Turbo vs. Super... Why the hate?

[TrotFox]

Seriously, I'm wanting opinions here. I recall seeing someone say how turbo was far superior to supercharging. Why and under what conditions? I have a non-Fiero, ex-racer, current airplane mechanic friend who has the exact opposite opinion. Currently my understanding is that I would enjoy a super better.

My desire is for a primarily cornering car that also happens to be fast in the qtr. This makes me lean toward super for the non-lag throttle response.

What say you guys?

Red 5spd Formula (gonna have more cubes first...)
Trot, the info gathering, fox...

[goatnipples2002]

supers have lag maybe not as much as an oversized turbo but none the less they have an amount of lag. Now that amount might not be much but they have lag.

[Aaron]

supers have lag maybe not as much as an oversized turbo but none the less they have an amount of lag. Now that amount might not be much but they have lag.

Kind of. (Premature apology for ba grammar/spelling/sentence structure, I'm a bit annebriated).

First you need to understand Lag, and timing. Turbo lag is when an engine is at an RPM with sufficient enough exhaust volume (At WOT), to produce boost, lag is the time it takes going from closed throttle no boost, to full/max boost. So basically, in a WRX STi, sitting at 6,000rpm, and flooring it, and time it takes to get full boost. That is lag.

Timing is the area where the engine is not at a sufficient RPM to produce enough exhaust volume to produce boost. So on the STi example, from 0rpm-3500rpm).

The following is for roost/twin screw supercahrgers, not centrifugals. Since a supercharger is always at a sufficient RPM to produce max (Or close thereabouts) boost, timing is out of the question. Now there is lag on a supercharger, as you said. When you're at, say 3,000rpm (Any rpm will work), you go from closed throttle to wide open. The throttle plate(s) snap open, the supercharger pulls max airflow, then pushes it into the manifold faster than the engine can bbreathe it in, thus pressure is built. This happens near instantly. You will not notice the "lag" on a properly sized, decently deisgned, supercharger system. It will be minute compared to that of even a spectacular twin turbo system. For all practical and logical discussion here, roots/twin screw superchargers have no lag, thus one of the advantages over a turbocharger.

Now over my ADD, my opinions on which is better:

Turbocharging is better. Lag and timing can be minimalized by GOOD design, and GREAT components. This means money though. Now generally, if a mod helps increase response and timing, and alleviate lag, it will hurt high end power and flow. This holds true for intake manifold design, turbocharger selection, exhaust manifold design (excluding ITBs), camshaft selection, cylinder head prep, etc. However there are mods that help turbo response/lag, AND high end flow. The only mod I can think of off hand is a free flowing intake and exhaust, and VVT (That's not exactly a "mod"). Ball bearing turbochargers help response and lag time A LOT, without sacrificing high end flow. But they cost more money...lots more...for good reason.

Now twin turbochargers are better yet. They cost more, and will not produce as much max power as a properly sized single, however the response and lag elimination gained is well worth it in my opinion. Take the 3000GT VR4 for example. Maximum boost at 3,000rpm, building from 2,000rpm up, and still pull/flow strong to 6500rpm, with minor dropoff after that to the 7,000rpm redline.

However superchargers have their place. I LOVE blowers. They sound awesome, drivability is great, and power is strong across the board (Though not as strong as a turbo).

It all comes down to what you want. What engine is this going on? The best choice is to complement the current engine's personality.

[slow'n'steady]

IMO:
turbos are more flexible and can control horse power easily with a boost controler/wastegate, on a SC you have to change the pulley an belt
superchargers use 20%-30% of the engines power to run it, so you are robbing horsepower to make horsepower where as a turbo runs on exhaust gas so it doesnt rob any horsepower to begin making more horsepower. Turbos usualy make as much horsepower at 9psi as a supercharger makes at 12psi.
turbos are more reliable due to the simplicity of the design, not much can really go too wrong with them, whereas with a supercharger, you have to worry about belts slipping and/or breaking, crankshaft, bearing and engine damage caused mby belt tension on the crank pulley. turbos are also more streetable as they are not ALWAYS making boost like a supercharger. if you drive normaly with a turbo there is virtualy no difference from it being N/A but with a supercharger that runs off the crank, as soon as it starts spinning you are constantly making boost of some kind.

plus turbo systems are usually cheaper!

[Aaron]

IMO:
turbos are more flexible and can control horse power easily with a boost controler/wastegate, on a SC you have to change the pulley an belt
superchargers use 20%-30% of the engines power to run it, so you are robbing horsepower to make horsepower where as a turbo runs on exhaust gas so it doesnt rob any horsepower to begin making more horsepower. Turbos usualy make as much horsepower at 9psi as a supercharger makes at 12psi.
turbos are more reliable due to the simplicity of the design, not much can really go too wrong with them, whereas with a supercharger, you have to worry about belts slipping and/or breaking, crankshaft, bearing and engine damage caused mby belt tension on the crank pulley. turbos are also more streetable as they are not ALWAYS making boost like a supercharger. if you drive normaly with a turbo there is virtualy no difference from it being N/A but with a supercharger that runs off the crank, as soon as it starts spinning you are constantly making boost of some kind.

You miss some concepts.

You do not HAVE to change pulleys to control boost, that is merely the best method (Air bleeding works, just not well). Turbochargers DO rob power, just generally believed to be not nearly as much (And it is near impossible to calculate how much).

I firmly disagree that turbochargers are more reliable. First of all, they simply do not last as long. Next, they use engine oiling, thus adding lines and complexity to the system. There are A LOT more hoses (aka places for leaks), and they offer more unpredictable power delivery.

Superchargers DO NOT always make boost. In fact, due to recent bypass technology, quite the opposite is true. First, at low throttle levels, there is simply not enough air to overcome the engine's natural breathing, thus no pressure is built (Roots). Next, most every blower nowadays has a vacuum/electrically operated bypass valve, alleviating low throttle boost.

Turbochargers also take advantage of the energy in the form of heat from the exhaust, which is unused/wasted by a supercharger.

[slow'n'steady]

as for reliability, i was talking about the actual unit itself, not the components (lines and such). superchargers must have a step-up mechanism (gears, belts, pulleys or a combination) consisting of numerous moving parts, to convert 6000 engine rpm to the 40,000+ rpm necessary to build boost. Turbochargers need no step-up mechanism and have only one moving part, the compressor/turbine wheel assembly. The simplicity of the turbocharger is therefore less prone to mechanical problems

turbos are exhaust driven and dont require horsepower to spin the compressor. turbos tend to make more power and torque lower in the RPM range than a SC. example: A supercharger that is suppose to make 8 psi at 6000RPM may make as little as 2.5 at 3000 RPM. Also with a SC the compressor speed and boost level increase as the engines RPM increases

[Aaron]

turbos are exhaust driven and dont require horsepower to spin the compressor. turbos tend to make more power and torque lower in the RPM range than a SC. example: A supercharger that is suppose to make 8 psi at 6000RPM may make as little as 2.5 at 3000 RPM. Also with a SC the compressor speed and boost level increase as the engines RPM increases

You're completely wrong.

Turbochargers DO require power to spin. They block exhaust flow, much like a muffler. This explains why a turbocharger often quiets a motor as much as a muffler. As I said before, it is generally coneived to be drastically less than that of a supercharger, and is near impossible to calculate.

Turbochargers DO NOT make more power below their spool-timed RPM. A properly setup roots/twin screwed STi would make more low end power than a stock turbo STi, as the turbo isn't making much, if any at all, boost. A PROPERLY SIZED and implemented supercharger will make near full boost from idle to redline, on most average RPM engines (<8,000). Here is a graph that I've posted bazjillions of times. Otherwise stock Ford Mustang Cobra, 4.6l DOHC, factory supercharged via a Eaton M112. Notice the Eaton and Kenne Bell 2.2l (A twin screw blower), make near max boost from start of the WOT dyno run to redline, and the turbo takes until ~4,000rpm to get full boost (14psi on this test).

[Dustay]

turbos or superchargers, what's really the difference? I mean its your opinion which one you want and which you think is the best. They are well matched. Most love the sound of the turbo so they take that over the supercharger scream. The turbos do have easier accessories to install like: timers, bov, intercoolers, and what not! lol that's MHO so :afrocool:

[p8ntman442]

and is near impossible to calculate.

unless your not a moron, and have some training in thermodynamics.

[Aaron]

and is near impossible to calculate.

unless your not a moron, and have some training in thermodynamics.

What does thermodynamics have to do with how much power is lost due to exhaust restriction?

[Series8217]

[Aaron]

Well it plays a part, as to how much volume there is, but fact remains, how do you measure the power taken by a turbocharger? It's constantly changing, has tons of variables, differs with every single application, etc.

So you know how hot the exhaust is.

So a Honda Prelude with a T3 that has 300* exhaust, its turbo costs it 30hp, while the turbo on a F350 with a Tfuckingbig and 400* exhaust costs it 40hp, right p8ntman?

[p8ntman442]

AArogance is a stinky cologne.

Put down the keyboard and pick up a book. Start with the law of conservation of energy.

[The Dark Side of Will]

turbos are exhaust driven and dont require horsepower to spin the compressor.

This is incorrect.
Do you think the compressor doesn't require any power to run? That's incredibly wrong.

The compressor does require power. At a given efficiency, boost & airflow, a turbocharger compressor will take every bit as much power to run as the compressor of a centrifugal supercharger. Where do you think this power comes from?

It comes from the turbine. Because the tubine isn't 100% efficient and the compressor isn't 100% efficient, the turbine has to pull MORE power from the exhaust than the compressor puts into the intake air. If the compressor is 75% efficient and the turbine is 75% efficient, the turbine needs 77% MORE (1/(.75*.75)) energy in the exhaust than the compressor puts into the intake air. This means that the backpressure created by the turbine is HIGHER than the boost pressure generated by the compressor.

[crzyone]

The compressor does require power. At a given efficiency, boost & airflow, a turbocharger compressor will take every bit as much power to run as a centrifugal supercharger.

Not quite true, a turbo also uses heat energy as well as pressure to power the compressor. A centrifical supercharger only uses mechanical energy from the crank. There is also loss through its gears and also has efficiency loss through the compressor. I would have to say a turbo is slightly more efficient. Plus, a centrifical supercharger makes more boost as engine rpm goes up where as a turbo makes max boost earlier and is then regulated by the wastegate.

Edit- You are right, the compressor side of each is identical, takes just as much power to run each. The mechanical drivers take different amounts of HP to run though.

[Pyrthian]

Super charger vs Turbo charger -
first off - if one was truly better - the other wouldnt exist.
for most applications - it DOESNT MATTER. its preferance.

super chargers have more parasitic loss, but have more consistancy & reliability. todays SC3800 will be around for a long time. todays high strung 4 banger turbos will be scrap in 5 years. <- general statement - obviously - its mostly a matter of owner care.

turbo chargers are more efficent, and offer much more flexability in design & levels of refinement.

[The Dark Side of Will]

Edit- You are right, the compressor side of each is identical, takes just as much power to run each. The mechanical drivers take different amounts of HP to run though.

Yeah, I should have said "the compressor of a centrifugal supercharger"

It should be noted that because the turbine requires more energy from the exhaust than the compressor puts into the intake, the turbine is being driven by some of the energy of the engine's fuel. It's like a mini-turbine engine with a pistons in the combustion chamber.

[crzyone]

They should make a centrifical supercharger with a 2 speed gearbox. Get that turbine spinning faster at low rpm. Or a CVT on a centrifical supercharger, that would be cool. Probibly make it quite bulky though, but you would get better performance at lower rpm.

[p8ntman442]

The point of a turbocharger is that the alot of its power comes from waste heat rather than drag on the crank, therefore its "free" hp where as everything the SC makes is derived from the crank.

[p8ntman442]

They should make a centrifical supercharger with a 2 speed gearbox. Get that turbine spinning faster at low rpm. Or a CVT on a centrifical supercharger, that would be cool. Probibly make it quite bulky though, but you would get better performance at lower rpm.

CVT turbocharger would be cool, but $$$$ if it were anywhere near efficient. Havent thought too much about it, but it may not be feasible, as you may not flow enough air.