420A Confused, What compression pistons I should use?

[GersonDSM]

I am planning on putting a turbo and 650cc fuel injectors on my 420a with all the other internals modified of course but am stuck on what compression pistons I should use either low or high or what ratio thats the last thing I need to know. Note: street car mainly for car meets and stuff also for a little racing kind of my daily what do you recommend

 

[spyderdrifter]

Use a lower compression piston with forced induction. Turbos and superchargers will inherently raise that compression ratio once they spool. If you use a high compression piston with forced induction, you may run into issues. I raise my 4g63 compression to 9.0:1, but that's as far as I chose to go.

 

[GersonDSM]

Use a lower compression piston with forced induction. Turbos and superchargers will inherently raise that compression ratio once they spool. If you use a high compression piston with forced induction, you may run into issues. I raise my 4g63 compression to 9.0:1, but that's as far as I chose to go.

So for my 420a should I use 8:8:1 pistons from wiseco because those are the ones I have been looking at the moment. Also what about the injectors 650cc does that change anything or could it still be rolled with low comp pistons?

 

[spyderdrifter]

You can use those pistons if you're wanting to and be fine. OEM 4g63 injectors run 450cc if i recall right. Anything higher will only add more fuel, and thus increase power. Yes they could be used with those compression pistons, but that is your choice.

 

[GersonDSM]

You can use those pistons if you're wanting to and be fine. OEM 4g63 injectors run 450cc if i recall right. Anything higher will only add more fuel, and thus increase power. Yes they could be used with those compression pistons, but that is your choice.

Oh ok because Im pretty much going in this build blindly and this is my main confusion just in your opinion you would recommend around 450cc then? For pistons Im not maxing out boost so would you say I could move up to around 9.1 I just pretty much want the perfect combination of pistons that deal with the boost I am putting around 8 for now and a little more fuel. To get some good backfires for meets and stuff

 

[spyderdrifter]

I'm not recommending anything, just telling you options. You could use the 650cc injectors if you want, and be ok. Increasing the injector volume will just raise you fuel flow and power.

 

[GersonDSM]

You can use those pistons if you're wanting to and be fine. OEM 4g63 injectors run 450cc if i recall right. Anything higher will only add more fuel, and thus increase power. Yes they could be used with those compression pistons, but that is your choice.

I'm not recommending anything, just telling you options. You could use the 650cc injectors if you want, and be ok. Increasing the injector volume will just raise you fuel flow and power.

Gotcha ok a tune would help that then but yeah I understand what you mean if I am adding a turbo I should use low compression because of the extra compression the turbo puts out to kind of level it out pretty much.

 

[spyderdrifter]

Yes, exactly. And injector size isn't going to matter as much as long as they can handle the load (power output) you're trying to achieve.

 

[GersonDSM]

Yes, exactly. And injector size isn't going to matter as much as long as they can handle the load (power output) you're trying to achieve.

Thank you this just cleared up my confusion and now I understand what pistons are better with what items

 

[spyderdrifter]

You're welcome, happy to help.