Which one puts out more pressure?

Bobtail · Post by **Bobtail** » Sat Oct 06, 2001 2:04 pm

Just to add a bit of spice to this thread Volvo were developing a compound supercharger which was a turbo mechanically connected to a lay shaft on the side of the engine ,This seemed to provide full time low rpm pessure .
When the revs increased to a given speed the boost was diverted to the inlet side of a bigger turbo ,which was exhaust driven.
I heard of this a long time ago 1980's?
It was fitted to a diesel truck engine about the same time as electronic diesel pumps were being developed.

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www.centralvwaudi.com

calereeves · Post by **calereeves** » Sat Oct 06, 2001 4:54 pm

thats pretty interesting. I wonder how the turbo connnected to the shaft works at high RPM directly feeding the engine?
Cale

Lo Cash John · Post by **Lo Cash John** » Sat Oct 06, 2001 8:13 pm

Guys,
I'm not trying to be a butthead here but...If any of these ideas are that great/efficient at making horse power, why isn't anyone using them for racing or production vehicles? I understand the desire to explore uncharted territory, but isn't the ultimate goal HORSEPOWER? I think the automotive performance industry has proven a 'straight' turbo system to be the most efficient in terms of size vs. power. Drag racers have shown roots type blowers to work very well when space is not an issue. So what IS the point of a Rube Golberg turbo/supercharger system??

[This message has been edited by Lo Cash John (edited 10-06-2001).]

calereeves · Post by **calereeves** » Sat Oct 06, 2001 8:49 pm

John,
I'm not so sure if I'm going for all out performance or if I just want something different... that may sound pretty stupid, but whats the point of having a bad ass bug if everyone else has the same thing. Just being able to say that you have a super-turbocharged vehichle, thats pretty cool. Maybe this is old technology, but the aircraft industry has used this since WWII, I already knew the P51s used it, but Guy Gove enlightened me that more than just one plane used it. Maybe no one has really taken the time to look at this option in the automotive industry due to space and emmissions constraints. I just thought that the supercharger would be more effiecient at turning the turbo than the engines exhaust would. What I'm still looking for is some hard numbers, or some equations I could use to figure out what the VW engine of "X" displacement with "Y"x"Z" bore/stroke and "A"x"B" intake/exhaust valves could flow in CFM. Once I have that, I can tell whether or not, theoretically, this would work. Its just an off the wall idea, that if well thought out, in my opinion, COULD potentially work, and work very well.

I didn't mean to step the toes of any turbo "purists".

Thanks,
Cale

[This message has been edited by calereeves (edited 10-06-2001).]

Ross · Post by **Ross** » Sun Oct 07, 2001 10:35 am

Check these little babies out, they look like they need to be installed on an aircooled motor...
www.z-engineering.com

Lo Cash John · Post by **Lo Cash John** » Sun Oct 07, 2001 8:45 pm

<BLOCKQUOTE>quote:<HR>Originally posted by calereeves:
John,
I'm not so sure if I'm going for all out performance or if I just want something different... that may sound pretty stupid, but whats the point of having a bad ass bug if everyone else has the same thing. Just being able to say that you have a super-turbocharged vehichle, thats pretty cool. Maybe this is old technology, but the aircraft industry has used this since WWII, I already knew the P51s used it, but Guy Gove enlightened me that more than just one plane used it. Maybe no one has really taken the time to look at this option in the automotive industry due to space and emmissions constraints. I just thought that the supercharger would be more effiecient at turning the turbo than the engines exhaust would. What I'm still looking for is some hard numbers, or some equations I could use to figure out what the VW engine of "X" displacement with "Y"x"Z" bore/stroke and "A"x"B" intake/exhaust valves could flow in CFM. Once I have that, I can tell whether or not, theoretically, this would work. Its just an off the wall idea, that if well thought out, in my opinion, COULD potentially work, and work very well.

I didn't mean to step the toes of any turbo "purists".

Thanks,
Cale

[This message has been edited by calereeves (edited 10-06-2001).]<HR></BLOCKQUOTE>

Hey, you didn't step on anyones toes. I just hate to see people throw money and time into something that will not perform as good or better than something else that cost 75% less. That's all. As for the aircraft industry using this technology...Keep in mind that aircraft engines are used in a COMPLETLEY DIFFERENT WAY. They are designed to run at a constant speed and therefore are tuned to make huge power at that specific speed. This is why aircraft engines have such a high torque/horsepower ratio. They don't have to rev-up while under load(the pilot sets the cruise speed or prop pitch and engine speed...done). Automotive engines are totaly different. They have to make power over a range of RPMs so the car may make it's way up to speed using the gearbox. Not only does it need to make good torque, but good horsepower as well. It's rather like comparing apples and oranges...

calereeves · Post by **calereeves** » Mon Oct 08, 2001 12:05 am

understandable, i hadnt really thought about the diff. between the way the aircraft engines run.
Cale

BergRace · Post by **BergRace** » Mon Oct 08, 2001 12:50 am

If you look at the Lancia HF Delta Integrale group 2 Rallye car, it used a supercharger/Turbo combo, where the SC delivered the boost til the Turbo had spooled up. A VERY succsessfull Rallye car.

J.

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-56 T1 hopefully soon with a F.I. T4 (AN engine)

calereeves · Post by **calereeves** » Mon Oct 08, 2001 11:52 am

Do you have a link to where I could find out some info on this car?
Thanks,
Cale

Bobtail · Post by **Bobtail** » Wed Oct 10, 2001 6:13 am

Did you read about those z-chargers NO NOISE!!Well I wont be buying one of them then!

IIRC the Lancia uses a comprex supercharger which compresses the air down a passageway of tapered tubes.
I can only presume it is a spelling mistake and should read COMPLEX!!

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www.centralvwaudi.com

calereeves · Post by **calereeves** » Wed Oct 10, 2001 7:03 pm

Yeah!, those z-chargers sound pretty cool, but I bet they're exspensive as hell! ProCharger just came out with a new one too, "lower" noise, and the cool thing about these is they have no oil lines, you just recharge the oil every 6k miles! I bet its really exspensive too though. I can pick up an Eaton M45 for about 2-300 vs. procharger for 2-3000!
Cale

Andy E · Post by **Andy E** » Fri Oct 12, 2001 4:31 am

I'm pretty sure aircraft use a turbo before a displacement type supercharger as the first stage in a two stage set-up. The supercharger increases the pressure by a contant ratio (well, if you ignore heat losses for a minute) and getting two displacement type superchargers matched wouldn't be easy.

A turbo extracts useful work from the exhaust gas by reducing it's temperature as well as pressure. Using a supercharger to compress and heat air (with all the losses that that entails) and then using a turbine to expand and cool it again (again with loss) so that you can turn another compressor to compress and heat it again will just compound the inefficiencies of each stage. Think of a solar powered light bulb

As for which makes more pressure... well on any engine the manifold pressure must always be higher than the exhaust pressure or you would have no flow.

I'm not helping, am I......

Searoy · Post by **Searoy** » Fri Oct 12, 2001 10:57 am

At say 3000 rpm, on a respectable 2110, which would put out more pressure, a supercharger or the engine exhaust pressure?

Totally depends on the rate of spin for the supercharger. However, turning the supercharger would take horsepower, while the exhaust pressure is practically free.

Also, the exhuast has more velocity, which is actually mroe important.

<BLOCKQUOTE>quote:<HR> If you ran a nice sized turbo off of a supercharger, then
1.) You wouldnt get as much heat build up from the engine exhaust plumbing through the engine compartment. <HR></BLOCKQUOTE>

Or your could just not plumb the exhaust into the engine bay.

2.) You would have more availible boost quicker because the super spins up just as fast as the engine RPM can go up because its belt driven. That would virtually eliminate turbo lag, right?

The exhaust increases with RPM too, so there would be no change in turbo spooling, unless it's negative. Exhaust adds heat that the super doesn't, LOTS of heat, and that heat actually has a positive benefit to the velocity of the flow.

3.) The engine would not have to worry about exhaust back pressure screwing anything up, because it would be routed out just like normal.

Instead it would have parasitic draw of horsepower in order to turn the blower. Since the blower is not 100 percent volumetric or thermal efficient you would spend more horsepower to get the air flow up. Then since the turbo is also not 100% volumetric or thermal efficient you would get less boost and more heat out of the system as a whole.

Does anyone see a problem or flaw in my logic? All commments and input are absolutely welcomed!

Efficiencies, both thermal and voumetric, would kill your output. Just think about it. Superchargers are air pumps. Turbos are air pumps. You're using an air pump to run an air pump.

You want a turbo, use a turbo, or two turbos, parallel or sequential, either way.
You want a blower, run a blower. Hell, buy that twin blower setup on ebay and really turn some heads. Just remember heat is only one enemy. Efficiency, or lack there of, is the other. You want the most thermally efficient and volumetrically efficient forced induction systen you can get, balanced by their parasitic qualities, either through exhuast back pressure or belt load. Balance this with your driving requirements. Outright power? Turbo all the way; yes, just one. Low end torque? Blower. Something in between? There's lots of options, each with their trade off.

Me? I'm going low boost blower for mid range RPM, right where it's most usable pushing around a heavy Type 3. And it'll fit under the lid.

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*** Teach a Man to Fish ***
Searoy

[This message has been edited by Searoy (edited 10-12-2001).]

Searoy · Post by **Searoy** » Fri Oct 12, 2001 11:03 am

I mean: Have the crankshaft drive a supercharger(nothing new there) such as an Eaton M45, or something of the like that requires no intercooling

Who said it didn't need intercooling? Due to the very low efficiencies of the typical roots (even the helical roots M45) it needs intercoling even more than a turbo does. Turbos generally have much higher efficiencies and create less heat. But they also create more boost, which makes more heat, so it's a trade off. It's also easier to route a turbo air charge output through an intercooler, but since the blower generally sits on top of the engine it would be difficult to pass the air throguh an intercooler. It's been done, and it's easier than folks think, if they ust would. My engine will have intercoolers. Unfortuantely due to the restricted available space they will be water to air intercoolers. We all make sacrifices.

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*** Teach a Man to Fish ***
Searoy

Searoy · Post by **Searoy** » Fri Oct 12, 2001 11:04 am

<BLOCKQUOTE>quote:<HR>Originally posted by Cam:
There was a conversion similar done on a SLK kompressor Benz a few years ago.
They left the standard blower and then fitted a turbo of some sort. I have it in a magazine somewhere (emphasis on somewhere!)<HR></BLOCKQUOTE>

The difference is, I believe, that the turbo fed air into the supercharger for further compression. The supercharger did not feed air into the turbine of the turbo.

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*** Teach a Man to Fish ***
Searoy