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Discussion Starter #1
I love the WRX and the STi. If I can afford it, i'm definetly going to get the STi, just have to wait and see if I can save enough for a down payment. If not, i'm either going to get a normal WRX or a Mazda RX-8 (I can get it for wholesale since I work for Hertz). I like the RX-8's interior a little better, but the 247hp rotery engine only produces like 157 ft/lbs of torque. So it goes 0-60 in 6.3 seconds. Where as the STi and the normal WRX can beat it. I'm a speed freak.

But I really don't know to much about the two engines. So can someone list some pro's and con's about the H4 and the rotery engine?
 

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Enyon,

I haven't driven an STi yet (mine arrives at the beginning of August) but I do own a 3rd gen RX7. I've also driven hot WRX's as well as 2nd and 1st gen RX7s. Here is my take on things:

Many will tell you that rotary engines are unreliable. This is not strictly true. Much of the reliability nightmares came from the 3rd gen (1993-95) which was related to poor design of the exhaust system and other related issues. The new Renesis engine is a significant evolution of the 13B platform and Mazda appear to have done a superb job with the design and tuning of the car.

Don't be too put off by the low torque numbers. The RX8 gearing is very different from the STi's due to the extremely large rev range (redline at 9000). The STi gets it's impressive 0-60 times more from the AWD than the 300HP. Furthermore, rotaries are quite happy to rev to their redline as the reciprocating mass is extremely low.

In terms of power-to-weight, the rotary is unmached by any piston engine. The 13B (two-rotor) can produce upwards of 600HP and yet weighs much less than a similar 4-piston engine. It's also smaller and can be mounted much lower in the car. This is the primary reason to choose a rotary-based car--reduced weight and better handling. If you like the way a very light car feels as it turns in, then the RX8 (2970lbs) is your car. And remember, less weight means better acceleration, cornering, and braking.

Okay, so, now the bad part: rotary motors MUST be tuned correctly. Many a 13B have been destroyed by a single detonation event. The apex seals, which are similar to rings for piston engines, are extremely fragile. This means that tuning a rotary to higher power can be a daunting task. With the RX8, it's going to be even harder becuase the car doesn't even start with a turbo. My bet is that even with tuning, intake, exhaust, ingnition, and other mods you *might* see 300HP. Put a turbo on for more power and you really run the risk of toasting your rotary.

Rotary engines also are highly inefficient as compared to a piston engine. Fuel economy is poor, and fuel consumption at the track is high. This has impact on endurance races. That said, Mazda did an amazing job winning Le Mans in 1991 with their quad-rotor prototype cars.

http://www.scuderiaciriani.com/rx7/787B/

On the chassis side, the RX8 will probably provide a smoother driving experience and ultimately a higher cornering speed. However, the horsepower of the STi offsets this advantage. I expect the STi to be quicker at the track, but it will probably lose at the autocross. If you don't believe me, go to a local autoX event and watch a boxter or S2000 outrun a 996TT. HP and AWD are great, but weight is always a killer.

The STi will be dominant at the drag strip until you get to the highly modified classes.

The STi has a huge advantage in tuning. You can spend about $3000 on your STi and probably see an extra 50-100HP. The car will be devastatingly fast. Another $5k and you'll be in the high 400HP for sure. It's too early to talk about reliability, but if the past is any indication, the Subaru platform will be reasonably sound.

For full-bore racing (i.e. spend $50-100k on your car) the RX8 will ultimately be the quicker car. It's low-slung design, far superior aerodynamics, and rotary powerplant will defeat a similarly-prepared STi. AWD is not really an advantage on the track, where weight and chassis dynamics are key.

There's other big issues to consider. The styling of both cars are a love-it-or-hate-it kind of affair, but I think it's clear that the build quality and interior design are much nicer on the Mazda.

That said, I'm not going to upgrade my RX7 to the RX8. I don't like suicide doors, and my current car weighs under 2800lbs and will have about 350HP to the rear wheels when it gets back on the ground. I'll outrun any 500HP STi at the track. However, I'm going with the STi because of it's daily driving pluses: 4 real doors, cargo space, AWD, and great low-end grunt. Maybe an extra 50HP from a tuner wouldn't hurt...

Good luck with your car selection,

-ch
 

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It looks like Hyperion did a lot of good explaining about the two types of motors. Here are a few basic things I can add:

* The small, compact design of the lightweight rotary motor not only allows it to be placed lower in the chassis; it results in nearly perfect 50/50 weight distribution, regardless of how many passengers are in the car. And don't forget the simplicity of design; their designs have very few major moving parts (only THREE in the last generation RX-7), compared to around eighty or ninety in your average engine.

* Obviously, inline and V-shaped internal combustion engines are the majority of the automobile population. This means that finding a shop that can repair and tune boxer engines can be a pain in some cases (but it's not really that bad). But finding a shop that works on rotary engines is a far more daunting task in most cases.
 

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Discussion Starter #6
Hyperion: Thanks for the great post. You definetly cleared some stuff up for me. I'm not really looking to put some mods under the hoods of these cars any time soon, maybe a year or two after I get them, but certainly not $50-$100k worth. hehe, don't have that much money.

I also went to the howstuffworks.com web site, and they have cool animated .gif's of the rotary engine, but not the H4. It was really cool to watch in motion.

DeeezNuuuts, I also didn't think to much about repair costs. Its going to be something that we're all going to have to face eventually.

I got some time to choose, not a big hurry, just tyring to put things in perspective, thanks guys.
 

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How to tune a Blitz BOV?

As a side note, I've been hearing that the dyno results of the RX-8 aren't so great... a few people have reported RWHP dyno results in the 170s, which is bad. Even though this was just from a few cars out of many RX-8s, the ones tested mean one of two things: either there is some SERIOUS loss of power in the drivetrain (over 27%) or the 247 hp at the crankshaft is an optimistic rating.
 

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Yeah, i was watching car and driver and they were comparing it to other sport compacts and talking about the 250hp.

Plus Super tuner TV named that Dodge SRT5 or whatever the name car of the year.... sure....
 

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srt4. the neon. awesome car, in concept. never seen or driven one, but is an awesome alternative to an wrx.
 

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Hmmmmm...., let me think about this one....... Neon.....Impreza......Neon........Impreza........

....need I finish this thought? I would rather buy a Lancer....
 

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:) oops. by "alternative", i meant that if someone (e.g. college student) couldn't swing the few extra thousand bux, it's a great alternative.
 

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Really? The SRT-4? Wow. I've driven one, and that fothermucker is MEAN. Regardless of what gear you're in, punch the gas and the turbo responds with almost no hesitance. It is a lot of STRAIGHT-LINE PERFORMANCE for the money, but unfortunately not a lot of car. I'm sure that this debate has been dragged on for quite some time, but if you don't want to read this, then don't. All that power in the SRT-4 is GREAT, but consider the fact that it's all running through the front wheels without the aid of any type of LSD, so it can get messy. The interior is rental-car quality, and the exterior is still that of a Neon, just with a more "sporty" touch. It does NOT deserve to be car of the year.
 

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I dont really like it, it looks like a yellow (hate the colour) neon with a bridge on the back. Maybe in a few years it would get this award...

I agree it does not deserve car of the year, but we have to remember this is Super Tuner TV, and it is their first car of the year award. I usually only see Nissans and Hondas on that show anyways :(
 
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