i know people say the turbo is better for the 1/4 mile run. but what about a highway roll from like 40mph?

 

Ahh the old turbo vs SC debate......

It's a toss up, depending on turbo size and application. The SC is *instant* boost, the turbo will have to spool. Most people/kits run t3/t4's which can spool anywhere from 3500~6000 depending on how big the compressor is the displacement of the engine. Superchargers on the other hand can blow termendous amounts of hot air(roots style) which is bad for power. Also superchagers have whats called parasitic drag, IE it's take power to make power. Turbochargers on the other hand require very little energy from the engine, since they rely on the exhaust gases to spin the turbine. On the other hand.....wait i'm out of hands.

Not the best explanation.....

 

what if the supercharger has water injection intercooling?

 

There are basically two types of superchargers--positive displacement and centrifugal.

A turbocharger is a centrifugal supercharger that's driven by a turbine that converts the heat from exhaust gasses to mechanical energy. Belt driven centrifugal superchargers get their energy from the motor's crankshaft. The centrifugal types need to spool up before they start making mad power. The advantage of the belt driven centrifugal supercharger is that it provides boost in a more linear way, so it's easier to tune and tends to not run out of boost at high RPMs. Of course there are exceptions to every rule.

The positive displacement supercharger is always crank driven. Early "Roots" style chargers had no provisions for intercooling, but many modern ones do. The positive displacement supercharger's advantage is that it literally forces a certain quantity of air into the engine. They're the most linear, and therefore the most consistent to tune and run. The downside is that they have the most parasitic power losses.

For street use, a positive displacement supercharger can really wake up a 4-banger. You'll find yourself downshiftin less, and you won't need to thrash the motor to get the car to move out. The powerband will be wider and less peaky. Centrifugal superchargers tend to be peaky, and can cause your motor to have a dual personality--sluggish at first, then all the sudden tons of go. That's fun for a while, but less practical for the street. If you're racing, that drawback might not be as much a problem as it is on the street.

 

Smart kid, water/alcohol injection is a very good method of knocking down the intake temps on superchargers. I think i've seen peeps running that setup and some stepped up pulley S/C setups making very good numbers. Mostly you see that kinda setup on roorts type blowers. The centrifugal types can have I/C setups just like turbo's, tho those are a bit peaky/tempermental from what i've heard. The roots type will give you on tap power all the time.

Also with either form of F/I good tuning is key to the power and longevitity of the engine.

*edited* good info slow-n-low, but turbochargers and superchagers are 2 different items. Centrifugal type superchagers are belt driven same as roots, but are not connected directly to the head.

For examples of the 2 different types of superchargers, take a look at these

This is a Jackson Racing roots type S/C

This is a Vortech centrifugal type S/C

 

ya i wanted to go jrsc with water injection kit, mainly cuz its a daily driver

 

No, turbochargers are superchargers. The name is a contraction of "turbo-supercharger". The only functional difference is their power source. In fact, if you look at a turbo and a Vortech side-by-side, the similarities are obvious.

It looks like you're confusing mounting conventions with device type. While the stereotypical Roots blower is bolted to the top of a hemi motor, that's not what distinguishes a positive displacement supercharger from other types. Positive displacement blowers move a fixed amount of air per RPM, because the internal mechanism is sealed, preventing air from escaping. They have a fixed displacement. Centrifugal types use centrifugal force to build pressure, and air can leak back out at low RPM. That means they're not linear like positive displacement blowers; they have different efficiencies at different RPMs.

http://www.grapeaperacing.com/GrapeA...supertypes.cfm

 

simply put, turbocharger all the way.

turbocharger systems are designed to provide no less than 70% thermal efficiency. superchargers provide no more than 65%. thus lb for lb, the turbocharging system is more efficient per psi of boost.

additionally, superchargers being crank driven will provide full boost at max rpm. most are geared to provide a significant amount of boost lower in the rpm range, but a turbocharger is only limited by it's own inertia. a properly sized turbo application will provide full boost instantly, especially from a roll. the supercharger will only provide as much boost as the engine rpm happens to be at that time.


"turbo lag" aka spoolup is not nearly as dramatic as everyone talks crap about... only those who run Drag systems, which feature severely mismatched turbines, will the owner ***** about spoolup time.

 

I dunno my DRAG kit has worked wonderfully boost comes in around 3k and will hit full boost around 4k. Laggy turbo spool can be attributed to the turbo being mis-sized for your app, or it can be from the fact that BIG turbo on small engine's will always have lag. If you want daily drivablity small turbo's provide low-end power where you'll need it to be comfortable. However you trade off top-end and large power for it.

All DRAG, REV-HARD, MAX-REV or any of the bigger power turbo kits have turbo's that are t3/t04e's. A laggy turbo is a t3/60-1 or a straight to T4. Thats just my opinion however

 

Based on all the "Kill Stories" I read that feature cars unable to race from a standstill like drag racers do, I conclude that adding low-end torque can't help FWD drag racers. In that respect a little turbo lag is actually desirable for drag applications, right?