Parallel and sequential turbo systems each have their own pros and cons. What you say put the turbos one right after another you are talking about a sequential twin turbo setup. Driving each turbo with exhaust from 2 cylinders is a parallel setup.

Cars like the Supra and RX7 both utilize sequential systems from the factory. Basically the idea is that you use a small turbo and a large turbo, one for low end boost and one for high end. The problem with a system like this is that switching off between the turbos is very difficult to impliment, just as it would be for twincharging. You would also be losing exhaust gas velocity for the 2nd (larger) turbo that would limit your top end potential.

For twin turbos on a DSM parallel is definitely the way to go. T-25s are plenty good for a TT setup. I don't remember the exact flow numbers offhand, but consider that the 14B flows 405 CFM. Lets assume the T-25 can flow 350 CFM. Two of them in parallel would be able to flow 700 CFM, which is more air than a Frank 3 puts out.

It isn't like you would be tryign to push more air through the engine with two turbos instead of one. Think of it as that you are making the same amount of boost but that each turbo is only working 1/2 as hard to make that. The T-25 is efficient up until about 18 psi. With 2 of them you would be only need them to push 9 psi each, which is well within their efficiency range.

Bottom line is that Doug's setup is probably pretty optimal for a TT setup on a DSM. So if you really want to do it copy his.

 

Thanks phacade that is a real good start. I'm glad you cleared the whole parallel or sequential thing up. I really want to know how much boost a 4g63 can take. If it where possible to throw 36 psi of boost at it would it last. My reasoning behind finding this out is exactly what you just said. If a t25 can make 18 psi of boost max then why set it up in a system that is only geared towards making 18psi total. I’d think you’d want 2 turbos that only make 9 psi of boost each for optimal spool up time. So if a 4g63 can take 36psi then I’d say t25’s are the best bet. But if not then does anyone know of a better turbo for this application. Right now I haven’t researched alternative, much less smaller, turbos enough to know (by alternative I mean turbos not traditionally used in dsm performance). So basically can some one throw me some rough estimates as to what our engines can take or maybe someone knows the engineered tolerance. Another thing to think about is manifold length (should they be equal length or possibly engineered like headers to create vacuum into the collector or something). Oh yeah, is there any concrete numbers on Doug’s setup? I’ve been waiting for him to update his site, but I got tired of waiting so I started this thread.

 

A 4G63 will not be able to run 36 psi unless you have a fully built motor. Even with that I think that much boost is unrealistic.

You have to realize that when people say a turbo can put out X amount of boost, it means that is the absolute max boost you can run where the turbo is actually making more power. When the T-25 is putting out 18 psi of boost, you are probably somewhere around 40-50% efficiency. That is not very good.

The T-25 is at or near it's peak efficiency around 9 psi. That is why it is a good turbo to use in a twin turbo application for a 4G63. At the track the most boost you will be running is around 25 psi with 110 octane which is 12.5 psi per turbo, still well within the efficiency of the T-25.

Headers are designed to be equal length because that is the most optimal for exhaust gas flow. So you are talking about the same thing.

I believe Doug has run 11's with his setup.

[Edited by Phacade GSX on 10-15-2001 at 01:34 AM]

 

I would say, two ball bearing t-28's. those would be just about right, eficant enough to push 15 psi per turbo, with out turning into hair dryers. the ball bearing centers should help, I haven't seen the the bb t-28 advertised for the dsm, but I have seen several supar owners talk about them.

 

Gross Conceptual Error here?

OK guys,

I think this may just be a terminology thing here, but are we saying that twin T-25's can flow as many CFM as a Frank 3? The first post was asking about max boost pressure you can run.

Now if we are agreeing that boost pressure don't mean crap and CFM is all that matters then I am with you about 90%.... not 100% because we would need to find out how much lower boost pressure effects the CFM flow of the IC piping, Intercooler, intake manifold, and head before we say that 9 psi on twin T-25's would equal the flow from 25 psi on a Frank 3.

Are we on the same page here? Anyone have data on how boost pressure effects flow rate in our extensive intake tract?

Later,

Keith

 

T-28s spool pretty damn fast already. Going ball bearing would be a waste of money.

Are you sure the Supra guys were talking about BB T-28s? Maybe you're getting it confused with a T-78 or T-88 cause a T-28 would be way too small of a turbo to run on a Supra, even on a pre-MKIV or MKIII.

 

Re: Gross Conceptual Error here?

OK guys,

I think this may just be a terminology thing here, but are we saying that twin T-25's can flow as many CFM as a Frank 3? The first post was asking about max boost pressure you can run.

Now if we are agreeing that boost pressure don't mean crap and CFM is all that matters then I am with you about 90%.... not 100% because we would need to find out how much lower boost pressure effects the CFM flow of the IC piping, Intercooler, intake manifold, and head before we say that 9 psi on twin T-25's would equal the flow from 25 psi on a Frank 3.

I was talking only about CFM. I don't think I said that 18 psi total boost from twin T-25's would equate to the same amount of air as 25 PSI from a Frank 3. If I gave you that impression then that wasn't what I was saying.

Lets assume that a T-25 at 9 psi is 75% efficient and a Frank 3 at 18 PSI is also 75% efficient. With two T-25s, you would be pushing exactly the same volume of air through the turbo(s) to the intercooler. The reason why 18 psi in a Frank 3 is better than say 18 psi in a 16G is because the 16G is not as efficient as the Frank 3 at that boost level, and thus the air density going to your intercooler is not as dense. If both turbos were equally as efficient at 18 psi, as is the case with the Frank 3 and dual T-25s, then you would be flowing the same amount of air at the same density from either setup.

 

Re: Re: Gross Conceptual Error here?

OK guys,

I think this may just be a terminology thing here, but are we saying that twin T-25's can flow as many CFM as a Frank 3? The first post was asking about max boost pressure you can run.

Now if we are agreeing that boost pressure don't mean crap and CFM is all that matters then I am with you about 90%.... not 100% because we would need to find out how much lower boost pressure effects the CFM flow of the IC piping, Intercooler, intake manifold, and head before we say that 9 psi on twin T-25's would equal the flow from 25 psi on a Frank 3.

I was talking only about CFM. I don't think I said that 18 psi total boost from twin T-25's would equate to the same amount of air as 25 PSI from a Frank 3. If I gave you that impression then that wasn't what I was saying.

Lets assume that a T-25 at 9 psi is 75% efficient and a Frank 3 at 18 PSI is also 75% efficient. With two T-25s, you would be pushing exactly the same volume of air through the turbo(s) to the intercooler. The reason why 18 psi in a Frank 3 is better than say 18 psi in a 16G is because the 16G is not as efficient as the Frank 3 at that boost level, and thus the air density going to your intercooler is not as dense. If both turbos were equally as efficient at 18 psi, as is the case with the Frank 3 and dual T-25s, then you would be flowing the same amount of air at the same density from either setup.

OK, I agree with you 100%. Some of the posts seemed to be saying that running twin T-25's at 9 psi each would give you a total boost pressure of 18 psi....that is wrong! Now twin T-25's running 9psi would give you more than double the CFM of a single T-25 running 18 psi due to the efficiency curves....but your boost gauge is still going to read 9 psi.

Glad we are on the same page

Keith

 

actualy, I saw twin ball bearing 28's advertised as a street up grade for the supra, when I was looking at buying one. not sure if it would be good, but he did say money didn't matter right, if so wouln't we want the turbo to spool up as fast as possable? I mean it would proably only get them to spool up like 150 rpms faster, but every little bit counts.

 

I think that 25 psi on race gas is a good goal (if I get crazier then that I’ll just get nos). I could be totally off base hear (I didn’t pay too much attention when my brother was building his Camaro v8, for obvious reasons), From what I remember we wanted to get uneven headers because they created a vacuum or something that let more exhaust get out faster by actually pulling the other chambers with the vacuum (equaling more hp), or something. I aint to sure on that one like I said I wasn’t paying attention and it could be the other way around. Please excuse my ignoramus on headers most of my car knowledge is dsm based and headers don’t matter so much as we all know. Also, four door, CFM is the main objective seeing as though it is directly related to horses (of the power variety) but it’s not gonna matter so much (I don’t think) once we get to the twin turbos because as phacade and I think you pointed out two t25’s or t28’s (someone should get some info on their peak efficiency so we can decide which would be best) flow a shiza load of cfm’s. As far as cfm’s go we should be more concerned with what you were saying earlier about low pressure intercooler piping and all. Oh, wait I just reread your last post and you lost the fuck out of me their. So are you saying that 9psi each on twin t25’s would be more cfm’s then a regular 18psi. I think I’m just over analyzing the statement, your probably right. Any ways, easy solution so what turbo would a twin t25 setup equate to (i.e. 20g, but better drivability, or maybe 16g, but more top end)? Also let’s stop assuming 18 psi and start going with 12.5 psi (I think) because I’m thinking this will be geared to produce 25psi of boost at it’s peak. All right so what length should the manifold/header contraption be I know if you make it longer it flows less cfm’s, but is quicker on the bottom end (and spool up), but I think we’d want them to be shorter (or stock length) to match the cfm rate we are going for (I don’t actually no what that is, if anyone wants to crunch numbers feel free). Another thought I had was what size exhaust should be hooked up to the turbos. In the end they should probably come into a 3” exhaust, but does that mean the two pipes going from the turbo to say the cat (for arguments sake) should be 1.5” that seems a bit small to me and I fear it will mess up the spooling time. Another solution is dual exhaust with an h pipe (besides that always looks cooler). I think I’m done writing. Also I’d like to go ahead and say that I am a more abstract thinker (in other words I leave out a lot of detail) so if I don’t throw in numbers it’s mainly cause I don’t know (so go ahead and put them in for me) or I assume you probably already know. I also think it pertinent to mention how I’d like this baby to drive. I’d want spool up to be close to stock if not better, and still get huge quarter mile times. I might have already mentioned that, but what eves. I’m done boring you, you probably have enough to write about for a week with all the mistakes I probably made in this post.

 

What the about the beloved 14b? Just thought id throw it in their beacuse its just above the t-25 but below the t-28, a nice median i believe.

Kevin

 

Twin 14B's might be a little laggy for the street. Remember you only have 2 cylinders to drive each one.

I think everyone wants a turbo with no lag and massive topend. Unfortunately you can't have both, even with twin turbos. Running dual T-25's or BB T-28s would probably net you pretty good spoolup time, but it will not be better than with a single T-25, simply because you don't have that much exhaust to spin the turbos.

If you designed a perfect parallel TT setup with the least amount of exhaust gas velocity lost between the head and the turbine you would likely get spoolup time equal to a Big 16G or maybe a TD05-20G. But your topend will be equal to that of a Frank 3.

 

Twin 14B's might be a little laggy for the street. Remember you only have 2 cylinders to drive each one.

I think everyone wants a turbo with no lag and massive topend. Unfortunately you can't have both, even with twin turbos. Running dual T-25's or BB T-28s would probably net you pretty good spoolup time, but it will not be better than with a single T-25, simply because you don't have that much exhaust to spin the turbos.

If you designed a perfect parallel TT setup with the least amount of exhaust gas velocity lost between the head and the turbine you would likely get spoolup time equal to a Big 16G or maybe a TD05-20G. But your topend will be equal to that of a Frank 3.

Yeah, to minimize lag you would need to go with an assemetrical sequential system. I would use a T-25 and Forced Performance "Red" for a sequential setup....but that would be much more complex to set up than a parallel system.

Later,

Keith

 

Okay so you want 18 PSI of manifold pressure, so a pressure ratio of 2.4 off the turbo(assuming you have a lot of intake piping and a front mount). And you want to rev lets say to 7000, if this is a road car. So your engine should be flowing about 512 gage CFM (32 lbs/min). Each turbo then needs to flow 16 lbs/min at p2/p1=2.4 peak. According to turbonetics a good compressor might be a 40 or 45 trim T3. Now to get this turbo spooled up correctly you'd need a small turbine housing. This is not such a problem since each turbo only causes backpressure to half of the exhaust flow. Hybrid T3/T2s would probably work well, if they make them. The advantages of dual turbo's lie in the fact that they have less rotational inertia and therefore are easier to spool. To capitalize on this ball bearings should be used (as mentioned above). All together a very streetable turbo setup could be used that would provide 65-72% efficient boost from about 4000 rpm to redline.

 

And keep in mind that with the exhaust, the crosssectional area of a 1.5" pipe is *much* less than half the area of a 3" pipe. -Mike

 

Because I'm the type who likes to throw some gas on the fire, I will. I've been thinking that a TT setup would be pretty sweet to fill in all that missing low end, and it would also make for a much more impressive launch without burning up the clutch and destroying the transmissions!

Since I'm really a motorcyle guy at heart (sorry but even drag only DSM's wont touch my bone stock ZX-12!) I remember reading a story about a guy who specializes in putting turbos on bikes. The details in the old gray matter are a little fuzzy, but the last project I saw of his in a Motorcyle rag was a Harley V-twin. This normally wouldn't be a good candidate for a turbo, but I think he was using these little IHI (maybe Air Research) turbos with a variable stator vane setup. The variable stator vanes allowed the setup to be free of a wastegate! The vanes would simply close off and let all the exhaust bypass the turbine! This helped give you boost from almost idle. I wanna say he was getting around 120hp or so from a 1340cc twin (stock is about 49). The tester described the engine as seemless without any hint of lag. And remember this is without an intercooler!

So it just occured to me, wouldn't it be really cool to use 4 of these little turbos? It would make constructing the exhaust manifolds a lot easier. One small section of bent pipe per cylinder leading into the turbine inlet. Might be a bit tricky to package all four in there, but if money is no object we could always find someone to lengthen the nose of your DSM (you already said you have a money tree at your house!). Downstream of the turbo's were left with a standard 4 into 1 collector, just like on any in-line 4 cylinder motorcycle.

While were at it, why not route the compressor outlet pipe's over top of the valve cover (after you've modified the hood to make them fit) and have them empty into a custom "log" style intake. You can do this since you don't have to worry about an intercooler! It also cuts out god only knows how many feet of the regular DSM IC piping. These pipes would need to be about 1.5" in diameter to flow the same as one 3" UICP. Of course, this means you would have to use a stand alone EFI system, so save a few thousand buck for that as well.

I'm thinking a setup like this would net you around 400hp, but have way better bottom end power than a car running a Frank 3 or similiar setup.

Let me know whast you think.

 

Ummmmmm

Because I'm the type who likes to throw some gas on the fire, I will. I've been thinking that a TT setup would be pretty sweet to fill in all that missing low end, and it would also make for a much more impressive launch without burning up the clutch and destroying the transmissions!

Since I'm really a motorcyle guy at heart (sorry but even drag only DSM's wont touch my bone stock ZX-12!) I remember reading a story about a guy who specializes in putting turbos on bikes. The details in the old gray matter are a little fuzzy, but the last project I saw of his in a Motorcyle rag was a Harley V-twin. This normally wouldn't be a good candidate for a turbo, but I think he was using these little IHI (maybe Air Research) turbos with a variable stator vane setup. The variable stator vanes allowed the setup to be free of a wastegate! The vanes would simply close off and let all the exhaust bypass the turbine! This helped give you boost from almost idle. I wanna say he was getting around 120hp or so from a 1340cc twin (stock is about 49). The tester described the engine as seemless without any hint of lag. And remember this is without an intercooler!

So it just occured to me, wouldn't it be really cool to use 4 of these little turbos? It would make constructing the exhaust manifolds a lot easier. One small section of bent pipe per cylinder leading into the turbine inlet. Might be a bit tricky to package all four in there, but if money is no object we could always find someone to lengthen the nose of your DSM (you already said you have a money tree at your house!). Downstream of the turbo's were left with a standard 4 into 1 collector, just like on any in-line 4 cylinder motorcycle.

While were at it, why not route the compressor outlet pipe's over top of the valve cover (after you've modified the hood to make them fit) and have them empty into a custom "log" style intake. You can do this since you don't have to worry about an intercooler! It also cuts out god only knows how many feet of the regular DSM IC piping. These pipes would need to be about 1.5" in diameter to flow the same as one 3" UICP. Of course, this means you would have to use a stand alone EFI system, so save a few thousand buck for that as well.

I'm thinking a setup like this would net you around 400hp, but have way better bottom end power than a car running a Frank 3 or similiar setup.

Let me know whast you think.

How small are these things? My other question is....why do you think you wouldn't need an intercooler with this setup? Other than those two concerns, it sounds like a pretty damn cool idea!

Keith

 

I am way into your idea, but I think some things need to be reworked a little bit. First off I just want to say that I don’t really have a money tree, I was being sarcastic. The idea is great especially the part about routing the intake over the valve cover into something I can only assume to be similar to an equal length plenum (I’ve wanted to make one of those for a dsm for awhile now). However I don’t really want to change the shape of the hood I mean it might end up looking cool, but will probably never end up looking like a dsm and obviously lose the sleeper aspect of the car. I don’t know that point is debatable if the system shows good potential. I still don’t understand why we don’t need an intercooler, well I kind of do, but that leads into my next point. This system is gonna make a dsm end up driving like a v8 with tons of bottom end and very little of the top end where our engine is most efficient. It’s gonna have descent power, but not insane power. Plus 400 hp is still very streetable on single turbo setups, part of the reason I wanted to go twin turbo was to at least break 600hp (I dream of 1000hp, but that’s not until magnetic bearing turbo’s come out) and still have a very streetable car. I think a quad turbo setup would have to much bottom end, and definitely not enough top end to justify the bottom end. I believe that a horse power decrease was found in separating the exhaust 4 ways at the manifold and that was why they ended up with twin scroll instead of quadruple scroll on the evo’s or something. I’m considering it more and more though even as I write this response. I just came up with stuff that might make the system produce more horse power. Give me a day or two to think about it and I’ll throw a more definite response.

 

Interesting.

Just to trow something out there, spoling a turbo has todo with inertia, the amount of force required to accelerte an object.

Much like the difference in acceleration btween 15 Volk wheels and chrome "dubz", the wheels in your turbo ract the same way.

Somehere on the web is a site listing all the wheel diameters of the popular turbos,if you crunch the numbers it only takes about 2/3 of the energy to accelerate two discs the diameter and weight of a 14b as compared to a Frank 5, which is rated at 800(?)CFM, while the two 14b's would be at also at 800 (810) actually.

Now, remember that this does not take into account the design of compressor and turine wheels, just the pwer to accelerate two discs equal in diameter and eight to their respective turbos

 

FourDoor,

The units are physicaly very small. I can't remember the exact details, but I want to say that they would be less than 1/2 the size of my 16G. They couldn't be very large and still fit on a motorcycle. There is another guy in florida who makes turbo kits for bikes. He's done a CB1100XX (a fully faired sport bike) and managed to fit everything in the fairing so it looks almost stock from the outside. If you know anything about sport bikes you now there isn't alot of room inside the fairing of a modern motorcycle. That particular installation is good for 225hp!

All of the companies that sell turbo kits for bikes sell them as bolt on kits. You do not need to change the pistons or anything else. The bikes run stock compression (11 to 12:1 for Jap/european and around 10:1 for Harleys) so you can't really turn up the boost. I think they usually run around 5-8psi, with a "crazy" setting of 11 or 12 psi. That brings me to the question of why I said no need for an intercooler. The idea of running twin (or quad) turbos is to increase the CFM, not the boost. Boost alone does not make power, CFM is the real power producer. So why not run 4 small turbos at a low boost pressure (like 5 or 8 psi) with enough CFM to make 400hp. I don't know what these turbos were originally designed for, but they probably are not very efficient at the higher boost levels DSM are known to run (i.e. above 12psi). However I do know they are efficient in the 5-8 psi range. The guy with the Harley conversion would have hand grenaded the engine if they heated up the charge very much. Remember that Harley engines are Air Cooled, have relatively high compression, and that the rear cylinder has terrible cooling air flow. This tells me that an intercooler would just add pressure losses and flow restriction. If you want to turn up the boost a little higher, I'd go with water injection to keep the knock at bay.

xHEROx,

I was being conservative when I said 400hp. If you want a DSM to make 600 hp, you'd better have a Money Tree! If you want 1000hp, what you'd have when your done probably wouldn't resemble a DSM in any way, shape, or form. I doubt buscher's RWD Talon even makes 1000hp. It certainly wouldn't be a sleeper! If you buy SCC (sport compact car), a recent issue had 4 400hp "street cars". They had 1 DSM (2G spyder with a Frank2)good for 390 some HP. The DSM was the only one of the 4 that had a full intake and exhaust system (including a cat)and was a true daily driver. The other cars made more horsepower but they weren't what I'd call "street" cars. They had a honda with a big garret on it to make 500hp, but they described the exhaust system as "what can only be a lightly modified sewer pipe"! I'm sure this thing would wake the dead if you drive by a cemetery. Definitely not a sleeper!

Besides if you could double the torque at low RPM, you'd have a much faster car for daily driving on the street. Torque is what really makes a car accelerate, not HP. IMO opinion, too many people obsess over HP, and pay no attention to torque. If Hp was so important, why couldn't I rig my ZX-12 motorcycle engine (160hp at the tire) in my 240SX. This is 40 more HP than my stock Nissan engine, but I'd bet it wouldn't even come close to what the stock 120 hp engine would do at the drag strip. In short the heavier the vehicle the more you should tune for Torque.

Tim

 

i have a friend that did a twin turbo set up on a dsm.He had alot of problems with it at firsthe used the turbo manifold from a twin turbo supra.He works at ATLTERED ATMOSPHERE (301)330-8835 his name is sean.if you call him I'm sure he would be glad to help you out.

 

I agree about the torque thing, I don’t think people consider the drive train enough either. I don’t know exactly how to describe what I’m looking for, I know it can be done, but it just takes some planning. I’ve considered a million things to make the perfect car, from putting together a solenoid based valve system so you could essentially change the valve timing (or cam lobe except there wouldn’t be a cam, it’s hard to explain, but makes a tone of sense, it’s kind of like vtec only infinite rather then three different cam lobes) to magnetic bearing turbos (which seem to be my favorite lately). Basically I want a street car that can be economical all day long then turn into a race car at the push of a button. That’s where I figured the twin turbo would help. This quad turbo sounds great, but I’m not very into street tuned cars. I’m more interested in race tuned cars that some how are still street legal. Any ways about quad turbo I thought of an idea, since as most of you have pointed out cfm’s are the big deal anyways not really hp I think the quad turbo is a better idea then twin turbo for the purposes of this conversation. I figure we could flow as much as a frank 5 or mutt 6 or 20g or whatever turbo you want to stick in there and have the thing spooled practically off the line. The water cooling is the perfect idea for this application to, especially since as you pointed out intercoolers would just mean pressure drop when the turbo puts out such low psi. In fact some web site I was looking at today makes a medium grade water injection kit just for turbo applications that flow less then 12 psi. It’s designed to work with a turbo system that has no intercoolers. Coincidence or fate? Since there is less rise in pressurization there will be less rise in temperature while putting out the same amount of cfm’s. okay now the only other thing I’m missing is how we are going to control the boost on this thing. You said something about a vain something or other. One other thing to pull from your guys’s plethora of knowledge, how many cfm’s could we shove down a 4g63’s throat? I pretty much asked this already, but I’d like a pretty solid number. Consider the drive train since there isn’t large aftermarket support on drive trains much less dsm drive trains. Also what kind of turbo was the guy running again? And I just finished planting another money tree so go fucking hog wild with this one. I’m gonna draw up a diagram of how I’m envisioning this thing I’ll scan it in and post it in the next few days I’ve got to go later.

 

xHEROx,

If what your after is vehicle that can blast down the strip in the high 9's then drive home from getting good gas mileage and also pass all noise and emmision regs, it's very simple really. Go to the bank and get a loan for about $12K. Then drive your self down the the local Kawasaki or Suzuki dealership. The things your looking for are called a ZX-12 or a GSX1300R Hayabusa. My Zx-12 goes from mild mannered commuter that gets 40mpg to a raging beast that will burn the strip up (low 10's or high 9's) and top out at over 185mph on the salt flats at the flick of my right wrist.

No need to worry about multi turbos, AWD systems breaking, and having to program a standalone EMS.

Tim

 

New variation

Hey guys,

What if we take one of these tinny little motorcycle turbo's and run it off of a single exhaust manifold runner and have the other three feed into a Forced Performance "Red" or a huge assed garret turbo? This is my assemetrical sequential idea mutated a little bit to reduce complexity...... think about it and let me know how you feel.

Keith

PS: Yeah, it would use a conventional FMIC

 

If what your after is vehicle that can blast down the strip in the high 9's then drive home from getting good gas mileage and also pass all noise and emmision regs, it's very simple really. Go to the bank and get a loan for about $12K. Then drive your self down the the local Kawasaki or Suzuki dealership. The things your looking for are called a ZX-12 or a GSX1300R Hayabusa. My Zx-12 goes from mild mannered commuter that gets 40mpg to a raging beast that will burn the strip up (low 10's or high 9's) and top out at over 185mph on the salt flats at the flick of my right wrist

I believe two things are pretty reasonable to assume-
1- we all know how fast sport bikes are. A co-worker of mine runs a low nine second quartr mile on his GSX-R, and commutes with it everday.

2- being that this is a DSM enthusiast site, most of us don't care that we could go faster on a bike, but it mostly only our DSM's that draws us to DSM enthusist site.

The water cooling is the perfect idea for this application to, especially since as you pointed out intercoolers would just mean pressure drop when the turbo puts out such low psi. In fact some web site I was looking at today makes a medium grade water injection kit just for turbo applications that flow less then 12 psi. It’s designed to work with a turbo system that has no intercoolers

I don't understand how the amount of boost matters to a WI kit?

What matters to a WI kit is that the air coming in is hot enough to turn the water into steam. To compensate for lower engine demands, kits come with smaler orifices to keep the motor from drowning.

If you want the end all to water injection kits, serch in the archives for Aquamist.

Also, post up your page so I can check it out, but I would be hard pressd to believe there is anything better than RL's Aquamist System.

Boost alone does not make power, CFM is the real power producer. So why not run 4 small turbos at a low boost pressure (like 5 or 8 psi) with enough CFM to make 400hp. I don't know what these turbos were originally designed for, but they probably are not very efficient at the higher boost levels DSM are known to run (i.e. above 12psi).

I think you guys are a little confused on the bost/cfm relationship.

A 2.0 motor running at 100% VE (this is for simplicity) needs roughly 210CFM at 6000rpm. Now, to gain positive manifold pressure, you need to flow more than this.

So, if you want to get fifteen pounds of boost, you must force 420cfm of air into the motor. It does not matter how many turbos you run, as long as there is a common plenum, the two compressors will create the ffteen pound of boost to reach tis lvel of CFM at this rpm.

You cannot run 5 to 8psi and make 400hp on a DSM. That would be less total CFM than a stock DSM. Boost set at that level woul be adding 100cfm to your motor, which is fine I guess if you are a honda owner, but it no where near 400hp.
Being 100% realistic, its well below 190hp.

Where the confusion may come in, is the fact that by using two smaller compressors as opposed to on lage on of equal airflow, is that the small ones will only have to spin half as fast as the one larger one.

The advantage is that the smaller turbos will spool (accelerate) faster than the one large wheel, its not that you get to run less boost ad get more CFM.

Not to be insulting, but, I really wish some of the more exprienced (and hardheaded) users would get onto this one

I really recommend "Turbochargers" by Hugh McIannes, just quick read through wuld answer a lot of your guys questions.