blower pressures....
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blower pressures....
What is so diffrent about how they measure a turbo's boost pressure and a supercharger's boost pressure??
I've heard of boost on a turbo routinely upto 15 to 25PSI, with highs of like 40PSI on the F1 cars. I don't remember ever hearing of a supercharger putting out more than 12PSI boost.
But yet, an output of a turbo of 15PSI is concitered about the same boost as about 5 to 7PSI on a supercharger when figureing in hp and torque gains.
thank you for yoru time
bdraft
I've heard of boost on a turbo routinely upto 15 to 25PSI, with highs of like 40PSI on the F1 cars. I don't remember ever hearing of a supercharger putting out more than 12PSI boost.
But yet, an output of a turbo of 15PSI is concitered about the same boost as about 5 to 7PSI on a supercharger when figureing in hp and torque gains.
thank you for yoru time
bdraft
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Originally Posted by hkiefus
I wasn't aware that the amount of boost psi was any different between SC and TC. WWII aircraft has boot pressures of 100psi. Hard to believe.
Yea hard to believe when you conciter the metelurgy of then and now. I don't think they made their engine blocks out of out of concrete reinfoced steel.
That or they must have either measured it in a diffrent way or in a diffrent place in the system. Which leades me back to my question.
Maybe the SC's is measured above atmosphere and the turbo is total pressure??
If you simplify standard atmosphere pressure to 30psi (29.92 or 29.29 I forget), than a SC putting out 5psi would be throwing a total of 35PSI (but since the rest of the system is under 30PSI, the effective boost is 5psi).
If that was the case though, a turbo that was putting out 15pounds of boost would be throwing -15PSI which wold effectivly mean that that the air travel would be from tailpipe to intake inlet (extake inlet?).
Hey, look on the bright side, your tires are never really flat, they always have about 30psi in them.
later
bdraft
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appologies....
I have to make an appology. First for making the dumb move of mixing up two diffrent ways of measuring atmospheric pressure. It's not 29.92 or 29.29psi for SAP (standard atmospheric pressure). Right number wrong unit or right unit wrong number depending on how you look at it.
SAP is approx. 29.92 inches of mercury, it's about 14.7psi. A SAP of 30PSI would be about 60 inches of mercury.
Secondly, i need to appologise for not being able to figure out how to edit my message after I already posted it (I think I remember reading I could do that) at this time.
later
bdraft
SAP is approx. 29.92 inches of mercury, it's about 14.7psi. A SAP of 30PSI would be about 60 inches of mercury.
Secondly, i need to appologise for not being able to figure out how to edit my message after I already posted it (I think I remember reading I could do that) at this time.
later
bdraft
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From: Calhoun GA
At the same boost pressure on the same motor a turbo will make more power, this is because a supercharger is belt driven...it takes HP from the motor to turn it.
Keep in mind, essentially it's not about the boost pressure, it's about CFM. On a stock motor, a blower or turbo can make 10psi. Then you go with a better set of heads, cam and extrude hone the lower intake and then you only see about 8 psi, but it does feel as though there is more power. It's not that you lost any pressure, but that you improved the quality of the airflow. The air can go in and out with less restriction
Keep in mind, essentially it's not about the boost pressure, it's about CFM. On a stock motor, a blower or turbo can make 10psi. Then you go with a better set of heads, cam and extrude hone the lower intake and then you only see about 8 psi, but it does feel as though there is more power. It's not that you lost any pressure, but that you improved the quality of the airflow. The air can go in and out with less restriction
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Originally Posted by Blurry94
Keep in mind, essentially it's not about the boost pressure, it's about CFM. On a stock motor, a blower or turbo can make 10psi. Then you go with a better set of heads, cam and extrude hone the lower intake and then you only see about 8 psi, but it does feel as though there is more power. It's not that you lost any pressure, but that you improved the quality of the airflow. The air can go in and out with less restriction
I would love to understand this better.
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From: Calhoun GA
Originally Posted by hkiefus
Eventually the SC/TC is pushing against the piston, cylinder walls, and head. Now granted, a freeer flowing exhaust can help to evacuate the cylinder and that can result in increased power.
I would love to understand this better.
I would love to understand this better.
Take a drinking straw and pretend it's your stock intake heads and cam. Blow through the straw with all your might and notice the resistance...you can probably create a little "boost" pressure too.
Now let's take a piece of 1" PVC that is the same length as the straw (a little excessive I know, but you get the picture) and pretend that this is an extrude honed intake, ported/polished heads, and a better cam with higher lift. Blow through it just as hard as you did the straw and notice how much less restrictive it is.
The better heads and intake allow more air to flow with less restriction, and a better cam will allow more air to enter the combustion chamber. Keep in mind the SC'er/TC'er are still spinning at the same RPM. Does this make sense?
Last edited by Blurry94; Apr 29, 2004 at 10:21 PM.
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Post Fiend
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It certainly does. I think I understand the benefits of a free flowing induction system. What I would like to understand more is whether it is more efficientto build freeer flowing induction system port/extrude hone, valves, cam profile, etc, etc, or just sping the SC a bit faster.
In my younger days I spent fortunes on these items while my botton ends were a dime a dozen. Today, I just bolt a huffer on the lid. When my engine went to toast at 30K I asked the boys what we should do when it was out. The price of the four cams was only a thousand less than the SC.
In my younger days I spent fortunes on these items while my botton ends were a dime a dozen. Today, I just bolt a huffer on the lid. When my engine went to toast at 30K I asked the boys what we should do when it was out. The price of the four cams was only a thousand less than the SC.
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From: Calhoun GA
Yes you can spin it faster...but with more boost means higher discharge temps, and that can cause engine failure if the tune isn't dead on. At that point, you'll want to look at an inter/aftercooler, water/alcohol injection etc.., even when using better flowing parts. Cooling will allow the tune to be a little more aggressive.
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orignal question....
Still haven't told me why turbos have a higher boost pressure than supers at the same HP rating....
I know that turbos effectivly make more power because there isn't as much loss in turning it as there is for a super.
Was reading through some turbo places today. One package was listing a 15psi boost and 110hp I think. Same engine (ie. same size/brand, both suposedly stock tune) witha super package was getting about 105 to 110hp out of the 5 or 6psi the supercharger was throwing.
Both hp numbers were suposedly from the wheels so all losses for driveing the equipment was factored in I would think.
Still confused about that....
later
bdraft
I know that turbos effectivly make more power because there isn't as much loss in turning it as there is for a super.
Was reading through some turbo places today. One package was listing a 15psi boost and 110hp I think. Same engine (ie. same size/brand, both suposedly stock tune) witha super package was getting about 105 to 110hp out of the 5 or 6psi the supercharger was throwing.
Both hp numbers were suposedly from the wheels so all losses for driveing the equipment was factored in I would think.
Still confused about that....
later
bdraft