I just bought the car and the swap has already been done it runs great. but other than the port and polish on the head im not sure whats been done inside. does anyone know what the estimated compression ration would be if its stock internals, and if so what i should do to be able to run boost? would appriciate any help.

 

get a compression test! dont even think about boost until you do that.

 

There are tons of compression ratio calculator, included the one found on zealworks. Those are great ways to find out which combinations yield certain results. Pop in the info you know, and you will be able to find out where you stand. If something else is done, IE: Head is milled, or something of that sort, then it will change slightly. You must know exactly what you have done.

Yea dont go boost on that motor, compression is too high if they ran it in an NA car, and wasnt built for boost. Check in with the previous owner and find out what pistons he had placed in there, that would solve all your problems.

 

The preivious owner is kinda a pain to deal with and hasnt really been able to tell me much at all. would taking a normal compression reading tell me anything or and i going to have to tear it down to find out whats been done inside and get the specs that way.

 

A compression and leakdown test will only tell you how much compression is in the cylinders accross the board...so ie: 260 in all 4 cylinders.

The best thing is to know what kind of pistons you have in there, and if the head is milled.

 

What type of head gasket you have is also very important. The thinner the head gasket, the higher the compression will be. so OEM, 2 ply, 1 ply...all makes a difference, along with what crank is in there...

Basically you need to find out whats inside, so you can better determine the numbers.

 

if you do a compression test then you would have an idea if it would be ideal or not to boost that motor. maybe the motor still has the stock pistons. if so then you should be ok to boost a little bit. getting a compression test will answer alot of your questions and also give you an idea of how your motor is holding up.

 

yes but it will not tell him the static compression of the motor...it will only tell him if the motor is healthy enough to boost. You can have a 12.0:1 motor with 260 accross the board, but its still not gonna be good to turbo it. You need to find out what piston, crank combo you have in there...

 

If i Go by what the previous owner says then it has a steel crank, forged pistions, upped rods, and rings with arp head studs. I know the head has been milled with ctr cams and venom adjustable pulleys. But none of it really helps with knowing compression ratio or what has really been done only thing i know for sure is about the head. I guess I'm just gonna tear it down and find out was trying to avoid it. I dropped it off at a local performance shop to get engine management system and tuned on the dyno. I'll get started as soon as cash builds back up lol.

 

Assuming the motor is healthy, a compression test will give you a relative idea of what your compression ratio is. For example, a 9.2:1 b18a should be around 180 psi if healthy, while a 10:1 gsr engine will be over 200 psi. So, if you were to do a compression test and got 250 psi, chances are you won't be wanting to boost it

 

thanks sean ill give that a shot.

 

it should be anywhere between 190 and up if its a healthy stock ls block and b16 head.

 

first off, why would you buy a car and not know whats in it? thats just stupid and the previous owner doesnt know anything or (sounds like he doesnt wanna tell you whats in it/wrong with it). find all the info before buying something like a motor.

anyways stock b20b is around 8.1 CR, b20z is at 9.1 CR, but since it has a b16 head should be around 9 to 10 CR. you said that it has forged pistons so it can be anything. do a CR test. 180-220 is great for boost. anything higher was made to go n/a.