Hey all, had used the search, but didn't come up with any clear answers, but i have been looking into superchargers over the net, trying to work out why many people around don't talk about them much and seem to go turbo.

But its confusing. On one web site, it was stating the humble supercharger gives boost all the way through the revs, while turbo only gives boost mainly in the high revs (cause of the high flow of exhaust created by teh faster more rev engine).

Yet, some say that turbo is better, because having the supercharger connected to the engine slows down the engine as the engine needs to turn the superchargers turbine connected to the belts. Others also say turbo puts pressure on the exhaust as it acts as an obstacle slowing down the exhaust from exiting the engine as it has to get around it.

So from all these ups and downs, i'm lost in wonder of really, what the hell would be the best to use. I was thinking supercharger, but then turbo, back to supercharger and now and huh? wtf? which one? Lol

So from all u guys experience, or whoeva else has questions on it, or comments/recommendations/ideas or arguments/inputs into this topic/debate or wateva u wanna call it, please by all means, do. Thanx all.:thumb

There's different types of SC's and different types of turbos. Depends on your needs as to what setup you should get.
The original style SC's (I think called hurst?) that look like a factory sticking out of your V8's bonnet provide boost (sucking extra fuel) all the way through the revs. I think the new screw types have the same effect but are more efficient (more boost vs engine load).
Turbos do have a progressive boost, but you can choose the turbo to suit your rev application. They can be good for daily drivers, putting around and you get very little boost, but let it rev and get your power! You could probably find a small turbo which would give you lower rev boost.
There are also centrifugal SC's which are still engine driven but behave more like turbo's, and seem to offer best of both worlds.
It all depends on what the car is for.
Unless I'm still living in the past, you wont see top fuel dragsters running turbos, doing the shopping or paying there own fuel bill


anyone else, please correct if I'm wrong or obsolete

I would agree with Edmond.
For street use and for racing.
There are always exceptions and applications that will be more
suited to one or other.
For all out dragracing, I have found the superchargers that
I used, were more forgiving to driver error, like taking
off at low revs or short shifting, than would a
same boost turbo be.
BUT! Boost for boost the turbo will make more power provided the intake temps are controlled.

How LONG is a piece of string

The type that a lot of V8's use is called a Roots style supercharger. They kind of work like a gear oil pump (like on the VW) except they pump air. Then there are twin screw/lysholm superchargers which are much more efficient than a roots style, they use these on some high end mercs, the Mazda Eunos 800M. Whatever people tell you,superchargers and turbochargers both take energy from the engine - it takes a fair bit to compress air.

Anyway I could go into more detail but I would just be parroting. BTW Google is your FRIEND
http://www.coloradocobras.com/whipple/superchargers/forced-induction.html
http://auto.howstuffworks.com/turbo.htm

what would u guys think would be more wise for a performance vee dub on the track, that would come road worthy? say a 2L genuine type 4. (the aircooled ones supposably from the caravelles, cause im still trying to understand which model their exactly from, but from what i have heard from people like xtc, well yeah.)

Adding a little more, what year caravelles range to before they hit any sense of watercooling? if anyone knows. if anyones got links about em' and where they're from, that'll be awesome.

I have got a fair idea of how each works, but telling whats best for the huge mix of ups and downs is so complicated. btw, that how stuff works web site is champ, been using since yr 8 for everything. Great read too. Was reading something about the theory of intellegent design, ANYWAYS... on the track again, thanx all for ur contributions to this talk, its great getting opinions from the pros. Keep em rolling

string? Lol

A properly configured turbo system shouldnt have any problems being off boost at the strip but it aslo comes down to how the car is setup. A big turbo is going to need a lot of revs off the line if you want to leave on boost. If your 60ft time is your main concern a supercharged setup may be the go.

Pro Mod turbo cars cant 60ft as good as the blown and Nitrous Cars (yet) but they top end stronger, thats a pretty good example of the differences i think.

BTW top fuelers aren't allowed to use anything other than a 14/71 standard helix blower, I think turbo's and Nitro would be ideal companions. Plenty of wasted heat in the exhaust!

better for what? where you need more low down torque then displacement supercharging such as the rootes blower is the go. centrifugal superchargers operate in a similar fashion to a turbo so don't make any significant boost in the first 1/3 of the rev range, but are a whole lot easier to plumb in than a turbo. A turbo is also an efficiency device so when not on boost you can often gain better fuel economy, but as stated they come into their own high in the rev range (depending on application).

everything is a compromise, so it comes down to where and how you need to use the motor.

Also, everyone seems to say if you want low down torque go the blower, but just as a thought remember diesel trucks havent used blowers for years. One of the nice things about turbos is that they respond to load more than evrything else.

Yes!

and

42

well since we're on a vw forum I guess we should talk about what is suited to the humble VW.

I would say a supercharger would be best.

Turbo's put too much heat into the exhaust port. Porsche realised this and put cast in liners in the exhaust ports of the 944 turbo. The problem with the VW engine is that the head cooling is not that great, and you don't really want to put any more heat into there. The parallel valves of the VW motor makes it difficult to get cooling air to pass between intake and exhaust and cool the exhaust port / valve properly. Porsche also realised this and cranked the exhaust valve out on an angle to allow cooling air through on it's early air cooled engines. So vw engines already have crap exhaust port cooling and putting anymore heat into there is asking for shorter exhaust valve / cylinder head life. Having said all that there are plenty of turbo vw's running around. I'd put a HPC ceramic coating in the head / exhaust port if going the turbo route.

Superchargers don't put the same amount of heat into the exhaust port as a turbo. I think a VW engine would live longer with a supercharger on it and run cooler.

But I've never tried it so I can't really say.

if you want type 4 seach old posts by amazer who ran a reliable turbo type 4 kombi as a daily driver.

Type 4 motors were in production '68-'82 from Germany begining life as 1.7L in the type 4 car. 2L versions ran from ~'75-'82 They were insltalled in T2, T3 kombi's and porsche's.

Most Porche heads have liners in the exhaust ports. even non turbo stuff. Have a look at a 944 turbo manifold if you ever get the chance, not what most people would call ideal for a turbo! its over a meter of pipe from the head to the turbo!

There are hundreds of stock motors out there with the same problem. Ask him how old that head was before that happened, and what was he towing again? Most kombi heads that fail will be on their second or third re-build, and most likely over 150,000klm between each. Every motor will fail eventually :thumb

My definition of reliable is the same as the dictionary :P

If your talking life of a motor, not reliability, any performance increase will reduce life as you (and I think most people) would already know.

Quote:

Originally posted by Baja Wes I guess it all depends on your definition of reliable. I seem to remember sitting at one particular Valla (2003) watching Amazer try to rebuild his dead turbo type 4 engine at his campsite. Not surprisingly the exhaust ports had failed on both heads. He rebuilt the top end before heading home, when the bottom end gave way part-way there. So I guess reliable is a relative term

greedy51 ran a supercharged type 2 kombi engine for at least two years, maybe try to contact him about supercharger information

for effieciency, a turbo is ahead of a supercharger every day of the week.

people forget three very important things about superchargers;
1. they often produce just as much heat as a turbo because of the pressure they create.
2. they take an amount of power to drive, where a turbo only relies on a little bit of back pressure and heat expansion to drive them.
3. for the same amount of power increase, often superchargers weight far more than turbos. when it all gets down to it, power to weight is where its all at.

Don't get me wrong, I love blowers, but recently read an excellent techo book on turbos and its been a wakeup call for me. Sure, you could fit a little blower to a 1600 like greedy's old setup, but it's certainly not going to be as good as some people will tell you. If you are serious about forced induction, an EFI and intercooled turbo setup will beat a blower every day.

BTW, I am currently thinking out a buildup of a motorkhana special using a 1600. In the long run it will have forced induction and initially I was thinking a blower until I thought about the weight issue. to keep the engine in one piece and the car under 500kg, a proper turbo setup will be lighter and give me more power over a blower. I know some are going to sight Pete Gumley's hillclimb car as being blown, light and powerful, but remember he gets to use alcohol fuel which acts in an intercooling fashion.

centrifugal superchargers are similar in efficiency and weight as a turbo, but unfortunately very expensive.

They both heat up the intake charge, and both will therefore benefit from an intercooler. The difference is a turbo creates a lot of exhaust backpressure which puts a lot of heat into the exhaust port. Superchargers don't do this.

For power in a street car a turbo is the best.

For engine life in a vw motor I am sure a supercharger would be the best.

In the end it comes down to what you like. The whistle and 2-stroke power band of a turbo, or the whine and raw torque of a supercharger.

An excellent example was a friends Toyota sprinter. First he had a 4AGZE (1600cc supercharged). Later he swapped it with a CA18DET (1800cc turbo).

Despite the smaller size the 4AGZE had heaps more torque. Any rpm it just went. I love the supercharged exhaust note and supercharger whine. It was really drivable and was my favourite.

He preferred the CA18DET. Sure it made more power and went quicker, but it didn't respond at lower rpm and required much more gear changes to keep it in the "power band".

Surely it would depend on how much boost he setting the turbo for and the general aim of the setup. WRC cars are limited to 300hp of power by a flow restrictor, but they produce mental amounts of torque and have a very low redline for a competition engine (6500rpm).

Also, it should said that although centrifugal superchargers are the same weight as turboes, they actully provide all the disadvantages of both, ie. they don't come on until the revs wind up and they still put a load on the engine. Besides, if blowers are so good for torque, why have all the big diesel companies gone for turboes? The only car companies that are using blowers on production cars these days are the ones who add the supercharger as an afterthought, and generally without an intercooler I might add.

Wes, I love blowers, but it seems only sentimental hotrodders think they can really produce the goods over a proper turbo setup. You can factor top fuelers into this catorgory too.

VW did use superchargers on the mk2 golf (g60) and also the polo (g40)

To keep the turbo spooled you inject fuel directly onto the exhaust turbine , this is really hard on the turbo . Generally its a good idea to run water injection with this kind of setup to try and cool the incoming air into the combustion chamber . Methanol would be ideal :o

Pete, some light reading for you since I think you have been brainwashed by the turbo book you read

Saab variable compression supercharged engine - really really efficient;
http://www.saabnet.com/tsn/press/000318.html

Mazda miller cycle KJ-ZEM engine - supercharged and really efficient. I almost put one in my car instead of the KLZE
http://www.mazda.com.au/articleZone.asp?articleZoneID=92

centrifugal superchargers are a lot better than you think, and aren't laggy like a turbo, but do build boost with revs.

I think the really high end drag cars use superchargers for two reasons. 1 - a turbo probably can't produce enough boost. 2 - the exhaust housing and turbine would probably melt on a top fuel engine.

Don't get me wrong, turbos are good. But the difference isn't as clear cut as you first may think.

I have driven supercharged and turbocharged cars, and I prefer the "character" of the supercharged ones.

i loved driving the supercharged fatso... really lovely up razorback ranges, sucked fuel pretty hard when you put the foot down.

as stated above its all about driver preferences. there is no better of the two simply because they essentially deliver a different product. much the same as petrol and diesel engines: both are engines, both have ups and downs, but people will drive one over the other because thats the kind of engine they like to drive with.

I was about to say I forgot the miller cycle mazda, but you'd have to admit, that hasn't really taken off, and it still isn't intercooled. As for Mercedes, I think it's more about marketing and tradition than efficiency for them. They have a history of using them, it's like mazda putting a piston engine in an RX8, they wouldn't sell. I know about supercharged 2 strokes (diesel and petrol), but they won't work without one if they have a wet crankcase, so they are not a good example.

I know what you are saying, but I still reckon turbos are a clear winner. And this is coming from a man who'd die to put a supercharger on any car I own.

wes you said it yourself when you were talking about my reference to turbo diesels,

Go the supercharger Chris. You will have more fun.


(lighthearted)
re: the sentimental hotrodders/top fuelers. I tried to do some turbo calcs but my brain melted.
The size of the turbos (they would have to be many) would be huge but NO lag and 200+psi boost. "1.7:1 air/fuel mixture for nitromethane the flame front temperature measures 7050 degrees F (3900 degrees C)" now we'll need some sort of intercooler. 1 pic=1000 words.

Some times you know what is right but you still vote for
what you know and love.
I still love my blowers, and as much as it is bogus I would
love to setup a centrifugal blower with an SU carb on an air cooled street volksy.
It can always be EFI'ed and intercooled later and would
be alot faster to fabricate than a full turbo system.
Plus it would be good to try and impress chicks and my
mates...since that is why most of us do stuff that is silly.
Yes turbos are the go, but Volksy blokes like to do stuff
that is different.