i have a 99 2.4 cav and am planning on doing internals and turbocharging it, i do not know much about turbos yet, and i was wondering if i should go high compression or low compression pistons if i want to run around 12-15 psi of boost... this might be a stupid Q, but i read that with the gm supercharger not to go low compression, so thats why i am asking...
Low 9 to 1 compression or lower for pump gas reasons. less detonation .high compression is for na.
quite a few people are boosting eco's well into your goal numbers with the stock 10:1 pistons using premium gas and are just fine.
as for the 2.4, people get away with decent boost with the stock compression ratios (9.5:1 and 9.7:1).
It really depends what you are using the car for. If youare just going to race it, I would say drop the compression lower. If you are going to use it for a daily driver, I would say leave the compression close to stock. Raise the compression if you want to try to really squeeze some power out right before it blows up....the choice is yours.
well i have a spare motor that has a spun rod bearing, and i was going to rebuild it to turbo it, but also use it as a daily driver.... any suggestions now that you have some more info?
I built my 2200 to be a boosted daily driver as well. I kept bumped the compression from 9.1:1 (stock for 2200) to 9:1, but had a thinner head gasket and the block decked, so it ended up being ROUGHLY the same as stock. By keeping the compression ratio close to stock, the car will perform close to stock when out of boost. The kids in the 8:1 or 8.5:1 are loosing a lot of low end torque before they produce boost. Thats fine for racing, but sucks around town. That is my $0.02
alright, say i have secret cams, ported heads, bigger injectors and a bigger throttle body.... how many pounds of boost do you think i could run? (on a brand new rebuilt motor)
its common knowledge to drop compression for streetable turbo cars. detonation resistance is the primary factor.
and forget about guess modding
"bigger injectors" and "bigger throttle body" aren't very precise. also boost pressure doesn't dictate power.
build the car for the power you want, then all the answers will be clear.
PJ said it best. Build it how you want. I loe high compression and boost the power is so nice but 1. if you don't have the octane around you to run it then your screwed and 2. if you tuner doesn't really know what there doing your screwed. My little supercharger project is going to use higher compression and produce signifacant gains. If you go turbo lower compressionis ok. But I would never go lower with a positive displacement pump(ie roots and screw type superchargers) your power will go down, sure you will make power but a guy with a stock block supercharged will make more power.
Now I'm not tlkaing about dropping .5 thats ok and reasonable, droppping it a whole point not a good idea, but one of my buddies did that in his EP hatch and barely clicked off 175 hp, he pulled a stock engine and dyneod at 205, put high compression pistons in there and increased boost 2 psi and got 235hp out of his little egg.
alright, i know you probably dont want to hear this but here goes... say i go 30 over, forged rods and pistons, secret cams, and i already have msd dis-2 ignition.... how would that setup be for a turbo at around 10 lbs of boost? or could i even go more than 10?
this is a part of my research to see what i can do to keep it streetable, but have some nice kahoona's... haha
