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.

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!

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.

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.

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.

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.

Directfreak

iTrader: (2)

Good write up Jim, but let me interject for a few minor details.

I found this to be a funny remark, and a very true statement..

The Haltech does have rev limiting (two stage as well!), boost control (easily controlled with an adapter), NOS control, turbo timer output, shift light, anti-lag, and many other goodies. Not everybody can use a handheld display for tuning like the Wolf. Haltechs require a PC.
Both are outstanding units with technology that just was not even heard of more than 7 years ago. I also believe ECU choices are also GREATLY influenced by the local tuning shops. Whatever they use, - you use, for simplicity's sake, if you want their help.



Yes and no. CFM will make more of a difference than just boost levels. For example, you can make X HP on a stock Turbo at 15 lbs, and the same X HP on a stage II turbo at only 10lbs of boost because of the higher CFM.



Good prices. I need to shop with you!



I like the "on a rotary" part.
With the exception of Multimillion dollar race car teams, Boost (theoretically) "should not be used for more than 15 seconds at a time" - Corky Bell, Maximum Boost.



YMMV? Just guessing what that means.

What's the 1st "M"?

Many Modern Superchargers and kits do have engine oil and water cooling.. (they all have oil cooling, even if self lubricated)

Again, good write-up!

Directfreak

iTrader: (2)

Ahh...

Your Milage May Vary...

Ok, I get it now. I used to hearing,

Your RESULTS May Vary..

Thanks Felix, it was bugging me.

NOTA V6

Hey guys,

Alex's comments got me to look over a couple of mine.

Haltech comment: I guess I formulated an opinion without really digging in on the information available. It was pointed out to me by a couple of actual Haltech users that most people buy them simply because most people buy them. That was my point really, not that the Haltech is a bad unit. Sorry to you Haltech guys. No offense intended.

Boost - lb. for lb. comment: I was not clear enough. I was assuming that with equal boost, that the same CFM would actually be entering the intake. I wanted to make an apples to apples comparison about the equal boost levels, and the higher boost potential of the turbo.

Thanks for pointing out the addition of oil and water cooling on the modern SC units Alex. This actually confirms my suspicions that the SC air compression causes just as much heat per psi of air compression as a turbo, since it requires cooling of the compressor. So again, the turbo has the additional heat disadvantage of being directly bolted on to an exhaust (turbo) manifold.

You can come shopping with me any time. PM or e-mail me if you want info on where I got any of these prices (except the junk yard IC, since they don't intentionally stock Starions/Conquests just for us. And the IC piping and welding I sourced out through a local friend). I would announce them here, but none of them are paying me for the advertising. Eventually, I will put reviews of all of the places I bought parts from on the Northstar vendor page.

Thanks for the kind words.

setzep

Hey Jim thought you weren't going to use that I/C that you had? Did you have someone fix that crack at the bottom? Also I talked to a few of my bussies and they said not to worry about the fins bending, they didn't do that because they were old just because they are so damn thin. I took a look at my I/C that hasn't even been run yet and the fins were week also, just took a small screwdriver and spent a few min getting them back into place. I hope you end up using that I/C it looks to about the perfect size because of you running the A/C and all...

Have you made any progess since I was there? After taking a look at your TB I decided to do the same I also ordered my turbo, TD07 25G 17cm divided exhaust housing. Just waiting on that so I can see what I need to do for a exhaust manifold.


Cam

NOTA V6

Hey Cam,

After sourcing FMICs, I determined that we can make the Starion IC work. I am planning on returning the black panel that fits over the condenser into place, and it will not be mounted in the grill opening. So it will be hidden after all, so it can be ugly as all get out, as long as it works. So, we will gum it up with as much welding as it takes to seal it. Why do they get so much for an IC anyways? It's just a radiator with fins on the inside too...

Many of my parts have arrived, but I have to get up my ambition to get out to the garage and start doing things again. I'm sure when the turbo arrives, I will have to get out there and install it. After I finish making whooshing sounds with my mouth, and throwing myself back into my chair. The pace slowed down quite a bit on my project when I realized it wouldn't be ready for the MRR.

Take care,

Jim

Directfreak

iTrader: (2)

-lafz LOL!

I know what you mean Jim, today I put the turbo in my car.

I know it's not exactly what you mean though.

Actually, all I am waiting for now is my new Fuel Rails, and I will start putting everything in the car. I am 95% done with the parts buying. I even got the Haltech last week.

setzep

Jim-
I'm sure once you get your turbo you'll have a lot more ambition to get out there to work on it, I have a feeling when I get mine (hopefully sometime in the next week or so) I'll be out there in the garage getting some buisness done

Alex-
What turbo is that?