Can I supercharge a 240, I think I can.

[Chezedik]

I would like to know: I have been inside the KA, and despite the pressure die cast pistons, the bottom end of a KA is extraordinarily well built. But I am concerned about the fuel system. I know the injectors are at 237cc/min, which is about enough to support 190HP (roughly) at an 85% duty cycle. With a pressure regulator at 60PSI above manifold vs. 43psi, you end up with about 330cc/min, if I did my math correctly. Which as we all know is about as much as you can expect the welds on a stock fuel rail to hold consistantly, without bursting. This on a stock motor with stock programming will effectively lower the duty cycle to a max of 85% (safely w/o bind) at about 281cc/min. (Now that I have rambled for a moment) What amount of boost can I safely expect for 280cc. I know that a stock SR runs about 7psi on 330cc, but of course, they allow for a margin of error and modification, which produces a reported 205HP (170HP dyno proven on a dynojet in california). Can I safely run 5 psi on a stock block 240 with that amount of enrichment. I think I have solved the supercharged 240sx issue, and when I have completed the project, I intend to market the kit (nothing but the adapters, so as to make a few $, and make it an affordable and fun alternative to turbo). Let me have any input you can.

Following are the required air requirements in CFM for the KA, assuming 141 CI of displacement:

1K RPM 40.79 CFM2K RPM 81.59 CFM3K RPM 122.39 CFM4K RPM 163.16 CFM5K RPM 203.95 CFM 6K RPM 244.74 CFM 7K RPM 285.53 CFM

At a 2:1 ratio of drive to a KA the M62 eaton supercharger will max at 440CFM at 14000RPM supercharger speed, which will require about 28HP to turn, and will stay inside of the capability of the supercharger, without overdriving it, and hitting 120F of delta temp. All of this said, if I can work out the mechanical limitations, which I believe that I can, I want to know if I can make this work. I am still not proficient enough in thermo-dynamics to understand if the engine will be able to consume that much more air than it normally would in stock trim. If anyone has any ideas, I would love as much input as possible, and if I have to lower the ratio, and you think it might help, let me know.

[crzycav86]

Stock ka injectors are 270cc/min, sr injectors are 370cc.

You could probably run 5 psi on the stock injectors. KA-T guys do it all the time(but their intake temps are higher). With an fmu, you could solve the fuel issue. A good stock block can take over 300 hp, so you won't have to get new internals yet...

I suggest you ask some people in the ka-t forum.

[Chezedik]

I am sorry, but glad to know. I thought I heard someone tell me 235, but good to know. How does an FMU differ from a fuel pressure regulator. I know they are rated by ratio, but how will that be safer than adjusting my press reg with the stoichiometer that I have. Also, like I say, I think I have the mechanical aspect solved, but I need to know in terms of CFM how boost could be derived, so I can try and do this safely the first time. I think that the 2:1 drive ratio may be a bit much. But maybe in the 2.5:1 or 3:1 could work. Basically, I think I can do this, and what I need is for anyone with an idea, to tell me why I can't. But I do appreciate the info on boost capacity as it relates to the stock injectors, and I will be searching the other posts for more info.

[Zydeco]

I didnt know superchargers took some hp to turn.

[DAEDALUS]

Yeah, just like any other belt-drdiven accessory.

[Chezedik]

Yes, but as superchargers go an eaton blower has a pretty high adiabatic efficiency rate, plus the low end will be good. I think the KA's lack of power above 5.5K should be celebrated with a supercharger, (or a good NA build(yes, I do know)) rather than trying to change the natural properties of a well built high displacement 4 cyl.. I work at a parts store, and when all the V8 guys come in, I like to tell them that I own a big block Hemi. Then I tell them to prove me wrong. Sorry, off the point, I need you guys to tell me why I can't do this. By the way, for a good read, check out cav's post on hacking the S13 MAF. When I hear the results (if good), I intend to try it. I think it a better idea than paying for a chip, besides the obvious reason, I want to maintain stock (or even slightly retarded) ignition timing. NOW SOMEONE TELL ME WHY I CANNOT SUPERCHARGE MY CAR, IF I AM WILLING TO TAKE THE TIME. (sorry for yelling).

[bcar240]

I think it is more due to what is "customary," for lack of a better word. It seems that usually superchargers are used on higher-displacement engines and turbos on smaller "tuner" motors. I know there are plenty of exceptions though. The small motors have less horsepower at tap in stock form, and the "lose ## HP to turn supercharger" has more of an effect than a turbo would. Small engines tend to rely more on high-tech parts and tuning to make power, and a supercharger is not as easily tuned as a turbo. This being said, I believe you could get away with it and have great results supercharging a KA. IIRC, it has been sucessfully done before at least once. If I were you, I would make replacing the injectors/fuel pump and maybe the fuel rail as one of my first priorities after getting it installed. Seems like you have done your research, if you think you can get it hooked up and working I would say go for it.

edit: just to let you know, I don't have much experience with superchargers, so take this more of a "theoretically possible" discussion.
Modified by bcar240 at 4:35 AM 1/30/2005

[madbouncy]

http://www.nicoclub.com/zerothread?id=95732

Ubernoober said some stuff about superchargers in that thread, I can't remember exactly which supercharger he said you should look for but it's in there. There's nothing stopping you from putting a super on your car other than you'll have to have everything custom made opposed to just ordering up the parts for cheap. It's easier and cheaper to turbo the KA and most people want to give the KA a better highend. If you can fab the parts up yourself, it's not really going to be more expensive, but if you want to have a shop do it, it will be. Good luck with it though, definitly keep us posted if you start anything.

[Chezedik]

That is a hell of a thread with a lot of misinfo, but it did have one thing I wanted, which was a formula for computing boost based on total flow. That will help me to compute my ideal pulley size.

[masticatingcow]

Yes, but as superchargers go an eaton blower has a pretty high adiabatic efficiency rate, plus the low end will be good.

I'm pretty sure the Eaton roots blower has the LOWEST adiabatic efficiency of common superchargers.

I'm quoting from SCC's March '05 issue, page 126. The article is called, "Suck, Squish, Bang, Blow."

"Roots blowers also have the lowest adiabatic efficiency of the commonly available superchargers. This means they blow hotter and suck more power from the crank than other types of blowers. Having good adiabatic efficiency is important to the tuner because with higher efficiency comes a cooler and denser intake charge. A high efficiency blower will also steal less power from the crank at any given boost level."

Of course, every forced induction setup has its pro's and con's, but I just wanted to clear that up. Yes, the low end will be good, but it's not the "pretty highly" efficient setup you might think it is.

[Chezedik]

Yes, this is in regards to roots blowers, not eaton superchargers. If you read further into said article you will find that they mention this. Further they go on to include that because of the eatons curved rotors vs. the straight rotors used in roots units, and because of the bypass unit used with them, they exhibit a better adiabatic efficiency than the roots blower. When this is compared to the higher heat output of the centifugal style and rotrex/pro-charger style centrifugal clones, the eaton comes out as a clear winner in the department of adiabatic efficiency. Although, it is not as volumetrically efficient in the lower RPMs as these other units. Sorry, but your quote is incorrect.

[Chezedik]

To further compound this as well, the deeper cause for the roots blowers lower efficiency is because it is not a supercharger in the true sense. It is a blower. Where as one just moves air like a fan, the other actually compresses it. The roots is riddled with inefficiencys, and although it is characterized with the eaton (just based on physical similarities), they are two very different beasts. Like I say, follow that article a little further and they will back me up on what I have just said.

[masticatingcow]

Are you telling me that the Eaton roots blower is not a supercharger? If that's the case, do you think the SCC staff is doing its readership a disservice in discussing the Eaton unit in an article subtitled as, "Know your supwerchargers?"

Regardless, the article suggests that the Eaton unit is an improvement on old-school roots blowers, but nowhere does it say that the Eaton is more efficient than, say, a centrifugal supercharger. While you may very well be right in that the Eaton unit exhibits a higher adiabatic efficiency than most other superchargers, it seems kind of dumb that, after equating roots blowers and the Eaton name, Kojima would state the exact opposite. I'm not calling you out, so don't get all flustered. All I'm really trying to say is that I've found (in fairly reliable places) concepts contrary to your statement.

So, if the Eaton roots-type blower is NOT a supercharger, can you explain what the Eaton supercharger is? Because, damn, for the longest time, I've always used "supercharger" and "blower" interchangably. Oops.

[masticatingcow]

But anyway, I noticed that you asked in CAPTIAL LETTERS quite some time ago for someone to tell you why you could supercharge your 240sx.

Um, the answer to that is, well, yes you can. Good luck with it and keep us posted.

[Chezedik]

No, what I am saying is that the roots and the eaton are not terms that can be used interchangably. They are not produced by the same group, and they are designed differently. So, yes the roots is a blower, and the eaton is a supercharger. However, it is not necessarily wrong that you use the two terms interchangably. You see, as stated in the article you quoted, the roots blower is typical of designs like the wieand x71 series, and so as a matter of convention a blower and supercharger are termed the same. I wouldn't worry about it, only a nerd as bad as I would call you out on it in conversation. I will keep you posted. And I came up with another idea for intercooling it for air-water-air, but that will be later in the project.

[The Mic]

You can just about any supercharger into your car as long as it is made to turn in the same direction as your engine's pulley. Screw type and Roots type superchargers would not fit very well though, as these force air directly into the intake mainfold. A centrifugal supercharger would probably be the best way to go. As far as I can tell, it may be the only way. A centrifugal supercharger is basically a turbo driven by a belt rather than an exhaust turbine. The thermal efficiency of a centrifugal supercharger is slightly less than that of a turbo. But the supercharger has much better response(no lag!) and can offer boost just off idle. This is because superchargers generally have linear boost curves. Boost is controlled by the size of the pulley, larger pulleys giving lower boost levels, and small pulleys giving higher boost levels. The 240sx can probably handle about 5 psi of boost without a lot of tuning. 7 psi might be attainable with some really diligent tuning. As far as fitment of a supercharger in a 240sx, it may be a little tricky, unless you have no air conditioning.

Vortech, Paxton and Powerdyne are probably the most reputable names in centrifugal supercharging. Vortech and Paxton have similarly designed superchargers and are internally gear driven. They have a slightly better thermal efficiency level than the Powerdyne unit. However, Powerdyne is internally belt driven(it uses a belt similar to a timing belt) and does not require oil lines to be installed for lubrication. It is also much quieter than gear driven models.

[j-z]

yes, you can supercharge your car. i dont know why youre choosing to go with the roots type setup though. a centrifugal setup would be way more ideal to use. i was seriously so close to running one on my 240, but i got caught up in running auto-x and forced induction is something i choose to stay away from. later down the road, if i do happen to change my mind and go forced induction, i will be going with a centrifugal unit. for fuel delivery in your situation, i would use a inline fuel pump and a FMU (im selling both of these if youre interested). welds breaking on a fuel rail.... ive never ever heard of that. also, you were wondering how much more air the engine could consume in stock form... it will consume what ever you throw at it because it is forced induction, or maybe you were wondering about how much more it could consume in stock form safely... tell us your reason why you choose a roots type blower over a centrifugal unit.

[Chezedik]

I actually will not be using a roots, I will be using an Eaton. That is just what I have been told about the fuel rail, but I will be trying cav's idea for hacking the s13 MAF. That is not what I mean, about consuming air. What I mean is this I guess: How many excess CFM will equate to a pound of boost? I understand the question was worded stupidly, and I hope that you know what I mean. But my question is what exactly constitutes boost in a scientific sense. I know it is manifold pressure above 14.7, but is there any good way to equate boost to volume of air? I chose an eaton because of it's propensity to increase fuel mileage at partial throttle, for the fact that it has a bypass, it's air charge will be cooler, which means more boost on stock internals, w/o having to worry about detonation. It is also a blower with a lower curve for boost, meaning it does not have to spool up as long as a centifugal blower. And yes, superchargers do have to spool up, just like a turbo, they have to spool up in order to begin to build positive manifold pressure. So I think that although the horsepower numbers may not be as high as they might be with a centrifugal, they will be more streetable. If I wanted a turbo, I would pick one of the turbo kits available for the KA.

[hamsturbation]

an eaton might not be the best choice...for one, if you read that article about the eaton further...that bypass lets HOT air though the supercharger into the intlet track, creating heat soak in the intake manifold..not good

"The thermal efficiency of a centrifugal supercharger is slightly less than that of a turbo. But the supercharger has much better response(no lag!) and can offer boost just off idle."

you sure its LESS? i think its HIGHER than a turbo, seeing how its not attached to a hot *** exaust manifold

centrifugal superchargers are not known for producing low end power either...

and a "roots type" supercharger and a roots blower isnt the samea ROOTS blower does not compress air, a "roots type" such as an eaton blower DOES

[j-z]

the reason for a turbo being more effecient than a centrifugal supercharger is that it doesnt take any of the motors energy to make additional power. a super charger does because it is belt driven and creates drag and takes away some power from the motor to make additional power.

[Ubernoober]

Gawd!The amount of misinformation in here is stunning. I don't know where to begin so I will just ignore this thread for the good of my mental health.

BTW, do a search. There is much more accurate and useable information in other threads.

[Chezedik]

That in and of itself is not what makes it more efficient. Because ham is right about the high heat, and to a small effect you are right about not using belts. Turbos are not always as efficient, that is where they get the reputation for nasty lag, when in truth, most modern turbo setups (with the exception of very large turbos) do not have big problems with spool-up. This is simply more people spent more time developing more combinations of turbine/compressor, such as t3/t4 or disco potato. Ham, I could be wrong, but I believe the crux of that statement was based on the bypass being mounted directly to the charger, on the chargers exhaust. This in effect, traps air in the charger where it will recirculate, and try to compress compressed air. What I intend to do is use Eaton's optional remote bypass and mount it before the inlet of the manifold on a large butterfly, to some sort of blowoff, or maybe the HKS recirc valve. Or maybe I will leave it alone. I must decide where the tradeoff is worth it in power to ease or reliability. I am looking at hacking the MAF and turning up reg press so I get some top feed 330ccs or 370cc injectors, and pulling roughly 400cc and 10lbs. I have been told the bottom end of a KA will do it so long as timing is backed off, and there is plenty of fuel. Long story short, prevention of detonation. The KA is plenty strong, the weak point is the pistons. This is due to Nissan's method of die-pressure casting them. By casting them and forcing material in you end up with more casting faults. It is a strong piston, so long as it is not expected to go above and beyond, it does fine. But many KA-t guys have seen a lot more than 10lbs on them, it is just using proper fuel and timing control. We have two methods on our new manifold: first is we will rifle the runners to better atomize fuel and insure proper combustion, the second is an air to water to air cooler, which will also sit in the manifold and cool the exhaust air from the charger. What do you guys think would be a reasonable expectation for power. I would not mind mid-200s, with all the bolt ons as well. Someone let me know what they think. Also, I posted this thread because I wanted you guys to criticize my idea. The idea being that if you guys help me find the holes in the plan, I will save mistakes in the tuning process.

[Chezedik]

Oh, and constructive criticism only please.

[hbrown]

Yes you can do this. I think it will work well. You may need to look a little closer on the idea of jacking the fuel pressure way up to get the required volume - I dunno about the Nissan injectors- but there is a maximum pressure that most injectors can typically operate against without having problems. The fuel rail welds should not be a problem. Just get bigger injectors with the right flow numbers.

The Eaton unit is classified as a roots type supercharger. Any supercharger that has a longitudinal casing enclosing a pair of timed multi-lobed rotors is a "roots" type unit. The Eaton is different only in the fact that it has the bypass valving and the rotors are of a helical design. It is not a "screw type" compressor like the Lysholm. It does have a high efficiency rating when compared to most roots type designs. It is considered by the engineering community to be a very highly engineered unit that performs well.

The difference in this type of supercharger and the cetrifugal is best described by the type of air delivery- roots types are positive volume displacement- they move a quantity "x" of air per revolution no matter what they are up against where as a cetrifugal unit builds pressure using high velocity impingement on the impeller. A roots type is a "pump" and will build boost pressure immediately- a centrifugal is a "fan"- although an efficient one- and has some 'slip' to it. A centrifugal supercharger basically 'freewheels' until you drive the revs up hard enough to where it is in it's design rpm- at which time it builds boost. The Eaton has the bypass system which lets it practically freewheel the same way until you get on the throttle- at which point the bypass is closed off and full pressure is developed to the manifold. The Eaton is designed for building low end and midrange torque- and will suit the KA very well I think. The Eaton can be spun up around 14,000 RPM and is usually driven somewhere around a two to one ratio- so that is about right also. You can expect about 9-10 psi max boost out of one.

There is no doubt it will work- and work well. There just seems to be a real unwillingness for the "Tuners" to embrace the supercharging technology- which has really come a long way in the last 10 years. They are a much more streetable setup than a turbo- and they give what a smaller engine needs most- torque. 2 or 3 years ago you could get an Eaton from a junkyard for $200 or so- try to get one for that now. They are slowly catching on- and the newest ones are much better than even the ones from a few years ago. If you can get the fuel map worked out and cram an intercooler on it also- you will have a good workable system. H.

[Chezedik]

Any other replies, any and all info would be helpful.

[hbrown]

Jackson Racing can probably help you out- they may even have a kit for 240's by now- they use Eatons.

I have been toying with the idea of putting together a belt driven set-up using the compressor side of a large turbocharger- only obstacle is getting the drive belts to have a high enough ratio to spin the charger hard enough to do any good. It has been done before- and it will workif you can sort out the belting.

[Fester]

What I mean is this I guess: How many excess CFM will equate to a pound of boost? I understand the question was worded stupidly, and I hope that you know what I mean. But my question is what exactly constitutes boost in a scientific sense. I know it is manifold pressure above 14.7, but is there any good way to equate boost to volume of air?

Don't think of the air you're pumping (or sucking) in as a volumetric measurement, think of it as a mass measurement. At least one interpretation of MAF is Mass Air Flow....

Now lemme see if I can remember some high school chemistry

1 mole of gas at 1 atmosphere and 20 (?) degrees C occupies 23.5 (?) litres, or about 0.83 cubic feet.1 mole of a 21% O2 mix (i.e. good clean air, please convince George to sign the Kyoto protocol so we can all make more horsepower ) will contain a mass of 16 * 2 * 0.21 = 6.72g of oxygen.From your first post, at 6000rpm and 20 degrees C inlet temp (not too likely...), the engine will consume 244.74 / 0.83 * 6.72 = 1982g of oxygen per minute. Be generous, call it 2kg.

The mass of oxygen consumed will be (reasonably) linear with both pressure and temperature. Don't forget that the zero point for temperature is zero Kelvin, not zero Celcius. Zero Celcius is about 273.2K. For example, at 40C, 1 atmosphere and 21%, 244.74 cubic feet of air will contain a mass of 1982 * (273.2 + 20) / (273.2 + 40) = 1855g of oxygen.

[Camel]

Guys, this is such an old conversation. Don't post again until you ACTUALLY have a supercharger to install. All people ever do with this is talk. I haven't seen one example of it being done with a KA yet.

[j-z]

Guys, this is such an old conversation. Don't post again until you ACTUALLY have a supercharger to install. All people ever do with this is talk. I haven't seen one example of it being done with a KA yet.

.whats up your ***? this is a discussion forum where people talk about a specific topic. now, about you havent seen one exmaple... go look in the ka forum. youll see where a guy successfully supercharged a kade in a hardbody.

[Chezedik]

Yes, that was a good post, and by the way he showed us it could be done. However, his only real mistake that I saw was using an m42 instead of an m62, and he found that after about 3000 rpm it would fall flat, because the displacement of the charger far too low to support the engine and still boost. But to the best of my understanding, he did not continue. If I recall, I even offered to buy the manifolds to do my own testing, but never got a good response. Oh, and by the way, we already have our manifolds designed, and when we can scrape up the funding to come up with a blower, we will be installing it on my personal vehicle. I am just asking for opinions and formulas to come up with the right pulley ratio and to decide if I should use a thicker head gasket, which I do believe I have decided to do. I have a machinist friend who will be producing those at a .60" thickness, which I believe will allow me to use a full 10lbs of boost on stock timing, or even slightly retarded timing, with pump gas. Also, I would like to know if anyone has heard about a transmission swap from the T5 clone we use to a T7, I have a friend who has three spare t7s, and we intend to remove the bell housing and tail shaft housing from the T5. The tail housing does the measurments for the speedo, and there are three other sensors in the body of the trans, I need to look into my FSM to find out exactly how important they are to operation. I intend to use the t7 (7 speed)with the Nismo 4.636 R&P and I calculated (using the C&D time of 16 flat) a 14.02 1/4 time. The same machinist friend has begun production on an aluminum flywheel that will be superior to the Fidanza unit. It allows for the bolting points of the metal insert to run through the back of unit, so you will not have to worry about shearing the bolts off when you really rape the flywheel with a metallic clutch facing. We really are trying to come up with some revolutionary ideas. Anyway, if anybody is interested in any of these ideas, please let me know. We are trying to figure out if we should continue in production. I will definately be following through on my end just for the fun of it.