Automotive ADD: Engine swap edition

So I have this RX-7.  I killed the awesome bridge ported 13B and built a semi-experimental street ported "6 port" engine for it.  (In quotes because the secondaries and aux ports have been opened up to one massive port, with epoxy filling in dead areas).  But I also want things like quiet, and ability to drive long distances, and good emissions, so I have been planning/accruing parts for various swaps.

I mean, okay, I do have a complete rotary to T5 adaptor set complete with RX-4 bellhousing and Mustang V8 trans, so that kind of marries me to rotaries for something.  And what I think is a Turbo II bellhousing with a Jerico adaptor on it, and a T56 adaptor.

But, I also want to put an LS4 in something RWD, because LS4s have good heads and stuff and are CHEAP used because the blocks are allegedly worthless unless you have a Grand Prix.  But I am fairly sure I know how to make one RWD, with several trans options.  Also, I have a Chevy engine to BOP trans adaptor, and BOP TH350s/400s are cheap to free, and I have those 2.lol gears for the 9" so who needs overdrive?  Oh, and that LS3 oil pan/pickup, which I originally bought for a theoretical LM4 swap, but LS4s are even cheaper than LM4s.

I also really like the idea of a 2.5 Duratec with ITBs.  This should be doable easily with a 5 speed NC transmission so I can stick an RX-7 tailhousing on it, might even be able to keep the cable driven speedometer.  ITBs are readily available.  And I have all the RWD specific Duratec bits on hand.   But this would require a higher end Megasquirt than the MS2/Extra already in the car, and nothing against MS at all but I kinda also want generic OBD-II data capability for in car camera overlays, which requires an OEM-like computer.  Which brings us to...

Ecoboost.  Okay, it's a turbo, and turbos suck, but there is something compelling about the idea of a junkyardable drop in engine, and the Ford controls pack costs about what a VVT-capable Megasquirt costs and no dyno time required.  But, turbos suck and RPM rules.  Which brings us to...

Honda K24A2.  These are also really cheap on eBay, and looks like a sure way to get that 250-280 crank HP that I'm after with little fuss.  Adaptors exist for NA/NB Miata transmissions and, again, a Miata 5 speed is a tailhousing swap away from bolting in to an RX-7 with no fuss.  And NA/NB trans are way cheaper than NC to boot.

But if we're talking Honda, my favorite Honda engine of all time is the J-series V6, for its smoothness and incredible ease of service.  And, wouldn't you know it, swap bits for these into Miatas exist too.  The ugly part of this swap is these engines don't have mounts, they hang entirely off of the trans with a little snubber mount on the front of the engine that does practically nothing, so I don't know how these would work in RWD form.

You know what would be an even easier swap though?  Renesis.  I already have a subframe that mounts the engine off the middle, I already have an RX-8 header, and I already have a single-pipe Racing Beat exhaust that should be adaptable.  And MS2/Extra will natively read the RX-8 trigger wheel and control the injectors and coils, so no electronics needed.  But emissions...

I like the 2.5 duratec swap. 

In reply to dxman92 :

I figure it would be about $300 for the engine, $600 for the first transmission (consumable, Mazda smoothcases are not strong), $300-400 for the clutch and flywheel, $800 for the ITBs, $??? for the necessary airbox, $150 for a Honda S2000 exhaust manifold (can be tweaked to suit the Duratec), and $1600 for the computer.  So, uh, probably over $4000.  Plus who knows how much dyno time to get the VVT optimized.

Which is where I start thinking about other things, like buying an entire ratty S2000.

Yes, it would be cheaper to use the existing computer and blank off the VVT, and use a MX5 intake instead of ITBs, but blanking off the VVT negates most of the advantage of the 2.5, and ITBs are waaaay worth it as far as throttle response and aural pleasure are concerned, so in my mind these are non negotiable.

And I thought I had issues. 

What are your hp goals?

A gm 60 degree v6 isn't too difficult and the engines are cheap.  The 3500 has 205 hp stock.

The Buick 3800 makes around 220 hp stock.  Both engines are fairly straight forward to use in a rwd configuration and have the wct5 for trans.

Just a thought.

In reply to wvumtnbkr :

Somewhere between 250 and 300hp with redline at 70-80mph in 1st or 2nd gear, with as much RPM as the engine combination will accept since RPM is more easily pedaled.

My LS4 thoughts involve/require removing the rotating assembly and inserting 4.8 bits, for example.  A RWD crank is required anyway, may as well put in a good one.

A cammed 3800 does sound really nice, but I'm still partial to the 3100/3400.  But the only good cams for those are flat tappet since there isn't room for a roller and high lift at the same time,  But thanks for the reminder anyway...

Interesting timing on your post.  I am looking to resurrect my 1st gen street car and considering options.  I'm a rotary fan, but I'd kinda like some torque and better mpg's, plus need to pass visual inspection for emissions and would greatly prefer it meets reasonable emissions standards.

Here's my list:

s5 TII - have one sitting on the floor next to the car - am a little leery of reliability and fussiness for that vintage and complexity.

Renesis - I have friends who have installed renesis with MS2 into IT7 cars, so I think I could follow that route without too much trouble - would need more streetable motor mounts, and a different exhaust header solution since the stock manifold fouls the passenger footwell.  Doesn't really deliver on torque or mpg's, but I think it would be a riot with 4.44 gears, 9k redline, and about 90hp gain over stock.

Miata 1.8 turbo - I think I would really like the character of this engine, but it looks like no one has really done this swap.  I'm assuming there's a reason for that.  Plus costs would be quite steep with a FM turbo kit.

LFX - This is the wildcard option: GM 3.6L - ~320 hp and 7600 rpm redline.  Reasonably cheap and plentiful.  V8 roadsters has a kit for a miata  - could probably leverage some of their work for ECU and intake manifold, etc.  No idea how well it fits around front cross member/steering or a transmission solution.  Has exhaust manifold built into head, so exhaust should be very straightforward - single pipe for each side - no fancy custom header required.  They have gotten favorable press for exhaust note (in Camaro's) in online reviews.

In reply to sevenracer :

I really like the BP turbo option for a daily driver vehicle, but I don't like it so much as a competition engine - I do not like turbos.

I'm also a huge fan of the High Feature V6, but LFXs locally are crazy expensive.  I was told here that you can find them for cheap "all day long" in Texas, with no further explanation/direction.  I can't find a phone number or website for "Texas" and have no idea if they ship, and eBay searches prove fruitless.  I've tried to buy engines long distance from salvage yards on car-part.com and found that the majority of them have zero interest in shipping (even though they might say they do) and the rest all claimed that they sold whatever several months ago but haven't bothered to update inventory.

TDI, it's the engine an RX chassis has always deserved. 

Torque. You want it. That'll work nicely with the tall rear gear you plan to use.

Also, just get the LM4, not the LS4. It's already set up for RWD, and with the amount of work required to get the LS4 ready it's a wash financially.

Patience will get you a complete running LM4 donor with 290 hp for less than $800.

There's lots of reasons why the LS engines are all the rage right now for swaps. It just makes sense.

Edit: also, you threw me for a loop with the avatar change.

What are the options for a manual behind a LFX?

Indy-Guy said:

Torque. You want it. That'll work nicely with the tall rear gear you plan to use.

Also, just get the LM4, not the LS4. It's already set up for RWD, and with the amount of work required to get the LS4 ready it's a wash financially.

Patience will get you a complete running LM4 donor with 290 hp for less than $800.

There's lots of reasons why the LS engines are all the rage right now for swaps. It just makes sense.

Edit: also, you threw me for a loop with the avatar change.

Oh I like torque, but I prefer it at 8000rpm 

The HUGE advantage of the LS4 is that it does not use a throttle control module, the PCM directly takes input from the APP.  One thing I'd want to try to do is play with throttle mapping so that the engine doesn't feel like it has a 50lb crank and tons of engine braking.  If you try to do that with the early PCMs (P01?) you can easily brick them.

Of course the real fix is to blank off one bank of the engine and run it as a 2.4l four, which is also something I'd like to do.