Boxer electric air conditioning

Hi all,

As some might know, I've recently converted my '83 BBi from CIS to EFI with ITBs (inspired by the aesthetics of the BBLM's Lucas injection). Obviously, this is not a concourse car. Rather, this is my attempt to create my version of the ultimate BBi (a BB "Modificata" of sorts).

One of the changes made, was the removal of the AC compressor from the top of the engine. Instead, my plan is to install an electronic AC compressor in the frunk. This is popular in the Porsche restomod world (eg, Singer et al). I find the absence of the compressor on the engine to have a cleaner aesthetic, but it also removes weight from the top of the engine. The electronic compressor is lighter, and the weight is moved to the front of the car. Since that's where the rest of the components are, there's no need to run long AC hoses along the length of the car. I suppose there's also a horsepower argument to be made as well (at least when the AC clutch is engaged).

One downside though, is that an electronic compressor takes a lot of current to run. I believe I could run the compressor on the stock alternators, but the compressor's ECU would turn itself off at idle, and only turn on once driving (not ideal).

My plan has two main parts:

1. Install a Classic Retrofit AC Compressor in the frunk.
2. Replace one of the alternators with a modern six phase / Denso style 175A alternator. Classic Retrofit sells the one from WOSP. Similar in design to the ones from DC Power Engineering.

Ideally, I'll keep all the other AC components the same (condenser, drier, etc.). Not sure if this doable, but we'll see. There are other misc. items to address as well, like upgrading the alternator wiring. I'll use larger motorsport battery cables for the "Big 3" (battery-to-frame GND, engine-to-frame GND, alternator-to-battery).

The compressor has already been purchased, but they're made to order and it'll take a few weeks to arrive. There are still some unanswered questions that I'll figure out as I go (fittings, brackets, misc wiring, etc.). I'll share my progress on this thread.

Living in Miami, it'll be nice to have proper AC.

 

Never like it when a parts supplier makes a false statement: "and no loss of engine power". Using the engine to drive the alternator to run the compressor probably actually uses a little more (or, best case, about the same) engine power than just using the engine to drive the compressor directly. If you go this route, you will also probably have to design/make a new belt system to drive the now much higher power 175A alternator. But sending you positive mojo, and hope you'll post details if you go this way.

 

My first reaction too. No way the existing belt system drives a 175 amp alternator.

 

Yeah, it's needless marketing fluff. I am largely considering it a wash or inconsequential one way or the other.

I could be wrong, but it is my understanding that this style of alternator is considerably more efficient (not just more windings) – especially at idle. The hope is that it's a drop-in replacement as far as belts and bolts go. I guess we'll see...

I'll post the good and the bad.

 

I'll do some research and report back. Not sure if a different pulley is required, necessitating a shorter belt, serpentine, etc.. Or maybe something more extreme. Or maybe it really is just drop-in as far as bolts and belts go.

 

And....you are wrong . Electric machines (motors, alternators, generators, etc.) have had pretty decent efficiencies since the 1890s. Here's a typical reference for you saying that a cheapy alternator might be 60% efficient while a super-duper alternator could be 80% efficient):

https://themachine.science/efficient-alternator

Your stock belt system, intended to drive an alternator supplying 770W (14V x 55A), would have to be way, way, way over-designed to live with an alternator supplying 2,450W (14V x 175A) -- and, if anything, F has more of a history of under-designing their belt drive systems. Still, a super-interesting project (that I can't recall ever being discussed/shown here before) so will follow with interest.

 

Its not a drop in. The belt drive system in use by Ferrari at the time had great difficulty driving 45 and 55 amp alternators. Ferrari redesigned it for the Testarossa with a 125 amp alternator and it was grossly underdesigned and required a redesign. The reason the compressor was located where it was was because of its driving power requirement it needed to be as close to the crank pulley as possible. Neither of the alternator locations had that benefit. TR alternators were all right next to the compressor for the same reason.

 

IIRC, the BBLM alternator is in that position as well? Not sure if that was for the same reason.

I guess we'll see what's needed. Both manufacturers above state you should be able to use the same sized belt in the same location. Classic Retrofit even has this alternator listed for the 308 for use with their AC. I'll ask them for more information on the install / pulley setups they've seen.

I guess more importantly, think my point isn't "who's right", but rather it probably doesn't matter as it doesn't seem like any of these issues would be deal breakers. I'll tackle issues as they arise. Can't be more difficult than the EFI/ITB conversion!

Thanks. I'll post here as the project progresses. Both good and bad. If a new pulley setup is required, I'll give you guys both credit for calling it

 

Drive it with a cog belt.

 

Very cool! (No pun intended)

Classic Retrofit AC Compressor says something about "a healthy current". Is there a number associated with that description?

Looks like a nice mod.

 

It's my understanding that the compressor requires a constant 70A. Otherwise, the compressor's ECU will shut off. It's also my understanding that the 175A alternator puts out about 75A at idle (96A at 1800 RPM). So if I keep one stock alternator, and upgrade the other to 175A, I'd have 230A total, with maybe 90A at idle?

I won't really know how all these systems work together until I get in there and start swapping stuff out. I'm pretty sure this hasn't been done on a Boxer before, but it's been done quite a few times in the 911 community, so there are a few examples I can look at.

 

Status update.

Compressor Arrived
Earlier than expected! It came very well packaged / protected. I attached some pics so you can see the size comparison between the Classic Retrofit and stock. I haven't had a chance to weigh them yet, but it's considerably lighter (which should come as no surprise).

Image Unavailable, Please Login Image Unavailable, Please Login

Misc. Prep
I had previously disconnected the high/low hoses from the stock compressor during the ITB swap, but they were just kind of dangling there (hidden). I've pulled out the low side hose, and now need to get the high side hose (little more tricky).

Also, my car has a battery cutoff on the bulkhead cover. I don't see it listed in the parts diagrams, but it has yellow chromate (maybe dealer installed "upgrade"?). Either way, it looks a bit beat up / over-heated. So I'll replace those cables with thicker motorsport grade – along with the other key alternator / battery cables.

Image Unavailable, Please Login
Image Unavailable, Please Login

Alternator
I have an order placed for the 175A alternator (no ETA yet). I'll likely purchase the wiring / terminals / heat shrink / connectors from Prowire; which has been my go-to during the EFI and PDM projects.

Game Plan
Now that the compressor is here, I can start laying things out, creating brackets (SendCutSend), ordering wiring / connectors, etc.. Like my previous projects, I will do my best to ensure everything is bolt-on/bolt-off (nothing "destructive"), but that might be tricky with all the riveted covers in the frunk area. Might be better overall to rethink the frunk layout since I never carry a spare wheel anyway and the entire layout essentially revolves around that.

 

Good day Robert,

Outside of the obvious wiring changes, what are your plans for changing/upgrading the factory main supply wiring/cabling ? I ask, as Ferrari's wiring just barely met the electrical loads demanded of it and so adding a lot more load will simply make matters worse. In fact, depending upon the sustained current being drawn, you may have to consider different wire characteristics (stranding, alloy changes, etc) along with superior insulator sheathing (silicone?) to maintain the rated temperature rise of the wire, but also to minimize heat transfer to wires that run adjacent, bundled with these cables, or through confined areas with little air flow.

Cheers,

Sam

 

Hi Sam,

I wouldn't say that the plan is very concrete at the moment, but other than the obvious up-rating changes needed, I'll likely up-rate anything that might be pulling additional current. For the PDM project, I used this 4 AWG with Raychem SCL on the lugs. That worked well, so I'll likely use more of that (maybe going up to 2 AWG in some areas). For the rest of the wiring, I only use milspec Tefzel /32 (in various gauges). Any Tefzel outside of the cabin, I wrap in Raychem DR-25 with SCL on the ends which helps with heat and abrasion. In the cabin, I've been leaving the wires open, but with SCL on the ends.

I like working with the Deutsch DT/DTM/DTP family of connectors for new circuits (eg, the EFI work), but for period correctness without modifying functioning circuits, I've been using the TE Faston family of connectors (eg, the 180906 connector for the Dinoplex connector, and the 280232 connector for the fuse box terminals).

All that said, the AC is largely outside the main circuit. The AC ECU will power off the original 16A AC fuse (although it only needs 5A). That's really the only thing on the other side of the shunt. The AC compressor itself will be connected to the battery through the AC ECU; protected by an 80A fuse and an isolating contactor relay (not going through the main circuit / shunt).

I don't think it matters, but I recently replaced my battery with a lithium AntiGravity (Group 48). Complete drop-in (has BMS built in).

I think the big questions are more around alternator pulley geometry (seems the bets are against the current geometry / pulley being sufficient), as well as if I can (or should) retain the factory fiberglass covers in the front vs taking them out for something more custom. I like the more exposed / easy access look I now have in the engine bay, so I may try to carry that through to the front where I can more easily access brake lines, AC components, etc. – which somewhat dovetails into the new radiator / cooling fans project.

I know electronics are your area of expertise, so feel free to fire away with suggestions / critiques – I won't be offended!

 

Good day Robert,

Sounds good. As long as you have been reviewing and planning on superior wire, then all is fine. Since you did not post too much about the wires/wiring, I was concerned that it was not getting the attention that it needed. Obviously you have this covered and so all should be fine.

As for the 4 AWG wire, I find it interesting that the link you provided did not include a resistance spec. The Tefzel wire looks great and the specs provided are what one would expect (which includes resistance, etc).

The Faston connectors have been around for ages, but are not overly tolerant of high temps found win high current applications... and so the housings can discolor and distort. That said, Faston connectors were designed at a time where auto current loads were relatively modest and so one cannot fault the design.

As for the replacement battery, I would check/confirm what protections are built into the battery itself. Lithium battery technology is great, but it does need a fair mount of design attention (circuitry) to address various charging and discharging conditions. Overcharging or rapid discharging (e.g. very high current being drawn or short) can cause Lithium batteries to self ignite and once they start burning, they pretty much continue until there is nothing left (extinguishing a lithium battery fire is not trivial). I would think Lithium Auto battery manufacturers would take all this into account, but some may not... so it would be best to double check... and especially because of the potential high currents being drawn by the Electric AC. Additionally, it would also be prudent to confirm that the lithium battery is tolerant/compatible with the vehicle's charging system and your potential replacement of one of the Alternators.

Cheers,

Sam

 

It looks like the cables used very nice power lugs over starter lugs, but the crimp job was totally botched. Those lugs require the use of very expensive crimpers to get it right. Making Your Own Battery Cables - Marine How To

 

I assume that you will convert the cooling system to a legal cooling fluid like in example r134a. If that’s the plan I would recommend changing out all fluid hoses to modern type sleeved hoses to avoid the fluid escaping through the old hoses. I did that in my bbi four years ago when converting to r134a and haven’t had to refill the system ever since.

Best, Peter

 

I figured I'd at least attempt to reuse as many of the larger components as I can (eg, drier, condenser, blower, evaporator, etc.), and then replace / upgrade as needed. Hoses will be replaced though, and I'll likely use modern "pad" fittings as well. Refrigerant will be updated as well.

As you know, I'm removing the fiberglass panels in the front area (almost finished, thanks for the pictures!). The next step will be to 3D scan the area, and mockup the condenser placement along with any new brackets / panels.

 

I was feeling guilty now and then for modifying my 308 GTB but not anymore after seeing your threads

 

Ha. Well, I feel guilty every time I do something non-original; while I'm doing the work and it's a big mess. So far, the guilt has gone away when I finish the project though. I find it best for my sanity to ignore the value of the car.

 

Status update.

I initially thought about fitting the AC compressor within the stock frunk panels, but ultimately decided against it. I think I can improve on the quality (the cloth is just kind of randomly placed, faded, and peeling anyway), as well as the layout. I don't carry a spare tire, so I can rethink the storage area, AC / battery compartment, and radiator ventilation. I'm pretty sure there are areas here that haven't seen daylight since Maranello 1983, so there's quite a bit of cleanup needed. I'll also take the opportunity to remove the ghetto rigged valance light wiring added for federalization.

Attached is a pic after initial removal of the panels. I plopped the compressor in just for reference. I'm not married to that spot, but I think it's the most obvious. With the AC ECU, it's about the same height as the battery, so a center access panel beneath storage seems logical.

I also 3D scanned the area to start working on new panels in CAD. There's a pretty obvious "V" shape, so I'll probably base the design around that.

Anyone have experience with the Re-Originals heater ducting? Mine don't seem that bad, but I figured it'd be nice to refresh some of the tired areas.

Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

 

No wonder a BBI has 2 alternators, with all those fans!

 

Inefficient fans at that. Especially that middle one (AC); pulling 11A with essentially no shroud.

 

+1. When you see the 3 fans and two blowers like that.. Yes, lots of motors! Not far away, there's a cabin blower motor, wiper motor, two fuel pumps, and two window motors. I guess it really can add up. Guessing averaging about ~8 amps each ?

 

One of my recent projects was to replace the fuse box and relays with a PDM; which can measure current draw on each output. I mostly replicated the existing fuse box configuration (each PDM output is mapped to one fuse). The higher draw outputs are:

RH fuel pump: 7.5A
LH fuel pump: 7.5A
RH radiator fan: 8A
Center radiator fan (AC): 10.5A
LH radiator fan: 8A
Main beams: 8A (each)
Flash-to-pass: peaks at 13A, then settles on 9A
Dipped beams: 6A each (7A with fog lights on)
Heater fan motors (both on high): 7.5A
Window motor: 10A (20A if you continue pressing the button once fully up or down)
Hazard lights: 13A
Horns: 18A

I made some tweaks to the configuration based on what I found. For instance, I separated the radiator fans from the other circuits. With the factory configuration, if the fans are on, and you honk the horn for anything more than a quick beep beep, you're likely to blow that 16A fuse since the combined current draw is 26A.