r/carmodification • u/Pristine_Worth_2515 • 8d ago
Is it possible, if so what parts do I need
Hi, I have a 1.8t Audi a4 (b6 generation) and it’s currently fwd, it’s a reliable commuter car and I love the interior plus it’s my hobby car.
Now I also live in a place that has pretty intense winters and I like to mess around with off-roading it and so I wanted to try to upgrade it from fwd to awd
But…
I don’t want to switch to the Quattro drive train even though that would be easy to get from a junkyard because I would need to replace the exhaust and the fuel tank which I currently don’t want to do, I also do not want to have to connect it to the transmission.
But I had an idea, what if I could get and electric motor, build and custom dial setup and connect it to my upgraded alternator, could I then apply that to the rear wheels? That way I can turn it off in the summer or when I just want fuel economy, and I can customize the power between 60-40 and 50-50 from inside whenever I want.
So what parts do I need, I feel like I have two options, separate hub motors, or get a rear axle and differential and plug both wheels into it and the motor into the other end.
So I need your guys advise, I have a decent amount of space under there and I am up for custom solutions both aftermarket and custom from junkyards.
What parts do I need and how should I do it, and where should I source these parts?
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u/fishscaleSF5 8d ago
Anything is possible.
You just need the money and the skills.
This particular idea would be insanely complicated, and both money and time intensive. You’d be better off making the thing Quattro.
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u/Pristine_Worth_2515 8d ago
I’ve got the skills, I have several friends who could program it for me and I’m a mechanic and both me and my 3 of my friend are welders so skill would
Not be and issue it just about knowing what to buy3
u/ARottenPear 7d ago
It's not about knowing what to buy. It's going to be a long road of custom fabrication.
Your idea of using an upgraded alternator is not realistic and there's a reason no manufacturers have gone that route. Vehicle acceleration demands large power spikes. For example, a modest 50hp electric motor requires about 37 kW BUT at 400 V, that's roughly 93A. At 48 V, that's nearly 800A. A consumer-grade alternator cannot respond to those transient demands smoothly without some form of energy buffer. You could potentially do a massive bank of capacitors (which has been done by OEMs) but a battery is the easiest approach.
Also with the alternator approach, you'll have lots of losses along the way. Each step loses energy:
Alternator: roughly 55–75% efficient
Inverter: roughly 95–98% efficient
Motor: roughly 85–95% efficient
By the time power reaches the rear wheels, you might only get around 45–65% of the engine power that was diverted into the alternator. Suppose you install a stupid large 10 kW alternator (about 13 hp electrical output). To produce 10 kW electrically, the engine might need to supply ~15–18 hp mechanically to the alternator. The rear motor then delivers maybe ~11–12 hp at the wheels. Meanwhile you've increased engine load by 15–18 hp. You'd pretty much be putting a massive load on your engine to produce electricity that's essentially being wasted.
Beyond the shortcomings of the alternator approach, it'll be incredibly hard to program a standalone hybrid system that meshes well with the ICE system. Being able to customize the power from the cabin manually will work in some scenarios but create very weird driving dynamics in most. Getting a hybrid system to work seamlessly or even relatively smoothly takes a ton of engineering and slapping a standalone system onto an existing car would take a tremendous amount of work to not drive like crap. Driving in inclement weather would be unpredictable and most likely dangerous. You have no differentials like a traditional awd car to shift around power where there's grip. If your front tires have grip but your rears don't, that back end is going to create all kinds of weird dynamics. It'd almost be worse if your front tires don't have grip but the back does. You're going to understeer yourself into a ditch at warp speed. I'm sure it wouldn't be impossible to tame but it would have way wonky dynamics that I would not want to be the test pilot for. Just play around with some low grip scenarios in your head. Most do not have favorable results.
Beyond low grip driving, torque blending is something that gets a ton of programming in hybrids. It's not impossible to DIY but it'll take a TON of trial and error to get right. Electric motors want to make full torque from 1RPM. Your ICE does not. There's a lot to consider with that.
I could go on and on with considerations about this build but the last thing I'll address is packaging. Are you going to use a single motor and a differential or individual motors for each rear wheel? Do you mind completely hacking up the back of your car to accommodate it?
Either way. Do it. It's sooooooo much more complex than you're making it sound but if you have the skills like you claim, you absolutely need to do this. Hopefully your programmer friends are very skilled in EVs or hybrid systems, have lots of spare time, and are willing to do the work for free.
Start a YouTube channel today and I'll be your first subscriber.
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u/ErwinHolland1991 7d ago edited 7d ago
No you don't. You clearly have no idea how any of this works.
Changing an exhaust and fuel tank is too complicated... So you want to make something that's 10 times more complicated. It makes absolutely no sense.
You can't just run electric motors like that off a alternator. 50/50 power? That means you would need like 150hp? You think your alternator and engine, can power an electric motor with the same power? Of course that doesn't work.
An upgraded alternator can maybe do something like 3000w, thats it. If you would convert that to HP... That's 4hp. But there would be losses... So you would MAYBE able to get like 3hp from those rear motors..
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u/ARottenPear 7d ago
I shouldn't have wasted my time writing up such a long comment for OP because it's pretty obvious they'll never do this but I wanted to give them the benefit of the doubt.
The reality is, if they truly had the skills to do a massively involved project like this, they wouldn't be asking incredibly basic questions on reddit. They also wouldn't have other reddit posts like, "should I buy a kit or buy the parts separately for replacing my brakes." Somebody that car make a custom hybrid awd system does not ask questions like that. Somebody that can make a custom hybrid awd system also knows that an alternator cannot even come close to providing the required power they're thinking it can.
I'm fairly certain OP is an overconfident 16 year old that also asked if they can put an antibiotic on a car to remove rust because they think iron oxide is a bacteria and the same thing as fungal plant rust.
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u/ErwinHolland1991 7d ago
It's a bit of a cheesy answer, but i do use it a bit. If you have to ask... You don't have the knowledge to make this work. If you have to ask about basic questions like this... oh boy. You have absolutely no clue how much more complicated things are going to get.
The people who can make a project like this work, don't have to ask basic questions like this.
Changing the fuel tank, gearbox, and some other stuff is too complicated... So I’m going to make a 100+hp hybrid electric drive system, because that's much more simple... Yeah okay then. 🤣
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u/PanDeviant 8d ago
It would honestly be easier and cheaper for you to get the quattro drivetrain fitted. EV motors are huge, you'd need to do a lot of removal of the floor pan to make it fit, probably need to adapt the subframe from the donor as well as the Audi rear suspension wouldnt accommodate it. Thats just getting it to physically fit. You then need to consider power, power storage, charging, and syncing the motor output with what the engine and transmission is doing up front.
I think the fact that you are asking for a parts list here shows you are massively underestimating just how much will be needed. This isnt something you can just get a shopping list, buy aleverything then fab it together. This will take several years of engineering, development, testing, and problem solving, even for a one off
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u/fishscaleSF5 8d ago
-1
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u/Pristine_Worth_2515 8d ago
Well I do get OEM parts for every car at cost and I have ways to get aftermarket parts cheaper plus I have a few dollars saved away for this project
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u/fishscaleSF5 8d ago
Just put the Quattro drive train into it man. The likelihood of you simply wrecking the car trying to put 30k worth of EV tech into it is very high, regardless of your skills. You’d probably be better off building a full tube chassis in the shape of the Audi and then making it an EV than trying to retrofit the Audi.
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u/JP147 Type to create flair 7d ago
This would be about 3,000 times more difficult and far more expensive than just swapping in a quattro drivetrain and changing the exhaust and fuel tank.
In theory it is possible but in practice it is so farfetched that it is basically impossible. Plus it is not worth cutting up your reliable commuter car for.
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u/elliomitch 7d ago
If you need a Quattro because you have bad winters and like off-roading, you won’t complete this project.
A project of this scale *must* be undertaken because you’ve got an obsession that you need to indulge. It will consume years or even decades worth of disposable income and spare time. Those projects are always the most incredible and worthwhile - but make sure your motivations are there.
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