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Thinking of buying another rx 7 or 8

Old 09-30-2015, 03:38 PM
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Thinking of buying another rx 7 or 8

So i love my 04 rx8 its an awsome car i use it as my daily right now so i was thinking of picking up an rx7 or another rx8 to make a street/track car i have a few 3rd gen rx7s in my area id like to buy but the real question here is which has higher tuning potential the rx7 or the rx8?
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Old 09-30-2015, 03:52 PM
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Tuning for what? Raw power? With or without an engine swap? Without, FD RX-7 hands-down. Best of both worlds is a 13B-REW swap into the RX-8. Either way be prepared with a metric butt-load of money...
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Old 09-30-2015, 05:43 PM
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Having owned both an FD RX7 and a RX8, I would say the FD RX7 has greater tuning potential with aftermarket turbos and more. The RX8 Renesis engine was never designed to be boosted. Many have with some success, but engine longevity is reduced. Either way, bring lots of money for any serious horsepower gains.
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Old 10-01-2015, 05:55 AM
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Originally Posted by gwilliams6 View Post
Having owned both an FD RX7 and a RX8, I would say the FD RX7 has greater tuning potential with aftermarket turbos and more. The RX8 Renesis engine was never designed to be boosted. Many have with some success, but engine longevity is reduced. Either way, bring lots of money for any serious horsepower gains.
Sounds like i want an rx7 then thanks guys
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Old 10-01-2015, 08:44 AM
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Originally Posted by gwilliams6 View Post
Having owned both an FD RX7 and a RX8, I would say the FD RX7 has greater tuning potential with aftermarket turbos and more. The RX8 Renesis engine was never designed to be boosted. Many have with some success, but engine longevity is reduced. Either way, bring lots of money for any serious horsepower gains.
Is the up keep and maintainace for the 7 pretty much the same? Or is there more or less to look out for especially with a slight extra hp build im not trying to build a complete monster just something with a little more pep than my stock 8 maybe faster accel a little more torque nothing too crazy.
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Old 10-01-2015, 08:58 AM
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The FD has 36 vacuum hoses controlling the turbos. If any one of the 72 ends of those lines pops off the mixture can go lean and pop the engine. It's a nightmare. Proper preventive maintenance including silicone hoses, glue, and cable ties reduces the risk.

Also consider the FD is a minimum of ten years older than any RX-8 and produced in much smaller numbers.

The RX-7 is a beautiful and powerful beast. But if it was a girl she might be called "high maintenance". If you are willing and able to give it the detailed attention it needs and spend the money required it will be highly rewarding. If you want something easier to maintain and more forgiving at the limit, go RX-8.

I had two FDs including a CYM R1. I sold them after I bought my RX-8. End of story.
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Old 10-02-2015, 08:07 AM
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Most of the successful FD RX7s on the road today have had major turbo changes from the complicated twin-scroll turbo, to a simpler and larger single turbo setup (much less vacuum hosing). Also most current FD owners have gone with a more efficient aftermarket radiator. Heat was a problem with the FD. Parts are available, but it is not inexpensive to modify and maintain. You could connect with folks on the RX7 club for a better idea of what it would take to buy and modify. Racing Beat, Pettit Racing and loads of others have all the stuff you might need.

After having had to part with my own FD (following a divorce, years ago) , I was a day away from buying a well-maintained 1994 FD with a rebuilt engine (low mileage,with a single turbo setup, and more efficient radiator ,braided lines etc) in Florida for $11,000. Remember these FD were close to $38,000 new. I had a agreement with the owner , but one day before I was to drive there from NJ with the money, someone in Florida with the cash in hand ,beat me to it. So then I went out and bought my 2008 40th Anniversary Edition RX8.

I love my RX8, but still miss the adrenaline rush of the FD. The FD was small and cramped for me, a large guy, 6ft 4in. But that was ok. I felt like I was wearing the car and its responsiveness to throttle and amazingly quick response to steering input were something to behold. I plan on keeping my RX8, it is loads of fun and all paid for, but if the proposed new RX is anything like an FD, I will be also owning one of those too.

If I had the money, yes I would buy a used FD and bring it back to top condition and enjoy the heck out of it ! There are some great FD out there that I see at RX meets and car shows, and they are wonderfully restored and modified and have awesome performance, far beyond what most RX8 mods can achieve.

Last edited by gwilliams6; 10-02-2015 at 08:21 AM.
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Old 10-02-2015, 10:57 PM
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I am at a similar dilemma from time to time, if I should buy a turbo kit for the RX8 or just get an FD as a 2nd car !

Since I'm only aiming around 300whp at max for either car, it's a biiig question since it feels like after reading the forums, 300whp on a RX8 and keeping most of the reliability is not that much of a dream! (Correct me if wrong)

Last edited by zspaun; 10-02-2015 at 10:57 PM. Reason: Addition
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Old 10-03-2015, 07:32 PM
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I think with 300 WHP as the goal, the RX-8 would be my choice. Everything I read (and am planning on doing) says that can be done reliably with the right mods, and the right mods aren't hard to make. Combine that with the fantastic chassis and other factors and it's an easy decision.
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Old 10-05-2015, 10:01 AM
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Yes the RX8 chassis and things like traction control, dynamic stability control, electronic brakeforce distribution, etc. are more advanced than on the RX7.

But the reality is that the Renesis engine already has the highest compression ratio of any NA rotary engine Mazda has made. Then you go and boost it in an attempt to get 300 WHP and this puts enormous strain on the engine and its internals, including all seals. I know there are turbo kits out there for the RX8 and Pettit Racing used to make a well-built supercharger setup. But Pettit no longer makes them after getting bad feedback when those engines didn't last. Of course with any boosted RX8 you have to have greater cooling, free flow exhaust, expert fuel and air management and greater ignition spark to keep the engine together. The Renesis was NEVER designed to be boosted. You will spend a load of money to try and get that 300 WHP and your engine will likely have an early death. Anyone planning to do this should have enough reserve funds for more than one engine.

The difference in the FD's REW rotary engine was that it was designed to be safely boosted by starting out with a lower compression ratio.

I have owned three boosted RX7s (four actual boosted setups). For my original first gen RX7, I had an early turbo system put on its original 12A engine with a water-injection setup to prevent detonation at boost. This pushed the 12A's NA output from 100hp to 200hp. Then later I had Racing Beat totally redo the car for the track and they special built a 13B engine with low compression rotors and race porting and a large turbo that yielded from 350-400+ hp depending on the tuning and boost pressure. Everything in the car's driveline had to be upgraded to handle that power, as well as major cooling system, ignition, fuel system,suspension, brake and exhaust upgrades.

Then I also owned a second gen. RX7 Turbo II with 200hp stock turbo, and then the FD with 255hp stock twinturbo.

The point is you will have to upgrade many major components to make it all work, and even with all that, you should not expect your Renesis boosted engine to last very long.

Last edited by gwilliams6; 10-05-2015 at 12:05 PM.
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Old 10-05-2015, 11:59 AM
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Originally Posted by gwilliams6 View Post
Yes the RX8 chassis and things like traction control, Electronic brakeforce distribution, etc. are more advanced than on the RX7.
Oh hell no! I forgot to mention get a base model RX-8 with no sunroof, no HID, and none of that DSC/TCS garbage.

The point is you will have to upgrade many major components to make it all work, and even with all that, you should not expect your Renesis boosted engine to last very long.
I wouldn't call the radiator, fuel pump, and injectors "many major components".
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Old 10-05-2015, 01:52 PM
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Originally Posted by wankelbolt View Post
I wouldn't call the radiator, fuel pump, and injectors "many major components".
If you're going FI, that's not all you would have to do. 300rwhp NA vs FI is very different with a rotary. I'm guessing that based on the context of the other replies, everyone is talking about FI power.
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Old 10-05-2015, 02:23 PM
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Oh? What else has to be done?
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Old 10-05-2015, 02:45 PM
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Opinions vary but having driven both, IMO the FD is not better in any way than the RX-8, even stock vs. stock. Now of course when talking about modding for power, generally a stock FD is a better starting point than the RX-8 but the price difference of a clean low mileage RX-8 is much much less (like 1/4 the value of a clean FD) than a clean stock FD (super rare) and the FD will be much older so stuff like wiring, etc. becomes an issue.

For the price of a really clean FD you could buy a clean RX-8 and pay to swap in a freshly rebuilt with a single turbo, etc. and be making 400WHP all day long.
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Old 10-06-2015, 04:16 AM
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Originally Posted by 9krpmrx8 View Post
Opinions vary but having driven both, IMO the FD is not better in any way than the RX-8, even stock vs. stock. Now of course when talking about modding for power, generally a stock FD is a better starting point than the RX-8 but the price difference of a clean low mileage RX-8 is much much less (like 1/4 the value of a clean FD) than a clean stock FD (super rare) and the FD will be much older so stuff like wiring, etc. becomes an issue.

For the price of a really clean FD you could buy a clean RX-8 and pay to swap in a freshly rebuilt with a single turbo, etc. and be making 400WHP all day long.
So a 300whp single turbo rx8 with a freshly rebuilt engine + supporting cooling mods would be a viable daily drive for 60k miles or am i pushing it? :p
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Old 10-06-2015, 08:33 AM
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Originally Posted by wankelbolt View Post
Oh? What else has to be done?
Besides the turbo, manifold, IC, injectors, ECU, wiring...

Going turbo isn't trivial.

Originally Posted by 9krpmrx8 View Post
generally a stock FD is a better starting point than the RX-8 but the price difference of a clean low mileage RX-8 is much much less (like 1/4 the value of a clean FD) than a clean stock FD (super rare) and the FD will be much older so stuff like wiring, etc. becomes an issue.

For the price of a really clean FD you could buy a clean RX-8 and pay to swap in a freshly rebuilt with a single turbo, etc. and be making 400WHP all day long.
I know we have a difference of opinion on the 8 vs 7 thing but, you're wrong about something here. You can buy an already single turbo'd car for super cheap these days, even really nice ones. A low mile car would be expensive but a nice FD is not. As usual, buying a modded car straight of the gate is best here. Hopefully one with water injection. In the end, the initial price of the car is probably over shadowed by the price of the single turbo conversion anyway (motor conversion for the 8) so pick your poison. Even buying a v8 swap is cheap (which I highly recommend against, great cars but not for me, just sold mine).

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Old 10-06-2015, 08:42 AM
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Originally Posted by Supernaut6 View Post
Besides the turbo, manifold, IC, injectors, ECU, wiring...

Going turbo isn't trivial.
No kidding. But turbo, manifold, IC are part of the turbo package. My point is nothing "major" that isn't part of the turbo package or the three items that I mentioned needs to be changed. No need to replace ECU, housings, rotors, eccentric shaft, transmission, propeller shaft, differential, drive shafts, gas tank, wheels, suspension, flywheel, clutch, or tires. Of course gauges are a good idea.

OK, clutch and tires might need to be replaced shortly after a successful turbo install.

The turbo package - manifold, turbo, IC, plumbing - plus radiator, injectors, fuel pump, and good tuning on the stock ECU is what is needed. Nothing else "major".
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Old 10-06-2015, 01:07 PM
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Originally Posted by wankelbolt View Post
No need to replace ECU...
No kidding? I thought you would definitely need to replace the ECU.
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Old 10-06-2015, 01:34 PM
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Originally Posted by zspaun View Post
So a 300whp single turbo rx8 with a freshly rebuilt engine + supporting cooling mods would be a viable daily drive for 60k miles or am i pushing it? :p

Single Turbo 13BREW (FD engine) or 13B-MSP (RX-8 engine)? With a solid tune a REW would make it to 60k at 300WHP no problem, a Renesis would be pushing it but I will let you know when I reach 60k,

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Old 10-07-2015, 07:11 AM
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Just my point exactly, the longevity of a boosted Renesis is a huge question mark. While a turboed REW can last much longer.
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Old 10-07-2015, 08:47 AM
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Originally Posted by gwilliams6 View Post
Just my point exactly, the longevity of a boosted Renesis is a huge question mark. While a turboed REW can last much longer.
Thinking about this way to go about it. I've seen many rx8 shells for sale around here and I may pick one up cheap and just go for the rew swap and call it a day. All I want is about 350-375 rwhp out of this platform
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Old 10-07-2015, 09:19 AM
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Keep in mind of course we are assuming all things are equal in terms of build quality. The REW was designed to be boosted so of course it should be more reliable. However, I know plenty of FD owners and all of them have had engine failures at some point. I can think of a handful of completed REW RX-8 swaps that have engine failures already as well. When you push things they break and generally if you have the room to push things you will.
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Old 10-07-2015, 09:37 AM
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Originally Posted by Rkesh88 View Post
Thinking about this way to go about it. I've seen many rx8 shells for sale around here and I may pick one up cheap and just go for the rew swap and call it a day. All I want is about 350-375 rwhp out of this platform
Bingo!
With the inexpensive price of rx8s you'll see this trend continue.
Either with rew, v8s or some type of swap.
It really is the best of both worlds.
And when your bored w/350-375hp you'll have room to grow as where renny takes a dump being pushed that hard.

.
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Old 10-07-2015, 12:54 PM
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Originally Posted by gwilliams6 View Post
Just my point exactly, the longevity of a boosted Renesis is a huge question mark. While a turboed REW can last much longer.
This man gets it

.
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Old 10-07-2015, 01:52 PM
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Originally Posted by firecran View Post
Bingo!
With the inexpensive price of rx8s you'll see this trend continue.
Either with rew, v8s or some type of swap.
It really is the best of both worlds.
And when your bored w/350-375hp you'll have room to grow as where renny takes a dump being pushed that hard.

.
I fell in love with your REW RX8 when i first saw in the classifieds, i think, If i had unloaded my S4 and b5 a4 i wouldve bought it.
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