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Old 09-08-2009, 08:56 PM   #1
Mini-Skoolie
 
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do-it-yourself electric hybrid idea

So, I had my first major disappointment last week with our bus. We loaded it and our 20' trailer full of fake fur and glowey things and started off on the glorious road to Burning Man. Well, things started off just fine until we hit a stop light on a hill. When the light turned green, I floored it in first gear, and found to my surprise that we were not moving forward. The engine (a DT360[small, I know] with an 4 spd auto tranny) just didn't have enough power at the low end to start up the hill. If I hit the same hill while moving (and able to keep the engine between 2500 and 3000) I can do just fine, but starting up with the engine running around 500 rpm it would not put out the power necessary.

There are a few things I know I can do to get a little more power. We've already adjusted the timing, fuel screw and governor, but I think I can adjust the governor a little more and I'd like to add an intercooler, and maybe a bigger turbo. We're talking single or double digit horsepower gain here, though, and I think that in order to have enough power to haul a trailer full of stuff, we need to think a little bigger. Something that briefly crossed my mind was adding a low gear, somewhere in between the transmission and the rear diff, for the soul purpose of being able to start up a hill. But that idea was scrapped because it sounds like a lot of work and cost just to be able to temporarily change the gearing ratio.

My next idea, though, I'm still kicking around and looking for feedback. So, here goes: The front of the engine has some giant wheels for belts coming strait off the engine. I was thinking of welding on a gear to the front of that and adding a chain to an electric motor that I could engage from the driver seat with a switch when I need more power. A friend of mine that works with electric cars swears by an electric motor that can put out about 200 hp for around $1500. This would nearly double the peak hp of the small engine, be pretty easy to install, and I wouldn't have to do any mods that would hurt my mileage. I would need a larger battery bank, though, but I was planning on increasing that to increase the length of time that my freezer can cool, anyway. The main thing I would be worried about would be breaking something in the engine. Or wearing out the electric motor as it would be spinning even when it is not powered since it would still be attached. Well, that's it for my rambling. Shoot my idea to threads.

-T
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Old 09-08-2009, 10:30 PM   #2
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Re: do-it-yourself electric hybrid idea

The electric motor when not powered up would definitely affect your mileage.

Sounds to me like you need a different torque converter.
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Old 09-09-2009, 09:51 AM   #3
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Re: do-it-yourself electric hybrid idea

Since the motor will only be engaged from a standstill, is there a way to install a clutch of some forme to disengage the motor's gear while the bus is under power from the engine? This will save both MPG for the engine and wear for the motor. Yes, it's a little more work, but otherwise your idea sounds great.
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Old 09-09-2009, 02:16 PM   #4
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Re: do-it-yourself electric hybrid idea

Correct me if I'm wrong, but I thought that electric motors typically don't have much friction since there aren't pistons or anything that need to move, which is why you can usually turn over an electric motor with your hand on the output shaft, but not an engine. Obviously it would be less work on the engine when the electric motor was engaged, and I don't think it would create too terribly much work when the motor is not powered. Wear is a concern, but I think that a motor designed for electric vehicles probably has a pretty long lifespan.

I'm not 100% sure about all this, though. Need to consult my electric vehicle specialist friend.
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Old 09-10-2009, 01:07 AM   #5
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Re: do-it-yourself electric hybrid idea

Keep it floored and see what happens. Seriously. You're going to get the tranny fluid plenty warm, but I PROMISE that bus will move eventually provided you don't have a different major mechanical problem such as a broken one way clutch on the stator in the torque converter. You need to let that torque converter spool all the way up to its stall speed. At the same time the engine RPM's will climb and the increased load will result in more exhaust heat which means more boost (yes, it's the heat energy in exhaust, not the velocity/pressure that provides the majority of the energy for the compressor). More boost is going to give you more power.

More than once I've had to step on the pedal and hold it there for what felt like an endless 5-10 seconds before anything at all happened, but eventually it did happen. I either moved forward or I broke the tires loose. I've had to do this many times due to the terrain I take my bus on at times.
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Old 09-10-2009, 02:16 PM   #6
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Re: do-it-yourself electric hybrid idea

Quote:
Originally Posted by Smitty
Ditto here ....but you'll have to generate electricity to power an electric motor, and since energy isn't "created" (merely transfered) you're simply taking power from the bus motor to feed the electric one. Similar to running a car off hydrogen (I tried it....it's hype).
Yeah, totally true. This would be a pretty poor implementation if I was trying to increase the overall horsepower, or increase the overall efficiency. What I'm hoping for, though, is getting a momentary power spike when I need it, which would deplete the batteries, but then they would be able to charge while cruising. This is pretty similar to the concept behind traditional hybrid vehicles which get a large increase in their fuel economy in city (with lots of stops and starts), but doesn't change the efficiency of the vehicle really at all at highway speeds. (compare a 1980s vw rabbit to a prius, and the rabbit is just as good at highway mileage)

Quote:
Originally Posted by the_experience03
More than once I've had to step on the pedal and hold it there for what felt like an endless 5-10 seconds before anything at all happened, but eventually it did happen. I either moved forward or I broke the tires loose. I've had to do this many times due to the terrain I take my bus on at times.
I floored it for quite a while to no avail, but maybe it still wasn't long enough. We were really loaded down, though, with I'm guessing around 20k extra weight. I could fill up some 55 gal barrels of water and do some more tests and see if holding it longer helps. I didn't think about the turbo having to spool up. It seems like the engine never really got above 500 rpm. Maybe that means I didn't hold it long enough.

There's also the problem of spooling taking so long that the light turns red again before the bus gets enough speed to get through the intersection.
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Old 09-10-2009, 05:20 PM   #7
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Re: do-it-yourself electric hybrid idea

i wonder how grossly overloaded your skoolie was.

i had a dt360 loaded going to bm with a trailer and weighed in at around 34K pounds. That's about 14K pounds of cargo. With an allison at545 i never had an issue like you are talking about. Sure she was slow uphill, but never had a time when she wouldn't take off from a standstill. my gvw was 28.8K.

What rear end gears do you have? I think i had 4.56:1 rear gears.
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Old 09-10-2009, 07:54 PM   #8
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Re: do-it-yourself electric hybrid idea

What do you have for gears, tires, and transmission? There are a few AT545 torque converters out there, including one with the lock up feature. I'd be willing to bet a swap there would help you out. Of course you don't get something for nothing and you would probably lose top end and mileage.
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