TURBOCHARGE or SUPERCHARGED - The $64 Question

[twin turbo]

AL427SBF, if you go to theturboforums.com you can find the answer to almost any question by using the search button and looking thru the various forums there.

I love my twin turbo sbf and wouldn't ever consider going back to normally aspirated. The great thing about turbos is you can adjust the power setting, adjust how fast you want the boost to come on, and get great gas mileage and driveability.

I find it interesting that the two posters in this thread that said their cars are hard to handle and not as fun with a lot of power were both supercharged. Cheers.

[AL427SBF]

I'll check those forums out. Agree, seems some of these "advise givers" are not so much interested in answering the question turbo vs supercharger - and more interested in sharing their problems do to poor choices for their motor/driving preferences lol.

[Jerry Clayton]

OK--try this on for size---The Cobra has a lot of room in front of the engine for mounting a super charger---As for turbos---you will probably lose the side exhaust, you are going to add a lot of heat to the under hood area of a vehicle that is severely heat challanged--you will be dragging around a lot of crap that will only become effective way above the range that you can drive on the street, and nowhere will you find an organization with rules/specs for what your doing--

If you want turbos, put a 4 cylinder in it with a system that will give you a pathway to increase and upgrade the power level as you gain ability(tuning the complete car as well as driving ability) and always wear a full driving suit and helmut, gloves,boots,etc, along with a full cage_____

[zrayr]

supercharging has several advantages over turbo set-ups. It costs less, is easier to install, and the systems last longer without major overhauls. The power cost of supercharging is greatly overblown (pun intended). Even vintage Paxton superchargers on a basic 289 are making 120+ HP and costing less than 20 for a net gain of over 100+ HP. The modern roots type are dramatically more efficient than that.

Z.

[olddog]

Originally Posted by AL427SBF

I'll check those forums out. Agree, seems some of these "advise givers" are not so much interested in answering the question turbo vs supercharger - and more interested in sharing their problems do to poor choices for their motor/driving preferences lol.

Only a small percent of Cobra's have forced induction, so its no surprise a lot of folks here say you don't need it.

On the other hand your question is too broad and undefined. It's like asking "gasoline engine verses diesel engine, which is better?" How can anyone answer this? Are we talking 2 stroke or 4 strokes? Weed eaters, boats, cars, planes, or 18 wheeler?

There are so called positive displacement forced induction. Roots (lobed type) blowers, scroll, and screw compressors would be in this category. The lobed blowers are less positive than a screw compressor, especially as the pressure goes higher.

Centrifugal blowers are not positive displacement. A turbo is in this category.

With a centrifugal blower, the pressure it can generate is a function of the tip speed of the wheel. So on a belt driven centrifugal blower, the boost at low rpm is near zero. The boost and therefore the torque at the flywheel increases as the rpm increases. This results in an engine that has no balls until it revs up.

On the other hand, a positive displacement blower can give 100% boost from idle to maximum rpm. This results in an engine that has massive torque from off idle to red-line.

The Turbo wheel speed is not connected to the crank and is driven by exhaust gasses. At WOT low rpm the turbo wheel will speed up and make more boost than its belt driven counterpart. A turbo is not positive displacement and will not make the low rpm torque, however it can spin up and make maximum boost well before the red-line, which is an improvement over its belt driven cousin. Then it dumps exhaust out a waste gate to control the boost to its maximum as rpm climb.

So on the surface the turbo splits the differences between centrifugal and positive displacement. However since nothing is free it does so at a cost - lag time. Turbo lag is well known. It takes time for the turbo wheel to build up speed and make boost. Turbo proponents will tell you turbo lag is a thing of the past. Although it has been greatly reduced, it is still there, and it always will be. They will tell you that there are tricks to stage a turbo car at a drag strip to eliminate the lag. This is the proof that the turbo lag is still there. The lag is not eliminated in their staging technique. It is compensated for, by it, but rest assured it is still there.

[olddog]

It is often stated that the turbo is free power, since it doesn't have a belt robbing power from the crankshaft. This is not totally true. The turbo is a restriction in the exhaust pipe. It increases exhaust pressure on the engine. This increased pressure is pushing on the piston on the exhaust stroke. This is robbing power from the crankshaft. Some sources say boost pressure to exhaust pressure is close to 1:1. I do not know if this is always true.

On the other hand, the turbo does take advantage of the high cylinder pressure that is blown down, when the exhaust valve is opened early (before the end of the power stroke). Some of the power that drives the turbo would have been wasted, so some of it is free power, but not all.

When compared to a belt driven blower making exactly the same boost pressure on the same engine. the turbo will make more power. However because the turbo increases exhaust pressure, valve timing can be tuned to get a bit more power. So the best cam choice for a turbo verses a blower is a bit different. At mild boost pressure this can be ignored, but the higher the boost pressure the more important the cam choice becomes.

[AL427SBF]

I've googled turbocharge vs supercharge, several in depth articles by performance engine builders who have experience with both. It's pretty unanimous across the board which is the better solution, and not really a close comparison when you weigh in all the factors. Many myths surrounding both also dispelled:
- Under hood heat
- Amount of mods to the existing motor configuration
- Net performance gains & when in the power band
- Steetability, wear & tear on the motor
- Cost in a true 'bang for the buck' assessment
- etc. etc. etc.
Really good reading, I recommend some of you here maybe do the same. Oh, there are some here (well one for sure) that already know the results of such an in-depth trade study, turbocharging is the far superior solution to boosting performance over supercharging. It's really no contest at all.

[olddog]

Originally Posted by AL427SBF

turbocharging is the far superior solution to boosting performance over supercharging. It's really no contest at all.

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

Why has the big three sold both turbo and blowers in recent times?

[DougD]

I'll say it again. Roots blower. Simple. The boost's all in at low rpm, makes the torque you need. No need to wind it up like a 4-cyl.

But either is a poor substitute for a normally-aspirated engine built to do the job. We are talking a street car, right?

In my opinion, of course.

[AL427SBF]

olddog, didn't say "... an absolute fact in all circumstances", far from it - but you don't run top fuel on the street, we're talking a car that you can enjoy on the weekends and register with the DMV. I would still go torbo if I were building the motor from scratch, but I've changed my mind with an already built engine. Easier to jump to a supercharger, but I would go with a twin screw from Kenne Bell or Whipple, more efficient than a roots. I'm betting my "normally-aspirated engine" is built to do the job and I won't need to do anything.

[undy]

How about a little NOS??

It's by far the simplist and cheapest way to get HP. The really great thing... If you don't like the power all you have to do is take it off. You also can keep your 10 or 11 to 1 compression, unlike a proper designed supercharged or turbo system. I'm thinking of a 100% hidden 300hp progressive fogger system in my 482" aluminum sideoiler for a winter project. the whole system will run me about a grand and I can adjust the power to come on a any rate and go (up to 300HP) as high as I can safely handle.


Oh, btw... drag radials will become pretty much a requirement.

[AL427SBF]

NOS is probably the cheapest but who wants the headache of bottle maintenance and that nickel & dime overhead, I don't.

[undy]

Cobras = maintenance, an age old formula... I'll take nickle and dime over $5K and $20K overhead any day of the week. The nice thing about NOS, unlike superchargers or turbos, it won't suprise you unless you want it to.

A bottle fill is around 20 bucks and you can kill yourself at least 20 times with it. Now that's a bargain!!!

[twin turbo]

Undy, have you ran nitrous before? It only costs $20 to fill a bottle? You can make 20 runs with this $20 bottle fill? It won't surprise you unless you want it to, really? As someone who has spent thousands on bottle fills and the problems and hassles with them, I could not disagree with your statements more.

[lovehamr]

Originally Posted by AL427SBF

but I would go with a twin screw from Kenne Bell or Whipple, more efficient than a roots.

If it's a twin screw it is a Roots style blower regardless of the marketing hype. I had one on our last Toyota Tacoma and am about to put one on our new one. From a simplicity and bang for the buck point of view I don't think that it can be beat.

[CHANMADD]

If you read the other thread here about toppled it appears that very few guys have the nuts to go much over 100 mph, so what's the point of having enough power to go 300mph. Also if you start making stupid horsepower other driveline components start failing with dire consequences.

[CHANMADD]

If you read the other thread here about top speed it appears that very few guys have the nuts to go much over 100 mph, so what's the point of having enough power to go 300mph. Also if you start making stupid horsepower other driveline components start failing with dire consequences.

[AL427SBF]

Originally Posted by lovehamr

If it's a twin screw it is a Roots style blower regardless of the marketing hype. I had one on our last Toyota Tacoma and am about to put one on our new one. From a simplicity and bang for the buck point of view I don't think that it can be beat.

Agree, I think you can consider a twin screw a perfected roots system.

[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.

[AL427SBF]

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.

http://www.kennebell.net/techinfo/ge...romcatalog.pdf