Replacing R/R for better MPG?
 

I am looking to replace the OEM Shunt type R/R with series unit, and if my math correct depending on speed this should give me 3-13% MPG improvement?

OEM stator is rated at 35A (420w) and this is constant load due to shunt type R/R. The actual electric load is 190w less, which with series unit should reduce engine drag by 0.26hp.

Per calculator depending on speed (35-65mph) road+aero load is 2-10.3hp, so the 1/4hp drag reduction should give ~3-13% improvements.

Am I missing something?

I suppose at lower speed the stator output will be less than max, so 13% is over-estimate.

If we are talking about a generator system then minimum drag is when there is no current in the field windings or the armature is not moving. The core of the field coils will have some residual magnetism so there will be some slight output with the armature moving. A clutch on the armature shaft could control it such as used on an AC compressor though there would need to be enough current from a battery to engage it.

Just remove the alternator, and install an exhaust driven turbine driving a generator.
Really, you don't need an alternator, are better off with a rotating exhaust turbine.

:rolleyes: That's just gotta be a joke. If such a thing existed and was viable, we'd be using it already I'd think. Back pressure would reduce performance and if it were made so that it wouldn't do that so much then it probably wouldn't be able to keep up with enough charging. A couple little windmill generators at the bar ends charging a pack of Lithium ion batteries on a no alternator/generator engine would probably be just as effective. (or just as ineffective as the case would probably be) If real, then I'd want to see a source.

Back pressure trades top speed for torque, so your MPG should go up, as well as your acceleration.

As far as an exhaust driven turbine, powering an alternator, no one invented this yet.
But if you want to ride alternator free, the exhaust is a good place to harvest the energy from.

A lotta "shoulds" and "ifs" and "no one ___ yet" in there. We like tested and proven stuff on this forum.

Nothing works tested and proven 100%, however, back pressure allows more hot exhaust in the cylinder to warm up the incoming cold air/fuel.
It's a proven fact to increase torque and MPG. That's why many manufacturers do this especially for small bikes, and performance cars as well, using exhaust back pressure valves, or some form of restrictive exhaust can.

I was talking about the exhaust-powered alternator, obviously.

I think trying to disconnect an alternator, is just as unproven.

Nope! There are folks on here who have run A/B/A tests of alternator deletes, and good discussions of the pros and cons surrounding them.

Hahaha!
Disconnect electrically only not much improvement.
Total disconnection belt and electrical can be up to a 10% improvement on a small car.

I know turbochargers use exhaust gas to spin them up, but that's not like trying to spin a generator. Even then, I think turbo chargers draw off some HP to spin the turbo. I understand it works to get more air into the engine for even more HP... an electric generator would be a more demanding load and likely would not give a worthwhile return.

Alternator deletes have been done on drag racing machines where batteries last long enough to do a run or 2. So it works for that. But it just wouldn't be practical for much else. Small dedicated gas generator to keep battery charged on a vehicle sans alternator may free up HP for the vehicle, but then it takes fuel to run the generator. Added complication with little to no net benefit... Back to square one again as far as I can tell.

Currently bikes use permanent magnets spun around a stationary stator. The extra power is just dumped into a big aluminum heat sink. I think if an improvement was made it would be to give us field regulation as opposed to resistance. I would like that a lot.

Some bikes capture the energy in a capacitor, that will rout the power to a LED strip around the bike.
The strip will start to glow, as soon as the battery is charged.
Since it's waste energy anyway, it can very well be used for less necessary mods, like decorative lighting

Well if it's wasted any way why not run a little 12v air pump
Fill a one gallon tank with 220 psi run it to an air amplifier this one would give me about a minute of boost at 5psi
https://www.zoro.com/exair-air-ampli...ym8aAqVK8P8HAQ
http://www.northerntool.com/shop/too...2543_200672543

Volvo does this to some of their luxury cars, called their 'power pulse technology'.
A small compressor, small squirt of air, just enough to take the turbo lag away on their turbo diesels. As if a diesel didn't already have enough low rpm torque...

You could however, insert a blower on the air intake, resulting in about +1HP boost. Not that you'll notice :rolleyes:

5psi is worth 2.89hp to me
That's almost a third more power
Why would I want a turbo if I already have to much power from just the amplifier
My bike only needs 15cfm that thing will output 618cfm @38psi from 80psi inlet pressure
It will only do it for like 10 seconds
But my bike would be all splody by then