Supercharging AND Turbocharging

[turboandrew]

Warpspeed, of course not, lot's of things need to change. A 1000 rwhp 2JZGTE would need new cams, possibly better intake manifold, stronger rods & pistons, bigger injectors, etc, as would a 1UZ -and it should make 1000 rwhp with 30 psi. I think we are actually in agreement in some ways. If you left a 2UZ completely stock, slapped on a M112, then a very large turbo, perhaps you would need what you suggested. I made the assumption that the 2UZ would be modified quite a bit to accomodate the twin charging, with the very least: lower compression pistons, better rods, better intake (perhaps a 1998+ 1UZ intake mani), much better cams. I would personally want to start with a motor which, without the aid of SC or turbo, made at least 300 rwhp. That should be very reasonable with the right changes. Given that, I would expect getting to the 1000 rwhp mark could be achieved with around 30 psi intake manifold pressure, and perhaps around 20psi between the turbo compressure outlet and the SC let. Then again, even with a worked over 2UZ, perhaps a M112 is too small. If it is, don't band-aid it with a turbo which needs to have a very high pressure ratio. The whole point should be to have both chargers to not have a high pressure ratio, right?

 

[UZZ30-Québec]

even if you put 1000PSI before the supercharger, the supercharger will act like a big wall to your airflow going to the engine.

if I was you, i'd put a clutchpulley on the blower with a pressure sensor in the manifold. the blower will push your 7-8 PSI, once the turbo is able to push more than the blower and you get more than 8PSI, the clutch disengage the blower.

Also, i would not drive the turbo's air in the blower, but both directly in the intake. with an anti-return valve (one-way valve) on each unit so they won't push against each other.

think of if, if you spin an hair dryer, let's say it's revving 5000RPM. if you're able to blow air against it, it'll spin faster. same thing if you put compressed air agaistn the blower. The problem is, the blower is direct driven, it won't spin faster so it'll act as a wall and only use the air it can pump.

and running a supercharger with 50PSI before it, then the charger must charge this air up to let's say, 75psi (for stock compressing half bar pressure,) it will develop a lot of heat.

Volks actually runs a twin charger system on their europeen 1.4 liter 4 cylinders. You should take a look at how they do it.

 

[nzefi]

even if you put 1000PSI before the supercharger, the supercharger will act like a big wall to your airflow going to the engine.

think of if, if you spin an hair dryer, let's say it's revving 5000RPM. if you're able to blow air against it, it'll spin faster. same thing if you put compressed air agaistn the blower. The problem is, the blower is direct driven, it won't spin faster so it'll act as a wall and only use the air it can pump.

No, it won't. Bad analogy. Read back through the thread - a roots SC is a positive displacement pump which doesn't care about the air density at its inlet.

SC works on pressure ratio - if it makes 0.5bar outlet boost with atmospheric inlet pressure (pressure ratio 1.5) then with 1 bar inlet pressure it will make (Pin*PR) = 1.5 bar outlet boost pressure.

If you had 1000psi inlet pressure it would make ~1500psi outlet pressure, roughly. It just compresses the air a given amount.

Cheers

Nick

 

[Warpspeed]

That sounds about right Nick.

I usually work on 1.5 CFM/Hp, and 1,700 CFM works out to a flow of 48,138 litres of air per minute.

An M112 has a displacement of 1.835 litres per revolution. So assuming it fills to 100% capacity per revolution, at 10,000 blower revs per minute that is 18,350 litres per minute of air flowing through the blower.

So to pass 48,138 litres per minute of air, with only 18,350 litres per minute blower displacement, would require the incoming air density to be 2.6 times atmospheric. It would probably be closer to 3.0 in practice because the blower Ve is not going to be anything like 100% at 10K blower rpm.

The M112 flow map confirms that assumption. It would be far better to replace the M112 with something that has about two to three times the swept volume, and drive it to about roughly the same maximum speed. My choice for this would either be a 6V-71 with 327 CID per rev, or a 6-71T with 339 CID per revolution.

The existing blower has only 1.835 litres per revolution trying to fill an engine that has a swept volume of 2.35 litres per revolution. Overdriving a small blower on a stock street engine is an economical way to get a satisfying power increase.

But for a serious high power engine running at higher pressure ratios, overdriving a really small blower is no longer a viable option. Blower capacity per revolution really needs to be higher than engine swept volume per revolution.

Assuming 30psi to 35psi total boost would do the job (?) that is an overall pressure ratio of 3.0 to 3.3 I would aim for a pressure ratio of something like 1.8 across the turbo, and about 1.8 across the supercharger to begin with. A 6-71 GM blower with 5.4 litres per revolution should fill 2.35 litres of engine without having to work at inefficiently high blower rpm.

The original M112 driven at the standard original speed would need nearly the full 3.0:1 pressure ratio AHEAD of the blower just to fill the blower. That is just silly, and not at all practical.

 

[Lextreme II]

WOW... Over my head...... So with the 4.7 and M112 along with GT40R. What is the potential?

 

[Warpspeed]

Not much with the M112 unfortunately.

 

[Warpspeed]

even if you put 1000PSI before the supercharger, the supercharger will act like a big wall to your airflow going to the engine.

There are two ways of looking at that.

In one respect you are quite correct. If you take a 300 Hp supercharged engine and try to boost it with a turbo to get 1,200 Hp out of it, then everything after the turbo will be a giant restriction to the extra flow. There will need to be enormous boost pressure developed up stream of the supercharger to raise total flow by the required factor of four.

But the supercharger will still be creating positive boost under those extreme conditions, so it will not be the giant restriction you suspect. Why? because the engine will be an even larger restriction than the supercharger. Removing or bypassing the supercharger under those conditions will not increase flow but reduce it.

 

[UZZ30-Québec]

won't the supercharger overheat with all this pressure?

 

[Warpspeed]

Not if the air from the turbo is sufficiently intercooled first.

 

[Lextreme II]

What about bypassing the supercharger at high rpm and high boost? As I mentioned few pages earlier. That will reduce restriction.

 

[Warpspeed]

Bypassing the supercharger is certainly not going to reduce flow restriction, but it will certainly cause an instantaneous drop in boost pressure.

Sounds like a great idea. Imagine you are accelerating hard in second gear with 18psi boost. Bypass the supercharger, and boost drops instantly to 9psi. I bet that is going to really make it go a lot faster, eh ?

 

[stevechumo]

I wouldn't bypass the supercharger. I'd think a separate port for the turbo itself will do its job and the supercharger will also do its own job. The concern is how do we have enough clearance to make a secondary port that can distribute the air somewhat evenly to all cylinders. How about the intake for the supercharger is on the left and the intake for the turbo is on the right? And beneath the supercharger manifold are 8 separate little paths that lead to each cylinder.

 

[LondonBenji]

Just......about......keeping up...... :684:

Okay, so how does this change when twincharging with:

2xturbochargers, into.
2xsupercharges!

:tongue2:

So each half of the V gets it's own turbo and supercharger, heck even their own plenum intake (with the exception of a balancer bar because I heard that is a good idea to help even the pressure).

 

[turboandrew]

Maybe whipple 140AX would work well. Flows 1274 CFM and many examples of supporting ~650 rwhp. That could probably get you a 1.8:1 ratio easily and allow a turbo for the other 1.8:1 pressure ratio. Also happens to be a lot more effcient than roots type.

http://www.whipplesuperchargers.com/product.asp?ProdID=1162

 

[nzefi]

WOW... Over my head...... So with the 4.7 and M112 along with GT40R. What is the potential?

Well see the thing is... lets say you just supercharge the 4.7 with the M112. Then assuming a redline of 7000rpm, and max rpm of 13 500 on the M112 (from Eaton website) this means you will only be making ~4psi boost - not really worthwhile.

And if you have a look at a GT40R compressor map, then it flows a maximum of ~60 lbs/min at choke - another rule of thumb is 10hp for 1 lb/min; so this turbo is roughly good for 600hp (give or take). So in order to hit your 1200hp goal, you'll need two.

The turbo will be your limiting factor, so I'd say 600-650hp.

Cheers

Nick

 

[striker]

Guys come on.

don't feed the turbo output through the supercharger intake, but bypass it.
so SC for no lag super spool up with cappable 550cfm pumped in the engine at a relative low RPM with pully change, then kill the SC at.. say 3500rpm with a Merc magneto pully (yes that fits after a lathe job) and let the turbo(s) take over to get you up to stratosphere levels. and away are alll you're problems... just figure out where you on boost RPM range is with the turbo(s) and alter your pully on the SC to that.

the grasroots boy over here in holland take VW 1.8 engines over 480hp this way...

your constantly talking about compound charging, a complete different set of rules is implied on that mater. go for a parralel set-up and go to the goal on having flow, not exes boost.

the only thing you guy's are building now is HEAT, which will rob you off more power than it will deliver, do you want a driver or an ice-bagged dynoqueen?

ps: Warpspeed don't call David *THAT GUY* if it wasn't for him this forum wouldn't be here.

Grtz Thomas

 

[Warpspeed]

All sorts of truly horrible problems await the development of a parallel system.

So you still want to declutch the supercharger when it is producing full boost eh ? and suffer a massive instantaneous drop in either flow, boost or both. Then what stops the turbo boost from causing the supercharger to spin BACKWARDS at a million rpm draining off whatever residual boost is left ??? Remember declutching it, disconnects it completely from the engine, it surely WILL spin backwards explosively from all the stored air pressure, with nothing to limit the speed either.

And how do you prevent the supercharger from just blowing air backwards out through the turbo compressors ? It will be one massive boost leak. It simply will not be possible for the supercharger to create any low rpm boost at all.

I hear you say, fit a one way flow valve to the turbo. Fair enough. The turbo compressor is then sealed completely off with zero flow, but then with zero flow it will surge it's tits off. With zero flow a centrifugal compressor simply cannot build up any boost pressure, only surge like crazy and make a nasty noise. The surge line on the turbo map is there for a very good reason.

All these wonderful ideas guys. Keep them coming, I have not laughed so much in years.

But enough is enough. I am not going to respond to any more posts on this thread, it has all just become surreal and totally detached from reality.

 

[striker]

valve system that progresivly closes and not abruptly, should do the trick here but that should be on the SC's output also then declutching it is the only way. to get this to work. that's true,

there's one who allready posted the drawing for it.

grtz Thomas

 

[cribbj]

But enough is enough. I am not going to respond to any more posts on this thread, it has all just become surreal and totally detached from reality.

Tony, I think the people here are proposing different ideas in an effort to get their heads around the concept of multistage compression, which can be tough to grasp, until the light goes on and it's Eureka time. I went through this experience and had my little epiphany with multistage gas compressors.

Many of us have had experiences with parallel twin turbo systems, sequential twin turbo's, etc. but I think no one except yourself (Edit: Oops, sorry Wayne - you too!) has had any real experience with automotive compound charging. So some of these ideas may sound ridiculous to one who has already done it, but we're just trying to understand this concept better, in terms of concepts we're already familiar with.

Don't give up on us yet......

 

[LondonBenji]

Warpspeed, chill dude, we are all good in here aren't we?

Frankly I think you have been a wonderful asset to this discussion and I for one would like you to keep posting.

I think people are just having a hard time getting round some ideas, lets lay out some things we've learnt....


1. Blow the turbo through the supercharger.
2. The supercharger is NOT a restriction on the turbo.
3. For simplicity sake, do not bother decoupling the supercharger.

Anything else that should be added?