Finally, thanks to BlueTII on the forum, I got my hands on a lysholm type twin-screw supercharger for an upcoming project. It is the oem unit from the Millenia S miller cycle engine, and its rotors look just like the ones in my avatar. It is huge, like 20" long and 8" wide and about 35 pounds, lol. Man it's going to sound cool on the FC, the rotors spin at about 4x the speed of the input serpentine pulley and it moves a bit of air . .



It's time to start fabbing.

 

 

Sweet!!!!!

 

I'm confused, where does the turbo go in this setup???

 

this is a supercharger not a turbocharger

 

cool, can't wait to see how you do it.

 

I know that, it's more of an inside joke between me and anyone that supports superchargers that I talk to regularly. I'm not a big fan of them. It will be interesting to see how he does with it though.

 

I don't know Jeff, are you sure you want to add the weight.

Remember in your engineering mind, superchargers are less efficient than turbos and someone already engineered a great turbo setup for a 2nd gen, they were called Mazda.

Seriously, bring it out and show us what you've done. Your work has looked pretty good so far!

 

I'm sorry but I wouldn't call the series 4 turbo a turbo setup with great engineering backing it.

 

congrats man

 

Thats right Zjbarra....amazing that we get a long so well huh. Since Turbos suck and superchargers rock....lol. You being the turbo fan, and I being the supercharger fan. But I still like you anyway.

CONGRADS on the Supercharger...woooo hoooo need more. WTG 88IntegraLS.

 

Wow, thanks for the support, adding a supercharger has been a big pipe dream of mine for a while. Blue TII, who has one of the most unique TII's I've ever seen, has given me a lot of help. He was considering using this supercharger on an FC for a long time, but stuck with turbo.

 

Why not? they made 180hp stock on 1.3 liters and most engine/turbo lasted for 130k + thats double what most fd's go for.

CJG

 

i'm just a boost fan i think it would be an awsome setup on your car hope to see it but i couldn't care about the turbo vs super thing they are both awsome but supers on rex's i here can't produse as much power but you get more off the line so whatever

 

Do you still remember where those Whipple pics are if you need to see them for inspiration?

 

ha ha, yes I still have them, but it's more inspiring to play with a real twin screw charger than to look at pix of them!

In my engineering mind, superchargers are a better approach for an enthusiast who desires instant throttle response much like if one were to install an NA 20b in an FC . .

Turbos create backpressure and have manifolds that don't flow as well as properly tuned headers, though superchargers take energy from the crankshaft. It's all a matter of what type of compressor u choose for the supercharger when ur trying to determine what efficiency u want.

Centrifugals are the cold section of a turbo, basically a gear and belt driven turbo compressor. Roots blowers are simply fast moving air pumps, and lysholm type (screw type) superchargers are true compressors with the same positive displacement nature of roots but with efficiency that approaches centrifugals, which are the most efficient (from an energy required for a given psi, and heat added for given psi standpoint).

Centrifugals are used on V8's mostly because those engines have plenty of low end torque but don't have a flat torque curve, so the exponential boost curve don't matter much (little boost until 2/3 the way up the rev range). Roots are great for giving low end torque by creating full boost at like 1/3 the rev range and holding it to redline . . although roots type blowers heat up the air more than a centrifugal compressor . .

Enter the lysholm type supercharger . . this type has efficiency approaching centrifugal with early and constant boost like a roots . . the best of both worlds basically. U can use a real fmic like a turbo, unlike roots which are better off with an air/water aftercooler which wouldn't cool as well as a true air/air intercooler.

So there, that's what I know in a nutshell about efficiency of superchargers . . they have a bad rep for efficiency because the old weiand 6-71 or like type are straight rotored roots type with teflon strips that rub the rotors and create heat . . this old school type is much like current day camdens and is good for creating boost early in the rev range, but not as efficient as a turbo compressor. However, lysholm type superchargers do not suffer from this inefficiency as much as roots type for a few reasons which I won't go into here.

Summary: In my engineering mind (turbojeff), I chose a lysholm supercharger because I want my fast car to sound supercharged (loud and not turbo), feel superchargered (mash the gas and instant power), and not have boost controllers, or a compressor bolted to the hottest part of the engine. 88IntegraLS says: my setup will probably not equal the efficiency of a turbo, but it will smoke traditional non aftercooled roots blown setups running similar boost. I only want 5-8 psi and 250 at the rear wheels (for now . .)

 

So 88 do you have any ideas of using a intercooler set-up similar to Ian's? Or are you just going to stick with a front mount.

Man I feel like I am going to be the only one left looking for real performance with my N/A set-up. I hate you man

 

So are you planning on doing some porting also, I think your goal of 250, should be within grasp with that amount of boost, but i think your going to need a good sized street port. Also, what are your goals for tourqe? So far the torque that has been produced by the camdens has not been very impressive. What are your thoughts on this?

CJG

 

The engine already has porting. As na, the car recently ran 14.78@95.6 . . that's mildly modded tII territory.

But yes, I am about to inflict some later port closing timing and larger runner size on this engine before it gets boosted . . ahahahaha, what a life.

*edit* the subject of torque . . the engine has a good bit of NA torque now, and with 8-10 psi arriving at 2k rpm or less the instant the gas is floored, I'm not too concerned about doing wilder ports than I have already, but I don't want this thing to feel quite like a V8, more like an NA 20B with a streetport similar to what I've already got on the S4 13B NA . . u know, flat torque curve from 2500 rpm all the way up to redline . . I'm guessing I won't see more than 200 ft-lbs, but if the car runs 12's, I'll be wearing a smile anyhow. Holding torque to redline makes a big difference compared to NA V8's that haven't been modded, which have their torque fall off about halfway up the rev range . . and flat torque is so nice to drive, just feels good, predictable, real rotary feeling torque, but more of it than an NA would have. Kind of like the stock FD twins, that's what I'm after, that kind of feeling.

 

I'm not saying superchargers don't have an application.

The problem with them is that they take belt driven hp from the engine to provide boost, parasitic losses basically. Unless you fab up a cool bypass and a clutch it runs all the time, which is another negative in the efficiency column.

A turbo on the other hand uses waste heat from the engine to produce boost. In the process it does create some additional pumping losses but in the end they end up with a positive sign for using waste energy and making power with it.

Also turbos don't really effect mileage off boost. There isn't really enough exhaust/waste heat for them to make any boost at a cruise (properly sized turbo). A TII and FD both get in the low/mid 20mpg on the highway, even modded. The best I ever got in an NA over a 1000 mile trip was 26mpg.

Superchargers are cool and the benefit to you in this entire project is that your going to learn a lot. You can put it on a resume' and talk about it at an interview. No kidding, I'm 100% serious. When I interview an engineer I like to hear what he's done and what he learned from it. Anyone that says they haven't ever made a mistake either hasn't done anything or they are lying.

I'm pretty sure you won't come close to 250rwhp at 5-8 psi. If I had to guess you'll get in the 160-180rwhp range, which is not bad for a 2300-2400lb car at all.

Jeff

 

Another thing...

I'm not an expert on porting to say the least but the more overlap you have the more boost will go out the exhaust port right? Porting boosted engines is different than NA IIRC.

 

I think all forced induction is cool. I still think the instant power argument is over used because a turbo is full boost by 4000 rpm's. So what kind of performance driving do you do at low rpm anyways since peak HP is at 6000 rpm?

 

With overlap you will lose a bit of the mixture but you are still going to maintain pressure. I think you would just have to time your fuel extremely well so you don't lose it durring the overlap.

 

Yes, most turbo ports I've seen have mostly later closing and not much overlap, and that is how mine is already ported, and how I will extend port it this weekend. Although, turbo bridgeports have been done and usually match the power of a normal low overlap street port turbo at about 3k rpm, then the turbo bridge exceeds the street port with a big margin, but it also has a larger turbo usually.

8 psi is .5 bar, or 1.5 atmosphere. If my engine is making ~150 rwhp at .9 atu, multiplying 150 by 1.5/.9 and then multiplying again by .8 to cover belt losses and intake air temp rise gives 200 rwhp, although the compression ratio rises under boost which elevates overall efficiency somewhat . .

Bypassed superchargers steal a few hp when cruising on the highway in bypass mode (of course I'm planning on bypassing this), but that's not worth a tenth of a mpg.

I've said it before and will say it again: Turbos create more backpressure on the exhaust than the boost psi they create, and that steals horsepower just like belt losses of superchargers . .

It would be much easier to sell this car, buy a TII, and do the standard mods to max out the stock turbo to get 250 rwhp, but I'm doing this for practice for future goals, and yes it's nice to mention that I can fab and calculate stuff and put it to use when talking to other engineers. I can't believe how many engineers I know from just experimenting with this car, it's insane! Off the top of my head there are 4 guys I know who have engineering degrees and are gainfully employed, and rotorheads like me.

Oooooo I wish this was done right now so I could get it on a dyno and prove my points . . or be wrong, ha ha. I heard the skeptics in the second gen section put down my idea of ram air induction, but I tried it and it worked . . I see atmospheric pressure in the manifold about 1000 rpm higher now at WOT in 3rd gear due to my ram air setup, and less overall vacuum as the revs climb than before I sealed off the system . .

With projects like this, it gives me some small-talk to throw at the business people in my future who will get me the venture capital I might need.

 

Street driving . . I like how a properly build NA rotary feels, and sometimes on an autocross course the tach gets down around 3k when coming off a curve, and u need to get back on the gas. It's all subjective; everyone knows that turbo cars can be properly designed to kick *** in just about any kind of competition, but they feel and work differently than what I'm after with my car. It would be much easier to just build a turbo rotary like everyone else, but that's not for me.