HKS Supercharger Teardown

[Rich 378]

If it's done right they fit the car with an uprated battery, alternator and starter motor to account for the increased use. Also the system should monitor the battery condition and electrical load to avoid stopping the car when there's high load or low charge. Mine seemed pretty good as I recall, but I've driven other cars that had utterly braindead start stop (Fiat I'm looking at you), so it seems a bit of a mixed bag. Much better with automatics in my experience too.

[Nicebiscuit 655]

My BMW had start stop. Was fine and never gave any issues. But a bit pointless.

My main issue with all this stuff is that it's mainly gaming the test cycle. In the end the CO2 the car puts out is directly related to the fuel burned. Both the GT86 and the Saab that preceded it can just about crack 40mpg if driving frugally or nearer 30mpg or not. Yet allegedly the Saab emits 50g/km more CO2. That's a physical impossibility. (I might add that the Saab also put out an extra 80bhp and weighed 400kg more...)

I'm not blaming the manufacturers, but the legislation seems counter productive - increasing complexity and shortening useful lifespan in the pursuit of dubious efficiency gains. Interesting the example of the twin charged 1.4tsi VAG engine came up. They stopped making that didn't they? Fairly troublesome as I recall. Polo GTI now has a straight 1.8 turbo...

I like the hybrids as they seem to offer genuine efficiency gains if you do a lot of urban driving. The Toyota system is nothing special on a run, but knocks a diesel into a cocked hat in stop start traffic, with the added bonus of not spewing out soot.

[DanJ 374]

Agreed, my most recent experience was a 1-Series manual with start stop, it was awful so I switched it off, that courtesy car was swapped for an E class auto, which was well calibrated and refined. Either way I was still glad to get the Scooby back!

The next thing for start/stop is "stop in drive", which is switching the engine off whilst your coasting, going down a long hill etc.

That will be much better in the real world in terms of fuel saved, but having driven some early development hybrid cars with it fitted I can tell you its very odd at first! You need a mild-hybrid of sorts for torque infill during engine restart though, although this may be better on the 48V systems.

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[Keethos 842]

Lol, I've always question why cars didn't just coast when off the gas but people kept on telling me it was because of safety and that you have to be in full control and if you're coasting you not in control etc, but to me, this just means having to use the brakes more rather than engine braking. Funny story, my brother in law used to have an old school Saab 96 which could switch between keeping the gear engaged or coasting when off the gas.....guess which mode he was in when this sucker had to help him push start his car?

[Mark@Abbey M/S 235]

Only issue with turning a car off on the coast is no engine braking on a manual car and as long as the car has electric power steering your be okay.

Interesting thread thou. Variable speed on a fixed drive SC I like the idea of very much like bleeding boost on a SC to control torque.

[nerdstrike 186]

15 hours ago, DanJ said:

The next thing for start/stop is "stop in drive", which is switching the engine off whilst your coasting, going down a long hill etc.

I'm confused. There have been high tech engines doing injector shut-off on coast since the nineties. There are also V8's that turn off half their cylinders in low power scenarios. I know the compression braking will slow the vehicle anyway, but it seems rather a desperate measure to combine coasting with a switched off engine. The energy needed to spin up the flywheel to idle is probably quite large compared with that saved by removing the engine braking.

[Nicebiscuit 655]

I'd just like the ability to bypass the s/c altogether. I like the idea of one, but don't want it helping gobble fuel when I'm tootling about on a light throttle. For that reason (and that alone) I can see me going down the turbo route with this car.

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[Rich 378]

11 hours ago, Keethos said:

Lol, I've always question why cars didn't just coast when off the gas but people kept on telling me it was because of safety and that you have to be in full control and if you're coasting you not in control etc, but to me, this just means having to use the brakes more rather than engine braking. Funny story, my brother in law used to have an old school Saab 96 which could switch between keeping the gear engaged or coasting when off the gas.....guess which mode he was in when this sucker had to help him push start his car?

Fuel injected engines cut fuelling on overrun (generally if you're off the gas and RPM is at least around 2k). So if you're rolling downhill in gear it will use no fuel, even though the engine is "running". This is probably why coasting has never been added, it doesn't really add much over just rolling in gear, other than increased brake wear.

[DanJ 374]

Its mostly more "cycle beating" by the OEMs, by moving the start/stop system to the "P2" location (between engine and gearbox) from the "P1" location (FEAD connected) then they can drive portions of the emissions cycles that aren't stationary with the engine off.

If you have a mild or full hybrid then switching the engine off does make a reasonable difference to the amount of energy that can be captured on deceleration and hence use less fuel.

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