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RUMOR: RX-7 to get Larger 2 Rotor Rotary?
Submitted by SuperUser on Monday, December 2, 2002 - 3:49pm

Dave Morris writes in: "There's a new RX-7 on the way. Senior Mazda engineers revealed key details during animated after dinner conversation at the October long range preview of the RX-8 in Hiroshima. The blueprint for the car is complete and the new two seater will share major systems with the RX-8. But while the new RX-7 will utilise the same elegant double A-arms front and five link rear suspension as the RX-8, as well as it electrically assisted rack and pinion steering, it will have a more powerful rotary engine. Instead of turbocharging the RX-8's 184kw Renesis rotary, Mazda is developing its largest ever two rotor mill, the power target is atleast 206kw.

"Mazda has always increased rotor width (similar to increasing cylinder bor and stroke in a conventional piston engine) in 10mm steps. The 10A engine had 60mm wide rotors, the 12A went to 70mm and the 13B twin and 20B triple rotor were 80mm, so it's a pretty safe bet the new rotors will go to 90mm.

"Assume the RX-7's Renesis will breathe as efficiently and rev as hard as the RX-8 emgine, and a quick calculation shows the capacity increase should deliver about 206kw - bang on the number suggested by Mazda's excited engineers. Making two rotors 10mm wider makes the engine just 20mm longer. That won't bother Mazda's packaging engineers, who will repeat the "front midship" engine placement of the RX-8 in the new RX-7. While the RX-7 will sit on a shorter wheelbase of 2400mm or less, it's two seat format means accomadating a slightly longer rotary behind the front axle won't be a problem."


Could the next RX-7 contain an engine dubbed the 14C? We'll have to wait. Rumors going around now way the won't "produce" an RX-7 until/unless the RX-8 is a financial success.

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subject:
I second that idea!!
author:
No Rotor
date:
July 7, 2004 - 8:32am
It should be noted that the plans for mazda to build the next RX-7 are depending on the success of the RX-8, and adding a 20B version of the renesis would do just that. Offering a different engine package for a car that is already turning heads would only bring the rotary loving crowd and new found owners/fans to get even more interested in it.

We're all aware of the fact that there is "no replacement for displacement", but we have to understand how corporations work, and if the toos are there, the parts are there, all they have to do is start putting it together, and having to go thought the design process of bringing a totally new engine to life can be avoided, and they are able to come up with a wining recepie for a new 20B motor, i say let them try! come on! we're all waiting!

Claudio RX-7
Santo Domingo, Dominican Republic
FC3S '87 - Custom TO4E Trubo
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subject:
No title supplied
author:
No Rotor
date:
December 31, 1969 - 4:00pm
14C. Why "C".
The 10A, 12A and 13B are all the same design engine. The reason the 1.3 litre engine got a B was to differentiate it from a VERY early 1.3 litre design.
It would make more sense to call the 1.4 litre engine a 14A, unless of course there is a radical engine design change in the 1.4 litre engine.
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subject:
No title supplied
author:
No Rotor
date:
December 31, 1969 - 4:00pm
the original article was from the much more credible Wheels magazine in OZ who sent 2 guys to Japan for the rx-8 preview and who actually attended the dinner.

-pete
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subject:
Interseting, but unrealistic I think
author:
No Rotor
date:
December 31, 1969 - 4:00pm
This article is interesting, but I think it is a bit unrealistic. I would think that if there is to be a fourth generation RX-7, there will have to be a lot more to differentiate it from the RX-8 than using the same suspension and setting the minimum 280HP target described in the article above, especially considering the expectation of a 300HP MazdaSpeed version of the RX-8.

If the new RX-7 has only 30 more HP than an RX-8 and has the same suspension, why would anyone buy an RX-7? I for one would not trade the practicality of a four seater for identical handling and a mere 30HP extra.

To get me to buy the new RX-7 as described above Mazda would have to make it considerably lighter (like 500 lbs), considerably less expensive (like $5000), or considerably better looking than the (already good looking) RX-8. Otherwise, I'm sticking with the 8.
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subject:
Sounds fishy
author:
No Rotor
date:
December 31, 1969 - 4:00pm
Consider a 4th gen similar in size to the 3rd gen. Mazda has made it clear through the past two gens that size conservation is something of a priority.

With a smaller, lighter engine, and without a turbo, it doesn't seem like mounting a 20B renesis would be too difficult a task. Fabricating an entirely new engine is not very cost effective, and Mazda can't be so foolish as to repeat some of the mistakes that they made with the 3rd gen. Hell, the 3rd gen even shared rotors with the late model 2nd gens. More common components between the rx8 and rx7 means a better price.

I would expect Mazda to make the next Rx7 a NA 20B, unless the primary concern here involves the 276hp rule, also known as 206kW.
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subject:
What if it was a Back to Basics RX-7?
author:
No Rotor
date:
December 31, 1969 - 4:00pm
I think that a RX-7 with a larger rotary would work great if it was in the right package.

If you think back to some of the most successful designs from Mazda, they had one thing in common, simplicity. I recall my father getting his first RX-7 back in May of 1978. The car was a simple two-seater, inexpensive, with great handling, beautiful body, and an engine that loved to be revved.

Fast forward 11 years to 1989, and you have Mazda's next big success, the MX-5 / Miata. The Miata had the same charms as that first RX-7; inexpensive, a voluptuous body and an over-engineered rev happy motor, all wrapped up in a simple two-seater convertible package.

My recipe for an ideal 2005 RX-7 would be a ~2600lb, two-seater, great handling of course, a nice 1.5L Renesis motor, and a slick retractable hardtop/convertible design. Anyone hungry?
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subject:
No title supplied
author:
No Rotor
date:
December 31, 1969 - 4:00pm
You should not forget the 15A. It had a displacement of
735ccm. The chamber width is 90mm.
http://www.der-wankelmotor.de/Motoren/Motoren_Mazda/Mazda_15A/mazda_15a.html
Your sincerely, Kurt Heintz
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subject:
Rx7
author:
No Rotor
date:
December 31, 1969 - 4:00pm
I really want to read the rest of that article. I tried to find "SpeedMagazine" on the web but i was not able to locate it" Could you help me?
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subject:
No title supplied
author:
No Rotor
date:
December 31, 1969 - 4:00pm
You are right it would actually be dubbed a 14A because it's the first engine of that volume to be produced. Felix Miata answered this question for us already in his famous FAQ.

http://members.ij.net/mrmazda/cfaqtext.html#10A12A13B
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subject:
RX-7 Larger 2 Rotor
author:
No Rotor
date:
December 31, 1969 - 4:00pm
Good grief, Mazda, an 11% bump in displacement/Horsepower for the next generation RX-7 over the RX-8 just doesn't feed the Bulldog!

I own a '93 RX-7 since new, and with reasonable mods it's making 335 hp in a weight reduced car of 2,649 lbs.

Your "14C" concept is much too conservative. Think of a weight to horsepower ratio of 8 lbs or less (Corvette Z06 = 3150 lbs and 405 hp = 7.8 lb per hp).

The next generation RX-7 needs 350 hp in a 2600 lb car stock from Mazda (7.4 lb per hp). It also needs 300 lb ft torque.

Your "14C" concept is way too conservative
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subject:
No title supplied
author:
No Rotor
date:
December 31, 1969 - 4:00pm
I know Mazda have not done much with their cast/forge re-tooling in their two factory where rotary parts are made to produce an all-side port rotary RENESIS engine. They have just innovated their current designs due to cost. I just can't imagine a bigger displacement RENESIS 2 rotor version of 10mm more per housing, that will just increase their cost of producing rotaries. Since now they totally have to make new rotors, housings, eccentric shalf, plates, etc & R&D. I would just use the same concept of the 2 rotor RENESIS & make a 3 rotor RENESIS (all-motor). Since most of the tooling are already made, most of the parts are interchangeable & it's already proven that the 3-rotor performs good in the last Cosmo in Japan. The bigger 10mm 2-rotor displacement cost of R&D & producting will be as much, if not more than that of producing a 3-rotor RENESIS.

A Rotary 2.0 liter 3-rotor RENESIS w/stainless rotors (like the Rx-8 RENESIS) will approx. produce easily 355-400Hp@7000rpm all-motor & produce torque of arround 250-300ft.lb.@3000rpm. And, rev up to 8000-8500rpm reliably on stock Cosmo 20B eccentric. And, then if eccentric shaft upgraded to 1 mm dia. like the Mazda 13G, at same 8000-9000rpm will be possible, with riability wear. Also, being all-motor, the 3 rotor will have the revolution speed of a 2-rotor, but with the torque of a small-block V8, thus the engine will not beg you to turn off the A/C, & other engine accessories like the FC/FD3S 13B's. The 3-rotor RENESIS will seriously meet most emission standards, lower cost in production (the tooling it's already made!), and give the competition some serious performance competition. Since, IMHO I think this would be a worthy replacement for the Rx-7... since the whole concept of Rx-7 with sequential turbo totally failed in the US due to mechanics training, and easy tampering of the engine... and now bigger displacement of just 1.4 or 1.5 liter will just be dumb.
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subject:
larger engine
author:
No Rotor
date:
December 31, 1969 - 4:00pm
I believe the fourth gen rx7 should have 2 engine options. If the next rx7 weighs about 200 lbs less than the rx8 then 250 HP should make it competative in price and performance to cars like the nissan 350Z. Then for a higher horsepower version, a 20B renesis should give it the performance to compete with cars like the chevrolete corvette. I think this would be a better option than turbocharging the 13B renesis, or developing an entirely new 2 rotor engine with just 100 more CC's. You would have one car that could fit in two price catagories and please more people. I too believe it would cost less to make a 20B three rotor renesis engine than an entirely new two rotor displacing 1400 CC's. The added TORQUE of the 20B alone would be worth it.
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