Join Date: Aug 2009
Location: Battle Creek, MI
Lowering the CR on the engine does NOT allow you to run more boost for more power. Lowering the CR on the engine DOES however allow you to run more boost WITHOUT knock on pump gas. More boost does not always mean more power. There are a LOT of factors involved in building engines that determine the power outputs you are going to have.
For example. My turbo on my evo doesn't "wake-up" until 30psi+. If I were to run anything bigger than 9.5:1 CR pistons I would have to add some sort of alcohol/higher ethanol based fuel (e85 or race gas or meth injection), just for the simple fact of with that much boost, you are adding higher temps with the extra compresson and you will get detonation without adding a type of "cooler" additive into the fuel to help keep it from detonating pre-maturely. You CAN run the stock 10.4:1 CR pistons in your turbo'd 2.4, HOWEVER, this does NOT mean you can't push more boost or the same boost out of it as a 2.2. However, this does mean that you are going to need to add something to your setup to run more boost, and the TUNE has a lot to do with it too. If you can tune for the extra fuel needed for the more boost, as well as the cooler additives, but if you can't tune the car yourself or have someone help you tune it and you start getting knock, REGARDLESS of the CR you have, you will blow it up.
Adding CR to an engine does actually give you more power. So if you can find that medium of CR and boost, you will maximize the amount of power you are going to be able to push out of the engine. So yes, you can raise the CR, and the boost, you just have to make sure you're not doing anything to over push it without the proper safety steps taken to make the engine more "bullet proof" as some of us refer to it as.
In cobalts you have a 3 degree tolerance of KR that you can "safely" get out of these engines. Anything more than that, and you're actually damaging the engine. Obviously with more boost, you have to have a more spot on tune to keep you from getting the KR, so you won't blow up your engine. Just do a little more research before fully deciding on what you want to do. Just don't be discouraged by some, but also, try to keep in mind a lot of us on here have a LOT of experience doing these things with not just these cars, but others as well, and we have a lot of information to give to someone that wants to know. Don't take the information given as a threat or harassment or anything negative, just use it as helpful knowledge that you can use to help further your knowledge on the stuff you're trying to do.
WITH THAT SAID, keep this stuff civil. I read what seemed to me to be a little hostility. I don't want to have to start deleting posts in a sticky.
Mods - Injen CAI, CIA MAF Relocate CP's, Dejon FMIC,
Custom 3" DP, 3" Exhaust, GT3076R, Pioneer AVH-4100DVD, Hurst STS, ZZP triple pod, Autometer Cobalt boost/DPIC/WB gauges, Nitto NT05 245/40/18's, H&R Springs, 80:20 Meth Spray
Future - KSport Kontrol Pro Coilovers, 10% Tint, FMIC spray
538whp/501wtq @38 psi on meth and 93 oct on stock ish motor
06 EVO IX MR/SE - Sold
Mods - *Updated 10/6/13* AEM TRUboost EBC, 4in custom TBE, SD dual 93/e85 tune, ETS 4in Race Core FMIC, Dual Aeromotive 400lph Fuel Pumps, T4 Tubular Manifold w/ dual WG's, FP Super99HTZ DBB Turbo, GSC 274 mivec cams, ARP headstuds/rod studs, FIC 2150cc Injectors, Aeromotive FPR, Aeromotive Fuel Rail, catch can, Mini Battery Kit, Slim Coolant Fan, Kiggly Racing high pressure valve Springs/Titanium Retainers, Supertech Stainless Steel Valves, Dual VTA Tial 44mm WG's, 4g64 Stroker Manley Pistons, 155mm 2.4 LR Manley Turbo Plus I Beam Rods with ARP 625 Studs, 100mm forged non-billet Manley Crankshaft, Full H/E PNP with Port Matching, Kiggly Racing Girdle, Dual Tial 50mm BOV's, Excedy Triple Disc Carbon HD Clutch, AEM EMS
'95 Ram 2500 Diesel
Mods - 5in TBE, Boost Elbow set to 28psi, Adjusted fuel pump, Open Turbo.
Future Mods- Super Street Clutch (rated @1400ftlbs tq), 67mm turbo, 160lb valve springs, added timing, tubular exhaust manifold, larger injectors, possible 6 spd swap.
Master ASE Certified Gasoline/Diesel Technician since 2004
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