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RX8 13B Engine into a FD RX7

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Old 04-10-20, 08:41 PM
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RX8 13B Engine into a FD RX7

Hey

As 13BREW's become rarer and more expensive, I'm wondering if anyone has actually attempted to put in a Renesis 13B engine into an FD?

It's obviously NOT the perferred engine, with reliability, design issues and a performance disadvantage to the FD's 13BREW.

But, it might be a future alternative to keeping the FD on the road, with a rotary?

SORRY if this has been covered - I did search.
Old 04-10-20, 09:00 PM
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Not sure if you are aware but you can still get a new REW engine for under 5k.
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Old 04-10-20, 09:16 PM
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Originally Posted by Johnny Kommavongsa
Not sure if you are aware but you can still get a new REW engine for under 5k.
Yeap.

It's more thinking in 10 years time, for guys keeping their FD long term.
Old 04-11-20, 07:45 AM
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Rebuilds are very affordable. I'd avoid the MSP engine at all costs unless it was going to be an NA 3 rotor. Boost and an MSP is like swimming against a current imo.

Last edited by fendamonky; 04-11-20 at 08:07 AM.
Old 04-11-20, 08:11 AM
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(Renesis) "reliability, design issues and a performance disadvantage to the FD's 13BREW"

that may be the greatest understatement ever on our board...

looking down the road good old capitalism will provide the answer with non OE 13BREW substitutes.
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Old 04-11-20, 09:09 AM
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Originally Posted by AndyMac
Yeap.

It's more thinking in 10 years time, for guys keeping their FD long term.
Mazda has a whole engine factory that is tooled up to do the FD and Rx8 engines, so since that is all that building can do, that is what they have been doing with it... until they retool it, or tear it down, REW supply will be good.

as an aside the Rx8 engine in the FD would be really fun, its like an Rx8 that is 500lbs lighter...
Old 04-11-20, 12:44 PM
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I agree that an FD with RX8 13B-MSP, 6 speed and 4.77 rear would be a really fun car.

But a big let down when coming from a fully functioning FD.
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Old 04-11-20, 12:51 PM
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Originally Posted by BLUE TII
I agree that an FD with RX8 13B-MSP, 6 speed and 4.77 rear would be a really fun car.

But a big let down when coming from a fully functioning FD.
ive been sort of tempted to do an NC miata with an Rx8 engine, its almost a bolt in, but i just don't like the NC miata!
Old 04-11-20, 01:56 PM
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^^
Exactly!
I had same thought process and ended up at the same conclusion.

NA swapped FD would also be about the same weight as NC Miata since you take ~200lbs of turbo/turbo support rubbish off the front end.

In the end, the FD just looks better
Old 04-11-20, 04:43 PM
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we did a Nasa race of Mazda challenger race challenge (it was something like that), and the cars were all 6 speed NC cup cars, 2650lbs. that is like turbo FD territory... the ND cup car was 2 seconds faster at laguna too (this was 2015, so before the ND was on sale) the door was $1600!

<edit> Mazda race of NASA champions, race



Old 04-11-20, 06:04 PM
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AndyMac,
You done woke up all the forum's heavy hitters

A LS V8 swap would be better use of your $$$

Last edited by Nakd n Fearless; 04-12-20 at 05:50 AM.
Old 04-12-20, 10:17 AM
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The RX-8's engine is a pretty peaky non-turbo engine. Doesn't have a lot of low-end power. The FD's twin setup fills in a lot of torque down low.

Also the RX-8 is only about 200-300 pounds heavier than the FD. Mazda still does an amazing job of saving weight on cars.

All that said the RX-8 engine is pretty much strung out where it is. Bolt-ons will only make a small amount of extra power (like 5-10hp), even porting doesn't add much power. A simple downpipes and cat-back on the FD will add TONS more power. Also the RX-8 doesn't respond well to turbos, it has to be a VERY mild turbo or the engine will be a hand grenade. There's a reason RX-8 guys do REW swaps if they want to make power.

I did see an FB at DGRR one year that had a full RX-8 engine swap - all the manifolds, everything working. That would be a fun time in a 2100 pound FB and suits that car well.

Basically, it's not worth swapping in an engine that makes less power and has far less potential to make power when modified.

Dale
Old 04-12-20, 12:33 PM
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Originally Posted by DaleClark
Also the RX-8 is only about 200-300 pounds heavier than the FD. Mazda still does an amazing job of saving weight on cars.
Dale
they do, the Rx8 is like 18" longer than the FD, and has 47 airbags, and all the other modern distractions too, its really light for what it is.
Old 04-12-20, 01:19 PM
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Originally Posted by j9fd3s
ive been sort of tempted to do an NC miata with an Rx8 engine, its almost a bolt in, but i just don't like the NC miata!
Here's one done by FEED, at the 2:00 mark if the link doesn't work:

Old 04-12-20, 01:42 PM
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see it seems pretty good, 1080kg is good too
Old 04-12-20, 06:50 PM
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300 lbs of weight difference. The Rx8 is a damn cow, better balance on corners though.

Last edited by Red94fd; 04-12-20 at 06:53 PM. Reason: Spellcheck
Old 04-13-20, 08:59 AM
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In the RX-8's defense I wouldn't call a 3000 pound car a "damn cow" - most modern cars are WAY above that. The FD is about 2800 pounds give or take with options. The one thing the RX-8 has going for it for sure is it really has a great chassis and handles well.

Dale
Old 04-13-20, 09:48 AM
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+1 the average new car weighs as much as a small moon. the Dodge Challenger is 5,500lbs! even the 1983 Mercedes its based from was only 3500lbs..

Old 04-13-20, 10:00 AM
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I have brand new Mazda oem 13brew motors for $4699.I sell RX-8 msp Reman motors for $4399 currently. There was recently a significant price jump on the msp motors, while the rew motors have held relatively consistent over the past few years. In my opinion going with the msp motor would be a significant downgrade. rew motors from the factory typically dyno at 215-220hp while msp motors struggle to make 180hp. The msp motors were built for cost savings and emissions. The housings tend to wear out much quicker than in an rew motor. The mounting is also completely different as they mount by the center iron like the fc motors vs the rear. There are plenty of rew motors available as well as much aftermarket support.
Old 04-13-20, 10:53 AM
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Ok ok ok baybe not a cow but 3000 with 180-190 whp max and torque? Its getting there.. if you have a passanger and hit the gas you will know the dissapointment. Makes you want to get out and start pushing that sucker.. lol I know it..
Old 04-18-20, 08:16 PM
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Originally Posted by j9fd3s
ive been sort of tempted to do an NC miata with an Rx8 engine, its almost a bolt in, but i just don't like the NC miata!
There's a guy that just recently did this for a customer. Said it was a huge challenge and pain in the ***, but the car runs great.
Old 04-19-20, 08:40 AM
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Originally Posted by gmanpie
There's a guy that just recently did this for a customer. Said it was a huge challenge and pain in the ***, but the car runs great.
i think it would, you're either removing 500lbs from the Rx8, or adding 60hp to the miata... the two cars are built on the same chassis, so most things swap over, and crucially in California, all the emissions junk (leak detection pump, etc) is the same between the two cars, so that would work too.

hard part is the wiring, and that you need both cars
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