ponyman

streetrod

They are both excellent choices. It all depends on what you want to do with the car.

mach1

Interesting thread! It would be nice to hear from someone who has owned both. I'll stay out of this one for that reason. I've been told that the con on the turbo side is that they are somewhat temperamental and inconsistent for any bracket type racing.

MustangJohn09

found this:

My vote is for a twin-screw Positive Displacement Blower. Both the Saleen, and KB are twin screw designs. The adiabatic efficiency of a twin-screw far surpasses the Roots or the Centri style. This is the overall effeciency of the blower. Basically it's ability to make hp with less boost/less parasitic load. The only other power adder that comes close is a turbo setup.

As for the Roots style, it is also a PD blower, but an older design. A roots is a "looser" fit than a Twin-Screw blower so it has less drag under cruise, but has more "blowby" during high boost/loads, so it's less efficient under load. Anyway here are some comparisons for you:

1. Twin Screw pros:
a. Mild mannered, easy to drive fast, very predictable, linear power curve
b. Quieter in non-boost situations
c. Huge low end torque (400 ft-lbs at 2800RPM) no need for lower gears and lower MPG
d. More usable power on the street due to torque and linear power curve. On 90% of my "Street Races" the other person gives up in the first 100 ft because I "Frog hop" them sooooo Bad. I usually start at 2000 RPM in second gear and the race is over by 5500 in second!!! I never have to go over 75 MPH!!
e. Easy to install and maintain. ONE belt and oil change every 50K miles.

2. Twin Screw Cons:
a. Expensive 4-6K for basic setup
b. heavy. Adds 50-60 lbs to front end of car.
c. Harder on driveline components. Huge low end torque is a bit more stressful on stock components.
d. Hotter. Engine will suffer a bit from "heat Soak" due to extra metal casing from S/C
e. Less MPG. Expect 1-2mpg less overall.
f. Limited High HP potential. (There the law of diminishing returns)
g. "Seem" slower because of very smooth, linear power delivery.

Centrifugal S/C Pros
a. lighter (smaller components)
b. cooler. (also do to smaller components) Less heat sink
c. Less expensive ( about 3.5 -5.5K for good kit)
e. Higher HP potential. (Centi S/C is basically a belt driven Turbo)
f. Get a "Rush" when the power comes on

Centrifugal S/C Cons
a. very troublesome to install. (Many pieces, hoses clamps, fittings, brackets, etc) Look at some of the pics of a Twins screw kit and then look at a Centi kit.
b. higher maintance costs, and time. Lots of fitting, clamps, brackets, etc to get loose.
c. Lack low end torque. Have to "spool up" to get power.
d. Less driveable, more unpredictable power delivery. Harder to control especially in traction limited invironments. A twin screw with good tires will have better traction even though there is more torque because the power delivery is even and controlled, not "on -off" like a centi, or a turbo.
e. Noisy. (All around the loudest of all three discussed here)

Turbo Pros:

a. Cooler (turbo is not doing much when not in boost
b. better MPG (no parasitic draw when not in use)
c. Very high HP potential (U can really turn up the boost on these!)
d. Quiet, even in boost they are very quite
e. Driveability is good. They do have some of the on-off like a Centi S/C but can be controlled easier with boost controllers.
f. Not as hard on engine, driveline components.


Turbo Cons:
a. heavy. Usually as much as twin screw because of all the plumbing/piping involved
b. very troublesome/time consuming to install
c. Also more maintenance hungry. (pipes fittings, hoses etc)
d. No torque down low. (have to spool up).
e. Expensive. Good turbo kits are 6-8K
f. harder to tune

So there you have it. Basically it really boils down to what you want to use the car for. If you want a fire breating 1/4 mile beast, get a Centi S/C, you'll get the most bang for the buck, but loose streetability, and will work on it much more. If you want quiet, super High HP, best MPG, then get a turbo. If you want a "street killa" that will kick most people in the ditch and still provide good daily "Stock like" driveability, and be the most maitenance friendly, get a twinscrew!! I've owned turbo cars before, and I'll tell you, the twin screw is the best fit for all around daily street use with the occasional 1/4 mile jaunt. I wouldn't have anything else.

ponyman

Thanks john

I was looking at the saleen SC, but the new KB 2.6 seems a better choice. Now, it is pretty much between that and a turbo.

I was quoted a price of 5700.00 for a turbo + 450.00 for install at a shop down here

I know the KB does not need to spool up, but how much of a lag is there really on the turbo when spooling?

I would eventually like to take this to the strip for some run times.

I also figure in building the bottom of the engine along with possibly getting some work done on the tranny as well.

cameron55

Nice write up. Should be a sticky

gtcs722

So what all is involved in maintaining a turbo? Pipe corrosion? Fittings cracking and needing replacing? Does the turbo require changing the bearings every so often? Would ceramic coating the pipes help cut down on some of the underhood heat? Does all that piping get loose every once in a while?

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07SatinGT

I have owned a few aftermarket turbo kits on other cars. I personally disagree with the statements of no torque down low, that all comes down to properly sizing a turbo for the application. I also feel that launching with them too is a slingshot so long as you have your car setup such as with a stick you get a 2-step to load up the motor and build boost or with an auto a transbrake to again load up the motor to build up boost. I do agree with all the other pro/con statements on them though.

Typically you end up with a lot more maintenance, you do not understand underhood heat until you experience these things The ceramic coatings help out a ton though. You end up with a lot more silicone pieces in the system to connect a lot of your pipes, while this is the potential of added maintenance in itself I honestly do not recall ever breaking one or having it wear out but could see it happening. The clamps typically do not back off, now the kits I have had with aftermarket headers you sometimes would be dealing with the need to retighten header bolts every so often, I do not see that happen much at all with 2V/4V kits so optimistic the 3V kits are the same. Cracking in headers is always a potential worry, often comes down to poor design of the header or poor materials choice, typically design though. Oiling can sometimes be an issue, the turbo needs oil to survive but send in too much(seen this happen on a few 2Vs) and you smoke or worse yet do not get your drain line right and it smokes. As far as wear and tear on the motor I do not think that is much different than with an SC, one could even argue with an SC having a belt pulling on the crank might cause premature main bearing wear but that would be a useless argument IMHO.

For me it would be a tough call as to which I would go with. I think from a smile per dollar aspect it is just hard to beat the SC's like the KB although once you factor in the cost of long tubes with that SC you really are not spending much different than a turbo kit.

s197muscle

I think turbo maintaince is over stated, if they took that much more maintaince then they wouldn't come from the factory on so many vehicles.

Pipe corrosion can happen anytime stainless pipe isn't used, buy a quality kit with all stainless piping and you have nothing to worry about.

Any s/c or turbo will require the bearings to be replaced at some point. It is much easier to find a shop locally that specializes in turbos than it is to find a shop that knows anything about a twin screw.

Ceramic coatings will help, but I haven't noticed excessive under hood temps with my car. Also, ceramic coating will be dissolved by race fuel if you ever use it and if you don't have stainless pipes then they will rust from the inside out.

You will need to tighten the clamps on any centri or turbo, but it's not that big of a deal.

blackstang

Turbo kits have evolved and many of the problems that existed with early kits don't apply anymore. The Powerhouse kit had over a year of R&D. As others have mentioned turbos can make more power with less fuel than any S/C.

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