Full Time Electric Supercharger - Is it Possible?

S

staticGenerator

New member
Hello All,

I've been ruminating over supercharging my 2003 4.7l Dodge Dakota for a couple of years now. I'm hesitating over making modifications to the engine that are permanent or not easily removed (I have a warranty on a rebuilt engine for 5 years and I don't want to void it). In any case, there aren't any real outlets that cater to the Chrysler brand supplying SCs for these years, the only one I know of being Boosted Technologies, and they say their 1500 RAM kit will work with Dakota. However they say I'd have to make mods to the frame under the engine bay - not something I want to do. Also, their solution costs about $5K which is more than I want to spend.

This is not for racing. I live and haul with my truck in the mountains between 8K and 11K in elevation. My understanding is that we lose 3% HP per 1,000 feet in elevation, so at 8,000 feet I've lost almost 25% of my stock power. Here are my goals:
  • Between 3.5 - 5psi boost. At 8K feet, 3.5psi would closely match the naturally aspirated power produced at seal level (the atmospheric psi at sea level is 14.7 psi, at 8K feet is 11 so 3.7 psi of boost would about match that of the naturally aspirated engine at sea level).
  • Engage just above idol. I want the boost to start engaging as soon as the gas pedal is pressed. This will keep the boost on early and allow lower end torque, more important for towing.
So here is my plan to accomplish this:

  1. Build a supercharger following Alex's build, using a P-2 Centrifugal Supercharger and possibly the same BLDC motor.
  2. Limit the current draw to about 200A
  3. Looking at getting a used Chrysler generator/alternator (which puts out 48V and >200A) to power it
  4. Use a PWM boost controller something like this AEM Tru-BoostX Gauge-Type Boost Controller to send a PWM to the motor controller to keep the boost at 3.5-5psi
I'm aware that this approach would re-introduce parasitic power, even more so than a mechanical SC providing the same power.

My questions are:
  • Will the BLDC motor handle consistent power while driving, are they durable and able to handle the constant duty?
  • What are other possible problems or drawbacks to this concept?
  • Should I just buy an Eaton M90 SC, get a mounting plate fabricated, and forget about this whole electric SC idea?

I'm open to any other approaches/suggestions. Thanks in advance!
 
I am definitely not there yet but have some learning from my build so far.

  1. Power: Seems like the battery discharges in the realm of 10X of which it can be charged. For instance 100 amps x 48 volts = 4,800 watts at low boost level. Where draw on car charging system maybe 40 amps x 12 v = 480 watts. So need to charge for 10 minutes and boost for 1 minute
  2. Driving: I did an analysis of some of my data logs and found that the I have low manifold air pressure / vacuum (heavy or wide open throttle) less than 10% of the time. This seems to align with conditions of point 1
  3. Heat: I have a hard time keeping my motor cool even at low duty cycles. 5,000 watts plus is a lot of power and there is a lot of heat generated in the windings. If we had super conducting windings, that would be one less constraint. Honestly, I am adding at minimum air cooling and exploring water cooling for my motor even for my low duty cycle.
My conclusion is that an electric super charger should meet my needs for intermittent boost. If you want always on power, may be best to do engine mods, turbo charger or super charger.
 
GTHound said:
My conclusion is that an electric super charger should meet my needs for intermittent boost. If you want always on power, may be best to do engine mods, turbo charger orI will be using a 48 volt
Click to expand...

That's some very useful feedback I appreciate it. I was thinking about using a 48 volt generator like the one listed here on eBay https://www.ebay.com/itm/4047713722...xjIa-eIQ5C&var=&widget_ver=artemis&media=COPY

It will put out just over 200 amps continuous. However according to what you've just stated that will not be enough current to keep the motor running even at low boosts. I am curious however about the fact that maintaining 3.5 PSI at lower RPMs including up to 2,500 RPM should require much less CFM than high acceleration. So I was curious if I could use the electric supercharger to maintain lower RPM boost around 3.5 PSI. I'd probably use one of the battery packs from one of these rolling start type of systems that the generator I mentioned recharges. Then as you mentioned only using the supercharger when I really need the extra power going up the hill etc. I'm going to keep thinking about this option. And if I can't use an electric supercharger for this concept I could probably come up with a side mount supercharger that won't require me to cut into the frame or body of the truck under the hood.
 
Boost at very low rpm is a bad idea. It creates a tremendous amount of cylinder pressure and can cause severe engine damage - it makes your tuning window small, can cause uncontrollable detonation, blow head gaskets, beat up rod bearings, etc. If you need more low end grunt, the best bet is to honestly put some gear in the truck or downshift. On an engine with peak hp at 5,000 rpm, I wouldn't add any boost until at least 2,000 rpm, and then very little; but 2,500 rpm would be better.
 
AlexLTDLX said:
Boost at very low rpm is a bad idea. It creates a tremendous amount of cylinder pressure and can cause severe engine damage - it makes your tuning window small, can cause uncontrollable detonation, blow head gaskets, beat up rod bearings, etc. If you need more low end grunt, the best bet is to honestly put some gear in the truck or downshift. On an engine with peak hp at 5,000 rpm, I wouldn't add any boost until at least 2,000 rpm, and then very little; but 2,500 rpm would be better.
Click to expand...
Not to mention, why would you Boost before the manifold, only to have the Throttle body lower the pressure and Volumetric Efficiency again?

It would be better to have the Boost mapped to only the highest part of the throttle range where the throttle body isn't acting as a restriction to fight the Boost you are making.
 
My twincharged engine can produce 1.7bar abs pressure at 1500rpm or (or less if necessary) and although does obviously produce significantly higher cylinder pressures than naturally aspirated, it is mapped accordingly and hence the ignition timing is retarded and the lambda is set run relatively rich to mitigate knock. Also the duty cycle under these conditions is relatively low in my application.
 
staticGenerator said:
My questions are:
  • Will the BLDC motor handle consistent power while driving, are they durable and able to handle the constant duty?
  • What are other possible problems or drawbacks to this concept?
  • Should I just buy an Eaton M90 SC, get a mounting plate fabricated, and forget about this whole electric SC idea?

I'm open to any other approaches/suggestions. Thanks in advance!
Click to expand...
Not sure if it is still up to date but I would add an option, what would it cost to swap a 5.7 engine instead ? that is much a better gain than 5psi on a 4.7l.

I didn't test one myself yet but as an electronic tech that read and watch around this subject for a long time including Alex testing, eturbo projects are more often for temporary extra power during short time....doing it for extended time when hauling may be your main struggle....(Going up a long hill, you would expect boost to last 100x longer than Alex when drag racing)
It may be bad to say it here but i feel the mechanic supercharger would be a better choice for those conditions.
An eturbo fed by an alternator is like replacing the Sc belt by wires with more losses than a direct drive belt....
Adding SC lobes vs electric centrifugal to the comparaison may balance back a bit on overall efficiency but not on complexity.....

Back to eturbo, you would like an alternator to keep feeding it....You may need 2 or 3: Even if you can find one at 48v keep in mind changing 12v for 48v do the opposite on amp capacity. an high output 12v 300amps will remain 3600w nominal when rewired for 48v and only give 75amps in this configuration. You may find a huge one doing the 150-200amps needed but it could be expensive.
Running 10kw from alternators having 50% eff would need 20kw of energy (about 27hp) from the belt...., it may come close to fitting a Paxton/Vortech Sc and you didn't wire anything yet....(feed for though)
I would add batteries and a 5kw alternators to avoid over doing it even if it limit the 100% use to half duty to keep battery charged.

About parasitic wastes, i think it would be hard to get a negative result even if electric power isn't stored but taken from the engine: Assuming you can generate 5psi with a +/-15hp parasitic loss, it is still 33% flow gain that may return a 25% power increase minus that +/-15hp losses from alternators. Base on the above, we look for a net +/-50hp gain at the flywheel.

I don't think a RC motor would handle constant heavy loads. It will be soon temperature limited, you should try one water cooled (extra pump+radiator) but i would also check for larger motors in order to have a constant nominal power closer to the peak power needed
 
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Jeff23spl said:
Not sure if it is still up to date but I would add an option, what would it cost to swap a 5.7 engine instead ? that is much a better gain than 5psi on a 4.7l.

I didn't test one myself yet but as an electronic tech that read and watch around this subject for a long time including Alex testing, eturbo projects are more often for temporary extra power during short time....doing it for extended time when hauling may be your main struggle....(Going up a long hill, you would expect boost to last 100x longer than Alex when drag racing)
It may be bad to say it here but i feel the mechanic supercharger would be a better choice for those conditions.
An eturbo fed by an alternator is like replacing the Sc belt by wires with more losses than a direct drive belt....
Adding SC lobes vs electric centrifugal to the comparaison may balance back a bit on overall efficiency but not on complexity.....

Back to eturbo, you would like an alternator to keep feeding it....You may need 2 or 3: Even if you can find one at 48v keep in mind changing 12v for 48v do the opposite on amp capacity. an high output 12v 300amps will remain 3600w nominal when rewired for 48v and only give 75amps in this configuration. You may find a huge one doing the 150-200amps needed but it could be expensive.
Running 10kw from alternators having 50% eff would need 20kw of energy (about 27hp) from the belt...., it may come close to fitting a Paxton/Vortech Sc and you didn't wire anything yet....(feed for though)
I would add batteries and a 5kw alternators to avoid over doing it even if it limit the 100% use to half duty to keep battery charged.

About parasitic wastes, i think it would be hard to get a negative result even if electric power isn't stored but taken from the engine: Assuming you can generate 5psi with a +/-15hp parasitic loss, it is still 33% flow gain that may return a 25% power increase minus that +/-15hp losses from alternators. Base on the above, we look for a net +/-50hp gain at the flywheel.

I don't think a RC motor would handle constant heavy loads. It will be soon temperature limited, you should try one water cooled (extra pump+radiator) but i would also check for larger motors in order to have a constant nominal power closer to the peak power needed
Click to expand...
This is for performance within intended individual guidelines, I'm pretty sure no one is looking for more than short term, high efficiency momentary boost. The biggest return at least for my efforts is high efficiency, high performance with minimal invasiveness.

I've completed several traditional turbo projects and the novelty here is just as important if not more so for some than the power achieved. It's pretty obvious a large displacement motor would accomplish the same goal, but that's been done to death and not all platforms will lend themselves to this option with ease if at all, especially a modern vehicle with all kinds of firewall hurdles that must be jumped in order to do anything outside of stock, from VIN matching to electronic communication in order to accept a motor swap.

My 3.6L V6 in stock trim is 304 hp/ 273 lb-ft with variable valve timing, 5 psi without a parasitic tax would make it very fast and it's already that in stock trim. This is all about practicality, ingenuity and something different. Attempting to support the blower with an alternator would be counter productive to the process. It's purpose would only be to provide some degree of on board battery charging if I used it.

There aren't many public roads where I live that can sustain much more than +/- 6 sec of wide open throttle before speed is criminally and dangerously high for conditions. I can do 0-60 all day and short burst driving is what I prefer.
 
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