jimmer 0 Posted May 9, 2008 What is the max comp ratio for a xu10j4rs as a rally engine? I've seen pistons that will take it to over 12:1 will they run on pump fuel and does raising the compression this high put more strain on other engine parts? Any help much appreciated james Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted May 9, 2008 ive been told safely you can run 11.0, you can howvere run up to 13.0 but i dont know what u need to run at this level Share this post Link to post Share on other sites
petert 588 Posted May 9, 2008 They're made at 12+:1 so you can mill them down as required. For 98 ron pump gas, 11.5:1 is about max., but other components need to be matched, such as cam timing. Share this post Link to post Share on other sites
