Contour Enthusiasts Group Archives Forums Modifications Forced Induction intercooler vs. more boost

Dude, these cracks about "serious lack of understanding" are based solely on your MISREADING what we were disagreeing about. Like I said before, I had no argument with 90% of what you were telling me, and kept repeating because you convinced yourself I was arguing against it. So I'm sorry, but I do take offense.

I could argue it either way, but so could you. You and know, correctly or incorrectly many call Nitrous Oxide forced induction.

I'll even refer you to a board you may moderate

Forced Induction: Superchargers, Turbos, Nitrous

Ok, enough crap disturbing for one day, I really don't want to argue semantics or religion.

I'm game for politics, however.

TB

I don't disagree that there is much to learn before really attempting the project. But I think I do understand enough that what I was saying was reasonable. And I probably shouldn't have gotten my hackles up, I'll apologize for getting uptight.

Your earlier guess was correct, I'm thinking of an electrically powered centrifugal compressor. Done right, this would have less drain on the engine than either a turbo or a belt supercharger, therefore yielding more gains per PSI of boost. But electric motor choice being what it is, it will have to be limited to low boost. Parts might be not much more than $1000. This doesn't count all the overhead that comes from dealing with other engine issues that have to be looked at, but it's still likely to be cheaper than other FI setups (other than those made of used parts).

Another advantage is that since the boost pressure would be regulated electronically (ouch, a motor controller is one of the most expensive parts), there is no dependency whatever on engine speed. The boost can ramp up while you're pushing the pedal down.

A system like this would be most ideal for a hybrid-electric car, which already has a beefed up higher voltage electrical system. Such a car would get even better mileage than it does now, if it used an exhaust turbine to power its generator. Then you'd have an electrically decoupled turbocharger, with mileage better than anything in existence today, yet lots of power on demand.

Paul,

just a hint, but have you looked into the power requirements to drive an electric fan to sufficiently supply enough air to run any sort appreciable boost pressure on a given engine? Have you compared those power requirements to the additional drive loads for an appropriately sized alternator? I believe you will be in for an unpleasant surprise. Even more so when you consider the extra weight associated with that large of an electric motor as well as any additional batteries.

I think electrically driven forced induction has a good potential for short-term transient conditions, but to say that it take less power to drive is short sighted at best. It will take the same mechanical energy (probably more, due to conversion inefficiences) from the engine to drive the alternator to make the required electrical energy as it will to drive a mechanical supercharger. Granted, the electrical system does allow you to spread out the time when the power is generated, but only so much. Further, a turbocharger is driven by mostly wasted energy (outgoing heat and flow velocity in the exhaust system) and really only costs power in that it eliminates any exhaust scavenging effects. If ever there was such a thing as free power, the turbo is about as close as you can get.

Also, as far as component cost, I think you are grossly underestimating the costs associated with electric motors and thier controllers at the required power levels. Keep in mind the power levels required to provide the required flow at the desired pressure. A good example is on a typical Ford 5.0L engine with a centrifugal supercharger and a power output in the 400hp range, it takes somewhere in the neighborhood of another 70hp to drive that supercharger (ie, engine would be putting out 470hp in the exact same setup if it didn't have to drive the blower). Even if you cut that in half for the 200hp range you are looking at, that is still ~35hp.

Don't get me wrong, I would be overjoyed to see a functional electrically driven supercharger, but the current level of technology doesn't allow it to be anywhere near competitive with other methods of driving a compressor. The closest I have seen to a succesful system design was the "dynapac" I believe it was called. And even then, its benefits were quite limited and very expensive.

Rara makes good points about weight and power requirements. I believe 50HP electric motors weigh hundreds of pounds. (I was dreaming about a car the produced electricity in the engine compartment, and instead of a transmission had computer controlled motors at each corner. Put a 50HP electrical motor at each wheel, with very little driveline loss

however, I think I had over a half ton of motors before you added anything to the car such as the engine and generator

Anything that weighed less probably costs a lot more.

Of course we know that power (electrically speaking) is equal to (current x voltage) so you have to increase one of them to produce large quantities of power.

1HP = ~745W (rounded down even)

At 12V to produce 745W you need 62A of current. You can quickly see that the 12V system in today's cars can't supply that for long. Heck even the proposed 48V systems will still need nearly 16A of current to make 1HP.

Higher voltages provide different challenges as you need better insulation and isolation to prevent arcing and to protect the humans that would ride around in the vehicle.

If you had a 240V generator like you might find running off a 8+HP gasoline engine, you would need about 3A of power to produce a single HP and most of those generators are only rated for say 10A of 220V power (or 20A of 110V) depending on the engine. So you are going to need a BAG (Big A.. Generator) to produce sufficient electricity for a sustained period of time.

I wish it were easier, as I'm far more comfortable with electricity than I am with mechanicals

TB
I do have a EE degree, but so much has changed since I graduated

hey, before you waste your money, Starter motors are not capable of sustained use. The duty cycle on them sucks! More like 10% If you crank for 15-20 seconds you have to wait 1-2 minutes to cool it down. Remember, that is even with a cold start condition with it being bolted to a giant heat sink (the engine)!

You'd be better off using an exhaust driven turbine to be honest. The cost will end up less once you have paid for a motor that can sustain the boost-on-demand as well as the electrical system and cabling upgrades.