DIY Hybrid-ing old cars with low budget, is it possible?

[Leo.IT]

Hello everybody!
After a period with some problems with my old Renault, seems that she's finally working the way it should be.
So I'm having a lot of strange ideas in my mind.
The car runs good but it's not very efficent, the tyres are quite small (145 or 135/80 r13) and the car is lightweight (700kg) but the engine is really old and it doesen't help to improve mileage (15 km/l).
I was wondering if it's possible to realize some kind of hybridization of an old car like that, with plenty of space under the bonnet and in the trunk.
I'd like to get my hands dirty in a summer project, something not too extreme.
I saw hub brushless motors, drum brushless motors, but it's quite hard to have a clear idea of the situation.
I think low powers (less than 10 HP) are enough for a car that, brand new, had 34 HP!

[Daox]

Its quite possible. It also not easy and quite complex. Definitely much more extreme than most here have tried.

[oldtamiyaphile]

I'd put a Fiat Twinair in it and call it a day. With only 700kg to push it would be a riot and the low loads would make it very economical, at least at lower speeds. 3l/100km shouldn't be hard.

The R4 is manual I presume? Adding hybrid is tricky because you have to work out how to actually control it during gearshifts. If you just do something like an E boost button that might be easy but you'll loose some of the benefits.

It would probably be best to just go to full EV, as even small motors will probably provide more power than you have now.

[Ecky]

My understanding of mild hybrids is that most of the savings come from being able to downsize the engine, which you're obviously not going to be doing by bolting on an electric motor to the existing engine. You'll be able to recover a little bit of energy that would otherwise be lost doing braking, but it might not even offset the additional weight of the batteries.

[freebeard]

Seconded on the pure EV approach; but if you want to do something and not screw up a nice car, consider a pusher trailer.

[elhigh]

Get a good Lombardini diesel and drop that in. That would be easiest. You would just have to come up with an adapter to attach the engine to the existing transmission, but lots of people have done stuff like that already.

I like the idea of adding hybrid capability to the car but for the shadetree mechanic it would be really difficult - you would need to create and install a completely new drivetrain, either to replace your existing one or else to replace your undriven axle. The latter would actually be easier, I think. But going this route would add a lot of weight to a car that doesn't have a lot of capacity in the first place.

Another concept would be a series hybrid. This would also completely replace your existing drivetrain. An electric motor would become your prime mover. You would have batteries to provide surge power when needed, but there would also be an engine powering a generator. Ideally the engine would be just powerful enough to provide slightly more power than the vehicle needed at a steady cruising speed, which gives the designer the opportunity to install a smaller engine and run it closer to its most efficient speed. The slightly excess capacity and regeneration would provide the extra power needed (stored in the small battery pack) for acceleration, hills etc.

Not many go this route. I first read about it in Mother Earth News in the 70s; Mother then tried it on their own a couple of years later and reported that it did okay. But it's a squeeze getting all that non-optimized hardware under the hood.

Hmm. I wonder what the dimensions of the Prius C's drivetrain are, and how well you could fit something like that under the hood of your battered old 4. That would buy you all manner of hybrid capability, ready-made.

[oldtamiyaphile]

Originally Posted by Ecky

My understanding of mild hybrids is that most of the savings come from being able to downsize the engine, which you're obviously not going to be doing by bolting on an electric motor to the existing engine. You'll be able to recover a little bit of energy that would otherwise be lost doing braking, but it might not even offset the additional weight of the batteries.

DIY budget hybrid won't have regen capability.

Originally Posted by elhigh

Hmm. I wonder what the dimensions of the Prius C's drivetrain are, and how well you could fit something like that under the hood of your battered old 4. That would buy you all manner of hybrid capability, ready-made.

That's really the only way to go IMO. I think European legislation makes that sort of thing nearly impossible though. I'd love to put a Prius drive train in my Renault Van, but really I'd likely only pick up 1l/100km and lose my towing ability.

[MobilOne]

Your best and quickest payoff would come from extreme hypermiling where possible. All the other options would likely never pay for themselves.

[elhigh]

Originally Posted by MobilOne

Your best and quickest payoff would come from extreme hypermiling where possible. All the other options would likely never pay for themselves.

In my mind none of this is ever about "paying for itself." The money I spend on fuel is never going to pay for itself. Making the car better than it is is the point I'm pursuing, not an economic goal but a performance goal. The economic improvement of the vehicle is a plus, something that merely reduces the impact of the investment. If it completely pays back the investment, well and good.

[Frank Lee]

I think the path of least resistance if often the best one to take; many of us suffer from delusions of grandeur in our ability- technical or motivational- to complete such a project (noodling it and starting it is the easy part).

It would also help to evaluate your usage patterns- lots of city and mixed city/rural driving is where hybrid tech really shines; mostly highway cruising like I have wouldn't pay off.

Is the stock engine worn out? What would the car's economy be with a stock overhaul or even lightly modified like "RV cam", hot ignition, and the like.

Next step up in effort and expense is an engine swap. There are loads of more modern, more efficient engines to choose from. Maybe swapping in a modern 5 speed transmission along with a new engine would be the way to go. I can see a 3-cyl/5sp m/t Swift drivetrain moving that car right along while being efficient.

Or add an electric motor. EMer Brucey did but he didn't rave about the results. His was a helper, used on acceleration. I'd do a standalone, divorced from the ICE.

P.S. Doing the EV part is possible on a small budget. Study up on MetroMPG's EV projects.