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Old 08-01-2017, 01:05 PM   #1 (permalink)
Panther140
 
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Electric Motor Mounted Like Supercharger -- Electric assisted engine

Scroll down to the large font if you want to cut to the chase.

I have an idea that I wish to use to reduce load on my engine. This is to allow the engine to stay in V4 mode longer. Its a 2007 Silverado 1500 5.3L Crew cab pickup truck. I recently got a new job, and I have to drive 60 miles round trip of interstate every day. (I may not be at this job location long enough to see any ROI from buying a commuter car.)

I'm going to paint a mental picture for you about my idea, so just play along: Picture a V8 engine with a centrifugal supercharger mounted somewhere under the hood. See that supercharger pulley that is driven by a belt? That belt is being driven by the crankshaft, which has a pulley mounted on it.

Now, leave everything exactly the same, but swap the supercharger out for an electric motor. So you have an electric motor that is mounted in the exact location and basic pulley configuration as a centrifugal supercharger, but it delivers torque to the crankshaft, rather than receiving it from the crankshaft.

The controls do not have to be complex. This is not supposed to be a significant amount of torque being delivered. It would be nice if it could have regenerative braking capability, however. Any time the engine slows down, I want the motor to salvage its inertial torque and decelerate it faster than parasitics would decelerate the engine. I'd also like to use a motor's regenerative capability in conjunction with engine braking. I'd size the pulleys so that the electric motor can deliver torque to the crankshaft in the vehicle's main operating range.

Does anybody have any information about whether or not this has been tried before on a research level or a DIY level? I'd love to hear any information or answer any questions that you guys might have for me.

I haven't decided which motor would be optimal to use. I have plenty of room in my truck's bed for a small battery bank. I'd really like suggestions on motor selection and sizing. Keep in mind that the point of this is to save money. I'm not going to spend thousands of dollars to gain 2mpg on an old truck like mine.

The benefits to this idea are that it is non-intrusive, and potentially budget friendly. There is no need to remove or significantly alter any drivetrain components when building this. There is no sacrifice in performance of the vehicle, and the motor could potentially be used to augment the engine's torque when accelerating if you chose to.

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Old 08-01-2017, 01:19 PM   #2 (permalink)
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Its been done before by GM with its BAS hybrid system. Its also been done by an old EM member on a 2000 Subaru Outback.

Electric Assist Project: E-charger (2000 Subaru Outback)
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Old 08-01-2017, 02:22 PM   #3 (permalink)
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There's this car that does what you're looking for:
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Old 08-01-2017, 03:46 PM   #4 (permalink)
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Hello Panther140,

Quote:
I have an idea that I wish to use to reduce load on my engine. This is to allow the engine to stay in V4 mode longer. Its a 2007 Silverado 1500 5.3L Crew cab pickup truck. I recently got a new job, and I have to drive 60 miles round trip of interstate every day. (I may not be at this job location long enough to see any ROI from buying a commuter car.)
Daox and vskid3 have already covered GM's BAS system and other attempts to "electrocharge" your engine, basically attempting to mild-hybridize your truck. My first thought was that cylinder deactivation is controlled by the truck's computer, therefore it should be possible to tweak the tune in that computer to change when/how long/etc. the truck runs in 4-cyl mode. So I searched a bit and found this forum post.

It has a nice list of things the computer looks for to determine whether it should or should not be in 4-cyl mode. A few comments suggest staying below 65mph and/or keep the load low, which jibes with that list. So, step one for you would be to slow down and see what speed you can maintain while keeping it in 4-cyl mode.

From there, one could surmise that standard Ecomodder aerodynamic and other load-reduction tweaks could potentially increase the speed at which you can maintain engine load low enough to allow 4-cyl mode: Air dam, grille block, tonneau cover or aerocap, wheel covers, synthetic gear oils, higher tire pressure, etc. All things intended to reduce the amount of force it takes to push the rig through the air going down the road. There's a max engine rpm at which it will allow 4-cyl mode too, though, so you may still have a speed limit.

Essentially, you can likely get as much or better fuel efficiency gains by modifying your driving style and/or some minor tweaks to the truck vs. the expense and tuning headache of adding a BAS system or similar.

Here's another thread.

This one lays out the timing. You have a ~91% duty cycle for 4-cyl mode - for every 10 minutes in 4-cyl mode the engine will switch to 8-cyl mode for 1 minute before switching back. It also has a much more detailed description of how the system works.

Near the end of the first thread, this company was suggested.

They apparently offer a plug-in device (Plugs into the OBD2 spot, unfortunately probably prohibiting the use of a ScanGage or similar) that extends the amount of time the truck spends in 4-cyl mode, with all sorts of claims about increased fuel economy, etc. Might want to dig into their FAQ and search around for testimonials, etc. on the web and see if it might be of interest.

Apparently it is the same 4 cylinders that are turned off: 1, 4, 6 and 7. The other cylinders lack the necessary additional oil gallery, special lifters, and control mechanism. Not sure what it would do to the balance of the engine if you modified it so all 8 cylinders had the tech and had a custom tune that switched back and forth between the two sets of 4.

If you want a potential "bolt in" solution, where in this case "bolt in" means "all factory parts, but a *lot* of work to round them all up and getting them to work in your truck", find a wrecked 2-Mode Hybrid Tahoe or Suburban or similar GM truck product, and swap in all the hybrid tech and related harnesses, batteries, ECM's, etc. You'll still probably need a custom tune to get it all to play nice together.

Have fun!
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Old 08-01-2017, 10:11 PM   #5 (permalink)
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Electric motors are a dime a dozen. More of an issue is the battery and controllers.

This is a pretty cheap lithium cell:

https://www.ev-power.eu/LiFePO4-smal...u-case-CE.html

To get 144v, you'd need 45 of them in series, which comes out to about $1100. A controller might cost you nearly that much too, though I admittedly don't know much about that market. You'd be able to get 20 amps of assist for 1 hour taking the battery from full to flat, which you probably shouldn't do if you want it to last. That's approximately 3.5HP of power, after losses. 45 in series could support about 35HP of assist for 10 seconds, or ~10HP continuously, which would last about 15 minutes if you're leaving 10% capacity at either end. If you wanted 30HP continuous, you're looking at around $3000 in batteries, minimum, or you risk damaging the batteries from the current draw.

I could guess at how much power your truck needs to move along the highway - probably about 40-45HP, give or take. If you're getting 16mpg and added 3.5HP of continuous assist, it would bring you up to about 17.5mpg, assuming no gains in efficiency from things like staying in 4 cylinder mode longer.

By comparison, my car gets about 90mpg at 60mph. Adding 3.5HP of continuous assist might bring it from 90 up to maybe 130-145mpg. The absolute amount of fuel saved would be the same for both of us though.

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Old 08-01-2017, 11:26 PM   #6 (permalink)
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Welcome to Ecomodder.

Quote:
I'm going to paint a mental picture for you about my idea, so just play along:
Do go on. I have similar intent, with a slant-four diesel; based on what I've learned here:

Controller mods or build for E-assist altermotor

Quote:
Originally Posted by HaroldinCR
My plan, if ANYONE would be interested, is to try to get a controller working for the E-assist alternator, which can put out over 20 HP at 55v and expected 30+ HP at 72V.
The part in question is from Buick Lacrosse and Impala hybrids. I measured one at a car lot as 8.5" pulley-face to rear, and ~8" in diameter. The controller enables regen, but stop-start needs some thought (with a five-speed manual). I lean toward a toggle switch on the shift knob.
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Old 08-02-2017, 06:03 AM   #7 (permalink)
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Aside from the substantial cost of batteries and controller, there is one more annoying hurdle which is actually getting power to the crankshaft. Every single combined alternator-starter system out there uses dual belt tensioners, and I think there's a good reason for that.

You would have to figure out a place to add a second tensioner to your belt before the motor if you want to replace the alternator with a motor. Or, you can use a toothed belt and add an extra pulley. I know that's a common way to power dry sump systems, but I am not sure how difficult it would be to do that.

There is of course a limitation, which is that the belt cannot handle very much power. Supercharged engines are probably the most demanding on the belt so that's a good place to look for clues as to how much. I recall doing the calculations and a Lotus Elise SC should put something like 10Nm on the crank pulley, which is probably around 20Nm on the supercharger pulley. Since the supercharger pulley is fairly small, I think with a larger pulley you could probably send 20Nm to the crank safely with a 5" crank pulley but I wouldn't go above that. Your engine pulley is I think 7.25" so you might be able to get away with close to 30Nm.

Frankly for your application I think this is the wrong solution; you already have a big V8 with a lot of power ready to go, if you press the gas pedal harder and it turns on the extra 4 cylinders, what is wrong with that? The efficiency of your engine actually goes up because those 4 pistons aren't dead weight anymore. The point of a mild hybrid is to provide some extra torque and stop start capabilities, but your engine is already very powerful and has quite a bit of fuel saving measures, so it would need a very powerful electric motor and battery to make a difference.

Last edited by serialk11r; 08-02-2017 at 06:12 AM..
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Old 08-02-2017, 09:45 AM   #8 (permalink)
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Great idea and great project, but you will see greatest financial benefit from aeromods.
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Old 08-02-2017, 12:49 PM   #9 (permalink)
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Quote:
Originally Posted by ksa8907 View Post
Great idea and great project, but you will see greatest financial benefit from aeromods.
That is probably true. I'm doing those, but I didn't want to combine them with this thread about mild hybrids. This truck's biggest issue on the interstate is definitely wind drag.

Incorporating aerodynamic modifications may reduce the size of the motor that I need to use in order to keep my engine in V4 mode for the majority of the time.
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Old 08-02-2017, 01:00 PM   #10 (permalink)
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Quote:
Originally Posted by serialk11r View Post
Frankly for your application I think this is the wrong solution; you already have a big V8 with a lot of power ready to go, if you press the gas pedal harder and it turns on the extra 4 cylinders, what is wrong with that? The efficiency of your engine actually goes up because those 4 pistons aren't dead weight anymore. The point of a mild hybrid is to provide some extra torque and stop start capabilities, but your engine is already very powerful and has quite a bit of fuel saving measures, so it would need a very powerful electric motor and battery to make a difference.

The parasitic losses while in V4 mode are less than the parasitic losses of the vehicle in V8 mode. The inertia of the pistons at a given speed does not change when you fire those cylinders. However, the side loading on them increases.

The pumping losses are increased in all 8 cylinders when the vehicle switches to V8 mode.

I think that you are right, though. The supercharger style mounting is not the best way to gain efficiency via an electric motor. I think that the biggest gain would be to use a system that would allow more direct regenerative braking.

The reason that I wanted to use an electric motor was because there are a lot of supercharger parts and concepts that would apply.

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