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Tearing Down Tesla Segment 8: Comparing the Cooling Strategy / Housings of Motors for Tesla Model 3 vs BMW i3

Both the Tesla Model 3 and BMW i3 have novel approaches to cooling the motor. This week’s segment compares these approaches. Let’s get to it.


The BMW i3 uses a two-piece motor housing to allow for large coolant channels in the housing walls to cool the housing, which in turn cools the motor and stator laminate stack. The Tesla Model 3 has a coolant to oil heat exchanger on the exterior of the housing and uses the oil to flow through grooves and channels in the stator laminate stack to cool the motor.

The advantage of the BMW i3 design is that it eliminates the need for a heat exchanger, along with the thermal transfer loss between the two fluids. However, the two-part housing requires more processing costs related to casting and machining a second housing component.

The advantage of the Tesla Model 3 design is that it only requires one housing and allows for direct cooling of the stator through contact with the cooling fluid (versus through a housing wall). However, this design requires a heat exchanger assembly and an oil pump to circulate the fluid. These two commodities add significant cost to the motor assembly, but they also have a dual purpose of providing heat to the battery as well as cooling the motor. In this design, the systems pays for some additional functionality.


The general conclusion is that Tesla is increasing their cooling performance of the motor by running oil directly through the laminates, but accommodating this system requires a cost increase for added commodities of a heat exchanger and pump. This drives approximately a $31 cost increase on the Tesla Model 3 versus the BMW i3 design, even though the Tesla was able to use a single piece housing.


Each of the motor housings and companion cooling components were analyzed in Design Profit to understand the full cost of cooling the motor. Specifically, the housing full fabrication process was captured in the software, including the casting and all machining operations.

Should Tesla Import the Model 3 from China?

According to Munro & Associates CEO Sandy Munro, the answer is YES.

This InsideEVs article asks some thoughtful questions about the possibility of Tesla importing the Model 3 to the United States from China.

Would U.S. customers care?

Especially since the build quality is better?

When speaking to Alex Guberman of the YouTube channel E For Electric, Munro said he thinks Tesla should consider importing the vehicle to the United States and other countries from China because Tesla would make more money if they did so.

According to the article, “Munro and Guberman discuss how all cars have a high amount of Chinese-made parts in them, particularly the electronic components. Chinese manufacturing taxes also play a big role in this discussion. China reduces the manufacturing taxes they impose if the vehicle gets exported out of China, lowering the cost per vehicle. Therefore, Chinese-built cars can actually cost less when they’re exported, even after paying to ship them to their eventual destination.”

Be sure to check out the full article for his full insight.

Tearing Down Tesla Segment 7: HVAC Differences in the Tesla Model 3 & BMW i3

There’s a rather traditional design tradeoff for the IP HVAC ducts in the Tesla Model 3 and the BMW i3. Read on to learn more!


The BMW i3 uses blow-molded ducting, which can reduce material weight and cost by allowing for thinner walls on the duct, but often requires multiple pieces to create the path to route the air. The Tesla Model 3 uses a three-wall injection molded duct, which reduces material weight and cost by eliminating one side of the duct and using the instrument panel substrate for that wall. This design often integrates several pieces into one part and requires more design work and a rather large specialty assembly jig to weld the part to the instrument panel.

Second, the BMW i3 has rather traditional air vents. There are four vent assemblies (two on each side of the driver and passenger) and each vent consists of several small parts assembled to allow for manual control of the air side-to-side and up and down. The Tesla also attempts to reduce cost using a very novel approach to controlling airflow at the vents. Tesla uses a patented air vent design that uses two opposed air streams to control airflow allowing for the need of only two vent assemblies with fewer vent components, as less directional fins are required to focus the air. To further improve the design, they motorized the control (via a touchscreen) to add an additional level of functionality. With this design, they were able to reduce that cost of the components by making it fewer parts, but then put that cost back into the system by adding functionality.

It is interesting to note that Tesla is possibly able to adapt this specialty design with a more complex assembly jig because its vehicle production volume is significantly higher than the BMW i3, which allows those engineering and tooling costs to be distributed across more parts, allowing for bigger development budgets.

Sandy Munro Comments on Tesla’s Secret Sauce

In a guest post for Clean Technica, author Ian Richards lists some reasons critics harshly judge Tesla CEO Elon Musk, including his “run-ins with the SEC, intemperate tweets, and a catalogue of missed deadlines show that he does not have the character or the competence to run a major public company.”

However, according to Richards, there is a problem with these judgments. While “all the major automakers are experiencing declining sales and laying off workers. Tesla just recorded a blowout quarter, and is growing unit sales faster than any automaker in history.”

The article discusses some of the reasons for Tesla’s success. Many are the result of Musk’s innovative thinking and leadership that inspires groundbreaking products and technologies, including one example where he quotes Munro & Associates CEO Sandy Munro:

“The Superbottle is a great example of how the normal automotive companies don’t work together, and Tesla does. That Superbottle crosses many lines that you can’t cross here (in Detroit). If I’m in charge of engine cooling or battery cooling, I don’t want anything to do with cooling the cabin. And yet, we’ve got the motor cooling, the battery cooling, and electronics, all going through one little bottle that’s got some clever little ball valves that open and close to make sure that everything’s getting heated or everything’s being cooled to where it needs to be. We all thought that was the best thing in the whole damn car.”

For more insight on why Richards calls Musk “the smartest CEO in the auto industry,” check out the full version here:

Tearing Down Tesla Segment 6: The cost of a parking pawl

Did you know that the Tesla Model 3 does not have a parking pawl and actuator in its gearbox?


The Tesla Model 3 is unique, as it doesn’t have a parking pawl and actuator in its gearbox like most other electric vehicles, such as the BMW i3. This is potentially made possible by relying more on the EPB (electric park brake) units on the rear calipers in the brake system.

For reference, the BMW i3 also has EPB units on its rear calipers, along with the traditional park brake pawl in the gearbox.                                                                                                      

Data: The BMW i3 spends approximately $25 on parking pawl components and assembly, more than half of which is associated to the actuator for the parking pawl. These are costs that the Tesla design avoids incurring.

Methodology: Using Design Profit’s comparison tools, Munro was able to identify cost and component differences between the two designs.

Munro & Associates to Host Aluminum Design & Lightweighting Solutions Workshop

On March 18 – 19, Munro & Associates will host the Aluminum Association’s Transportation Group’s spring 2020 Aluminum Design & Lightweighting Solutions Workshop. The event will teach automotive engineers developments, advancements and best practices in aluminum technology by experts from leading producer companies, including Constellium, Rio Tinto, Arconic, Hydro and Novelis.

The two-day event will take place Wednesday, March 18 from 8 a.m. to 6 p.m. and Thursday, March 19 at 8 a.m. to 4 p.m. at Munro & Associates, located at Centre Rd in Auburn Hills, Michigan.

For more information, including the complete agenda, or to register for the event, visit:

Tearing Down Tesla Segment 5: Seat Comparison on Tesla Model 3, BMW i3 and Chevy Bolt

Seats are another example of how OEMs spend money in different areas. For example:

  • The Tesla Model 3 only uses vinyl for its front seat covers; while
  • The BMW i3 uses high-end leather and cloth; whereas
  • The Chevy Bolt uses leather and vinyl.

Background: This shows that BMW and Chevy prioritize the quality and feel of the seat surface, while Tesla focuses more on adding functionality with a 12-way seat control (versus the manual adjustments on the i3 and Bolt.)

Typically, an electric vehicle is competing alongside luxury vehicles, which normally expect powered seats, but often many electric vehicles will revert to a manual seat in order to reduce the weight associated to the heavy motors that provide actuation.

Data: The front seats for: Model 3 are $568 and 44.8kg; versus the BMW i3 at $729 and 39.8kg; versus the Bolt at $532 and 38.3kg.

Methodology: During the teardown process of each vehicle, we fully disassembled the seat to analyze the covers, structure and electromechanical mechanisms. Each manufacturing process to sew, weld or stamp the components for the various areas of the seats were quantified to develop a full cost for the seat.

New Event: SAE Tour of Munro & Associates with SAE

Join us on March 25 for a tour of Munro & Associates’ competitive product benchmarking and teardown facility. At Munro, products are analyzed for total accounted cost reduction and quality improvements. The tour of the Munro Benchmarking Investigation, Innovation & Implementation Center will provide an in-depth review of advanced electric vehicle technologies related to electric motors, inverter converters and batteries.

Attendees* will obtain hands-on access to some of the most innovative vehicle components on the road today, such as the Telsa Model 3, Audi e-tron and all-new Nissan Leaf.

Munro has a long history in the automotive industry, working on pivotal new launches and redesigns for most of the world’s OEMs, as well as a vast global array of Tier 1 and 2 suppliers. As such, innovation and paradigm shift has been a consistent output for several decades.

8:00 – 8:30 a.m. Networking Breakfast
8:30 – 10:30 a.m. Presentation and Tour

*Important Note: Tour is limited to SAE members and their guests. Registration will close March 23. No onsite registration or refunds after March 18. Continental breakfast will be provided.

Click here to register:

Tearing Down Tesla Segment 4: Battery Cooling System Comparison on Tesla Model 3 vs. BMW i3

The Munro engineering team also spent some time analyzing the battery cooling systems for Tesla (coolant) and the BMW i3 (AC fluid).

Background: Outside of the battery pack, the primary cost difference seen between the Tesla Model 3 and BMW i3 is the cooling system. The Model 3 (similar to other coolant cooled battery packs, such as the Bolt) requires an auxiliary water pump to push coolant through the battery cooling circuit. Since the BMW i3, which uses AC fluid, has to move much less fluid, the compressor does not require an additional pumping mechanism, but may require a slight upsizing of the AC compressor to compensate for increased demand.

Further, an added benefit that the Tesla battery pack cooling gives to its functionality is that each battery cell in the pack has full contact along the side of the coolant tube. This differs from the BMW (and the Bolt), which have only module level contact to the coolant system (at the bottom of the battery module). This enables the Model 3’s cells to cool more evenly, as well as more efficient control of pack temperatures.

Data: Within the battery pack, the Tesla cooling system costs approx. $270 for a 75 kWh pack, which translates to $3.60/kWh in cooling cost vs. the BMW, which costs approximately $84 for a 22 kWh pack translating to $3.80/kWh. 

Methodology: All coolant system components were removed from the vehicles. Install to vehicle and battery pack were captured in Design Profit to develop assembly costs. Next, the fabrication of each part within the cooling racks in each battery pack was analyzed to develop cost for the parts. These costs are then totaled and analyzed via Design Profit to better understand the differences between the vehicles.

EV vs. ICE Cost Breakdown and its Effects on EV Adoption

InsideEVs recently posted an article sharing Munro & Associates CEO Sandy Munro’s cost breakdown comparison of electric vehicles (EV) vs. internal combustion engine (ICE) vehicles, originally shared during Sandy’s recent Autoline After Hours interview, and why the results give an explanation to EV adoption issues.

Author Gustavo Henrique Ruffo states, “We are not sure how charging companies will make fast charging cheaper than filing up a fuel tank, but Sandy Munro helped us see more clearly why depreciation is a big burden for EVs. The engineer did so by revealing how much of their cost is concentrated on the electric powertrain.”

Sandy’s cost breakdown shows 51% of the cost of an EV is in its powertrain, compared to only 18% for an ICE vehicle. To which Ruffo states, “Munro clarifies that battery packs, inverters, and controllers are as much part of the EV powertrain as are the motors and any transmission an EV decides to use, such as the Porsche Taycan’s. Anyway, if he broke down the powertrain components’ share in the total cost, the battery pack would undoubtedly be responsible for most of it.”

The article goes on to discuss battery packs, the cost and what changes need to be made to in order to improve EV adoption.

Check out the full article here: