Lowering Comp for Turbo

8krpm

Member
Joined
Jan 3, 2017
Messages
71
Car(s)
EK Civic
Hi guys,

I was hoping to shed some light on this topic. I'm looking at starting the process of purchasing some turbo bits, and one of the things I was considering was lowering compression with lower comp forged pistons.

I was wondering, aside from power loss what adverse affects does lowering comp have? Will the motor's ability to rev past 8k be limited? Also, does anyone have any tips or advise for choosing the "right" comp?

My decision was to go with a 9.0-9.5:1 ratio wiesco pistons at the moment, though I'd like to know if anyone has any ideas to put forward regarding compression ratios? I understand the general idea of compression but it's been a difficult topic to get my head around.

Currently running stock JDM B18c comp which I understand won't cope with anything more than about 10 psi on 98RON.
 

rvm

admin
Staff member
Joined
Apr 15, 2006
Messages
10,627
Car(s)
EK9/Civic
What ecu are you going to use?
Do you have access to a tuner and a dyno?
 

8krpm

Member
Joined
Jan 3, 2017
Messages
71
Car(s)
EK Civic
Hey RVM.

currently running a Hondata s300 v3. I have emailed a few prospective tuners who I would be interested having the car tuned with ultimately though unfortunately I haven't received a response from any of them.
 

Omen666

Active Member
Joined
Mar 16, 2016
Messages
211
Try evil tuning in Middlesbrough pal he mapped my ej9 and did a bloody good job too, search evil tuning on facebook
 

8krpm

Member
Joined
Jan 3, 2017
Messages
71
Car(s)
EK Civic
Try evil tuning in Middlesbrough pal he mapped my ej9 and did a bloody good job too, search evil tuning on facebook

Hey man, not in the UK unfortunately.

No mention of a power goal?

220KW - so about 300 HP at the wheels which I'd imagine would be obtainable in the 9-9.5 comp ratio. I would be running E85 at some point in the future just not sure when. I'm under the impression you can run a high comp turbo ["safely"] build if you run E85 though I don't personally know anyone who has a street driven turbo running a high comp setup on E85.

So at this stage I'd be saying the power goal is assuming petrol from the pump.
 

that_civic

Well-Known Member
Joined
Feb 8, 2012
Messages
1,226
I asked the same question on k20.org, well if high comp and boost works, some replies said they run low boost with high comp and it's fine. Just need to watch out for detonation, thats what i've been told though.
 

8krpm

Member
Joined
Jan 3, 2017
Messages
71
Car(s)
EK Civic
I asked the same question on k20.org, well if high comp and boost works, some replies said they run low boost with high comp and it's fine. Just need to watch out for detonation, thats what i've been told though.

Hey man - yeah, I've heard high comp low boost (no more than 10 psi) is considered safe assuming it has been tuned well. As I was thinking of going forged pistons though, I'm tossing up whether or not I should just lower the comp while I'm here.
 
Top