It's hard to beat a junk yard twin turbo on a bone stock 5.0 for about $800 putting you in the low 12's because you have traction problems

I can see now we will never see eye to eye on this, which is fine. You have a few assumptions stuck in your head that are not accurate. I don't know how to change that.

In your previous post you were saying you didn't want to include roots superchargers in the mix and in the very next post bring them back up (with the 5 mile sprint deal).

In all your examples you are assuming the turbo vehicle is set up optimum and the supercharged (roots or not doesn't matter) vehicle is mis matched.

If both vehicles are set up to take full advantage of the forced induction used, the difference will not be as clear cut as you would like to think. You would not use a roots supercharger for road racing, there are several reasons, vision, weight, center of gravity.

You assume that at X rpm your turbo will be spooled up, the same can be "arranged" for a supercharger, you fail to realize that. As Parisienne66 said and I have said many times in a different way "Everything is relative, and everything always has its wins and losses, on both sides."

You first said turbos were better, period. I showed how that theory was flawed and then you didn't to include roots superchargers, then you didn't want to include drag racing. If we elminate enough stuff at some point the turbo will be the only thing left.

You also make another assumption that is NOT correct, you really can't have supercharger that is too big, while RPM does have an effect, unlike a turbo it is not all RPM dependant. You can turn a larger blower slower and make more boost than turning a small one fast. It's all about moving air. A larger fan has the ability to move more air. If you take two fans with the same pitch blades one has 12" blades the other has 16" blades turn them both the same RPM and the larger fan will move more air. NOW it will take more power to turn the larger fan as an engine builder/tuner it is up to you to figure out the point that you get the most return.

It does NOT take 600HP to turn a 14-71 blower (used in top fuel) this is a big mis-conception. You can turn that blower with your hand and you are not producing 600hp. Therefore your Honda can spin it. To make the kind of boost, HP and RPM the TF cars make it uses about 600HP to make 7500-8000HP. Your Honda is not going to make that much power nor be able to use that much boost so it would not use 600HP to make the 300HP it would produce.

You are not going to convince me and I am sure I am not convincing you. I think you have a few things twisted, I do know the point you are trying to make, I just don't think you are making it correctly.

I will help you, if you take the "SAME" size turbo and centrif blower, all other things being equal, the turbo "should" be able to make more power up top. The blower will make more power down low, So which is better? Both cars have 2.73 gears, which one will be quicker and which will be faster? Are we drag racing or road racing? oval track or road course.

Do you see my point? The point is it all depends on what the goal is on which is better for that application.

I never at any point in this whole thread said one was better than the other. I only tried to point out the advantages and disadvatanges of each.

I can agree to disagree and let this thread go back to rest.

Royce

the real benefit of a turbo is shown in the diesel world, when the load increases the extemp climes the turbo speed increases and the boost rises to the occasion. when the truck, or car so equiped hit a hill and the air thins out the turbo speed increases giving the same boost at the top therby no power loss, sizing the turbo is very important. as far as drag raceing is concerned r system works but in general terms roots or any engine belt driven blower is rather dated. suitable for the flint stones. mind you i am from the diesel world where cat has used turbochargrs after coolers and wast gate systems since 1955 with great success. just another opinion. the article i thot was well put together. cliff

How long have they been using superchargers on diesels (roots at that). Since you are from the diesel world you should know they are still used on diesels today. I don't see many "fast" diesels, either.

Royce

It's not that there is no power loss. It's just that, without any changes a turbo is less prone to power loss with altitude gain. On the other hand, with the proper setup on a belt driven supercharger you can negate the power loss as well. You can change rotor or compressor speeds on a belt driven unit relatively easily to make up for the thinner air, which is goes along similar lines to the points Camaroman was making a few posts ago.

For Years I Have Watched This Debate With Interest And Of Course Technology Has Constantly Improved During This Time. It Is Interesting To Note That after All These Years All These Methods Continue To Exist. My Personal Preference Is The Supercharger. Remember All The Compressors Are Doing The Same Thing. Its How They Are MADE To Do It That Differs Most. It Is At This Point I Prefer The Supercharger. They Are Getting Ever More Efficient. But The Main Reason I Prefer The Supercharger Is That I Am Free To Engineer The Exhaust System For Greatest Efficiency By Doing Whatever It Takes. You Cannot Do This When You Are Running Exhaust Gasses Through A Turbine. I Can Then Concentrate On Extracting Maximum Efficiency From The Rest Of The Components Once Again By Doing Whatever It Takes. Indeed New And Improved Technology Will Make It Increasingly Easier For The SC's To Shine While The TC's Will Forever Be Plumbed Into The Exhaust. Belt And Gear Drives For The SC Are Reliable And Getting More So. Detonation A Problem? Shouldn't Be But Don't Forget H2O Injection. Oh, And By The Way, Don't Forget The Other 'Forced Induction'. THE JUICE!!!! MD

I don't function on assumptions. Assumptions are making decisions based on values that you don't know to be factual. When I discuss my opinion on matters I only speak with the basis of things I know to be factual. To keep things in perspective, I understand that you do no differently. Just a few thousand years ago it was common fact that the earth was flat. We now know that they were wrong, and similarly either one of us could be wrong. I may not be accurate, I do keep this in mind. But believe I have reason to think I am, such as you believe you have reason to think you are. I am not disrespecting you or the supercharger, I am disagreeing with you on the idea of one overall better power adder between the supercharger and the turbocharger.



Yes that is my position, I have seen nothing to support the contrary except in short distance sprint racing, to which I did concede, yes, the turbo in this application is inferior. I do not however believe this is enough to raise up superchargers to "overall equivalent" status with the turbocharger.



There is less disagreement here between us as it would first seem. I am sharing my opinion on the question "Which is better?". This is a specific question but encompases a broad range. A specific question in a narrow range would be "Which is better in 1/4 mile drag racing?". The answer to this I believe to be the roots blower, I am fairly confident that is your position aswell. However, with such a broad-ranged question at hand, I am keeping all applications of the reciprocating internal combustion engine in mind. Short distance sprint racing is a small piece of that pie. That is specifically why I don't believe focusing on drag racing applications is the path to the correct answer to this broad topic, and therefore as I stated before, I want to "Steer away" from that focus.

Why don't I think the continued discussion of roots superchargers is constructive to reaching the answer? Roots superchargers have their applications to which they are the king. But these applications are limited. The internal combustion engine is most efficient at high rpm, and for cruising. This is not where the roots blower shines. So in applications where the I.C.E. is most put to use, the characteristics of the roots blower makes it a poor choice in these applications. So it is clearly not the overall best. Therefore I think it prudent to "pass over" the roots blower as I stated before.



I am completely aware of the arrangements that can be made for a supercharger, are you considering the consequences of those arrangements?
In my examples I am not slighting the supercharger by mentally mismatching it. That would be absurd, especially when it comes to making a point. I am considering and factoring the power sapping nature of the supercharger (roots or not doesn't matter). Aswell as it's ridgid give-take nature due to it's direct drive design. What exactly is "optimum" set up? This must be asked in context of application.

This leaves cent. superchargers and turbos. Here the facts are clear, I scaled it down to make these facts easy to digest before. But I can just as easily lay out 'real world' examples since my scaled down examples are still trying to be taken literally and applied to the real world.
I am going to be nice to the supercharger here and pretend it has no rpm ceiling. The supercharger's rpm is directly related to the engine rpm. The CFM a supercharger moves is directly related to the supercharger's rpm. You can gear a supercharger to turn as many revloutions per 1 engine revolution as you want, and thus you can produce boost as quickly or as late in the engine's rpm band as you like. However, do to this rigid direct linkage you lose power no matter how you decide to set it up. Here are 3 real examples. Superchargers use both compressor and housing sizing as well as gearing to achieve the desired results.
1) If the supercharger is designed to produce the maximum boost That the engine will see from it at peak engine rpm, then we know that at low to mid engine rpm we are not going to see peak boost. We know this because the supercharger was specifically set up to produce maximum boost at top engine rpm. This method produces the highest peak power figures (if you do not know why right now, read on and you will), and is best used in high speed top gear applications where the peak power can be utilized for the longest possible period of time. 2) If the supercharger is set up to produce the maximum boost at low rpm, then we know that at mid to high rpm more boost potential is being generated by the supercharger, but is being diverted away from the engine. This power to turn the supercharger faster and faster beyond the point of peak boost is 100% lost. Horsepower is "thrown away" at the supercharger. If you want your supercharger to provide peak boost at an earlier rpm, for more power at that earlier rpm, you do it at the sacrifice of peak power at high rpm. This method produces the lowest peak power figures. This is best for low speed acceleration, or applications where high torque numbers are desired peak rpms are only seen briefly. Such as pulling and hauling. 3) If the supercharger is set up to provide maximum boost at a mid rpm, then you have a balance of the characteristics of examples 1 & 2. Power does not come on as quickly as example 2, however, peak power numbers do not suffer as much either. You sacrifice peak low rpm power, and peak high rpm power, for increased power access over a wider usable rpm range. This "medium" setup is the most common. Best suited to street cars.

That basically covers centrifugal supercharger setup options for all your different I.C.E. applications. If I've left a possible setup out, by all means post it up. Keep in mind I am pointing out specific uses where one setup will shine over the others. But we are probing the question, "which is better _overall_".

Using the same 3 examples I will swap out a turbocharger in place of the supercharger. 1) Highest peak power. Initially, characteristics of the turbo will be similar to that of the supercharger. Low rpms will see no response from the turbo, it is not untill the mid-ranges that the turbo begins to kick in. This effect is the famous "turbo lag". Note however, for a peak horsepower goal, this is no different than the supercharger. When the turbo does kick in the power comes on very quickly. It is not linear like the supercharger, it is more violent and sudden. Rather reminissant of nitrous. At peak rpm and boost the greater efficiency of the turbocharger will render a higher peak horsepower figure. 2) Low rpm power. Initially again, characteristics of the turbo will be similar to that of the supercharger. The turbo will begin to spool not far off idle and peak boost can be seen at a low rpm. Once peak power is reached and rpms and subsequently, exhaust volume contiues to increase, the waste gate begins to divert excess exhaust volume bypassing the turbo alltogether. The more rpms beyond the point of maximum boost the greater the percentage of exhaust is bypassed around the turbo. This means, unlike the supercharger, the turbo does not continue to spin faster beyond what is needed to maintain boost pressure. Horsepower is never "thrown away" at the turbo. I often refer to this as the thrifty nature of the turbo. Peak power is not as high as example #1, not because the smaller turbo is robbing horsepower and throwing it away at the atmosphere, but because sizing down the turbo to achieve low rpm boost means using a turbo that is not as efficient at moving large high rpm CFM as a larger later-spooling one would be. The greater efficiency of the turbo means low rpm horsepower figures will be greater than that of the comperable supercharger setup, and due to the "only take as much power as needed" style of a turbo, top rpm horsepower figures will also exceed that of the comperable supercharger setup. 3) The middle of the road turbo setup. This is where the turbocharger most noticably differs from the comperable supercharger setup. Here the boost does not come on immedately from a stop. But most setups will see maximum boost by 3000 engine rpms at the latest. Similar to the superchargers, because the turbo is not designed to come on asap, acceleration from a stop is less than that of example #2, and because the turbo is not sized for maximum efficiency at high rpm and high cfm, the peak power will not be as high as example #1. In this setup the maximum boost will be realized sooner than a comperable supercharger setup, so mid-low to mid horsepower figures will be higher than that of the comperable supercharger setup. Due to the thrifty nature of the turbo once maximum boost is reached, the turbo will never take more power from the engine without returning that to the engine in greater cfm. This means high rpm peak horsepower figures will also be greater than that of the comperable supercharger setup. Furthermore because this setup puts the turbo's efficiency sweet spot over a greater band of engine rpm, the fact that turbo has a greater efficiency than the supercharger is most relevant in this setup.

Something else that needs to be addressed about turbos. I keep reading about "comparing apples to apples". Reguarding percieved unfair comparisons.
Superchargers and turbochargers are similar in many ways, but in application of setup they are very different beasts.



This is not a complete or realistic comparison. I will help you. I can take the "same" size centrif blower and gear it like any one of the above 3 examples. All other things equal is not realistic. How are you going to "gear" a "same size" turbocharger to equal the gearing of the supercharger without changing size? Turbo systems are tuned using size to modify their behavior. If I want a turbo to come on sooner I do it by changing the size of something. This does not mean I'm turning an apple of a turbo into an orange. It simply means I am adjusting my turbo setup to behave in the same manner your supercharger setup does. The fact that the turbo will make more power is not because I am cheating somewhere. It is because the turbo is superior. The only all things equal possibilities are engine internals and atmospheric variables. When these are equal, I will always be able to make a turbo system outperform a cent. supercharger. Any way you like, low rpm, high rpm, up down, side to side, it doesn't matter.



I understand it does not take 600HP just to turn a 14-71. The notion of putting one on a Honda motor was just a comical image I had in my head of a blower that's too big for the motor. Yes I agree it takes more power to turn the larger fan. You can go with the smaller fan, but turning faster all takes more power. You can trade size for speed all you want, because they both take power. This is the game of thermodynamics. If you get more efficiency by going to a larger fan with less revolutions, that means you already hit the point of diminishing returns on the high rate of revolutions.
As the overall size of the supercharger increases the CFM it moves per revolution increases exponentially and so does the power required to turn it. Because the motor underneath of it is not changing, eventually the increased power requirements of the supercharger to maintain x boost will not be matched by power returned. Again, this is the game of thermodynamics. So yes, you can have a supercharger that is too big. This is not an assumption.

I do not feel there is anything wrong with me saying one is better than the other. I feel it is simply a truth simply not as widely recognized, as say, the more commonly recognized truth; car is better than the horse & buggy. It is inferior when it comes to the environment, or for romantic tours through beautiful parks and gardens, but overall, the car is better.
Similarly, so is the turbo.

Forgive me if I'm not one to agree to disagree. I will agree that we disagree. And I am always peaceful about it. But there is so much opportunity to learn something out of disagreement, especially when the one you disagree with is civil as you have been.

Take care,
~S

As you stated I think we are more in agreement than either of us know. I think our stumbling block is the whole "better" thing. Both have situations where they shine or are "better". The way the vehicle is set-up to do whatever it is intended to do (drag race, top speed, road race), has more to do with it than how the power is made.

How do we agree on what is better when we don't even know the goal? I will never agree anything is "better" or "best" without knowing all that is involved.

The question is too broad to say one is better and refuse to think otherwise.

I have no problem discussing this for days on end and I don't feel you have been disrespectful in any way. I too have tried to be respectful.

This is the exact reason there are rules for every type and form of racing. You have to have a way to keep things "fair". In certain instances a turbo would be the only way to go, in others nitrous is better and in others a supercharger would be a better choice. This alone means neither one is the "best" or "better". You have to lay out a circumstance for each and then you can say X is better than Y in that instance. The problem is X is not always "better" than Y. Are we talking fuel economy? Are we talking an injected turbo engine vs. a carb'd blown engine? There are just too many possibilities to say one is 'best".

You can talk until you are blue in the face and I will never agree that one is surperior accross the board.

You assume I am "defending" the supercharger, that is not the case I try to see all facts. I just saw a few mis-conceptions stated earlier and wanted to be sure both sides were heard.

Does "better" or "Best" mean which one is most efficient? If we are talking efficientcy then yes a turbo is "typically" more efficient.

What is the best? Who decides? How do you prove it? Typically we race to see which car is faster/quicker.

When talking about drag racing (the most popular form of racing in America as far as public participation), the turbo cars usually MPH really well for their E.T. Why is that? It is because they make a lot of HP up top, but not great torque down low. So in this case a supercharger is more "efficient" at getting the job done.

If we are talking about on the street or cruising. I will take my supercharger (yes even a roots) over a turbo any day. You don't drive around on the street with the engine RPM's through the roof. I can have gobs of fun and never spin the engine over 4000RPM.

Now if you were asking me to build an all out top speed car, I would definetly look at turbos to get my boost.

If we are talking looks, I will take a supercharger hands down. Turbos are ugly/crude (in most cases) and require a bunch of plumbing (read heat). They can be a hassle to package. Turbos can also be VERY challenging to run in a carb'd set up. So in these cases I would say a supercharger is "Better" or "Best".

Do you see where I am going here?

Which is better or best for a carb'd engine/car? What if the class you run says no injection? Once again there's the pro's and cons. You just can't say one is "Best" because there are far too many variables.

It was never my point ot say a supercharger was better, I was never arguing that point. I just will not believe a turbo is "always" better. My whole point was to prove NEITHER was "best" or "better".

If we have two engines with the same cubic inches (lets say 350), both make the same HP, same peak torque (just at different RPM's) one is turbo and the other is Supercharged, Which one is better? Why? What will these engines be used for?

Royce

tell me what diesel engine that uses a supper charger, no modern engine builder in the diesel world, 2cycle Detroit's where the last in north American, and they would not run with out a roots blower to at least get them up and running, plus at the end of there struggle they used turbos to supplement the roots. some of us look to toatle performance not just fast for a few seconds, i think and hope there is room for us all on this site

Cliff plenty of room for everyone here. I think you are taking things out of context. Did you even read my last post?

I am no diesel mechanic, this is a hot rod site. I don;t know of any diesel hot rods, if I am wrong excuse my ignorance.

Are you saying there are no trucks on the road that still have roots, superchargers? "jimmys". I have never personally researched this, but I did discuss this with a well known blower builder. I was told they are still in use today. Was he wrong?

Read my previous post before you reply please.

Thanks,
Royce

You can still buy repair parts for Detroit two strokes, they may still be available for off-highway and industrial use as well but Im not sure about that.

As for hot rod diesels. Banks built a diesel powered Dakota that broke the land speed record for pickups (including gas powered), I think it had a 5.9 Cummins. The truck went something like 225 mph thanks to 700hp and 1200 lb ft of torque. They called it the "Sidewinder" Dakota.

yes i did, what iwas trying to say was ther ar no current engines built to day for highway or industrial use that use supperchargers belt or gear driven.99% are turbocharged . ther are still a few 71 and92 series detroits on the road, the8v92s had bothe roots and turboes,but thes are older units and hard on fuel.as far as diesel hot rods ther are lots. ford and dodge trucks with diesels hoped up to huge hp and torq nos.remember a turbo is driven by extemp as well as velosity so you get boost when you increas the fuel and ex temp rises. also as vehicl clime in altitud the turbo speeds up as air gets thinner, ther by no power loss and no loss in manifold pressur.(a dodge with a cummims would be rated from o to7000 ft altitude with no loss of hp. cliff

ever here of turbo lag , try feeding 1 gal of fuel to a motor running 3000 rpm, like drowning your pet dog , hp in fuelers is made by burning fuel , you cant get the air out of a turbo till higher rpm when the rotor starts spinng so you figure it out , how!

not every one gets excited with drag racing hpower for 3seconds does nothing for me but what ever turns you on great.

I've heard of turbo lag yes. I've also heard of flat head fords. Both are known as a thing of the past. Technology has taken turbocharging well beyond what it used to be, just as it has taken engines well beyond where they used to be.
My turbocharged v8 reaches maximum manifold pressure of 11psi at or near 2,300 rpms. If I wanted to, I could do some changes and have them come on earlier, but power that early simply isn't usable by me because my car is not designed with drag racing in mind, and so my holeshot traction isn't maximized.

I completely agree with you that feeding copious amounts of fuel to a motor turning only 3,000 rpms (assuming this isn't a freakishly large engine) is not a good thing because there isn't enough air to necessitate all that fuel. However, I also suggest poking around and learning a little bit more about fuel management. There are several different methods, mechanical and electronic, but they all basically perform the same function. That is to deliver an amount of fuel that is relative to the amount of air coming into the motor. If my turbos have not "spooled up" by 3000 rpms, that means they aren't pushing alot of extra air into the engine. That means whatever fuel management system I use isn't going to add the gallon of fuel that you are talking about. So the scenario you pose for turbos that havn't spooled up yet isn't applicable, because it's not going to happen. If it does, it is the problem of the fuel management, not an inherent problem with turbochargers.