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      07-02-2013, 02:57 PM   #111
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M3/M4 N-Ring time is below 7:40 min.
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      07-02-2013, 02:58 PM   #112
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M3/M4 N-Ring time is below 7:40 min.
BEAST mode. they just said everyone shut up.
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      07-02-2013, 03:55 PM   #113
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Originally Posted by NISFAN View Post
Apologies for not being clear, I am talking about multi turbo systems on a single bank, like the BMW tri turbo inline 6. These systems have complex plumbing systems which lead to in-efficiencies.
Please explain the in-efficiencies that is connected with the tri-turbo system in the M550d engine. It seems to me that the advantages must have been greater than the disadvantages since BMW has chosen this concept?

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Originally Posted by NISFAN View Post
Yes turbo's have lag, but no different to the NA engine that has lag from idle to redline, as it never experiences the torque wave produced by FI.
You are just kidding, right ?

Renault's F1 engine department clearly doesn't agree with your statement anyway...

Lag and "torque wave" are two very different things. A NA engine will, for all intents and purposes, have instant torque delivery. When opening the throttle there will be, within milliseconds, a delivery of 100% of the available torque at that rpm and throttle opening.

A turbo engine will have the same, millisecond, delay before it delivers the unboosted maximum torque. When the first combustions at that level have taken place, the extra amount of exhaust will come into the exhaust manifold and start the process of spooling up the turbo. Depending on the operating stage of the turbo, this spooling up process might have to include first stopping the process of spooling down (turbo is loosing rpm's), then starting to accelerate the turbo up to it's maximum rpm and boost for that engine rapm and throttle opening. The turbo's compressor side also has to start the process of compressing the air, routing it through the intercooler and the necessarily longer intake tubing before the compressed air reaches the intake manifold and then enters the engine. Just the extra volume and length of the intake side of a turbo engine MUST produce a delay between throttle input and power delivery. Hence why even on a F1 engine with a motor to spool up and down the turbo, the manufacturer states that they cannot get as rapid response as a NA engine. By design, a turbo'd engine can't have as fast response as a NA engine.

A turbo engine will, a few milliseconds after throttle opening, only deliver a certain percentage of it's maximum power delivery for that rpm and throttle opening. That percentage depends on how much of it's power is made under boost. The higher the boost, the higher the percentage of power is made under boost. A engine that has a boost pressure of 0,5BAR (low boost) will typically make around say 40-50% more power under boost than it does without boost.

So, a turbo engine that boosts at 0,5BAR will only deliver 2/3rds (66%) of it's maximum power (at that rpm) a few milliseconds after the throttle has been opened fully. It then takes the added time of completing the combustions which creates the exhaust gases needed for spooling up the turbo(s). Then the turbo starts generating boost, delivering the air through the intercooler and intake plumbing before entering the intake manifold and finally the engine. That is turbo-lag my friend and is not remotely comparable to a NA engine.

Yes, a turbo engine will deliver more torque than a similarly sized NA engine. But where the NA engine delivers 100% of it's available power just a few milliseconds after throttle input, a turbo engine will only deliver maybe 50-60% of the available power in that same time frame, and then you have a delay before the turbo has reached max boost and you have 100%. It's kind of like a two stage power delivery. As explained above, it takes added time to reach 100%. There is currently no way around this, not even the clever F1 engineers have been able to eradicate it completely...

A NA engine cannot have lag from idle to redline, it constantly delivers 100% of available power at any given rpm and throttle opening. A turbo engine cannot, and does not, replicate this quality. Not even next years F1 engines!

And, just to reiterate, I love the torque wave a turbo engine delivers. It's addictive and much more useable in daily driving than a high revving NA engine that needs high rpms to deliver the goods.

And BTW, the beauty of the MGU-H unit is that it can start spooling up the turbo at the instant the throttle is opened. The turbo doesn't have to wait for the exhaust gases to start the spooling up process. This saves some time and boost production starts allmost immediately. Obviously not instantly as the compressor side has to compress the air and then flow it through the intercooler etc. But at least the turbo can respond immediately to throttle input The delay (lag) on the exhaust side of the turbo has been eliminated/minimized, it's now the compressor side of the turbo that is the cause of delay (as the turbo's compressor side cannot go from 0BAR boost pressure to 3,5BAR immediately. Air is compressible (unlike most fluids) and it therefor takes time to build pressure as more volume of air is needed to fill up all tubing/intercoolers etc before the desired pressure can be reached. The turbo has to pump air to build pressure, which takes time).

Last edited by Boss330; 07-02-2013 at 04:15 PM.
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      07-02-2013, 05:43 PM   #114
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Quote:
Originally Posted by Boss330 View Post
Please explain the in-efficiencies that is connected with the tri-turbo system in the M550d engine. It seems to me that the advantages must have been greater than the disadvantages since BMW has chosen this concept?
If your goal is to reduce boost threshold to very low revs, without compromising top end power, then yes a tri turbo like M550d is a valid solution. However, the additional plumbing adds restriction to overall system, which adds in-efficiencies.



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Originally Posted by Boss330 View Post
You are just kidding, right ?

Renault's F1 engine department clearly doesn't agree with your statement anyway...

Lag and "torque wave" are two very different things. A NA engine will, for all intents and purposes, have instant torque delivery. When opening the throttle there will be, within milliseconds, a delivery of 100% of the available torque at that rpm and throttle opening.

A turbo engine will have the same, millisecond, delay before it delivers the unboosted maximum torque. When the first combustions at that level have taken place, the extra amount of exhaust will come into the exhaust manifold and start the process of spooling up the turbo. Depending on the operating stage of the turbo, this spooling up process might have to include first stopping the process of spooling down (turbo is loosing rpm's), then starting to accelerate the turbo up to it's maximum rpm and boost for that engine rapm and throttle opening. The turbo's compressor side also has to start the process of compressing the air, routing it through the intercooler and the necessarily longer intake tubing before the compressed air reaches the intake manifold and then enters the engine. Just the extra volume and length of the intake side of a turbo engine MUST produce a delay between throttle input and power delivery. Hence why even on a F1 engine with a motor to spool up and down the turbo, the manufacturer states that they cannot get as rapid response as a NA engine. By design, a turbo'd engine can't have as fast response as a NA engine.

A turbo engine will, a few milliseconds after throttle opening, only deliver a certain percentage of it's maximum power delivery for that rpm and throttle opening. That percentage depends on how much of it's power is made under boost. The higher the boost, the higher the percentage of power is made under boost. A engine that has a boost pressure of 0,5BAR (low boost) will typically make around say 40-50% more power under boost than it does without boost.

So, a turbo engine that boosts at 0,5BAR will only deliver 2/3rds (66%) of it's maximum power (at that rpm) a few milliseconds after the throttle has been opened fully. It then takes the added time of completing the combustions which creates the exhaust gases needed for spooling up the turbo(s). Then the turbo starts generating boost, delivering the air through the intercooler and intake plumbing before entering the intake manifold and finally the engine. That is turbo-lag my friend and is not remotely comparable to a NA engine.

Yes, a turbo engine will deliver more torque than a similarly sized NA engine. But where the NA engine delivers 100% of it's available power just a few milliseconds after throttle input, a turbo engine will only deliver maybe 50-60% of the available power in that same time frame, and then you have a delay before the turbo has reached max boost and you have 100%. It's kind of like a two stage power delivery. As explained above, it takes added time to reach 100%. There is currently no way around this, not even the clever F1 engineers have been able to eradicate it completely...

A NA engine cannot have lag from idle to redline, it constantly delivers 100% of available power at any given rpm and throttle opening. A turbo engine cannot, and does not, replicate this quality. Not even next years F1 engines!

And, just to reiterate, I love the torque wave a turbo engine delivers. It's addictive and much more useable in daily driving than a high revving NA engine that needs high rpms to deliver the goods.

And BTW, the beauty of the MGU-H unit is that it can start spooling up the turbo at the instant the throttle is opened. The turbo doesn't have to wait for the exhaust gases to start the spooling up process. This saves some time and boost production starts allmost immediately. Obviously not instantly as the compressor side has to compress the air and then flow it through the intercooler etc. But at least the turbo can respond immediately to throttle input The delay (lag) on the exhaust side of the turbo has been eliminated/minimized, it's now the compressor side of the turbo that is the cause of delay (as the turbo's compressor side cannot go from 0BAR boost pressure to 3,5BAR immediately. Air is compressible (unlike most fluids) and it therefor takes time to build pressure as more volume of air is needed to fill up all tubing/intercoolers etc before the desired pressure can be reached. The turbo has to pump air to build pressure, which takes time).
Regarding the NA being smitten with lag all the way to redline is not difficult to understand. I'll explain....

Lets take an S65 type engine, and add a turbo charger system to it. If we do it right, even if we disconnect the wastegates so no boost is ever achieved, it still runs like an NA s65, all the way through the redline. Anyone driving this car not knowing there are turbo's attached to the engine, would comment on it feeling exactly like an NA s65.

Now we connect up the waste gates allowing the engine to build boost. All of a sudden there is 'lag' right? Well not comparing it the the NA s65, the turbo doesn't make things any worse than before, the torque curve compared to an NA version is identical.....but yes there is a delay before an even greater hit of torque takes place.

Comparing a small displacement turbo engine with a similar power but larger NA engine is when you notice the lower off boost torque.

You do correctly paint the picture of lag, but lets just visit some factors....

A turbo is a small device capable of accelerating very quickly in the right conditions. It is an air pump. When boost pressure in the inlet tract is low, you are powering a device with no load on it, this allows it to spool ridiculously fast.

Secondly, common myth is that a turbo has to be at 140,000+ rpm before it makes any boost. Totally incorrect, it depends on the Turbo airflow charts, compressor sizes, etc, however, more commonly the truth is they can start producing positive boost at half those revs. Now you might think that 70-80k revs is still high enough to take time to reach? Not really, the turbo is never stationary, even at IC engine idle it rotates at a few thousand rpm (no load on the pump remember). When WOT is reached, the energy going through the turbo increases very rapidly. Think 335i producing full torque from 1200rpm. This indicates that full controlled boost is reached by 1,200 engine revs.
that doesn't leave much delay for lag, and in fact I would be surprised if the turbo was even below boost threshold at idle. The higher the IC engine is above boost threshold, the lower the lag due to the high energy in the exhaust. A 335i will require waste gate opening from as little as 1200rpm to vent excess exhaust energy.

In summary, yes lag exists, but is grossly over exaggerated in modern systems. You might get a 0.25 second delay before full torque is achieved for the revs, compensated for by increased torque shortly after.

Coming back to F1, in the 80's turbo lag was massive, lasting seconds. But remember this, they realised that pumping enough air volume at the mandatory blow off valve, overloaded it in such a way that you could boost the engine to higher pressures than IIRC the 2 bar blow off valve allowed. This means the turbo was grossly oversized for the application. They used to run at something like 5 bar. That will not be the case for modern F1.

Last little point on competition, there isn't a single race class where (when allowed) a turbo charged engine is not the fastest type. i.e. there are no race series where NA rules over Turbo.
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      07-02-2013, 05:47 PM   #115
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Quote:
Originally Posted by Boss330 View Post
...
Yes, a turbo engine will deliver more torque than a similarly sized NA engine. But where the NA engine delivers 100% of it's available power just a few milliseconds after throttle input, a turbo engine will only deliver maybe 50-60% of the available power in that same time frame, and then you have a delay before the turbo has reached max boost and you have 100%. It's kind of like a two stage power delivery. As explained above, it takes added time to reach 100%. There is currently no way around this, not even the clever F1 engineers have been able to eradicate it completely...

A NA engine cannot have lag from idle to redline, it constantly delivers 100% of available power at any given rpm and throttle opening. A turbo engine cannot, and does not, replicate this quality. Not even next years F1 engines!
Excellent post.

NISFAN continues to delude himself with his "privileged understanding" of turbo lag which clearly only represents a very odd apples to oranges comparison of an given engine with and without a turbo system. I think I've given up but thanks for carrying the torch here...
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      07-02-2013, 05:54 PM   #116
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Quote:
Originally Posted by NISFAN View Post
You do correctly paint the picture of lag, but lets just visit some factors....
Finally a concession.

In short, because people exaggerate the severity of turbo lag in modern turbo engines and because turbo engines are successful in racing (and likely simply due to your preferences and bias), you felt you needed your own little private definition of turbo lag. Now confronted with a detailed explanation completely consistent with anyone's common understanding of turbo lag you finally yield.

OK, time to move along now...

Here is hoping that BMW are able to achieve an engine for the M3/M4 with substantially less turbo lag engine than those they currently have on the market. I think very likely they will.
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      07-02-2013, 05:58 PM   #117
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Excellent post.

NISFAN continues to delude himself with his "privileged understanding" of turbo lag which clearly only represents a very odd apples to oranges comparison of an given engine with and without a turbo system. I think I've given up but thanks for carrying the torch here...
I have also stated there isn't one competitive event where NA trumps Turbo, even uphill races on tight winding narrow roads where surely lag would render the turbo useless? Surely Lag is that bad right?

In fact, typically turbo's are written out of the rule books because they have a seemingly unfair advantage. The original E30 M3's reason for being was cut short due to turbo charged engines. It was designed and bred to be a competitive race car, cut down by others 'going turbo'.....ha ha......oh the irony.
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      07-02-2013, 07:06 PM   #118
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      07-02-2013, 07:08 PM   #119
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how do you jump from talking about lag and then talking about turbos making more power? i dont think anyone argues against turbos making more power. now that is just plain stupidity.

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      07-02-2013, 07:23 PM   #120
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BEAST mode. they just said everyone shut up.
No one is doubting the new car is going to be a beast, again its about using different style of engine.

if track times is all your car about cool... thats not me though. i never base my car purchase off a track time.
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      07-02-2013, 08:59 PM   #121
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^^ another E92 M owner. i'm seeing a trend in these threads lol..
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      07-02-2013, 09:40 PM   #122
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^^ another E92 M owner. i'm seeing a trend in these threads lol..
and what a non e92 m owner you are?

honestly though, i wouldn't expect you do understand what some people love about the engine.
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      07-03-2013, 12:14 AM   #123
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Quote:
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Originally Posted by pkim1079 View Post
BEAST mode. they just said everyone shut up.
No one is doubting the new car is going to be a beast, again its about using different style of engine.

if track times is all your car about cool... thats not me though. i never base my car purchase off a track time.
I was just commenting on what it did to the competition. I drive an e90 m3.

And about all the turbo lag stuff in here. I dont need to get technical. I just got back from dinner driving my gf's 135i and you can really feel the lag and throttle response is not immediate. For example you press down a bit on the gas and if you keep it there at the same pedal position, it will do nothing and then all of a sudden lurk forward.

I dont buy my cars based on a track time but i do buy a car that can do daily and track duty!
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      07-03-2013, 02:55 AM   #124
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Quote:
Originally Posted by NISFAN View Post
If your goal is to reduce boost threshold to very low revs, without compromising top end power, then yes a tri turbo like M550d is a valid solution. However, the additional plumbing adds restriction to overall system, which adds in-efficiencies.


BMW's object was obviously to design a engine concept that creates boost through the entire rev range. So a very efficient design for what it is supposed to do. It would not be suited for a F1 engine, but neither was it intended to be... Additional plumbing don't necessarily mean added restrictions, and remember that not only volume but also exhaust speed and continuity are vital factors in the efficiency of a turbo system. Which part of the additional plumbing on the M550d do you suggest adds in-efficiencies?

Regarding the NA being smitten with lag all the way to redline is not difficult to understand. I'll explain....

Can't find any explanation of what you call lag on a NA engine below... Unless you are saying that a NA engine's lag is defined as the difference between it's NA power delivery, and it's theoretical power deliver IF it was torbocharged??? By that definition, any engine has lag, even a turbocharged engine, as it's, theoretically, allways possible to have more boost. But I have never heard ANYONE calling that "lag".

Lets take an S65 type engine, and add a turbo charger system to it. If we do it right, even if we disconnect the wastegates so no boost is ever achieved, it still runs like an NA s65, all the way through the redline. Anyone driving this car not knowing there are turbo's attached to the engine, would comment on it feeling exactly like an NA s65.

Now we connect up the waste gates allowing the engine to build boost. All of a sudden there is 'lag' right? Well not comparing it the the NA s65, the turbo doesn't make things any worse than before, the torque curve compared to an NA version is identical.....but yes there is a delay before an even greater hit of torque takes place.

You have just descibed what is known as "turbo-lag". Yes, a turbo engine produces more power (no one is arguing against that), but that extra power isn't instantly available.

Comparing a small displacement turbo engine with a similar power but larger NA engine is when you notice the lower off boost torque.

You do correctly paint the picture of lag, but lets just visit some factors....

A turbo is a small device capable of accelerating very quickly in the right conditions. It is an air pump. When boost pressure in the inlet tract is low, you are powering a device with no load on it, this allows it to spool ridiculously fast.

Yes, it spools up fast, but once there is pressure build up it meets resistance. And regardless, it takes time to build pressure. Atmospheric pressure is instantly available...

Secondly, common myth is that a turbo has to be at 140,000+ rpm before it makes any boost. Totally incorrect, it depends on the Turbo airflow charts, compressor sizes, etc, however, more commonly the truth is they can start producing positive boost at half those revs. Now you might think that 70-80k revs is still high enough to take time to reach? Not really, the turbo is never stationary, even at IC engine idle it rotates at a few thousand rpm (no load on the pump remember). When WOT is reached, the energy going through the turbo increases very rapidly. Think 335i producing full torque from 1200rpm. This indicates that full controlled boost is reached by 1,200 engine revs.
that doesn't leave much delay for lag, and in fact I would be surprised if the turbo was even below boost threshold at idle. The higher the IC engine is above boost threshold, the lower the lag due to the high energy in the exhaust. A 335i will require waste gate opening from as little as 1200rpm to vent excess exhaust energy.

In summary, yes lag exists, but is grossly over exaggerated in modern systems. You might get a 0.25 second delay before full torque is achieved for the revs, compensated for by increased torque shortly after.

I have never heard about anyone (with basic knowledge) that believes a turbo has to spin at 140.000+ rpm to make boost. I drove a 1 year old Turbo Diesel engined car to work today. From low revs (1000rpm), 1st gear, entering a roundabout, I counted between 1-2 seconds before there was noticeable boost. At higher revs, there was something like 0,5sec delay before full boost/power was delivered. That same engine, without a turbo, would obviously allways feel as lethargic as this engine did before boost. That's why turbocharging makes sense, especially on smaller displacement engines. Without at turbo, the car I drove would have needed a significantly larger volume engine. Power delivery would have been better, but fuel consumption would be worse.

Lag is a inherent flaw on a turbo engine, but in most conditions it's not a major problem. After all, most European cars are now sold with a Turbo Diesel and Joe Public have no issues with driving them. It's not like it's a minute's delay, but in some conditions it's really noticeable. But you must not confuse added power from a turbo and turbo-lag. Yes, a turbo helps the engine make more power, but by design there is a delay.


Coming back to F1, in the 80's turbo lag was massive, lasting seconds. But remember this, they realised that pumping enough air volume at the mandatory blow off valve, overloaded it in such a way that you could boost the engine to higher pressures than IIRC the 2 bar blow off valve allowed. This means the turbo was grossly oversized for the application. They used to run at something like 5 bar. That will not be the case for modern F1.

Next years F1 engines will typically run at 3,5 bar boost, but boost is unlimited. Fuel flow is limited though, so excessive boost levels will probably not happen.

Last little point on competition, there isn't a single race class where (when allowed) a turbo charged engine is not the fastest type. i.e. there are no race series where NA rules over Turbo.
It seems your arguments are more related to whether a turbo engine makes more power than a NA engine. I agree, a turbo engine makes more power than a similarly sized NA engine. In fact, that is the only reason to turbocharge in the first place...

Last edited by Boss330; 07-03-2013 at 03:59 AM.
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      07-03-2013, 03:09 AM   #125
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Quote:
Originally Posted by NISFAN View Post
I have also stated there isn't one competitive event where NA trumps Turbo, even uphill races on tight winding narrow roads where surely lag would render the turbo useless? Surely Lag is that bad right?

In fact, typically turbo's are written out of the rule books because they have a seemingly unfair advantage. The original E30 M3's reason for being was cut short due to turbo charged engines. It was designed and bred to be a competitive race car, cut down by others 'going turbo'.....ha ha......oh the irony.
No one said turbos are useless, again see post just above...

Turbo engines are fantastic at producing maximum levels of specific torque and specific power (i.e. per displacement). That certainly contributes to their popularity and success.

The issue is that in many types of racing and even in non-competitive spirited driving there is a real need for turbo lag reduction or even elimination entirely of turbo lag. Who can argue against more power sooner, that is the true irony in your kooky defintions and bias.
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      07-03-2013, 03:12 AM   #126
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Quote:
Originally Posted by Levi View Post
M3/M4 N-Ring time is below 7:40 min.
The obvious questions are: Rumor? Source? Tires? Driver?

That achievement would represent about a 2 standard deviation performance above and beyond what a 3450 lb car with 450 hp could obtain (see prior threads on 'Ring time vs. power to weight regression analysis...). Unless the power to weight is substantially better than this and/or it is running street legal race rubber I seriously doubt a time of 7:3X. My prediction (given the best rumors on power and weight) is a 7:5X time.

Last edited by swamp2; 07-03-2013 at 04:14 AM.
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      07-03-2013, 04:48 AM   #127
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Quote:
Originally Posted by swamp2 View Post
No one said turbos are useless, again see post just above...

Turbo engines are fantastic at producing maximum levels of specific torque and specific power (i.e. per displacement). That certainly contributes to their popularity and success.

The issue is that in many types of racing and even in non-competitive spirited driving there is a real need for turbo lag reduction or even elimination entirely of turbo lag. Who can argue against more power sooner, that is the true irony in your kooky defintions and bias.
Hmmm, yes you have journo's that know nothing about cars that claim the M5 is laggy....because someone mentioned 'turbo'. I can post a video of my M6 accelerating from 50mph, not much lag in that at all, and we know it will very quickly pull lengths on a bigger displacement, lighter, e63/4 M6.

So why don't you plot E92 vs F80 torque curves, and show me where E92 is better even allowing for a momentary lag in boost on F80. What you'll conclude is that you're choosing to ignore a heathy torque increase across the entire rev range due to a blink of an eye 'lag' period. Talk about kooky ....or maybe torquey cars scare you?

BTW, that blink of an eye lag? a good driver responds to that, gets used to it, predicts it, eliminates the 'big issue'.

As for the new M3/M4, BMW have stuck with a fairly large displacement to achieve circa 450hp. This equals Low boost....the lower the boost the lower the lag. It would have been more ballsy to have gone for a 2.2litre 4 pot squeezed to get the same power. Similar to what Mercedes did in the AMG A45.

Whilst on AMG A45 here is what Auto Express wrote about power delivery from the little 2 litre 4 pot "there’s hardly any delay between pushing the throttle and feeling the thrust". I know a bit difficult for a turbo hater to digest but there you go
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      07-03-2013, 08:06 AM   #128
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I always assumed that turbo lag is the reason why dragsters use superchargers.
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      07-03-2013, 08:57 AM   #129
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Originally Posted by kgaler View Post
I always assumed that turbo lag is the reason why dragsters use superchargers.
Nope, Top Fuel NHRA rules state that turbo's are not allowed. Some of the other classes use Turbo's when the rules permit.
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      07-03-2013, 10:34 AM   #130
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NISFAN: It seems you are debating two different issues as one. Turbo lag and whether a turbo engine makes more power...

No one claims that a turbo engine does'nt make more power. It DOES! That's why they can downsize to a 3l engine and make a quicker car. Just as with the E60 vs F10 M5. It's just that the power delivery isn't as instant in a turbo engine.

To quote CAR on the Audi S4: "throttle response that could only be achieved on a turbo-free motor."
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      07-03-2013, 12:07 PM   #131
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Originally Posted by NISFAN View Post
I can post a video of my M6 accelerating from 50mph, not much lag in that at all
...
So why don't you plot E92 vs F80 torque curves, and show me where E92 is better even allowing for a momentary lag in boost on F80. What you'll conclude is that you're choosing to ignore a heathy torque increase across the entire rev range due to a blink of an eye 'lag' period.
Your obvious misunderstanding of lag continues, lag is a DYNAMIC concept which has very little to nothing to do with a dyno gathered torque curve and almost for sure can not be "observed" in your M6 video. In addition, I care about an engines peak hp much more than it's torque curve. Yes a broad flat torque curve is desirable but so is a high redline a lack of drastically falling torque approaching redline.

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Originally Posted by NISFAN View Post
As for the new M3/M4, BMW have stuck with a fairly large displacement to achieve circa 450hp. This equals Low boost....the lower the boost the lower the lag. It would have been more ballsy to have gone for a 2.2litre 4 pot squeezed to get the same power. Similar to what Mercedes did in the AMG A45.
We do not yet know the new engines displacement, but if you call 3.0-3.3 liters large, OK. The latter idea sounds great, go with a design to assuredly have more lag, which BMW, like many F1 teams, are going to great lengths to reduce or eliminate.

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Originally Posted by NISFAN View Post
Whilst on AMG A45 here is what Auto Express wrote about power delivery from the little 2 litre 4 pot "there’s hardly any delay between pushing the throttle and feeling the thrust". I know a bit difficult for a turbo hater to digest but there you go
Wait, I thought journalists know nothing about cars. OK, as long as they help promote your position they can be quoted and have a valid point, but when they have a contrasting opinion they then "know nothing".

Ugh.

Last edited by swamp2; 07-03-2013 at 12:15 PM.
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      07-03-2013, 12:16 PM   #132
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Quote:
Originally Posted by Boss330 View Post
NISFAN: It seems you are debating two different issues as one. Turbo lag and whether a turbo engine makes more power...

No one claims that a turbo engine does'nt make more power. It DOES! That's why they can downsize to a 3l engine and make a quicker car. Just as with the E60 vs F10 M5. It's just that the power delivery isn't as instant in a turbo engine.

To quote CAR on the Audi S4: "throttle response that could only be achieved on a turbo-free motor."
Well the two points are this:

If I take an NA engine and turbo charge it. The throttle response will be EXACTLY the same as it was in NA form. In other words the torque curve will be identical.....until.....the turbo starts producing positive pressure. So where is the lag?

Of course this config will be significantly more powerful than the NA it was based on.

So second option is to make an x powered engine to equal an an x power NA. This will be based on a smaller displacement engine + turbo. Yes of course the non boosted torque curve will be the same as an NA engine of same displacement (trying not to complicate things, but actually a boosted engine can run smaller duration camshafts that will promote higher torque lower down in the rev range). Only in this scenario, will a guy used to 4 litres feel let down by the lower (due to smaller displacement) torque values, until boost is held.

Example 1 Now dyno runs on turbo charged engines show that lag is at it's worst when you go from idle WOT. In this scenario, a.) turbo speed is as low as it can be b.) engine flow is low to start with, mostly likely below boost threshold any way.

Example 2 Opposite scenario is torque being controlled at high'ish revs (for example holding road speed mid corner on long sweeper, part throttle), then going WOT. Here turbine speed will be high to start, and exhaust gas will be high to energise the turbo. Lag in this scenario could be as little as 0.1 second.

The biggest road user complaint is that the turbo doesn't spool instantly when going for a lazy no gear change. Sure you are putting the engine into Example 1 territory. Drop a gear or two and you edge towards Example 2. You control the lag. This delayed acceleration is not much different to an NA, trundle along in an s65 M3 in 6th gear manual at 30mph, floor it and nothing much happens.

So you can see that lag depends on how you look at an engine turbo combo. Sure there is a delay before boost is produced on WOT, but torque is identical to an NA version of the same engine.
This reinforces my point that an NA has lag all the way to redline, because the boost never comes no matter how hard you rev it or push on the throttle. Yet NA enthusiasts bang on about Turbo lag. To me Turbo lag means that the engine has a turbo, which is a great thing. It means you are extracting as much power out of a set of internals as you possibly can.
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