Preferred Pistons

[Metallic36]

I have my stock ecu right now, nothing else because I'm breaking in the engine still. Just keeping tabs with an AEM UEGO wideband.

So if I was staying with a stock ecu for a while are we saying you need to go with a 9:1 CR?

 

[neox.286]

yea it will run with the stock ecu, just keep a good eye on your air/fuel ratios as youll be adding more air into the mixture than fuel (cause you are essentially making the compression chamber larger)

it shouldn't be too drastic of a change, but I wouldn't be able to say because I dont have that setup

 

[shane02pro5]

Not at all...you would barely know the difference.

(friday)

So if I was staying with a stock ecu for a while are we saying you need to go with a 9:1 CR?

 

[i like speed]

(cause you are essentially making the compression chamber larger)

I thought it kept the same displacement just made the top of the piston closer to the head at tdc? I'm learnig too I just wanna make sure i understand it right.

 

[neox.286]

I may be wrong in my understanding of it, since all of my understanding is from learning on my own and not from any kind of professional schooling

however....when they make lower compression pistons you are changing the top of the piston to a different shape (or placing it closer to the head)....when you are compressing it doesn't matter if the shape is flat, rounded, or whatever...8.5:1 is 8.5:1 compression

however, because you are not changing the length of the rod (only the piston) then the only way that you can make 8.5:1 compression instead of 9:1 is by not moving the piston as close to the head (or changing the shape of the top of the piston)....meaning the compression volume has to change

(this is from looking at it from a mathematical perspective, so it may not be accurate in here...if I am wrong, someone please correct me there)

after typing all that out, I guess you are right...it would have to change displacement....so someone please verify the above?

 

[low_psi]

None of Victor's Proteges have ever had built motors.

Sam built and installed a motor into his own car though.

As for compression ratios, the 9:1's are fine for most applications. If you're going to run lots of boost on a larger turbo(T3 turbine and larger), 8.5:1 would be the better choice.

 

[yashooa]

Sam told me once that he had several engines come to him that needed rebuilt, and they were all using Arias. I had planned to go with Arias, but after that I chose the CP pistons because a lot of people on here have had good success with them.

I have the Arias and have not had a single issue. This has been debated to death in another thread. My squirters are fine it all comes down to who builds the engine and who does the machine work. I had excellent service on both of those points and my engine is perfect. I have boosted to 21PSI so far with zero detonation. I have an MPI, two Cobra Mustang injectors and a J&S.
I do have to turn the J&S up in the heat but I can back it down when it is in the 70's and below.
My Arias were ceramic coated and dry filmed on the side. My turbo is supposed to be good for 24PSI I am edging closer to that level. They do slap in very cold weather I just make sure to warm the engine up for 2 mins before I drive it. In warm weather they do not make any noticeable noise.

I have the 8:5:1 ratio and I have not noticed a drop in power or much difference in MPG. I get about 34MPG as long as I stay out of it. When I hammer it and the extra injectors come on line it goes down dramatically.

 

[neox.286]

None of Victor's Proteges have ever had built motors.

Sam built and installed a motor into his own car though.

As for compression ratios, the 9:1's are fine for most applications. If you're going to run lots of boost on a larger turbo(T3 turbine and larger), 8.5:1 would be the better choice.

thats what I thought, but his mod list on his car's website (as linked prior in this thread) shows otherwise?

 

[JDM Sam]

I see a lot of wrong, he said she said statements.

1. I built block in my car last year.
2. New Arias pistons are manufactured differently from the old sets. They will not hit the oil jets now.
3. Stock ECU works on both 8:5:1 and 9.1:1
4. 8.5:1 makes less power per psi than 9.1:1.
5.You can run more boost on 8.5:1 on pump gas vs 9.1:1.
6. 8:5:1 you can run 20+ PSI, you better have a big turbo for this or you will be blowing hot air.
7. 9.1:1 you can run max 19psi depending on your tune and octane.
8. If you want the right specs of said cars hit up www.*************.com. They have used every built engine setup possible for the FS.
9. Small turbo on a built motor is fine for a street car. Stock turbo can run up to 16-18 psi and be quick.
10. You can lower the compression slightly using a thicker MLS gasket.

 

[neox.286]

hey sam, do you know if pirana's msp had a built motor in it?

 

[low_psi]

it did not have a built motor. engine parts were listed on the site for his mod list because he had purchased them but a motor was never built due to Victor parting out the car and selling it.

 

[neox.286]

that's what I thought haha, thanks bro =)