compression ratio - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

nexusatm · 04-14-2016, 01:24 PM

Hello people, tell me please what i need to make compression ratio 10 or 9.5? What parts i must to buy? Are there kits aviable for this action? (sorry for my english)

denso · 04-14-2016, 02:22 PM

If you want to lower your CR you have to get a new set of pistons.

Your power goal should be known if you want to lower your CR.

nexusatm · 04-14-2016, 03:03 PM

Quote:

Originally Posted by denso

If you want to lower your CR you have to get a new set of pistons.

Your power goal should be known if you want to lower your CR.

What about connecting rods?

Andew727 · 04-14-2016, 03:06 PM

there are a few ways... even a thicker head gasket can lower compression... pistons are the way to go.

Matt@Cosworth · 04-14-2016, 05:34 PM

definitely replace the rods too
the stock items are weak and very variable in strength as they are a sintered part

SPCorBUST · 04-18-2016, 09:12 PM

Does anyone know how lower compression pistons affect emissions? I think I'd like to use lower compression pistons but I'm concerned that I'll no longer be able to pass a smog. California CARB is a PITA.

R2RO · 04-18-2016, 11:47 PM

You shouldn't lower your compression ratio without first consulting your tuner on the benefits and cons for both keeping stock compression or lowering it, also for the amount of power you want to push out of the engine.

Personally for my build i'm staying with the stock compression with some (Custom CP Pistons, and Carrillo H Beam rods) because I don't think the trade offs you get with lowering your compression is worth it.
i.e. Lower gas mileage, lower grade fuel(usually), and etc.

But if you want to lower it, all you need is some low compression pistons from either (CP, JE, Arias, Manley, and etc just to name a few) just to name a few.

boredom.is.me · 04-19-2016, 12:07 AM

Or you can just run a stock internals with not a shitty tune and be fine to 450whp with e85 and 18psi. You should be blowing trannies before blowing blocks.

Luftwaffel · 04-19-2016, 12:30 AM

Quote:

Originally Posted by boredom.is.me

You should be blowing trannies before blowing blocks.

CSG Mike · 04-19-2016, 12:34 AM

Quote:

Originally Posted by boredom.is.me

Or you can just run a stock internals with not a shitty tune and be fine to 450whp with e85 and 18psi. You should be blowing trannies before blowing blocks.

450whp won't last forever, no matter how good your tune.

boredom.is.me · 04-19-2016, 01:11 AM

200 won't last forever either.
@Reaper

Northwest86 · 04-19-2016, 05:14 AM

13:1 or gtfo.

Reaper · 04-22-2016, 01:53 PM

We have 2 cars locally racing time attack and still street drive. One is stock rods 13.5-1 at 400+whp and the other is all stock 450whp for 27,000 miles. Lots and lots of broken transmissions right now. Not much racing until sequentials come in.

JDMChris · 04-22-2016, 02:05 PM

Quote:

Originally Posted by SPCorBUST

Does anyone know how lower compression pistons affect emissions? I think I'd like to use lower compression pistons but I'm concerned that I'll no longer be able to pass a smog. California CARB is a PITA.

Dont do it, unless you want to lose power.

04-18-2016, 09:12 PM	#6
SPCorBUST Senior Member Join Date: Dec 2011 Drives: 2013 Subaru BRZ Limited Location: Orange County, CA Posts: 935 Thanks: 525 Thanked 399 Times in 255 Posts Mentioned: 23 Post(s) Tagged: 2 Thread(s)	Does anyone know how lower compression pistons affect emissions? I think I'd like to use lower compression pistons but I'm concerned that I'll no longer be able to pass a smog. California CARB is a PITA. __________________ Setup 1: KW C38, Grams 550, Grams 265, 4bar, FlexFuel, Delicious Setup 3: JR C30, DW 700, Grams 265, 3bar, FlexFuel, Moto-East Setup 4: JR C30 HBP, DW 700, Grams 265, 3bar, FlexFuel, Church Setup 5: JR C30 HBP, DW 700, DW 300, 3bar, FlexFuel, Delicious, Built Motor Setup 6: JR C30 HBP, DW 700, DW 300, 3bar, FlexFuel, Delicious, Closed Deck Built Motor

04-22-2016, 01:53 PM	#13
Reaper in orbe terrum non visi Join Date: Jan 2014 Drives: violent Location: Mountains Posts: 1,747 Thanks: 279 Thanked 762 Times in 446 Posts Mentioned: 62 Post(s) Tagged: 1 Thread(s)	We have 2 cars locally racing time attack and still street drive. One is stock rods 13.5-1 at 400+whp and the other is all stock 450whp for 27,000 miles. Lots and lots of broken transmissions right now. Not much racing until sequentials come in. __________________ I have E85 where there isn't E85, that's my secret. http://www.ft86club.com/forums/showt...t=reaper+build

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04-14-2016, 02:22 PM	#2
denso Member Join Date: Feb 2014 Drives: 86 Location: Germany Posts: 84 Thanks: 56 Thanked 18 Times in 16 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	If you want to lower your CR you have to get a new set of pistons. Your power goal should be known if you want to lower your CR.

04-14-2016, 05:34 PM	#5
Matt@Cosworth Senior Member Join Date: Dec 2015 Drives: blue - Cosworth SC stage 3.0 Location: Northants - UK Posts: 330 Thanks: 3 Thanked 388 Times in 182 Posts Mentioned: 34 Post(s) Tagged: 1 Thread(s)	definitely replace the rods too the stock items are weak and very variable in strength as they are a sintered part

04-19-2016, 05:14 AM	#12
Northwest86 Senior Member Join Date: Oct 2015 Drives: Velocity Orange 86 GT Location: Australia Posts: 196 Thanks: 0 Thanked 71 Times in 55 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	13:1 or gtfo.

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