Sterling

Eh-Eh-Eh...Don't get me ****** started, fellas!

Know yer **** before ya talk it.

ASEmaster

I would vote supercharger.. I had no idea there was one available for an FB. You get none of the lag from a turbo, you don't have to mess with the exhaust system to the extent you would with a turbo either. You probably wouldn't need to baby it like you would a turbo for it's longevity either (proper warmup/cooldown procedures). As far as stress on the crank goes, it wouldn't think it would be that adverse if done correctly.. if it took the place of your airpump, it would probably be NO different to the shaft.

Mad Max did have a sweet SC, but I've never seen one you could turn on and off like that How would the air get into the motor when it was turned off?

I don't have the $$$$ for any type of charged air system, so it's all academic at this point anyhow (maybe I could modify my smog pump to add some boost ), but there's my 2 cents!

mar3

iTrader: (8)

Two heavy helical lobes place a LOT more pressure to the pulley than the simple air pump especially when you consider that they're not simply adding a little air for emissions, they're cramming it into the intake manifold which resists this effort more and more as boost increases....think of the difference between blowing into a straw and blowing up a small balloon and now you've got a better idea of why the difference does exist...

Sterling

Boost remains constant.

Project84

check it out. 330 people viewed this thread, and only 34 voted in my poll.

Aico

I voted

Felix Wankel

Why waste such a strong exhaust pulse by running a supercharger? Unless you are just determined to be different.

Sterling

Yeah...It's all just a big attention getter. I'm gonna make all my own plenum, braces, pulleys, linkages, ductwork, ect so that in a row of forced induction rx-7s with the hoods all up (we have alot of them just lined up around here...they're everywhere), I can draw the most of the crowd just cause mine's...
...different.

People got money to burn on go-fast ****. I went to an import car show testerday and was very disappointed by the lack of inginuity and creativity. I looked HARD. Maybe 5% had done anything unique, and it was all just body stuff - Ya know - to be...
...different.

Exhaust gas energy? Man what a waste indeed! No joke. I have a Garrett turbo from a Dodge 4 banger sitting here. I've been wondering how I can utilize it in an exhaust system to turn an AC compressor. Only I want to use the AC system all redesigned to cool my intake and water injection...I dunno. I've had a couple ideas (some even flakyer than that) to utilize the wasted energy, including a way to simply ductwork it all to a shroud around the exhaust simply to blow away all the heat from that area.
Heh. Just some thoughts floating around just to be , well, Ya know...
...different.

Course I fell in love with the rotary engine cause it's, uhh,...

Ya know!

WhiteT78Supra

Go the turbo route.

Bob

Wattz

But uh, even if you turbo charge an engine, it'll still be under more stress than N/A, right?

So Superchargers are cheaper, but they put LOTS of stress, and turbochargers are more expensive (you gotta mod the exhaust and stuff too) but don't put as much stress as a supercharger...

So uh... Basically you want a supercharger if you don't drive the car as a daily driver, you want a turbo.

So if I'm gonna build a low-budget race car, a supercharger is gonna be just fine for what I want it for?

Spinner-D(eluxe)

I would like to supercharge my 13B 6-port someday because of the simplicity of it compared to a turbo system. With a supercharger you get more low end, and thats where the rotary needs the power in my opinion. Plus you get instant power, and no turbo lag, and the supercharger doesn't hold heat like the turbos do.

My ideal setup would be a Camden SC with a carb, and no emmisions contol crap, header to straight pipe back to muffler. The intake would be all custom piping to get rid of the stock emmision control add on crap on the lower manifold. Nice and simple. Sure the superchanger will rob a little power, but it's still going to give you way more instant torque.

SO what is commonly accepted is Turbos are good for durration races, like high speed 24 hour races, and superchargers are good for short durration races like auto-x. In auto-x you need quick short bursts of power, and in high speed racing on the track you need sustained cheap boost on the top end.

Oh and one last thing people forget is exhaust gass is not totally free. The turbos do create some restriction in the flow, but probably not that significant when they are spinning.

85RX7GS

iTrader: (1)

Supercharger!!!

peejay

I'll watch as all you supercharge folk have fun chewing up front bearings and tweaking E-shafts left and right Pull an engine apart and you'll see a wear stripe on the front bearing from the accessory belt(s), now imagine how much FUN the bearing will have when you put a really tight supercharger belt on it

Spinner-D(eluxe)

Hmmm, that is a good point. Hadn't thought of that. I wonder has anyone ever designed an electric supercharger, so you wouldn't need to run a belt from the motor to the SC?

mar3

iTrader: (8)

That service message for all the people that want to ignore that fact though it's been mentioned time and again. Oh, yes, also...boost is not constant in a SC application for the last freakin' time!!
It builds just like a turbo but in a more linear fashion...

Felix Wankel

Yeah, if boost was constant, you'd be pumping out your max boost at idle. That'd be a little freaky.

More Power

There are superchargers that are turned off like Mad Max's. Mercedes uses the Lysholm type and it has a clutch. The computer disengages the clutch while coasting. So in theory it can be done, although I have never heard of it. The reason you don't just have a bypass like on a roots, is because the roots type makes boost in the intake manifold. The Lysholm, or screw type, compresses the air and a bypass would merely keep the boost from getting to the engine, it would still have the same amount of drag on the crank.

I think superchargers are much more complex. The centrifugal comes the closest to a turbo in efficiency, but it makes boost later than a small to meduim turbo. The roots type makes boost early, but isn't very efficient. The Lysholm is the best, but it is the most expensive. I say stick with the good old turbo. It has work for tons of people in the past.

smnc

I'm opting for the SC method myself. Sometime next year, god willing I going to start work on a custom SC setup with a Magnuson/Eaton hybrid-roots type, or a Whiple lysholm-type. A nice top end power boost, but mostly a lot more power and torque down low and in the midrange where I want it most. And of course, no lag...

alien_rx7

I opted for the turbo choice. Saw an Omni GLH Turbo at the boneyard the other day and a Saub 900 Turbo. Thinking of going back and grabbing one of the turbos off and doing all the custom plumbing myself.

What is the best Turbo how-to book around?

Barb_wire

i dont like turbos warm up and cool down time

Manntis

A brief note on the Mad Max supercharger:

The supercharger is made by Weiand (pronounced "why and"). They make twisted-vane, roots-style superchargers for many after market applications. The system uses a GM 6-71 case as the base, and a Scott injector hat at the top.

On the movie car, this was all faked. The supercharger was empty and the carburettor sat inside. A small water pump was attached to the front of the supercharger to hold the drive wheel, this also moved the supercharger belt forward to clear the standard 351 water pump assembly, and the distributor has a 90 degree elbow to allow it to clear the supercharger. The supercharger belt is driven by an electric motor which is hidden by a yellow bucket in the garage scene in MM1. Weiand never had a supercharger that could be activated and deactivated. Even with huge compression it would be tough to generate 600bhp on a 351 in 1974 without rebuilding it once every couple of hundred miles.

About on/off superchargers:

Nowadays Delphi makes an electric powered supercharger (this is the company that makes the QUADREASTEER system for bloated GM trucks) that is not only on/off but can be varied according to desired boost. Unfortunately I believe it's sold to manufacturers only in wholesale lots, not individually to consumers.

jeremy

iTrader: (1)

now thats a damn good response.

Directfreak

iTrader: (2)

I wouldn't reccomend those. Honestly, just get a Turbo from a Turbo II, it will be MUCH better, and is designed for the rotary powerband and air-flow.

Maximum Boost - Corky Bell
Turbochargers - Hugh Maccines

Those are just to start. Check the Sticky thread on top for many details.

Phu5ion

Directfreak, i love the bookends.

NOTA V6

IMO, if SCs were really that great on NA rotary blocks, you would see a "SCing my NA" sticky thread rather than a "TII swap into a GSL-SE" sticky thread. Look at the number of people doing the TII transplant and the number of people doing the SC.

Now popularity alone is only an indicator, and honestly, not a very good one. After all, look at all the turbo rotary herd stuck on their Haltechs while the Wolf 3D V4 is better in just about every way (also my opinion), and has boost control, turbo timing and rev limiting built in.

It was pointed out to me when I was trying to decide what route to boost I would take that if SCing was that great, more people would be doing it, and there would be some websites around boasting about it and detailing people's setups. Also pointed out to me is that you don't see any serious performance rotaries of any kind running an SC for professional level track events of any kind. Those two facts hold a little more weight with me. There are reasons for that, even though I may not fully comprehend them.

To address some of the points and opinions already voiced:

Wattz: But uh, even if you turbo charge an engine, it'll still be under more stress than N/A, right?

Any forced air will put more stress on the engine than NA. You are forcing air into the combustion chamber which allows you to add more fuel to the mixture. That's where the added power from forced air induction comes from and why it puts more stress on the engine. There's simply more mixture for combustion.

So Superchargers are cheaper, but they put LOTS of stress, and turbochargers are more expensive (you gotta mod the exhaust and stuff too) but don't put as much stress as a supercharger...

It's all the same stress levels and costs pretty much the same, pound for pound of boost. The turbo has a higher boost potential, but also has more complexity and an increasing price tag for increasing the boost levels. The exhaust mods for a turbo are pretty much a manifold, wastegate and down pipe.

I haven't priced any SCs for a couple of years, but if we guesstimate that a SC setup costs around $2K we can roughly compare the cost to my setup:

$693 - T-60-1 Garret turbo (shipped)
$250 - HKS manifold
$336 HKS 40 mm wastegate
$50 - Mitsu Starion IC from junk yard
$350? - IC piping and welding
$147 - pair of 1600cc injectors (shipped)
$197 - Bosch 550 hp Fuel pump

That's $2023, and I still need the exhaust and anything else I may be forgetting. Subtract injectors for those with carbs, but plan on jetting or upgrading the carb to avoid detonation if you are running big boost. Add a stand alone ECU for those running EFI, since NO RX-7 stock ECU will handle the full fury of a T-60-1. This setup (the turbo and gear, NOT my engine mind you) is good for up to 500hp est. (manufacturers est. ). So, we're talking about 50% more expense for a big turbo setup, but also more than 50% more power potential added than a SC.

A stock J-spec with everything ( $2440 shipped and with spare parts to sell if you are doing an FB/TII transplant) and a rebuild kit ($500-900?) to almost guarantee some longevity, would total at around $3340, and you'd still need an exhaust and be running a TII TMIC.

***DISCLAIMER: All my cost estimates are based in reality. Some are guesses at and marked as such. Some expenses that no one can foresee, including variances of the engine and chassis you are starting out with, will happen with any project. YMMV.

So uh... Basically you want a supercharger if you don't drive the car as a daily driver, you want a turbo.

You want a SC if you don't want big boost, and want something simple to install or just something a little different. If you want something more tunable, with a higher output, more forum/mailing list tech support and the added techno wizardry doesn't scare you off, turbo is the route to go.

So if I'm gonna build a low-budget race car, a supercharger is gonna be just fine for what I want it for?

Depends on the racing you intend on doing. Although like I said above, I see no professional racers of any kind SCing their rotaries. This tells me that to be competitive, you need to look at the racing you intend on doing, and see what the rotary winners are using.

Spinner-D(eluxe): With a supercharger you get more low end.

Not so. Boost is boost. If I run 15 lb.s of boost through a turbo, I will get more torque (low end) than a SC running 9 lbs. The SC will give linear boost as the RPMs rise.

Plus you get instant power, and no turbo lag

True. I think this is what you meant by more low end with a SC. However, lag can be minimized on an injected turbo setup with thoughtful IC piping, intercooling, compression ratios and fuel mapping. And it can be minimized on a carbie turbo the same ways minus the fuel mapping. I am carbie illiterate, so there may be ways to do it that I am clueless to.

SO what is commonly accepted is Turbos are good for durration races, like high speed 24 hour races, and superchargers are good for short duration races like auto-x. In auto-x you need quick short bursts of power, and in high speed racing on the track you need sustained cheap boost on the top end.

Show me the top rotary drag cars and I'll show you some turbocharged rotaries. Endurance races are generally won by NA rotaries (ala the 787B) because they don't fail when the competition does. Boost is not good for endurance racing, it's good for acceleration. At least on a rotary. Again, that's my personal opinion based on my own observations.

If autocrossing is your thing, you must tune your driving to your setup regardless of what kind of setup it is, turbo, SC or NA. You must learn to keep the revs in your power band, where the boost is readily available. I have a friend that recently shaved almost 2 seconds off his runs in a day by simply running the course in 1st gear instead of 2nd. Again, YMMV according to your local autox course format. Autocrossing any high powered car is not as simple as pointing the car where you want it and mashing the go pedal like it is with most of our NA 1st gens. Lag can definitely add to the complexity of the situation though.

Oh and one last thing people forget is exhaust gass is not totally free.

The only free boost I am aware of is NO2. All other boost is parasitic.

Barb_wire: i dont like turbos warm up and cool down time

Everything has is up side and down side. Turbo timers will help you with the cool down time. No engine should be boosted while cold though, so the SC and turbo are again on equal ground on that note. In fact, it's the compression of air that heats all the turbo gear up big time, and that happens with an SC too. Although the turbo has the added heat of the exhaust manifold which it's attached to. Turbos are oil cooled, and sometimes water cooled too. SCs are not.

When you start pushing big power through a belt driven forced air induction system, you will find that many of the peripheral items add up the same between turbo and SC. SC running higher boost levels will need an IC and supplementary fuel just the same. Boost is boost in that regard.

So, look at the power level you want to achieve and start adding up the cost to benefit ratio. Will you need a stand alone ECU? Will you need a new carbie? Will you convert to EFI? Will an SC even get you to your goal? Will a big turbo push your high mileage engine over it's limit? It all comes down to your goals vs. the money you want to spend for them.