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Bought a 2004 rx8 that won't start. thinking about putting a ls2 in it.

Old Oct 31, 2014 | 01:41 PM
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Bought a 2004 rx8 that won't start. thinking about putting a ls2 in it.

Anyone have any thoughts on the build?
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Old Oct 31, 2014 | 01:56 PM
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If you have an extra $20k laying around you want to burn, go for it. It's been done. Now, you better run before the others get here and flame the crap out of you.
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Old Oct 31, 2014 | 02:06 PM
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I hear Isuzu makes some pretty good engines.
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Old Oct 31, 2014 | 02:11 PM
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No flaming allowed in the new member forum.


That being said, you won't find people that are just going to give you a thumbs up.

Basically, the RX-8 is a terrible platform from an ease-of-swap perspective. Not only is the factory engine in a spot that other engines can't be in (which means you are custom rebuilding most of the front of the car's subframe, suspension, steering, etc...), but EVERY electronic component in the RX-8 is run through the factory ECU. In order to have a seemless swap that isn't like driving a pile of electronic spaghetti or a christmas tree of warning lights, you will need to design/develop/write custom electronics modules to communicate with everything OR find aftermarket replacements for everything. This is where most builds end up bogging down and either stalling completely or their owner claiming it's "done" as long as you don't get within 50 feet of the car.

This is all on top of custom everything else: exhaust, cooling, oil cooling, ppf, mounts, wiring harness, driveshaft, etc...

There has been ONE LS swap that actually reached the full "completed" stage, done by TougeFactory as a "cost no object" swap, and it was up for sale a month later for $69k, and it still hasn't been sold to my knowledge, several years later.

So if you have LOTS of cash laying around, you have a fair shot at getting it done if you spend all of that plus however much you can scrape together. Every single person that shows up on the forum posting about it and thinking it's a simple/cheap/easy swap has proven how misguided they were (Even if they still don't realize it).

The easiest engine swap available, if you want more power, is to swap to an REW. That is ~$12k, and can be ingrated with the electronics fairly easily.

Alternatively, the easiest, and cheapest, swap possible is to swap the chassis, and just trade the car for something closer to what you want. Seriously.

Feel free to try to prove us wrong. We keep waiting for someone to do so...11 years after release, and no one has yet.
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Old Oct 31, 2014 | 05:03 PM
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Well I happen to have just the right stuff laying around to do it I'll be pulling the ls tomorrow. I'll post pics to keep you guys updated and to prove you wrong
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Old Nov 1, 2014 | 01:13 PM
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Here's what I'm starting with. About to pull the motor out of the gto now
Attached Thumbnails Bought a 2004 rx8 that won't start. thinking about putting a ls2 in it.-20141019_181508.jpg   Bought a 2004 rx8 that won't start. thinking about putting a ls2 in it.-20141101_110438.jpg  
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Old Nov 1, 2014 | 02:19 PM
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Well, at least the seats are the right color to hide the result when the bills start becoming overwhelming.


J K. Hope you have the patience, knowledge, perseverance, time, facilities, equipment and capital to pull it off and a sufficient sense of humor if it doesn't work out as planned.
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Old Nov 1, 2014 | 02:43 PM
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I'm sure I do. I'm not exactly inexperienced and this definitely isn't my first ls swap. But thanks for the encouragement!
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Old Nov 1, 2014 | 03:15 PM
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I have to do one last push to convince you to not attempt it.

Have a look at the Frankenstein RX-8s Subforum

You'll notice quite a few build threads that just go silent at some point through the build. Most that attempt a swap with a non-rotary never get anywhere near a completely functional product. If you intend to only run this car as a full race car, going with zero factory equipment it becomes a much more reasonable project. If you do that then it's no different than any custom race car build.

If you intend for this car to be streetable, let alone completely legal there are massive hurdles to jump over that RWWIP went into a little bit. Quite a few of them have to do with the fact that most of the factory diagnostic components would need to be functional to be legal in most of the US.

I'd really like to know what your goals and expectations for the car are. Allot of the people that attempted it started out looking for completely unreasonable things (400hp LS1+Rx8 handling, daily driveable+400hp, Rx8 handling+torque, etc...)

Good luck, be sure to let us know how it goes.
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Old Nov 1, 2014 | 03:33 PM
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My goal is a 900hp daily driver.
If I can afford to do this & in 3 weeks, I can handle a little rx8.
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Old Nov 1, 2014 | 03:34 PM
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Sorry, the picture didn't post in my last reply.
Attached Thumbnails Bought a 2004 rx8 that won't start. thinking about putting a ls2 in it.-20131030_155433.jpg  
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Old Nov 1, 2014 | 03:35 PM
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There seems to be a surge of new LS Swap RX8 projects. It seems like the best place for information so far is the LS Powered RX8 group on facebook.
I'm working on swapping an LS3 with the V8 Roadsters kit.
Are you using a kit or are you making all of your own components?
Interested to see your progress, best of luck.
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Old Nov 1, 2014 | 03:38 PM
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I'm doing it all myself. And btw, the motor in the last picture I posted makes 2000hp.
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Old Nov 1, 2014 | 03:44 PM
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And thank you
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Old Nov 1, 2014 | 04:03 PM
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Originally Posted by TurboLS2rx8
My goal is a 900hp daily driver.
If I can afford to do this & in 3 weeks, I can handle a little rx8.
Way to make people doubt you.
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Old Nov 1, 2014 | 04:04 PM
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Originally Posted by Legot
Way to make people doubt you.

lol! And what have you built?
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Old Nov 1, 2014 | 04:21 PM
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If you have the money and skill to build that, then you might have a fair shot at this. Not the typical 16yo kid that doesn't even know what a proper 250whp is and only has access to an iPhone.

Good luck. If you want to start a build thread, feel free to start it in New Member subforum and I'll move it over to the right subforum for you.
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Old Nov 1, 2014 | 04:29 PM
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Thank you, I'll go ahead and start one
I have plenty more street car builds I've done that I can post if anyone wants to continue to doubt my experience.
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Old Nov 1, 2014 | 04:32 PM
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No one believes anything posted on the internet. Or everyone believes everything.

Trying to convince people of what you might be able to do is largely pointless, it's best to just go do it.
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Old Nov 1, 2014 | 04:34 PM
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Very true. I'll get on it
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Old Nov 1, 2014 | 05:48 PM
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You seem a little quiet Legot? :0
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Old Nov 1, 2014 | 10:19 PM
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Believe it or not, I don't really care...
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Old Nov 1, 2014 | 11:21 PM
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It just occurred to me: why a LS2? Why not wait a bit and install the modified hemi from the new Hellcat? At roughly 700 horsepower, it would get you closer to your 900 HP goal in the first stage.
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Old Nov 2, 2014 | 12:11 AM
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Originally Posted by Mysterion
It just occurred to me: why a LS2? Why not wait a bit and install the modified hemi from the new Hellcat? At roughly 700 horsepower, it would get you closer to your 900 HP goal in the first stage.
Because hellcats are junk. That's why.
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Old Nov 2, 2014 | 01:26 AM
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Let me get this straight....the motor from a discontinued product line of a company teetering on the verge of bankruptcy has more going for it than one of the best selling and most coveted engines on the market today. Is that what you are saying?


Last edited by Mysterion; Nov 2, 2014 at 01:30 AM.
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