A Real Hybrid XJ

I put some though into this idea a couple years ago for a full-sized SUV. It came to me after working a construction job for a while and then going to work in the turf grass industry. I know a strange way to begin a hybrid idea, but we used a generator that was diesel powered and put out enough power to run an electric tower crane and all of our power tools, lights ect. It averaged out to use about 4 gallons per hour which is not bad for a diesel motor 1/2 the size of an XJ. I am not sure on the output but it was supposed to be able to power 4 residential blocks. It was large, but you would never need something that powerful. The second half of the story came about at the first golf course I worked at. We had to replace the water pumps that supplied the course with all of its irrigation. They were submersible pumps powered by 1000 hp electric motors. When I saw the size of the electric motor, I started thinking about the applications in vehicles. You could in effect turn your vehicle into a generator that powered its own electric motor. This was in late '99 early '00, before hybrid tech was very popular in America. Now days the idea is old but back then I thought I was on to something... I got married and had kids so all of my 'thinking' was put on hold. After reading this post, I have gained interest again. Maybe not for an XJ, but something larger like a suburban or expedition.

I was wondering why you would need batteries? Other than one to start the diesel engine. Couldn’t you use a series of capacitors? Once the engine is started, it would adjust RPM based on the needs of the electric engine or the state of the capacitors. I am by no means an electrical person, so if that way off some one slap some sense into me...

:twak:
 
The advantage of using batteries is you can charge them at home from the electric grid. You only need the generator if you use up the batteries. For short trips, you could plug it in and not use any diesel.
I remember a Popular Mechanics magazine project in the early 80's that they built with an electric motor and a small gas generator. It was a styrofoam bodied home built, but it got reaaly good mileage. IIRC they used fork lift parts for the electric power.
If you can make it work, it should be a really cool project.
 
FoMoCo said:
also I'd strongly recomend some sort of trans, even if its a 2 speed, since you say 90% of your driving is highway. you probably won't get your best efficiency running right at the max 100% duty cycle RPM, and motor life will likely be shortened.
Good point - I had planned to check with the manufacturer about that, however I have to admit I am hoping the best way to run it involves no transmission. The basic specs I've seen on this motor shows a max RPM of 10,000 - at what duty cycle I have no idea - that would equate to about 200MPH connected directly to the transfer case. :roflmao:

There will have to be at least two limiters built into the control system; one to prevent over-torque of the drive line components off the line, and a governor on the RPM.
 
This is the most interesting thread i have ever read. WoW. What an Idea. I see how this could be a great thing for the future. Dont let this idea get away. I never want to have to park my XJ because i cant afford gas or if it. Good luck and thanks for the good read.
 
chuckm65 said:
Well, if I triple my mileage (actually the correct term should be "fuel efficiency", since some of my cost will be for diesel and some will be for electricity from the grid), it would cut my cost down to a third, say $350 per month, or a savings of $600-700 each month! That adds up quick.

My reasons for wanting to do it listed by importance to me:

1) this sounds like a fun project
2) the long term pay-off in reducing my fuel costs
3) politics - while I am not Green by any stretch, I hate having no choice other than to pay whatever they demand at the pump
4) the long term savings in learing how to do this stuff myself
5) I've always been intrigued by the idea of cheaper energy - It's just now that I am coming to a point in my life where I can start playing around. I'm also looking into solar panels and/or windmill generator for my home

But I still need to figure out how many horsies it takes to make this brick go 70MPH
hasta

1) I totally agree and support the project for this reason: go for it!

2) Maybe, maybe not. It can be done, but don't count on it and don't do it simply for this reason, and least without a lot of through investigation. And I can tell you right now that you won't save much on the highway, but you have a lot of potential at slow speeds: especially off road mileage.

3) Agreed. And with a diesel you upen up biofuels and straight vegitable oil, which is where you have much more potential to cut fuel costs.
4 and 5) yup yup


For regular driving there's no way that a simple powerplant/hybrid swap will tripple mileage. The efficiency simply aren't there to be had. 1st, you can almost forget about gains during highway driving. The slight savings in gas will be cancled out by the cost of batteries, which do wear out. Here are the main opportunities that I know of:

Short trips: this is where EVs accell and make the most sence.
Slow speeds, stop and go, off road: This is where gas engines are very ineffecient and hybrids can do better.
Different fuel source: burning waste oil that you get for free or next to it is you biggest money saving opportunity.

Cool project, just make sure you do it for the right reasons.
 
chuckm65 said:
Now, since the diesel would only be used to drive the generator, it will run at a constant speed. It will only kick on when the batteries reach a certain level of discharge AND will be configured to run flat out at a constant throttle - the most efficient way to run any internal combustion engine. The electricity produced will be consumed by a combination of running the electric drive motor and recharging the batteries.

The efficiency ratios for electrical generation are in the 90+%, as are the conversion back to mechanical power in the drive motor.

Since a diesel, pound for pound, pulls a lot more power out of it's fuel than a gasoline engine and since it will be run in such a way to maximize its efficiency, combined with the low cost of the charge-up I get from home at night, I truly believe that I can get a cost per mile as low the equivalent of 60+ MPG

There are other groups that could help with the details a lot better than naxja. Check out yahoo groups for EVs and hybrids.

90% mechanical to electrical and 90% back works out to 81% total: a good sized loss that will eat up a lot of the gains made from running a constant load. Also, the added weight of the system will cut in to the overall effeciency.

Most home EV conversions keep the transmission as the motors used are more effecient with the lighter starting loads. But if you do get a motor that can handle the starting loads for regular street use remember that you sill have low-range in the transfer case for more torque off road.

And I wouldn't worry about spinning an electric motor at high speeds, at least from a wear perspective. It's all rotational, not recipercating (sp?) like with internal combustion. The problem is that the power will drop off at the very top.
 
srimes said:
There are other groups that could help with the details a lot better than naxja. Check out yahoo groups for EVs and hybrids.
Yeah, the main reason I started this here is that I MUST figure out how much horsepower is required to make an XJ roll through the wind at 70MPH. I guess I figured with all the XJ officianados on this forum that someone would know of a source for this info... or give me a good way to figure it out.

Maybe i can find some info regarding wind resistance coefficients for the XJ body and work it out that way - I think the rolling resistance / friction is only about 10% of your energy output at those speeds.

srimes said:
90% mechanical to electrical and 90% back works out to 81% total: a good sized loss that will eat up a lot of the gains made from running a constant load. Also, the added weight of the system will cut in to the overall effeciency.
Not sure how much extra weight - losing the 4.0 and the transmission lightens it up by about 650 lbs. The electric motor weighs in at 90 kilos (about 200 lbs). Add in a 3 cylinder (hopefully that small) diesel with generator core and I would imagine it's something between a 150 pound savings or a break-even.

How much the necessary batteries will weigh is a function of technological improvements over the next year or so and how many PBJ's I'm willing to eat in order to pay for better / lighter cells.

During development I can see myself just using a bunch of AGM's on where the back seat and cargo area is - probably have to install some air-springs to help with the weight. Can anyone recommend a good rear axle upgrade? I have the 8.25 on it right now.

srimes said:
Most home EV conversions keep the transmission as the motors used are more effecient with the lighter starting loads. But if you do get a motor that can handle the starting loads for regular street use remember that you sill have low-range in the transfer case for more torque off road.
I think they use a transmission so as to reduce the size/cost of the drive motor. They usually get one with max power just enough to drive it at 55-60 mph and no more. So they need the mechanical advantage of gearing down at low speeds.

If my current guestimates are even close, the motor I have selected will be capable of driving the vehicle in excess of 100 mph, although my electrical system would not sustain that for any appreciable time, which is just as well since it would exceed the drive motor's rated RPM and power limits for 100% duty cycle - but should I find a tractor-trailer barrelling down on my arse I might be able to get out of his way. Also, this will permit me to move off the line which is something I need when off the highway.

and I was counting on the reduction of the transfer case for off-road. BTW, what is the reduction ratio from the input shaft when in Low?
 
2.72 to 1 low range reduction at the output shaft.....

Grow a corn field and make your own fuel and start a bar and serve Golden Grain 190 to pay for the operation!!.....:cheers:
 
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chuckm65 said:
Yeah, the main reason I started this here is that I MUST figure out how much horsepower is required to make an XJ roll through the wind at 70MPH. I guess I figured with all the XJ officianados on this forum that someone would know of a source for this info... or give me a good way to figure it out....
Ecomike has an xj with a 64hp diesel according to his sig :)
 
chuckm65 said:
Ok, I found a Brake Horsepower curve for a 4.0 liter.

http://www.wjjeeps.com/misc/curve_40.jpg

It shows about 90 HP at 2,300 RPM, but I assume that is it's maximum horsepower at that speed (i.e. with the throttle wide open).

So does it make sense that at 70 MPH with LOTS of pedal left that I am using something (hopefully considerably) less than 90 HP?
internal combustion engines (ie, not electric) operate at highest efficiency at WOT, and efficiency is what you're going for... if you're running at 2,300 rpm and lots of pedal left, you could probably run lower rpm at WOT... thus producing less overall power. the one kink in that is i have no idea how to calculate/measure that. i can say that at 70 mph, most of the resistance will be aerodynamic and will increase with respect to speed squared, but will be multiplied by some constant. so whatever the drag coefficient of a very large brick moving at 70mph is... there you go :lecture:. i wouldn't necessarily neglect the other power consumed by internal drag(in the engine, rolling resistance, etc), but it's probably less than 20% of the overall drag. so you could do some sweet number fudging and estimating to come out with a potentially semi accurate number...

i too say go for it. i'm on a supermileage vehicle team at school (UMass Amherst for mechanical engineering) and the goal of the competition is high gas mileage. last year we got 1125 mpg. granted, that incorporates a lot of driving strategy. we run it up to speed then kill the engine and coast till it slows down then do it all over again.

anyway, good luck and definitely post on the results!
 
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asp387 said:
internal combustion engines (ie, not electric) operate at highest efficiency at WOT, and efficiency is what you're going for... if you're running at 2,300 rpm and lots of pedal left, you could probably run lower rpm at WOT... thus producing less overall power. the one kink in that is i have no idea how to calculate/measure that. i can say that at 70 mph, most of the resistance will be aerodynamic and will increase with respect to speed squared, but will be multiplied by some constant. so whatever the drag coefficient of a very large brick moving at 70mph is... there you go :lecture:. i wouldn't necessarily neglect the other power consumed by internal drag(in the engine, rolling resistance, etc), but it's probably less than 20% of the overall drag. so you could do some sweet number fudging and estimating to come out with a potentially semi accurate number...

i too say go for it. i'm on a supermileage vehicle team at school (UMass Amherst for mechanical engineering) and the goal of the competition is high gas mileage. last year we got 1125 mpg. granted, that incorporates a lot of driving strategy. we run it up to speed then kill the engine and coast till it slows down then do it all over again.

anyway, good luck and definitely post on the results!
Well, I'm starting to get the idea that the HP required is MUCH less than 90 to go 70 MPH. I found a page for a guy who did a straight electric conversion of an '88 XJ. He used a 19/84 rated/max HP motor. Said the top continuous speed he had attained was 65 MPH. I'm trying to get in touch wit him now to see what his motor's amp draw was at that speed.

BTW, I've seen several technical specs for the 97-01 XJ drag coefficient at 0.52. Although this by itself is meaningless. I think for this to be usefull we also have to know the cross-section area of the vehicle's front, top to bottom (I would assume it includes the tires as well?) - time to get my tape measure out.

Thanks for all the encouragement, and I will continue to post to this thread as I learn more.
 
Half of the word "American" Is I CAN! I will be watching this thread with great intrest. I do have a speculation. Weight of the engine/drivetrain versus weight of the "Hybrid" Components. (Including batteries/capacitors). And distribution thereof.
 
I say go for it Chuck. Once you get it done, I'm sure alot people will be asking how you did it.

I thought about putting a Natural Gas Bi-fuel engine in my '55 Chevy, but I'm concerned about the lack of power. The Chevy Cavalier NGV sells for about $7,000 used. But, I think my '55 will spit out the 4 banger in a heart beat. :D

The more people try different solutions, the more options we'll have in the future.

E
 
chuckm65 said:
Yeah, the main reason I started this here is that I MUST figure out how much horsepower is required to make an XJ roll through the wind at 70MPH. I guess I figured with all the XJ officianados on this forum that someone would know of a source for this info... or give me a good way to figure it out.


The MPG guys do something called a "coast down test," which should give you a good idea about the resistance. I haven't worked with it so I don't know how specific it will be at a given speed.

Another test which could be the most accurate, but harder to perform, would be some version of a tow test, where a seperate vehicle provides the motive force for the jeep, say by pulling, and that load is measured with a spring scale. You can then measure the lb-thrust needed at any speed and grade and calculate the needed horspower. You'll just need a rope long enough to not throw off the drag too much, or do an offset pull, or a push, or something. And it probably would not be legal on public roads. I'd try the coast-down test first.



chuckm65 said:
Not sure how much extra weight - losing the 4.0 and the transmission lightens it up by about 650 lbs. The electric motor weighs in at 90 kilos (about 200 lbs). Add in a 3 cylinder (hopefully that small) diesel with generator core and I would imagine it's something between a 150 pound savings or a break-even.

How much the necessary batteries will weigh is a function of technological improvements over the next year or so and how many PBJ's I'm willing to eat in order to pay for better / lighter cells.

The 4.0 is a heavy pig, but it think you are being very optimistic. A diesel genset that puts out 30 hp is not going to be light. Most probably weigh more than the 4.0 and transmission, and new will cost more than the jeep is currently worth. To do it cheaply will require a great deal or creating your own with a used engine.

Why did you decide on a series-hybrid system? Do you need to be able to drive at highway speeds indefinetly? If so you may be better served by a parallel system, like what is used in production hybrids today. If you don't need full-time highway capibilities then a series system with a smaller genset may be a better idea. If you size it for continuous opperation in the 30 to 45 mph range you can use a much smaller engine, which can change while you're stopped.

If you do a lot of highway driving you may just want to swap in a diesel and check out biofuels.
 
srimes said:
The MPG guys do something called a "coast down test," which should give you a good idea about the resistance. I haven't worked with it so I don't know how specific it will be at a given speed.

Another test which could be the most accurate, but harder to perform, would be some version of a tow test, where a seperate vehicle provides the motive force for the jeep, say by pulling, and that load is measured with a spring scale. You can then measure the lb-thrust needed at any speed and grade and calculate the needed horspower. You'll just need a rope long enough to not throw off the drag too much, or do an offset pull, or a push, or something. And it probably would not be legal on public roads.
I can see that working - given the vehicles mass and some soft of half-way reliable estimate of rolling resistance (which according to what I've read changes very little as speed increases), take it up to speed and then shift into neutral and plot the change in speed over time.

For the rolling resistance, just get on a flat road and tow it up to a steady 5MPH where the wind resistance is minimal and note the strain on a force-meter/tension gauge of some kind. This could work.

Now that I think about it, I guess I could even do 10MPH and 20MPH towing tests - the change in necessary force to pull the vehicle would be almost 100% due to increased wind resistance. That would alow me to fairly accurately calculate the drag coefficient (CxA or CdA). I think I could then use that with some formulas I found on Wikipedia to verify or augment the coast-down data/results.

You are right about the legalities - but at 5-20MPH I there are plenty of long, flat (it's Florida) straight residential roads around here that see no traffic at 6:00 or 7:00 am on a Sunday morning and the cops don't care what you do off the main roads

srimes said:
The 4.0 is a heavy pig, but it think you are being very optimistic. A diesel genset that puts out 30 hp is not going to be light. Most probably weigh more than the 4.0 and transmission, and new will cost more than the jeep is currently worth. To do it cheaply will require a great deal or creating your own with a used engine.
Optomistic - perhaps. maybe not - just depends on how much power it takes. And it wouldn't be fun if I just buy all the parts right from the factory. I plan to play around a good bit. Ideally I could find a used 3 cylinder turbo charged diesel that I can use with bio and/or flex mixtures

srimes said:
Why did you decide on a series-hybrid system?
Drive-line simplicity

srimes said:
Do you need to be able to drive at highway speeds indefinetly? If so you may be better served by a parallel system, like what is used in production hybrids today. If you don't need full-time highway capibilities then a series system with a smaller genset may be a better idea. If you size it for continuous opperation in the 30 to 45 mph range you can use a much smaller engine, which can change while you're stopped.
When I hit the highway I may have to go as far as 100 miles before getting off into stop & go traffic. I'm going to size the diesel/generator set such that even at highway speeds, there will be a little juice left over after powering the motor to do a little charging of the batteries. I will build/program the controller such that the motor turns on at the predetermined level of battery discharge, or if it senses the batteries cannot put out the power I need given my throttle position. When the diesel does kick in, it runs full bore at it's most efficient speed until the batteries reach a certain level of charge, and/or my foot loses some lead.

On my return trip, as I near home, I will manually turn down the charging thresholds - there's no sense in getting home with fully charged battery sets.

BTW, from the research I've done, I intend to put a bank of supercapacitors between the motor and its power supply. They act as an "accumulator" (for those of you familiar with hydraulic systems), smoothing out voltage and amerage fluctations from the batteries or generator, and acting as a short-term reserve of power to allow for time necessary to spin up the diesel/generator set.

srimes said:
If you do a lot of highway driving you may just want to swap in a diesel and check out biofuels.
I think a smaller diesel that is run only at a full-bore constant throttle/rpm will end up being SIGNIFICANTLY more efficient than any I.C.E. running any kind of fuel when mechanically connected to the driveline - but we'll find out one way or the other.
:cheers:
 
hollyxj said:
Here is an xj that had a electric motor swaped in http://www.driveev.com/jeepev/convpgs/motorclutch.php
yeah, he's the guy I sent email to hopefully find out what kind of amp-draw his electric motor saw at 65MPH.

His XJ is ALL electric with a reported range of about 35 miles. Despite the fact that he started this project 4 years ago, lead-acid / AGM battery energy densities haven't improved a lick since. He has 1,260 pounds of lead-acid batteries and was able to get 35 miles on a full charge.

I was hoping to keep my battery weight at or below the 1,200 pound mark, but I also want to get at least 45-60 miles on a single charge before the diesel-generator set has to kick in. I'm hoping the motor effficiencies have improved a little since then.

I'm also hoping that 70MPH can be had for around 30-40HP, altough I bet it's more like 40-50HP (friggin brick!!).

Maybe I should scrap the whole hybrid idea and just use some fiberglass to round the thing off a bit in the front - might get me from 19MPG to 30. LOL
 
chuckm65 said:
Maybe I should scrap the whole hybrid idea and just use some fiberglass to round the thing off a bit in the front - might get me from 19MPG to 30. LOL

or you could just swap the front end from a 2500 :looney:
 
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