Twin Turbos

[Otispunkmeyer]

HoHoHo said:

Otispunkmeyer said:

aka_kerrly said:

Just to confuse things even more you also have cars like a Toyota MR2 which has a twin entry turbo which people often think means there are 2 turbos!!

Those really should be twin scroll... That's the volute or snail looking housing.

I think modern machining is able to produce better, more complex turbine and compressor wheels so they work over a great range of flow rates.

Add to that, variable inlet vane control and you make those wheels work over a further increased range. You want small, light wheels so that they spin up when you put your fit down. I think increasingly we'll see electric compressors which can spin to 70krpms in milliseconds, providing you instant response.

(Until everyone drives an EV of course)

Or the 61 plate 335i I had which had a big badge on to of the engine.................

TWIN TURBO POWER

WTF does that mean.........it means BMW went from two to one turbo from the previous to that engine but didn't want to upset the punters

Excellent. I didn't know BMW put stickers like that on their cars! I know Alpina stick a Bi-Turbo badge on there. And no it doesn't mean your turbo bats both ways haha!

[AW111]

HoHoHo said:

Or the 61 plate 335i I had which had a big badge on to of the engine.................

TWIN TURBO POWER

WTF does that mean.........it means BMW went from two to one turbo from the previous to that engine but didn't want to upset the punters

Bavarian Marketing wk?

[Alex C2]

HoHoHo said:

Or the 61 plate 335i I had which had a big badge on to of the engine.................

TWIN TURBO POWER

WTF does that mean.........it means BMW went from two to one turbo from the previous to that engine but didn't want to upset the punters

Close, but try again.

Twin Power = Twin Scroll

[HoHoHo]

Alex C2 said:

HoHoHo said:

Or the 61 plate 335i I had which had a big badge on to of the engine.................

TWIN TURBO POWER

WTF does that mean.........it means BMW went from two to one turbo from the previous to that engine but didn't want to upset the punters

Close, but try again.

Twin Power = Twin Scroll

Still not two turbos though I thought

[HappyMidget]

HoHoHo said:

Alex C2 said:

HoHoHo said:

Or the 61 plate 335i I had which had a big badge on to of the engine.................

TWIN TURBO POWER

WTF does that mean.........it means BMW went from two to one turbo from the previous to that engine but didn't want to upset the punters

Close, but try again.

Twin Power = Twin Scroll

Still not two turbos though I thought

Think of it as conjoined twins Almost two turbos, but not quite.

[HoHoHo]

HappyMidget said:

HoHoHo said:

Alex C2 said:

HoHoHo said:

Or the 61 plate 335i I had which had a big badge on to of the engine.................

TWIN TURBO POWER

WTF does that mean.........it means BMW went from two to one turbo from the previous to that engine but didn't want to upset the punters

Close, but try again.

Twin Power = Twin Scroll

Still not two turbos though I thought

Think of it as conjoined twins Almost two turbos, but not quite.

Ah, every day is a learning day

[Mike335i]

It actually says TWIN POWER TURBO, so actually it is accurate. It is a turbo with twin (as in two) power states, or 'scrolls'.

Funny how the order of words changes things.

[AW111]

Mike335i said:

It actually says TWIN POWER TURBO, so actually it is accurate. It is a turbo with twin (as in two) power states, or 'scrolls'.

Funny how the order of words changes things.

Does it have two exhaust turbine wheels, or one?

Edit :
Some googling shows it is a single turbo, with one exhaust turbine, but a twin entry scroll housing.
So one turbo, one power stage.

"Twin Power Turbo" is not a lie, because it doesn't really mean anything, but it implies two turbos, when there's only one.
Bavarian marketing WORKS!

Edited by AW111 on Monday 5th December 20:49

[HoHoHo]

AW111 said:

Mike335i said:

It actually says TWIN POWER TURBO, so actually it is accurate. It is a turbo with twin (as in two) power states, or 'scrolls'.

Funny how the order of words changes things.

Does it have two exhaust turbine wheels, or one?

Edit :
Some googling shows it is a single turbo, with one exhaust turbine, but a twin entry scroll housing.
So one turbo, one power stage.

"Twin Power Turbo" is not a lie, because it doesn't really mean anything, but it implies two turbos, when there's only one.
Bavarian marketing WORKS!

Edited by AW111 on Monday 5th December 20:49

So was I correct

[rayyan171]

toon10 said:

rayyan171 said:

Twin scroll turbocharges, again used by BMW, use one turbocharger only. The turbo exhaust gas flow port is split into two. The turbo equally pushes gases coming from cylinders 1, 2 and 3 and then from 4, 5, and 6 into the compressor. This in turn creates a parallel twin turbo effect. Normally with a single conventional turbo, the gases pressure decreases a bit as they collide with the other gases coming from the other cylinders, reducing the overall pressure. The twin scroll significantly decreases this decrease in pressure from the gases, and higher pressure results in better boost, better efficiency etc. which is why BMW use this now instead of conventional parallel twin turbos.

Lots of manufacturers have their needs, so it was much harder to apply them to NA cars, therefore turbos are very commonly used to meet the needs.

Hopefully this solves many questions, correct me if I am wrong.

Interesting insight. I have the twin scroll on my car and wasn't aware of the engineering behind the idea. I know BMW changed from the twin turbo setup to the single twin scroll one on my car but are there any other manufacturers using this setup and if not why? Seems to be a cheaper and better alternative to adding 2 turbos?

It definitely is a cheaper and better alternative to adding 2 turbos instead as it puts less pressure on the block and produces less emissions, boost is at the highest and most efficient pressure so that helps too. It also saves on fuel as well.

Other manufacturers find it difficult to adapt because of the significant change in internals when changing from twin turbo to twin scroll. But, ford is using it and lexus too, so I am guessing other manufacturers will eventually catch on.

[Mr Tidy]

Otispunkmeyer said:

Excellent. I didn't know BMW put stickers like that on their cars! I know Alpina stick a Bi-Turbo badge on there. And no it doesn't mean your turbo bats both ways haha!

Assuming you are referring to the D3 I think that is pretty much a mix and match job, as in a twin-turbo 2 litre diesel put into a 3 Series shell when BMW never offered one (just the 325d, 330d and 335d which were all 3 litre turbo-diesels - early 335ds were twin-turbo IIRC).

But BMW did offer the 2 litre sequential twin-turbo in the 1 Series and it was pretty impressive (I had a 123d for 6+ years) - but it was still a diesel! Now I have experienced the N52 naturally aspirated 3 litre Straight 6 petrol I realise I should have bought a 130i!

[300bhp/ton]

V8RX7 said:

Nanook said:

BMW 335s and old straight 6 Skylines (just 2 examples) have one turbo per 3 cylinders, the turbochargers are the same size.

I don't understand what the advantage is of this type, 3 cylinders driving a small turbo or 6 cylinders driving a large turbo would seem to be the same in performance / spool terms.

I presume there must be a benefit because there are cost, weight, complexity penalties having two instead of one.

Obviously on a V engine there are obvious "layout" benefits to twin turbos.

I inertia would play a part. Two smaller turbo's should be less laggy. And as a rule a smaller turbo will work better at lower rpm. So in todays market fast spooling turbos for a fat low and mid range seem all the rage. I would 'guess' as I've not seen a dyno plot, but these small turbo's probably nose over well before the red line.

A larger single turbo, despite being fed by 6 cylinders would likely result in more lag (when you lift off the throttle and reapply, rather than boost threshold).

I would think there are also packaging benefits to two smaller turbos as well. Even on an S6.

[V8RX7]

300bhp/ton said:

V8RX7 said:

Nanook said:

BMW 335s and old straight 6 Skylines (just 2 examples) have one turbo per 3 cylinders, the turbochargers are the same size.

I don't understand what the advantage is of this type, 3 cylinders driving a small turbo or 6 cylinders driving a large turbo would seem to be the same in performance / spool terms.

I presume there must be a benefit because there are cost, weight, complexity penalties having two instead of one.

Obviously on a V engine there are obvious "layout" benefits to twin turbos.

I inertia would play a part. Two smaller turbo's should be less laggy. And as a rule a smaller turbo will work better at lower rpm. So in todays market fast spooling turbos for a fat low and mid range seem all the rage. I would 'guess' as I've not seen a dyno plot, but these small turbo's probably nose over well before the red line.

A larger single turbo, despite being fed by 6 cylinders would likely result in more lag (when you lift off the throttle and reapply, rather than boost threshold).

I would think there are also packaging benefits to two smaller turbos as well. Even on an S6.

It was answered here:

Max_Torque said:

If we are talking about purely parallel turbocharging and we take a single turbocharger of "size = 1", then take two turbos of "size = 0.5". The total turbo size is the same in both cases, but the "twin" set up has more lag! Because despite what you might think, turbo inertia does not scale linearly with size ( because there are bits of the shaft / wheels that are spinning that don't contribute to energy capture or release (the shaft, wheel centres etc)) And as each turbo has half the flow to drive it, if you do nothing else but fit "twin" turbo's you gain nothing.

So why bother you may ask, well there are 2 reasons:

1) You can connect those turbo's to optimum cylinders in terms of firing order and hence capture more of the EVO blow down pulse, which does reduce boost threshold

and

2) You can generally get a lower volume of exhaust manifold between turbine and exhaust valve, so there is less heat loss and the pressure pulses are less dissipated by the volume of the exhaust manifold - again, lower boost threshold / lag

[Wills2]

Welshbeef said:

Wills2 said:

McVities said:

popeyewhite said:

Warby80 said:

The new Audi Sq7 has a 4 litre v8 with sequential turbos and an electrically driven compressor aswell…

664lb ft at 1000rpm

Tuned M5s (twin turbo) and E63s (biturbo) happily run c.800lbft or more!

Do they run those large torque figures from idle rpm too?

Why would you want that unless you're ploughing a field or towing the space shuttle?

I guess you could ask Tesla P90D owners the same question then they destroy you off the line. A Q7 is a family bus so big power little effort to access is a winning combo - who cares what it does or doesn't do on a track as it would never be used as such a vehicle

Where do you get this rubbish from? Destroy? What is it a type 22 frigate? Family bus? That'll be doing 40mph on the way to the shops?

You really are an arse....anyway back to electric turbos...

[anonymous-user]

rayyan171 said:

It definitely is a cheaper and better alternative to adding 2 turbos instead as it puts less pressure on the block and produces less emissions, boost is at the highest and most efficient pressure so that helps too. It also saves on fuel as well.

Other manufacturers find it difficult to adapt because of the significant change in internals when changing from twin turbo to twin scroll. But, ford is using it and lexus too, so I am guessing other manufacturers will eventually catch on.

Could you please elborate a little more on the "significant change in internals" required for a twin scroll setup, and why they are required? I was under the impression that it is all in manifold and turbo design?

I can think of a few aftermarket applications where twin scroll turbos have been retrofitted to cars that used traditional turbos, through the use of specifically designed manifolds, seemingly with no issues.

Edited by 279 on Wednesday 7th December 02:30

[Welshbeef]

Wills2 said:

Where do you get this rubbish from? Destroy? What is it a type 22 frigate? Family bus? That'll be doing 40mph on the way to the shops?

You really are an arse....anyway back to electric turbos...

Pack it in you scrumptious chap you.

[Welshbeef]

Mr Tidy said:

Assuming you are referring to the D3 I think that is pretty much a mix and match job, as in a twin-turbo 2 litre diesel put into a 3 Series shell when BMW never offered one (just the 325d, 330d and 335d which were all 3 litre turbo-diesels - early 335ds were twin-turbo IIRC).

But BMW did offer the 2 litre sequential twin-turbo in the 1 Series and it was pretty impressive (I had a 123d for 6+ years) - but it was still a diesel! Now I have experienced the N52 naturally aspirated 3 litre Straight 6 petrol I realise I should have bought a 130i!

All x35ds are two Turbos but sequential Turbos not twin scroll

[AW111]

279 said:

rayyan171 said:

It definitely is a cheaper and better alternative to adding 2 turbos instead as it puts less pressure on the block and produces less emissions, boost is at the highest and most efficient pressure so that helps too. It also saves on fuel as well.

Other manufacturers find it difficult to adapt because of the significant change in internals when changing from twin turbo to twin scroll. But, ford is using it and lexus too, so I am guessing other manufacturers will eventually catch on.

Could you please elborate a little more on the "significant change in internals" required for a twin scroll setup, and why they are required? I was under the impression that it is all in manifold and turbo design?

I can think of a few aftermarket applications where twin scroll turbos have been retrofitted to cars that used traditional turbos, through the use of specifically designed manifolds, seemingly with no issues.

Edited by 279 on Wednesday 7th December 02:30

I'm trying to work out what "boost is at the highest and most efficient pressure" means .

[Steven_RW]

https://www.youtube.com/watch?v=45ZODU3XWlg

This looks at a twin turbo setup vs a single turbo setup. Quite interesting for all those who have expressed opinions up to page 2 (as far as I made it during breakfast).

Regarding two turbos. The sequential one changes the exhaust gas flow away from the smaller one, as it becomes a bottlneck at higher rpm.

Bigger turbos are basically better for higher flow higher rpm, but to take more exhaust gas (cc's or RPM) to get on boost.

Twin turbo in the way that term is being used here would mean both matched turbos work equally and one does not have the exhaust gas diverted away as RPM rises.

I am building a compound system where the air intake of the little turbo is actually fed from the outlet of the bigger turbo. So if the smaller turbo produces a boost factor of 1 to 2 then it will multiply whatever boost it receives from the bigger turbo also by a factor of 2.

Aim is for smaller turbo to come in early produce boost and therefore more exhaust gas which allows the bigger one to spool up much faster than if it was working on a 1.6l engine in isolation.

RW

[V8RX7]

Steven_RW said:

I am building a compound system where the air intake of the little turbo is actually fed from the outlet of the bigger turbo.

So if the smaller turbo produces a boost factor of 1 to 2 then it will multiply whatever boost it receives from the bigger turbo also by a factor of 2.

Aim is for smaller turbo to come in early produce boost and therefore more exhaust gas which allows the bigger one to spool up much faster than if it was working on a 1.6l engine in isolation.

So you're effectively building a sequential turbo (one feeding another) but backwards to the norm as you're mounting the large one first.

Surely that is the worst of both worlds - the smaller one is initially restricted by the larger one, then once it gets going the larger one's exhaust is restricted by the smaller one.