coldoath
NAXJA Forum User
- Location
- West Texas
Reasoning behind this statement?
Electric assist motor feasibility to improve MPG
- Thread starter casm
- Start date
Reasoning behind this statement?
bigalpha
Moderator
- Location
- Tucson, AZ
I doubt anything implemented will require any type of in-depth code.
- Location
- Rainy side of Washington
You'd be surprised...
That being said, I doubt casm would have problems writing code anyways. As I recall he's one of the resident software/computer wizards around here.
That being said, I doubt casm would have problems writing code anyways. As I recall he's one of the resident software/computer wizards around here.
Heh, I'm a long way removed from being a programmer anymore - I can whip up a shell script, beat a bit of C/Perl/PHP into doing what I want, and still kinda-sorta follow 6502 and 68K assembly - but so much of what I've been doing the past few years has been either infosec/network engineering or management that I'm seriously rusty in that department. Wouldn't mind an excuse to refresh those particular grey cells, though...
And he's so smart that he just closed the browser tab containing the preview reply to this thread that took an hour to write
I'll regurgitate it when I'm at home again later - grmph.
- Location
- Rainy side of Washington
if you use firefox, ctrl-shift-t may save your bacon there. reopens the last closed browser tab including all history and (in some cases) form entry data.
dasbulliwagen
NAXJA Forum User
- Location
- Asheboro, NC
I seriuosly cant beleive that this thread has gone on for as long as it has, with so many serious replies. What the OP is wanting to do is not doable on the budget he has, and with the way he wants it done, there is a lot of overlap of systems. I agree that the best way to do this would be a full diesel electric conversion running electric to power it all the time. Adding alternators, and controllers and putting in this and that between the engine and trans is all pure fantasy on any budget less than a million dollars in order to make it usable and reliable. Even a decent diesel electric setup is going to cost upwards or 10-20,000 dollars to do right. Im sure you think that you can do better and on budget, but a realist sees it the other way. Im sorry, but I just dont see it happening for you. If you ever do start a build, in my experience, you will never finish to a degree youre happy with, and will just be out all the money you spent on it, and out the vehicle itself too as it will be torn all to hell in the process. Youre having some good ideas, but if they were that good, they would have been done somewhere else by now. Hybrid gas electric engines and trans are seriously expensive to engineer. Im just trying to save you some heartache later on. This just isnt going to work.
Hokay, time to see if I can reply without killing the tab again. Onwards:
I'd say that's about 95% of the idea. The other 5% is a small but significant distinction: it only does this under certain circumstances. I realise that you get this, but wanted to make sure that it's included as part of the overall picture.
Understood, and I'm not making any pronouncements on efficiency either - all of this is theoretical, and I'm taking anything that we go over here (my ideas included) as being basically a 'what if...' bull session.
Anyway, I agree with what the numbers on that chart show, but they don't cover the one circumstance I'm most interested in: economy improvements with the gas engine decoupled from the drivetrain. Granted, that's a big unknown at this point, and once the mega-alternator is added into that equation, it may well cancel out the improvements I'd be hoping to see. But the point is taken.
That may end up being the most feasible approach, sure. The one thing I see with that equation, though, is that you'll still need something to drive that generator - which is essentially the role that the 4.0 would fulfill. Now, that's not to say that there may not be a better choice than the 4.0 for running the generator (there almost certainly is), but keeping to using as much of what we've already got is what I'm mainly aiming for.
Out of curiosity, what was your idea in this regard? I've seen a couple of EV conversions that do this in small cars where something like a 15hp diesel generator provides power to the EV drivetrain, but those are stull running batteries IIRC.
Actually, I'm in a lot of agreement with this approach, particularly from some of the reading I've been doing lately.
One thought that crossed my mind (totally impractical, but seems like it would have merit in an ideal world) would be to replace the torque converter with a dual-clutched electric motor. In normal running it could provide essentially the functionality of the torque converter, but decouple the input shaft from the 4.0 under assist conditions. The downside is that that would require the AW4 to stay in gear to provide motive power, which would entail losses through the transmission - thus coming back to the on-the-tailshaft idea.
As an aside, I've been nursing a theory for some time that the programming of the AW4 controller combined with the gear spacing and torque converter behaviour is a contributing factor to poor start-stop condition fuel economy. However, I'm not sure (given the latter two factors) that there's a lot of room for improvement there; replacement with a CVT may be a better approach than hacking the controller software. Complete speculation on my behalf, though.
You nailed it - ideally, this is how I wanted to control the coupling / decoupling of the DC motor.
That's the thing... The integration part in terms of control doesn't seem impossible; packaging is almost the bigger issue. That latter part is still theoretical, though, because I'm just not finding a DC motor that ticks all the right boxes, so there's nothing to get a physical dimensions baseline with - yet.
This was why I was considering the double-clutch idea - one clutch at each end of the DC motor, electrically-activated (similar to the ECTED locker, say). That may go some way towards alleviating or hopefully eliminating the situation you're outlining above.
I'm glad you mentioned this; it's something that's been in the back of my head but that I've been avoiding for one reason: aerodynamics.
My completely off-the-cuff, non-empirical observations suggest that 60mph is the point of diminishing returns on aerodynamic efficiency for an XJ. Makes sense; we're pushing a brick through the air, and it's a brick that was designed for a 55mph speed limit - it simply wasn't necessary for it to cut through the air at 70 or 80mph because people weren't commonly driving at those speeds in 1984, and decent EPA economy numbers could be returned at testing for a 55mph limit.
With that in mind, my opinion is that trying to use the assist motor at highway speeds would return only a very small (if any) improvement without also substantially improving aerodynamics. Granted, I could be entirely wrong about this, but it seems like a not-completely-unreasonable supposition given what I've seen thus far.
My driving is typically about 80% town, 20% highway, so the focus has been on improving start-stop driving economy.
True, but keep one thing in mind: all of this is notional. That's not to say you aren't necessarily correct, but rather to say that we're just kicking the idea around and seeing what comes of it. Nobody's turning ordering parts or turning wrenches yet
No offence taken, and it's certainly not read as bashing. Early on in the thread I asked for people to constructively poke holes in the idea, and that's definitely what it's here for.
Yep, I've run across this in a couple of things I've been looking at. The idea interests me, but I'm not sure how effective it would be in this situation. I really need to get a better understanding of it first before writing it off, though.
True, but most of the motors I've been looking at are in the 400A-600A range; this seems to be about where they produce comparable torque to a 4.0. You can get similar torque numbers from lower-amperage units, but those motors typically aren't intended for automotive applications. However, if there's something out there I've missed, I'd love to hear about it.
Yes, but Internet is SERIOUS BUSINESS, and SERIOUS THREAD calls for SERIOUS REPLIES
Again: everything being discussed here is notional. Not repeating the point to get on you specifically about it, but because it's a point that seems to be being missed as people (hopefully) read through the thread.
Okay, you're saying it won't work - and that's perfectly fine. But, in relation to the system I am proposing, please explain why it's a bad idea. I understand what you're getting at with the above, but it doesn't directly address the system being discussed.
(Note to Kastein: I found the 'submit' button this time The earlier issue was that I forgot to protect the tab I was editing in, and trying to resurrect it once closed didn't recover my responses.)
I'd say that's about 95% of the idea. The other 5% is a small but significant distinction: it only does this under certain circumstances. I realise that you get this, but wanted to make sure that it's included as part of the overall picture.
If we look at this dyno sheet: (ignore the red lines, its for a muffler comparison)
You will see that in order for a 4.0 to make 100hp to give full power to the EM, you need to be at around 3250 rpm. Count in the loss from the EV drivetrain, we are probably looking between 3500 and 3750 rpm.
Now that is if you want FULL EM power to the wheels, so lower rpms would create lower voltage therefore low power.
Just looking at these numbers it doesnt sound like you are going to be getting much a difference in mpg. Let me remind you that i included a lot of speculation in that post, so take that with a grain of salt.
Understood, and I'm not making any pronouncements on efficiency either - all of this is theoretical, and I'm taking anything that we go over here (my ideas included) as being basically a 'what if...' bull session.
Anyway, I agree with what the numbers on that chart show, but they don't cover the one circumstance I'm most interested in: economy improvements with the gas engine decoupled from the drivetrain. Granted, that's a big unknown at this point, and once the mega-alternator is added into that equation, it may well cancel out the improvements I'd be hoping to see. But the point is taken.
That may end up being the most feasible approach, sure. The one thing I see with that equation, though, is that you'll still need something to drive that generator - which is essentially the role that the 4.0 would fulfill. Now, that's not to say that there may not be a better choice than the 4.0 for running the generator (there almost certainly is), but keeping to using as much of what we've already got is what I'm mainly aiming for.
Out of curiosity, what was your idea in this regard? I've seen a couple of EV conversions that do this in small cars where something like a 15hp diesel generator provides power to the EV drivetrain, but those are stull running batteries IIRC.
Actually, I'm in a lot of agreement with this approach, particularly from some of the reading I've been doing lately.
One thought that crossed my mind (totally impractical, but seems like it would have merit in an ideal world) would be to replace the torque converter with a dual-clutched electric motor. In normal running it could provide essentially the functionality of the torque converter, but decouple the input shaft from the 4.0 under assist conditions. The downside is that that would require the AW4 to stay in gear to provide motive power, which would entail losses through the transmission - thus coming back to the on-the-tailshaft idea.
As an aside, I've been nursing a theory for some time that the programming of the AW4 controller combined with the gear spacing and torque converter behaviour is a contributing factor to poor start-stop condition fuel economy. However, I'm not sure (given the latter two factors) that there's a lot of room for improvement there; replacement with a CVT may be a better approach than hacking the controller software. Complete speculation on my behalf, though.
You nailed it - ideally, this is how I wanted to control the coupling / decoupling of the DC motor.
That's the thing... The integration part in terms of control doesn't seem impossible; packaging is almost the bigger issue. That latter part is still theoretical, though, because I'm just not finding a DC motor that ticks all the right boxes, so there's nothing to get a physical dimensions baseline with - yet.
This was why I was considering the double-clutch idea - one clutch at each end of the DC motor, electrically-activated (similar to the ECTED locker, say). That may go some way towards alleviating or hopefully eliminating the situation you're outlining above.
I'm glad you mentioned this; it's something that's been in the back of my head but that I've been avoiding for one reason: aerodynamics.
My completely off-the-cuff, non-empirical observations suggest that 60mph is the point of diminishing returns on aerodynamic efficiency for an XJ. Makes sense; we're pushing a brick through the air, and it's a brick that was designed for a 55mph speed limit - it simply wasn't necessary for it to cut through the air at 70 or 80mph because people weren't commonly driving at those speeds in 1984, and decent EPA economy numbers could be returned at testing for a 55mph limit.
With that in mind, my opinion is that trying to use the assist motor at highway speeds would return only a very small (if any) improvement without also substantially improving aerodynamics. Granted, I could be entirely wrong about this, but it seems like a not-completely-unreasonable supposition given what I've seen thus far.
My driving is typically about 80% town, 20% highway, so the focus has been on improving start-stop driving economy.
True, but keep one thing in mind: all of this is notional. That's not to say you aren't necessarily correct, but rather to say that we're just kicking the idea around and seeing what comes of it. Nobody's turning ordering parts or turning wrenches yet
No offence taken, and it's certainly not read as bashing. Early on in the thread I asked for people to constructively poke holes in the idea, and that's definitely what it's here for.
Yep, I've run across this in a couple of things I've been looking at. The idea interests me, but I'm not sure how effective it would be in this situation. I really need to get a better understanding of it first before writing it off, though.
True, but most of the motors I've been looking at are in the 400A-600A range; this seems to be about where they produce comparable torque to a 4.0. You can get similar torque numbers from lower-amperage units, but those motors typically aren't intended for automotive applications. However, if there's something out there I've missed, I'd love to hear about it.
Yes, but Internet is SERIOUS BUSINESS, and SERIOUS THREAD calls for SERIOUS REPLIES
Again: everything being discussed here is notional. Not repeating the point to get on you specifically about it, but because it's a point that seems to be being missed as people (hopefully) read through the thread.
Okay, you're saying it won't work - and that's perfectly fine. But, in relation to the system I am proposing, please explain why it's a bad idea. I understand what you're getting at with the above, but it doesn't directly address the system being discussed.
(Note to Kastein: I found the 'submit' button this time
The earlier issue was that I forgot to protect the tab I was editing in, and trying to resurrect it once closed didn't recover my responses.)
bigalpha
Moderator
- Location
- Tucson, AZ
My second thought is: is there a reason you are mainly looking at driveshaft/torque converter level?
I've got two ideas that may be crazy:
1. What if you mounted two smaller motors to turn the wheels?
2. What if you could mount a motor in/around the front diff to turn the axleshafts (if you had 2WD)?
I don't know squat about squat so I don't know how doable those ideas are.
I've got two ideas that may be crazy:
1. What if you mounted two smaller motors to turn the wheels?
2. What if you could mount a motor in/around the front diff to turn the axleshafts (if you had 2WD)?
I don't know squat about squat so I don't know how doable those ideas are.
Definitely. More:
It was actually wheel hub motors that got me onto the splice-into-the-drivetrain idea. They appear to have a lot of potential, but from what I've been able to dig up on them they make more sense to implement in a clean-sheet design where they can be packaged appropriately. The real issues include (but are not anywhere near limited to) modifying axles and suspension in an existing design to accomodate them: they have very definite physical space requirements, and add significant unsprung weight.
That's not to say they aren't a good approach; my gut feeling is that they may be better overall provided that the issues above can be worked out. It's just not clear to me how that could be done on a practical level in the context of an XJ.
Or 2WD with a transfer case fed (through the case's front output) to an electric motor up front. Either one sounds workable, but then you've only got 2WD.
Just to explain the idea of grafting onto the back of the transmission (or thereabouts) a little further, it's the one common point in the exposed drivetrain layout between both 2WD and 4WD models, so in theory an assist motor placed at that point should be workable regardless of the drivetrain layout or transfer case mode.
Me neither, but I'm definitely enjoying kicking the ideas around
Last edited:
- Location
- Rainy side of Washington
hmmm.... this gives me an idea. Given how many people build a 231/300 doubler, what are your thoughts of taking a 231, clocking it over to the passenger side, building a custom rear housing half that a 300 bolts to, and then lock it into "4wd"? The drag from the DC motor would be minimal with the field coil disabled (or the power turned off, if a PM motor) and so you could then just use the transmission shift lever to switch from gas to electric by putting the transmission in neutral. Driving the generator would still be a problem though.Definitely. More:
It was actually wheel hub motors that got me onto the splice-into-the-drivetrain idea. They appear to have a lot of potential, but from what I've been able to dig up on them they make more sense to implement in a clean-sheet design where they can be packaged appropriately. The real issues include (but are not anywhere near limited to) modifying axles and suspension in an existing design to accomodate them: they have very definite physical space requirements, and add significant unsprung weight.
That's not to say they aren't a good approach; my gut feeling is that they may be better overall provided that the issues above can be worked out. It's just not clear to me how that could be done on a practical level in the context of an XJ.
Or 2WD with a transfer case fed (through the case's front output) to an electric motor up front. Either one sounds workable, but then you've only got 2WD.
Just to explain the idea of grafting onto the back of the transmission (or thereabouts) a little further, it's the one common point in the exposed drivetrain layout between both 2WD and 4WD models, so in theory an assist motor placed at that point should be workable regardless of the drivetrain layout or transfer case mode.
Me neither, but I'm definitely enjoying kicking the ideas around
Hm... Hadn't considered that specifically, but I can't see why it wouldn't work. It's more or less the same basic approach I'd proposed initially, but moving the DC/PM motor to a different spot in the drivetrain. Gonna chew on that for a bit, but I can't really see a huge downside on the face of it.
Yeah, that one's still a big 'how's that gonna work' item.
jimgrms
NAXJA Forum User
- Location
- Oceanside Ca the beach
If it was finacially feasable it would have been done already,, what ever detroit is its not dumb
larsen
NAXJA Forum User
- Location
- Washington
Ditch the transfer case. Use a 2wd trans to the rear axle and a dc motor to the front axle. Run a rear axle abs signal generator to sync the electric motor controller speed to to rear axle speed for awd. The front axle motor can serve as a generator when not being used as a drive motor. Use the alternator to trickle charge.
Point taken, but wheel hub motors would also be workable for this while allowing the drivetrain layout to remain substantially the same. But then we're back to wheel hub motors and everything that entails. Not saying it's not necessarily workable (it sounds like it would be), but in terms of overall effort compared to wheel hub motors would probably end up being about the same only with a different set of reengineering challenges.
larsen
NAXJA Forum User
- Location
- Washington
I'm gonna keep my eyes open for free parts with electric-drive conversion potential and work on proof of concept. I already have the 'victim' vehicle :explosion in my possession. Let's see if I can do to Lexus what Subaru did to VW.
Cool. Please keep us posted.
I'm guessing this means that the victim is a Lexus, but I don't quite get the "what Subaru did to VW" part...
larsen
NAXJA Forum User
- Location
- Washington
The victim is a Cherokee .. as for Subaru: "Talent borrows, genius steals."
The alternator idea is wholly unworkable.
You're taking in chemical energy in the form of gasoline, converting it to mechanical energy with the engine, converting it to electrical energy with the alternator, then back to mechanical with the electric motor. Each conversion causes a loss of energy and efficiency.
A battery-less hybrid like you describe wastes more energy than a conventional setup. To add efficiency you need to get the energy from another source - either off the grid stored in a battery or reclaimed with regenerative braking. As it is, this is nothing more than a free-lunch attempt at beating the laws of physics ala HHO.
You're taking in chemical energy in the form of gasoline, converting it to mechanical energy with the engine, converting it to electrical energy with the alternator, then back to mechanical with the electric motor. Each conversion causes a loss of energy and efficiency.
A battery-less hybrid like you describe wastes more energy than a conventional setup. To add efficiency you need to get the energy from another source - either off the grid stored in a battery or reclaimed with regenerative braking. As it is, this is nothing more than a free-lunch attempt at beating the laws of physics ala HHO.
Ah, OK. Gotcha now.
FWIW, Subaru based the first version of their flat-four on a Borgward design, not VW - and I believe they licensed the rights to it. Definitely a smart idea on their behalf
Okay. Now lets see if that supposition holds water or not. I understand everything you're saying here, but in the circumstances this is intended to operate in it may produce a benefit. How much of a benefit (if any) remains to be seen.
Uh, no. If you've read this as an attempt at generating 'free' energy, I'd suggest that you've misunderstood the basic idea being proposed.
Is anyone here serious? These ideas are way out there: either ignoring physics or ignoring any notion of payback. Here's how I would approach it from a more earth-based perspective.
1) Research hypermiling techniques. Try them out, see what works. Driving habits do make a difference, and they don't require a mechanical investment. An mpg gage helps.
2) Take the techniques that work and see if a system can augment them. One technique is turning the engine off when you stop to avoid wasting gas idling. I don't do that much, only sometimes at the bank drive through, but I'm always amazed/horrified how quickly my trip-mpg falls when stopped, even after a 30 min. highway drive. There are hybrid-lite vehicles that basically have an oversized starter so that when you stop the engine doesn't idle, and when you press the gas it starts and goes with the transmission in gear. One may be able to do this for not too much cash and weight (dual batts should power it, and be good for running the winch!).
Another technique that works is pulse and glide. Some folks with manual transmissions even install a kill switch button to turn off the engine when gliding, and roll start and the end of the glide. If you already had the "hybrid-lite" setup the engine wouldn't idle anyway and you could just press the gas to start and avoid wear on the clutch. For automatics (like mine) from the factory the computer turns off the injectors when coasting and the engine is over 1500 rpm or so. If you could change it to let the engine die you could save even more gas. Need to consider the breaks and steering.
This is what I would look at. It could significantly increase in-town, stop and go, and country highway mileage. Especially where it's hilly. And I'd try to do it for less than $1,000.
1) Research hypermiling techniques. Try them out, see what works. Driving habits do make a difference, and they don't require a mechanical investment. An mpg gage helps.
2) Take the techniques that work and see if a system can augment them. One technique is turning the engine off when you stop to avoid wasting gas idling. I don't do that much, only sometimes at the bank drive through, but I'm always amazed/horrified how quickly my trip-mpg falls when stopped, even after a 30 min. highway drive. There are hybrid-lite vehicles that basically have an oversized starter so that when you stop the engine doesn't idle, and when you press the gas it starts and goes with the transmission in gear. One may be able to do this for not too much cash and weight (dual batts should power it, and be good for running the winch!).
Another technique that works is pulse and glide. Some folks with manual transmissions even install a kill switch button to turn off the engine when gliding, and roll start and the end of the glide. If you already had the "hybrid-lite" setup the engine wouldn't idle anyway and you could just press the gas to start and avoid wear on the clutch. For automatics (like mine) from the factory the computer turns off the injectors when coasting and the engine is over 1500 rpm or so. If you could change it to let the engine die you could save even more gas. Need to consider the breaks and steering.
This is what I would look at. It could significantly increase in-town, stop and go, and country highway mileage. Especially where it's hilly. And I'd try to do it for less than $1,000.
