supercharged rb30, why not?

[shane_cummings]

Before you knock it give this some thought.

I have a na rb30 in a r31 wagon. My choices are a high comp na with rb25 pistons and head. I'd have to buy a whole rb25de, probably wouldn't get the torque I'm after.

I could run a na comp turbo setup which I've experieced and can say I would be very happy with. Would need turbo, manifold, oil/water lines, crossover pipe, the list goes on... Then there's injectors and fuel pump.

Why not use a 2L toyota supercharger?

1. They are off a 2L engine that revs to 8000 rpm which means they'd cope with a 3L that need only go to 6000rpm.

2. There would be no oil/water lines needed,

3. It could be completely switchable for daily driving and towing which would keep my economy.

4. Because it's switchable and economy isn't an issue an extra injector linked to a hobbs pressure switch or something similar could be used when on boost instead of expensive computer mods.

5. Turbo's generate more heat and backpressure in the exhaust which brings on detonation, less heat and backpressure means a supercharger could safely run more boost.

6. There is the ability to run a decent set of headers which is more power again.

The only thing will be whether I can retain the air con and whether the distributor is in the way. The superchargers are only about $350 and I know someone who could make the required pulleys and bracketry.

I'm after something that will give me good cheap (relatively speaking) power and torque and will not sacrifice economy too much.

So what have I missed? Who can crush my dreams?

[R31 POWER]

Power steering pump is in the way I think you'll find but if you source a non power steering rack from a pinny you'll be alright.

5. Turbo's generate more heat and backpressure in the exhaust which brings on detonation, less heat and backpressure means a supercharger could safely run more boost.

I think compressed air gets hot reguardless it's turbo or charged.

[browny]

There is a good thread discussing this here:

http://www.calaisturbo.com.au/showthread.p...ghlight=rb30esc

[boj01]

iive seen it done before without too many troubles, dont know all the ins and outs though!

[mr_r32gtst]

I think they use those superchargers on the commondore 3.8 kits. I have also seen a 1 on a patrol with the rb30e. Good luck with it

[shane_cummings]

There's enough room above the alternator on the driver's side, I just need to look at an engine out of a car to see if there's anything to mount a bracket to.

I realise that both turbos and superchargers make heat when compressing air, but only one has a red hot exhaust housing bolted to it.

To keep the whole cost down to a minimum to start with there would be no intercooling. You tend to see plent of superchargers without intercoolers but not so many turbos now days.

If it works well a computer and intercooler could then be worthwhile additions.

I've seen a gemini here with a 3.8V6 and has run one of these superchargers and he has it fully switchable (I've got a feeling he has a different one now), it has the most awesome sound to it when the blower is turned on. It's fairly modified now but I'm told he started fairly simple and got very good gains from day one.

[BOOSTD]

Talk to Castlemain Rod Shop, you might even find they have an on the shelf kit.....Actually I could almost put money on it.

[browny]

CRS do make a kit. My experiance with CRS is that they make some good products and some not so good products. I know knothing of the blower kit but recommend you check it out and choose wisely.

Also, Rod Hadfields general disposition doesn't exactly convince you to buy something off him.

[Sydneykid]

In my opinion, DOHC 4 valve engines are not happy bed fellows with superchargers. The engine's broad rpm range does not suite the relatively narrow rpm range that a supercharger works efficienctly over. ie superchargers don't have wastegates.

[PSI_GTSII]

I'd do it to be different.....

But, at the end of the day the Toyota Blower will struggle to make more than 200rwHP, and as happens to ...everyone...that wants to increase there cars HP they soon become accustomed to it & want more!....then where do you go from there with your little blower?

Turbo's are tried and tested and offer great results for relatively little $$$

RB30's come with Bags of low down torque Turbo's or S/Charged.

[Cubes]

Turbo's are switchable with the right foot..

If anything they may actually help decrease fuel consumption when driven lightly as there is no struggle for the engine to suck air in.

Supercharges on the other hand are parasitic little suckers. They require you to use power to make power.

Same could be said for turbos with their back pressure but this isn't really using power it is preventing power.

Depends if you have money to throw around or have the slight possibility of slapping a big turbo on next to that supercharger.

[browny]

I would love to get warpspeeds thoughts on your comments Joel.

[Cubes]

My thoughts said bugger all?!?!

Just that turbo's are switchable with the right foot and superchargers are parasitic.

No one car argue with that.

[Kaido_RR]

arnt sc, like set a one boost lvl and to increases the boost u need something like a pully kit which is like $900 or something?

[browny]

-Joel-

I had to cut my previous post short...but what I was going to add is...

In warpspeeds posts in the linked thread above, he spends a lot of time describing bypass systems used for improving both the economy and driveability of supercharged systems. He also makes comments wrt the benefits of superchargers vs turbos for road cars.

I thought his comments on controllability and parasitic load (ie economy) would be useful.

I don't understand how turbo's couldn't have a parasitic load. It takes power to compress air. This must come from somewhere.

[Cubes]

I just had a read of the thread.

Warspeed definately knows superchargers like the back of his hand.

BUT..

I'm after something that will give me good cheap (relatively speaking) power and torque and will not sacrifice economy too much.

The supercharger shane is thinking to use is a 2ltr supercharger that makes around 110rwkw at the wheels (160kw at the flywheel), without the supercharger that std motor makes ~80rwkw (Exactly the same as my old VL).

I guess it comes down to if you see 110rwkw being 'good power' in a VL.

Sure the superchargers make good torque but you still have to remember the old rule.

Horsepower = Torque x RPM / 5252.

Bolt a RB25 turbo on the side of the RB30 and it will make 160rwkw no problems with all the boost required for the power on board by around 2000rpm. Throw some more boost at it and before you know it you are making 80-90rwkw more than the supercharger.

It really comes down to what you want and how much power you want.

I personally wouldn't waste the money to only net 110rwkw.

[Warpspeed]

Hi guys, interesting discussion, lots of opinions here...............

It all depends on what you want, how much time, effort and money you are prepared to put into it, and what you expect from the final results.

There is no clear winner between supercharging and turbocharging, each has advantages and disadvantages, but turbos are much more widely understood than superchargers.

There are even many quite different types of superchargers, so that makes it even more interesting, it is just not possible to generalise about superchargers.

But there are a lot of urban myths and misconceptions that get passed on about supercharging. Superchargers have developed a lot in the last hundred years, as have turbochargers, but it would be quite unfair to compare a modern close tolerance screw compressor to a thirty five year old turbo with straight compressor blades and simple oil cooled sleeve bearings.

It would also be quite unfair to compare a state of the art ball bearing turbo with todays computer designed blade profiles and low inertia rotors, to a fifty year old design GM roots blower straight off a diesel truck.

How efficient it is going to be, and how well it works depends more on how it is engineered, and how well the controls work. Nobody today would think of using a turbo without a wastegate and intercooler. A supercharger also needs a bypass valve and an intercooler as well, and if it is properly set up it can give similar if not better results than a turbo on a similar engine.

You get what you pay for. When people think of fitting a supercharger, they often think of the $300 Toyota blowers that came off a 160Kw two litre factory engine. This will certainly work, but it will not work well, particularly on a larger free breathing engine like the RB Nissan.

It would probably work about as well as a $300 turbo that came off a two litre 160Kw engine would. Nobody would expect such a small turbo to perform on an RB30, but they expect mighty things from a similar sized supercharger.

When you start to get really serious about either supercharging or turbocharging, the results can be very impressive either way, but what is most suitable depends on the use of the engine and the shape of the power curve. But there is a lot more to it than that.

The biggest problem with positive displacement superchargers is just the sheer physical size of the thing, and mounting it in the engine compartment, but if you can manage that, there are a few real advantages. The first one is that boost can begin very low in the RPM range without lag, and airflow can be very high at the top end, provided the blower is physically large enough for the job. For a street engine another advantage is the vast improvement in detonation threshold of a supercharged engine. You can run much higher boost or lower octane fuel with a supercharger, because the heat can get out of the combustion chamber.

At full power, boost pressure will be far higher than exhaust back pressure, and with sufficient valve overlap scavenging can be very efficient. The heat can get out. So there is relatively cooler mixture at the beginning of the compression stroke, and much less tendency towards detonation. At any given boost level and induction temperature the supercharged engine will run much further below the detonation threshold.

A turbo engine running at similar boost and power will have significant exhaust back pressure to drive the turbine. Red hot glowing exhaust pipes on the dyno are not that uncommon. The exhaust is just as hot as those pipes, and a lot of it remains trapped in the combustion chamber when the exhaust valve closes. That hot trapped gas mixes with the incoming air undoing some of the good work your intercooler has done. Detonation is the number one killer of turbo engines.

Another thing to think about is compressor efficiency. Turbos usually peak at about 75% on the flow map at one particular flow and boost pressure, and can be much lower everywhere else. A screw blower can be 75% EVERYWHERE throughout the flow range, and there is no surge line either. This not only means lower discharge temperatures, but less drive power required.

Turbos are only efficient over a limited flow range, that is why there are so many sizes and different hybrid combinations. You pick your turbo for response, or maybe top end airflow, but you cannot have both. Show me a 500Kw turbo for a skyline that makes 15psi boost at 1500 RPM ? It is just not possible. But with a suitable screw blower you might just do it.

But if all you want is sheer top end horsepower, a turbo will beat anything else, except maybe a centrifugal supercharger. Turbos are very good in other respects though. They are very small for a given airflow, and a lot easier to install. A turbo installation on an unblown engine is a lot easier than fitting a supercharger to an unblown engine.

Turbos are great, I am not putting turbos down at all. But there are other ways that might or might not be better.

If you want to drive flat out all the time and stay in the power-band, turbos are great. But for a street car, you will not keep your licence very long doing that. Standing starts are also more difficult with a high power turbo. You have to launch it at high RPM, or it just will not go. The higher up in the RPM range the power band is, the more difficult a turbo car becomes to drive.

None of this is true with a well set up supercharger. It can pull from low RPM like an eight litre V8. But you do not get that surge of acceleration as the boost comes in that you get with a turbo. I think that is what is so appealing about high power turbo engines, they are just so much fun to drive.

So where does that leave us ? It depends on what you want I suppose.

[shane_cummings]

My ideal upgrade would be the RB25 turbo and associated intercooling and so on but the car in question is not intended to be a ball of fire, and having just bought a house and saving for a wedding I can't see myself spending money on any sort of management system. The only other way would be a vl turbo computer.

Making the supercharger switchable means fairly crude means of getting fuel in there only when its needed can be used.

If I can get a 50% power gain and good torqe I'll be happy.

I'm expecting it to cost about $600 to $800 with fabrication of brackets etc to be done by me.

If you can suggest a cheaper and equally reliable/economical way to make make similar gains I'd be keen to hear it.