A Real Hybrid XJ

[chuckm65]

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.

Well, I checked around with a fiew people I know locally and can't find anyone with a hanging scale I can borrow rated for more than 50 LBs. So I just ordered a 440 LB digital hanging scale. I suppose it'll come in handy for weighing some of the components I acquire along the way, as well.

Should be here by Thursday of next week, so I can get my sons to help me with the towing test next weekend - should be fun.

Anyone know of a good place to look online for small used 3-cylinder diesel engines in the 30-50 HP range?

All advice and constructive criticism is appreciated

 

[mramr1974]

I think jeep hybrid is a great idea if done alot of reserch for like vechiles but it you dont know already the cost will be up there, unless you have a special source for your eletric parts and alot of trial and error but defintly possible. just so you know there is a car coming out in 09 or 10 that runs on compressed air/fuel hybrid that will get about 100mpg and will cost about 17000 i forget the link but if you google aircar youll find a link for the us version current bring made in india but no airbags so that version wont be here gotta waiti ts preaty cool. good luck with your jeep

 

[srimes]

Well, I checked around with a fiew people I know locally and can't find anyone with a hanging scale I can borrow rated for more than 50 LBs. So I just ordered a 440 LB digital hanging scale. I suppose it'll come in handy for weighing some of the components I acquire along the way, as well.

Should be here by Thursday of next week, so I can get my sons to help me with the towing test next weekend - should be fun.

Anyone know of a good place to look online for small used 3-cylinder diesel engines in the 30-50 HP range?

All advice and constructive criticism is appreciated

Check out the marine engines used for sailboats, and compact diesel tractors too.

 

[chuckm65]

I think jeep hybrid is a great idea if done alot of reserch for like vechiles but it you dont know already the cost will be up there, unless you have a special source for your eletric parts and alot of trial and error but defintly possible. just so you know there is a car coming out in 09 or 10 that runs on compressed air/fuel hybrid that will get about 100mpg and will cost about 17000 i forget the link but if you google aircar youll find a link for the us version current bring made in india but no airbags so that version wont be here gotta waiti ts preaty cool. good luck with your jeep

I read about the air engine tech a year ago, or so. I'm not real impressed - with thermal losses at both compression and expansion (when you use it to make your car go) I don't see how it could be even close to the efficiency of an electric motor, because you would use an electric motor (could use an I.C.E but that would be even less efficient) to compress the air, then give up energy to heat loss produced during compression, then give up mechanical energy as the air cools off when it's used in the engine.

I don't know if there is enough friction in the air-engine that you could capture that heat and setup a regenerative cross-flow heat exchanger to reheat the air just before going into the engine, but my gut says it'd be so complex..... not sure if it's affordable

At a minimum you have range and infrastructure issues just like Hydrogen - But who knows?

Yeah, I know this project is going to be pricey - I'm going to try and minimize the tag by taking my time and planning everything. Right now I'm looking for some 3D CAD software so I can play with the layout of components - see what I have room for, etc. $1.00 of research/planning prevents $1,000 of "Oh Sh**!!!!" !

 

[Turfzilla]

So, where did you come up with the extra $1000 / month on fuel figure?? Even at $4/gal, thats an additional 250 gal of fuel/month. At 50000 miles each year = 4166 miles each month. So, you are using 230 gals/month (18mpg)

IF, your gas cost increased, oh I do not know, from 3.25 to $4/gal that would only be like $175 increase in fuel cost each month. Assuming you are driving the jeep that many miles now. Other wise your curent transportation would be getting at 38 mpg vs. the 18mpg of the jeep.

You have to look at your ROI on these "plans" stated above. Lets say it only cost $5000 for your changes. It will not pay for itself for about 120,000 miles.

I am not trying to shoot you down, but that extra $1000 you stated is WAY off IMHO. Maybe I am missing something here.

 

[twoksl2]

However, the mileage is not so great. I average a combined mileage of about 18-19 miles per gallon.

With gas going to $4.00 per gallon, I'll be spending about $1,000 per month just to fill this thing up.

its not an extra 1000 per month... he spends about 1k/mo just on gas. thats only about 150mi per day (assuming 30 day month, 18 mpg and 4.00/g gas)

 

[srimes]

I read about the air engine tech a year ago, or so. I'm not real impressed - with thermal losses at both compression and expansion (when you use it to make your car go) I don't see how it could be even close to the efficiency of an electric motor, because you would use an electric motor (could use an I.C.E but that would be even less efficient) to compress the air, then give up energy to heat loss produced during compression, then give up mechanical energy as the air cools off when it's used in the engine.

I don't know if there is enough friction in the air-engine that you could capture that heat and setup a regenerative cross-flow heat exchanger to reheat the air just before going into the engine, but my gut says it'd be so complex..... not sure if it's affordable

At a minimum you have range and infrastructure issues just like Hydrogen - But who knows?

I like the idea of compressed air as power storage myself. The energy storage density can beat chemical batteries, and don't depleat and wear out the same. It is used large-scale with power plants that pump air into sealed coal mines, and systems are being developed, I think soon to be implemented, for garbage trucks (hybrid), which are run basically only stop and go. Chemical batteries are not very good for regeneration as they cannot be changed quickly enough, but that isn't a problem for compressed air. Ford even build a hybrid SUV with hydraulic drive and compressed air accumulators to capture braking energy.

Compressed air, hydrogen, and chemical battery electric cars are basically the same proposal. They are all electric cars, just with different storage systems. The power is still generated at the power plant.

Compressed air would be great if you live where it's hot, as the exhaust will be cool!

 

[drifter]

My guess to your initial question is 97 HP. I know that is higher than you wanted to hear, but that is about what a stock 4.0L puts out at 2250 RPM.

I used the torque curve at this website http://www.ajeepthing.com/stroker-motor.html and HP=torque*RPM/5232 to determine that value.

Keep in mind losses throughout the normal drive train are generally estimated at about 50%.

Side-bar this sounds like a very complex and challenging project. I hope it goes well for you.

 

[srimes]

My guess to your initial question is 97 HP. I know that is higher than you wanted to hear, but that is about what a stock 4.0L puts out at 2250 RPM.

I used the torque curve at this website http://www.ajeepthing.com/stroker-motor.html and HP=torque*RPM/5232 to determine that value.

Keep in mind losses throughout the normal drive train are generally estimated at about 50%.

Side-bar this sounds like a very complex and challenging project. I hope it goes well for you.

Um, no.

Torque curves are given a full throttle. I'd guess the power required at 70mph is about 30.

And drive train losses of 50%? For what kind of drivetrain? In top gear with the TC locked up it's probably not much more than 10%. For a manual in 4th and 5th it's probably less than 5%

 

[rocketmanzj]

Powertrain losses from what I've been exposed to, just going off the differences in HP numbers from dynos can easily be 25-30+%. I'm more used to high HP, low drag cars, so switching to a brick with a large amount of powertrain loss is kind of shocking. I wouldn't think that 40% would be unheard of. 50% might be a little high though.

As far as the power needed goes, I know a thing or two about overcoming drag from air. Graduating from the Air Force Academy and then going through pilot training, taking Aero Engineering classes at both, it's kind of tricky. I'd be willing to help with some numbers, but I'm way to bogged down with flying right now to do much more than fly.

If you can find out the frontal area of the Jeep and if you could possibly find a drag coefficient then the numbers are pretty easy to compute and the formulas are pretty easy to get a hold of. Just some simple math. (If you need help with the math, I can do that pretty easily.)

I'm really sorry I can't help with this right now, I'd love to be able to help more, I just can't afford the time. If you want something else to think about though, the 2.5 pushes the cherokee around with less power than the 4.0, so you know you at least won't need as much power as the 4.0.

 

[oilyjeep76]

I can't help you on the electric side of things, but for more info on diesels swaps, check out 4btswaps.com and dieseltruckresource.com There is another diesel swap site I used to frequent, but can't remember what it is now. 4bt site deals with the cummins 4bt ( baby sister to the 5.9 cummins found in dodges. DTR is all dodge diesel info/forum

 

[xj2win]

You guys postulating about the required horsepower to maintain 70 mph are neglecting wind speed/air resistance. Also, you're going to need power to be able to accelerate, that wouldn't be very exciting if it took you a half hour to get up to 70. As was said before, hybrids get good mileage in the city due to the stop and go, a 200 mile trip on the highway the fuel motor will be running the whole time. Even with a diesel, I would be very surprised to see an XJ attain anything over 25 mpg or so. It doesn't have good enough aerodynamics and weighs too much to try and juice prius mileage out of it.

 

[n1ywb]

I've built a couple of hybrids with my college solar car club. My buddies and I have kicked around some ideas for building hybrids on a 4x4 drive train. Most of them involve either connecting the electric motor directly to the front diff and keeping it 4x4, or connecting the electric motor to the front drive shaft output on the transfer case, making the truck RWD. It would be mechanically simple. The biggest problem would be that with the stock motor and gas tank still in there, there wouldn't be much room for batteries. Maybe you could go with a smaller tank.

I doubt if it would be an economical project, but it would be cool.

Sorry to resurrect such an old thread...

 

[LVJimmy]

drag coefficient

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.

'91 Cherokee
Cd=0.45 frontal, area=2.4M^2
From website Mayfco.com

 

[redriverhugh]

I know its slightly off topic but there a french formula one designer who devised a air driven motor using compressed air to drive the wheels.

 

[n1ywb]

Sure, any gas under pressure can drive pistons, see steam. How are you going to store enough compressed air to go anywhere? Even if you liquefy it, you'd get a hell of a lot more energy density from a combustible liquid gas, like H^2 or LPG.

There are a million wacky ideas for engines. Very few of them really make sense. There's a reason ICE's are so popular. I strongly believe electric well eventually take over though. The only other concept that has merit IMO is the flywheel. It's actually been used in many successful prototype vehicles. http://en.wikipedia.org/wiki/Flywheel_energy_storage

 

[PurpleCherokee]

Has anybody mentioned anything about working on the GEARING issue rather than a HP issue on the side of the motor? That electric motor has got PLENTY of torque to keep the jeep, and accelerate the jeep at 70mph. The problem is, getting the gearing right and upgrading the drivetrain components to handle all that torque. If you've got that, you've got the solution. And since you're ditching the 4.0 all together, then you're not limited to whatever tranny will fit the 4.0. Maybe start looking for a six or seven speed tranny?

 

[AnarchyJet]

I see problems

I happen to work for a company that builds generators, and 90% eff. is just not going to happen. There are just too many losses in a typical rotor and stator, and how you drive it will play a big part. A 50-100 kw, direct drive alternator is 80% eff. tops. If you do a belt drive, it drops to 65%.
Also, a good electric motor will be 85% eff. so your diesel is down to .68% efficient. Now bolt that up to a driveline with 25% loss, and you are down to 51%
The only real way to make an electric hybrid work with current technology, is to mount the motors directly to the wheels and eliminate the drive line losses. Volvo is doing this on their new hybrid. Add in regenerative braking, and expensive lithium Ion batteries and you have something to work with.
It's not that your idea won't work, but I think you would be lucky to maintain your 18 mpg.