Dual Fuel, electric rear wheel drive, gasoline front wheel drive
 

Since most of us are modding gasoline power cars or replacing gas engines with elec motors and batteries I had this concept. If it has already been invented please let me know where to get one, if not someone here should get on this and the profits are all yours.

Concept: traditional front wheel drive gas powered car has a rear axle which is really nothing more than a trailer axle. Small lightweight cars on the highway only need to overcome air and rolling resistance to move along at cruising speed so horsepower required is low, especially in well areomodded cars.

Replace the rear axle with either 2 motors, one mounted on each reat axle shaft (imagine the rear axle from an S-10) or one large motor mounted where a traditional driveshaft would enter the reat differential. This motor could even be mounted vertially as to put the motor in the trunk to reduce the amount of junk hanging below the vehicle.
place batteries in the car trunk to power the rear electric drive, use regen braking to recharge (maybe)

Car could be run in either mode by putting the front or rear systems in neutral and driving off your choice of power. using a plug in system at home and making short trips you may never have to run the gas motor. Since city driving kills overall mpg you could use elec mode for getting through the city and once on the freeway on ramp switch to gas power where your gas engine, geared high and run at constant speed would be more efficient and have all elec needs fed off of batteries (water pump, power steering) so the engine could be just for driving.

But for now lets start with the rear axle swap out could be just a bolt on system for most small cars, with a battery bank in the trunk, of course Ni-Cd or LiH batteries would be best for weight but the cost factor is still high.

UW Madison fuel mileage challenge team did that with an GM Equinox. Their largest problem with this setup was the regenerative braking only on the rear wheels doesn't let you recapture much juice compared to front wheel regen.

Its been thought up before, just never done by OEMs.

Very similar concept as the XR3 (XR3 Hybrid: Personal Mobility Vehicle (PMV) Automotive Prototype Project)... though that is a "plan-built" vehicle. Diesel powered front wheel drive, electric powered rear wheel drive.

Cool idea!! :thumbup:

I like it, but using an AWD car (or one with an AWD variant) would be true "bolt-on." Looking at my Accord, it seems likely that cutting and/or fabrication would be involved. One way to keep the motor out of the sludge would be to have it facing down out of the trunk, and rotating the differential so the coupler is pointing up. Anybody see a problem with this?

Could be done with a RWD pickup too. Run the normal RWD gasoline drivetrain, and then put in a FWD differential and axle and direct-drive it. Like Daox said, you get better regen off the front (more weight transfer means more regen before skidding starts.)

There was a concept mitsu Eclipse that had gas front drive and electric rear drive... never went to market, of course. This was maybe around 2002-2004?

Dodge Durango Hybrid - Tech Stuff/Green Machines/Car Shopping/Hot Lists/Reviews/Car and Driver - Car And Driver

Dodge's "Through the Road" hybrid, never got to market. One cool feature was that the electric drivetrain could cover the hesitation while the automatic transmission shifted, resulting in smooth acceleration.

VW Golf Twin Drive prototype pretty much matches the description:

http://ca.youtube.com/watch?v=wcOd_NCbMsU

Details of the VW Golf Twin Drive:

VW Twin Drive Is German for Volt | Autopia from Wired.com

It's an interesting setup.

Cute!! Car's not bad either... ;)

So... Don't electric motors typically have two sides to the armature?

What would keep someone from mounting it between the rear hubs of an AWD car, and using a custom drive shaft on each side? I know that bench grinders (not enough power, I know) have dual shafts on them, and I can't see a reason why an armature could not be modded or a custom armature built by a machine shop that would allow for such a mod..

The cool thing is that if it were only used for acceleration assist it would only need little added weight from batteries... it's not like the engine won't be running, and producing power from the same fuel that it would be burning anyway is only logical, or at least using an alternator at idle to load the engine a little bit to help provide that power to reduce weight of batteries, but only using the alternator when the e-motor is working.

Conversely, using an e-motor of good size would limit the actual ICE power needed to keep the vehicle at a constant speed, or even to accelerate, so a smaller gas engine could be used.

Just tossing that other stuff out there, but primarily the idea that you could power the rear hubs of an AWD vehicle quite easily/cheaply (custom CV axles aren't THAT expensive.)

no diff :confused:

yah, without a differential you'll drag the inside tire around corners because both tires will be traveling at different speeds as your turn. I suppose you could just power one wheel or use two motors on different wheels. I like the idea though.

PS Do it and show us how you do it:)

LOL I forgot about the no diff thing... would be great in a straight line though!

Ok, so diff stays, motor gets mounted to diff... IRS is still a better option though, b/c with the motor mounted hard to the diff, it's putting more weight on the suspension. with IRS, you're putting no more weight on the suspension than was already there, and you're not incurring any more frictional losses than you would be with a solid rear axle.

In fact, I tend to think you're actually incurring slightly less losses with IRS, b/c you're only subjecting the diff itself to fluid drag, and the axles never see the associated "swimming".

Of course, given that CV axles are most efficient when working in a straight line (in a line that would be suited to a solid axle), you're probably losing that same efficiency gain b/c they're almost never straight.

It still would reduce suspension strain though, (unsprung weight) which is everyone's complaint when coupling motors directly to wheels, even though you can get rid of a large amount of weight at each wheel when using electric motors. (You don't need brakes anymore, technically.) (Legally, you still need them.)

Im new to this whole idea so bear with me while i try to explain it. What about trying something like this in a pontiac fiero. Mid-engine RWD, so you can use the front, one motor on each wheel. You would get the better regen braking, increase performance and get better mileage from the ICE. my biggest question on that is how do you get the front wheels to travel at the same speed as the rear?

You don't, really. Realistically, you can get away with separate throttles for both electric and ICE, and under light throttle it'll self-balance. Ideally, you would use a controller that provided traction and torque management to both engines at the same time.

The Poulson hybrid system mounts two 7 hp electric motors on the outside of the rear wheel hubs of a FWD car. They are designing it so it can be installed on any FWD car.

If you're adding electric RWD to an otherwise FWD car you can save some coin or get more robust shafts with universal joints as rear wheels do not steer. Also universals shouldn't be run straight anyway (it keeps the needle bearings from spinning properly), so you'll be good.

IRS would be better, but not all vehicles start out with IRS and this conversion would be problematic for suspension mounts. You could turn a beam rear axle to a live axle, body-mount the motor and shaft-drive the diff to minimize unsprung weight, although a live axle adds a lot over a beam axle in a FWD car.

I posted a similar thread about 6 months ago, called poor mans hybrid. obstacles would be for the end user, having to modulate two throttles. The guy putting it in himself wouldn't care. Not everyones a "mad scientist" so being user friendly would drive the cost and the research up, only afforded by the big car companies. I would totally go for one with a small ac motor in the back operated with a twist throttle, and relocate the e-brake handle or something.

I've had the same thought, since there hasn't been a light weight RWD compact since the 240sx. Everything's FWD and the Rear is where I'd want the acceleration to go. Making a hybrid just seems the practical solution except everything would have to be DIY fabrication.

Please link your topic getnpsi. I'd like to see it.

I don't think the two throttles would be a huge problem since mixing and matching would only be done during WOT, at least IMO. If we're going slow, just shut off the engine because low load efficiency blows anyway, and if we're above a certain speed where it makes sense to run the engine because it's operating efficiently enough, just make sure the electric motor in the rear doesn't engage unless we turn it on or we have something where it'll kick in at WOT or similar. Doing something similar with RWD is a bit easier as long as there is enough room to mount the motor behind the trans and shorten the driveshaft to accommodate the motor. From what I've read there's a ~1-2% drop in mileage at lower speeds due to spinning the motor around, but it's easier to use, and we can even run accessories on electric power by engaging the gear box assuming we can kill engine ignition, although it's pretty lossy spinning an entire engine over just to run an A/C compressor.

Load a 240sx with a buncha batteries and/or new drivetrain in the front and here comes understeer.

The poor mans hybrid wasnt my thread, it was a guy thinking of using an awd minivan, plenty of space to work out theory there.
http://ecomodder.com/forum/showthrea...ight-2233.html

I was thinking more along the lines of a Geo Metro with it's motor turned into a generator including removing the FWD. I figured it was easier to do that then deal with combining or manually adjusting the two throttles. You'd have to have a training session before anyone could borrow your car. The problem is still the prius inverter, 500volts straight to the motor during heavy acceleration or during highway cruising is a little harder to wire up. During that time it's easier to think the motor should be direct driving. But I'm fairly confident that running the fuel which I'm looking at ethanol through the engine which runs between 1500rpms and 3000rpms min/max, converting that with an alternator sized for maintaining a top speed of 70mph through the inverter to the motor hooked directly is just as efficient or within 10% of the 85% efficiency of the engine hooked up to a manual transmission and FWD drivetrain.

And getnpsi, that's why they put batteries closer to the rear wheels. It's easier to put more rear bias with the heavier lead acids. Just don't oversize the battery pack or overload the rear end.

For using an AWD van, it wouldn't be anymore fuel efficient unless it eliminated idling, maintained speeds below 35mph and limiting the engine to it's optimum fuel efficient range, which is 35mph in 5th gear for the Metro but can be upwards of 50-60mph in a lower geared sports cars such as the Corvette. And then you'd have to swap the engine for a smaller one to really reap the benefits, you won't need the big v6 anymore if you use the electric motor to accelerate to 35 and you'll eliminate the need for anything shorter than 3rd and 4th gear.

A Subaru would be very simple. Swap the AWD transmission with a FWD one (pre-1994, cheap, and would fit nearly any Subaru after 1990 that you'd want to use) and attach the motor to the rear diff. The cars are made so monkeys can work on them and the suspensions are built like tanks, too. Of course, that also comes with a bit of a weight penalty, but a first generation Impreza or, even a Legacy, is reasonable. Any suspension upgrade necessary to compensate for the extra weight of batteries is also easily done and available.

Yeah, Subaru. I'm only in preplanning, but I'm researching whether it'd be easier to get a RWD like a Mustang and put the ICE and a dual shaft AC motor inline and use a 2 speed powerglide converted to manual. I'm thinking that using the pedal with a potentiometer and converting the engine to drive-by-wire aka electric throttle control and using the same signal for the AC motor would be do-able but I haven't found out how yet. I'd like to use a 1.3l/1.4l converted to E85 which would be enough for 70mph max and I'd like to try something like converting to Atkinson cycle or 6 stroke but those are only dreams.

The easy part is putting an off switch for the ICE. But I'd have to put a clutch between the ICE and the AC motor and either manually switch on the ICE or get the ICE to switch on when the battery level drop. I'm thinking I'll just get a 5kw/hr pack of Thundersky's LiFePo and use something like the Prius'(the best example I've got) 40%-80% charge cycle. Without the v6/v8 and with a smaller battery pack and Aero mods it just might get the 40 mp(GGE) I'm setting as the projected goal.

You know, I get upset every time I see threads like this because I have an uncle who has the monster garage, every tool under the sun, the know how (he works for the power company) access to all the junkyard parts and controllers I would need to actually build such a car (and i have a spare subaru AWD wagon I could use or a neon coupe) .. and for some reason or another my uncle doesn't have any interest in knowing me for the most part.

I too, have wanted to retrofit a car with dual drive systems such as electric motor to power the rear wheels, and I'm so close I have everything I need except for the one person on eart who CAN help me make it all happen.

Well, we can all keep dreaming - but if he ever does gain interest in me and my ideas it'll be done.

Why Not Try Hand Throttles??
 

For the home-built special, why not consider the use of hand throttles similar to that used in a twin engined aircraft? if established with a electronic throttle control, you would effectively have easy control of both engines at the touch of your fingers.

http://www.ultralightnews.ca/fuelsys...s/IM000004.jpg

I've considered something similar for varying the degree of engine braking in an ICE. By varying the degree of EGR, fan braking, air-con temperature, you can potential vary the degree of engine braking experienced. [CAT haul trucks have their braking system lever next to the steering wheel. the emergency brakes on the older models are sprung loaded- perfect for braking on the straight.... and some corners]

If you were to maintain the pedal accelerator for the ICE, and still incorporate a hand throttle for the electric motor with forward and rear movement (neutral point- electric motor off, rearward-> increasing regen braking). A fail safe, similar to that used withcruise control would be needed to automatically stop forward electric motor propulsion when you touch the brakes or clutch for example.


The tech people would need to clarify for me how you would wire it up so vary the regen braking available.

I like the aircraft throttle idea. But I'm biased since I have a similar idea to use a hand throttle to manually control a CVT for a project I can't afford to build and probably never would as it wouldn't be practical, just a blast to drive and unlike anything else on the road.

Sounds like you got a cool uncle. You should really become his friend. Worst case you can help him with something and maybe he'll teach you something.


The problem with the aircraft throttle is the lack of a "centering" spring. In my mind that's just a necessary safety. With aircraft there isn't a reason to have the throttle revert to 0%. That is probably why a gamepad's control stick was being used in the other electric hybrid. But I see how hooking it up like cruise control might work. If the hand throttle is hooked up to the cruise control assembly, maybe the brake or clutch would cancel the input. Err, or not, I don't know.

Anyway, the hand throttle needs a potentiometer installed at the end of the stick. You wire uses a low power wiring rated in Ohms. If you use a 0-5k pot, you need wiring that does a little over 5k Ohms seems like 6.5k Ohms was about right. The wire then runs to your controller. If you had a controller to look at with a manual it might already include the specifics. And I'm not sure to the accuracy but hopefully that's gets you looking in the right direction.

I'd also like to be able to vary the regenerative braking as easy as I press on the power brake too. Removing the brakes on the driven wheels is probably out of the question whereas a motor might pull hp from generating electricity which creates "regenerative" braking I believe the power brakes generate more stopping power to the wheels. But I don't know. It's hard enough to get continuous power ratings from electric motors, manufacturers don't include rated stopping power with their factory brakes. Maybe there is a table on it somewhere.

And @evolutionmovement, why a manual controlled CVT? Couldn't you just run the engine RPM off the throttle(hold on while I explain this), the engine RPM that that the CVT maintains based on the throttle input. Eg, <50% it's in low RPM/FE range 50%-75% it's around the torque peak and above 75% it's trying to stay close to the HP peak? Maybe a little too much programming :p. Anyway don't pepper thread please. Now I've gone offtopic.

I agree about he centering spring, it would take a bit of work to enable the throttle level to do this mechanically.

It would obviously depend on the intended use...
and the amount of electric assist desired when operating the ICE.

my thought would be to use the electric motor to drive up to 40 km/h (25 mph), then engage 5th gear wit the ICE, maintaining some electric assist to avoid lumbering up hills. Or one could start rolling under electric (say 25% duty), then accelerate as normal with the ICE (however beginning in a higher gear say 2/3), then reduce electric motor duty to 0% once cruising speed reached.

What motor are you considering? 35mph/60kmh is closer to optimum, you're probably not going to maintain electric power for very long and 35 should be enough for 4th gear at least. Some could probably hit 5th but conditions vary.

BTW, for future reference the only reason to use electric power to assist the ICE is when you've undersized your engine and absolutely need the power. It's just for safety when merging onto highways or for a burst of power(which isn't a design goal here). ICEs are more efficient under heavier loads such as acceleration and cruising speed. Where the electric works better is outside of the bell curve that the gearing gives your ICE but usually limited to the lower speed range. For an ICE that curve (thanks MetroMPG) doesn't hit good FE until the lowest speed you can power through the highest gear without bogging.

I think Daox and MetroMPG have stated this already but I just wanted to make sure you were on the same page, Aussie. Hopefully I have my credits right, if not, you know who you are...ah crud, who was it?

If you run the motor inline with the engine with a clutch between, you could probably ditch the starter as well. Save a little weight, but you'd lose a little redundancy in case of motor system failure. Could you then, too, if using an A/C motor, use it as an alternator while off throttle or when using the ICE?

Allch Chcar, it's totally off topic, but the idea for a manually operated CVT is to replicate the feel of a variable pitch prop on a 3-wheel tadpole vehicle that resembles a Gee Bee R1 fuselage with a Focke Wulf 190 canopy powered by a 7-cylinder radial engine under a NACA cowl. I thought it would be fun and efficiency and practicality have little to do with the design, but the 20k+ for the engine alone permanently shelves that idea. Even if I had that cash, I'd rather give it away. Maybe.

More possibilities than flies on a dead Kangaroo's Bum
 

Please accept my example and as example only (i based this example on the little amount that i have read about the Honda Insight (a small ICE with electric assist)..... i wished it to simply demonstrate one of the thousands of possible configurations that could be used dependant upon an individual's vehicle and driving requirements.

Me personally, in my old GMH automatic, i would love to try using the ICE to accelerate to 40 km/hr (using optimum throttle position, at which the transmission changes into top gear), then use the electric motor to assist up to 60km/hr; which is a little sluggish. That makes the best use of the torque of the engine/auto trans to accelerate to 40km/hr. Above 60 km/hr it accelerates quite well using the optimum throttle position (arrived upon by many years and kms of monitoring the 'grand daddy' vacuum gauge). Having said that, I'd love to verify this will some real time fuel consumption gauge. [sigh].

The starter would indeed be removed. In case of motor/controller failure, the motor will be freewheeling and bumpstarting is still possible. Same workaround as a broken starter.

Removing the pulley and belt system and converting everything including the water pump to electric would be another modification as the motor would be designed to function for both powering the wheels at low speed and alternatively for generating electricity to the ECU, lights, powered items, etc during ICE cruising. All of those things are usually covered by an alternator that generates a maximum of 100 amps at 14volts. Since I'll probably forgo using the motor past a certain point, the batteries will only see a lot of recharging at low speed. The car would remain functionally an ICE powered car at cruising speed where an electric can't match the range liquid fuel provides. Controlling the power generation is something I'm looking in to as well. Otherwise the design wouldn't meet design specs. Outside of recharging the battery the system will need an estimated maximum of 200amps of 12volt power, after everything is converted to electric that is. And that's just as a bullet proof concept. It would probably work with less during cruising :turtle:.

Aussie, it sounds like your engine is acting exactly inline with what I'm saying. At 40km/hr your engine is bogged down in top gear and it's underperforming and overworking itself. At 60km/hr you can use the ICE comfortably, accelerating or cruising. In both your case and mine, an electric motor that can maintain 60km/hr would be a great starting point for converting to a hybrid.

Please notice I'm avoiding mention of the use of gasoline. If I had it my way. The vehicle would not only be RWD, have an electric motor and batterypack, and two speed transmission. It'd use pure ethanol(in my case at least). Three things the automakers don't offer in one package.

I considered an AWD but the reports that even a manual transmission car suffers from 25% driveline losses which I know automatic cars get with only two wheel drive front or back. I say 15% is too much, we're talking about 10% more of our power and energy turning into unused heat for a little bit of convenience. Small things like that make our markets unsustainable and our governments chug from the corruption.

Sorry to rant and waste some of your time. But another thing, a FWD hybrid isn't a viable DIY project outside of a beer budget because a Prius is already very cost effective. All of the RWD hybrids are SUVs or trucks designed for the power increase. All electric sportscars are still just exotics. Sheesh, even the RWD cars are reserved for those who can afford a $20k vehicle. I'm thinking this system I'm developing/researching will be better suited to a low-end sports car that can be equipped with a 100hp ICE and 75kw electric motor. I'm also having second thoughts about retiring my Ranger. As great as OBDII is, the newer Rangers run more HP for the same economy and this project might work out better with an older DIY vehicle. I already know I can get flexfuel info from the 3.0L Rangers, the electric motor used in the electric ford ranger, and I can keep my RWD without doing extreme modification of a transverse compact car or selling out for a Mustang. I'm starting to smell the Roses of success in my future.

Best Bet for regen braking is to have 2 static positions for ease of use and to avoid motoring an engine somewhere.

I used to help a summer camp and we had an electric narrow gauge railroad 20 passenger cart. It was an aluminum flatbed with welded on assemblies that were seats/battery shields. You had forward and reverse power but then we switched it to neutral on the way back because it was down hill the whole way.

The cart had two, I can't think of the word for them, switches you lift to activate. Each put one of the two motors into braking. Under one click you would not really gain speed down a 2% grade with 20 people and lots of climbing hardware and lots of batteries. With both down it would lurch when you activated it and kept the cart at reasonably low speed.

I always coasted to high speed and then engaged one and then the other about 1/2 mile from camp(six miles one way).

The advantage of the static was if someone who didn't know anything about driving it clicked one of those up while they were moving it disconnected the "throttle" so they couldn't short circuit the batteries or burn the motors out. We didn't think to connect the brakes to the same switch. Mistake.

Also it had a governor so if the wheels started turning fast enough it triggered a solenoid that snapped both switches active. It would not be able to be driven since the throttles were disengaged and then told us who was no longer allowed to drive.

If my calcs aren't off, and you take a 3000 lb car, like the Prius, and its going 60mph, and it stops in 143 ft, it uses 201hp for 3.25 seconds. Brakes can provide a tremendous amount of power dissipation. How often do you need to do a panic stop? There's always some idiot out there that doesn't know how to drive, and forces you to drive out of the ordinary.

I can never see getting rid of the mechanical brakes. On a long hill/mountain, what do you do when the battery is charged and the engine can't provide enough stopping power?

Michael

I had a similar dual-propulsion idea pop into my head the other day, great to see other people are thinking the same way!

I'm interested how it would be integrated into the driving experience. How about an analogue lever behind the steering wheel, similar form-factor to the semi-automatic gear change paddles you see on exotic sports cars? Around town you might have the ICE in neutral and drive the car on the paddle lever. Then when you reach the open road, fire up the ICE, select a gear and gently release the clutch while easing off the paddle. A bit of practice needed to get the hand-eye-leg coordination!

I thought about this once and it would seem extremly easy to do something like this.
use your regular gas engine throtle for the electric one by wiring through the ecu.

only problem i would see is finding a cost effective high powered electric engine.

the electricity can be taken from alternators driven by air force and a aolar panel ceiling.

100% for custom fabrication tho

Do you mean like this? Electrocharger / Retrofit PHEV Hybrid Conversion Kit :: Sigma Automotive
I've watched it for a while, and am still kinda hopeful it will actually make it into production.

Yeah the sigma page looks promising... despite some syntax errors

Geo Metro front drive, a Geo Tracker rear axle driven off the UJoint by an electric motor. They are about the same width. Electric for accel, bump start the ICE.