Turbo Or A Supercharger example essay topic

Ok, we " ve seen it brought up a million and one times, so, I'm going to give my take on the whole turbo vs. supercharger argument once and for all. Honestly, both devices ROCK. They essentially do the same thing (which is pressurize the intake) when it comes down to it. Arguing that one makes 'more power' than the other is utterly redundant, as I re-iterate that they both essentially do the same thing. (Look up redundancy in the dictionary and it will say 'See Redundant'.) Anyways, I'm going to write this blurb based on the assumption that anyone reading it has grasped the basic concepts of how a turbocharger and supercharger work. Typically, the argument is that a turbo makes more power than a supercharger, which is not entirely true.

For instance, the Lysolm (aka 'screw-type's supercharger, known as the PSI in Top Fuel) was the choice of forced induction for Top Fuel cars for years until they were banned for giving an unfair advantage to the cars using it. If it's good enough for Top Fuel, it's good enough to make some pretty good power on a street car. Now, don't get me wrong. I'm not telling anyone to run out and buy themselves a supercharger right now.

In fact, I'm not even implying that it's better than a turbo. I'm just making a case for it. Just as I'll make a case against the idea that turbos are all about lag and disproportional power curves. That's not entirely true. A turbo compressor that is well matched to the motor and tuned properly can result in a car that makes power smoothly over a broad power band. Per a conversation with Texan, the Audi R 8, a Le Mans car running in the LMP 900 class, is a good example of a turbo car that drives like a very powerful all motor car.

Admittingly, both Top Fuel cars and Le Mans cars are not the best examples of your everyday street turbocharged / supercharged car, but it's to make a case that either device can be good IF the car is properly tuned with it. Most of the myths about turbochargers and superchargers come from people that buy 'kits' and slap them on their cars without any real tuning. So how about Honda cars? Why does the turbocharger seem to be the definite forced induction of choice for these small inline fours that barely have enough displacement to hold a two litre bottle of soda?

Because current turbo kits have more options and more room for expansion. Currently, the almost limitless availability of different sized turbos and inter coolers allows for a great deal of very detailed tuning. There are turbochargers galore that can be matched to suit an engine's flow pattern and needs, with a plethora of inter coolers available to compliment the compressor of choice. Most superchargers just don't have that option. (I'm mainly talking about Roots based superchargers. I've touched on the reason why I feel that centrifugal superchargers are poorly matched to the small displacement motor in an article in the Supercharger Forum.) Adiabatic efficiency is supreme when it comes to a boosted intake charge, and there's no getting around the benefits of an inter cooled setup.

In fact, other than a motor's limitations regarding the amount of power it can hold, the only other limiting factor when it comes to boost is the amount of boost you can make before the intake charge is heated so much that you see a loss in power. An inter cooler allows for a cooler charge after the air is compressed, which allows for more compression, which, in turn, allows for more cf m of flow from the compressor. More air being moved is always a good thing. Why?

(Air + proportional fuel) x being burned = Heat/3 = Power produced So the more air that goes in, the more fuel you can burn, and the more power you can make. In that respect, it doesn't matter if that 150 extra cf m at 4000 rpm comes from a supercharger or turbocharger. 150 cf m at 4000 rpm is 150 cf m at 4000 rpm. However, the real important stuff happens somewhere along the way between the turbo / supercharger and the head. Boost is that cf m of air being compressed in the plenum, and how dense that intake charge can be is very dependent on how cool you can keep it. So we understand how an inter cooled turbo setup is beneficial, right?

Good. With that said, provided that both the turbocharger and supercharger producing the same cf m of flow that isn't inter cooled, you " ll see similar performance out of either. (Admittingly, the draw from the crank by the supercharger will show a slight drop in power in the end.) Let's look at another factor we should take into consideration. Altitude. As everyone knows, the higher the altitude, the lower the air pressure. How does that relate to choosing between a supercharger and turbocharger?

Taken into account that the devices relies on a supply of ambient air being fed through it, the relative air pressure can make a gross difference. As a general rule, turbos aren't affected much by altitude, provided that the waste gate is venting well below surge limit. The waste gate is controlled by pressure in the intake tract and will allow the turbo to continue to make boost until a pre-set limit, which is when the waste gate will begin to vent exhaust gasses to prevent excess pressure. So, in layman's terms, a turbo set up to make 12 psi in the plenum will make 12 psi, regardless of ambient air pressure. On the other hand, a supercharger will always move a given amount of air, and, given lower air pressure, will not compensate by spinning up to a higher rpm than the engine dictates.

That gives the turbocharger a definite advantage in that respect. To be fair about it, though, turbochargers do have boost thresholds. Under a certain RPM, there just won't be enough exhaust gasses to make boost. Whereas the low RPM positive displacement pump will make boost off idle, the turbo REQUIRES engine load to spool up. When I said that the turbo could make a wide range of power smoothly, that didn't mean that all it's weaknesses could be eliminated. It just meant that some of them could be compensated for.

A smaller turbo could provide boost earlier in the RPM range, and could provide more than enough flow to cover a good 5000-6000 rpm range before you hit compressor surge. (It can also reduce lag and make the car feel very responsive to the throttle.) Good tuning could reduce boost 'spike' and can make power production feel even and natural. But you can't get around boost threshold. You need a certain amount of load to spool up the turbo.

That's just the way it is. So far, as a sum of the whole, the turbocharger definitely has the advantage over the supercharger. So why supercharge if the turbo is so much more effective and versatile? Simplicity. A turbo can make smooth power reliably if tuned VERY well. The dynamics behind setting up a supercharger are much simpler.

With parts that compliment the nature of the blower (i / h /e, cams, breathing stuff), it's all a matter of tuning the right timing and air fuel. It is that much harder to combine parts to make an effective turbocharged setup. (More options = more complex. Look at the difference between setting up your high-tech MP 3/DVD playing car stereo vs. your dad's big button and knob AM only car radio.) In the real world of a daily driven street car looking for added power, there's nothing easier than bolting on a supercharger. Add in the natural limitations of the motor governing the amount of boost it can handle, and the amount of power a positive displacement pump provides begins to seem less disappointing. In a daily driver, the supercharger is the epitome of useable power.

Throw in the use of a Lysolm, such as the Rimmer kit for the Civic Si, and you " re looking at a LOT of useable power. So let's wrap this up. What's the bottom line? EITHER a turbo OR a supercharger would be a great way to add bolt-on power. The one you use solely depends on your preference, how much money you have to spend, and how much time you have to dedicate to your project. Either a turbo or supercharger requires tuning to put the power it makes to it's best use.

Just because you choose a turbocharger doesn't mean that you have to sacrifice responsiveness, just as a supercharger doesn't mean that you have to sacrifice good power output. I'll admit that the turbo is definitely the poster child for a serious race tuner, but I wouldn't discount the supercharger, since most of you people reading this spend more time on the street than the track.