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.
 
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