Rx8 Electric Performance Hybrid?
 

I have been playing around with an idea if its possible to convert a Rx8 to a electric hybrid.
I have no idea if this is possible to do in the way Iam thinking, but its fun to share ideas like this and discuss it, i know this has been done on other cars but for fuel saving only, I have not found much information further about it to use it in a setup like this.
Electric Hybrid on a Rx8?? That sounds like a boring environmental prius shit you might think..
Most hybrids are made to save fuel and environment, but what if you connect a strong electric motor to assist the rotary engine, there is no plans of saving fuel here only performance boosting (all though you could set it up for fuel saving if you wanted to).
Batteries is my main concern, they can add a lot of weight to the car when you need a lot of them. So what if we only use the electric motor to assist the engine when you want to accelerate, like under WOT. Then we would probably only need a "small" battery pack.
The el motor could be hocked up with the drivebelt to a modified "crank" pulley, a micro controller could read the rpm values and throttle position from the OBD so we have some kind of management for the el-moter and we can control what we want it to do through a electronic speed controller.

The big advantage from the el-moter I believe to be high torque from low rpms, so under WOT it could kick in from 1000rpm to 6000rpm or more if possible.
So my vision is that from the rotary engines perspective this will be like accelerating a light car down a steep hill.
But I have no idea how much gain you can get, total weight and total cost yet.
Will the Eccentric shaft or "crank" bearing handle added force to the pulleys
And will it be worth it at all?

I have been looking at 10KW - 20KW motors from golden motors which i think should give a decent push to the rotary engine from low to mid/high rpms.
It will however require 100 volts and 300amps to get full effect of the 20kw version, but we only need it for a few seconds depending on how fast you are going to drive.
This will work as a performance booster only when you step at WOT.
And you will need to charge the batteries when they are empty as the alternator will not be charging this system, this would give powerloss, but it could be possible to have charging system when the motor is passive under normal driving.
I don't know how much friction there will be when the el-motor is passive and there might be need to have some kind of clutch system to disengage the motor under normal driving.
I don't know if this has been tested on a Rx8 before, and there are probably a lot of people who have had similar ideas.

I made a illustration of the el-moter mounted to the Renesis in photoshop which consist of a "crank" pulley with double slots (the AC is currently ignored), a mounting plate for the motor, and the motor, it is not in the correct scale and its not mounted realistically in terms fitment and free space available in the engine bay, its just for illustration purpose.
Its basically the same progress as installing a supercharger.

https://www.rx8club.com/attachment.p...1&d=1397334596

This setup is not intended to give much gains on high rpms, but to increase mainly the torque and hp at low-to mid rpms to get a kick ass acceleration, it will kind a compensate for the drivetrain losess and it will feel like there is very low inertia, like WOT down a hill, if it works how i want.
So I don't think there will be any need to tune the PCM either as the rotary engine will do the same amount of work, only reving much quicker and easier.
But it may be I'm wrong, just think to myself hehe

It's theoretically possible, though would require quite a bit of engineering.

Some ideas for you:
- Convert a turbo's manifold and exhaust turbine to drive an alternator to charge the energy storage (battery, flywheel, whatever), so you are only charging with waste engery instead of borrowing power at one point to supply it at another point.
- Use a flywheel to store energy instead of a battery. You would need some different electrical charge/discharge electronics and hardware, but not really anything different than a battery pack, and it's far lighter. For example, the Porsche Hybrid race car concept in development uses a 31lb flywheel spinning 36,000rpm to store energy, which stores enough to provide 200hp from a pair of electric motors for 8+ seconds. A lot lighter than 500lbs of batteries.

Do it. The motor should work to recharge the battaries. Make sure you use captive discharge battaries or capaciters.

RIWWP
Great ideas, a exhaust turbine alternator that is something we all shoud have on NA, tho it will complicate the installation and be pricy to have in this setup I think. The 36000rpm flywheel sounds sick as f**k, the downside is probly a big delay if you want to trigger it multiple times, and how does it know when you want to use it? Does it start spinning once the car is on?


LOGALINIPOO
Do you mean using the el-motor as a alternator when not at WOT? It should be possible to regenerate power with a elmotor when only the rotary engine is running but it will cost performance.

I wonder if these types of elmotors can spin free when you are not putting power on them, if so this would be a lot easier to build.

It's the same challenges of using a battery for energy storage. The example I used doesn't discharge the RPM all at the same time, it's using the kinetic energy to supply electrical charge, essentially being an alternator.

Spinning it up can happen a number of ways, like using exhaust energy, engine load, solar power, whatever you set it up as. It's just a method of energy storage that doesn't have the weight penalty of a battery.

This is perhaps the best article detailing the type of hybrid setup you are considering: Porsche 911 GT3 R Hybrid 2.0 First Drive - Autoblog
Another first-person review of the car, more driver focused: http://www.roadandtrack.com/car-revi...t3-r-hybrid-20

The Audi hybrids in the LeMans series are done essentially the same way, though different exact implementation.

Very interesting article, and impressive hybrid platform.
This looks like the optimal way to make a hybrid, but too difficult to do as a diy project.
I think I will look into a battery back solution which is able to run the elmotor for about 30sec or so, and if the weight is low enough it should be do able to make some decent 0-100km/h acceleration times. I want to see if its possible to make a kit for ~3000$ that will make the low end torque a lot better. I should be able to calculate the minimum battery pack, weight and performance increase, and will see from there if its worth it.

Bump from 2019. Did anyone try this out?

I doubt anyone has tried this, but the flywheel idea that RIWWP mentioned sounds really cool...

An LS engine will do the low-end torque thing pretty well and is a lot cheaper to apply, not to mention a lot less complex.

The only thing a hybrid can do potentially better is fuel economy, but given the extra money you need to dump in to make a hybrid drivetrain work well, it will take forever to offset the difference. Not to mention, some performance hybrids aren't great on fuel, either. 2nd Gen NSX makes 573 BHP but gets 21 MPG both in city(not bad) and highway(horrible).

True, but then you would lose the rotary... but if you are going that far, might as well just put a 20B in it...

I am not a fan of LS swaps on 8s, but since we are talking about hybrid here, all bets are off. Neither of them are "cool" in an RX, per se.

I was in a hybrid race car club and I took a course on hybrid vehicles. It's like the leader of the club said, "Making a hybrid is easy. Making a good hybrid is really hard."

20B swap, again, is not easy. Find a 20B engine on its own can be a challenge, and that's just one of the many can of worms. Hopefully you have literal mountains of cash beside you if you try it(same goes for the hybrid idea, really).

A 20B is going to be at least 2x the price of an LS (which is already going to start out around $10k). Probably closer to 3x or 4x.

Lets be honest, the rotary is neat but that price delta is bananas.

no, they’re too busy living in fantasy world ...

:rollingla

I am interested, anything like in wheel ?
110 HP with 590 lbft insta torque

There are a bunch of Miata conversions that should fit in an 8 and are almost at the point of being complete kits that don't significantly alter the weight, balance or power-to-weight. Given the price of replacement rotaries, it's no crazy...

The biggest issue with hub motors is that it adds a crapload of unsprung mass. This is especially not great for high-performance applications, but even from a comfort-oriented NVH view, a higher unsprung mass is undesirable. Why do you think no OEM has adopted this technology yet?

I am not sure how a hybrid conversion would work, particularly in a performance application where low-end torque doesn't matter as you'd be revving the engine high anyway. The cost would also be pretty high once you toss a few batteries in there. The batteries will also eat up some interior room and add weight. Not as much as a full EV, but still.

I meant full electric conversions. They seem to either put the motor where the engine is, and retain the trans, or put the motor where the trans is and use the underhood space for batteries. Seems not terrible, and we only have more space.

you’d be better off spending the $15k for a shrink to figure out why your head is not screwed on straight …

Love you too Team.

I don't think Team is talking to you, but not sure here.

I think EV builds are cool as well, though those performance-oriented ones probably don't have many batteries to minimize weight.

it was just my usual snarky, aloof general comment; dumping that kind of money just to convert an old Miata to battery power seems a bit off kilter imo …

just because I think somebody’s head is either not screwed on straight or buried in a dark place doesn’t mean I won’t have their back when they really need it. The things in general that go on here with this forum can mostly be summed up as petty and meaningless worldly crap. In the end, none of this will amount to anything more than dust; from whence everything came, there it shall return.
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Reviving an old thread it seems. I am contemplating the same idea outlined in the opening post and just stumbled onto it after putting some thought into it. I believe the objectives are still valid and the method is the simplest way to boost bottom end torque. My objective will be improved performance 0-100 kph times but I think there can be a payback based on current fuel cost and say a 20%+ reduced consumption. Theres more choice in motor and battery now than when this thread was started and given my goals I’d go with supercapacitor for energy and regen.
Anyway i’m in hibernation until June so plenty of time to come to my senses.

Doing it for the fuel economy will be a bit like paying $20k+ for markup on a Toyota hybrid nowadays because "gas is too expensive" without doing the math to see how long it will take for the fuel cost to offset the markup, especially if this is your second car you don't drive much.

Doing it for the performance is cool, but I just don't think the cost/benefit ratio is there vs. established swap options like REW, LS, or LFX swaps.