EFI Boxer

I've mostly punted on seriously addressing the filtering / temp / weather protection. Honestly, I didn't want it to sway me from the tall vertical stacks, so I only really just poked at it a bit. I've posted some options before, some more discreet, some more akin to the Koenig cars.

With the stacks being offset (unlike the BB cars which were centered), I was thinking of designing roof scoops a la the early Series 1 cars. They're essentially skinny versions of the Koenig scoops. Maybe these skinny ones have slightly bette rear visibility than the Koenig scoops?

If I went this route, I'd likely nix the existing trumpets, and make a new set of trumpets that incorporated the lower plate. Obviously, the engine lid cutout is much larger on the BBi than shown here, so I'd have to address that as well.

Currently, the stacks are just sticking out the top of the engine lid. So obviously, that's not a long-term solution...

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What is this referring to?

 

Considering just how much straighter and larger these intakes are compared to stock, I have to think it's a huge improvement in breathability (even though the head inlets are still going to be a choke point). I can see the point about the filters disrupting flow though.

I'm going to try and design a roof scoop option. I'd regret it if I didn't at least try. There's a more discreet option as well that would pull air from the rear a la the carb cars. I can always fall back to that option. Neither involve the filters being in the trumpet.

 

That's okay, we're just spit-balling here. Any alternative your prefer? I think the roof scoop crowd has been the most vocal, that's why I ask.

 

Status update.

She runs! The car started right up on the previous plenum based tune. Idle was actually pretty good. I believe this has a lot to do with the addition of the IACV. Using a synchrometer (same used for balancing carbs), I was able to get each bank pulling the same amount of air at closed throttle. After balancing the throttle bodies, I am able to further refine digitally by trimming fuel to each bank until both banks have the same A/F ratio.

MAP vs Multi-Throttle Tune

I'm now in the process of reconfiguring the tune based on Motec's recent recommended settings for multi-throttle, and that appears to be working even better. It'll probably take a few days to get idle and free revving tuned to the point I can feel comfortable going around the block and tuning under load (basically the same thing I did before).

Sound

The question everyone probably wants to know... what does it sound like? Well, if the plenum setup was one dimensional, this is now two dimensional. It's another layer of sound / complexity. It feels more alive, where the stock sound is buried in plenums and twisting pipes. You get that distinct sound that comes from the trumpets as well. I did some free revving in the cabin, and it's definitely noticeable (even as low as 3000 RPM).

I can't say it sounds "exactly like the carb cars" (I've never driven a carb'd Boxer), but it has a similar multi-dimensional sound that you get with carbs. I will need to really tune the car before I can really make a judgement on the sound, but so far so good!

Throttle Response

Although tuning will really optimize this, I can already tell the throttle response is better. I need to tweak the fuel film settings ("wall wetting").

Also, the throttle pedal feels a bit stiffer than before; which I kind of like. This is largely due to 12 throttle plates / springs instead of the stock 2. The springs are already "soft", and I could even remove some springs if I need to, but I think I will leave it as-is for a bit.

Initial Thoughts / Disclaimer

These are just my first impressions; which I would normally wait to share because I could be wrong about something and have to correct myself. That said, I figure many people are interested in if this will even work, and how it sounds / behaves; which is why I am sharing "early". So my initial thought is "yes, it definitely works!", but that comes with a first impression disclaimer. Also, this is very subjective, but I much prefer the more open and raw BBLM inspired aesthetic. Nothing's hiding under plenums or covers. I will report back as I make progress on the tune. I will make a video as well.

 

So I did some initial tuning, and it's coming along well enough that I felt comfortable making a quick recording. Disclaimer is that it's still pretty early, and I didn't want to go crazy with it and inadvertently trigger knock. But it has been a long time coming to get to this point, and I figure others might be interested.

 

Status update.

So far, so good. No major issues.

I am working on a custom throttle crank, as the stock one doesn't fully open the butterflies. The video above never really gets the butterflies open beyond 40%. I made the first iterations in ASA plastic to test out various geometry. I'm now moving on to PETG-CF plastic, and will eventually have it made in metal. It's a balancing act of pedal feel, how much the butterflies open, and how fast they open. I guess that high school geometry / trig came in handy after all...

Each throttle body has it's own springs. Even when using 12 "soft" springs, in aggregate it's just too stiff when driving. I've since disconnected some of the springs; which has improved pedal feel back to essentially stock.

Both banks are sync'd to the point that I am able to remove all fuel trim via the ECU. I had heard ITBs were hard to tune, and while I can attest that they are harder than plenums, they're not impossible, and I'm glad I didn't let that scare me off. Closed loop fuel and digital trimming makes it a lot easier because you can get it working by using the ECU as a crutch, and then slowly remove that crutch as everything balances out mechanically.

I also received a revised version of my aluminum printed vacuum collectors. These are used to distribute air from the IACV. They arrived as pictured (I haven't cleaned them up at all). I used the same service as the manifolds (CraftCloud).

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With everything above, I am able to gently drive around the block and street tune. The tune isn't far enough along for me to say that total power has increased, but throttle response is improved, as is the sound. I really like the intake sound right behind my head. I am curious if using roof scoops will make it even louder (I wouldn't complain).

As this phase starts to wrap up, I'm putting more thought into the covers. I think I will need to make some prototypes to really know how I feel about scoops vs something more discreet. In the meantime, I ordered two 6 cylinder ITG filters to replace the individual trumpet filters. I'll run those with brackets that attach to the engine lid until I come up with something more permanent.

Same as before, once the dust settles, I'll tally up and share the costs.

 

Ha. Well, if helps at all, even though I haven't formally tallied the numbers yet, I am sure the cost for phase 2 (ITBs) will be less than phase 1 (EFI).

Injectors, coils, ECU, sensors and all that Tefzel wiring is way more expensive than the manifolds, throttle bodies and trumpets.

 

I'm not factoring in R&D. Just the cost to purchase the parts of the end result. In the case of the manifolds, anyone with the models can print them via CraftCloud.

If you factor the cost to print plastic at home, it's another $1,500 (I use a Bambu X-1 Carbon). But then there's the cost of the 3D scanner, etc.. I think your point though, is that a lot of cost went into R&D, as well as labor – which is certainly true. I don't dare tally that cost up!

 

Research and Development. Can be a general term, but in this case, I am referring to the time to do the research, CAD, prototypes, and revisions before the final product.

 

Status update.

More tuning. I've been pushing the car harder, looking for the areas that are too lean / rich. It's at a point where I'm out enjoying the car for a bit, pull over, look at the logs, make some tweaks, then keep driving. Tip in and decel are tough, largely because ITBs are so non-linear, and the difference between the banks are more exaggerated at 0-5% throttle. I'm probably being more of a perfectionist on this than I need to be. The car seems to be perfectly happy with the tune as-is.

Throttle Crank

I recently purchased a replacement throttle crank bushing; which I'll use with my custom crank. I am going to print one more version in PET-CF which incorporates the bushing, then print it in aluminum.

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IACV Fixture

I just can't seem to leave this alone. I'm on my third major revision, but I'm feeling pretty good about it. Attached is the my first version; which used the original AC bracket. I've since designed my own; which mounts in the same spot, and mounts directly to the IACV. The two ports on the back are for the IACV distribution (one for each bank), and then one for the brake booster. After some stress testing, I'll have this made in aluminum. In black, you don't even notice it's there; which is fine by me.

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Airbox / Filters

I've procrastinated on this for quite a bit, but I'm at a point where I need to take it seriously. I've been running the trumpets without filters (CanAm style!). Obviously, this is not a long-term solution (or even a medium term one). I have a few ideas that I am testing. Everything from ITG filters that sit over the trumpets, to more discreet BB-style airboxes that pull air from the rear, to roof scoops. At the moment, I really just need something to keep debris from getting into the cylinder without disrupting the air too much. I have a feeling this is going to take a bit of experimentation. The good news is that won't stop me from enjoying the car in the meantime.

 

Status update.

I've been a bit distracted prepping for new projects (breaking the cardinal sin of starting new projects before the old ones are finished). They're big enough to warrant their own threads, so I won't get too much into it here, but I purchased another PDM to replace the fuse box / relays. This will bring more peace of mind and more flexibility with how I turn on/off accessories while being completely hidden. I also replaced the lead acid battery with lithium (Anti-Gravity); which is considerably lighter. Although weight savings wasn't my main goal, I've been able to remove quite a bit of weight at this point. Side note, my car had a Group 24 battery size, but I went with Group 48; which seems just about perfectly sized. It was total plug-and-play. Also, I've spent a lot of time going back and forth with the Classic Retrofit guys in working out a solution to use their electric AC compressor in my BBi. That's not to say I haven't worked on the ITB stuff...

O2 Sensors
I added two more sensors, for a total of four. Each manifold has their own O2 sensor now. I was previously assuming 3 of the 6 on each bank had the same reading. Turns out this was probably okay, but it made me nervous that I was missing something. I now have full visibility and I'm only ever averaging 3 cylinders at any given time.

Tuning
Still chugging along on this. I think it'd be fine as-is for most people, and it's far better dialed in than it was with CIS. That said, my Motec dealer is suggesting I go back to MAP. The "trick" is to use a damper off the intake manifolds so the MAP signal is clean. He's also recommending a smaller vacuum reservoir. Thankfully, I can save the current TPS/RPM based tune as a separate "package", try the damper/MAP approach, and then A/B them to see which one is better.

Cooling
It's been very hot here (95F), but the car is running hotter than I expect. I think it's just trapped air pockets, but the tricks I know don't seem to be getting it all (purge valve, burp kits, squeezing the hoses, opening the heater valve, etc.). Also, the radiator fans are turning on later than I expect (closer to 97C). I have a block tester that can detect if I am getting exhaust gases in the coolant that I haven't tried yet (maybe a small gasket leak between the head / manifolds?). I'm hoping it's just a stubborn air pocket.

Air Filters / Intake Lids
This is where most of my time has been going. I have been working on various different options. I've probably prototyped half a dozen options at this point. I've tried a "slip on" cover that looked like the ones from the 917, but that didn't incorporate a filter and was just a bit too Porsche. I tried a "stand-off" version that simply elevated the stock lid up enough to let the trumpets breathe, which ended up just looking dumb. I tried skinny scoops like the early LM cars, but they don't look right with the large opening from the stock lids.

My current approach is to create a large "bracket" that attaches at the 4 stock points. This bracket becomes the thing that everything else would mount to and seals up against the trumpets. Using this design, I am working on two potential options, and a third stop-gap one:

1. A lid that looks like the stock one (but taller). Air is pulled from the rear from under the engine lid. Similar to the BB, but a little taller.
2. Roof scoops.
3. (temporary). Mount ITG filters to the bracket so the trumpets are protected while I work on options 1 and 2.

Other than the temporary option, the bracket won't be seen, but it allows me a lot of flexibility in mounting holes while leaving the engine lid alone. I should have the bracket dimensions finished today, then it's off to SendCutSend. I'll post pics once the brackets arrive and I've attached the filters.

Misc.
As this phase starts to wrap up, I have a punch list of small items. Eg, I originally skipped sensors for oil pressure and oil temp as they aren't strictly needed for the engine management, but I'd kind of like to make these work (if possible). I was thinking of hijacking the oil pressure light switch (oil pressure dummy light) to install a proper oil pressure sensor. Not sure what to do about oil temp other than attempt to piggy-back off the stock sensor's signal.

 

Status update.

Mostly tuning. I have the car in a good spot where I can rip around town and not have to constantly look over at the laptop to see if I went too rich / too lean.

I have to say, the car sounds so much better from the driver's seat. The pitch changes with RPM, so if you intentionally shift early and really gas it at low RPM, and just let it build up, you go from this low / guttural growl all the way up to a scream at 6k+. There's enough torque to pull it off without feeling sluggish. Combined with the throttle response, it's made the car a lot more dynamic / fun to drive. This all probably sounds familiar to the carb guys; which is why I can't imagine suggesting a BB owner do this conversion. Although, I think the location of the butterflies, combined with the size and flare of the trumpets exaggerates the auditory aspect compared to the Webers. I previously felt the sound of the car was pretty sterile (even with Nouvalari exhausts), but it's now so much better. I can only imagine what it'll sound like with the chop of proper cams.

Cooling
Turns out this was due to corroded terminals on the radiator coolant sensor preventing the fans from turning on and intermittently cutting out. I'm glad it was something stupid and not something big like a leak between the cylinder and the coolant inlet. The car isn't getting any warmer than you'd expect in 95F weather with a driver ripping up and down the street, occasionally getting stuck in Miami traffic. Helps to have fans.

Side note (not to distract from this thread), the PDM I am installing in the cabin allows me to see current draw for each output. My fans are pulling 8A (left), 10.5A (center), and 8A (right). I'll likely start a dedicated thread for this since there have been a few discussions over the years about how to address the fuse boxes / wiring in these cars.

Filters / Scoops
Still working on this. This is probably going to take a while as I'm experimenting with different things. I've already tried maybe four different options. In the meantime, I'm getting paranoid that a squirrel is going to bomb an acorn into a cylinder while I'm ripping down the street and blow up my hard work, so I installed two ITG sausage filters while I work on the long-term solution. I intend to use this bracket as a foundation for whatever design I come up with as it allows me to drill holes without messing with the stock engine lid.

If you're like me, you find this a mix of both a bit embarrassing, and a little kind of cool. Obviously doesn't solve the rain issue. It's just temporary, and you'll never see the bracket under the end-result. Anyway, you can see just how close the cylinders are to the edges (the filters are centered). Using a BB engine lid would make things simpler, but I don't think that's really practical. Ultimately, with scoops, you won't know the cylinders are asymmetric. In-fact, if I pull air from the rear, the large gap to the inside of the trumpets works in my favor as it allows air to feed down the sides, then up and over (one of the two "finalist" designs I am working on).

Also, this design is giving me a taste of what it's like to not have any rear visibility (which would be non-existent with scoops). And... I guess I don't really care. Sure, it may take a minute to see the red and blue flashing behind me, but I mean... I'd have scoops on a mid-engined, 12 cylinder Ferrari.

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This week is more tuning (especially the high throttle / high RPM stuff). Idle and cruise are just about perfect. This basically consists of finding a spot where I can WOT a few times (poor me) while looking at the screen for A/F ratios going too far in one direction (or worse, knock) – so it's not exactly the safest thing in the world to do. I'm not complaining though.

Now that I have a bracket to hang things off, I will be 3D printing the scoop parts and testing for fitment / aesthetics. This is going to take a while as each scoop will take multiple multi-hour prints. Not sure what material I will do the final parts in yet. I might just go with carbon fiber nylon, painted stain black (potentially reinforced with traditional carbon fiber weave).