Supercharger vs. turbocharger: parasitic loss

Discussion in 'Technical' started by Big Rob, Jul 25, 2007.

  1. No not really if you have 18psi you should be making at least 126hp with that boost alone plus that 36hp it would now be 156hp.

    Torque is the amount of work your engine can do and horsepower is how fast your engine can do its work. So if you had a Mack truck with 400hp and 1500 foot pounds of torque, the amount of work the Mack truck could do is huge because it generates lots of torque. In relation with its horsepower the Mack trucks engine dose its work very slowy.So it would be a really slow acclerating and it wouldnt make for a great race car because its a tower.So if you had a Indy car with 900hp and 500 foot pounds of torque, the Indy cars engine can do very little work compared to the Mack truck but it can do its work very quickly in a short amount of time. This is why Indy cars have to be pushed to a start on the low end but once the Indy car gets going it can acclerate very quickly up to 200+mph
     
  2. Wow.... I don't know where to begin.... really.
     
  3. No! Torque is a force, not work! I am applying a force to my desk chair right now, but I'm doing any work because I'm not moving it, am I?

    Power is the rate at which you do work. The amount of work being done is the instantaneous power output. If your Mack truck is making 200 horsepower and 1500 lb-ft, it's doing work at a rate of 200 horsepower. If it's making 400 horsepower and 200 lb-ft, it's doing work twice as fast. And if it were geared correctly and given a lighter chassis, it would accelerate just as quickly as any other 400 horsepower car -- in all likelihood, faster, because of its tall torque curve.

    Indy cars with 900 horsepower do work at a rate of 900 horsepower. They do much more work than a mack truck. The reason they can't accelerate at very low speeds is because they have extremely aggressive camshafts that make close to zero power at low RPM. Our FSAE car is the same way, up until 10 mph it's almost like the engine's not working, and then it explodes and goes like crazy all at once. Don't confuse torque under the curve (what really matters) with peak horsepower and torque values (which are far less useful than they are made out to be).
     
  4. What he was saying was by your 7 horsepower rule, his car would have negative power without the turbo. Meaning the rule is incorrect. 6 or 7 -percent- per PSI might be a more reasonable rule (edit: though still incorrect), perhaps you remember it wrong. ¯\(o_O)/¯

    Torque is much more analogous to force. There can be force, and torque, without motion, but there cannot be work without motion; if you lean on a wrench on a stuck bolt for example, that's torque and force, but it's neither work nor power. Force is the quantification of the induction of acceleration, while power, you're right, is the rate work can be done. Trucks will be torque-heavy because it takes shit#$%#ingtons of force to get their loads moving at all, but they don't need to do it very quickly.
     
  5. Well then it's another reason that the 300 peak HP cars are slower in the VW world. It makes sense what you said about tq, as mine does fall off up top and the SC VRs stays flat.

    And I know a lot of factors effect the final horsepower. I've had first hand experience that the same PSI doesn't make the same power. Not even close to the same power.

    Fourth. I know. I've had V8 drivers tell me 20psi is a lot, even though the compressor cover is the size of your fist. Many think 20psi = a lot of power.
     
  6. Guess what, I don't make 126, much less 156hp. My little engine makes 90 big ol hp, which means, basically, that you're full of shit.
     
  7. I make 280whp at 18psi. Put some 110 in there, and it's easily above 300.
     
  8. You would have to apply a force greater then that of your desk to move it bro but thats some other thread.

    Yeah you are right about the Truck doing its work at 200hp compared to its 1500lb ft of torque. So if that same Truck had 400hp with 200lb ft of torque, yes it would be a really fast ass Truck once it got moving!

    That 900Hp Indy car engine does less work do to the fact it has less torque 500 lb ft but does its work very quickly do to the fact it has 900Hp that is why it makes a good race car. The Mack Truck does an awesome amount of work with its 1500lb ft of torque but does its work slowly do to the fact it has 400hp.That Mack Truck can tow a 10 ton cargo around all day with no problem. You wouldn't want to put that Indy car motor in an Mack Truck because it wouldn't even move with or with out a load because it has a lower amount of torque. The only reason why the Indy car can do 200+mph is because of its 900hp and 500ft of torque this why it barley moves form a dead stop. Thats why Indy car drivers rev their motors really high and get a push start to get going on the low end.
     
  9. Okay if you make 90hp to the wheels then I bet your motor makes anywhere from 100-115 to the motor. Either that or your car has 300,000 miles on it and needs a new motor.

    To Bentheshift the guy who said PSI isn't power, when it comes to a turbo or supercharger or any engine you are an idiot.An engine is really just a big air pump. Example if you have 5.7 liter 350 engine for every two revolutions it displaces 350ci of air. Psi is air density when it comes to a turbo or supercharger and every racer that knows anything about engines will tell you, the more colder denser air you could fit into a cylinder head of an engine the more power you're gonna make. When you see those funny cars with those huge air scoops for superchargers and turbos all that does is suck in a large amount of air and then compresses it (this is where you get PSI from) into an air intake manifold and cylinder head which is then mixed with fuel and burned equaling more power. Just like on a cold day for every 10 degree drop in air temp an engine will gain 1 hp because the air has become colder and denser.
     
  10. Hollywood, have you ever heard that saying about removing all doubt? Perhaps you should quit >.>.
     
  11. Dude, Youre just blatantly wrong. Completely and utterly. PSi has no direct correlation with power. It has some relation to power relative to ambient pressure and such, but PSI isnt always PSI. you have to factor in parasitic losses, efficiencies, and a whole number of other factors.

    Youre just too simple minded for such a complex system. 10 degrees doesnt mean 1 hp. There are a million factors in play such as heat soak, intercooler efficiency, engine cooling, etc etc. In my GTi going from 80-100 degrees there was a MASSIVE drop in power due to some various factors.

    Youre such an idiot.

    Go do a burnout in your buddies STi. Oh wait, you cant because you cant do a burnout in an STI. too much grip/too little motor/too little clutch.
     
  12. Torque is not work. The units are the same, but their meaning is very different.
     
  13. WOW. A cooler engine makes more power then hot one right? Of course if its a 100 degrees outside your car isn't gonna perform as well as if it was 80 degrees. Yes there are other factors which limit how much power an engine will make. In your case the big one was heat and yeah there is parasitic loss in every engine.
     
  14. Sigh, you just dont get it.

    I lost far more than 2 hp, showing your rule to be wrong. I know cooler engines make more power. I was just showing your rule to be wrong. The only rule that I know that goes along with that is that you gain/lose roughly 1 PSI of tire pressure every 10 degrees.

    and I was talking about parasitic losses between different systems. A 400 pound turbocharger bolted to an engine at 18 PSI will not make the same power as a properly sized turbo at 18 PSI. Its called efficiency ranges and parasitic losses.
     
  15. So what if you have two different engines of the same displacement, say 2.0l. They both have four-valve heads, and one of them has 1cm diameter valves, and the other one has 3cm diameter valves, which means it has nine times the valve area.

    Now give them both the same turbo and crank the boost up to 18 psi. Both of them should make the exact same power, right?

    I could crank up the boost in my old MR2 from 12 to 17 psi and I would consider it lucky if I made 20 more horsepower. A different turbo could (and has made, in the same engine) make 300 or more horsepower at 10 psi. Give me a break.

    And I bet you'd be surprised how an indy car engine would do in a dump truck. With all its 250 lb-ft or so (500 is much more than current F1 cars make.) But, you obviously don't know anything about torque, gear ratios, and acceleration, and just as obviously, you don't care enough to learn, so I'm not going to waste my time.
     
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  17. Dude you couldn’t even answer your own question. The motor with the 1cm valves would extract more power per cylinder then the one with 3cm valves. The 1cm valve motor will be able to make the most out of the turbo charger do to the fact that when the air is compressed into those 1cm valves its going to build pressure and velocity behind the air thats entering the engine. In the case of the 3cm valves bigger isn’t always better the only point at which that 3cm would be better is at higher speeds where it needs larger amounts of air to make the most out of those 3cm valves to build power. Now you are talking about valvetrains which you more then likely have not clue about.
     
  18. Okay, let's slow this down a little. I'm posting this at my 10:00 break so it will be short. I'll try to make a more in-depth post on my lunch break.

    First of all, it is NOT volumetric flow rate (i.e. cfm) that matters in determining the power an engine produces, it is mass flow rate (i.e. lbm/min or lbm/sec). As we all should have learned in high-school physics or chemistry, in order to define the amount of mass of a gas (air), you not only need pressure and volume, but temperature. Remember the ideal gas law: pV=mRT (R is constant)?

    So, as you can see, pressure (psi) is not pressure. Temperature is a big factor in determining the mass of the air volume trapped in the intake manifold. It's an oversimplification to some extent, but are you starting to see why a big turbo that is more efficient at moving more air (volumetrically speaking) at a higher pressure will make more power than a small turbo pressurizing the manifold to the same pressure?

    Also, torque is NOT work, nor is it really a force, it is a moment. A moment is the cross product of a force acting at a distance away from a center of rotation thus trying to rotate an object about that center of rotation. Even though the units of torque and work appear to be the same, they aren't describing the same physical thing. Work is the dot product of a force acting along a distance in the same direction. I'll try to tackle this more on my lunch break.

    Break over... I'll try to get back to this later.
     
  19. Dude WTF!!! that Mack truck weighs 14,766 lbs. according to "http://www.macktrucks.com/assets/mack/Datasheets/Chassis%20Sheets/2008C/CXU6030020740_08C.pdf" check it out for yourselves. that indy-car motor wouldn't even be able to get that god forsaken truck to nudge, let alone start to roll. before you go makin assumptions do your freakin research.
     
  20. #46 Archangel06, Jul 31, 2007
    Last edited by a moderator: Apr 25, 2016
    God dude. You really have to put your face up your ass to get people to notice you huh? check out my link ' http://www.macktrucks.com/assets/mack/Datasheets/Chassis%20Sheets/2008C/CXU6030020740_08C.pdf ' check out how much torque this Mack truck is putting out. 500 ft. lbs. of torque isnt even close to enough torque to move that beast. 1. get your head out of your ass, people already notice you. 2. do some research before you go makinig assumptions. 3. Don't act like you know what in the hell your talking about, it pisses people off. I hope you have learned something valuable today. take it at face value and move on bro.
     
  21. #47 Hollywood, Jul 31, 2007
    Last edited by a moderator: Apr 25, 2016
    What would that Indy car motor do in an 15,000lb Mack Truck? Not a damn thing you galacticaly stupid moran. Webster should put your name next to stupid.

    http://en.wikipedia.org/wiki/Champ_Car
     
  22. Woah!!!! that F-1 racing engine isn't even puttin out the whole 500 ft. lbs. torque. its only 350-425 ft. lbs. wtf.
     
  23. Woah!!!! that F-1 racing engine isn't even puttin out the whole 500 ft. lbs. torque. its only 350-425 ft. lbs. wtf. HOLY SHIT !!!! back to the MACK, It is putting out 1,660 ft. lbs. torque at 1,200 R.P.M. That thing has more torque at idle than that indy engine has peak horsepower, or better yet torque to keep on comparing torque on torque.
     
  24. I had a lunch meeting, so I didn't get a chance to write everything out so another short one before I have to get back to work... Regarding the Mack truck: given the proper gear ratio, the Indy Car engine or the Formula 1 engine may move the truck just fine, and might even do better than the big honkin' diesel installed standard. We would have to see the shape of the power or torque curves to really be able to determine that. PEAK power and PEAK torque don't tell anywhere near the whole story. Also the engine's torque output by itself doesn't tell you anything about the torque at the drive wheels. Finally, the reason these big monster diesels make so much torque and not a whole lot of power is they simply don't spin very fast. Engine speed is a huge factor in wear and these things need to last hundreds of thousands of miles, unlike your typical racing engine. So in order to make enough power to do enough work and still last a long damn time, the engines are designed to be large and make a ton of torque instead of spin fast.
     

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