One reason i really don't want to go turbo is that my car is mostly driven around the city in bad traffic, i like being able to run away from small groups of cars when i need too and to me a s/c seems like a great idea. i hate having to wind my gears out b/c i dont need to be going 60+ mph on regular streets and if im trying to stay in the power band i dont have much choice so to me a s/c would be a nice gain of low-mid range power.

 

I thought supercharged rx7's are robbed of all there top end power?

 

I don't know if this is true, but 7's seem to be more powereful in the upper rpm's compared to other cars even if they're not turbo. So supercharging should give it instant power then domination in the high rpms as well. Turbocharging would give the car more power (especially highway racing). But, where ur drivin at "Staticguitar" i would recommend u get a supercharger.

 

yo that targa top is sweet!!!!! i want one on mine! anyone done it there fcs?

 

Not really. Superchargers mostly rob power across the entire powerband, but there are a lot of factors involved. Also, there are 3 popular types of belt-driven superchargers, and each has it's own characteristics. For example, here is a very generic boost profile. However, the Roots blower is not as good as it seems in this chart because it only runs at about 60-65% efficiency at a given boost level, while the other two run around 70-75%. If it makes more sense to think of it this way, the Roots supercharger will produce boost at low rpm's, but it heats up the air so much that the performance is not what you would expect at that boost level. This is why fast-spooling turbos, such as aftermarket BB turbos, or the stock 13B-T turbos, are usually better than a Roots blower.

 

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I've got both, a turbo'd 6port and a supercharged 6port, and sadly, the turbo beats it in all aspects, off the line, top end, etc, the supercharged car just can't keep up. With a larger supercharger this might be different, but my turbo spools so fast that it really doesn't make much a difference.

 

...subscribing to thread so i can read it later...

 

i love having all this knowledge from other arguing people, right at my fingertips, hey here's a sube ject change for you mechanics, my drivetrain is noisy in my custom 7, the previous owner said he had better driveshaft ends installed and its really noisy now, any tips, oh and is a short shifter worth $200, most specifically, the mazdatrix model?

 

do superchargers hurt reliablity at all, like i've heard turbos do?

 

Well, it obviously strains the motor a bit more, reliability is about equal, with the supercharger being a little higher since they run generally less boost.

 

can anybody direct me to somewhere where I can learn more about superchargers? I searched and found just people buying, selling and comparing...

 

http://www.howstuffworks.com is a good example, other than that there's a book out that's a good read, or just hit up google.com and search for supercharger setups or 'how superchargers work' and you'll end up finding good info about the different types.

 

Turbos and superchargers do not hurt reliability or longevity if they are run at reasonable levels for the build level of the engine. Even non-turbo engines become unreliable or short-lived at extreme power levels.

Corky Bell's "Supercharged!" book is available from most online book sellers.
http://www.amazon.com/exec/obidos/tg...=UTF8&v=glance

This website has good info:
http://www.superchargersonline.com/c...at.asp?group=2

 

why is it that it is more difficult to intercool the subercharger...is it because of the room the belt driven mechanism takes up...if you were to keep the supercharger "cooler" do you think the power yields would be different or for the most part...the same, being the effectiveness of the supercharger will be less than the turbo no matter what you do

 

im just curious because i have seen a few supercharged Fd's that put out almost 500hp...but i keep in mind that replaces sequential twins...but im sure it does effect the high end alot...also it works great in larger displacement motors i.e. 5.0s but from what ive read here its not as effective in small displacement high comp. motors like the 13b...that bothers me for some reason

 

It's all about sizing really, most people generally run a 1.3l/rev or less roots blower, or small centrifigal, a 2.3l/rev or higher lysholm (sp?) would probably make quite a bit of power. However, the cost for the charger alone is damn near $3000.

 

This only applies to Roots type superchargers. Since they are blowers and not compressors, the air is compressed after it leaves the supercharger. This means that the intake plumbing after the supercharger is technically the "compressor", and as such, this is where the air is heated by the compression. As the compressor, the intake plumbing needs to have a minimal length, and it must be designed such that the air is easily compressed. This makes it very difficult to intercool, and this is why you mostly see air/liquid intercoolers associated with Roots blowers, as an air/air intercooler would not be practical in most cases.

Centrifugal and Lysholm superchargers compress the air in the supercharger, as does a turbocharger. Therefore, the downstream plumbing is not as critical, and the air is heated prior to leaving the supercharger. An intercooler can be added anywhere between the supercharger and the throttle body.

The heat is produced by inefficient compression. The better the efficiency, the less heat is added to the air charge. Yes, a Roots blower and a turbocharger of the same efficiency would heat the air the same at a given boost pressure, which would yield the same resulting air density being fed to the intake manifold. For example, a 65% efficient Roots supercharger @ 10psi boost would deliver the same air charge to the intake manifold as a 65% efficient turbocharger @ 10psi boost.

Why would it affect the high end?

Not true. A higher-efficiency device works better, regardless of the displacement.

 

While I own a NA Rx7, I also own a supercharged MR2. It has a roots type supercharger and an intercooler. It is currently running 12 PSI of boost and I can tell you I only have to wait for my foot to reach the floor for full boost.

Yes, a turbocharger is more efficient than an equivalent supercharger but these things are never equivalent. I could use a bigger intercooler and have intake air temperatures that are the same for the same amount of boost. You should instead be comparing Dollars per HP and if you get a used SC the cost isn't that bad in comparison to a used turbo.

Most people never get that last 15% of power/efficiency that their engine is capable of and nobody gets that last 15% without destroying a few engines along the way.

A roots type supercharger is a very acceptable alternative for less than 15 PSI of boost. For over 15 PSI a turbo might be the only way to go but I am thinking about sequential SC on my MR2.

My personal opinion is that the heat stress and back pressure caused by a turbo is worse than the parasitic drag of a SC.

ed

 

thanks for clearing that up evil

 

personally, i would love either a supercharger or a turbo on my n/a, anything except an electric 1psi turbo :-P