What is the advantage/disadvantage of going with 9:1 pistons compared to 8:1 pistons?

[NASTYDSM]

I have heard many different opinions on which pistons are the best to go with. Can someone who is knowledgable please give me some advice? My mechanic says for me to go with 8:1 or 8.5:1 so i can run higher boost but other mechanics say to go with 9:1 so i don't have to run higher boost levels. What are the advantages /disadvantages of each? I will be using the 1G rods and probably Weisco or Ross pistons(because of their low cost) I am not trying to skimp out by getting these cheaper pistons, I just simply don't have that kind of money right now. By the way, if anyone has some pistons they want to sell me I am definately looking for a set. (they must be standard bore size) **Take a look at my mod list to get an idea of what i will be working with.**

 

[CBgst]

As far as I know you can still run higher boost with higher compression. The only difference is your tuning window is smaller with higher compression.

 

[Wilsonman02]

The 9:1 will give you quicker boost response, but u wont be able to run higher boost levels, and with 8:1 you wont have as quick boost response but u can run a lot higher boost levels.

 

[TurboTerror]

I am running 10:1 on high boost with no problems. You just have to be more careful and very precise on your tuning.

 

[kpt4321]

The higher compression your motor has, the more power you will make at a certain boost level. That means that, with higher compression, you don't need as much boost to make power.

On the other hand, higher compression makes tuning more difficult.

The fact that you don't know this already makes me feel like it's going to be interesting when you start to tune your Haltec.


Edited because half my post dissappeared...

 

[NASTYDSM]

Thanks for your responses. As previously mentioned, everyone seems to have a different view on which compression ratio will yeild the best results. I DO know that higher compression makes tuning more difficult but can yeild a higher amount of HP.

***My main question, which i didn't state clearly, was if the 9:1 pistons would make that big of a difference. Some people say it won't, some say it will. PLEASE LET ME KNOW WHAT YOU THINK!!!

I am leaning more to the reliability side of the spectrum rather than going all out and having to watch very carefully my tuning and such. For the record, I won't be tuning my car, personally. I have a local performance shop that will be doing all of the tuning on their in-house dyno.

 

[AWDLATIN]

Well, since every one told you about the tuning aspect of having high compression, it will spool a trubo a little quicker too. You are a little more prone to knock with fugged up tuning as well. 8.5:1 compression will give you some room to work with a little bit of a slower turbo response.

 

[CBgst]

Go with 9:1. If your having the car dyno tuned then tuning shouldn't be a problem. I personally think 9:1 a good number. 8:1 is a little to low and seeing how people are starting run 10:1 you should be fine. 2gs run 8.5:1 factory so I to me 9:1 really isn't pushing it. I'm running 9:1 with no problems so far. I also do all my own tuning with a logger and afc. Thus far I'm very pleased with my set up.

 

[pneumo]

Keep in mind that high compression and the smaller tuning window will also require more frequent re-tuning as mods change, weather changes, sensors age, moods change. Even if you're not doing the tuning you still should be qualified enough to see when the engine needs adjustment. Or just play it safe and go with 8.5:1 compression.

 

[NASTYDSM]

Thanks for all your help.

 

[13secGST]

Pros
higher compression means, more low end torque, better throtle response and faster spool up.

Cons
A little harder to tune and more dangerous to run higher amounts of boost.



8.0-1 Pros: Run higher boost with less knock and less knock with pump gas.

Cons: Not as much low end torque or throtle response, slower spool up.

If that clears anything up...your welcome...if you already figured it out...good

Personally I would probably pick 9.0-1 not really that big of a difference...and if your using forged internals...why not?

 

[TurboTerror]

Originally posted by CBgst
Go with 9:1. If your having the car dyno tuned then tuning shouldn't be a problem. I personally think 9:1 a good number. 8:1 is a little to low and seeing how people are starting run 10:1 you should be fine. 2gs run 8.5:1 factory so I to me 9:1 really isn't pushing it. I'm running 9:1 with no problems so far. I also do all my own tuning with a logger and afc. Thus far I'm very pleased with my set up.

1G's run 8.4:1, 2G's run 9.0:1 stock.

 

[Mike 99GSX]

Originally posted by TurboTerror


1G's run 8.4:1, 2G's run 9.0:1 stock.

1G's run 7.8:1, 2g's run 8.5:1 stock. He's asking about a factory turbo car not an N/A. Please don't post bad information. Another factor to consider is what kind of gas you are going to be running. The tuning window is narrower with higher compression, but if it will be a track only car running C16 then you still will have room to play. Where you run into problems is trying to push high boost levels on pump gas with the 9.0:1.