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Discussion Starter · #1 ·
With me not being any kind of expert on superhargers ... I was just wondering if the new kenne bell supercharger out for the 2v's would be better than centrifugal superchargers or any other root style supercharger. I plan on having a built shortblock and heads to run with a P/A application, but still use the car as a semi-daily driver and occasional run down the track/street race. Any help or opinions on this will be great!
 

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I don't think you can say the Kenne Bell Screw blower is better than a Centrifugal type blower, and I don't think you can say the centrifugal blowers are better than Kenne Bell's version. They both do the same basic job, but it’s when and how the boost is made that makes the difference.
The Kenne Bell blower is a positive displacement blower, which means you get power right off idle because the boost is already there. The twin screw blower makes your engine feel like it has a larger displacement than what it really is. They can make your 4.6L feel like a 6.0L engine. I prefer the Kenne Bell version over a centrifugal version because I want the power right off throttle, and thru the entire rpm range. Plus I plan on doing a lot of Auto-X so I want power in and out of the apex, and I want to do it without worrying about keeping the rpm’s sky high. On top of that, the screw blowers are pretty compact and fit neatly tucked between the heads.
The centrifugal version is nothing more than a turbo on a stick, basically, the higher the rpm’s the more boost it makes, just like a turbo, but without the turbo lag, because it’s more linear, and your not waiting for the exhaust to make it spool up. The centrifugal show's it's might at mid to upper rpm’s. At lower rpm’s most centrifugal don’t make much boost and much power.
 

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I spent the last 20 mins looking through threads trying to find the one with a link to a website which looks at all the different forced induction components. I cant find it, it was a while ago. Basically, it gave an honest look at how each different type works, and pro's and con's of them. Sorry I couldnt find it. Maybe someone else will see your post and put it up here for ya.

Silverstangs post is correct, I was just trying to get you MORE information. Personally, I would go with the KB cause I am a day to day driver, track time just to see what she runs.
 

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stanggt00 said:
I spent the last 20 mins looking through threads trying to find the one with a link to a website which looks at all the different forced induction components. I cant find it, it was a while ago. Basically, it gave an honest look at how each different type works, and pro's and con's of them. Sorry I couldnt find it. Maybe someone else will see your post and put it up here for ya.

Silverstangs post is correct, I was just trying to get you MORE information. Personally, I would go with the KB cause I am a day to day driver, track time just to see what she runs.
My bad, I should have provided a link for everyone...

http://www.superchargersonline.com
I think they have a article in the tech section...
 

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Generally,

Centrifugal blowers make more ultimate power than positive displacement blowers, they just don't make that power down under 3500rpms, but how often after launch does your car see under 3500rpms. Centrifugal blowers boost increases as rpms increase, so you might see 2# at 3000rpm, 5# at 4000rpm, 7# at 5000rpm and 10# at 6000rpms for example.

Posive displacement blowers make full boost down at like 2000rpms, so they will make 9# at 2000rpm, 3000rpm, 4000rpm, and maybe they start to taper off after 5000 or 6000rpm.

If these Kenne Bell blowers put out #s in the real world on the 2v engines like they are quoting, alot of use Centrifugal guys will be kicking ourselves for not waiting, but that remains to be seen.

They are making HUGE power on the 03 Cobras.:shocked

I think poitive displacement blowers will be better for scaring your passengers, but Centrifugals will be better in an all out race.

Howard
 

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Discussion Starter · #6 ·
Thanks a lot for all the input guys, this has really helped me in my decision on which way to go.

Zach
 

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Turbo vs SC

but without the turbo lag, because it's more linear, and your not waiting for the exhaust to make it spool up.
I have to disagree on the lag associated with the turbos. You can go to turbomustangs.com and find that with turbos you can be at full boost at 2000 rpms. Another plus for the turbo is the effeciency and the unlimited power, basically however much boost you want you can have. To give you an example in an application making 500 rwhp with a KB will make more with ATI (centrifical) lets say you can get over 550 with the right pulley combo etc, with a turbo you would be able to get to 700 with little effort. I have a built 4.6 and to make 800 rw my only option is a turbo. No other will do it not KB, not ATI only the turbo has the ability to get me there.
 

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another thing about the KB or ATI is once you get the boost to about 20psi they begin to make to much heat because of friction etc. To much heat equals lower and lower HP. Turbos don't have that problem.
 

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One minor thing I can add to this. When your referring to boost, which measures the pressure created by the power adder, it can be a little misleading. 10 PSI of boost on non ported heads and intakes will move less air than 10 PSI of boost on a fully ported head and higher cfm intake. Basically, with a fully ported intake system, 10 PSI would be equal to a much higher PSI on a non ported intake.
 

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here here! Right 10psi on none ported might see 30 rwhp where as with ported heads you may see 100 rwhp. It makes that much difference. Its all about flow, the more you shove in the more you have to be able to shove out.
 

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if you know how to drive even if lag does exist you can get around it. if you wanna go fast just keep it above 3k rpm's. i think turbo lag is just an excuse for the people who make superchargers, and people who can't drive.
 

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Re: Turbo vs SC

mytquik said:
I have to disagree on the lag associated with the turbos. You can go to turbomustangs.com and find that with turbos you can be at full boost at 2000 rpms. Another plus for the turbo is the effeciency and the unlimited power, basically however much boost you want you can have. To give you an example in an application making 500 rwhp with a KB will make more with ATI (centrifical) lets say you can get over 550 with the right pulley combo etc, with a turbo you would be able to get to 700 with little effort. I have a built 4.6 and to make 800 rw my only option is a turbo. No other will do it not KB, not ATI only the turbo has the ability to get me there.
Your going to tell me that 3feet+ of piping + intercooler + time for the exhaust gasses to spool up the turbine is not going to create lag???????????

O.K. from the website your brought up
Turbo Lag

A turbocharger uses a centrifugal compressor, which needs rpm to make boost, and it is driven off the exhaust pressure, so it cannot make instant boost. It is especially hard to make boost at low rpm. The turbo takes time to accelerate before full boost comes in, it is this delay that is known as turbo lag. To limit lag, it is important to make the rotating parts of the turbocharger as light as possible. Larger turbo's for high boost applications will also have more lag that smaller turbo's, due to the increase in centrifugal mass. Impeller design, and the whole engine combo also have a large effect on the amount of lag. Turbo lag is often confused with the term boost threshold, but they are not the same thing, lag is nothing more the the delay from when the throttle is opened to the time noticeable boost is achieved.

Turbo Boost

Usually measured in pounds per square inch, it is the pressure the turbocharger makes in the intake manifold. One of the ways to increase airflow through a passage is to increase the pressure differential across the passage. By boosting the intake manifold pressure, airflow into the engine will increase, making more power potential. Boost is also measured in Bar. One Bar equals 14.7 psi.

Boost Threshold

Unlike turbo lag, which is the delay of boost, boost threshold is the lowest possible rpm at which there can be noticeable boost. A low boost threshold is important when accelerating from very low rpm, but at higher rpm, lag is the delay that you feel when you go from light to hard throttle settings.
So your telling me that turbo's are making max boost at 2000rpms? I guess that must mean the person who has reached the boost threshold at 2000 rpms has a tiny turbo, which means your not making 700 hp with little effort. On top of that I don't beleive anyone is driving a 700-800hp car as a daily driver, which is the goal of the thread starter.
 

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96stang46 said:
if you know how to drive even if lag does exist you can get around it. if you wanna go fast just keep it above 3k rpm's. i think turbo lag is just an excuse for the people who make superchargers, and people who can't drive.
That's almost exactly what a guy with a turbo'ed integra said when he was comparing a V8 driver to a person with a import and turbo........

He said
If your a good driver, you know how to keep the rpm's above 3k and that's how you don't have turbo lag. The V8's are for people who can't drive and make a excuse for why turbo's have lag!
 

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Your going to tell me that 3feet+ of piping + intercooler + time for the exhaust gasses to spool up the turbine is not going to create lag???????????

I am not here to argue that turbos dont have lag , that is a fact but I can tell you that the lag is not caused by tubing lenth and intercoolers. That is like saying if two people are talking long distance coast to coast there is going to be a delay in the voices.
The tubing and intercooler may delay immediate airflow to the T-body upon startup but after that it is a constant flow. And the delay is only milliseconds. Everyone here has turned on a 50 FT water hose and experienced a delay but once the water reaches the oulet it is a constant flow. About the lag, that can fixed as well on a drag car with proper tuning. In the tune-up you have little or no timing down low and extra fuel. The lack of timing causes the fuel to be burnt in the exhaust also causing the turbo to build boost almost immediately.

You also said earlier that you like to enjoy power all through the RPM range. Well if you have ever seen a roots style blower on the dyno, which we have dynoed many. the results would be awesome power down low but the roots blower also loses its effectiveness pretty quickly as the RPMs rise.


Simple fact is all power adders have advantages and disadvatages. The main thing to consider is what application your power adder will be used for.
 

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My personal choice for forced induction is a KB twin screw, second choice would be a turbo rather than a centrifical (turbo with a belt).
I like the idea of power from idle, and KB blowers make some impressive numbers.
 

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silverstangs said:
The centrifugal version is nothing more than a turbo on a stick, basically, the higher the rpm's the more boost it makes, just like a turbo, but without the turbo lag, because it's more linear, and your not waiting for the exhaust to make it spool up. The centrifugal show's it's might at mid to upper rpm's. At lower rpm's most centrifugal don't make much boost and much power.
What are you talking about, comparing Turbo lag to a Centri lag.

Turbo lag is minimal compared to centri lag. You won't start building (key word building) boost on a Centri until 3000 rpm or so, depending on your setup, but in the meanwhile still putting drag on engine below that, whereas a Turbo will be seeing damn near full boost by then.

If you compare dyno sheets, you will see that a Turbo has a more linear power curve then a Centri which starts at 3000 and keeps rising.

You see much more usable power under the power curve then you do with a Centri.

I'll take that tubo lag anytime over the BIG Centri lag.

Keep in mind, we are talking about most daily driven cars here, Not a 91mm or bigger huffer.
 

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96stang46 said:
if you know how to drive even if lag does exist you can get around it. if you wanna go fast just keep it above 3k rpm's. i think turbo lag is just an excuse for the people who make superchargers, and people who can't drive.
even a good driver is gonna lose some boost between shifts....hence getting an automatic. and a local guy just got his 01 GT dyoned with 9# he saw 390 hp and 434 lb ft of torque with his KB...not too shabby if you ask me.
 
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