not the rod that broke but the bolts.

upgrading to ARP rod bolts can be just as big of an improvement as aftermarket rods.

[aveodude]

And the biggest advantage of aftermarket pistons is that they are forged and damn strong. With forged connecting rods, you can throw anything at them with a proper tune without them breaking.

+1 many people are surprise to hear that when someone says "I through a rod" that its not the rod that broke but the bolts.

upgrading to ARP rod bolts can be just as big of an improvement as aftermarket rods.

For real. While you are in there, you might as well go for the best stuff. Nothing like building a $4K motor to have a $20 part break and make it a boat anchor

[gse_turbo]

VERY true!

[khan4rtist]

damn im glad engine internals are getting made finally....maybe we can get this motor to spin to 8k

[g0ast]

OK gse, you answered my question but made me raise another question...

Say I was to turbo my car, and I got those pistons and changed the CR, would it be possible for me to somehow arrange it so I could still use Regular gas without it detonating?

I know I'd be spending ~$3000 for the turbo kit and pistons but I'm still too cheap for pay high gas prices :P


Also on a side note, I just want to ask this: Are aftermarket headers used with a turbo because of the need for a flange to attach the turbo on or is it something else?

[aveodude]

OK gse, you answered my question but made me raise another question...

Say I was to turbo my car, and I got those pistons and changed the CR, would it be possible for me to somehow arrange it so I could still use Regular gas without it detonating?

I know I'd be spending ~$3000 for the turbo kit and pistons but I'm still too cheap for pay high gas prices :P

Also on a side note, I just want to ask this: Are aftermarket headers used with a turbo because of the need for a flange to attach the turbo on or is it something else?

With a good tune, you can boost a 9.0:1 comp ratio and keep it from detonating. It is ALL about the tune. The lower comp does make it easier.

Turbo cars use exhaust manifolds instead of headers. There are 2 types log and tubular. A log mani looks like this



A tubular looks like this




The tubular one is better because it builds the velocity of the exhaust gas to spool the turbo faster. Down side is that not all cars have to room to fit it.