I am wanting to get some advice - I wish to buy a Rx7 S3 and bolt a 20B under the bonnet.

1) How hard is it?

2) What do I need?

3) Can I super-charge it?

4) What does FC stand for?

Thankyou all...

 

I'm sure that someone will tell you how to use the Search button on the forums.....that is where ALL your answers are found!

 

1) It will require signifigant modifications to both the car and your pocketbook. Definately not something for a beginner to tackle on his first try.

2) Depends how far you want to go and exactly what you want to do.

3) Yes but why would you? It's twin turbocharged in stock form.

4) FC is used to identify a second generation RX7. A third generation is an FD. I believe it is either from the serial numbers or a factory designation.

Not to be a ****** but from the sounds of it you are really green when it comes to RX7's. It would probably be best that you get in touch with someone local who has been there and done that. Fortunately you live down under and there are some really good rotary shops available.

 

Warmup, cooldown and lag times.

Unfortunatly, I am in the west, in a reasonably isolated location, and most of the rotor shops are in the east. Australia is approx. the same size as the mainland of the US, but we only have 19 million people. The distances between places is bigger...

 

1) Its about the hardest thing to do besides installing gull wing doors. Basically, if you need to ask, then you need to task a professional shop to do it for you.

2) You need the engine, various parts and modifications to install it, and everything to support it at the torque level that you plan to run it.

3) It comes supercharged with two turbos. If you are asking if you can add a belt-driven supercharger, then yes, you can add a belt-driven supercharger to just about anything if you have enough money.

4) http://members.ij.net/mrmazda/mdictionary.html

In the US, warm-up and cool-down times apply to the engine, so most of the people on this forum don't understand this statement. As for lag, the stock 20B-REW turbos have hardly any lag.

 

I'm game. And maybe stupid

Thankyou - very helpful.

I had heard that thrashing a cold turbo is asking for it to fall apart, and turning off a hot engine/turbo was asking for similar trouble.

I have also heard less-than-glowing reports about the sequential turbo system, and much power could be gained by replacing them with a big single turbo or belt driven super-charger. Am I wrong?

 

Thrashing a cold engine is asking for it to fall apart. Adding boost from a turbocharger or belt-driven supercharger only makes this worse.

You can run the turbos unsequenced if you like. Here is a dyno sheet of a 20B-REW with the stock turbos running unsequenced, tuned by a top performance shop.
http://www.cris.com/~Asam/Dyno1.html

Stock 20B-REW with sequenced turbos:
https://www.rx7club.com/attachment.p...postid=1819419

Comparison chart here:
https://www.rx7club.com/attachment.p...postid=2315881

 

Wow. 2 psi makes a fair difference.

I also like the idea of being able to turn a super-charger off...

(Where I come from, Super-charger = Belt driven, Turbo = Turbo-charger = exhaust driven)

 

Yes, but it may make more or less difference depending on the given turbo and engine system. Each system will have a certain sweet spot where a small gain in boost will yield a large gain in power.

I think you are watching too many Mad Max movies down there. Most modern belt-driven superchargers have a bypass valve that allows for better efficiency when off boost. Turbochargers do this automatically by design, and this is why a stock turbocharged and non-turbocharged FC have nearly the same gas mileage rating.

Yes, that's the normal thinking among the general public in most places. In international engineering terms, however, a supercharger is anything that increases the pressure of the intake air in an internal combustion engine, while a turbosupercharger (aka turbocharger or turbo) is a supercharger that is driven by a turbine.

 

I was lead to believe that they have a clutch on them not unlike an air-con compressor, and that the charger (belt driven, obviously) could be turned on/off and also set to go on and off at pre-defined rev-points...

 

Not the ones that I have seen. They usually are on full time. That is the big advantage that a turbo has. One can turn up or turn down the boost on a turbo car by controlling the wastegate with a boost controller. To get more boost out of a supercharger you need to change the size of the pully.

 

Yeah, and you'd have to have a pretty heavy duty (read - expensive) electricly controlled clutch to handle the high loads that serious superchargers have. But like SoloRacer said, even then it would be largely self defeating.

 

I don't see much point in that, other than it would be a great way to sell clutches and belts.

Click on the bypass valve link in this article:
http://www.superchargersonline.com/content.asp?ID=85

 

HIya All

Ambitious project.. I honestly wish you good Luck with it.. We need more 3-Rotors out there..

Belt Drive Clutched Supercharger... Nope.

Have Never personally seen one. Not to say they DONT exist.. but I have not seen one. And been looking at this stuff for quite a while.. Not to say I am crusty or anything.. LOL

The closest I ever heard of was some sort of Turbocharger inlet side with a Hydraulicly driven rear section... so when Oil pressure increased.. so did the speed of the COmpressor wheel... thereby increasing boost.
There was supposed to be some sort of setup where you could vary the allowable oil pressure to change max boost achieved.. and or the spool up of the system.
However... Never saw it.. and this was around 6 years ago I heard rumor of it coming out. Havent looked for it really.. but it may be out there..
BTW... Go here halfway down to read about the Mad Max blower.
http://www.madmaxmovies.com/cars/Rep...ack/index.html

 

Here y'all are. Obviously not as popular as I thought, but it has been done...

(clutched supercharger, that is...)

http://www.fefcholden.org.au/techinf...e/norman9.html

 

Found more...

http://mr2.com/TEXT/SuperChargerInfo.html

The system is briefly touched half-way down this page...
http://www.turbomagazine.com/features/0211tur_celica/

 

a supercharger is way less efficent than a turbocharger...

a supercharger will rob about 200 hp on an 800 hp engine, where as a turbo would only rob 50.

 

Yes, but I still see no point. Hey, if you like it, then by all means put it on your car. In my opinion just the bypass valve will work better, and will decrease the complexity and wear on the components vs. the switch.

LOL, leave it to SPiN to pull up Mad Max trivia.

I don't really like superchargers much, but your statement is a bit biased, lol. Genereally, you are looking at about 10% bhp loss at the flywheel to drive the supercharger. After that, you are looking at the adiabatic efficiency of the supercharger, which can be as low as 55% for a Roots type blower, up to over 75% for a centrifugal supercharger. Since a centrifugal supercharger generally has exactly the same construction as a turbocharger compressor, you could consider their adiabatic efficiencies the same. The Roots blower is the big heat monster.

 

Some (All?) of Mercedes's AMG cars use clutch-based superchargers that only run during load.

 

Do some research. Some of the Mercedes (I think?) models that came with superchargers were switched...

The M-62 supercharger is a clutch-type. They're cool

~Brad

 

Mad Max had a clutched blower too....

 

Actually, it was clutched at the drive pulley, unlike Mercedes. Until you pop the switch, the belt didn't turn.