[brian_]

Possibly installing something in the trunk to drive the rear wheels and leave the stock ICE in place...

I wouldn't try to talk you out of an EV conversion but I wouldn't recommend the approach you've described. It would be far easier to tackle an ICE replacement rather than the Hybrid you've described.
...
I just don't want you to start without knowing the challenges.

I agree.

With the engine left in place, this is a hybrid - not an EV - and has huge packaging challenges due to the inclusion of two complete powertrains (one gas, one electric). It is also a very ineffective and inefficient type of hybrid (parallel with no charging from the engine except inefficiently through-the-road), which has never been successful in any production vehicle.

 

[brian_]

About driving the rear wheels of a Civic...

B) replace your rear hubs with front hubs and attempt to install some sort of diff between them with driveshafts (that happen to be exactly the right length) then drive the diff with a reasonable size motor. With all of the structure that would be currently between your rear wheels I don't think this is practical.

Obviously the front hubs and rear hubs are unlikely to be interchangeable, and adapting a drive axle into a suspension not intended for it is generally an unreasonable project. That leads to the next option...

C) Remove absolutely every component under the rear of the car (I really mean EVERYTHING). Replace it with the rear end from a rear wheel drive car including the diff. Then again drive the diff with a reasonable size motor.

In some front wheel drive vehicles this is actually reasonable, because there is an all wheel drive version of the same vehicle, and its suspension and drive axle can be used. It is still more reasonable to get rid of the FWD car and buy the AWD car instead - rather than swapping components - but sometimes keeping a specific FWD-only body style would require the swap.

I don't think this generation of Civic (or its predecessor, which was mechanically similar) was ever available in AWD. The rear suspension of a CR-V or Element was similar to the 2003 Civic, and could perhaps work in a Civic. You might even be able to swap an Element or CR-V complete hub carrier into the Civic suspension.

Of course if making the back of the car into a big empty hole and starting again with a completely different structure and suspension is within your design and fabrication abilities, the suspension can be custom or can come from a different vehicle. In his thread Drivetrain layout options for a no-transmission build?, one member proposed putting the entire front suspension from another vehicle in the back of his Civic; the thread fizzled and I assume that the project was never built.


If doing a full EV conversion (and so removing the engine), the easy way out is to just drive the front wheels. The Mitsubishi i-MieEV, Nissan Leaf, VW e-Golf, Fiat 500e, Ford Focus Electric, Chevrolet Spark EV, Smart ForTwo ED, and presumably others are all EV variants of gasoline-engine cars with the motor just placed where the engine was, even if that's not the ideal place... and in all but two cases the result is a front-wheel-drive car with a pile of battery weight in the back, which would be nonsensical to do if designing from scratch. The other two had mid-rear engines, and so have mid-rear motors... still in the wrong place because they get in the way of the battery.

 

[brian_]

I did use front hubs from a FWD on all 4 corners of my latest project and moved the drive unit to the rear. But this is in a custom built chassis designed specifically with this outcome in mind. I didn't try to shoe horn all the suspension and drive unit into the rear of an existing chassis.

Very appropriate for the tube-framed competition special, and I agree quite different from the planned Civic.

Purely from a hub perspective there is a fair chance the front hubs will bolt onto the rear struts.

In some vehicles this may work, particularly where both ends use a bolt-in hub-bearing-carrier unit. Civics in some generations use this sort of hub-bearing-carrier unit in the rear, but the front hub and bearing are usually pressed into the carrier, so they're not interchangeable. Specifically in the EU/ES/EP/EM generation which includes 2003 the front and rear appear to be sort of opposite - the front hub with bearing presses into a hole in the carrier, while the rear hub with bearing slides over a fixed stub axle. There doesn't appear to be any front-to-back swapping opportunity here at the hub level.

The CR-V and Element have the same suspension design as the corresponding Civic but AWD, so they need a different rear hub and bearing configuration - they appear to have a bolt-in bearing carrier, which accommodates driven axles (which is why I mentioned the CR-V/Element earlier). As a result, it may be possible to bolt in the entire hub carrier from a CR-V or Element, and use its axle shafts as well, but there are likely structural issues in mounting a final drive or motor/transaxle unit in the Civic.

The rear of 1983 and later Civics doesn't have McPherson or Chapman struts: there are at least four different rear suspension designs used over these several generations and 35 years, but the design which was used in 2003 (and shared with the CR-V and Element) has a semi-trailing arm lower attached to the hub carrier with two bushings, plus an upper control link. Even in cars with rear struts, the strut configuration (and thus the way it bolts to the hub carrier) is usually different from the front to get the strut lower (and it can be because the rear doesn't need to steer).