Super vs. Turbochargers....A brief discussion

[SeanM]

Welcome ladies and gents, to the place to seek input on Superchargers and Turbochargers, as well as the pluses and minuses of each. I myself am largely interested in Supercharging my Explorer, but seeing as I have a long time to save the money to do so, I am beginning my research. Here are the beginning questions for this thread, which I would love to hear some technical/mechanincal(yet well explained) input on...

1. What is the definition, both mechanically and technically of a Supercharger?
2. What is the definition, both mechanically and technically of a Turbocharger?
3. Are there different types of Superchargers?
4. Are there different types of Turbochargers?
5. Explain the dynamics behind Superchargers.
6. Explain the dynamics behind Turbochargers.
7. What is "turbo lag"?
8. Can that "turbo lag" be eliminated?
9. Pluses/minuses in a comparison chart, perhaps, of Superchargers and Turbochargers.

Basically, I am attempting to pool all of the knowledge that each of you out there has so that there can be ONE thread where everything about these massive engine modifications can be referenced. I would like everyone to post a question so that some of the true gearheads out there feel almost obligated to answer. Don't be stingy with your knowledge of this topic . And now....Let the input flow like the salmon of Capistrano .

Sean
_________________________________
'95 XLT 4dr 4.0L V6 OHV Auto
Flowmaster 40 series Cat-back
K&N FIPK
Bosch 4+ Platinum plugs
Splitfire ignition wires
PIAA 9007 Super-White Headlights(adds 40 rearwheel hp )

 

[Nick Schmitt]

I have limited knowledge about this subject, but i will give you what i know, and anyone can correct me if i am wrong. Technically super and turbo chargers do the same thing, they compress air before it goes into the engine, but how they do so is the difference. Superchargers, are connected to the pulleys on the front of the engine, therefore in order to turn the supercharger it takes horsepower. In essence it takes power to make power. The turbine in the trubocharger is turned by the exhasut gases. Therefore it does not tkae any power to make the power. Turbo lag comes into play with only turbochargers. Basically turbo lag, is the amount of time that it takes for the exahaust to start to turn the turbine. Turbo lag as far as i know cannot be eliminated. I believe that know one makes a trubo for the explorer, most turbos are made for small asian cars. The different types of super and turbochargers, basically stems from their sizes. I believe that smaller turbines make more power lower in the RPM band, while larger turbines make more power in the upper part of the RPM band. Then there are twin turbines that make power through out the RPM band. Advantages of the super, is that it does not experience turbo lag, but you lose a little power to make the power. Advantages of the turbo, is that it does not take power to make power but it does expereience lag. i hope this helps, anyone feel free to let me know where i may be wrong.
Nick

 

[Alec]

Nick, I think all that you said is correct. Sean, if you want info pertaining to our Explorers, here it goes:
There is no turbo made for the Explorer. Cameron is trying to custom make a turbo setup in his, but it's costing $$$$$ and taking a lot of time. Turbos are usually harder to install because you have to plumb into the exhaust and run all sorts of pipes and stuff. BBK makes a great bolt on supercharger for the V6 OHV. In fact, I ordered one this weekend. Woohoo! From what I hear, its a super easy install. You take the intake manifold off, put the supercharger on, and connect all the belts and hoses. There are different types of superchargers. The BBK is an Eaton-Roots type which I think uses vacuum pressure and stuff to make the intake charge. Some people custom fit Vortech's onto their OHV's with varying success. Apparently, its a plumbing nightmare, and Vortech is a crappy company. The Vortech is a centrifugal supercharger. Hands down, an Eaton-Roots blower is better. I can't wait for mine! So, save up $3k and get the BBK! Oh, the BBK makes power throughout the RPM band (unlike a turbo or the Vortech), and has a constant boost around 6 lbs.

 

[tac0meat]

well i have to respectfully disagree with nick on the part about turbo lag not being able to be eliminated. your both right and wrong, nick. true, turbo lag will always be there to some degree, but it can easily be reduced to a point to where it is virtually unoticable. depending on how the wastegate is set, size of the turbine and compressor housing and blades and size and rpm of engine will ultimately determine the amount of turbo lag. a turbo sized for low to mid rpm on a 4.0 ohv(this is engine does not do so well at high rpm so lets concentrate on rpm below about 4500) can "spool up" very quickly if the wastegate is set so not to let much exhaust gas pass by the turbine blades. the less gas that is allowed to pass around the turbine will decrease turbo lag to a point to where you would probably never notice.

 

[blk mk8]

supercharger

the eaton is a very limited blower. the vortech will fit fine. the blower kit from the 4.0 has the same motor and engine compartment. you would have the same problem with either of them. troll has a vortech and it work very well. quadcam has had vortech and prochargers just ask him what he thinks of them. the eaton would be great for a stock truck with no plans of going very fast in the long run. they are best as oem factory blowers. a motor like trolls or cammrons would suck that little thing dry. i will post numbers soon about before and after with a vortech on a 4.o. can any of you find rear wheel before and afters of the eaton. try a paxton kit on a explorer before you use a eaton. 5.4 lighting with the eaton are all blower restricted.

 

[Cameron]

1. What is the definition, both mechanically and technically of a Supercharger?
2. What is the definition, both mechanically and technically of a Turbocharger?
3. Are there different types of Superchargers?
4. Are there different types of Turbochargers?
5. Explain the dynamics behind Superchargers.
6. Explain the dynamics behind Turbochargers.
7. What is "turbo lag"?
8. Can that "turbo lag" be eliminated?
9. Pluses/minuses in a comparison chart, perhaps, of Superchargers and Turbochargers.


1 and 2: Superchargers and turbochargers are fundamentally the same in that they are both air pumps. That is, their sole job is to compress air prior to its introduction into the combustion chamber. Superchargers are driven by a pulley that is driven by a belt attached to the crank pulley. A turbocharger is driven by exhaust gasses passing a "fan" that is connected to a shaft that turns an impeller that compresses the air.

3 and 4: Yes, there are many different "off the shelf" superchargers and turbochargers. Furthermore, you can custom make a turbo by specifying the turbine housing size, compressor wheel size, whether or not it is water or oil cooled, how many bearings it has etc...

5 and 6: That would require many many pages of technical data and drawings.

7: Turbo lag is essentially the time it takes a turbo to "spool up" and start providing boost.

8: Technically no. But it can be reduced so much that you probably wouldn't notice. Smaller turbos offer less lag but peak out at lower RPMs. Large turbos have longer lag times but offer high end power. That is the benefit of sequential turbochargers such as the ones found in RX7s. A sequential turbocharger is two turbos in one. The first turbo is small and has a very short spool up time offering fast response and low RPM torque. As soon as the motor reaches a set RPM level the small turbos bypass valve opens allowing all gasses to pass freely to the big turbo that gives the motor high RPM power.

9: There are many arguments for and against each of the forced induction methods. Some info that may help you decide:

PRO:
A properly optimized turbo has the potential to produce more horsepower within given limits of detonation, primarily due to lower parasitic losses.
All things being equal, proper intercooling will allow you to run more boost and produce more power. While both turbos and superchargers can be successfully intercooled, most turbo kits are designed around intercoolers, most supercharger kits are not. Although "Roots" type blowers (the kind that sits on top of the intake manifold) can not be intercooled without huge expense.
A turbocharger has a flatter boost curve than a centrifugal supercharger making it perhaps more usable for city driving (a positive displacement blower has the flattest boost curve of all).
Boost is more easily set on a turbo via the wastegate. With proper controls it can be changed from the dashboard. Superchargers require a pulley swap to change boost levels.
Turbochargers do not place an additional load on the front of the crankshaft which can lead to uneven wear
CON:
A turbocharger install is, without a doubt, more involved and time consuming than a supercharger install.
Under hood temps are higher but generally not a problem. High temperature coatings on the exhaust manifolds will greatly reduce under hood temps but at an additional cost.
In order to minimize the chances of cooking, it’s generally a good idea to let a turbo spin down before turning off the engine.
Contrary to popular misconception, turbo kits are more or less on par with superchargers from a price standpoint when you factor in the additional components. Most notably the intercooler. However, this does require a higher outlay of cash up front. This rule goes out the window when you try and turbocharge an Explorer because there are no kits available and everything is custom.

 

[RFR2212]

Cameron--What's the status of your custom turbo install?
Pete

 

[Cameron]

The wheels of progress move slowly.

I'm actually waiting for my brother to get his VW fixed. He will lend me his car while my truck is in the shop. It will save me the cost of renting a car while mine is being worked on. Just more money to put into the motor.

I have a guy using an exhaust manifold gasket building a custom flange that a custom exhaust manifold will be built on. If you're looking at the engine from the front, the turbo will be on the right hand side level with the throttle body.

I have the turbo, intercooler, blow off valve, wastgate and the plumbing will be custom made on site. I'm still trying to find a timing controller. I'm waiting on a reply from MSD. They look like the most likely candidate. For now I'll rely on a manual boost controller but will change to a programmable one when I install the Venom system installed. I recently purchased Rick's old aluminum intake manifold to replace my stock "plastic" manifold. We don't think the plastic manifold can take more then a couple of pounds of boost.

I'm so impatient to get this project started. Believe me, when this project starts I will post plenty of step by step pictures on my web site. I hope to start within two weeks.

The wait is driving me nuts!

 

[Chav]

ExplorerDaddy why do say that eaton roots type blowers are limited? and what do you mean. I am confused because I thought the roots or screw type blowers were the better choice and I've seen em on drag cars. I thought the centrifical blowers werent as beneficial because they dont produce much compression until the rpms are up.

-Chav

 

[Cameron]

Two basic superchargers exist today on the market. The first, and most common, is the "roots" type which is two spinning rotors that pump air into the cylinder. This is the classic "hot rod" style of blower that sits on top of the engine. The other style is an internal compression supercharger. In this type of supercharger, the pressure is built up within the supercharger housing, not in the intake manifold. Both types share the same boost principal, the only difference is in how the boost is delivered to the cylinder.

The roots type is almost exclusively used in carbureted motors. Although, Nissan, Mercedes and several other auto manufactures including Ford, have used and are using roots type superchargers on EFI motors the boost is reletivly low. The centrifugal type superchargers are almost exclusively used in EFI motors but I have seen carbureted motors with centrifugal blowers.

The problem with roots type blowers is that it is very difficult to intercool the charged air. Top fuel dragsters need not worry about this because the fuel they use (namely methane) is such a high "octane" that they need not worry about detonation. Or at least that's what I have been told.

 

[Alec]

So is anyone trying to say it's a bad idea to get the BBK 4.0 supercharger? I hope not...

 

[blk mk8]

blower

they are only better on race cars where you can bolt a blower on the motor that is just as big a 4.0 explorer motor. the bigest street eaton can only make as much power as a meadium size vortech. you need one of the holley or weidend race blower to beat the paxtons and vortechs. the best thing about the bbk(eaton) is it is great for stock cars but not good for any thing more then that and it is maxed out. the other blower's dont make as much power down low but make twice that on the top end. most paxtons and vortech make enough down low that it would not be a problem. a stock 4.0 can handle 13 pounds of boost on the street with a vortech but you will never be able to see that kind of power with the bbk that is why i used a vortech on the 4.0 we are working on.

troll's motor make so much torque down low that even with out the blower on it still spins the tires out the hole.every one has a difrent opinion so if you like the bbk better then the vortech then oh well. i can tell you this i can make the same car with a vortech go faster thought for no more cost then a new pulley. the cost of a vortech s-trim kit for a 4.0 retails for more than the bbk but any vortech destibutor can get it for a little over 2 grand. cameron you should get a haltech engine management for $1300. you can reprogram the whole fuel and timing curve in combintaion with a dis-4 ignition system and this will all work with you coil packs.this is your best bet so you dont have any timing problem or fuel prolems or have to mess with those dam chips.

 

[markhas]

Eaton M90

The roots type blowers can make good HP... say 400-500HP on a heavily moded V6. I have a 430HP supercharged 3.8 in my T'Bird SC. The engine is heavily modified to make this HP, and the engine can outflow the Eaton M90 blower which maxes at 15+ lbs of boost. You can turn it faster, but it becomes less efficient and eventually the bearings will go out. At these boost levels you need a good intercooler (air-to-air). It is true that the Eaton would be a limitation to max HP. However it all depends on how much HP/Torque you really need. The BBK uses a different blower M117 which is also used in the Lightning. This is a high output efficient blower intended for lower boost applications. It can't handle being run much faster than the stock 6-7lbs. I was originally going to put a spare SC engine in an older Explorer, but decided to buy a '98 with the SOHC engine. I might some day put a blower on it with parts from the SC engine... the computer will be a big problem though.

Engine:
http://www.sccoa.com/member/images/hasenyager4.jpg

Dyno Run:
Dead Link Removed

[Edited by markhas on 11-28-2000 at 04:59 PM]

 

[Chav]

What you said makes sense. Thank you for explaining it.

-Chav

 

[QuadCam]

one other piece of supercharger info

turbos, centrifugal superchargers, and roots-type blowers all "make boost" by forcing the air into the engine. The "boost" is built up in the intake manifold. The only supercharger that I know of that compresses the air within the housing of the supercharger is the lysholm-screw type. These are commonly know as whipplechargers. these superchargers uses interlocking screw-type vanes that squeeze the air together between the screws. as the air moves down the screws, the air is compressed tighter and tighter. then, at the end of the screws, the air is pushed into the engine.

of all of the options, I prefer the centrifugal superchargers. they are the easiest to tune and the most streetable ( in my opinion). the centrifugals also have the best adiabatic efficiency (over roots and turbos). most of the time, tremendous HP levels can be generated without the need for an intercooler.

do plenty of research, and try to get a ride in some vehicles with different power adders. Also, Vortech is a very reputable company, contrary to what someone said in an above post.

finally, there is always "liquid supercharging".....NITROUS!

 

[markhas]

High Power V6's

The roots blowers are great for making lots of torque at low RPM's ... which means they are better for off road use. If maximum HP at maximum RPM is what you are after, then this is not the blower for you. I personally like the Ford OHV 3.8 V6 used in the Thunderbird SC from '89 to '95 for obvious reasons. The engine is very similar to the base 3.8 and the stroked OHV 4.0 in the Explorer. In fact there are some SCCoA members that have stroked 4.0 SC engines. If I were to look for more power with a V6 Explorer, I would try and find one of these engines. For the same money as a BBK kit you could probably buy one from a junk yard and rebuild it. There are various places that have high performance parts for V6's ranging from SuperCoupes, Pontiacs to Buick GN's.

T'Bird Clubs:
http://www.sccoa.com/
http://www.tccoa.com/

Eaton Blowers:
http://www.magnusonproducts.com/

High Power Blown V6's engines
http://www.coymiller.com/

 

[RFR2212]

So, through all this mumbo jumbo that I somewhat understand, which style supercharger produces the best low end boost over stock, seeing as that is the goal for off roaders wanting low end power and torque
Thanks
Pete

 

[QuadCam]

rfr2212,

I am not an off-roader, but I would asume that you are looking for "stump-pulling" torque off idle. am I right?
I guess off-roaders look for that kind of torque for slow rock crawling and the like.

Like I said, I have no experience rock crawling, but I'm pretty sure that you are not doing that with the throttle wide open. none of the blowers or turbos are gonna give you that light-throttle torquiness. the roots-type may give you some of that feeling, but all of them are designed to give you boost at WOT. for the engine to "make boost", there needs to be a load on the engine. try revving a supercharged or turbocharged engine while in neutral; they don't make very much boost.

I think a stroker motor (added displacement) and/or more gear multiplication will help you out the most.

an example is the old Willy's Jeep. they only had 4 cylinder engines in them, but they had alot of gear (especially when 4wd-low is engaged). Those old willy's could practically drive up a wall.

 

[Cameron]

But when you're off-roading you would have your truck in 4X4 low. So the RPMs would be high, the load on the motor would also be high and the turbo/supercharger should benefit. I could be wrong here because I haven't finished my truck yet. But I would think that whenever there is a need for torque, a supercharger or turbo would benefit you. You just need to set it up for your particular application. If your building an off road beast, put a small turbo on it. Spools up fast and gives most of its power on the lower RPMs. If you're building a Salt Flats runner, put in a big turbo and sacrifice acceleration for high speeds. If you're building a street car, put in a medium sized turbo (assuming you don't want to hassle with a sequential turbo setup) and you'll get good all around performance.

But I definitely agree that gearing would be the most cost-effective way to improve rock crawling. Put in one of those Atlas 2 transfer cases and some 4:11 and your cooking. I think Rick has no problems rock crawling and he is running naturally aspirated.

Anybody have a supercharged truck they use for off-roading? Tell us your observations.

Anyways, just my 2 cents.

 

[Cameron]

And I used to drive a Jeep when i was in the Army (before the Hummer) and QuadCam is right. You could pull a tree out of the ground with that little 4 banger. It had the lowest gears. Unless we were towing something you would always start in second gear. I would love to have one of them now.