turbo question???

[Die Ford V8]

I know a SC takes hp to create more hp, but how much hp does a turbo rob from the engine(if any) to create the boost needed for the extra hp?

alot of authorities claim that a turbo is free hp, is this true?

yeah, still learning about turbos

[DarkEcho]

turbos run off of the exhaust, its hooked up so that the exhaust gasses spin propeller like blades in one part of the turbo, then the gas exits, the propeller blades are connected to a rod that spins another set of blades that go back into the intake, so the faster you go, the more exhaust you push out, the faster the primary blades spin, the faster the secondaries get spun, and thus you get accelerated air into your engine.

turbos cause backpressure in your exhaust system, so if you get a turbo (or two [img]smile.gif[/img] ) i would suggest improving your exhaust first, and get a nice large size 2.5 or 3" to allow the gasses a larger space to excape. then get your turbo and do all the mods to get it working. turbos wont take as much power as supers will from your engine BUT an SC will provide you with an INstant boost because as soon as you hit the gas, the SC kicks in and begins spinning, since its hookd up to pulleys. the turbo takes a while to "spool" and gain speed. so i would say get a supercharger if you want that instant kick as well as if your car is automatic, the torque converter causes a very slight delay from when your foot hits the gas till when the back wheels actually start turning due to its fluid setup.

sorry if this is too much info but my buddy has a 3000 gt and is doing a turbo conversion to a car that is already basically meant for turbos and he has had to buy ALOT of parts and its taking him almost a year to collect everything, i dont think SC's need as much modification but im not sure. hope this helps!

[T-Punk]

if you are want to have a decent daily driver i would suggest the turbo simply for gas mileage. other than that the differece, as said above, is pretty much turbo adds backpreasure and has to spool up where as the supercharger is always runnig and gets you that instant accel. but it takes a pretty decent amount of power away (usually about half of what it adds). so if you have a supercharger that put out 200hp it will usually only add 100 because half of the power it adds is used to run it. this can change depending on brands but thats fairly close from what i have seen. But to answer your question about turbos taking power to make power; no they dont take power to run but they do increase backpreasure which lowers you engines efficiancy. i deffinately agree that you should upgrade your exhaust but i would say do that for both. since both force more air in you will need to then get the exhaust out more quickly as well. now that i have like a page on this im going to stop. (please noone turn this into a "turbos are beter than S/C's" because they each have there strong and week points)

[Die Ford V8]

thanks man, I have read about every post and had a few friends show me some things so i know how a supercharger and a turbo works,

but, and I know turbos creat some backpressure, how much power does it rob from the engine. for example, if you still had lets say 12 psi going into the engine, from an outside source(engine w/o turbo)(no backpressure) how much more would the engine have.

with a SC I read that it robs 100hp but gives you 200 so you have a 100 gain.

with a turbo it robs _____ but gives you _____ so you have a _____hp gain. hope you had math class, he he

[T-Punk]

thsi is really hard to say. depends on exhaust and such but i would say if you run a 3" with no cat (cut out after the turbo) it would be somewhere around 10hp to maybe 30 without the cutout on a bad exhaust system (aka: stock exhaust). its just a rough guess... a very rough guess. i would shoot an email over to tiago. He is the resident turbo god. Shane might know too but 20 would be my best guess with a full 3" exhaust. basically you make 180 with the 3.8 (its the one i know best so im going to use it as an example) and you end up with 300rwhp after the turbo so 300-180=120 after you have lost your 20 or so hp from b/p. so i would say a proper sized turbo puts out around 150hp before acounting for b/p.

[phoenix64]

If your running 12psi with a turbo, your exhaust back pressure will be equal to about 24psi. You lose about 30hp from back pressure at that psi.

[Arctc Wolf]

turbo's r unique. depending on how big the exhaust housing is, u will get more or less backpressure. smaller turbo's will spool up quick, but add a lot of backpressure. larger turbo's will reduce backpressure, but add a lot of lag. also, smaller turbo's make better low end power, and bigger turbo's make better top-end power.

[Die Ford V8]

tiagos turbo is the better of the big and small right.
goldylox has the pourage just right?

[Arctc Wolf]

for our motors, it's a balanced turbo. good spool, yet not a lot of backpressure. There's a ton of other little things that u have to look at in turbo design that will affect spool and backpressure besides housing size. turbine design, turbine material, turbine diameter, center cartrige type(standard, ball bearing, dual ball bearing), compressor wheel design, diameter, material, and housing size.

[Tiago]

http://web.camaross.com/forums/showt...s+supercharger

[T-Punk]

well that was the best explaination ive ever found.

[Turbo V6 Camaro]

Assuming: the engine is flowing 1000 cfm of 60 degree inlet air (converts to 76.37 lb/min) and the centrifugal compressor of 70% efficiency (regardless of drive mechanism - exhaust turbine or crank driven) is producing 10 psig boost.


How much hp does it take to drive this compressor?

power = mass flow rate * (change in enthalpy)
Solve for compressed air temp = 143 deg. F
Look up enthalpies at 60 F and 143 F.
Solve for power = 88,442 Btu/hr
Convert to hp = 35 hp
35 hp / .7(compressor efficiency) = 50 hp

So, no matter how you drive this compressor, it takes 50 hp to spin it, 35 of which goes into compressing the air and 15 is lost as heat added to the air.

Supercharger: Drives off the crankshaft, so we stop here.


Turbocharger: Drives with exhaust gas, so we have to perform the same calculation on the exhaust side:

Assume: 1200 deg F exhaust gas to drive the turbine side of the turbocharger.

The exhaust side is a little trickier, though, since the mass flow rate is greater. We added 1 part fuel to 12.5 parts air after the compressor. So, add ~8% mass flow rate and you get 82.6 lb/min flowing through the exhaust turbine.

power = mass flow rate * (change in enthalpy)
88,442 Btu/hr (50 hp from earlier) = 82.6 lb/min * (change in enthalpy)
Change in enthalpy = 18 Btu/lbm
18 Btu/lbm / .7(turbine efficiency) = 25.5 Btu/lbm
Look up enthalpy at 1200 deg F, subtract 25.5, and you find a temperature of 1100 deg F.
Therfore, the exhaust gas loses 100 deg F as it passes through the turbine wheel. This lost heat is what drives the compressor wheel.
Assuming the exhaust system adds 0 psig backpressure, using T1 and T2 of 1200 deg F and 1100 deg F, it can easily be found that the change in pressure across the exhaust turbine is 3.57 psi


Conclusion:

So there we have it, on this engine and the above assumptions, the supercharger takes 50 hp to drive it and the turbocharger adds 3.57 psi backpressure.

It is physically impossible (even assuming a 100% efficient compressor and turbine) to pressurize the intake air without adding backpressure or taking power from the crank. If you figure out a way to do it, you've broken the laws of physics and are smarter than Albert Einstein.

Is 3.57 psi backpressure negligible? I suppose it depends on your combo, camshaft mainly.

On my last car (naturally aspirated), reducing backpressure from 9 psi to 6 psi netted 40 rwhp. Is this the case on every car? Probably not. Lingenfelter recommends running less than 5 psi backpressure.


i didn't do that its from camaro ss dot com

[oil pan 4]

With a turbo you have to burn more fuel to make each hp than any thing else.
N/A = about .5 lb/hr of fuel per hp
SC = about .55 lb/hr of fulr per hp
Turbo = about .6 lb/hr of fuel per hp
Turbo RX7 = .7 lb/hr of fuel per hp
Brake specific hp consumption
Of power adders SC and turbo the SC should need less HP to drive it.
So there is now why turbo gives free hp.
You here import guys (the ricers mainly) say that turbos are more efficient and that its free hp.
Just because you can see the belt driving the SC you know it needs power to be driven, turbos are a litte different you cant see what's in side there going on if your just standing there looking at it.
They just say it as a general term, they don't say whats moer efficient but that just that they are.
I here it over here all the time ( you state side people have no idea).
If they stick around to here me repeat my self very very slowly after about the 4th time they start to catch on.
The only free hp is nitrous and nitrous is about $10 a pound over here and you need a licence to buy any compressed gas (this place sucks).

[Die Ford V8]

i have a video and will try to put it one but this guy with a mustang gt had bling bling stickers on it and has now idea what an engine is im sure. the guy with the camera asked him about his twin turbo v8 and the guy said"yup twin turbo v8" then the camera buy was like, "rotary engine right" the idiot was like "yup" I know the basics and figured they took at least some backpressure to run, but my friend steve wanted professional proof so here he has it. i will try to get some vids up soon.

[Arctc Wolf]

BSFC depends a lot on the motor. Ported heads, cams, ect. and all those little crazy things i always talk about lower BSFC, allowing more power to be made w/ less fuel

On the example earlier, 3.75 psi backpressure isn't much when compared to 10 psi boost going in. where u start to see no gains is when backpressure and boost numbers come close to matching each other. then power suffers and ur "free power" disappears.