hp per psi theory

i heard from people that each psi is like 10hp. if an engine only gets 106hp with 14.5 psi (naturally asp) that proves that wrong right ... if an engine made 145hp it would be so depending on your eng the hp per psi will change. if that is true i if i put 30psi in a 106 hp eng ...not changing the compression ratio it would accually be making more like 318 instead of the esstimated 400hp. let me know what you think!! i am very curious.
:screwy:

its bull, way too many variables. try some research instead or believing conjecture

if your car is putting out 106 hp at atmospheric then doubling the pressure will be like having 2 engines working as one, if your fuel management is good. at 30psi you will be making 212 hp.

im about 80% sure. just dont remember where i read this. correct me if im wrong

Okay...geez...you don't have a clue what you are saying, not trying to be mean....the basic rule you are taking about is 10hp per PSI OF BOOST. Now, that's COMPLETELY DIFFERENT than atmospheric air pressure. The air @ sea level has a air pressure of 14.5 psi. That is different than the HP per PSI thoery. The HP per PSI refers to the power you'll gain ADDING PSI with a TURBOCHARGER...they say on average you can safly assume 10hp per PSI of boost you ADD to the motor.

This has NOTHING TO DO with the natural air pressure of the air. That is just the pressure of the air outside your motor is sucking in w/o a turbo, the pressure of the air on your skin, etc.

Now, on a BOOSTED MOTOR, 30PSI refers to the amount of BOOST you are running. That means it's 30psi ABOVE the natural air pressure...you will have more than 212HP of of 30psi, that's for damn sure. 30PSI is 30PSI of boost...that DOESN'T refer to the total pressure including the regualr air pressure. All of you are mixing up 2 COMPLETLY DIFFERENT THINGS!!! You see, the rule refers to Horse power per PSI of boost you ADD TO YOUR MOTOR!!! This has NOTHING TO DO WITH THE POWER OF YOUR MOTOR FROM THE FACTORY, LIKE YOU ARE THINKING!!! Your motor is 106 hp due to several factors, discplacement, tuning, etc...14.7 psi is just the ambient outside air pressure at sea level. You go up into Utah where the air is thinner, you loose a little power due to less air pressure, so there's less air getting into the motor.

You see, the 10HP per PSI theory on BOOST refers to FOR EVERY PSI YOU INCREASE THE BOOST OF YOUR TURBOCHARGER YOU GAIN 10HP. This is a general rule of thumb, and is ment in general. If you are in Utah where the air is thinner, you'll still get an average gain of 10hp per psi, because this is completly different than abiment air pressure...DO NOT CONFUSE THESE 2 THINGS!!!! That is what you are doing.

So lets recap. 10hp per psi is for a tubo'd motor. It means you will GAIN on average 10hp for every psi of boost you run on your TURBO'D MOTOR.

And 14 psi or so give or take would come close to doubling the power...that would come close to 212hp on a a motor that is 106hp naturally. 30psi would be closer to tripling the power. Of course, 10hp per psi of boost you run is a ESTIMATING RULE. There are other variable that can effect power of a turbo'd motor....tuning, airflow of the turbocharger, where you have an intercooler or not...how efficent it is. This isn't just some simple thing you can learn and master in one day.

think you miss understood what i was saying. if what you say is right... just because the air pressure is 14.5 all the time i will run 145hp ..not true obviously. i am less effecient with my eng becuase i have 106hp with the atm press. now if i got turbo would i be stayiing the same less efficent ratio or 10hp per psi... sorry..i think suck ass at explaining things. just curious what yall think... i made this up i heard from no one so i dont know why someone siad dont believe some one. but whatever .. thx for yalls responses
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think you miss understood what i was saying. if what you say is right... just because the air pressure is 14.5 all the time i will run 145hp ..not true obviously. i am less effecient with my eng becuase i have 106hp with the atm press. now if i got turbo would i be stayiing the same less efficent ratio or 10hp per psi
.

let me have a try at this.

You cannot apply that estimation of 10HP per PSI of boost to your STOCK motor that produces 106HP because you don't have a turbo/supercharger, thus you have 0 PSI of boost, and 0 gain in hp. Your total hp remains at 106 HP.

When they say "you gain an average of 10 HP per PSI of boost" they are talking about the gage pressure your turbo/supercharger pumps. It has nothing to do with atmospheric pressure.

Let's say you slap on a turbo/supercharger. You set it to boost at 6 PSI.

NOW you can apply your "hp per psi theory".

Thus, according to your "you gain an average of 10 HP per PSI of boost", you'd average 60 HP gain, thus bringing your total HP to 166HP. This 6 PSI we are talking about is the gage pressure.

If you want to take it in terms of atmospheric pressure, 6 PSI would be added to the pressure the turbo pressure, so 14.5 + 6 = 20.5 PSI absolute pressure going into the intake manifold. BUT, you have 14.5 PSI pushing the exhaust gases back into the muffler, so this cancels out to having both 14.5 PSI of atmospheric pressure at both ends. Net effect, 6 PSI into the intake manifold, 0 PSI into the muffler.


i heard from people that each psi is like 10hp. if an engine only gets 106hp with 14.5 psi (naturally asp) that proves that wrong right ... if an engine made 145hp it would be so depending on your eng the hp per psi will change. if that is true i if i put 30psi in a 106 hp eng ...not changing the compression ratio it would accually be making more like 318 instead of the esstimated 400hp. let me know what you think!! i am very curious.
:screwy:

Hypothetically, if your turbo was set to boost 30 PSI to your 106 HP engine, your average gain would be 10*30 = 300 HP, bringing your total to 406HP.

thanks, that cleared things up for me

accully op012 ..what you said is what i am believing.

If my eng is makeing 106 hp using the 14.5 atm press. that proves that 10hp will be gained for every psi is wrong.. i am useing 14.5 and not getting 145hp ...i am getting less that 10hp per psi... alot less. so if i put 14.5 more psi in it i wont get another 145hp ill accully get more like 212. that is what i meant sorry for all the miss conceptions. jesus i am horrible at explaining things.... do you all think i am correct in thinking this or am i making no sense ...once again

do you all think i am correct in thinking this or am i making no sense ...once again

making no sense. :screwy:

HAHA oh ok :mad:

accully op012 ..what you said is what i am believing.

If my eng is makeing 106 hp using the 14.5 atm press. that proves that 10hp will be gained for every psi is wrong.. i am useing 14.5 and not getting 145hp ...i am getting less that 10hp per psi... alot less. so if i put 14.5 more psi in it i wont get another 145hp ill accully get more like 212. that is what i meant sorry for all the miss conceptions. jesus i am horrible at explaining things.... do you all think i am correct in thinking this or am i making no sense ...once again

Okay man, let me try and make this as simple as I can, one last time for you. The "10hp per 1 pound of boost" theory applies ONLY TO A MOTOR WITH FORCED INDUCTION, I.E TURBO OR SUPERCHARGED. A naturally asperated motor doesn't make power on boost, therefor it don't apply. Many things besides the air pressure outisde effcent the motors power. The "10hp per 1 lb of boost" theory just says that when a motor is turbo or supercharged, for every 1 pound per sqaure inch or pressure (1psi) you turn up the boost of the turbocharger or supercharger, you will gain 10hp. Now, since a naturally aspirated motor doesn't have a turbo or supercharger, this IN NO WAY APPLIES TO THAT MOTOR. IT ONLY APPLIES TO A TURBO OR SUPERCHARGED MOTOR. Since that 106hp motor is not turbo or supercharged, this theory in no way effects the motor, as the motor is UNDER NO BOOST.

I hope this clears it up for you.

theres way to many numbers here and my head hurts,so hows this youll never know postively until you run dyno and/or engine dyno testing its that simple. its simply a theory

I just wanted to say that the person who started this thread is a moron. Think about this, what if u put a turbo on a big V-8. hard to do, but u could if u had the skills. Youd get more than 10 hp gain from 1 lb of boost due to size of the engine. Also, tuning totally effects your hp gains

Thanks for calling me a moron. i love positive feedback. uhh thanks to eckoman i know understand thanks alot man and yes you answered my question!!! understanding a newbie is a feat in its self. thx alot for yalls POSITIVE responses

the first posts we made fully explained it. I don't know why it took so many other posts to explain it so you could understand. I guess our initial explanations were not simple enough. Anyways, glad this thread is over.

Thanks for calling me a moron. i love positive feedback. uhh thanks to eckoman i know understand thanks alot man and yes you answered my question!!! understanding a newbie is a feat in its self. thx alot for yalls POSITIVE responses

You're welcome. I'm glad I could help explain it for you and glad you have a better understanding now.