Supercharging An Rb20det?

[BHDave]

Does anyone have a dyno sheet of a 2lt engine running one of these superchargers?

You could then compare stock turbo rb20 to some other 2lt straight 6 supercharged engine (a 1ggze maybe?). I have a stock turbo rb20 dyno sheet floating around somewhere for a comparison if it's needed.

Seeing as power is just torque times revs it will be easy enough to compare bottom end torque between the 2 engines.

And then poor old Hakai can make an informed decision rather than base it on a whole heap of opinions of guys who have never supercharged a thing in their life (I am also one of those who have never supercharged a thing in my life). I for one would be interested to see a comparison of some sort.

[mad082]

i know that there is a company that sells these superchargers (off the 1ggze i'm pretty sure) rebuilt for about $1100. they do them in a kit for commodores. a mate of mine went in an auto vx commodore with one in it at 5psi and said it went hard when they flicked the switch to switch it on. so i think that would be a good match.

i had a thought this morning (at about 5.30 when i couldn't sleep). correct me if i'm wrong, but if you were running a 14psi blower, would it be correct to say that it would have more boost at idle than the same blower set to run 7psi. the way i see it is that the boost of the blower (on some anyway) is determined by pulley size. so if you are running a smaller pulley it would be boosting more at idle. just in the same way that when you go to a higher gear you travel faster at the same revs, the blower would be boosting more at the same rpm.

[Hakai]

i know that there is a company that sells these superchargers (off the 1ggze i'm pretty sure) rebuilt for about $1100. they do them in a kit for commodores. a mate of mine went in an auto vx commodore with one in it at 5psi and said it went hard when they flicked the switch to switch it on. so i think that would be a good match.

i had a thought this morning (at about 5.30 when i couldn't sleep). correct me if i'm wrong, but if you were running a 14psi blower, would it be correct to say that it would have more boost at idle than the same blower set to run 7psi. the way i see it is that the boost of the blower (on some anyway) is determined by pulley size. so if you are running a smaller pulley it would be boosting more at idle. just in the same way that when you go to a higher gear you travel faster at the same revs, the blower would be boosting more at the same rpm.

I'm honestly not sure, I don't believe so though. Think about it, I know max boost is determined by the size of the wheel on the blower but at idle (say, 900rpm) I doubt it would be spinning hard enough to generate say 14psi boost? I might be wrong though, especially in regards to positive displacement blowers. I believe I am correct in regards to centrifugal (dynamic displacement) blowers though.

Right now, aftering discovering I can run a twin-screw (lynsholm) positive displacement supercharger AND still use an intercooler and retain stock throttle body setup, I'm leaning towards one of these units.

It is a very hard thing for me to decide. I'm thinking one of the better options would be to buy a 1G-GZE blower and experiment using that, if the results are positive from an old trashy roots type blower then I would imagine they'd only get far better with a high quality, high tech twin-screw blower running 14 or so pounds Plus I could most likely use the same mounting style setup once I've designed one

Keep the input coming people, it's all helping

[Sydneykid]

It is a very hard thing for me to decide. I'm thinking one of the better options would be to buy a 1G-GZE blower and experiment using that, if the results are positive from an old trashy roots type blower then I would imagine they'd only get far better with a high quality, high tech twin-screw blower running 14 or so pounds Plus I could most likely use the same mounting style setup once I've designed one

Keep the input coming people, it's all helping

Have you actually driven a 1G-GZE? What about a 4AGZE? I have and they were disappointing to say the least. Sorta like driving a diesel, lots of low down torque, but no rpm. It just goes flat at 4,500 rpm or so. It’s typical supercharger dynamics at work, limited rpm range determined by gearing.

If you can’t find one of either of those, try an MB 200 Kompressor, that will give you some idea of the best that the supercharger is going to get. Then remember that MB have been at this supercharged thing for a long time and spent millions getting that engine as good as it is. That is why the vast majority of car manufacturers of the world have gone to turbo charging.

I don’t care how long you spend on your supercharged RB, I bet I can beat it in torque and useable rpm with a turbocharger in less than 1 day. That’s a fact and I am no genius, it’s simply because it’s that easy.

cheers

[Hakai]

It was more so of a comparison to the 4.1ltr supercharger...

I believe you'd be much better off with a 2.5ltr and a stock turbo making close to 200rwkw.

There's no point having a shiet load of torque at 2000rpm with the skylines gearing, some torque yes and then a rush of power from 2500-3000rpm onwards.

Even with a supercharger the rb20 won't make as much torque at lets say 2500rpm as a larger motor (rb25 or rb30) running a suitable turbo to spool similiar.

If you do decide to go supercharger on the rb20 your still going to have bugger all off idle torque until it gets going at around 2000-2500rpm or so.

So... drop a 2.5ltr in it with a std rb25 turbo and experience similiar but with considerably more off idle torque possibly similiar mid range yet a shiet load more top end.

I'm tired also.. hope that made sense.

If the 1G-GZE running a roots blower sees good benefits, why wouldn't the same blower, or another blower designed to run specifically on engines around the 2.0ltr mark, see the same type of results on the RB20?

A twin-screw, positive displacement blower should provide great off idle response on the RB20, providing as I said above, I chose one that was rated to run on an engine of ~2.0ltrs, which there are plenty of out there.

Check out www.harrop.com.au under their superchargers. They sell Eaton and Lynsholm blowers.

The following Eaton blowers I believe would suit the RB20 quite well;

M45

Designed for 1.6-2.2ltr engines

Displacement: 0.733 Liter

Max. Outlet Pressure: 2.0 Bar

Max. Speed Cont (inst.): 14,000 (16,000)

Flow at Max. Speed @ 1.8 Bar: 630 cubic metres / hour

M62

Designed for 2.2-3.5ltr engines

Displacement: 1.035 Liters

Max. Outlet Pressure: 2.0 Bar

Max Speed Cont (inst.): 14,000 (16,000)

Flow at Max. Speed @ 1.8 Bar: 810 cubic meters / hour

The Harrop website doesn't have the same detailed stats on the Lynsholm blowers but the closest thing I can see is a the "Lynsholm 1200A Twin Screw Supercharger". I believe this would be quite close to the Eaton M62, if you notice the M62 is rated at 1.035ltr displacement, the 1200A is rated at 1.2ltr displacement. I'm assuming, but might be wrong, that this is a comparible measurement?

Both these superchargers are positive displacement types, which means airflow per revolution is the same throughout their RPM range. I don't know the in depth stuff on how superchargers work obviously, but I would make the assumption that being positive displacement, even at idle I'd have a decent hit of airflow coming from it and I'd also assume that it would continue to produce airflow linearly until the blower peaked at its max RPM. I assume this RPM would be proportional to the engine RPM multiplied by the difference in the size of the harmonic balancer vs the pulley wheel, would I be correct? If I could run a pulley wheel that would have my engine spinning at 6,500rpm that would equate to the blower running at say, 12,500-13,000rpm (to be safe) while not being of such a size that it would be creating more boost than the blower can handle, I don't see why I wouldn't have an awsome powerband from idle to 6,500rpm?

Any further input is welcome, I'm not trying to say you're wrong, just putting my understanding and interperetations out there, corrections are welcome

Cheers.

[Hakai]

Have you actually driven a 1G-GZE? What about a 4AGZE? I have and they were disappointing to say the least. Sorta like driving a diesel, lots of low down torque, but no rpm. It just goes flat at 4,500 rpm or so. It’s typical supercharger dynamics at work, limited rpm range determined by gearing.

If you can’t find one of either of those, try an MB 200 Kompressor, that will give you some idea of the best that the supercharger is going to get. Then remember that MB have been at this supercharged thing for a long time and spent millions getting that engine as good as it is. That is why the vast majority of car manufacturers of the world have gone to turbo charging.

I don’t care how long you spend on your supercharged RB, I bet I can beat it in torque and useable rpm with a turbocharger in less than 1 day. That’s a fact and I am no genius, it’s simply because it’s that easy.

cheers

That's a really good point SK. How is the 200 Kompressor to drive? I don't think I'll get the chance to hop in one anytime soon

My heart is not set on supercharging the RB20, I just want to do something different, if it's at all possible. If it's not a viable option then I will scrap it and go with a built RB20 turbo motor

Obviously Mercedes have done it, I would imagine the 200 Kompressor is a nice car to drive with a good powerband, is it as easy as chosing a supercharger that is suited to the engine, or is there alot more to it than this?

Cheers.

[Traditimeour]

Damn this sounds like an idea, i'd like to try

[Rookie ROX]

Hey,

I'm only new on here, but was linked to this thread and thought I'd contribute some of my limited knowledge.

I notice your discussion about the roots style supercharger, and their inefficiency. I don't believe a word of it. I've taken this next section from a company website, of whom I know the owner, and I also know he has a good knowledge of what he's talking about. Whilst it does have some advertising propaganda, it sheds some moe light on the issue. (Note that this guy sells Magnuson superchargers, hence the references, although he also sells Eatons)

Ok, so supercharging gives more power and more power per dollar, but... Why buy a Magnuson supercharger kit? There are many other brands, Vortech, ATI, etc. Some claim even higher power gains. Warning! This next section is quite long. It takes a lot of text to explain this properly. It's also important to remember that this entire discussion is in the context of the engines we deal with. There are some generalizations that don't apply to two strokes, Diesels, Nitromethane burning dunebuggys, etc.

To explain this I first need to explain the various methods of supercharging. All methods of supercharging do basically the same thing. They force more air into the motor then it could inhale by itself. This allows the engine to burn more fuel at full throttle and thus make more horsepower. However just how more air is forced in varies quite a bit. The following methods of supercharging are commonly used.

1. The Roots supercharger. This is a belt driven pump which has intermeshing lobes which force air into the motor. The Magnuson Supercharger is a modern version of the Roots supercharger. It has various improvements to make it more effiecient. These improvements include three intermeshing lobes per rotor instead of two, and the rotors are twisted 60 degrees to form a helix. The port geometry is also greatly improved over traditional Roots supercharger. Magnuson is the primary manufacturer of modern Roots supercharger kits. Over 300,000 factory vehicles roll off the assembly lines each year with this type of supercharger.

2. Lysholm Screw Type supercharger. This type of supercharger is very similar to the Roots type. Instead of intermeshing lobes it has big intermeshing screws. Externally it looks just like a Roots supercharger. It has some advantages and some disadvantages when compared to the modern Roots supercharger which I will be discussing. A few companies use this type, including Whipple, Autorotor, IHI, and some others.

3. The Turbocharger. The Turbocharger, often called a Turbo and originally called a Turbosupercharger is an exhaust driven compressor. It uses exhaust energy to spin a compressor to incredibly high RPM (about 2000 revolutions per second!) which forces air into the motor. It's compressor section looks nothing like a Roots or Lysholm unit, it's more like a centrifugal fan in a modern hair dryer. Garret and IHI are the most common turbocharger manufacturers.

4. The Centrifugal supercharger. This is sort of a hybrid device. It uses a centrifugal compressor almost exactly like a turbocharger, however it's driven by a belt not exhaust. Centrifugal supercharger kit makers include Vortech, ATI, Powerdyne and a few others. Quite a few companies make centrifugal superchargers, including, Vortech, Powerdyne, ATI, Rotrex, Paxton, and more.

Each of these systems offers some advantage over the other. Each has its srtong points and it's weak points. Here they are:

Roots: OK, we are talking about the MODERN Roots supercharger. A lot of vendors of other types like to compare using efficiency numbers from ancient GMC blowers. The modern Roots supercharger has a few big advantages. First it's the only style that compresses the air outside the unit itself. This means that when its bypass valve is open (standard equipment on all Magnuson kits) it's basically shut off. This means that any adverse effects on fuel economy or emissions during normal driving are negligible. Second, below 10 pounds of boost its efficiency numbers (i.e. power required to drive the supercharger itself and the discharge air temperatures) are really tough to beat. Third is reliability. The Magnuson supercharger requires almost zero maintenance. It only needs an oil change once every 100,000 miles and that's it! It has it's own reservoir so it doesn't heat up the engine oil. Fourth and perhaps most important is power. The Roots type supercharger puts out a lot of power at ALL RPM. Right off idle an engine with a Roots supercharger will typically have nearly full boost and massive power. This power increase will be fairly constant throughout the RPM range.

Lysholm: The Lysholm unit is very comparable to the Roots in most ways. It provides full boost from low RPM. Above 10 pounds of boost it's more efficient then the Roots blower, meaning it has lower discharge temperatures and uses less power to drive it. From a pure horsepower standpoint, above 10 pounds of boost the Lysholm is superior. From an "I actually plan to drive this car on the street point of view" it's not quite as good. The Lysholm has a few weaknesses. First, most street supercharger kits run 8 pounds of boost or less so unless you are talking about a custom built motor with low compression pistons, or you are willing to burn racing fuel, the Lysholm's high boost advantages are lost. The second weakness is that it compresses air internally. That means that a bypass valve can not fully shut it off. The result is your engine burns extra fuel to drive the supercharger at all times, even if you don't need the power. This also means that the supercharger is heating things up all the time which can result in a heat soaked intercooler, totally defeating the lower discharge temps. The fact that it can't be shut off with a bypass valve is the main reason the Lysholm design is not the design of choice among major auto manufacturers. It's worth noting that some attempts at shutting it off with an electronic clutch have been made, none have been successful in aftermarket applications.

Turbochargers: Removed this section mainly becauses it's not relevant to the discussion

Centrifugal Superchargers: Let's get one thing straight. NOBODY has built a factory supercharged car using one of these things since 1964, and every company I know of that did it back then is now out of business. Why is that? Because while the centrifugal units are great for certain applications they are poor performers on street cars. Here is the main problem. Their boost increases as the square of the engine RPM. In other words when set up for 8 pounds of boost (about all you can run safely on a modern motor with pump gas) on an engine with a 6000 RPM redline they will only provide 2.8 pounds of boost at 3000 RPM. Now for some real math. With 8 pounds of boost at 6000 RPM an engine will gain about 54% more power. With 2.8 pounds the power gain will be only 19% at 3000 RPM. Obviously below 3000 rpm the power gains would be insignificant. Take a look at your tach when driving on the street and see where you are really operating the motor. It's rarely in the range where the Centrifugal will be giving a lot of boost. With the same 8 pounds of boost all the other types would be giving the full 54% increase through the whole RPM range. The Centrifugal units do have some advantages. First they cost less power to drive then all other belt driven types. They also have lower discharge temps. This means that at 6000 RPM with 8 pounds of boost and everything else equal they will put out slightly more horsepower. The problem is that in a race by the time they reach 6000 RPM the cars with Roots, Lysholms, or Turbos will be long gone. The other big advantage is that it's A LOT easier to make a kit using a centrifugal unit. I know, I make custom supercharger kits! They have lots of fitting for easy remote mounting and they have round intake and discharge ports which are easy to attach tubing too. With Roots or Lysholms there is A LOT more stuff to be manufactured. The commercial success of Centrifugal superchargers is due to two factors. It's a lot easier to make the kits, and they can advertize a higher peak horsepower number which is all the uneducated buyer looks at. The reality is the lack of power througout the RPM range means you get beat by every other supercharged car on the road.

Now I may seem a bit negative about the Centrifugal units and I don't really mean to be. For certain applications they are great. For example if you are building a 2000 horsepower car set up for drag racing with closely spaced gears they just might be the way to go. This is because the car will be traction limited at the low and mid range end of low gear so the lack of boost is not a factor. Once the car gets going the closely spaced gears enable the motor to stay right in the range where it makes power. If you are going to set a car up this way the ATI Procharger is probably the way to go. The car will make more power then any other belt driven system and not have the spooling up issues of a turbocharger.

In Summary here are the advantage of the Roots supercharger

VS Lysholm the Roots offers better fuel economy and better performance at the boost levels you are likely to use. Plus it offers reliability proven in over 300,000 factory applications a year.

VS Turbos the Roots offers more power under the curve and probably more power period below 8 pounds of boost. The Roots supercharger has no lag, and a lot more power at low RPM. The Roots also has the edge in reliability. As I said, try and find an aftermarket Turbo kit with a 3 year warranty, or any powertrain warranty at all!

VS Centrifugals. This one is easy, A lot more power under the curve (that means throughout the RPM range) and proven reliability.

For a street car the Roots supercharger is simply the best way to go. I am sure there are some who will disagree but consider that G.M., Ford, Mercedes, Aston Martin, Mini and others came to the same conclusion as a result of their own reasearch.

The Magnuson kits we sell use a Modern Roots type supercharger. They use Eaton internals in their own case designed for each application. They all have built in bypass valves and they all place the throttle on the intake side of the supercharger. (All OEM supercharged cars place the throttle on the intake side because it's the best way to do it. Many aftermarket manufacturers don't. This causes some driveability issues which can never be totally eliminated.) Everything about the Magnuson kit is top quality and built to last. From the supercharger to the Dayco belt tensioner to the pulleys, everything is the best. This will probably be the most trouble free upgrade you will ever install.

I hope that sheds some more light on discussion at hand. Good luck with your project, I'm contemplating a similar thing only to my Alfa (Sssh! Secret!), so it's always useful to read more info from other sides of the manufacturing world!

ROCK ON

R~R

[Freddy Kruger]

one problem with supercharging a manual car is that if you miss a gear and give it a good hard rev in neutral you are boosting the motor up with no load on it. this is one reason why holden never made manual supercharged v6's.

the reason why was because the t5 gearbox is crap. it just couldnt handle the low down torque of the s/c v6...

[Cool Hand Luke]

hmm, i'd be personally going to RB25 or 25/30 combination before spending money on a supercharged RB20. If i remember correctly, when todd wilkes changed his supercharged holden ute to a twin turbo, he ranted about how much more torque the twin's made.

A centrifugal supercharger wont make full boost untill max rpm, so possibly before the stock turbo is able to make any boost, the supercharger will better the turbo, but aftere 3000rpm the stock turbo can make full boost... Centrifugal supercharger isnt going to do that.

Also if your diriving below 3000rpm and are looking for big torque or power, maybe you should have an rb30.. Even then, it'd only make power from 2500rpm... I had an RB20 with a RB25 turbo, front mount, re-mapped ecu etc in a 180sx. In 2nd gear at 60km/h if you popped the clutch it would go sideways, had almost no more lag than a stock turbo, and prob made 180-190rwkw, made good power from 3000-7500rpm, and pulled well to its 8200rpm rev limit.

As someone else said, with the gearing of your RB20, 2000-2500rpm wouldnt be very useful, as it'd be over and done with in a few secs.

[mad082]

just sat down to come up with some way to do something different, by doing a complete motor transplant. some of these might not fit, or might be way to expensive to do, but if different is what you are after then these may give you an idea.

some motors to transplant in-

1jz-gte

2jz-gte

13b (been done in a few 180sx's don't know if it has been done a a skyline)

turbo hilux motor (been done in a 180sx) very different

honda s2000 motor (buggers me what code the engine is) 9000rpm anyone?

sr20 (bit less power but a bit more torque. but they sound like crap)

just throwing ideas out there.

[Hakai]

Hey,

I'm only new on here, but was linked to this thread and thought I'd contribute some of my limited knowledge.

I notice your discussion about the roots style supercharger, and their inefficiency. I don't believe a word of it. I've taken this next section from a company website, of whom I know the owner, and I also know he has a good knowledge of what he's talking about. Whilst it does have some advertising propaganda, it sheds some moe light on the issue. (Note that this guy sells Magnuson superchargers, hence the references, although he also sells Eatons)

I hope that sheds some more light on discussion at hand. Good luck with your project, I'm contemplating a similar thing only to my Alfa (Sssh! Secret!), so it's always useful to read more info from other sides of the manufacturing world!

ROCK ON

R~R

That's really awsome info mate, thanks heaps

I didn't know that external compression actually had advantages, what little I could find about it in my short searches was unhelpful, but that info you gave is top notch. Looks like a roots blower wouldn't be too bad of a choice after all. Although, considering I have the RB20DET, it's already got 8.5:1 compression and it can handle like ~20psi from a GCG hi-flowed RB25 turbo (Or so I read on here somewhere) without changing internals, I'd assume it'd be good to cope with 15-16psi from a lynsholm blower? I know that airflow makes power not boost pressure, but I'm not sure on the airflow per psi of boost that type of blower would make, so my guess is just that, a guess, I might be wrong

Starting to look like this exercise is not going to be too easy to undertake and might not be for me, but I'll keep looking into it. Keep the ideas coming, if there are any left

[StockyMcStock]

didn't have time to read the whole thread, but i'll put in my 2c here anyway.

i designed and built my own SC-14 charged setup on my RB30 a few years ago. it went from 91rwkw to 131rwkw on the same dyno on consecutive power runs with the blower switched off then on, no management changes. this was using the standard n/a management, not tuned at all. the car went quite well but lacked top-end power as you would expect from such a poor old supercharger. it was making just 3psi at max power!

now, i have been busy working on my twincharge project and have had neither the time or money to do another project. but i know a certain gentleman in melbourne who is (very slowly) piecing together the parts to do a rather different GTR engine package using a supercharger. the ultimate aim is, i believe, 500hp at the engine and a torque curve to die for.

if i were to do it with an RB20 i would use a lysholm (whipple or opcon autorotor) 1600 blower, a good set of extractors and exhaust and some tunable management, along with all the necessary aids that you would usually need (intercooler, fuel system etc). having personally seen and dissected the 1600, 2300 and 3300AX Lysholm flow/rpm/outlet temp/delta pressure maps it would be just right for the RB20. flow maxes out at around 500hp worth of air, so if you wanted 400 at the engine it would do that nicely. the 2300 will go out to 750hp or so, the 3300 upwards of 1000hp.

i would also be tempted (if the engine wasn't being pushed TOO hard) to run a high compression engine, in other words simply use the DE version of whichever RB you have. no exhaust back pressure means happy cylinder scavenging and nowhere near as much reason to drop the compression ratio as you would for a turbo engine. then there is the boost delivery of the lysholm blower to consider, you will have full boost from right off idle all the way to redline, with no taper at the top end.

all in all i think it would make for a great engine, and would certainly sound the goods. i say go for it!

[StockyMcStock]

Lysholm: The Lysholm unit is very comparable to the Roots in most ways. It provides full boost from low RPM. Above 10 pounds of boost it's more efficient then the Roots blower, meaning it has lower discharge temperatures and uses less power to drive it. From a pure horsepower standpoint, above 10 pounds of boost the Lysholm is superior. From an "I actually plan to drive this car on the street point of view" it's not quite as good. The Lysholm has a few weaknesses. First, most street supercharger kits run 8 pounds of boost or less so unless you are talking about a custom built motor with low compression pistons, or you are willing to burn racing fuel, the Lysholm's high boost advantages are lost. The second weakness is that it compresses air internally. That means that a bypass valve can not fully shut it off. The result is your engine burns extra fuel to drive the supercharger at all times, even if you don't need the power. This also means that the supercharger is heating things up all the time which can result in a heat soaked intercooler, totally defeating the lower discharge temps. The fact that it can't be shut off with a bypass valve is the main reason the Lysholm design is not the design of choice among major auto manufacturers. It's worth noting that some attempts at shutting it off with an electronic clutch have been made, none have been successful in aftermarket applications.

and i call bullshit on a lot of this quote too. my reasons:

1: lysholm blowers are NOT very comparable to roots blowers, for reasons which the author later goes on to describe HIMSELF.

2. the lysholm is more efficient everywhere than any roots blower i've ever seen charts for, because it has an element of internal compression, which the author later goes on to describe.

3. "That means that a bypass valve can not fully shut it off". While this is technically true, looking at the 2300AX flow chart gives me a total power loss of less than 5kw when the blower is at 5000rpm and pressure change is 3psi. the chart goes off the bottom scale here but it would be safe to say that at idle, with an open bypass gate, your 700hp supercharger would be pulling less than 1kw from the engine.

4. "This also means that the supercharger is heating things up all the time which can result in a heat soaked intercooler, totally defeating the lower discharge temps." OOPS, that's bullshit too. outlet temps go up only when the blower is actually making pressure changes. if you have a bypass gate, it is completely unloaded at low throttle and idle, and outlet temps are always below 40 degrees. regardless of this, your gate will be recirculating the air PRE-intercooler so that "hot" air will never even make it through the intercooler core until you start boosting.

/end rant. buy a lysholm.

[Kozeyekan]

Hakai, good luck with this. I think most people have floated the idea before, but seem to lack the impetus to move beyond the theoretical.

If you get the supercharger going, keep us updated, show us the dyno sheets, and hell, you might even be a bit of an innovator.

Good luck with it all, Hope you get some awesome results.

[Hakai]

Hakai, good luck with this. I think most people have floated the idea before, but seem to lack the impetus to move beyond the theoretical.

If you get the supercharger going, keep us updated, show us the dyno sheets, and hell, you might even be a bit of an innovator.

Good luck with it all, Hope you get some awesome results.

With so many different opinions it's really hard to make a decision.

StockyMcStock made some very good points and also provided some very positive information and as he's speaking from experience when he says lynsholm blower of that size would be suited to the RB20 it gives me a bit more hope

Stocky, just to clarify, these are the superchargers your're referring to when you say you've dissected them personally before aren't they?

If so, what about this one? I know it's a step down from the 1600, but is it more suited to my application?

As I've said a few times in this thread, I am looking at supercharging because I want something different, and the off-idle response would be awsome I think. However; I want a compressor that is going to remain efficient until the high side of 6,500rpm on the RB20DET (8.5:1 compression). From your experience, which of these compressors (from the harrop website) would you recommend?

Thanks for the replies. Keep em coming, I haven't given up yet

*EDIT*

P.S: Stocky, maybe you can answer my question in regards to the airflow differences of a lynsholm blower of whatever size you are going to recommend, and a turbo such as the Garrett GT28RS? The reason I ask is because many people will testify that the RB20DET internals will run up to ~20psi through one of these turbos and I would like to have a rough idea of how this compares to a supercharger. How much boost would I be looking at running through this type of supercharger to obtain an equivilant airflow rate? (Ultimately, I don't want to blow my engine, I know the RB20DET is a strong bugger, running ~20psi through a 320hp turbo like the GT28RS on stock internals is impressive, I just want to know what I'm dealing with)

Edited July 11, 2006 by Hakai

[StockyMcStock]

Well look at that, Lysholm started making a smaller blower than the 1600. First i've seen of a 1200 but i haven't been looking into them for about a year now.

To size you one properly, i would need to know how much power you are chasing. On the RB20, anywhere up to 200rwkw i'd use the little 1200, it should be fine (note that i have not seen flow charts for it, but extrapolating from the other larger maps this is what i see) and anywhere up to 280rwkw i'd use the 1600. above that i'd go for the 2300. the lysholm blower will give you crisp boost response right off idle and hold it all the way through the top end. it's the best choice unless you can afford an Opcon Autorotor (basically an upgraded lysholm, but you pay for it)

sizing turbos and superchargers like this and giving any kind of meaningful comparison is very tricky, and largely useless anyway. a few helpful things to consider;

- your supercharger setup has no exhaust back pressure, hence no pumping losses in driving the turbine. this means more power. conversely, it requires crank power to drive the blower, so for the 2300AX you'll be using 30KW to drive the blower at 8000RPM, producing 1 bar of boost and 16 cubic metres of air a minute. this is, um..... quite a bit. and the blower has a safe redline of 14,000rpm. you see where i'm going.

-because you have no exhaust back pressure, you get very good (read: almost perfect) cylinder scavenging. hence, a cleaner, colder, denser charge each time it fires. this means more power again. but not only that, because your charge is cleaner, colder and denser, you can run more ignition timing before it pings. again, more power.

-you're running further from the detonation threshold, so you aren't too worried about it pinging so long as it's tuned properly. operating within sane power levels, if it doesn't ping, it won't blow up. pretty simple really.

- for all the above reasons, you don't need to have a static compression ratio as low as you normally would on an OEM turbocharged engine. 9:1 would be great, 10:1 would probably do just fine as well. you would have a very nice power delivery too. 8.5:1 will do just fine if you don't want to change it though.

if i had to guess (which i dont' like doing) your setup might run something like this:

RB20DET

1600 lysholm

excellent intercooler

management

excellent exhaust system

big cams?

i would suggest it would probably take you 12-15psi to get to 200kw atw, although my knowledge of the RB20 is limited. i know when we did calcs on my RB30DE plus a lysholm 2300 we were looking at 14-16psi to make 300rwkw.

either way the final power figure is irrelevant, what matters is how it feels to drive on the road. with instant boost response and a flat torque plateau that just never stops, it will be a very nice thing to drive. it will sound pretty mean too i reckon.

[mad082]

i've been thinking about the 14psi is not 14psi comment for a while now, and i've come to the conclusion that generally speaking 14psi is 14psi. i have racked my brain over this. sure things like heat from small turbos and that sort of thing come into it, and i'll accept that. but you get to a point where 14psi is 14psi.

this is my reasoning. you look at all the big turbos. they make big power, but at big boost. it is like saying 100kmh is 100kmh. if you do it in 3rd gear it may rev at 4000rpm and produce a bit more heat, but if you do it in 4th you are still going at 100kmh but a bit more efficiently.

the subject car is stock and you change nothing but the turbos. if you have a turbo that is efficient at 18psi running at 14psi and another turbo that is effiecient at 28psi running at 14psi the power is going to be similar. sure the 28psi turbo will have a bit less restriction on the exhaust so the air can escape better, but on the compression side it will flow about the same. the wastegate is controlled by the compressor side of things. the 28psi turbo will have a bigger compressor so it will be able to flow more air. however, because a motor has restricions, like an intercooler, and the motor itself, that limits the airflow. the bigger turbo has a bigger compressor which takes less rotations to pump as much air as the smaller one, but once it flows enough air to create 14psi of pressure the wastegate opens and it stops increasing the air it is flowing. the smaller turbo will be spinning faster to create the same amount of air. the motor can only take in so much air, and once you start flowing above that amount you are raising the boost and the wastegate opens to lower the boost back down to the lower pressure so the turbo slow down.

now not much of that may make sense but i just had a thought of a simplified version.

you have a length of hose with a restrictor in the end of it that limits the flow (the way the engine does. it can only suck in so much air at a fixed rpm) half way along the hose you have a pressure valve that releases any excess pressure (wastegate). this means that the pressure between the regulator and the hose is always 14psi. now turn the hose on so that it just opens the valve. there will be a fixed amount of water coming out of the restricot at the end of the hose. now crank the hose up. there will be more water coming out of the regulator, but no more coming out of the end of the hose than there was.

feel free to debate it or correct me, but use examples, don't just say it doesn't work like that. remember my example is on the one car changing nothing but the turbos.

[Cubes]

The Lysholm blower definitely looks like a good thing.

What are they worth? I've had a bit of a google but unable to find any prices.

I think with the rb30 you'd have to run VL style diff gears to make use of the torque otherwise it would be wheel spin and gearchanges every half a second.

[Cubes]

i've been thinking about the 14psi is not 14psi comment for a while now, and i've come to the conclusion that generally speaking 14psi is 14psi. i have racked my brain over this. sure things like heat from small turbos and that sort of thing come into it, and i'll accept that. but you get to a point where 14psi is 14psi.

Mad082, you are right given everything else equal, 14psi worth of air is 14psi worth of air.

Forget the airflow side of things for a minute and think about how a motor makes use of the air supplied, everything I'm about to say has already been said so I'll simply quote.

I'll quote Stockymcstock.

- your supercharger setup has no exhaust back pressure, hence no pumping losses in driving the turbine. this means more power. conversely, it requires crank power to drive the blower, so for the 2300AX you'll be using 30KW to drive the blower at 8000RPM, producing 1 bar of boost and 16 cubic metres of air a minute. this is, um..... quite a bit. and the blower has a safe redline of 14,000rpm. you see where i'm going.

-because you have no exhaust back pressure, you get very good (read: almost perfect) cylinder scavenging. hence, a cleaner, colder, denser charge each time it fires. this means more power again. but not only that, because your charge is cleaner, colder and denser, you can run more ignition timing before it pings. again, more power.

-you're running further from the detonation threshold, so you aren't too worried about it pinging so long as it's tuned properly. operating within sane power levels, if it doesn't ping, it won't blow up. pretty simple really.

- for all the above reasons, you don't need to have a static compression ratio as low as you normally would on an OEM turbocharged engine. 9:1 would be great, 10:1 would probably do just fine as well. you would have a very nice power delivery too. 8.5:1 will do just fine if you don't want to change it though.

Then after all that think about a the compressor side, a larger turbo generally provides air more efficiently than a smaller turbo, check out a few compressor maps and note how compressor efficiency drops off drastically on the smaller turbo's at high airflow rates. This obviously is a power killer and adds heat to the charge.