HKS Supercharger Teardown

[DanJ 374]

Last week I had the opportunity to see inside an HKS supercharger, thought some of you would be interested in seeing the pictures. Happy to answer any questions about what each picture shows, there's some clever engineering in there but they're very simple, I'm sure HKS make plenty of profit on each of these that they sell!

Dan.

[Keethos 842]

Cool stuff, where did you get to see this?

[DanJ 374]

Cool stuff, where did you get to see this?

It was for a competitor teardown for a project at work that I'm Chief Engineer on, we make a variable ratio drive supercharger with our own traction epicyclic.

http://www.torotrak.com/products-partners/products/v-charge/

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[Keethos 842]

Nice......so you developing anything for the 86 then

[DanJ 374]

Not likely at the moment, there's not much point in having the variable ratio drive on performance applications, the real benefit is for multi-stage boosting which is where the car industry is heading for the next gen of engines (there's a few out there like this already but not many yet).

The principle is to have a large turbo to enable an aggressively downsized engine and use the variable supercharger for transient response until the turbo spools up, we're expecting to hit a nice to drive on the road 140kW/litre specific output eventually

Although that sounds like it would be great for the FA20 its a lot of boost so you would need a built engine for it to live. That's why it's targeted for the next gen of engines so they can bake in larger bearings, stronger rods etc from the get go!

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[Church 209]

I'd rather expect industry to have electric supercharging + electric generator turbine on exhaust as Next Big Thing. =widest possible tunability by ecu, =efficiency of turbo, =no lag of turbo-ing, =any boost possible at any rpms even lowest idle ones, =reasonable simplicity & cost, =rather simple extending of existing internal combustion engines with such (due no need for mechanical linkage between SC & generator). At least results & user experience in this thread about DIY electric SC kits makes me think so, with main limitations being only battery dump pack charge (that would be fixed with generator that would recycle otherwise wasted exhaust gases energy) and slow pace/long wait times for assembling these kits by this guy :).

[DanJ 374]

E-Boost (either 12V or 48V) is coming too but its unlikely to ever be adopted as a stand alone alternative to a turbo. It cannot deliver sustained boost without draining the battery and OEMs are not going to give up on recovering wasted energy going down the exhaust pipe, its just not feasible with the direction of current and future emissions regulations.

It is definitely a competitor to our system for multi-stage boosting applications though, on that I don't disagree!

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[DanJ 374]

I think turbos in their current form will remain the norm. You can't beat the efficiency of a mechanical shaft linking the turbine to the compressor when you compare it to all the efficiencies involved in getting the energy from an electric turbine to the battery (via power electronics with AC to DC conversion, DC voltage conditioning, then electrical to chemical energy in the battery) and then back again through the same efficiency chain to the electric compressor.

The best place to get energy to run an electric compressor from is regenerative braking, which has access to whole vehicle kinetic energy rather than just exhaust gas energy, and is available when the engine is in overrun fuel cutoff i.e. wasting very little extractable energy down the exhaust.

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[Church 209]

Yes, direct mechanical linkage of turbo will have less energy loss .. but such electric SC + electric turbo generator will still be more efficient then electric SC-only (that works fine even on linked in SC kit, with energy charge accumulation during normal driving, and limitations rising only during very long WOT driving), and turbo has several cons due that direct linkage, such as lag, for fixing which it needs much more complexity and costs rise (such as dual stage turbos, variable wing geometry, blow off valves), direct mechanical link also puts limitations on underbonnet space usage / turbo placement / exhaust routing configuration. Electric separate SC & generator will need none of such. Just cut in at any place on exhaust (probably closer to exit for lesser temps/more longetivity) & on intake.

[DanJ 374]

I think were close to having a heated agreement on most points!

Electric supercharger on its own is not viable, it will always have some other addition to the power train to capture the energy to drive it (belt ISG is probably the cheapest option).

I strongly doubt electric only compressors will come to road cars, combined electro-mechanical units are more likely but these still have significant challenges with the high speeds required for the electric machine elements.

I do agree that multi-stage turbos are a nightmare, that's why the industry is looking at single turbo with supercharger, be it electric or mechanically driven.

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[Keethos 842]

How cost effect is having a smaller but built engine with a multi stage turbo compared to just a simple big lump with a simple turbo?

[jarnojvv 2]

How cost effect is having a smaller but built engine with a multi stage turbo compared to just a simple big lump with a simple turbo?

Its not about cost, but about emissions.

[Nicebiscuit 655]

Fascinating stuff - good to hear from people with expertise.

If it's mainly about recovering wasted energy then, I can't see Turbos going anywhere. Huge win from a relatively simple device. (And has been for years - as a Saab fan I'd still say the 15 year old B234 motor in my 9-5 wipes the floor with the FA20 on every level, much as I love the Toyota in every other way)

But as for recovering other energy - if you gather surplus energy from regenerative braking say, what's the best thing to do with it. Does an electric supercharger make sense or better to just use the electric power direct via a motor in a hybrid configuration?

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[nerdstrike 186]

Curious idea with the variable supercharger! The industry is really throwing everything in to see what sticks:

1. small engine + turbo
2. v-charge + small engine + turbo
3. engine-electric hybrid (prius style)
4. electric-assisted petrol + turbo (torque filling)
5. electric only
6. petrol-assisted electric (range extender)
7. hydrogen fuel cells

[Rich 378]

31 minutes ago, Nicebiscuit said:

But as for recovering other energy - if you gather surplus energy from regenerative braking say, what's the best thing to do with it. Does an electric supercharger make sense or better to just use the electric power direct via a motor in a hybrid configuration?

My old car had regenerative braking and it was used to reduce alternator load and for start / stop AFAIK. I'm not sure you get enough from a road car to make much use of it for motive power in a non-hybrid vehicle.

[Church 209]

And electric supercharging can easily use energy from multiple sources - be it from generator turbine in exhaust, be it from regenerative braking, be it from main battery .. it's all electricity .. only caveat that it can only provide supercharged/turboed boost to internal combustion engine rising it's power/torque, not directly assisting turning wheels as in some hybrids.

Still it seems as better fitting in future petrolheads then hybrids/electric cars will. Somehow hearing about something as heretic as electric formulas in future makes me want to puke. Yes, most probably performance will be there, once storing electricity tech will get up to needed weight/capacity parameters .. but it won't pump any adrenaline in me like watching B group rally monsters or crazy turbo formulas with active fan downforce of past with shooting from turbo blow off valves. F-1 priuses, eek. :/

[kurosagi01 41]

The way you described what you're trying to aim kinda sounds like what VW done with their polo GTI and the 1.4 mk5 golf.

[Nicebiscuit 655]

Oh, I'm quite excited about the potential of hybrids. Borrowed an Auris and whilst not sporty in a million years I liked the power train - and very economical in town.

But at the other end of the spectrum look what Porsche and mclaren are up to...

Energy density just isn't there yet, but if it were, a hybrid GT86 would be right up my street. Especially if you could tootle to Sainsbury on battery power.

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[DanJ 374]

How cost effect is having a smaller but built engine with a multi stage turbo compared to just a simple big lump with a simple turbo?

Its not about cost, but about emissions.

You get some cost reduction on the downsizing if you're losing cylinders, changing the spec of something at the design stage has very little impact on the ultimate piece cost, the vast majority of the "sale price" is amortisation of tooling investment and the engineering program to design and then validate a new design.

That's why things like the HKS kit cost what they do, in relative terms sales volume is low to recoup the investment over.

Jarno is right that it's ultimately about emissions, all the OEMs are looking at the most cost effective way to meet the emissions legislation and all have a metric something like £/g of CO2 saved over the test cycle they're willing to pay. There are future fines coming in for every gram of CO2 an OEM's fleet average is over the target, and that target decreases in regular intervals.

They've all gone after and had most of the "low hanging fruit" (start stop is a con just to get good numbers on the test cycle for example, the real world benefit for most is tiny) so they're now having to look at more innovative solutions. Its impossible to aggressively downsize (or down speed) with a single turbo and get transient response that customers would accept, hence the trend towards multi-stage boosting.

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[Keethos 842]

True but as you just mentioned, OEM will need to find the most cost effect way to reduce the emissions, this solution can offer reduced emissions but is it cost effective enough? Chances are if it's feasible, costs would typically be offset to the buyers anyways. Start stops are usually paid extras aren't they? All interesting stuff, I'm kinda with Church on the whole full electric side, I'm sure they're a hoot to drive but without the noise there's no drama to the enjoyment of driving.

[DanJ 374]

The way you described what you're trying to aim kinda sounds like what VW done with their polo GTI and the 1.4 mk5 golf.

It is very similar with a few key differences. The VAG setup uses an Eaton TVS (very similar to the Cosworth kit for our cars) with a conventional turbo.

The amount of sound deadening kit they've had to put on it to have acceptable NVH is unbelievable, but they've achieved it AND patented how to do it so the other OEMs are blocked from that route (if they want it to be quiet, nothing stopping them from using an Eaton without the NVH kit).

The Eaton setup is run at a fixed gear ratio to the crank and to get acceptable boost at low engine speed this gear ratio is so high that you have to declutch it above a threshold engine speed.

Another impact of the fixed ratio is that it spends a lot of time bypassing air, which is all wasted energy.

So having a variable ratio drive (or completely decoupled in the case of e-boost) has significant advantages. Having a centrifugal compressor attached to this rather than a positive displacement pump then makes all the NVH issues go away, so no need for sound deadening.

Variable ratio is also highly desirable for managing NOx emissions, particularly in Diesels which have very poor control of the incoming air.

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[DanJ 374]

True but as you just mentioned, OEM will need to find the most cost effect way to reduce the emissions, this solution can offer reduced emissions but is it cost effective enough? Chances are if it's feasible, costs would typically be offset to the buyers anyways. Start stops are usually paid extras aren't they? All interesting stuff, I'm kinda with Church on the whole full electric side, I'm sure they're a hoot to drive but without the noise there's no drama to the enjoyment of driving.

Rest assured full electric is along way from being mainstream.

It definitely is all about cost/benefit at the end of the day.

Things like start/stop will be standard fit on most new cars soon (certainly in time for 2020 when the next step in emissions legislation comes in).

I'll stop now anyway and try to keep away from geeking out on the detailed engineering

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[Rich 378]

30 minutes ago, Keethos said:

True but as you just mentioned, OEM will need to find the most cost effect way to reduce the emissions, this solution can offer reduced emissions but is it cost effective enough? Chances are if it's feasible, costs would typically be offset to the buyers anyways. Start stops are usually paid extras aren't they? All interesting stuff, I'm kinda with Church on the whole full electric side, I'm sure they're a hoot to drive but without the noise there's no drama to the enjoyment of driving.

Start stops are standard fit on a lot of cars for reduced emissions, which plays into tax bands. I was somewhat surprised that the GT86 didn't have one actually. I'm not sure they make a huge difference in real world driving as mentioned, certainly this car is more efficient than either of my previous two cars, both of which has 2L turbocharged engines. That might be because it doesn't have a turbo to throw lots of air (and thus fuel) in when you boot it though.

[Keethos 842]

Whaaaaat.....don't do that, debate more MORE I SAY! My mate works for BorgWarner and he was trying to convince me to get one of their EFR Turbos or to consider electric chargers but not really looked into it and wouldn't know where to start. Buying the unit is one thing, pluming and tuning everything correctly is another right? How easy or difficult would this be?

[Keethos 842]

It's been a while since I've look at brand new cars so no idea now but when I last looked, it was often a paid extra which didn't work very well or caused dead battery's.