ICE-Based BEVs: Let’s Talk Scar Tissue

Decisions, decisions. Some automakers are modifying their ICE platforms to create BEVs, while others are going with a clean-sheet design for a dedicated BEV platform. I personally believe everyone will have to go with a clean-sheet design, but there are pros and cons to both approaches.

The reason why automakers want to use existing ICE platforms to make a BEV is that they can save a ton of time and money. They can reuse much of what they’ve already got, both in components and manufacturing facilities. It also gives them a bit of a hedge. Even though sales of electric cars are soaring, their market share is still fairly small, about 4% of the market in the U.S., though more than double that in Europe and China.

And there’s a lot of skepticism, at least among some car companies like BMW and Toyota, as to how much or how fast the market will really go electric. So, by taking an ICE platform and modifying it to make electric cars, they can reduce their risk and their investment until sales of BEVs really ramp up later this decade.

That sounds like a really smart strategy…until you start diving into the details.

The disadvantage of using an ICE platform is that it carries a lot of what the engineers call scar tissue. In other words, a platform that has to be able to use a piston powertrain or an electric one ends up with a lot of compromises. It has to be designed to accommodate a gas tank in the rear or a battery pack in the floor. It has to have room for a radiator up front or, hopefully, make room for a frunk. It has to have a location for an 8-speed automatic transmission or a smaller spot for a 2-speed gear reduction unit. And so on and so forth.

Designing a platform be able to accommodate two different kinds of propulsion systems means you end up with a heavier vehicle. And that extra weight is what the engineers call scar tissue.

I think a great example of the pros and cons is a comparison of Tesla’s Model 3 versus the BMW i4 electric. The Model 3, as you know, is built on a clean-sheet, dedicated BEV platform. The i4 is built on a modified version of the ICE platform for the BMW 4-Series. But the i4 and Model 3 are very close in size.

And for this size comparison I’m using what they call a car’s footprint. That’s where you take the wheelbase, which is the distance between the front and rear wheels, and multiply that by the vehicle’s track, which is the distance between the left-side and right-side wheels. And since the front track is usually a little different from the rear track, you just figure out the average between the two.

So, the i4 has a wheelbase of 112.4 ins. (2,855 mm), the Model 3 is 113.2 ins. (2,875 mm). The i4 has a track that’s an average of 62.9 ins. (1,598 mm). The Model 3 is 62.2 ins. (1,580 mm). Like I said, very close. Multiply those numbers for each car, and the i4 has a footprint of 7,069 sq.-ins. (4.56 million sq.-mm), while the Tesla is 7,041 sq.-ins. (4.54 million sq.-mm) – again, very close, almost the same size.

But this is where the comparison really gets interesting. The i4 has a curb weight of 4,680 lbs. (2,123 kg), while the Tesla weighs 3,648 lbs. (1,655 kg). Yikes! That means the Tesla is over 1,000 lbs. (454 kg) lighter. What’s even more amazing is that the Model 3 is actually slightly lighter than the ICE version of the 4-Series. I’m using the BMW 430i Grand Coupe with an automatic transmission and a base Model 3 to make this comparison.

So, the next time you hear someone complain about how much heavier an EV is because of all that battery weight, you might want to point out to them that a Model 3 with its battery pack is actually lighter than a 4-Series BMW with a 2.0L turbo.

One reason why the i4 is so much heavier is that it has a significantly bigger battery, 83.9 kWh, versus only 50 kWh in the base, rear-drive Model 3. I’d estimate the BMW’s bigger battery pack is somewhere around 370 lbs. (168 kg) heavier than Tesla’s. And I’d also estimate that extra battery capacity adds over $4,000 cost to the i4. Yet, for all that extra battery, the i4 only delivers 29 more miles (47 km) of range.

All this difference in weight and battery size is reflected in the price of each car. A base Model 3 costs about $47,000. A base i4 is over $55,000. The only way BMW can get the kind of profit margins it needs with its ICE-based i4 is by charging $8,000 more.

And that really shows you the drawback of going with an ICE-based platform that carries a lot of scar tissue. BMW ended up with a significantly heavier, much more expensive design that doesn’t deliver much more range. We’ll see how it sells, but these numbers tell you BMW doesn’t stand a chance of taking on Tesla.

Rivian R1T_0

But this comparison between BMW and Tesla doesn’t tell the full story of ICE-based BEVs compared to clean-sheet BEVs. Not all EV startups are as weight-efficient as Tesla. So, let’s compare the Rivian R1T pickup (pictured, above), which is a clean-sheet design, to Ford’s F-150 Lightning, which is built on a modified ICE platform. And for comparison purposes, let’s go with the big battery in the Lightning – 131 kWh, which is almost the same size as the one in the Rivian at 135 kWh.

The footprint of the Lightning is 9,923 sq.-ins. (6.4 million sq.-mm), while the Rivian is 9,139 sq.-ins. (5.9 million sq.-mm). So, the Lightning is 8% bigger, but…it’s lighter. It weighs 6,590 lbs. (2,989 kg) while the Rivian weighs 7,148 lbs. (3,242 kg). That’s a 558-lb. (253-kg) difference.

The Rivian has four electric motors; the Ford has two. That probably accounts for a lot of the weight difference. And the Rivian can tow more: 11,000 lbs. (4,990 kg) versus 10,000 lbs. (4,536 kg) for the Lightning with Max Trailer Tow Package. But they both have about the same driving range, about 320 miles (515 km). So that shows Ford was able to come up with a competitive weight package with an ICE platform compared to Rivian’s clean-sheet design.

McElroy SQUARE_6

We’re still in the early days of the transition to an electric future, so that’s why we’re seeing some automakers modify their ICE platforms to make electric vehicles – to save time and money. But you watch. That’s a short-term solution. In the long run, a clean-sheet BEV platform, done right, will always be a superior product to an ICE-based BEV. And it all has to do with getting rid of that scar tissue.

John McElroy (pictured above, left) is editorial director of Blue Sky Productions and producer of “Autoline Detroit” for WTVS-Channel 56, Detroit.