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Discussion Starter #1
:headscratch:Ok here is the deal... i race...not show the hp output on my car... i want to know what type of supercharger is best out of the twin screw, eaton m112, or centrifugal unit??? i dont want lag... form what i hear at the track i go to people with centrifugal unit has lag untill they build up boost is that true??? oh btw i have a 98 gt with 04 gt swap... so please let me in on the info... what are the true racers got to say about it???:scratchchin
 

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If you still have the stock guts in the engine, you are limited to the amount of boost you will get out of it. If you intend to seriously go racing with the car, what are your plans and goals?

In general terms, centrifugal superchargers are similar to turbochargers - as you size them up to get more power, the amount of time (lag) needed to spool them up to their full power potential increases. They WILL produce extremely high power spikes, all things done correctly, higher than the output from a good twin screw positive displacement blower.

Overcoming any racing disadvantage from lag in either case requires planning, driving skill, and strategy. Lag is less of an issue on launch, where the rpms can be allowed to climb to the desired point, but CAN be a problem when gear change time arrives. Automatic trannies are the prefered method for winning in this case, with shift points and torque converter ratings designed to keep the engine in the fat part of the power curve, though really adept drivers can make a 5 or 6 speed sing through the power shifts.

The new twin screws overcome much (but not all) of the top end advantage of the centrifugal blowers, and some of the peak of the turbos, but they really shine in the area of torque production down low. They have virtually no lag, and the engines behave very much like a much larger displacement engine, hence their "positive displacement" tag. For street use they are hard to beat, with their instant response and fat power curve.

Frankly, if I were building a dedicated, cost no object, all-out race car based upon a 4.6, I would be looking at a big turbo rig.

For a daily driver 4.6, cost no object, I would go with a fully built bottom with a big twin screw sitting on top.

For a street/strip car, I might choose a strong ProCharger blower. I like their internal lubrication system.
 

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I agree TripleBlack, ProChargers are the way to go if your going with a blower, 5.0 Magazines show some outrageous horsepower with these apps stock, 3 of my partners down here actually spray a 50 to 100 shot to avoid their lag issue. Might be a quick fix, well enough to get you in that power band a bit faster.
 

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Also turbos are required a cool down period of 45 sec. before you shut dow your engine. Meaning you can just hop out of your car you gtta be patient. Another thing you should consider is the RPM range. Where as the turbo runs off exhaust the s/c uses pullies, you can get more boost n less time with the s/c. Procharger would definetly be the way to go.
 

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Also turbos are required a cool down period of 45 sec. before you shut dow your engine. Meaning you can just hop out of your car you gtta be patient. Another thing you should consider is the RPM range. Where as the turbo runs off exhaust the s/c uses pullies, you can get more boost n less time with the s/c. Procharger would definetly be the way to go.
thats what turbo timers are for.they cool down after the cars turned off.
 

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If you still have the stock guts in the engine, you are limited to the amount of boost you will get out of it. If you intend to seriously go racing with the car, what are your plans and goals?

In general terms, centrifugal superchargers are similar to turbochargers - as you size them up to get more power, the amount of time (lag) needed to spool them up to their full power potential increases. They WILL produce extremely high power spikes, all things done correctly, higher than the output from a good twin screw positive displacement blower.

Overcoming any racing disadvantage from lag in either case requires planning, driving skill, and strategy. Lag is less of an issue on launch, where the rpms can be allowed to climb to the desired point, but CAN be a problem when gear change time arrives. Automatic trannies are the prefered method for winning in this case, with shift points and torque converter ratings designed to keep the engine in the fat part of the power curve, though really adept drivers can make a 5 or 6 speed sing through the power shifts.

The new twin screws overcome much (but not all) of the top end advantage of the centrifugal blowers, and some of the peak of the turbos, but they really shine in the area of torque production down low. They have virtually no lag, and the engines behave very much like a much larger displacement engine, hence their "positive displacement" tag. For street use they are hard to beat, with their instant response and fat power curve.

Frankly, if I were building a dedicated, cost no object, all-out race car based upon a 4.6, I would be looking at a big turbo rig.

For a daily driver 4.6, cost no object, I would go with a fully built bottom with a big twin screw sitting on top.

For a street/strip car, I might choose a strong ProCharger blower. I like their internal lubrication system.
I agree...

Set a horsepower goal. If it is over ~425 whp, build your shortblock first or get a kit that you can drop the boost at or below 10# of boost until you can get the bottom end done.

If you want the power down low, and don't want lag, get a good sized twin screw blower and make sure you upgrade the suspension and get some sticky tires.

If a twin screw car hooks well, and has equal hp to a Centri car, the twin screw should win in a drag race since it comes out of the hole hard. A higher hp Centri car will catch up to a lower hp twin screw once it is spooled up if there is enough distance to finishline left.

There are tons of variables to think about too...

Gearing
intercooling efficiency
driver skill
traction
tune

Take your time and decide on the whp goal you want to achieve. I researched online for 2 years before I ordered my blower and I still love it and grin when I push the gas and watch the needle go from "Hg Vacuum to Psi. :bigthumbsup
 

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cool down

thats what turbo timers are for.they cool down after the cars turned off.
If I had a serious turbo car, I would also have a Messiere electric water pump, and set it up to run off a thermostat, circulating water until the engine cooled down, even if the engine were turned off. This would help keep the bearings in the turbo alive in case I occasionally forgot and switched off with the car still really hot and the turbo spooled up.

Using full synthetic oil would also be a must for the same reason.
 

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im kinda partial to the twin screws. super practical for street, and strip. build ur bottom end, and get a kenne bell 2.1-2.6 liter. there wont be many competitive cars to race after that. definately build the bottom end though. my friend had a 2.1 KB on his 01 bullitt, he was only runnin 8 psi when he sent a rod through the block. it was 15 degrees out and he decided not to let it heat up before he stomped it:hihi:.
 

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I would say that he also might have raised the rev limiter a bit too much (or removed it altogether). Too many rpms (and bad tunes) kill more engines than does boost.

It might be unpleasant bouncing off the limiter, but imagine the alternative (ie, rods exiting the block).
 

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I agree with 3B's assessment of the question at hand.

The Kenne Bell I had was the absolute best for my purposes. The car never saw the track and very rarely got run wide open throttle except in 4th or 5th gear for a few seconds on the highway, mostly because of traction issues.


I will have to be 'That Guy' and correct one thing though. Positive displacement blowers get their tag from the fact that they are in essence positive displacement air pumps. They will move a given amount of air no matter what pressure they are pumping against whereas a centrifugal pump will move air to a given pressure no matter what volume of air that is.
 

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I will have to be 'That Guy' and correct one thing though. Positive displacement blowers get their tag from the fact that they are in essence positive displacement air pumps. They will move a given amount of air no matter what pressure they are pumping against whereas a centrifugal pump will move air to a given pressure no matter what volume of air that is.
LOL I always wondered who that guy was! j/k

True, but it all goes back to proper blower sizing too.
 

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Correction

I will have to be 'That Guy' and correct one thing though. Positive displacement blowers get their tag from the fact that they are in essence positive displacement air pumps. They will move a given amount of air no matter what pressure they are pumping against whereas a centrifugal pump will move air to a given pressure no matter what volume of air that is.
I agree with the definition, which is a darn good one. Engines (and the various power adders) are all about pumping air, either directly, indirectly or by literally SUCKING it into the engine. Positive displacement blowers are usually measured in liters for that reason. Its (sort of, and that is a deep subject all to itself) a way of doing some simple estimating, ie, adding a 2.1 twinscrew to your 4.6 creates a "virtual" 6.7 litre monster. Its why LS1 guys call it "cheating", LOL. Pressure DOES play a role, of course, but it is a RESULT of the turning of the vanes within the case rather than a cause. These blowers operate downstream of the throttle body, maf and so forth.

Centrifugal blowers and turbochargers are different beasts, and things like blow-off valves can make a difference. They ARE all about pressure, whereas volume for each turbine fan-full is pretty small, there are LOTS of them due to the rpms that fan is turning. Volume occurs as a RESULT rather than a cause. They usually operate upstream of the throttle body, etc. (though there are exceptions).

I scanned back up the page, and didn't see where anyone said differently, so I wouldn't view this so much as a correction than as a valuable contribution...

Unless I'm missing something?
 

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Size matters

LOL I always wondered who that guy was! j/k

True, but it all goes back to proper blower sizing too.
Absolutely. Mismatches are disasters. The air pump (aka "engine") cannot process more than the limiting factor (wherever that is).

This can be in the heads, valves, combustion chambers, cylinders, exhaust, intake, supercharger, turbocharger, or a combination of the above.

Usually it IS just "one thing", but whatever and wherever that pinch point occurs, the maximum flow through that point IS the maximum flow for the whole thing...

Else expensive things break, which also sometimes happens.
 

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I found a short tutorial that illustrates the differences pretty well if anyone is interested. You can see for yourself why the positive displacement types crank out the low end grunt and centrifugals don't by looking at the graphs.


http://www.pumpschool.com/intro/pd vs centrif.pdf
 

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Here's an article I did for AFM and public release that has some data about the various options, but also some interesting information about Eaton's Twin Vortice (twin screw) supercharger, which of course was just coming on the market when I wrote the article.

http://www.allfordmustangs.com/articles/Mustang_blower_tech.shtml

I have been working on another article about the new, tiny superchargers just entering mainstream use in Europe. They are roughtly 1/6 the size of the typical VorTech centrifugal supercharger, but are incredibly silent and efficient. They are designed to compete directly with turbochargers as well as larger conventional superchargers.

And they are looking at twin-supercharger rigs for some applications. I have been trying to figure out pricing, but that is still hard to determine, since they are only talking to the OE manufacturers right now.

One source I found (in German) mentioned that they cost only about $120 to produce.

The boogers are smaller than the old air pumps used on the Fox Mustangs, and those are the "large" ones.

Rotrex is now offering a larger version of their so-called "G" blowers for sale as a kit for Mustangs. I will try to find the data. Its pricey but extremely complete (being a German design, I'm not surprised). It is NOT the sort of wild twin install like the one I saw on a Ferrari, or the one on a BMW M type written up in the German press.

Speaking of wild twin supercharger installs...

http://www.ask.com/bar?q=twin+superchargers&page=1&qsrc=0&ab=0&u=http%3A%2F%2Fwww.autoblog.com%2F2008%2F05%2F01%2Fobsidian-sg1-800-hp-twin-supercharged-uber-stang%2F
 

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Discussion Starter #16
i have an engine in the shop to be rebuilt with all manley parts going to cost me a bit over 4 grand. im also runnig with 5sp not and auto trans. but like i said i want the performance. i want to show my track runs not dyno runs.
 
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