what is PSI?

hey everybody, i hear all this about "my turbo puts out 8psi" or "my turbo puts out 12 but i can turn it up to 16"... i understand that it's the unit of power that your turbo puts out but what does it stand for? what does it do? and how do you adjust it?

PSI = pounds per square inch. it is how you measure air pressure. So the higher the psi the more air is being pressed into the engine. more air means more hp. You can raise the psi with a manual or electronic boost controller. and you can also remove the bcs restrictor
Im not sure but I think for every 1 psi increase you get 5 or 10 hp. Someone please correct me if i'm wrong. besides increasing PSI on the turbo you should inprove the flow of air into and out of the engine.

on the 14 b i know its 5 hp per pound

soooo if you have a 165 hp engine, and you slap an 8psi turbo on it you are only gonna increse a max of 80 hp?

normal pressure on the face of the earth is around 13.8. PSI is the measure of forced air over that measure. when you calculate out parasitic and regular drivetrain loss, everytime that you double the air pressure, or in other words, every 13.8 PSI of boost, you roughly double your HP. for instance, if you take a 100hp engine, and add 14psi, it will roughly give you 200hp. This is also why when you have a very powerful engine, like a dodge viper, even at low boost, youre getting huge gains.

this also works with a supercharger, but with a supercharger there is a great deal more parasitic loss, enough so that on a powerful engine, running a vortech sueprcharger, at lower boost levels, like 2.5 psi, the engine may dyno the same as it did prior to the dyno, which is why you have to beef up the internals to be able to accept more boost...

that's what i was lookin for. thank you... now another question, is boost something that has a limit? or does your engine provide the limit... what i mean by that is can you "turn" up a turbocharger to like 25 psi??? what is the max you can take one up to??? and what is the engine pressure level on something like that? and if you can't turn a turbo that high, is that why you get a twin turbo?? and theatretically speaking if you had enough room under yoru hood, could you put as many as you wanted?

umm...i have seen a video of a guy who took a turbocharger off of a tank, and bolted it to a supra engine, and at 80psi, the car turned into a fireball...the turbocharger itself is limited in how much "boost" it can produce due to the limited speed of the turbine...bigger turbos can create more boost.

the amount of boost is, in theory, endless, but it is more of a realistic thing. the more that the internals of the engine are beefed up the more boost that the engine can handle, but i think that the most boost i have seen a vehicle run was 35 psi, and that was on a roots style sueprcharger on a 68 GTO, and he was building about 2700hp...it was sick..to say the least.

twin turbos can work in two different ways.
1-each turbo unit feeds pressure into the engine independantly
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2-the engine exhaust feeds a smaller turbo, and the pressure created by that smaller turbo is actually what spins the turbine in a second, usually much larger turbocharger. a larger turbo requires more spool time, and in a twin turbo setup like this one, the smaller turbo being used first helps to reduce spool time, and with this one, you have forced air replacing the pressure of the exhaust to spin the turbo that is actually forcing air into the engine.

im sure that someone could put like 20 turbos, but it woudl become pointless, and another problem, turbos tend to capture heat, andthat is why built turbo cars pay close attention to the exhaust gas temperature and such, also hence the need for intercoolers and watercooled turbo units. the Chrysler ME-412 concept, which has been scraped, is actually a quad turbo setup, but they are not in sequence, as with the above mentioned second scenario.

can someone tell me how to remove the bcs restrictor on my 98 gst? i heard it will take the stock 8psi to about 12-13psi? Is this correct? Can I remove it without moding anything else or would that be like a big no-no?

that answer, i do not know...your GSt only boosts to 8psi?!

i've never heard of an exhaust turbo... how much would something like that run??? also you say that a larger turbine will produce more psi, the biggest turbine i've seen in pix is only about 2-3 inches in diamater... where do you get a larger turbine turbo?

umm your gst should be running between 9-12 psi stock if im not mistaken.... it varies... get a boost gauge set up and then you will know for sure what your starting out at

there are two types of forced induction...superchargers and turbochargers...

superchargers look like this and are driven as a part of the vehicles belt drive accessory system:

in red is the belt that drives the supercharger itself, and it is mounted directly on top of the engine..(this is just one type of supercharger)

turbochargers look like this,

the exhaust enters the turbocharger at point A, which is mounted on the exhaust manifold and spins the turbine in the middle of point B. as the air spins the turbine it exits via point C. the air is compressed sucked in through the opening where the B is, and is compressed and sent through tube D...through the intercooler "E", then through the other tube, into the throttle body, which is F, into the engine.

im sure that i missed a bunch of stuff, but this is a very loose definition of how the two types of forced inductin work. hope it helps.

9-12 psi stock? Sounds good to me. I thought I heard they run lower than that, but that's cool. nobody can tell me how to remove the boost restrictor though? Any help would be much appreciated. Thanks

here is how you remove the restrictor http://www.****s.com/forums/showthread.php?t=185405 let me know how much of an increase you get

where would you find a bigger turbin'ed turbo??? and how much would an exhaust turbo cost and how much boost would you get out of it???

quote:

ORIGINAL: RCJr9186

where would you find a bigger turbin'ed turbo??? and how much would an exhaust turbo cost and how much boost would you get out of it???

All turbo's are exaust turbos, except for the vortech like superchargers, which run off belts.

It depends on the turbo. Turbos are like tires, there are many different kinds and sizes. You can go with a big turbo and have a really high psi but alot of boost lag, you could go with a small turbo and get an instant spool but stay at a fairly low psi. It all depends on price be expected to pay 200 all the way up to 1g or so.

thanks for the link 99clipsgst. i really appreciate it!

well i've been looking at a HAHN stage 2 kit. which is around 3000. but i don't know the first thing to look for when picking out a kit, i only went by what people on here have been saying, the local perfomance shopt said to go w/ a STAR kit. but i duno.

you do understand that you have to beef up the engine itself right?

no please, learn me lol

the stock compression ratio is very low on forced induction engines. the compression ratio is increased by the forced induction, so you need a low ratio prior to full boost. for instance, there was a guy with a 68 GTO with a supercharger at the track last year putting out somethnig liek 2200hp...he was running liek 30psi, and 18 to 1 compression...he ran 128 octane in the engine, but with the supercharger removed, the engine only had like 8 to 1 compression.

if you were to bolt a turbo and manifold up to your stock motor, it woudnt last very long because the compression ratio after adding boost would be so high, and the stock internals are not made to deal with anything about the stock compression.

a friend of mine, who is building 420a turbo has abotu 12 thousand into it right now. that includes:
a new block, 20 over, sleeved. forged crower pitson rods, forged JE pistons, forged crankshaft-stock stroke, fully ported and polished head, neon RT transmission, quaife LSD, custom half shafts, MSD fully programmable ignition and a laptop to program it, turbo manifold, custom front mount intercooler, super 20g turbocharger, thermal 3 inch exhaust....im sure there are things im missing.

ron, you have to understand that making a natrually aspirated into a forced induction motor requires ALOT of work, and money. It cannot be done cheaply, or it will just break.

trust me... i know this!! i know im lookin at a LOT of money and time to build my engine up!!! that's why i was looking for a mod list and time line so that i know what to do first and whatever... and half of the things you mentioned on your friends 420a i don't know what they are... i wish i knw more about cars! do you have an AIM S/n?? so i coul talk to you more about this in more detail

i will PM you my screen name.

just remember that after about 300hp you will have to replace the tranny in the 420a a new motor built for a turbo is anywhere from 1300-2000. depeneding on what u get.

wait wait, you said i would have to replace the trani but you gave me the price for a motor.... a little confused i know that i will have to replace the trani, but why did you give me the price for a motor?? i would have liked to replace the motor but unless i take EVERYTHING out of the front and move everything around, there isn't a motor that will fit in my engine compartment... and i don't feel like selling my car to get a gst or gsx.