Hi,

Just trying to pick brains here. I was reading on Pistonheads that BMW is bringing out a 3.2 tri-turbo petrol for the next M3 and a tri-turbo.

Whilst I understand that the Veyron has 4 biturbos (8?) and the older EB110 has 4 turbos, and this is to squish out as much power as possible from a technologically advanced engine, given weight etc.

But what I fail to understand is by fitting so many turbos, ie quite a lot of boost, the cylinder head would need to be reinforced, which means added weight or high specification materials, which cost a lot.

I have no doubt if the other components are strong enough, it could with stand much more boost, but I don't see the reason for introducing a 3.2 tri-turbo petrol engine when the equivalent 5.0 V8 from the M5 would push out similar horsepower?

Apart from better fuel consumption at low revs, what are the reasons??

3 sounds a bit weird, as it doesn't divide by the numbers of cylinders. Normally in a twin turbo v8, there would be one turbo on each half of the vee.

As for the 3.2 tri-turbo vs 5.0 V8, it's the same comparison as the 1.2 TSI engine, vs NA 2.0L engine. Similar performance from less CC's, meaning better consumption etc.

Smaller, lighter turbines spool up faster. You're not necessarily going to evolve more boost though, because that's a function of the total air mass moved by all turbines on the engine, so 1 turbine that moves X cfm at Y PSI on $engine will give the same peak pressure as 3 turbines that move X/3 cfm each at Y PSI on $engine.

one of the turbos on that new bmw engine is electrically driven whilst the others are exhaust gas driven.

from what ive read about it the function is basically the same as the supercharger on the 1.4tsi engine. giving boost low down while the oversized turbos spool up to pressure.

Maybe they will have a sequential turbo 1st and then 2 parallel turbos , to spread the power, I would imagine the emissions would be a lot less than the v8 , company car tax is a big deal for business users , and as you have stated ,better fuel cunsumption, but not so good a soundtrack :yes:

Brill thanks, so it spools up quicker (esp with the twincharge sort of arrangement) to make it drive like a large N/A engine, when in fact they could just use the basis of their V8 to save cost.

I guess its really down to consumption and emmision then.... Oh well

I seem to remember the V12 Mercs used to be able to run on 2 cylinders to reduce emmision and consumption, could they not do that, or does EU decide that is cheating and have to test the engine when all cylinders are running?

they may even be using the first electric turbo to spool up the other two in a sequential bi-turbo with three turbos type of arrangement. makes sense in my head haha.

Its all to do with providing boost across the whole rev range.

IIRC Cummins sell a 78 Litre V16 diesel with 12

Its all to do with providing boost across the whole rev range.

IIRC Cummins sell a 78 Litre V16 diesel with 12

Its all to do with providing boost across the whole rev range.

IIRC Cummins sell a 78 Litre V16 diesel with 12

Wow!! Reminds me of this:

Not quite 78 litres, but it's a 29L V24 diesel with what looks like 8 superchargers. Imagine the torque on that thing.

That could pull a train

Out of interest, why does everyone go with Turbos, not Superchargers?

Is there some really obvious downside to Superchargers? or is it just a case that Turbos are much cheaper?

Shame its not real!

Edited 18 August, 201114 yr by My_Yeti

Out of interest, why does everyone go with Turbos, not Superchargers?

Is there some really obvious downside to Superchargers? or is it just a case that Turbos are much cheaper?

I actually think superchargers are better as they provide instantaneous boost, but it normally yield less power increase. However, I am under the impression that since they are not driven by exhaust gas, it actually make the consumption worse? I am sure someone who is more mechanically minded could ans your question.

Out of interest, why does everyone go with Turbos, not Superchargers?

Is there some really obvious downside to Superchargers? or is it just a case that Turbos are much cheaper?

Its all down to boost and losses - superchargers provide instant response but the mechanical losses can be high and they are less thermally efficient - turbos have less mechanical losses and better thermal efficiency but poorer initial response. Superchargers can also be slightly more complex.

Eaton have recently intorduced some new roots type supercharges which have mechnical losses and thermal efficiency that are more comparable to turbos and they are already in use in some Jaguars.

Roots type blowers have also been used on MX5's for years as well, both m45 and m62 types.

From experience of the 335i engine, the power delivery from the little n large turbocharged engine is smooth as a baby's buttocks. You cannot discern any turbo lag at all. This is a major factor in Bmw's strategy, as they previously fiercely resisted turbos in the past due to the whiplash factor. (yes, I'm aware they have used turbos before)

Out of interest, why does everyone go with Turbos, not Superchargers?

Is there some really obvious downside to Superchargers? or is it just a case that Turbos are much cheaper?

<specialist subject the b1eeding obvious> Turbochargers are driven by the otherwise wasted energy in the exhaust gases, so they're "free power". </end>

Superchargers are driven by the engine, so they absorb power that could be pushing you down the road; as much as 15% in the case of a "Roots type", like the GMC 4-71 and 6-71 units that you often see on American V8s such as the black Dodge Charger driven by Vin Diesel in the original "The Fast and The Furious".

I've seen the claims that the latest Eaton units are "about as efficient as a turbo", and don't believe them. Well, ok, I think the claimants are being economical with the truth: The phrase is probably true in terms of the efficiency of the compressor itself, but that power is taken from the engine crankshaft rather than the exhaust gas flow.

<specialist subject the b1eeding obvious> Turbochargers are driven by the otherwise wasted energy in the exhaust gases, so they're "free power". </end>

Superchargers are driven by the engine, so they absorb power that could be pushing you down the road; as much as 15% in the case of a "Roots type", like the GMC 4-71 and 6-71 units that you often see on American V8s such as the black Dodge Charger driven by Vin Diesel in the original "The Fast and The Furious".

I've seen the claims that the latest Eaton units are "about as efficient as a turbo", and don't believe them. Well, ok, I think the claimants are being economical with the truth: The phrase is probably true in terms of the efficiency of the compressor itself, but that power is taken from the engine crankshaft rather than the exhaust gas flow.

Hiya Ken,

Turbo's aren't really 'free power' though are they - they put a damn great turbine in the exhaust tract and thus create backpressure that needs to be overcome so they do themsleves absorb power that could otherwise be pushing you down the road. Until recently thy absorbed les power than superchargers but things are getting much closer now in terms of losses.

Just another view, since the supercharger runs on a belt from the engine, there is obviously loss form the engine to generaate that power, much like fans in older cars.

Obviously there is a dissipitation of energy driving the fan belt, therefore electric fans were introduced. Is there an electric super charger out there? (exc. those ebay cheap ones)

Is there an electric super charger out there? (exc. those ebay cheap ones)

In theory that works. In practice, you would need a lot of electrical power to be able to spin the turbine fast enough to provide boost across the whole rev range. More electrical power than the engine can generate in fact.

Lots more.

Imagine filling your boot with batteries just to power the turbine. Should last it an hour maybe before they need recharging.

Those ones on ebay will provide no measurable power at all, they are nowhere near powerful enough.

Those ones on ebay will provide no measurable power at all, they are nowhere near powerful enough.

Shut up, I thought they were the ****, thats what the advert said

I owned a 123D BMW and can vouch for the brilliance of at least having 2 turbos Although the car probably had a similar power/weight/Torque-thingie ratio to a remapped Furby vRS, it picked up a lot quicker and seemed slightly quicker overall and at any revs (especially low revs). You could feel the overlap bit of the 2 turbos delivery, but only once you'd had the car for a fair while and had got used to it's nuances - if you see what I mean. I guess if BMW say they can build a tri-turbo then they will deliver a pretty good engine. obviously not as good or as fast as a 2.0 petrol Furby, but not far off. I hope BMW will do an uprated version of the 123D in their new 1 series

Shut up, I thought they were the ****, thats what the advert said

just goes to prove it's very easy to make money out of idiots.

Sequential turbocharging has been around quite a while. Using 3 is unusual, I'm interested to see how it works exactly, but BMW obviously think it's a good thing, lets see what it does

I'm just waiting for car manufacturers to start usign Hybrid turbos. An exhaust turbine charges a battery or capacitor, which is then used to drive a motor which drives a compressor.

The good thing about it is you can use the energy stored in the battery to drive the compressor even when the turbine isn't going fast enough to provide any boost, and you can cruise round with no boost at all to charge the battery back up. Lagless turbo

http://en.wikipedia.org/wiki/Hybrid_turbocharger

Edited 20 August, 201114 yr by rk696