I know this has been discussed before but why is there no supercharger options for an FD? I think alot of people would like the idea of a set reliable forced induction system.

I for one don't need 500rwhp, crappy drivability, and a blown motor every year, i would prefer a set 12-14 psi and a reliable 300-350rwhp for daily driving, autocross, and track use.

 

The rotary has a very high-temperature exhaust, with exhaust pulses ocurring more often than in piston engines. This makes it very suitable for driving a turbocharger. Also, the turbocharger quiets down the exhaust note, which can be very desirable. Have you heard a ported N/A rotary lately?


I think a supercharger could work very well, it would simplify the piping, and you should be able to run a smaller intercooler or no intercooler at all. The supercharger can use a simpler fuel management system since there's no wastegate to worry about. The RX-8 crowd have been playing with the idea of a supercharger, you might check how that's working for them.


Look into Rotrex centrifugal superchargers, they seem good on paper.

-s-

 

There's nothing wrong with the stock twins. They will make more power easier and with less money than a supercharger. The stock twins are better than a supercharger in pretty much every single way.

 

Why do you feel the sequential turbochargers provide "crappy' drivability? And replacing the turbos with a supercharger isn't going to magically eliminate, or even reduce blown motors. Reliability is inversely related to performance modifications, irregardless of which forced induction system is used. You might be able to argue that the sequential system is trouble prone, but it's purpose was specifically to provide superior "drivability". Still, it seems to me that you could add a single turbo to get 350 whp ALOT easier (and likely cheaper) than a supercharger.

 

This is so simple. Turbochargers provide "free" hp, while a supercharger is parasitic and USES hp rather than provide it at low rpm, and then there is a constant parasitic loss at all rpm. So if your supercharger is providing 100 hp it might sap 30 hp or so. Look at Top Fuel dragsters.....the supercharger alone takes 900 hp to turn it at full boost.

 

Yet supercharged engines make more power than N/A ones, anyway.

Unless you tried to put a SC on thats so big the engine would have trouble starting and idling without being at a high enough rpm to make the power necessary to keep it running, its no biggie. Youre not putting one of THOSE superchargers on a 13b.

Theres also a supercharged renesis running around as a concept, anyway.

 

Supercharger are better at low rpm, full boost by 1500 rpm would not be out of question. We not talk about a top fuel motor which has to do with rpm just like turbos not hp. Additionally turbo's are parasitic as well.

I think that the real challenge is the fact that we have low compression engine designed to be boosted. Street superchargers work better providing additional boost for higher compression engines with relatively low boost 6-7lbs. That combined with high revs make turbo chargers the better choice.

 

http://www.camdensuperchargers.com/index.php?pag=403

 

Superchargers are less efficient than turbochargers and heat up the charge more...

 

According to Rotrex, their centrifugal superchargers are more efficient than turbochargers. Don't get me wrong: I haven't tested this or verified it myself, but that's a pretty big claim to be making so I hope it's true. By the way, the Koenigsegg uses two Rotrex superchargers, and it's a very well-engineered vehicle.


PS: that Camden thing is huge. I wouldn't put it on my car.

-s-

 

Hello-

Fact: the record for an internal combustion engine running the most power per displacement is... a turbocharged forced-induction-era 1.5L F1 engine. In qualification tune (i.e. tuned hotter than normal endurance race tune so it makes more power, but dies after about 2 laps of qualifying), they could get them to about 1000hp/L. Not even the supercharged top fuelers on nitromethane can do that.

Of course, the reason why F1 could is simple: money. But, you'd think with all the money they could get, they'd choose the option that gives the most power... and they chose turbos.

Now, for lag, superchargers win. That's why top fuel dragsters choose them. But for max power... I'm sorry... but turbos win.

Yes, it is possible to make a centrifugal supercharger get a slightly higher efficiency. However, this efficiency is only for a narrow speed range (which, unforunately, is governed by engine speed... not boost pressure... not a good tradeoff). And, that efficiency is a ratio of pumping power you get out over pumping power you put in. With the centrifugal supercharger, 100% of that pumping power is parasitic. For turbos, it's less than 100%... some, but not all, of the pumping power is for free from the exhaust.

As for the intercoolers... going supercharger doesn't fix anything. The intake air gets hot from compression and inefficiency, not from exhaust gases. The more efficient the setup, the smaller the intercooler. Positive displacement superchargers (the roots-style... the ones on all of the dragsters that have awesome response from low rpm on up) are the WORST of the group with a bullet.

The only true advantages of going supercharger over a turbo are:
- nearly zero lag
- simplification of the exhaust system

But, you get:
- less power
- more complicated belts
- a different type of intake system complication (no simpler than turbos... just different)
- positive displacement SC = more heat and inefficiency
- centrifugal SC = poor low rpm response... perhaps even worse than turbos

Take care,
Shad

 

My primary use would be auto x in which a supercharger would be the best.

The Camden units are only for 1st and 2nd gen correct??

 

Big turbos make for crappy driveability (lag). A supercharger would be for more reliable, spin up faster (power everywhere), and you should be able to use the stock ECU and injectors for up to 12-14psi with no sequential problems. Like I said in the beginning of the post I would be satisfied with 350 rwhp. The engine response would be excellent on a track and around town.

I just wish SOMEONE WOULD BUILD ONE!!!

 

Think of it this way. On the Mercedes SLR it takes 120hp just to use the Supercharger.

 

Actually, that is not entirely true. The turbo does use "waste" exhaust gas for energy, but it also stands as a restriction in the exhaust, and therefore a restriction to power. This is proven by the fact that many say a turbo "quiets" the exhaust versus normally aspirated.

For example, if you took a regular old NA engine of any sort and installed a turbo somewhere in the exhaust stream, but didnt pipe the compressor of the turbo into the engine, you'd see a drop in power, because the turbo is "in the way" of the exhaust.

Now, is that drop in power more or less than the same NA engine would see when spinning a supercharger? I dont know that any studies have been done one way or another.

You must also keep in mind the plumbing involved in a turbo install, as well as ALL the heat that it retains. Being a bottleneck in the system, it creates backpressure between itself and the engine, retaining more heat. Turbine housings are big cast heat sinks also.

People talk about superchargers heating up the intake charge, but they don't cause any more heat than a turbo...they may even cause less. Why is it that almost every factory and aftermarket turbo application uses intercoolers, yet many supercharger applications are not intercooled, if the supercharger supposedly heats the air more? How could a supercharger heat the air more at the same pressure, versus a turbo that is connected to a HOT turbine wheel, shaft, and turbine housing, while the supercharger is not anywhere near the exhaust?

Superchargers require no exhaust modification, no "up, down, left, right, around, large, small, large" exhaust piping to be run. Supercharger boost is very consistent and they are an easier platform to tune because of it. Supercharger intake plumbing is quite simple as well, especially when running non-intercooled setups.

I'd like to see a well set up supercharger on an FD, unfortunately the intake layout of the rotary does not lend itself well to screw type installs, nor is there room in the FD enginebay for a non-rigged looking centrifugal install.

The **** to have on an FD, if it were possible, affordable, and could fit, would be a twincharged setup with a big turbo for top end and a medium supercharger for low end controlled by a clutch setup like the a/c or airpump. The blower could get you going then once the turbo spooled at around 4200 the supercharger would disengage to prevent drag. Plumbing and cooling would be a nightmare but it would be insane to drive.

 

Packaging is the reason there are no ICs on factory superchargers. A "V" engine with a V mounted supercharger is hard to package with a IC.

Superchargers are driven purely from parasitic drag on the crank.

Turbos do present a exhaust flow restriction but the power they pump into the engine more than offsets the restriction.

You can make huge power with either. Turbos are more efficient.

When talking about the heat introduced into the intake charge, the supercharger is critical. Roots or centrifugal? Roots type beat the air to death and heat it up a lot IIRC.

 

I agree with the people who've said that turbos will make more power, but not everyone feels the need for 400+whp. Some of us would rather eliminate lag and add instant (and predictable) torque at lower RPMs, and supercharger is a proven way to do it.

Someday when I've got enough free time and money, I'd like to try putting a centrifugal (Rotrex) supercharger in my FD. I'd consider putting it where the air pump used to go, or possibly in the place of the power steering pump. My main concern involves combining the rotary's buzz with a supercharger's whine. It might sound horrific.

-s-

 

I think Camden makes one. I remembered talking to Atkins once and they said they could make one.

 

HAHA. Now that's probably true. I think everyone has covered all the pros and cons. Turbos will always put out more power, but I am a big fan of simplification. I can see where a single centrifugal supercharger would be useful for that and cutting down on heat related failures. Centrifugal superchargers don't heat the air up like the roots type blowers do.

 

Hmm...with all due respect to you and RR, you've made some inaccurate statements here:
It's only a power restriction until the turbine begins producing boost.
Your comparison is kind of irrelevant, because once the turbine begins producing boost, there are no losses. A Roots or screw SC's parasitic losses, on the other hand, increase with rpm, regardless of size, and those losses are always there.
Because a supercharger must be mounted as close to the intake tract as close as possible due to its design, which often negates the possibility to install an IC (this is one of the reasons why air/water ICs are often used, because they don't have the same space requirements as an air/air IC). You'll note that the vast majority of bolt-on SC applications only produce small boost pressures, to keep the intake temps from soaring.
The most commonly used SC is a "Roots" type blower, which doesn't actually internally compress the intake charge like centrifugal or screw-type SCs. In very simplistic terms, it depends on "compounding" the intake charge in the intake tract itself (the reason why it must be mounted as close as possible to the intake, negating an IC installation) to produce boost, which generates more heat. There is also the problem of some intake charge getting recirculated in the lobes as they rotate, generating even more intake heat.
Screw-type SCs don't suffer as much from this problem, but their parasitic losses are much higher due to the extra work and rpm required to produce boost.
A street-based SC installation will usually require an electrically-operated clutch of some sort to allow the engine to generate enough speed to offset the parasitic drag at very low rpms, as well as disconnect it at cruising rpm to cut drag and increase efficiency; those units aren't very light. The blower unit is can also be quite heavy, due to the necessary construction for structural integrity to withstand belt torque and high rpms.

 

I have to disagree with everything that Kento said.
Just because a turbo makes more power than it loses doesn't mean that it isn't a restriction. Have you ever heard of a turbo running lower pressure in the exhaust manifold than the intake manifold? A roots SC does not have increasing losses with RPM, it has increasing losses with higher boost.

A roots SC does not have to be mounted close to the engine. True, it does work a little better but only at low RPM.

The vast majority of bolt on roots SC are mounted close with no intercooler because they are mounted on high compression engines. The kits are limited to 5 PSI by the compression ratio. At that boost, they almost don't need intercoolers.

Roots SC's respond differently than turbos to intercoolers. An intercooled turbo keeps the same boost with more volume but an intercooled roots has lower boost with the same volume. Good for roots but not significant. Great for turbos.

My MR2SC came with roots SC and an intercooler running 8PSI stock which has been upgraded to 12PSI quite easily.

Oops, I won't disagree with this point. It's inaccurate but not completely wrong. (BTW, they recirculate almost nothing)

Street based roots SC do not require an electrical pulley clutch. OEM SC have them because it helps MPG slightly. A bypass valve is adequate but even that is not strictly necessary. A roots SC that makes a 2 litre engine equal to a 3 litre engine will be more efficient than a 3 litre engine even if it has no clutches, bypass valves, or even an intercooler. All those add-ons are there to try to get the boosted 2 Litre engine to be as efficient as a non-boosted 2 Litre engine.

A roots type SC draws less power than AC when you are making boost less than 1 PSI. It does draw a lot more when under full boost but we already know it produces more than it loses.



I feel an FD would make a nice roots SC setup because:
The boost would be constant at all RPM.
The engine bay temperatures and exhaust port temperature stress would be greatly reduced.
You could get rid of almost all the vacuum solenoids and intake complications.


You would definitely get less HP per PSI than you could get with a turbo (I'm going to guess about 20 HP) but I think the consistency and lower stress would make up for it. A roots blower is very comfortable at 10PSI and it works well up to about 15 PSI. Above 15 PSI a turbo will far outperform a roots blower.

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