whats the general rule of the lbs of boost to how much horsepower you get. for example. for it being so cold i'm seeing about 13.5-14 lbs of boost with just my intake. is it really creating that much more power? i know there is some rule like for every # of boost you get a general amount of hp right?

oops. i wrote ho! haha i meant hp

 

Somewhere around 8 HP per # of boost.

 

there is no general rule because each f.i. is different. On a supercharger, you have to use power to make power, on a turbo, not so much. also, engine varibles, compression ratio...ect ALso, psi is a measure of pressure in the intake manifold...not a measure of volume. That is why a bugatti veryon makes 1000hp with 16psi...and our cars only make xxx amount of power. So if you increase the veryon by 1psi and our cars by 1 psi, i'm sure the difference between the two will be quite large.

 

So if we boost 12.5lbs. that means that our little 2.0 motor only puts out 105hp? thats kinda funny if you think about it hahaha

 

with your example, that would mean that is what the suprcharger is putting out onto of the engine..another way to think of it, without the supercharger, your car would dyno 105 less hp.

 

I believe that for each psi of boost you would get around 6HP/8TQ on the M62 and our motor. Other factors definately make a difference though. If you allow the car to flow better you can reduce the psi and make more HP essentially allowing the motor to make more HP per psi.

 

Why would you guys think that for every pound of boost you have, you'll gain an x amount of power? Tell me how much power you gain with 15 pounds of boost and a a/f ratio of 14.1.

There is no predetermined amount of power you'll gain for every pound of boost you create. There are much too many variables that play into it.

 

Its not the psi that give you the amount of horsepower its the volume and density of air. You can get a rough idea of what the m62 will do per psi however that is just a guesstimate. It will change with temperature elevation and mod list.

 

Well basically HP = torque * RPM/5252 and boost psi is.... aww hell....

I'm too lazy to figure or find a formula to add boost psi into the hp formula so let's use ricer math.....

Your stock ss/sc runs anywhere from 188-218 whp and I'm assuming boost is between 11-12.5 psi.

Stage 2 dynos have been recorded from 222-248 whp again assuming 14-15.5 psi.

so 30hp boost from 3psi is 10hp per psi.

(These numbers have been made up and in no way have any factual data to back them up)

 

There is no pre determined number. The 8 HP I posted is a general gain that guys have found going from one size pulley to a smaller one.

 

General still meaning guestimate and even still, dynos aren't 100% accurate and vary if that's what you're going by. It might give you an idea but the point is that you can't say that you will gain even in a certain margin with a certain pulley size (PSI) because there are too many variables in between that could alter it.

 

yes adam it is a guestimation, and mr.t called, he wants his life back. haha

7-10hp per pound of boost is fairly realistic

 

What about the guys who are in higher elevations or the guys who are running overly rich? Or the guys who are running 2.6" pulleys without aftercooler upgrades and IATs are exceeding 200 degrees?

 

Ok, here's the deal. Assuming atmospheric pressure is 14.7psi (at sea level), 2 bar or 14.7lbs. of boost would double the density of your air (assuming it did not raise intake temperature, which is impossible due to boyle's law, and assuming your CFM remained constant, which it won't). So assuming that you measured the intake temperature after it exited a perfect intercooler that reduced the IAT to atmospheric temps., without reducing velocity (constant volume) and you increased the fuel the appropriate amount, and you had an intake, valve and exhaust system adequate for the task, the most you could possibly realize per lb of boost increase is: 1/14.7 or a 6.8% maximum theoretical increase per lb of boost. This does not include the hp required to compress the air, which must be deducted from the max theoretical increase.

Practically, below 2 bar you would be doing good to realize a 5% increase/lb of boost on a turbocharger or an independently powered F/I system (like an electric supercharger) that has no parasitic load on the engine. Unfortunately, as you spin a belt driven supercharger faster, the parasitic load increases geometrically.

After 2 bar there are far too many variables to predict hp gains with any degree of accuracy. As a general rule of thumb, as you approach higher boost pressures, the percentage of gain tapers off exponentially due to increased temperatures, increased coefficients of friction, design inefficiencies and physical engine limitations.

 

Say were you a writer for Star Trek??

 

well im stock with just an airbox mod and withteh cold temps over here im runnin about 14lbs... n i dynoed last weekend at tunetime 238whp/199ft-lbs on a mustang dyno.. with some weather correction it came out to 228/190... n i kno for sure that with warmer temps it wont b like that..

 

damn. i didnt need all that. i know there is the guesstimate out there. not an exact answer. and yes i meant on our motors, which is why i stated the 1 mod i had. i would obviously dyno higher being colder vs. in the summer. was just wondering about what that would equate to in terms of power. and yes i'm about at sea level and the temp is like 15

 

then u can pretty much use my numbers.. im close to sea level and its that cold here... sooo just look at my numbers i dynoed last week