Laminar's RX-8 EcoBoost swap thread

[Laminar]

No, not that EcoBoost. This one:



I think it's going to work, so I'm going to start a thread.

I want a quick, reasonably efficient, stick, 4 door, fun daily driver. Back in 2015 I put a 302 in an M3 and I've been rocking that for the past 6 years. It's close to what I want, but it's stinky (no cats), hot (no AC), gets 15mpg at best, and the chassis is showing its age. It's an awesome racecar, but not the best daily. Enter the RX-8.





It's nice, but it's not that quick and basically the same gas mileage as the M3 for half the power. But at least the AC works.

My first idea was a Mustang V6 - 300hp, lightweight, cheap. Should be a win, right? Nope! The upper intake is an absolute killer.









No way that's fitting under the hood. Okay, what can I get with a slimmer intake manifold? The GM V6 is fine, but it's been done before. Well, the EcoBoosts have a shorter manifold that sits down in the valley...





I had planned to turbo the 3.7 eventually so this just accelerates my plans.

The 2.7 is nice because:
- Dual injection means I can ignore the direct injectors and run E85 via the port injectors without issue
- Little baby turbos for instant spool
- CGI block is sweet and built for boost
- Lots of instrumentation for data collection

But will it fit? Almost!

Stripped off the turbos, the EGR system, and weighed it. Came in at 366lbs, same as the 3.7. Not bad for having a CGI main structure for a bazillion times more strength.








Went ahead and notched the subframe a bit to give me a little more wiggle room.








Snugged it up against the firewall




The hood almost closes. Without the insulation it'd probably latch. I may have to get the tiniest bit fancy to get some extra clearance.


Started working on engine mounts:










As for the rest of the drivetrain, a few serendipitous things came to light.

The Coyote flywheel bolts straight up:


With the addition of a 3.7 V6 manual block plate and by moving one dowel pin, the V6 Mustang MT-82 bolts right up:




The crank is already drilled for a Mustang pilot bearing. And by using a 3.5/3.7 starter, the flywheel engages and the engine turns over.

ECU will be a Megasquirt. Might work, might not. Initial tests are promising.

Rear end will be Explorer 8.8. I already have one, plus the Ronin axles, I'll adapt it to the subframe myself.



Turbos will have to be rotated down a bit to clear the frame horns and fit in the engine bay. That means I need to source adapters to change the stock turbo o-ring fittings to -AN lines. I also might have to do a scavenge pump because the oil drainback holes are so high in the block.

That's basically where I'm at. I need to get the engine mounts made so I can get that and the transmission into place and move on with the hundred other impossible things to figure out.

[kinger]

Very Very cool!  I thought exhaust manifold fitment with a DOHC motor made this difficult in the 8.  I am a ecoboost fan and the 2.7 is one awesome motor.  You might go over 30mpg when your done with instant TQ in town.  Cool build!

[Laminar]

There’s actually quite a bit of width where the 3.7’s headers go, that was going to be fairly easy to fit up. The 2.7’s driver's side turbo is going to be tricky to fit around the steering shaft.

[Laminar]

Finally wrestled myself out of analysis paralysis and got the engine mounts tacked up.





Ideally the engine would be as far back as possible, as low as possible, and centered in the chassis. I ended up with...not quite that. After notching the subframe, the engine could be dropped low enough that the hood would just about close, though I still expected to have to do something to the hood. But that made the oil pan stick below the subframe like 4"...no bueno. And with the engine centered, there was almost zero clearance on the driver's side for the exhaust/turbo setup with the steering shaft, brake lines, and fuel line right there. So I lifted it up about an inch and scooted it toward the passenger side about as far as it would go.

This gives me a bit more ground clearance and it won't hurt me up top too badly since I'm going to have to modify the hood anyway.

And now I have a fighting chance of fitting everything in on the driver's side around the steering shaft. I'll still probably have to reroute the brake and fuel lines just because they probably shouldn't be 0.25" away from a glowing hot turbo.







I also just remembered that with the engine centered, the A/C compressor on the passenger side wanted to send the lines straight into the frame. Now that I've cheated it over there an inch or two, it's gonna be a bear to fit. There's going to be some notching.

[kinger]

Super tight on sides, then look in front LOL tons of room there, fun to see one less cyl in front.  You have your work cut out! 

[Laminar]

Super tight on sides, then look in front LOL tons of room there, fun to see one less cyl in front.

I was trying to get it back far enough that I don't have to push the steering rack down too far. We'll see how it lands there. I'm also "ruining" the perfect RX-8 chassis balance, so I'm trying to keep that weight rearward.

Once I start with the turbo piping and airbox and radiator and fans the front end is going to be filling up quick!

You have your work cut out!

I try not to think about it too much. 

[kinger]

Super tight on sides, then look in front LOL tons of room there, fun to see one less cyl in front.

I was trying to get it back far enough that I don't have to push the steering rack down too far. We'll see how it lands there. I'm also "ruining" the perfect RX-8 chassis balance, so I'm trying to keep that weight rearward.

If by "ruining" you mean instead of them rotting a pasture with a dead rotary, they are roaring down the road, making 2x mpg, 3x power, and handling impacted so little that a only a professional race team could tell, then yes carry on soul crusher...

[Venom13132]

 

If by "ruining" you mean instead of them rotting a pasture with a dead rotary, they are roaring down the road, making 2x mpg, 3x power, and handling impacted so little that a only a professional race team could tell, then yes carry on soul crusher...

 

[Laminar]

Every day I wonder if I shouldn't have just done the smart thing and tossed in a 5.3, but I have to keep reminding myself that this is going to be a blast and turbo noises are fun.

Here's where the oil pan ended up, it's about 2" below the crossmember. I'll probably put a skid plate on to protect the plastic oil pan. The 60 degree V angle helps with the extreme width of a DOHC engine, but it pushes the intake up since there's less room in the valley. That's where the LS engines are nice - everything is all low and compact.

[kinger]

Yikes that is no good.  I noticed scratches on my F body pan the other day and it doesn't stick down at all.  Its hard to beat LS, the design is just so compact.  Easy to see why they are popular to swap especially after seeing these pictures.  Thanks for sharing.

[Laminar]

I mean, I could always go dry sump. Anyone want to give me like $3k? 

[Laminar]

Got the transmission (almost) mated up. For the surfaces to actually touch, the engine would have to aim further down than it can right now without hitting the firewall. The mounting boss for the shifter is hitting on the top of the tunnel.

Lots of room on both sides, but to get the top clearance I'll need to either drop the engine an inch or so, clearance the trans tunnel, or cut off the boss since I'm planning to hard mount the shifter anyway.







I'm leaning toward dropping the engine an inch. This gives me more cowl clearance and more turbo clearance on both sides.

I'm also considering hacking off the HPFP. It's driven off of an extra cam lobe on the rear of the passenger exhaust cam, so it's pushing the engine an extra inch or so off of the firewall. With that gone, I'll likely gain quite a bit of steering rack clearance.

I already yanked the vacuum pump off of the driver's side head. In both cases, I'll need to block off the oil feed and make some sort of cap to cover the back of the head. In the case of the HPFP, I'll also have to figure out how to/if I can lop off that cam lobe without destroying the engine.

I also measured from the trans to the shifter hole. As it sits, the shifter linkage will need shortened by 3" to make the shifter land directly in the hole. That's not bad at all.

[Laminar]

Continued tinkering over the weekend. Cut the tacks on the engine mounts and repositioned the drivetrain. I ended up pulling the HPFP off so I could get the engine further back toward the firewall. I'll have to make a cover for that eventually.

Covered the exposed cam lobe in blue tape:


Getting the coolant line from the back to the front will be fun. The NA engines take the coolant up through the valley and have tall intakes as a result. The EcoBoosts take it parallel to the intake up above the valve cover.


Got it level to within a couple tenths of a degree side to side, currently sitting at about 3ish degrees sloped back. This was as low as I wanted to put the engine/oil pan while still maintaining a little bit of clearance for the top of the trans in the tunnel. To reduce that slope, I'd have to either drop the engine more, or clearance the tunnel. I'll have to be intentional about where I set the diff to make sure the u-joints are happy.


With that set in place, I started on a transmission mount. I'll probably have to end up welding something to the body to bolt the transmission crossmember to. This little bracket will hold the transmission in place and also serve as a solid mount for the shifter. In stock form, the shifter mounts to the body and connects to the trans with a linkage and rod. I'll solid mount to the transmission, which should help with shifts under power and some of the other poor shifting characteristics that the MT82 sees in stock form.

[digitalsolo]

What do you do with the HPFP if it’s not in that spot?

[Laminar]

Not use it. 

Direct injection means using the factory ECU and all of its...limitations. My plan is to run off the port injectors only and leave the DI system closed.