Ive never owned a twin screw, or roots type blower, but ive heard that in the 4.6, the power curve seems to nose over pretty bad in the midrange. I know ill be sticking with a centrifugal type like the Vortech.
Look especially at the following (Post #16 by Birdieman)
Quote:
ORIGINAL: Birdieman4
I have owned and tuned a centrifugally blown car as well as a twin screw car. I have had a lot of time in both cars. The biggest reason why I say go twin screw is because of the much fatter powerband. A centrifugally supercharged car's hp is directly dependant to its rpm. A twin screw car isn't. Because the power comes in A LOT sooner in a twin screw car vs a centrifugal car, it makes it very streetable but very fast at the hit of the throttle. What I mean by that is you can haul ass all day in a twin screw car and never exceed 4000 rpms. In a centrifugal car, your big power starts at 4000 rpms. You get the power where you need it with a twin screw for the 4.6 motor- down low. But, you also get it in the mid to high range as well. With a centrifugal blower, you get it up high. As most peole with centrifugal blowen cars do, they add really short gears to help keep the car's rpms up high all the time. It makes the car less streetable. With a twin screw car, you can run taller gears and still get through your rpm range very quickly. I like having a freeway car, gear wise. -My personal preferance. The twin screw allows you to be able to have the best of both worlds.
Thanks DonW, your car is absolutely gorgeous by the way.
I heard that info on the twin screws by a local guy that strictly does mustang performance, but ill see what hard evidence if any I can find to back it up.
That last post makes good sense, the only thing I dont agree with is the statement that centrifugal type blowers dont come on until 4k rpm. In my experience with them, the usual rpm range for it to really hit hard was between 2500-6500. Of course twin screws are always in motion so the power band starts earlier. Anyway, ill try to see what I can dig up to prove validity to my prior post.
Thanks DonW, your car is absolutely gorgeous by the way.
Aww shucks, thanks!
Quote:
ORIGINAL: nitrojunkee
I heard that info on the twin screws by a local guy that strictly does mustang performance, but ill see what hard evidence if any I can find to back it up.
That last post makes good sense, the only thing I dont agree with is the statement that centrifugal type blowers dont come on until 4k rpm. In my experience with them, the usual rpm range for it to really hit hard was between 2500-6500. Of course twin screws are always in motion so the power band starts earlier. Anyway, ill try to see what I can dig up to prove validity to my prior post.
I tend to agree with you on the "4k rpm" statement to a degree. The dyno curves I've seen look like they come on on the low-3000 rpm range. I am still in "decision mode" myself, although I am definitely leaning towards the Saleen SC right now. I originally wanted a centrifugal SC, but have waffled back and forth a couple times. I want to gather as much info as I can before I put one on. Anything you can add to the pro/con debate would be appreciated. The more info we have, the better choices we can make for our own cars.
Ive never owned a twin screw, or roots type blower, but ive heard that in the 4.6, the power curve seems to nose over pretty bad in the midrange. I know ill be sticking with a centrifugal type like the Vortech.
HUH?!?! If jumping to over 400hp and 400 fp.lb tq at 2500 rpm and staying there until 6k is nosing over, then you should go with twin turbos. Centrifugals are dyno queens ( no offense lostsouls ). Yup, they make horsies, and they continue to make them up to red line, but the torque is pretty weak in comparison. Plus, you have to get pretty high up in the rpm range to get the horsepower. Now if you're going to run at 5k+ all day long, then yea, they are great.
I have owned and tuned a centrifugally blown car as well as a twin screw car. I have had a lot of time in both cars. The biggest reason why I say go twin screw is because of the much fatter powerband. A centrifugally supercharged car's hp is directly dependant to its rpm. A twin screw car isn't. Because the power comes in A LOT sooner in a twin screw car vs a centrifugal car, it makes it very streetable but very fast at the hit of the throttle. What I mean by that is you can haul ass all day in a twin screw car and never exceed 4000 rpms. In a centrifugal car, your big power starts at 4000 rpms. You get the power where you need it with a twin screw for the 4.6 motor- down low. But, you also get it in the mid to high range as well. With a centrifugal blower, you get it up high. As most peole with centrifugal blowen cars do, they add really short gears to help keep the car's rpms up high all the time. It makes the car less streetable. With a twin screw car, you can run taller gears and still get through your rpm range very quickly. I like having a freeway car, gear wise. -My personal preferance. The twin screw allows you to be able to have the best of both worlds.
Let me add some clarity to the 4000 rpm centrifugal thing. It didn't mean it to sound like centrifugally blown cars start making boost at 4000 rpms. They start making BIG power at 4000 rpms. In my procharged car, I start to make boost at around 2500 rpms. At 4000 rpms is where I start to make big-ish boost (5-6 psi). There is nothing wrong with a centrifugal set up on an 05 gt. I just happen to like the power curve on the screw set ups better, and not having to depend on rpm for boost makes the car very user friendly on the street. The 'fun' factor of the twin screw is huge. I am just reporting my personal experience with both types of blowers.
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