Sourcing K series long block for RX-8 swap

[reklipz]

So, I've mentioned this in passing in the recent past; my buddy is looking to swap a K series Honda engine into his RX-8, replacing the stock 13B-MSP Renesis it came with. I believe this has been done before, but the technical details of the process aren't really why I'm making this post. That said, don't let that keep you from chiming in; talking about this stuff is fun.

The goal of the swap is to achieve around 400 WHP, most likely with a turbo charger. He's wondering if, when built up to 400 WHP, the amount of torque from a K24 build would be too great and require reinforcing the drive train. The plan is to maintain the RX-8 drive train from the transmission back, including the carbon fiber drive shaft.

Anyway, he's fairly settled on the K20A2 as the base, though I believe he could be persuaded otherwise if the knowledge was presented. Locally, we've found a single K24, and plenty of K20A3s (economy VTEC).

It looks like we may have a K20Zx nearby, and I recall reading that the K20Zx (I believe they were comparing the Z3) platform is even better than the K20A2, due to a better flowing head. I see that the redlines and fuel cut offs are higher, while everything else from a bird's eye view seems the same.

Neither of us have ever performed a swap before, but we have lots of "american muscle" expertise we can tap, though they're rather bashful when it comes to anything import. What advice can you share regarding our ambitions? There's lots of things that haven't been addressed in this thread, like dealing with the intake and exhaust, electronics, or mating with the existing drive train, but those are things we'll have to tackle as the build progresses. We're mainly concerned with choosing an engine at this point, leaning toward a K20xx with "performance" VTEC.

I put this thread in the "other automotive" section, with the potential expense of it not seeing the light of day. If it's suitable for one of the "technical" forums, please feel free to move it so we can get some more eyes in here.

[Jarrett]

I know you didn't create this thread to hear all of the reasons that this shouldn't be done. But...

The factory transmission in those cars can hardly handle the factory power outputs. It's a 6-speed which is great for highway driving but not much else. Anyone who does anything serious to these cars puts the 5-speed from the FD3S into them That transmission is pretty stout. It's not a direct swap in and of itself but it's the closest thing there is to a direct swap.

If turbocharging is already on the table then why the heck not just boost what's already in there. Build it up and boost it. Or, put the FD3S 13B in it. They can be had for dirt cheap from importers. Of course you should rebuild them but it's not a ton of money when you're comparing it to swapping a K-engine in.

[reklipz]

Not trying to inflate my post count, just separating thoughts:

It appears the K20Z1 and the K20A2 are virtually the same, except the K20Z1 has the exhaust camshaft from the ITR (Integra Type R, presumably). Now, I must be ignorant, because I thought the USDM Acura RSX was the Integra... so the engine having it's own exhaust camshaft is a bit tautological. Can someone explain this?

In any case, the K20Z1 seems to be a better buy than the K20A2. Further, the K20Z3 seems fairly similar to the Z1 (and therefore the A2), except it has the camshafts from the A2, and possibly a different port pattern on the intake. It's so hard to get accurate information from forum threads; everyone speaks in terms of the car that the engine came from, rather than by the engine code.

[reklipz]

I know you didn't create this thread to hear all of the reasons that this shouldn't be done. But...

The factory transmission in those cars can hardly handle the factory power outputs. It's a 6-speed which is great for highway driving but not much else. Anyone who does anything serious to these cars puts the 5-speed from the FD3S into them That transmission is pretty stout. It's not a direct swap in and of itself but it's the closest thing there is to a direct swap.

If turbocharging is already on the table then why the heck not just boost what's already in there. Build it up and boost it. Or, put the FD3S 13B in it. They can be had for dirt cheap from importers. Of course you should rebuild them but it's not a ton of money when you're comparing it to swapping a K-engine in.

Jarrett, this is perfect. Anything goes in this thread.

We're well aware of how temperamental the RX-8 6 speed transmission is. Deev describes it as being made of glass, and we'd already done some research and discovered the same. That's exactly why I mentioned it, actually. I'm acting more of a liaison here, just along for the ride and there to help with the build. Ultimately, it's his car, and I'm just conveying thoughts here. Currently, fourth gear is being temperamental and always grinding; this is just the synchronizer as far as I'm aware. My buddy has tracked down a transmission that he is suggesting on cobbling parts out of to make a single "best build" of both; retaining the stock 6 speed transmission. I'm not sure of his thoughts on swapping to the (third generation, apparently) RX-7's 5 speed.

It looks like the biggest concern with swapping transmissions is due to the cost involved, particularly with replacing the drive shaft.

As for sticking with the Renesis, the whole point here is to eliminate the maintenance hassle associated with the engine. I assume the same goes for the prior 13B-REW.

[Jarrett]

And he feels that a K-series engine turned rear wheel drive mated to a foreign transmission with a home-built wiring harness running 400hp worth of turbocharged boost is a better alternative in the reliability department?

I've decided this is a troll post. GeoffM must have hacked your account reklipz. I'll sort this out for you.

[reklipz]

I don't see how you can consider a post asking for information regarding a goal trolling. Perhaps we're out of our minds, but we're not trolling. Obviously we're not shooting for 200 extra HP from boost alone. It's my understanding that, with the K20, there is lots of power to be gained from your typical bolt-ons alone, and even more with a port and polish along with proper a proper tune.

As far as the reliability of a custom wiring harness and mating plate/bits for the drive train, you seriously doubt that these things can be done reliably? These are essentially zero-wear components; done properly, they will be reliable.

Finally, I don't see how RWD vs FWD plays into the reliability argument.

Don't shoot us down because the goal seems outlandish. Tell us why and how the goal is outlandish, and then let us grok that information and try again.

/me anxiously awaits GeoffM's punishment;

[NAiL05]

I would keep the REnesis rotary. Change out the seals and run a turbo on it. IT will make more power than the k24 and rotaries push air like no other engine I have felt. Hence why such a small motor can run such a big turbo charger. The downfall of a rotary other than emissions is heat...They generate a lot of it.

[Quashish]

And he feels that a K-series engine turned rear wheel drive mated to a foreign transmission with a home-built wiring harness running 400hp worth of turbocharged boost is a better alternative in the reliability department?

I've decided this is a troll post. GeoffM must have hacked your account reklipz. I'll sort this out for you.

haha

I don't know much about the rx8 but that it's a 1.3 rotary. Right there got me wondering why you would try to put a 4 cylinder honda vtec engine to the transmission meant for the rotary.

I've also heard they rev super high. Idk I imagine getting the ecu to work right with a lower revving engine, and getting the vtec to work would be a huge kick in the trousers. assuming you could mate up the engine and trans.

It just seems complicated and unnecessary. I think this is a bigger undertaking than you and your friend imagined.

[Accrdwgnguy]

Anything is possible with some fabrication skills.

[NAiL05]

That is going to need a lot of fabrication...eff it just put a 3 rotor in there. Makes life easier. I remember quite a while back when they first came out and someone decided to put a 20b turbo in an rx8...quite fast

[Xsjado]

I guarantee you pull out of this, your better off with a 2jz and 2jz gearbox.

still be a piece of crap when finished.

He should just buy another car, are there no decent rotary mechanics nearby?

There are many aftermarket options for gearboxes while your just throwing money away.

as for a 3 rotor a guy in the u.s spent close to 100k to get it done, what a nightmare.
why not got for 600 atw.

[Madpol]

iv'e said it before in another thread...if you can put a V8 into an old school mini and make it rear wheel drive you can do anything lol
http://www.youtube.com/watch?v=lh1DoGzHFl4

or a Hayabusa mini rear wheel drive
http://www.youtube.com/watch?NR=1&v=...I&feature=fvwp

[gloryaccordy]

If cost is a concern you might as well nip this project in the bud

[Xsjado]

http://www.wirewheel.com/Dempsey-Rac...e-in-soon.html

this will probably save you a lot of money.

http://www.wirewheel.com/1997-Acura-NSX-GT-2.html

[oni_cb7]

It's really not that hard. You just either need an adapter plate between the transmission and the motor. Or a custom bellhousing on the transmission. Both options will require someone who knows how to make these custom pieces. (I've spoken to a guy in california that can build adapter plates to mount a small block chevy motor to a stock early 70s datsun truck transmission). Speaking of california, I hope you don't plan on trying to do this if you live in california.

As for the motor... I'd just go for an s2k motor. It's reliable. Decent gas mileage (if you stay out of vtec). Plus, they are fairly affordable (I just found a complete s2k motor for 2800). And this will keep with the high revving nature of the rotary motor.

The k series motors should be easy to find. I've seen those in junkyards before. Good thing honda put it in everything.