Hello all!
I’m not 100% sure if this is the best place to seek advice but I recently got into cars and wanted to modify my own car for efficiency. I searched online for all kinds of hybrid conversions but most were just plug in hybrids instead of being fhev. I saw a few people put a motor between the transmission and the drivetrain but I also saw a few people go for a tesla rear swap altogether. The problem is these people usually converted classic cars into full electric vehicles instead of the hybrid I was looking for. I still want the full functionality of my car (ei: automatic transmission, infotainment systems, and awd) almost like it never had an electric engine installed and modify it as so (ei: engine swaps, tune ups, etc). I’m going for modularity, fuel efficiency, and practicality/ user friendliness (anyone can get in and drive it like a normal vehicle). In my research I found the rear unit of a model s and wondered if I could somehow attach it to my rear drivetrain and have it operate like a hybrid where the engine charges the batteries through braking, coasting, and normal functions and the combustion engine would kick in around 40 mph. Would this cause any problems with the transmission or gears of the drivetrain since my car is all wheel drive? What problems can I run into? Thanks everyone for your input (I’m new to the cars world so I dont know much other than the few donut media videos I watched discussing how certain parts work)
Welcome to the forum.
I can’t help you, I do not have the knowledge.
Your goal might be possible, will require extensive engineering and a substantial bank account.
Good Luck
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Do you have a degree in electrical engineering? AND a degree in controls engineering? And at least 10 years experience working on hybrid vehicles? Are you a skilled metal fabricator? In order to do this job, you’ll need all these at the very least.
Just a few points… to recharge the batteries requires a BIG generator. FAR bigger than any conventional alternator… hybrids use the drive motor as a generator while braking. This is called re-gen braking. The first problem is to provide consistent brake pedal pressure under re-gen and when not under re-gen. This is not trivial. Next, a FWD car doesn’t brake much from the rear so using the Tesla motor in the rear can’t generate much re-gen or the car will lock the rear wheels and you’ll need the signals from the ABS to control wheel lockup in slippery conditions.
Now to the drive modes. If you want the IC engine to “kick-in” at 40 mph, you’ll need to develop a way to hold the engine in neutral and then drop it into the correct gear at the correct RPM at 40 mph so that a large jerk doesn’t happen. Control software and hardware drivers need to be developed to make this blend nearly seamless.
The two issues above are why the PHEV Prius is a FWD vehicle with the electric motor integrated with the front driveline, not just hung off the rear.
If you do, somehow, get this thing to drive and stop, you will need to develop the Tesla suspension to complement the front suspension it is attached to. Ride and handling will need to be developed so when you apply the kilowatts to the rear motor the car doesn’t spin out of control.
Are you starting to understand why it takes teams of engineers with advanced degrees years to develop these complicated systems? Do you have the knowledge and skills to pull this off?
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Hey, thanks for commenting. Firstly I have 3 years of electrical engineering experience so I’m not too worried about the electrical portion of the job but I dont tend to do this potential job on my own. It’s not a set in stone plan but if I had to choose I would send the parts and car out to a qualified repair shop to get the integration, but I do see your point. As for the drivetrain since my car is awd couldnt I just integrate a brake system that is the same as the front tires? That way if the front tires brake the back ones do too (my reasoning here might be flawed but go easy on me here) Again this is all theoretical talk and I’m open to your suggestions for a work around or solution. And if this avenue is simply too much are there any “easier to intigrate” solutions out there for the same outcome of being a hybrid car hybrid? One integration I found was the one I mentioned in the original post where someone just attached an electric motor at the end of their transmission and the electric motor to battery and controller.
Here are two videos I found that explain what I mean:
The first is a professional integration while the second is a hobbyist trying their hand at something new.
Unless you’re planning on doing a lot of road trips to the middle of nowhere where there aren’t any EV chargers available, I’d suggest you tweak your idea a bit. If you’re swapping in a Tesla drivetrain, you do not need a gas engine.
Cars like the Prius need the gas engine in part because their electric motors are horribly weak. 0-60 would be measured in tens of seconds if the motor could get the car to 60 before the gas engine takes over.
But the Tesla drivetrain changes all of that. It’s very powerful, and there’s really nothing a gas engine would add to that equation unless you also swapped the gas engine for, say, one from a Bugatti Veyron or something.
In fact it’s so powerful that you can just take your transmission out too. You get the effect of an automatic because you only have the one “gear.”
There are companies that do this already. Usually they convert classic cars over, like 60’s Mustangs or Deloreans, but if you gave them money they’d do it to any car. But the trouble is that all of this stuff is incredibly expensive. We’re talking “enough to just go out and buy a new Tesla Model S” expensive. Just for fun I priced out what your car would cost to convert at one of these places. You’d be looking at around $120,000 unless you wanted the really powerful Tesla motor and the highest-range battery option, in which case add $27,000 to that.
A lot of that cost is in the design work and labor, of course, but the Tesla motor assembly alone can cost thousands used, and more than 10 grand if you want the high performance version. And that’s without batteries.
If this is just a mental exercise, cool, but if you’re actually thinking of doing this, be prepared to spend a lot of money.
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WOW, thanks a lot for that. Really puts things into perspective, so I do actually have legitimate plans to upgrade the motor to one of a mustang gt since I heard it’s easy to integrate and someone has already done it. I know there are probably much more powerful motors out there but I would like to stick to ford motors as it’s just more convenient. Also with what you said I’m thinking of just scrapping the whole idea of the tesla power and just using a custom electric motor like the people in the videos did.
Or what this guy did: Worlds First 600HP ALL MOTOR 350Z HYBRID Conversion (+200HP Electric Motor) - YouTube
The whole point is to get a better fuel economy than my existing setup which avg around 21 to 25 mpg. I know adding a bigger motor is counterintuitive but I believe there is a middle ground somewhere between performance and fuel efficiency using an electric motor, the tricky part if finding what combination works best I would think.
You want to spend thousands to get better fuel mileage ? On a discontinued vehicle ? Me thinks this is not a practical idea . Now if you want to see if you can do it that is different .
I can’t imagine a shop would accept a group of parts and ‘here, put them together’ instructions. If you’re wanting the gas engine to charge a Tesla-sized set of batteries, that isn’t going to happen. Hybrid cars have tiny battery packs in comparison to EVs. Now you’re wanting to put a Mustang engine (V8, I assume) in a Fusion?? Along with a Tesla motor and battery pack? And integrate their operation? Hmmmmmmmmm
I really like the interior of my vehicle and cant really find a replacement at the same price range. Yea I could go the sporty route and get a mustang with the engine I want but the enterior is subpar and the fuel efficiency isnt that great understandably, existing hybrids arnt really fun to drive around but they do offer great fuel economy and their interior is up their but the cost of a fhev that suits me just isnt in my price range from what I’ve seen. Also a tesla has great mileage and great interior but doesn’t give me the “punch” and fun driving I get from a sports car and I would assume to try and and turn either of the vehicles above into one another or a combination of all 3 will cost me upwards of 100,000 easily whereas I can take my existing salvage title car and turn it into a formidable middle ground of all 3 under 50k and have it be exactly what I want it to be. Just a fun thought of mine. And yes a little bit is about knowing if I can do it or not haha.
Hahaha I love how you put that. Yea it’s a rough idea but past post have suggested that this would be too impractical so I’m moving on from the tesla idea.
Even if you somehow figure out how to make all that stuff physically fit, you’re going to alter the handling something awful.
I’m not saying you can’t, but if you manage to pull this off you should open a company and do this for a living. 
(and that suggestion stands regardless of what electric drivetrain you pick)
Thank you everyone so far for your advice, I have changed the name of the topic to fit the discussion better. Again tesla is out of the question, I underestimated its power Haha. I am looking for a smaller solution as suggested using a smaller battery and a easier to integrate electric motor. I am fully aware a ford fusion hybrid exist but with the drivetrain only being fwd, the transmission being cvt, and the electric motor itself being integrated into the transmission I cant see myself gutting the hybrid version just to be back at square 1 with my existing car. I want modularity (ei: tune ups, engine swaps, etc) like any other car but with an electric system like a hybrid.
Haha sounds like a plan for when I get out of school.
You have just enough education to think this possible but not enough experience to understand the task at hand. I was there once. I hold a masters degree and 30 years of automotive engineering experience so I have an idea of the momentous task you are suggesting.
And then this…
The answer is right here for under 50K
This fully engineered car is likely nicer, faster and more well integrated that anything a newly graduated engineer-car enthusiast could ever create on their own.
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Under 50000.00 ? I doubt that and being a salvage vehicle there is not much chance of having insurance to cover even part of the expense of this venture . And if life changes require selling this thing finding a buyer is really going to be difficult at even 25 % of the cost.
Out of curiosity could you customize a tesla? Also great find but dont these usually go for 35k?
True. It has some sentimental value if I’m being honest as it was a gift and I want to be able to use it for a long time with no plans of selling. Now this can either be a dream car or a car in my dreams haha.
Go look at the Tesla site (you have done this, right?). $40,000 base, so most sell for more.
Another alternative is waiting for the rumored v8 hybrid ford is making for its mustang, from their all it is is just upgrading the interior for luxury.
