TURBOCHARGE or SUPERCHARGED - The $64 Question

[csx4910]

CHANMADD, If someone doesn't have the gonadonal (balls) fortitude to go over 100 mph - they have no business owning a cobra or any other car of decent quality

[65SC]

Originally Posted by fordracing65

That set-up and look is actually my favorite look for a big block cobra.

had the same SC on my CSX, made 650.5rwhp

[65SC]

Originally Posted by olddog

A twin screw compressor and a roots blower are totally different technologies. Note the names compressor and blower.

Twin screw compressors are used in industry to compress air, well over 100 psi. A roots blower cannot get anywhere near that pressure. Anything a roots blower can do, a twin screw compressor will do with less hp consumed and less temp rise in the air. Not to mention the compressor can generate pressures that the roots cannot get to.

the FR TVS 2.3 is a very nice roots blower that can stand toe to toe with FR Whipple 2.3 twin screw

[2FastCobra]

Here is a Good Forced Induction article http://www.snowperformance.net/produ...le-pdf-106.pdf . Turbo is the way to go!!! I have put superchargers on many different cars over the years, I have had Vortech's, Procharger's and 2 Kenny Bell units, none could compare to a properly sized turbo. I went with a turbo on the Cobra to help quiet the exhaust down and for the power. One thing that some are forgetting is that turbo's are dependant on load to make power, with the low weight of my FFR the turbo self regulates its power, if the car is moving well at 600rwhp in the lower gears than the turbo will not be under as much load and will make only the power that is needed to keep it moving and as the car gets into the higher gears (more load) and starts meeting more wind resistance the turbo will start making more power. In first gear my 2,270 pound car makes around 7-8 pounds of boost, in 2nd gear the car makes about 11-12 pounds of boost and 3rd gear up the car is under more load and will make 20+ pounds. Turbo's like tall gears, I am running 3.08 rear gears in my car, it is not to loud and with all the torque the turbo makes the car is always in the sweet spot. With drag radials and a well set-up suspension the car has very little wheel spin. If you have good traction at the track and are loading the turbo you will be making more power. Superchargers are rpm dependant and will make the same power in each gear as the rpm climbs. I am able with my turbo to make over 850+ HP on pump gas (injecting a little methanol). My
My car is making 924rwhp, 986rwtq at 18.3 psi, I am running 22-23 psi now and it is a blast to drive. Here is a link to my you tube dyno video. Dyno tune with Steve Petty.wmv - YouTube
Any power adder that is used on these lite weight cars will blow your mind!!!! Good luck!!

[2FastCobra]

posted twice

[2FastCobra]

My exhaust comes out the turbo into 5 inch pipe then splits into 2 3.5 inch pipes that run to each side of the car and dump into my side-pipes with thrush 3.5 inch glass packs. My FFR is quieter than my last Mustang that did not make half the power.

[fordracing65]

Thats some serious power, I love a small block turbo, all the guys around here also run one turbo instead of 2, with the technology these days it makes sence, way to go.

[Thor maine]

I think the rule of thumb still holds true.If it's a diesel TURBO . If it's gas BLOWER. For a turbo to work really well(in a gas engine) has to be computer control and variable pitch or multi turbo system.Diesels have so much low end torque who cares that the turbo may lag(not in todays computer controlled diesels). Blowers start as soon as they start to spin.Go with the blower. But how much horsepower can you use?

[2FastCobra]

If a turbo is sized to the motor properly it will have no more lag than a supercharger, a lot of the time if set up and tuned right it will be at full boost before the supercharged motor that will be waiting for the motor to turn faster so it can start making boost. You also need lower gears to make the motor spin faster to get a supercharged motor into boost, with a turbo taller gears are better and with the taller gears and all the torque you will be shifting a lot less. My car has 3.08 rear gears and 4 gear will go to 160+ mph and I still have 5th gear. Not trying to Dis any supercharger guys here, just tired of hearing the same old turbo's have lots of lag argument, it is just not the case anymore. Turbo lag is from 8:1 compression 1.5 liter import motors with old school turbo's that had heavy impeller wheels. With the low weight of most of our cars, any power adder will be a blast. Just pick the type that will fit your needs and go have fun.

[lovehamr]

For those throwing silly words about, like "blower" as though they have some special meaning outside of periodical literature, the following are just two pages among many that are worth reading.

HowStuffWorks "How Superchargers Work"
Supercharger - Wikipedia, the free encyclopedia

"A supercharger is any device that pressurizes the air intake to above atmospheric pressure. Both superchargers and turbochargers do this. In fact, the term "turbocharger" is a shortened version of "turbo-supercharger," its official name.

The difference between the two devices is their source of energy. Turbochargers are powered by the mass-flow of exhaust gases driving a turbine. Superchargers are powered mechanically by belt- or chain-drive from the engine's crankshaft."

[olddog]

A blower is a real word that has real meaning. There are many types of blowers, centrifugal, turbine, lobed (roots). There are thousands make that millions of them used in industry. Your furnace most likely has a blower in it.

It just so happens that a couple types of blowers are used as superchargers, as well as compressors. I don't understand what is silly about discussing a blower used as a supercharger.

[lovehamr]

Originally Posted by olddog

So the best cam choice for a turbo verses a blower is a bit different.

I only said that because of its use in this thread and think we need to be on the same terms if we are going to be understood in our technical usage. The term "blower" is commonly used to define a device placed on engines with a functional need for additional airflow. The term blower is applied to rotary screw, roots-type, centrifugal compressors and turbo-superchargers when utilized as part of an internal combustion, forced induction, system. What I mean is that writing something like this is kind of silly because a "turbo" IS a "blower" regardless of the colloquialism that a mag like HRM might apply at any given time. And here it is again:

Originally Posted by olddog

A twin screw compressor and a roots blower are totally different technologies. Note the names compressor and blower.
Twin screw compressors are used in industry to compress air, well over 100 psi. A roots blower cannot get anywhere near that pressure. Anything a roots blower can do, a twin screw compressor will do with less hp consumed and less temp rise in the air. Not to mention the compressor can generate pressures that the roots cannot get to.

Here again, the verbiage is misleading at best and wrong at worst. A supercharger is an air compressor used for forced induction of an internal combustion engine. Those methods vary but that IS what they are. I will agree that a twin rotor old style roots SC cannot match the efficiency of a Lysholm (twin screw.) But to say that it’ll do anything that an older roots type will do is equally wrong because the Lysholm, though capable of higher PSI cannot match the older roots in volume. And you only have to look as far as your own post to see an example:

Originally Posted by olddog

If this is an absolute fact in all circumstances, then why is Top Fuel running blowers?

I’m assuming that you’re referring to roots or twisted lobe roots types here. Of course they aren’t running Lysholms, turbos, centrifugal, sliding vane or scroll types. Of course there is a reason for that. The oxygen content of nitromethane enables it to burn with much less atmospheric oxygen and the cooling effect of all that fuel attenuates a good bit of the compression heat. For those so inclined here you go: 4CH3NO2 + 3O2 → 4CO2 + 6H2O + 2N2. In short, what they need is a whole lot of intake charge moving fast and at boost pressures approaching 75psi. That’s right, 5.0 bar.

All that stuff is not really applicable to us but the simplicity of the design IS VERY applicable as the manufacturing of a roots type is easier and thus less expensive than any other type. In this case, what are we talking about? 15psi and up for expected boot pressure? Or are we most likely talking about 5-10psi? If it’s a street car but you’re still going for the ultimate power or something like that then there are other choices. However, if it’s a street car and you are looking at moderate boost levels (say 7psi or less), on an otherwise unchanged engine, you can still expect a 40%+ increase in power with an old reliable roots without breaking the bank. Then your back to “will it fit under my Cobra’s hood?” I know a roots would never fit under my BB Cobra’s hood.

But on a SBF? Hmmmmmmmmm, could be……………

As a side note, I may be jaded because I just put a TRD roots type SC on our newest Toyota truck and the difference is amazing!

Steve

[olddog]

I'm not trying to argue, or for that matter even claim to be an expert. I have 33 years practical experience in industry. We use roots blowers to push (and in some cases pull) plastic pellets from Silos several hundred yards into the factory. We also operate twin screw air compressors. We even have multi-stage turbines. I have combined that knowledge with my favorite hobby engines. My intention is to share my understanding, and I try to not lead people astray. I can be quite anal at times. We agree more than we disagree.

Is the technology on the Toyota truck a root blower with twisted rotors or is it a true twin screw compressor (the area of the screws actually reduces and compresses the air)?

[lovehamr]

OK, I think I get where you're coming from. You're coming from an industrial take and calling a Lysholm type a compressor because it internally compresses the air and a roots type a "blower" because it has no internal compression?

That makes sense actually as we use large (think 10/71 size as I have no other frame of reference) superchargers to evacuate bullet fragments from our range traps. So I'm thinking the suction that they can produce must be pretty good along with the volume moved.

Sorry OD, I wasn't thinking about industrial apps.

In answer to the Toyota question; it's a modified, or twisted rotor type, roots. Here are a couple of pics of the rotors. You can see that the compression would be external, a byproduct of moving more air.

[olddog]

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[olddog]

Yes. Another difference is that a lobed blower moves air from one side of the case to the other side. The screw compressor pulls air in at the end of the case, them moves the air longitudinally down the screws, and the air exits the opposite end of the case.

The picture you provided is perfect to see that there is a leak path back through where the two rotors inter-mesh. The air is pulled around the outside in the open void in the rotor. Some air slips by between the case and rotor too. This is what limits the pressure capability of the lobed blower. The slippage also adds heat to the air.

Straight lobes are much simple (cheaper) to make, but the air output pulses. They sound similar to a engine running. The twisted rotor gives a much smoother steady flow of air. I was told by an old time racer that they used to time the straight lobe blowers (the twist didn't exist yet) to the engine to get the pulse to hit (I think) just before the intake valve closed to pack more air into the cylinder. I have no idea if that is true.

I have seen Teflon strips added to the rotor tips, in engine applications. This is supposed to seal to the case. Not sure if it is claimed to seal where the rotor inter-mesh. No doubt it makes a big improvement, but I doubt it is a perfect seal. It reduces air temp and increases pressure capability. For industrial use where things tend to run 24/7/365 they wear out too quick. We have none of those.

As for your use of sucking the bullets, we do that on short runs for resin pellets. I'm not sure what the maximum vacuum is, but I'm certain it is way less than 1 atmosphere or no one would bother with water vein vacuum pumps. I would guess 1/3 to 1/2 an atmosphere.

Anyway congratulations on the Toyota. I'm sure it works well for you.

[Luce]

You blower supercharger guys who haven't owned a non 4 cylinder turbo have no idea how nice they are and how they pull from the bottom up. My last fun car was a 2004 SL 600 with the twin turbo 5.5L V12 and Rentech tune. From memory, it put out 750 ft-lbs from 1500 RPM up. It had a torque curve that looked like Abe Lincolns top hat. You could add 1/2 throttle on the freeway, and within .25 seconds, you had full boosts and pulling past anything WITHOUT downshifting. If you floored it and were going less than 45MPH, it would drop into 2nd and lay rubber. (actually, the nanny only let it continuously chirp)

That's something you don't get with a supercharger, and don't come close to getting with a paxton type centrifugal belt driven compressor.

And if your running a roots type blower with no charge cooler, your waisting your time and money. By the time you do all you have to do to prevent detonation, and subtract the HP consumed by the blower itself, you've gained almost NOTHING but increased your fuel consumption by 75%.

Yea, I pull no punches after a few beers.

[Flygirl]

Seems like a supercharger would be lots more linear in its power delivery; that'd be my choice if I wanted that much power in the first place.

Personally, I'd avoid the expense of either, but I'm a simple gal.

[Blue66]

We have used both over the years. Turbo's to us are the way to go.. Quiet, easy to install, an go "pretty good. I am old school but GM opened my eyes a little in 86/87 with there little V6 turbo Buick GN's. Reliable, smooth, pulls like a freight train, an gets good gas mileage to boot. Takes a lot power to spin a supercharger. Turbo's are free wheeling an only gets used when ya put down the gas pedal.