nyccollector

I have a very low mileage (11,700 miles) 1988 Series 4 RX-7 convertible and would like to know the plus and minuses of maybe installing a supercharger. Would the supercharger unit in any way harm the engine or cause it to overheat in the summer and would it effect my gas mileage? Also, and more importantly, would it over stress the engine or existing drive train? Any thoughts would be appreciated...........

Thanks

misterstyx69

iTrader: (142)

Play nice people.
Evan,get your flame suit on!

jjandros

iTrader: (7)

Would it effect your gas mileage?!!!... Yes. Research. Use the search bar and you'll come up with plenty of info. Promise.

DennisH

I'd imagine you'd be fine for the most part, though it really depends how much boost you were planning to run. anywhere from 6 to 10 psi should be okay on stock components.

I think the existing drive train is good for up to around 250hp or so, the fuel pump is good to around 200hp; so it'd be worth upgrading other components to handle the extra power.

If I had the money, I'd probably do a supercharger myself (I have the same car), because it provides more consistent boost, and low-end torque which these cars can really benefit from, so I say go for it.

nyccollector

Dennis,

The RX-7 convertible is a terrific car but frankly rather slow from a standing start - power doesn't really come on until somewhere around 60-70 MPH. Price aside any recommendations as to which supercharger make I should consider and what additional (other) components should I upgrade for a supercharger installation?

Thanks

wthdidusay82

iTrader: (15)

I believe www.atkinsrotary.com has a supercharger kit. Its pretty expensive though, or check www.camdensuperchargers.com you could do a similar custom setup for a fraction of the price.

Rotary >Pistons

DennisH

Well, like I said, I have the same car, so I know where you're coming from on the speed issue.

I don't know a whole lot about superchargers, if I had the money, I'd definitely throw it down to do a set-up though. I was planning to stick to N/A and do all of the bolt-ons, do a streeport, and other upgrades like flywheel. It'll be quick enough for me, and the car will handle even better.

wthdidusay82

iTrader: (15)

Try doing a search on Google for supercharged rx7 and it should come up with some threads from rx7club

Rotary >Pistons

Evil Aviator

There are four popular types of automotive superchargers:
1) Turbosupercharger (called a "turbocharger" or "turbo" for short) - An exhaust-driven turbine with a shaft that spins a centrifugal air compressor. Advantages: Capable of high boost pressure, good thermal efficiency, easy to intercool, quiets the exhaust noise, no drive belt. Disadvantage: There is a "lag" in the time between pressing the gas pedal and the turbo producing boost.
2) Centrifugal supercharger - A belt-driven pulley attached to a gear drive that spins a centrifugal air compressor. Advantages: Capable of high boost pressure, good thermal efficiency, easy to intercool. Disadvantages: Slow boost rise, drive belt reduces engine power.
3) Roots supercharger (usually called a "blower") - A belt-driven pulley attached to a gear drive that spins a twin-lobe air pump. The air pumps through the intake system until it hits a restriction in the intake manifold, where is compresses. Advantage: Fast boost rise. Disadvantages: Low boost pressure, poor thermal efficiency, difficult to intercool, drive belt reduces engine power.
4) Lysholm supercharger (also called a twin-screw) - A belt-driven pulley attached to a gear drive that spins a twin-screw air compressor. Advantages: Capable of high boost pressure, good thermal efficiency, easy to intercool, fast boost rise. Disadvantages: High cost, drive belt reduces engine power.

Given the high exhaust energy of the rotary engine, a turbosupercharger is usually the preferred type of forced induction.

A supercharger will not harm the engine if it is installed properly and the engine is tuned properly. Otherwise, the supercharger will blow the engine.

You can get a decent aftermarket all-aluminum radiator for about $300-350. Given that a supercharger setup is going to cost you between $6,000 and $20,000, the radiator is peanuts, and you can even install it yourself in about an hour. Besides, the stock radiator sucks, and even with low mileage you may want to check the top for cracks in the plastic.

Gas mileage at cruise should be about the same, but it will decrease drastically during acceleration.

Generally, the drive train can take about 200hp before it gets overstressed. However, it depends how you drive and what kind of tires are on the car. For example, if you drag race with slicks then you are more likely to break the drive train even with the stock engine, but if you just drive around the street with regular street tires the tires will spin before much stress is put on the drive train.

In that case there is something very wrong with your engine. You should get it fixed before you spend your time and money installing non-essential parts.

misterstyx69

iTrader: (142)

I didn't mean to scare you of when I said get the flame suit on!
Just,personally,if I wanted the power of a supercharger I would go turbo.
The reason is that a whole Turbo engine can be had for the price of a supercharger.Maybe less.

imsplitbit

I was gonna say the same thing. Stock engines with turbos already attached are pretty easy to come by.

Evil Aviator

+ The $6,000 Camden kit is not any better than a $1,500 Turbo II engine.
+ The Nelson/Paxton kit is out of production, and the kit was flawed anyway.
+ A good custom setup is way too expensive for most people on this forum.
+ A convertible is not the best platform for a fast RX-7.
+ Most people on this forum cringe when a good, low-mileage car is molested.

Were I in the situation of the OP, I would get the engine fixed by a professional, sell the car, and buy a ghetto-molested Turbo II that has been pre-ruined by some wanna-be drifter. Car Math: A $4,000 Turbo II + $10,000 in shift mad quick yo dorifto mods = a car with a $2,500 resale value. It is much smarter to buy a car from the wanna-be drifter who ruins his car as opposed to being the wanna-be drifter who ruins his car.

nyccollector

OK - based on your responses to my questions about supercharging my RX-7, I've decided to keep my convertible just as it came from the factory. I guess it really doesn't make much sense messing around with a stock engine for better performance. Buying a fixer-upper makes much more sense and certainly much cheaper in the long run.

Thanks to everyone who responded to my thread.

misterstyx69

iTrader: (142)

Well I have seen 1500 dollar complete used SC's on the forum For Sale.Also complete drop in engines for 800.
I wouldn't really be worrying about overheating the engine,I would be worrying about Pissing off your Budget.
Even if you get a supercharger you have to run Fuel.That would require a ECU of some sort.
..at least with a stock TII engine and harness,the Stock ECU could suffice.
Then you could build on the TII keg for more power as you get more Funds in that Quest For the "Big WEEEEEEEEEE!!!!!"

S4 Vert

I already got roasted for asking the same question, so I wont roast. It just seems adding a supercharger would fill the low end power and torque void on na RE's.

dream3rdgen

iTrader: (1)

The availability and knowledge on turbo 7's is so much more it would be better obviously. A blower would be efficient but it will be more pricey and less fuel efficient no matter what.

RotaryRocket88

iTrader: (7)

Those supercharger kits have been passed around the RX7 community so many times it's amazing. For the majority of those that have owned them, it seems to have been the kiss of death for the engine due to half-assing the fuel/fuel control. For just about any supercharger build thread on here, there's usually a corresponding For Sale thread and rebuild thread.

Evil Aviator

Blowers are typically the least efficient of the different types of superchargers. I would like to see somebody try one of the new thermally-efficient Eaton TVS blowers on an RX-7, but so far I am not aware of any such project.

Besides the fuel, the shade tree mechanics use the wrong size of supercharger, they chum the supercharger because they forget that a rotary engine does not redline at 5,500rpm like a piston engine, they try to get too much boost out of a Roots blower that was never intended to produce more than 12psi boost, they do not have the skill to align the pulleys, they incorrectly intercool a Roots blower, they try to install a BOV on a centrifugal supercharger, they try to "twin-charge" their engine backwards, and sometimes they even get it to work but are not happy with the results because they didn't realize that the belt saps 40hp from the engine. There are many other stories that I can't recall at the moment, but I think that gives a good rundown of what happens when you don't know what you are doing and you are too cheap to pay a professional to do it for you.

84stock

iTrader: (5)

Been there done that, and have that...camden that is.

My advice, atkins 5th&6th port sleeves and a rb streetport exhaust system and that's it.

Aleda21

What kinda power does a supercharger givd

Evil Aviator

A supercharger does not produce any power. It increases the density of the air that is going into the engine. The resulting power that is produced by the engine will vary based on several factors such as engine displacement, engine rpm, the amount that the air is compressed, the heat generated by the compression, the heat rejected by intercoolers or other parts of the engine, the power required to run the supercharger, the ignition timing, the air-fuel ratio, the ability of the exhaust to scavenge the extra flow, the ambient temperature and pressure, and other factors.

84stock

iTrader: (5)

My street-ported supercharged 13b put down 227 rwhp and 180 ft lbs torque.

Feels fast, torquey and impressive. However, for little more than I invested in all my supercharged aspirations I could have easily had 300-350 rwhp with a turbo and good standalone.

Next venture, to be done with my donor gslse, is a v8 swap. Testing out a 327 that I'll build which should produce 350+ hp and 360+ ft lbs torque plus nitrous.

wthdidusay82

iTrader: (15)

I want to see a supercharger and turbo at the same time that'd be impressive

Rotary >Pistons

Evil Aviator

That is called "twin charging". In a functional sense it is really more for rally cars and truck pulls, but some people do this to their street cars just because it looks cool. Otherwise, it is usually better to just use a good ball bearing turbo or a Lysholm supercharger to get similar results with less weight and less complexity.

MmSadda

iTrader: (2)

I speak from having a couple years of hands-on experience with the centrifugal Paxton-Nelson kit. Most of what I can't do on my own in my garage ws done by Defined Autoworks here in Columbus, OH.

Regarding the Paxton/Nelson: In a sentence, it's very poor bang for your buck, but is quite a fun kit to run. You can pick up a kit here for $1000-1500 if you're patient. I got my full Paxton kit for $1000 with an oil cooler, but had to source the appropriate pulley. To safely run this $1000 kit, you're going to want to spent $1k+ on a standalone, and another $1k+ on installation plus tuning. Unless you're going with an oversized (lower-boost) I would also strongly suggested a better fuel pump, and 550cc (I think) injectors, so that's a few hundred more. With the stock pulley on stock ports, you can expect to see around 215hp to the wheels, and a surprisingly flat torque curve. However, running the stock 9lb pulley puts a fair bit of stress on the engine.

In short, as EvilAviator (who knows his stuff) said, the kit is truly flawed.

For the same $3500+ you'd spend on properly running that kit, if you're smart, you can probably do a decent S4TII engine with a nice turbo and standalone. This will probably make more power, and will be MUCH better suited to further modification.

With all that said, I wouldn't trade my idiotic supercharger setup for the world. I love it, I love how fast the boost comes on (even though you can get quick boost with modern turbos.) I love the power delivery at high RPMs. I personally love working with it, and wouldn't give it up for anything. But I'm daft and have more money than sense (and I don't have that much money.)