Supercharger Discussion For all you misguided souls.
Sponsored by:
Sponsored by:

compression ratio help?!

Old 11-29-2018, 03:59 PM
Thread Starter
Join Date: Apr 2018
Posts: 10
Total Cats: -18
Exclamation compression ratio help?!

hi guys,
Ive got a JR M45 SC to go on my mk1 1600, I'm planning on rebuilding my spare engine while I run my high mileage one until it breaks. the question I have is whats a good compression ratio for a supercharger setup? The engine will have a light head skim, ported and polished, heavier valve springs, my Mazdaspeed high lift cams (cant remember the profile), arp head studs, arp main studs, Manley rods etc...

I know the rule of thumb is lower compression for boosted setups, but that's only really for high boost which my M45 isnt going to make. im looking for as close to 200whp as i can get. the setup will be Inter-cooled, dual throttle bodies, bmw TPS etc... im just looking at piston options and i can only find low compression (8.5:1) and high compression (10.6:1) if im right the import mk1's had a factory ratio of 9.4:1. I know i dont need a fully forged engine for a SC setup as they dont make massive power but ideally i'd like the setup to be able to take a turbo too, because if and when i get bored of the SC I might want to go down the turbo route (only a TD04 maybe 250WHP), unless i fall into the V6 engine swap trap . not sure if its possible to get forged pistons closer to 9.4:1 as that would probably be best to support SC and Turbo setups.

Anyway any help is massively appreciated
Kyle_7669 is offline  
Old 11-29-2018, 04:03 PM
iTrader: (24)
shuiend's Avatar
Join Date: May 2006
Location: Charleston SC
Posts: 14,447
Total Cats: 1,341

Put it on your stock motor. Sell spare 1.6 motor for scrap. Use that money to buy a 1.8. Start there if you are going to sink a single penny into a built motor.
shuiend is offline  
Old 11-29-2018, 04:30 PM
Elite Member
iTrader: (6)
Join Date: Feb 2013
Location: Staunton, Va
Posts: 3,208
Total Cats: 397

truth has spoken
ryansmoneypit is offline  
Old 11-29-2018, 05:01 PM
Senior Member
iTrader: (6)
Join Date: Feb 2011
Posts: 540
Total Cats: 64

what is your projected boost psi and what fuel will you be using?
Twibs415 is offline  
Old 11-29-2018, 05:42 PM
Supporting Vendor
iTrader: (31)
Savington's Avatar
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,309
Total Cats: 2,019

The M45 blower is literally incapable of producing enough airflow to put a stock engine in any danger. Do not waste your money on a built 1.6L.

High-Performance Turbo Specialists - Sunnyvale, CA - Email us!

Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
Savington is offline  
Related Topics
Thread Starter
Last Post
Engine Performance
04-10-2009 06:20 PM
DIY Turbo Discussion
02-22-2009 05:40 PM
General Miata Chat
01-22-2008 10:02 AM
General Miata Chat
11-19-2007 09:49 AM
General Miata Chat
04-17-2007 04:23 PM

Thread Tools
Search this Thread
Quick Reply: compression ratio help?!

Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.