Hakai

I'm impressed by the coherence of this post. I would have thought that seeing school's out as of this morning you would already be off guzzling bags of goon like it's water. That's what you fully sick ghetto thugs do now days isn't it?

So it is in fact true that the 2530KAI will spool faster than the GT-RS, but it's due to less rotating mass, if I understand what you're saying correctly? Sounds like for both purposes (Price and response) the 2530KAI is deffinately my best choice. Infomation has helped alot, thanks all Ben.

I searched for all the keywords I could think of that were relevant, the search function has never liked me at all, I can very rarely turn up anything useful. The links helped, had most of the info I needed to know. Thanks Paul. Ben.

Since toying with the idea of putting a supercharger on the RB20 went down in flames (Read: Cost) I'm currently looking into turbo upgrades, and I was recently talking to Tom from www.bd4s.com.au. I was enquiring as to the price of their HKS GT2530KAI units. He wrote me back telling me that the HKS GT-RS is a better turbo. He claims that it will spool faster than the 2530 and also make more power through the range. I looked at the HKSUsa website and it appears that the GT-RS and the 2530 both have the same exhaust housing and wheel specs, but the GT-RS has a larger compressor side, does this mean, as Tom is saying, it will spool faster and make more power through the range than the 2530? Another thing I am concerned over is the fact that HKSUsa only list the GT-RS as being supplied with a T25 flange, I was under the impression that for a unit to be bolt-on for the RB engines, it required a T3 flange? Any insight would be greatly appreciated, as well as any experienced people have had with either of these units, especially on the RB20. Cheers, Ben.

Don't encourage him! He's a dangerous man.

I don't think!!!! I promise!! *Thinks* *Runs*

This example can't really be related to a turbocharger. The reason for this is because with a turbo you have a compressor pumping air INTO an object that it is then also expelled from. While pumping air into a bike tyre, it isn't being expelled anywhere. As I said in my post above this one, quoting Stocky, the increase in airflow is due to a lessening of restriction on the exhaust side. As SK has said plenty, and has been reiterated here quite a bit. Boost pressure is ONLY a measure of RESISTANCE to AIRFLOW. If resistance changes, then for boost pressure to remain the same, airflow MUST change with it. There is an increase of air going past the afm, there simply has to be. If boost pressure is a measure of resistance to airflow, then boost pressure is, as I said in the post above, a calculation based on both airflow and resistance to airflow. For boost pressure to remain the same when you change the resistance to airflow (Which is what you are doing by decreasing resistance on the exhaust side of the engine), the airflow simply HAS to change. It's a basic mathematic principle. I'm not trying to say you're stupid, don't take me the wrong way, just trying to help you understand I felt like an idiot when Stocky corrected me heh, but in the end I understand a bit better now *EDIT* I just thought of something else. Your example with the bike pumps. You say that when you pumped with 1 cylinder it peaked at about 70psi? And with 2 cylinders it peaked at about 100psi? Those pressure readings are indicitive of the tyres resistance to the airflow that you were generating with the pump. Examine this for a minute. Using 1 cylinder the resistance to the airflow created is 70psi. You'd think that when you're using 2 cylinders, and effectively doubling your ability to generate airflow, that the resistance would increase to 140psi. However; It didn't. The reason I believe this to be, is that while it provided 70psi of resistance to the airflow from 1 cylinder, it could in fact, handle more airflow it just needed that airflow to be provided, which is why, when using 2 cylinders, providing double the airflow, instead of the pressure doubling, you only saw a 30psi increase. Pressure is resistance to airflow, what that tells us is that the majority of the extra airflow generated by the 2nd cylinder did in fact flow freely into the tyre. We can deduce this because that airflow was not resisted enough to turn into an increase on your pressure gauge Using 2 cylinders, you would have in fact pumped the tyre up much faster than using 1. Setting a pressure limit of 40psi (When 1 cylinder peaks at 70spi) is completely negating the advantage of using the second cylinder. See where I'm going with this?

This example you've used illustrates exactly what I was talking about. Yes, each of the cubic inch of areas will have the same pressure and will contain the same volume of air, the key is exactly what you said, there is more of those pieces in the truck tyre. Knowing this, if you add up all the pieces together, you end up with both tyres having the same pressure level, but the truck tyre has more air in it. Same for my example. Sure if you remove one tiny piece of the whole you get each being equal, but when you add everything together to create the final product, they are not in fact equal. Basically, they have the same pounds per square inch of air each, there are just more square inches that require filling in the bigger tyre and hence the bigger tyre has a higher volume of air in total. I will admit that I was unaware of the technical reason for the airflow increasing in an engine when a larger turbo was fitted, I assumed it was because the turbo itself was bigger. The truth as it seems, as Stocky pointed out, is that the flow increases due to a lessening of backpressure on the hotside of the engine. Thereby decreasing the resistance to airflow on the intake side. As the resistance to airflow is decreased, the amount of air required to generate the same pressure level increases. That's about it If you wanted to look at it mathematically, then I'm sure there is a formula for working out pressure based on airflow and backpressure. But mathematically if you have a formula consisting of 3 values and you change one of those values, then it is not possible for one of them to remain the same, unless you also change a second value. In this case, you decrease backpressure, you want boost to stay the same, you must increase the airflow. I suck at explaining, but I hope this helps a bit more.

Ok from this I'm understanding that when you upgrade to a larger turbo, the exhaust side of the turbo is flowing more freely, which in turn imposes less resistance to the compressor side allow it to flow better? If I cross that with what SydneyKid said (Boost pressure is only a measure of resistance to airflow), then my brain is telling me that with this new, free flowing characteristic, there is less resistance to the airflow created by the compressor. If there is less resistance to the airflow being forced into the system by the compressor, then the turbo will have to flow a higher amount of air for the boost pressure to reach a given level? Is this correct? I'm tired I'll think it over some more while I sleep. It'll be good to finally understand this once and for all heh. Cheers.

I wasn't intending to refer to power, only airflow. I thought my example was correct in explaining why a larger turbo will flow a higher volume of air at the same given boost pressure level than a smaller turbo? *EDIT* With the MR2 example, I was under the impression that higher airflow packs more air into the chamber for combustion which = more power? The exhaust being less restrictive makes sense too and I hadn't thought of that, but surely it's a combination of both?

First let me say SK that I do have alot of respect for your advice and I realise that someone with your experience could very easily out-do what I want to put together. However; That aside, I do want to do something different. As Stocky and Warpspeed have both said, I could produce a good power figure with a very drivable street car from supercharging the RB20 and it's something very, very different, which is what I wanted to do Although, as Warpspeed has pointed out, alot more than I thought, will need to be upgraded and the cost just isn't in my price range I do appreciate your input though SK Cheers. Exactly what I wanted to know. Would be awsome to have snappy response off the line and it hold all the way through the rev range. Your guess as to my possible setup is pretty much what I was thinking as well Except I had thought more towards the 1200A, but if you think the 1600 will be better, I'd trust your judgement. I also agree that the final power figure isn't that relevant, I too really only care about how it feels to drive. How much torque are we talking about here The sound would be incredible I'd imagine also. Thanks again for the reply Warpseed All this info is starting to come together and scream in my face that it would be awsome, just as I imagined it would be. It's good to hear that it wasn't a completely stupid idea in the first place You do bring up some really good points though, as I said just up a bit in this post. The costs are something I didn't calculate very well. Cost is the thing that is starting to put me off this whole idea, maybe one day when I have money to throw around Another thing is that I might still have a buyer for my car, guy who was buying it, his best friends father is a panel beater and can repair it cheap, so I might still sell the old girl, only found out today Thanks to everyone for the information, I'll be keeping every scrap I've saved and hope that one day I can actually put it into practice. Do what Warpspeed said, start with an R32GTR and build on that... RB26DES anyone?

I'll use the example that best helped me to understand this when I was wondering why as well This is all 100% theory, you could do this in practice, but I have never done it. It is however; an easy to understand explanation. 1)Take two lengths of PVC pipe, one 40mm and the other 50mm. The length is irrelevant but assume they are at least of equal length. 2) Plumb a pressure gauge into each pipe, at the same location in the pipe. 3) Pump water through each pipe until the pressure reaches and sits steadily on 14psi. 4) Observe the amount of water flow coming out of each pipe. What you will find is that the 50mm PVC pipe will have far more water flowing out of it than the 40mm pipe, even though they are both pressurised to 14psi. The reason for this is simple, as SydneyKid has said a few times, pressure is only a measure of resistance to flow. The 40mm pipe only requires X amount of water flow to be going through it before the pressure inside the pipe reaches 14psi. The 50mm pipe has a larger area to be filled and as such requires more flow before the pressure inside it also reaches 14psi. A turbo flows on the same principle. A larger turbo has a greater area inside that has to be pressurised before the internal pressure reaches 14psi, as such, more airflow is required to obtain the same pressure reading that you got with a smaller turbo. This is why when a friend of mine got his MR2 turbo rebuilt and hiflowed with T04 internals and bolted it back on, running 2-3psi less boost he saw a drastic increase in power. (not dyno proven, but you don't always need a dyno to tell you you've gained power - let's say he went from having to try to chirp 2nd on a gearchange, to having to try NOT to spin it) Hope this explanation helped mate

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)

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

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.

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.

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

I must be missing something, or I'm just too tired... (Though WTF can't I get to sleep tonight god damnit) I'm not meaning to be rude but I'm missing the comparison to a supercharger on my lil old RB20 here, sorry dude, please explain a bit better, I'm quite dumb tonight

It is a different kind of power though is it not? Even if it made the same power/torque at 2200rpm, the delivery is kinda different so the effect might not be the same? I honestly don't know, just throwin it out there

My engine is an RB20DET. 8.5:1 compression. If my current injectors can handle 10psi boost through the current turbo, why would I need to upgrade them? I understand boost is irrelevant and airflow is the real factor here. I know my injectors can handle 15psi or so through the turbo, do you think that the blower you're recommending would flow more CFM of air at 5psi than my stock turbo does at 15? What about my ECU, it being the turbo ECU would it be able to cope with boost from a supercharger as opposed to boost from a turbo? Is there any difference to what the ECU sees? Or does the ECU just take the AFM reading and apply the fuel accordingly? What I meant by disengaging the blower in neutral with its internal clutch was to prevent revving the engine when missing a gear change and causing potential damage by forcing boost into an engine that's not under load, aparantly that's a bad thing, I'm not sure why? Can you asnwer my question about the roots type vs lynsholm type blowers, or are you unsure like me lol? Does the blower your recommending use external compression or does it use internal compression, as explained Here. Sorry to be a pain, it's just that external compression as explained there doesn't sound that enticing to me. Also, do I -have- to remove my air con compressor? And what is a serpentine belt? Lol? Thanks again

Can I mount this type of blower in the same place in the inlet system as a turbo/centrifugal blower? For example; After the air filter/AFM then have it blowing through the intercooler and then into the throttle body? Obviously using a BOV to regulate closed throttle backpressure. What RPM range would it be efficient for? Would it make boost early and still last through to say, 6,000rpm? Preferably 6,500rpm. Can I setup the electronic clutch to disengage when the gearbox goes into neutral to prevent off-load boosting into the engine? How much would one of these blowers cost me? Where would I get one? What would be the cost of having it rebuilt once I've bought it (I don't wanna put things that are going to go broke on me quickly on the car if I can avoid it). Thanks again Ben. *EDIT* Lastly, you say it's a roots type blower? This means it's not a lynsholm-screw type and it works on external compression rather than internal compression. Isn't external compression extremely inefficient and doesn't in generate alot more heat than internal compression? Also what is a serpentine belt? What type of belt does a lynsholm screw type blower run, what does a centrifugal blower run? What's the difference between the 3?

Mate, any advice is good As I've said already, other peoples' experiences are my best source of information. I was looking at Vortech blowers and noted they were extremely pricey. I would be fine with an 8-9psi blower though, especially since it's going to be kicking in down low. I have a mate who is a metal fabricator, so if he's willing to give me a hand and has spare time at work (Which he does and I think he'd love to help, esp since he'll get to drive it lol) then I can probably get the metal stuff taken care of quite reasonably. What about my mounting point? I was thinking if I have to high mount it, then I can get a bonnet modification, like a bulge just over the supercharger, would look kinda awsome I think Also what about the belt to drive it? Do I need a custom balancer that has provision for a supercharger belt? Is there something I can strap it to on the standard balancer? Something else I haven't covered yet, ECU. The Stock RB20DET ECU, would it handle it? Could it be remapped to work, would an RB20DET powerFC be programmable for an application like this? Am I looking at a completely custom ECU? Once again, please keep the info coming people. Any experiences or knowledge is helpful. I've only been looking into this for a day now and already I know 100x what I knew yesterday. Cheers P.S: Don't be sorry if you're putting me off the idea. Original ideas are great, but you're correct, I don't wanna spend a bunch of cash and have a shitty engine in my car. If I get discouraged from the idea it will be because I honestly feel from the information I have gathered that it's not the right or viable option for me to pursue

Noones' 2c is useless mate. Experience is the best thing I can go off now. I think you're right too, the 4A-GZE blower isn't what I'm looking for. From what I'm reading here, I'm leaning towards a Vortech centrifugal blower, as I absolutely want an intercooler setup, which I aparantly can't have or can't have as easily or effectively with a screw type blower of either sort. Also aparantly they aren't as "laggy" as I've been led to believe thus far, which leaves them as a great option, they also look alot cooler than screw type blowers rofl In regards to 14psi being 14psi, I understand that airflow makes power not boost, as boost pressure isn't a constant, but is relative to other factors. Basically what I meant was, if you take a supercharger compressor and a turbocharger compressor that both flow the same CFM, then 14psi from the supercharger would be the same load on the internals of the engine as 14psi from the turbocharger, correct? I know this is alot of what ifs and buts, but I'm looking for a comparison so that I can assess how well the RB20DET motor is going to hold up to boost from a blower compared to a turbo. From what I can see now, the hardest part of this whole endeavour will be mounting the blower. Other than that, pipework, intercooler, BOV and intake setup will be basically the same as a turbo setup, assuming I'm using a centrifugal unit. So mounting right now is my biggest concern, after obviously getting the cash together to afford the blower and associated good bits Keep the input coming people, cheers. Ben.

That's what I needed, a kit for the RB twin cam series. I did a goodle on APS superchargers and found what I think is their site, but I couldn't find a link for the RB series kit. If you could link something that'd help a great deal. As for using a dynamic/centrifugal blower, as I said I've read that they bog down in the lower RPM. Obviously I don't have extensive knowlegde of this, so can you give me an idea of what I'm looking at? Vortech was my first thought for the blower as they're a very big, very reputable name, what model of Vortech blower am I looking at using? I 100% want to use an intercooler so I guess a lynsholm-type is out of the question, by what you're saying I can't intercool that setup? So questions are; 1) What model of Vortech blower am I looking at, I want boost to be efficient until at LEAST 5,500rpm, preferably 6,000-6,500rpm on my RB20DET (DET meaning the lower compression engine, not meaning I intend to retain the Turbo). 2) What RPM would a centrifugal unit begin to boost at? When it's not boosting, how bad is the engine going to bog down from the drain of the belt driven blower? 3) Is say 14psi from a centrifugal supercharger the same on the internals of an engine as 14psi from a turbocharger, just at a different range of rpm? Keep the answers coming guys, I'm loving the sound of this idea so far. And to whoever said it, yes, I think a blown RB20 would sound f**king unreal Ben.

I completely understand what you're saying. I've done a small amount of research on superchargers and what I've been able to find points to the fact that the best compressor for me to use for the RB20DET would be a positive displacement (screw type), but a lynsholm-type not a roots-type. The roots-type screw works on compressing air by, from what I can understand, using pressure forced back against the supercharger from the manifold, it's called external compression. The lynsholm-type screw works with internal compression, the air is actually compressed by the screws, I don't exactly understand how, all I know is it sounds like the type of charger I want. I looked at dynamic (centrifugal) chargers, but all the info I turned up (albeit only a small amount) says that they are quite sluggish down low, which defeats one of the purposes of this exercise for me. It really all depends, I want something that will boost early on, but I don't want it to be tapering off at 5,000rpm, I want it to be holding boost at least evenly, maybe not increasing, until 6,000-6,500rpm. I'm not sure if a lynsholm-screw type will continue to boost so that's something I need more info on, but I know that a centrifugal unit will not boost early on and will still be putting excessive load on the crank, therefor as far as I can tell, equating to a loss in low end power rather than a gain. Supercharging may not be for me at all, I might end up building a turbo engine, or I might end up giving up on a built engine at all, who knows. Just after info right now Keep it coming Ben.