KERS - the future of antilag?

[NISFAN]

I'm thinking generators produce a linear but constant power supply dependant on revs. This means if sized for average engine speed, they don't produce enough power at low revs to re-charge batteries, etc. Also the output cannot be adjusterd at times when you don't need the power.

Whereas an alternator has got 'need' control, and also has the capability to produce enough power at low revs to charge things.

So for example, an alternator can use a lot of (engine) power if you had the aircon, lights, wipers, etc on because there is a lot of power drain going on. But on low load situations it self adjusts to not require the same engine power. The perfect device.

Generators require a certain amount of power to drive them regardless of load on the electrical system. To have a generator large enough to cope with a 'modern' car, it would be a huge device, much bigger than a starter motor.

Recently, intelligent alternator control devices have appeared, whereby the alternator is fooled into working really hard during engine overrun, which in turn means it uses 'engine braking' energy rather than 'engine power' to drive it. Most new BMW's etc use this technology now for fuel saving.

[ru']

The car industry is moving towards (or trying to) having a single starter motor/generator device (as well as using higher voltage than 12V, say 40V ish). This will enable basic regeneration power systems.

[minos]

well i don't think it will be long before cars don't come with starter motors at all, i know some of the "i stop" techonolgy is relying on starting the engine, by making sure the car know where the piston is located and then start a combustion on a piston that is traveling down, will be a shitty combustion but enough to get the engine moving

as for now it still engages the stater driver but, car starts in less than 0.3sec (at least on the new mazda3, i guess with some more R&D, they will be able to ditch the starter

[kismetcapitan]

Originally Posted by NISFAN

Recently, intelligent alternator control devices have appeared, whereby the alternator is fooled into working really hard during engine overrun, which in turn means it uses 'engine braking' energy rather than 'engine power' to drive it. Most new BMW's etc use this technology now for fuel saving.

I want that!!! The ultimate alternator upgrade!!

[NISFAN]

Hmmmm, you've got me thinking that I want that too now

I have an aftermarket ECU that would be capable of turning the alternator 'off' under load. Not sure I would want to do that at high RPM, as I want all the power needed to fire the plugs.............
............. but perhaps to aid anti lag, I could turn it off at high throttle openings at low to mid revs. This will give the engine a couple of extra horses to get through the laggy phase.

I don't think it would be that difficult to set up another circuit that makes the alternator engine brake, overcharge either. Could do this by simple brake light activation, or perhaps via the ECU (road speed above xxx, and throttle position below yyy)

Cool thanks for the idea Kismet

[kismetcapitan]

dude, let's engineer this thing together. The stock alternator is 85 amps, I've got a 160 amp Infiniti alternator on the car now, and I would like to go up to a 200 amp unit.

My one concern is the ignition system. Mine seems to hate low voltage conditions and will stutter and stall if the battery is low (Splitfires + HKS DLI + NGK surface-gap plugs which require a lot of juice). During hard acceleration, my car seems to use a lot of electricity through the ignition - after a spirited romp, the battery and the car's system voltage is lower, similar to if I've been sitting in traffic with the A/C and my 800 watt stereo cranked up.

What ECU are you running? I've got a simple Power FC - I'm trying to remember if any of those wire terminals on the Datalogit box are programmable outputs?

[kismetcapitan]

oh, and a question about alternators. There's no clutch; the internal rotor is always spinning as far as I know. Is it when the regulator switches on, that resistance is created and a load placed on the engine? Just how many horsepower does an 80 amp alternator sap out of the engine? a 160 amp? I think I better hit Google...

[NISFAN]

Cool, see this

BMW regenerative braking

[Pete G]

and this

Combined starter-alternator reduces petrol use: News from Dow Corning

[ru']

The alternator load on the engine will be pretty much proportional to the current it's producing, i.e. it will be a lot easier to spin if it's disconnected from the battery/electronics, and if the battery is flat and/or you're drawing a lot of current then it'll be a lot harder to spin.

[Cris]

Originally Posted by kismetcapitan

oh, and a question about alternators. There's no clutch; the internal rotor is always spinning as far as I know. Is it when the regulator switches on, that resistance is created and a load placed on the engine? Just how many horsepower does an 80 amp alternator sap out of the engine? a 160 amp? I think I better hit Google...

the alternator is an electromagnet. it only drags on the engine in operation component drag aside. I forget whatthe conversion rate is but it's something like 20:1. if youcould getitto work under braking you'd stopa bit quickertoo. probably notenough to care about mind.

[kismetcapitan]

Assuming a future retrofitted starter/alternator combo would be small enough to stick onto the RB26...perhaps start/stop usage could be effected on a Skyline as well.

One wouldn't want to do that until the engine was well up to temp though! But start-stop is a good idea; I remember first trying it out on the first generation Honda Insight. Works just like a golf cart - hit the gas pedal and you're rolling and the engine is starting all at once. If you wonder about the need for widespread implementation of start/stop technology, walk through a traffic jam, between the cars, during a summer day. When I'm threading my bike through traffic, it feels like the temperature shoots up an easy ten degrees. All that heat equals lost and wasted energy.

Would need a big battery though...or, hehe, a supercapacitor and a flywheel energy storage unit, as per the F1 cars

I wonder if my 25,000th post here will be talking about the six flywheel boxes I've got in the boot, some polymer-technology battery pack where the rear seats used to be - and an 800kW electric motor where the RB26 used to be!

[kingsley]

Originally Posted by kismetcapitan

current hybrids use the electric motor as a starter motor, so they've clearly sorted out whatever issue they were having.

Why (there must be a good reason) would an alternator produce AC which has to be converted to DC, when a dynamo could just produce DC from the start? Maybe for voltage regulation? (an alternator without a regulator would produce too much juice at high RPM - it makes peak power usually around 3000rpm, that much I know)

I'm not massively genned up on this topic so forgive me if I have some of this wrong.

Old cars used to be fitted with dynamos instead of alternators. Dynamos have a commutator, like an electric motor, so they produce DC (although the voltage wouldn't be constant, it never goes below zero, unlike an alternator).

Back in those days, dynamos couldn't really be revved beyond 6000rpm. Not sure why, maybe it was something to do with the commutator. Anyway, as a result of this, they were geared 1:1 with the engine.

The main problem was that they didn't start producing much output until about 1200rpm, which means that you're getting no charge on tickover and flat batteries were a potential problem with lots of slow driving.

Alternators could be revved faster and although these too didn't start producing decent charge until 1200rpm, because of their higher rev limits they could be geared 2:1 with the engine so you still got charge at tickover.

All the above from reading some 70s car books during my childhood so the info is a little old.

Cheers,
Kingsley.

[ChristianR]

citroens wrc car uses kers like system..

Citroen WRC Hymotion4 | People | Racecar Engineering

saw it on dave, will give 100bhp increase, or can be used to drive inbetween stages emissions free and silent

[Cris]

It strikes me that a system like this could be used to replicate the ATTESA system.

If you had a 'normal' RWD chassis with the front wheels connected to an electric motor (or small pair in the hubs). Usual guff about using the electric motor to slow the car, charge the battery etc. When the rear wheels start to slip the alternator steps in to 1 - decrease the torque output getting to the (rear) wheels 2 - supply energy to the front wheel motor/s. 'Leccy motors 'start up' quickly so the reaction time should be good. As part of a start-stop system you could use the front motors to pull the car forwards it traffic only using the engine beyond say 50% throttle or 10mph.

Of course you could have a Launch Control type mode which would use the engine and the motor and wouldn't have the alternator draw.