The debate: what is better. Supercharged or turbocharged?

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

vw54 wrote:How LONG is a piece of string

The roll I bought yesterday is 25 metres.

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

shiftyvw wrote: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.

see, this is where it gets complicated. You can get awesome low down torque from a turbo, but it is compromised because you do so by using a large compressor and small exhaust housing, placing a substantial restriction of exhaust gasses. The net result is a turbo that boosts at 1500rpm on a motor that now won't rev past 4k. No problem on a diesel that won't rev past 4k anyway, but on a high revving petrol motor it's not good. This is where the first twin turbo setups came from, trying to get both low rpm torque and high rpm power, by using mismatched turbos and a very complicated valve system.

Again, it's horses for courses. What scenario are we talking about? Until someone nominates that, it's a meaningless discussion.

[ Edited on 26-10-2005 by Secoh ]

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.

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

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 🙂

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.

Baja Wes wrote: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.

pete wood wrote: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).

WRC cars use complex antilag systems which cause backfires in the exhaust to keep the turbo spooled and almost constantly on boost. I don't think anyone will run that set-up on a turbo vw.

if blowers are so good for torque, why have all the big diesel companies gone for turboes?

because they want efficiency. They don't have crappy air cooled exhaust ports to worry about. Besides, there are heaps and heaps of 2-stroke supercharged deisel trucks out there.

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.

I'll telll mercedes you said that. Haven't you heard of the kompressors? Others use supercharging too, some in very efficient cutting edge technologies (like the miller cycle)

You can factor top fuelers into this catorgory too.

Well actually you can't. All the top fuellers I have ever seen are supercharged

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.

Bug_racer wrote: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

Ahhh.....no you dont.
Let me guess, there is a special fuel injector in the exhaust manifold right................errrrr nope.
Antilag is what you are thinking of.
Just about every aftermarket ECU suitable for turbocharged cars has this feature as standard.

There are quite a few issues to deal with using water and one of them is it condenses nicely in 'cooler cores if sprayed into the turbo mouth.
There are plenty of fandangled ways to work around this but the bottom line is its not worth the drama as a half decent cooler core does close enough to a decent job.
Water is the domain of the archaic draw-thru system.

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,

because they want efficiency.

I don't care about whether it's a VW motor or not, I'm over that debate, I was talking about efficiency.

pete wood wrote: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.

well actually it is intercooled. It has a highly efficient Lysholm screw-type supercharger and is fitted with two air to air intercoolers.

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.

you could use the same arguement for why trucks famous for their turbo engines use turbos.

I don't care about whether it's a VW motor or not, I'm over that debate, I was talking about efficiency.

well I was not talking about efficiency, I was talking about what I thought suited the VW motor the best. So no wonder we don't make sense to each other 🙂 But if you are talking efficiency then you probably will have a hard time finding a turbo engine that is more efficient than the variable compression supercharged SAAB motor anyway.

Turbos are well suited to high revving jap motors. A VW motor does not fit that description, and I think is more suited to a supercharger.

Besides people don't put turbos on their car for efficiency, they do it for more performance. As others have said, turbos and superchargers are just different types of performance.

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.

Dave, I love your supercharged drag car. I have seen it many times over the years, and it's always been my favourite. I love the sound, I love the way it leaps away from the line in a seemingly effortless way. It's a car that legends are made of.

A turbo car could probably beat my supercharged 202 in my EH, but I tell you what it is a whole lot of fun being able to go in a burnout comp and sit in top gear with the motor only doing 3000rpm. The torque is great. It actually feels like the 202 cubic inch motor has been replaced with something in the size of 308ci In a way I suppose that is what the supercharger does. It continually pumps air in at a higher ratio than the motor could naturally aspirate.

Anyway its my car and I like it and that is what counts. I don't think there is an actual debate required 🙂

I thought lysholm superchargers approached the efficiency of a turbocharger/centrifugal but did it right across the rev range?

miller cycle supercharging is an entirely different kettle of fish. The supercharger is not there to make above atmosphere boost per se. Miller Cycle recognises the difference between static and dynamic compression ratios. The inlet valve is held open as the piston is coming back up for the compression stroke. So in theory the charge gas is being forced back through the inlet. This gives a very low static compression ratio and takes much less energy to bring it to TDC on the compression stroke.

To compenaste for the gas charge trying to be forced back out the inlet, the supercharger is used to push it back in again, thus giving the high dynamic compression ratio that the motor needs to fire. At the end of the day it is there to increase fuel efficiency, though additional torque and the ability to boost it some more is a pleasant side effect.

personally i like superchargers better, and have you guy's seen this?

http://www.whipplesuperchargers.com/default.asp

Top fuellers are irrelevant to any turbo vs blower argument. They HAVE to run a roots supercharger and not the most efficient (high Helix) ones either. Presently nothing beats blown moters on the setp of the throttle.

Che Castro wrote:I thought lysholm superchargers approached the efficiency of a turbocharger/centrifugal but did it right across the rev range?

To a point yes but where the turbocharger gains (efficiency) is it works as an "energy recovery" device.

A turbocharger extract and turns exhaust heat into energy to help turn the turbine where it would otherwise be lost out the zorst pipe.

A well matched and set up turbo results in surprisingly low pumping losses (zorst manifold pressure)

A blower provides positive boost pressure but at the cost o9f horsepower that would otherwise go to the wheels, with no energy recovery from the hot zorst gas.

So pound for pound boost pressure, the turbocharger "should" result in a more efficient setup.

However, for drag racing, instant torque is paramount and in bigger arsed engines, the liability of lost power driving the blower is a far lesser evil than turbo boost lag.

Some serious turbo straightliners cunningly get around this lag issue with a decent shot of nitrous oxide off boost for instant power and then reverting to turbo boost pressure alone once the turbo spools.
Yeeehar!

Its just horses for courses.
Turbochargers are significantly more compact and lightweight against an equivalent capacity blower and are easy to mount in just about any position that gives you a stiffy whereas the larger, clumsy blower must be attached onto an engine in such a fashion as to be inline with pulleys and such. This can be quite a bother when allowing for other engine ancilliaries that are belt driven.

FWIW, having done a custom installation in my old Ford capri and currently owning 2 turbo cars, I personally love the shreik and whistle of spooling turbos followed by a "pssshht" on gearchange against the constant sort of mechanical whine of a blower.
However, the in-your-face instant kind of stomp of the blown engine is hard to pass!

For all intents and purposes, for a streetable car, the choice is largely "pay your money and take your choice"

Happy blow jobs.
L8tr
E

hehe. This is going mad. ALot of good info, keep it rolling

Great clean debate without people going off their rockers for others with different opinions, great peaceful rebuttals, nice job. This is avd, great to have an interesting informative talk 😀

Anyone ever think of having both a turbo on the exhaust and a supercharger on the one engine? Be possible? You would need some serious reinforcement on the engine components though with that kind of boost. Never have heard it being done before, therefore chances are its probably a stupid idea.

mynameischris88 wrote:Anyone ever think of having both a turbo on the exhaust and a supercharger on the one engine? Be possible? You would need some serious reinforcement on the engine components though with that kind of boost. Never have heard it being done before, therefore chances are its probably a stupid idea.

No, not silly at all and works very well. A pretty old idea now.

Toyota did one years ago, based on what looks like an 18RG or a 2T (Celica Twin Cam) with a complicated plumbing setup where the supercharger delivered the boost from low down and when the large turbo spooled up, the blower was disconnected via a clutch similar to a magnetic clutch on an A/C compressor.
I never did see how the plumbing was switched and valved but it looked like a freakin snake pit with all these tubes running all over the engine.
A serious looking bit of kit however!

Turboing over supercharging has been done for many years on Detroit "92" TTA series 2 stroke truck and marine deisels.

The supercharger with blow its set boost pressure from ambient but when the turbo gets spooling, the blower will deliver base boost pressure ratio + turbo boost pressure.

A M8 of mine down here in Tassie is currently developing just such a beast of an engine.
Its a Ford Pinto 2.3 litre. Looks identical to a 2 litre Ford Escort/Cortina engine.

He has got a big arsed turbo off something feeding a roots type supercharger. Programmeable EFI and some serious engineering and money unloaded into the thing.
He is a machinist by trade and a very handy fabricator.
The one off billet steel roller camshaft is just one of the bits of pricey trickery that litters this project!
The 20mm thick big end bearing stud girdle is very serious and something to behold!

I have seen the initial build of the engine but it has not fired a shot in anger just yet.

Itseventually going into a heavily modified Mk 2 Ford Escort and it (engine) looks simply awesome in the flesh.

L8tr
E

I think the most successful use of the turbo and supercharger combination was the Lancia Delta S4 rally cars. It was rumoured to have between 500 and 600HP I think, and was insanely fast. Unfortunately it was too fast and when it did eventually crash the occupants were incinerated and group B rally cars were banned due to safety concerns.

The most recent use of turbo and superchargers successfully is probably the Bandag Bullet (worlds fastest Truck!). Of course it is fitted with two V8 diesels, two superchargers and four turbochargers.

As the saying goes...
Turbos are nice, but I'd rather be blown.

Bill Oakey,grandfather of Aussie Top alcohol Drag Racer Dean oakey, built a quad turboed/supercharged Keith Black Hemi 20 or so years ago.He couldn't keep the turbos together, on the step of the throttle the turbos couldn't cope with the amount/force of the exhaust. An experienced Top Fuel driver at the time said it had as much hp as the Fuel motors of the time but from memory never finished a quarter mile. He did have some success with a twin supercharged engine i.e. the first blower compresssing into the second and then to the engine. Wouldn't be legal now .

Go to the shoptalkforums and read the 40+ pages on the same debate...pretty informative.

I have a vf24 ballbearing turbo they used to use on group N rally cars. Makes power from 2600-6500 and has minimal lag.

Why not run both...or what I am going to have on the 914....NOS spooling up a massive turbo.

Mercedes are getting rid of there blowers in preference to turbo's...like the new E65 twin turbo which is limited to 1000nm of torque...and makes it at 1800rpm or some ridiculously low rpm.

With water injection...just have an injector somewhere on the inlet manifold so there is less time for it to condense and get the one that has a MAP sensor and is regulated accordingly.

Couple of pages of mostly waffle and a few smart replies. No one has yet asked for the original poster to refine the question.

What is best: blown or turboed? The question needs to say for what specific purpose.

There are times when the turbo will be best - most of those reasons have been reasonably well stated. Other situations will see the blower by far the best and a turbo could never ever compete. Take a car competing in super gas for example.

A blown car will get off the line make its run and then allow the driver to on and off keeping the torque and instant power just under the right foot to keep under the time but still beat the other to the line which is still running at WOT.

When the question is better framed the debate might be more informative.

Fiction or Fact.....most Turbo cars only rely on the turbo itself with standard bottom ends to produce hps.....most Blown cars rely on a stronger bottom end to run the blower to its potential......JVLRacing???????

i cant even think of the last time i saw a blown super gas car? You dont need a blower to go 9.90!

Faster cars that have to run in gas from time to time that have blowers use it to full advantage because they can on and off in the last quarter of the track. Forcing the other car to run under the index to "apparently" catch up and then run under the index.

It's all academic because the question still hasn't been posed - what is better for what purpose?



[ Edited on 31-10-2005 by HotRodMatt ]

I'd gladly go with a turbo every time. With the advent of electronic boost controllers, launch control, staged boost, anti-lag, twin port wastegates and hybrid turbo configurations there isn't much you can't acomplish with a well designed turbo setup these days.

Look at superchargers. Their major breakthru's in technology in the past few years are basically just improving tolerances and there's also been the development of centrivical superchargers that use turbo style compressors because they recognise the efficency that can be gained. Other than that superchargers have the same issues they've had for years. High air temps (except with capa's new intercooled v8 manifold setup) are a serious issue. An 8/71 on a 493ci I was looking at in darwin when visiting with reub ran air intake temps in the area of 100-105 degrees C at 8lb boost which is frankly insane.

Putting asside air temps the thing people mostly complain about huge power turbo setup's is that although they can have massive top end they also have a lot of lag at low engine speed and as a result low torque. Anti-lag is a partial solution but seriously who can use that from light to light driving in traffic.

Enter the idea of hybrid turbo's. Basically by running a small turbine housing to get shaft speeds going at low RPM and a large compressor to achieve the required air flow for big boost and HP at high rpm's. Early hybrid setups were plagued with issues of boost surging and overboost due to poor boost control. The diaphram based wastegates just couldn't anticipate what was going to happen at certain engine speeds so spikes and eratic power figures were a big problem.

Also, when using a small turbine the exhaust back pressures would get very high at high rpm. Eg: Boost pressure = 25lb, exhaust back pressure = 50lb. This back pressure would reduce the efficency of the engines ability to draw in fuel(even with boost) because when old die-hard hot rodders turbo'd engines they'd choose a cam with big overlap. The exhaust pressure would force intake charge back up the intake till the pressure equalised, then when the exhaust finally closed the engine could actually intake some fuel. This scenario would cause a huge power fall-off at higher boost levels.

The big back pressures would also cause the wastegates to open before full boost could be achieved, because wastegate spring pressure would be being exceeded by exhaust back pressure.

Now thanks to those clever japanese guys the use of electronic boost controllers, twin port wastegates and well designed camshaft profiles hybrids can provide wide torque bands with huge top end power as well, and without anti-lag.

To sort out the cam issue, they close the exhaust valve before the intake opens. This allows exhaust pressures to be higher than the intake pressure with no adverse side-effects. Cam overlap was only used in naturally aspirated and supercharged engines to allow the momentum of exhaust via EXTRACTORS to extract (scavenge) exhaust and help pull in the intake charge. Not needed anymore with boost forcing its way into the engine anymore...

The twin port wastegate control via an electronic boost controller gets around the back pressure wastegate creep problem and the boost surging. Twin port control allows intake pressure to re-inforce the wastegate spring in holding the wastegate shut, then at programmed boost level the gate will be opened by a frequency pulsed solenoid. Most decent boost controllers LEARN your engines boost profile and get better the more you drive them so they eliminate overboost completely.

Well there's my 2 cents! Sure we are all into old air-cooled vw's but I'm a big believer in using as all the new performance ideas to maximise the potential of my car. There is no denying what a well engineered ricer car can do with some decent bolt on's.

iswinkels wrote:An 8/71 on a 493ci I was looking at in darwin when visiting with reub ran air intake temps in the area of 100-105 degrees C at 8lb boost which is frankly insane.

That example is an old roots style supercharger with no intercooler. They are very inefficient set-ups, but look cool.

Let's face it, if someone is going to supercharge a vw motor they will probably use something like a an SC12 from a 4agze or an SC14 from a 1GGZE because they can be found very cheap from jap import shops. They are roots style but have coated lobes (teflon of some kind?) which helps with the efficiency a little. The main difference is they are normally set-up to use an intercooler. They also have electromagnetic clutches to allow you to turn the supercharger on and off.

Then if you have a little more money you'd go for an Eaton supercharger. These are roots style as well, but have helical lobes which really makes them operate more like a screw supercharger. So they are quite a bit more efficient than your old skool BM supercharger. They can also easily be set-up with an intercooler.

All forced induction systems SHOULD be intercooled for reliability and improved performance. Regardless of whether its supercharged or turbo'd.

Some turbo setups without intercoolers reach simular air temps as the 8/71, but with a well designed intercooler with sufficent cooling area its possible to get air temps as low as ambient air temps while on boost, and even lower if you run water spray, or CO2 or NOS intercooler spray.

Baja Wes wrote: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. So I guess reliable is a relative term 🙂

Awww wes, you are so cruel. That engine was a dud I have to admit. But it was also thrown in with the $900 purchase price of the kombi. The head swere probably already cracked and the turbo just plasma cut through them. The one before that which was properly built with 3 times the horsepower lived a lot healthier life. Although it too has cracked heads, the reason it was euthenased was the gritty metal bits in the sump and because I could no longer afford the gearboxes (still havent paid for #2)

As to the best compressor.... I'm thinking my next fast car wont have either. Things with Honda badges are appearing enticing. *reaches for the soap*

i cant give such a technical view. but i think i can agree with the statement that both can be equally as good.

Rotarys for example rely a lot on the torque that a turbo provides to get them as fast as they go. and they go pretty damn fast for a 1.3 litre. and can make quite hgih power.

also a mate has a 57 chev that has a supercharged 454 in it. he is making 842rwhp without the nitrous setp installed yet. and on a street tune. he says he has no problems at all with it and is VERY happy with what he has got.

although he has built his car mainly for burnouts.

so i think both can be used to full advantage depending on what you are building the car for.

Anthony

problem sloved!

...

lol, u serious? 😂

Good for de-icing your carb in cold climates.

this thread was interestingto read as i am currently in the process of re-restoring my type three and i was teetering on that wal of whether to go super or turbo. my plan was to go off an alloy block, with serious bore and stroke, nasty ass cam....that type where the car won't idle and then i was gonna stick an older style roots type super on top with a custom intake of sum sort.
my only problem is that i have been told that both turbo and super suck under natural aspiration and work better with injection. is this true? and if so, whats a custom efi system worth to set up?

jonno

its not that they SUCK under the hood of a carby fed car. many people still use carby s for turbos. would just drive smoother .etc with turbo.


Anthony

a supercharged setup should work quite well in draw through carb mode, as the supercharger doesnt separate the fuel mixture like a turbo does.

Do you want induction sounds or turbo whistles? That is the question.

With a type 3 or 4 engine turbo it is far more easy to use the standard efi manifolds and throttle body and throw on a programmable efi system. If you go the quad throttle route then there is going to be a lot more pipework involved and harder to keep neat. You could also build your nasty cam na engine and still have it idle with efi.

For all efi it will cost more bucks with the hi pressure fuel pump, regulator, return lines. I'm guessing that throttle bodies would cost roughly the same as carbs. Installation I found to be easy, but keeping it neat with the extra wiring and hoses is a problem. I wanted something that appeared as though it came from factory but failed rather miserably once the EFI system went on... and then gave up trying.