Aftermarket hybrid/KERS

[Nicebiscuit 655]

Just idly thinking... but given the popularity of super/turbocharging our cars for more poke, but given that this is 2017 I'm wondering if it's technically feasible to fit some sort of aftermarket hybrid setup to an 86?

 

A lot of high end sports cars now are using electric power to boost performance. An interesting thought... don't know if anyone's tried it with similar vehicles

 

 

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[Nicebiscuit 655]

(And yes - I have been drinking)

 

 

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[Steeps 294]

Something I've liked the thought of, the problem comes from capacity. On the hybrid range of Toyotas if the electical capacity runs out you drop some efficiency but that doesn't matter because it's only needed for test conditions to get the cheap road tax. If you're using the system to boost performance this is a lot more noticable if it runs out of power. To increase the capacity you're adding a lot more weight, which wouldn't suit the car.

[Nicebiscuit 655]

Fair point. I suppose it'd be easy enough to at least keep the extra weight low...

 

I wonder what battery capacity you'd need? Probably wouldn't work in a track scenario but on the road you're rarely using the full 200bhp as it is, so a mild boost would go further...

 

 

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[nerdstrike 186]

Trouble with batteries is that for meaningful electric driven torque, you need lots of current, which means you need lots of batteries - individual cells can only discharge so fast. The Tesla system pre-heats itself to get best battery output in Ludicrous mode, and the longer range Teslas have greater performance as well as range. 

Next consider the commercially affordable systems, like the range extender in the i3, and the hybrid drive in the Prius. The engine is not directly connected to the wheels and just spins a dynamo. Lexus has some hybrid vehicles that use something resembling a beefy starter motor, but I don't think those add performance so much as poodle power for low speeds.

The only proper blended petrol-electric performance systems are currently found in £100000+ cars who have done the development to use the systems sympathetically - new NSX, Porsche 918, P1, i8 etc.

Basically I'm saying that a "KERS" system would probably cost more than your car to build.

[Nicebiscuit 655]

I don't doubt it... was more a thought experiment... it's going to be a long time til this sort of thing can compete with five grand bolt on FI kits.

 

But still I wonder why it's still the preserve of the £100k plus cars like you say... The daft thing being that they don't really need it - fuel economy or car tax is hardly an issue if you have a Ferrari...

 

 

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[nerdstrike 186]

If you wanted to treat it like a nitrous system, push a button to go faster you could probably manage a relatively inexpensive system, but you need to bolt a reasonably large motor right into the power train without it getting in the way of anything else. If you just kept the motor engaged while the engine is working, it turns into a generator. That's fine to a point, but creates fairly generous parasitic losses, that is unless you have a clutch system to disengage it when it's neither charging nor discharging.

Then you need to situate a couple of grand worth of batteries somewhere, and maybe there's managing the extra power so that it comes on and off smoothly and doesn't just VTEC yo' ass into trouble. You basically need two throttle maps on the same pedal, one for the engine and another for the motor which may or may not change depending on speed/gear. It's a lot of electronics and firmware programming I would think. Not really in the area of expertise of your typical petrol-head tuning developer, more the people that build custom ECUs.

Simple systems have been built for bicycles which just provide assistance whenever they sense you pedalling, but cars are on a much bigger and more complicated scale.

The expensive sports cars have taken great pains to blend the outputs of the engine and the two or more electric motors that drive various wheels. It's much more sophisticated than a traditional four-wheel drive system, up to and including negative power applied to individual wheels, and torque-fill that comes on at low RPMs or while turbos are still spooling. Much finesse and development time is required! These cars are forerunners of future sports cars more in our market segment I suspect. What is 100k now will enter the market in the £30-40k market in a few years time.

[Church 209]

Check fenton's electric supercharger thread over at ft86club. It's both of more reasonable budget, and also is step above convenience wise then just "button", engages depending on accelerator usage letting batteries recharge when cruising. Due way cheaper & simpler to implement such, lesser power usage, it gets by with more reasonable batteries weight & cost wise, yet providing that extra oumph in SC fashion. Would be highly considerable upgrade .. if not almost year long wait times for it. Still, closer to reality if not the not-mass-produced availbility issues even with demand much bigger then offer and also good technology demonstrator.

Imho there is big future to such .. if it also is accompanied with turbo-generator on exhaust. = Better economy then SC as exhaust gas energy is recycled, simpler to fit on existing engines/cars (as electric fan SC & electric turbine generator can be placed anywhere on intake/exhaust paths, due mechanical linkage not required. Heck, it can be placed even at rear muffler), +fine grained control & tunability possibility by ECU or other controllers. It might get a bit worse economy then classic turbo, but pros imho outweight cons. Immediate boost available (even at idle rpms :)), flexibility, ease of install not requiring cardinal intake/exhaust tubing mods ..

[nerdstrike 186]

Wow, they've worked hard on it. I suppose it's only recently we've been able to put enough battery in a small package to run a compressor like that. A novel idea with limited application. At some point you'll hit the threshold where you might as well have a full time turbo instead, because it needs so much juice from the engine to keep it topped up. It would suit the street-racer types for sure, possibly not track use when you're always up in the revs and the money might be better spent elsewhere.

[Falix 22]

The ideal is the electric turbocharger, F1 style, but we are a way off those being available off the shelf.

Theory goes:

 

Split a turbo in half, add electric motor instead of center bearings. These are larger and thus have packaging issues.

Turbo is then spun electronically to provide power at WOT where it would usually lag, IE low rpm WOT situations.

Over a certain RPM, exhaust gasses are sufficient to spin exhaust turbines at required RPM, motor switches to generator, being spun by the exhaust gasses whilst also transferring drive to cold side, providing boost, while refilling electronic anti-lag. Also the scavenging seems to remove the need for a wastegate, as they all seem to run without one?

The challenge is packaging this system, increased strain on the engine from  "1bar" manifold pressure almost instantly whenever the throttle pedal is touched, and the heat from the hot side on the electronic core.

 

Essentially one up from an electric supercharger as this does energy scavenging too, creating electricity AND boost from waste gasses.

[nerdstrike 186]

Interesting. It's a big unit what with the motor in the middle, but clever pass-through on power. Am I right in saying that you need a wastegate for two things?

1) Shedding excess boost at low RPMs where the turbo flows more than the engine needs

2) Blowing off pressure when throttle snaps closed but exhaust pressure is still up.

The first point is nullified by having control over how much current goes to the motor, but I can't see how you can get round the second, i.e. lifting off at high RPM. I guess the scavenging turbine doesn't have to be as large as you would normally have for that amount of boost, and maybe you can apply much more drag to the motor as the pedal lifts to keep the pressure down.

Obviously this clever setup is only making an ICE behave better and waste less energy, so in the end you can achieve more with by feeding electric power directly to the transmission, but that comes with more dramatic engineering costs.

[Nicebiscuit 655]

Neat.

 

 

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[Falix 22]

23 hours ago, nerdstrike said:

Interesting. It's a big unit what with the motor in the middle, but clever pass-through on power. Am I right in saying that you need a wastegate for two things?

1) Shedding excess boost at low RPMs where the turbo flows more than the engine needs

2) Blowing off pressure when throttle snaps closed but exhaust pressure is still up.

The first point is nullified by having control over how much current goes to the motor, but I can't see how you can get round the second, i.e. lifting off at high RPM. I guess the scavenging turbine doesn't have to be as large as you would normally have for that amount of boost, and maybe you can apply much more drag to the motor as the pedal lifts to keep the pressure down.

Obviously this clever setup is only making an ICE behave better and waste less energy, so in the end you can achieve more with by feeding electric power directly to the transmission, but that comes with more dramatic engineering costs.

Yep, essentially wastegates stop you feeding too much boost, but when you have direct electronic control of the drive transmitted, I guess you can just stall the shaft?

 

And yes, these are far more likely to be eventually available to us than direct-drive KERS.