Turbo lag in M3 vs M5

[ss134]

One of the key characteristics of all M3s has been instantaneous throttle response - I am convinced that the S55 will be one of if not the most responsive turbo motors ever.
This is BWWs most important car, it encapsulates the essence of BMW- I have faith that the engineers have come good on the key concerns we all have regarding throttle response , steering etc.
I believe far more time and effort will have been invested in these areas than even the M5/6.

[bm323]

Originally Posted by solstice

I had a passenger in the car during one stint with the B7 and we both laughed at it. I pushed the throttle at the apex and we looked at each other and counted 1.2.3 wooooosh. It's that bad. But then, it's likely not an issue for the driving style of people who actually buy these cars. The S63TU sure has plenty lag compared to for example the S65 but it's not bad for a turbo car, not bad at all.

Originally Posted by Needsdecaf

This does not speak well for your driving analytical skills. The lag is very noticeable.

Guys with little experience/unfamiliar with the M5 and drive it slow and then stomp it will definitely feel the lag.

[elitex]

Originally Posted by Boss330

Remember that the S63Tu behaves different in Normal mode vs Sports mode. It has a version of the "pre tensioned" turbos we will get in the S55, but that is only active in Sports mode (as it's detrimental to fuel consumption).


On a different note, it seems RealStig is in good company when talking about the behaviour/response of the S63Tu... Perhaps you should let Chris Harris know he has poor "driving analytical skills"

Agreed. In comfort mode, there's all kinds of lag. Sports and sports plus, not so much. Now, throttle becomes a little tricky with both sport modes, specially when you jump in from M3. It takes a little getting used to.

[Boss330]

Originally Posted by bm323

Guys with little experience/unfamiliar with the M5 and drive it slow and then stomp it will definitely feel the lag.

Originally Posted by elitex

Agreed. In comfort mode, there's all kinds of lag. Sports and sports plus, not so much. Now, throttle becomes a little tricky with both sport modes, specially when you jump in from M3. It takes a little getting used to.

I'm not gonna say that a turbo engine is as responsive as a good high performance NA engine. There is allways bound to be a certain delay between throttle and full boost. However in Sports modes the delay in the F10 M5 is so small it's allmost hypothetical

This is why so many reviewers have said it doesn't really feel like a turbo engine. Expect the S55 to be even better

And on the subject of people not used to drive the F10 M5; One of those complaining about lag in the M5 also felt there was no need to go above 5500rpm as there was nothing to gain in acceleration by doing that... Apparently he shifted at around 5500rpm and thought that was the best way to extract maximum acceleration from the car... The M5 is still plenty fast doing that, but you definitely aren't getting the most out of the car. And by shortshifting at 5500rpm, the torque at the wheels decreases compared to what you would have at 7000rpm if you stayed in the same gear. As long as torque at the wheels are higher staying in the same gear, there is nothing to gain by shifting to a higher gear. You don't want to shift before torque at the wheels in the gear you are in are equal to what the next gear will give you.

Some just look at the torque curve of the engine and thinks that since in the F10 M5/F8X M3/4 it falls off from around 5500rpm, that's when you should change up. But changing up reduces torque multiplication through the transmission and thus decreasing acceleration compared to staying in the same gear, until the torque at the wheels numbers cross.

[catpat8000]

Originally Posted by Boss330

I'm not gonna say that a turbo engine is as responsive as a good high performance NA engine. There is allways bound to be a certain delay between throttle and full boost. However in Sports modes the delay in the F10 M5 is so small it's allmost hypothetical

This is why so many reviewers have said it doesn't really feel like a turbo engine. Expect the S55 to be even better

I have no doubt the new M3 will be better than the M5 in terms of lag but I can guarantee those of you saying the M5 has no detectable lag are wrong. It does have lag and if you can't feel it, either you haven't really driven this car or you don't know what lag feels like.

But I also know who I am replying to and I know you've never ever made a mistake in your whole life, so I don't expect you to acknowledge that now.

[Jockey]

Originally Posted by catpat8000

I have no doubt the new M3 will be better than the M5 in terms of lag but I can guarantee those of you saying the M5 has no detectable lag are wrong. It does have lag and if you can't feel it, either you haven't really driven this car or you don't know what lag feels like.

But I also know who I am replying to and I know you've never ever made a mistake in your whole life, so I don't expect you to acknowledge that now.

And there are people who swear they can tell the difference when 10 lbs is removed from a 3500 lbs car, so...

I've owned multiple turbocharged cars in my life, each next had much less appreciable turbo lag than the previous one. So much less so that my N54 has "nearly" no lag compared to the previous. But it still has turbo lag.

It's all a matter of perspective and what type of engine response you are acclimatized to.

[elitex]

Originally Posted by catpat8000

I have no doubt the new M3 will be better than the M5 in terms of lag but I can guarantee those of you saying the M5 has no detectable lag are wrong. It does have lag and if you can't feel it, either you haven't really driven this car or you don't know what lag feels like.

But I also know who I am replying to and I know you've never ever made a mistake in your whole life, so I don't expect you to acknowledge that now.

I know what turbo lag feels like. I owned an Audi A4 and that thing was horrible. I also know how to differentiate lazy throttle and turbo lag.

M5 turbo lag is very minimal. If you're expecting it to be like an M3 then I understand the feeling.

[Boss330]

Originally Posted by catpat8000

I have no doubt the new M3 will be better than the M5 in terms of lag but I can guarantee those of you saying the M5 has no detectable lag are wrong. It does have lag and if you can't feel it, either you haven't really driven this car or you don't know what lag feels like.

But I also know who I am replying to and I know you've never ever made a mistake in your whole life, so I don't expect you to acknowledge that now.

I think you must mistake me for someone else
I have made many mistakes. and also here on the forums I have been wrong

As elitex says below, I also know what turbo lag feels like. I own a 1988 Ford Sierra Cosworth which has a 2l, 8:1CR, 1bar boost engine at 270-300hp. That engine HAS lag and it's wait for it, wait for it, THERE it comes all at once! Good fun to drive, but hopeless on a twisty track as it's hard work to keep the engine on boost

As I said above, a turbo engine will NOT be like a good high performance NA engine. There is bound to be a delay, but there is a difference between a 1-2sec delay and a 0,2-0,5s delay. It's not as if boost builds slowly in Sports mode in the M5 and takes a few seconds to go from 0 boost to max boost. Yes, there is a delay (as there will be in any turbo engine) but when it takes less than 0,5s to build full boost then that isn't all that bad IMHO

So, I'm not sure where you and I differ. We both agree that a turbo engine is bound to have a minimum of lag. And everyone I know of (including people like Chris Harris) also agrees that the M5 is in a elite group of very few turbo cars when it comes to throttle response. I even made a point of saying that a turbo engine won't be as responsive as a NA engine, just to avoid being accused of saying that the M5 is as responsive as such an engine... But apparently I wasn't clear enough

I have driven the F10 M5 on the autobahn (and on normal street roads) to over 250km/h if that counts, with multiple accelerations and passes

Originally Posted by elitex

I know what turbo lag feels like. I owned an Audi A4 and that thing was horrible. I also know how to differentiate lazy throttle and turbo lag.

M5 turbo lag is very minimal. If you're expecting it to be like an M3 then I understand the feeling.

Agree 100%

The M5 is also two different beasts in this regard when it's in normal mode and in Sports mode. And in Normal mode, even my NA N53B30 feels like it has lag. It's not lag obviously, just a "lazy" throttle setting in the fly by wire throttle. The throttle isn't connected via mechanical linkage anymore, so in Normal mode there seems to be a delay between accelerator pedal input and actual throttle valve movement. That disappears in Sport mode and the engine feels much more responsive, in fact it doesn't just feel more responsive. It is more responsive since the throttle valve responds quicker to gas pedal input

Lag and lazy throttle can often be confused.

[jlh335i]

You guys are comparing a larger displacement v8 to a smaller i6... Now maybe Boss can chime in with the actual turbo sizes for each motor, but the fact that the m5 makes 127 hp/liter and the m3 143 hp/liter, Im going to predict that you will have more lag in an m3.

Also, auto transmissions (DCTs etc) with good programing are going to do a lot to hide turbo lag from a non discerning driver. Take any turbo car with a manual and step on the gas from low rpms - you will experience turbo lag, and you will learn where that turbo(s) begins to spool. Turbo lag is just a part of the nature of forced induction (sans twin-screw), and perhaps some one would like to post a compressor map and go into further detail.

[Suave]

This thread like others is why I will be able to retire early as a BMW Mechanic with all the time I spend here.

[Needsdecaf]

Originally Posted by Boss330

Remember that the S63Tu behaves different in Normal mode vs Sports mode. It has a version of the "pre tensioned" turbos we will get in the S55, but that is only active in Sports mode (as it's detrimental to fuel consumption).


On a different note, it seems RealStig is in good company when talking about the behaviour/response of the S63Tu... Perhaps you should let Chris Harris know he has poor "driving analytical skills"

I'll say it to Chris Harris or anyone else. If you're not already on it, you'll get lag in an M5. I've driven a 1/2 dozen, both 2013 and 2014. If you're tooling along at low revs, you can definitely feel the turbos spool and the boost build.

The car does have good power off boost. I mean, it is a 4.4 liter V8 after all. But to say there's no lag is a fallacy.

[catpat8000]

Originally Posted by Needsdecaf

I'll say it to Chris Harris or anyone else. If you're not already on it, you'll get lag in an M5. I've driven a 1/2 dozen, both 2013 and 2014. If you're tooling along at low revs, you can definitely feel the turbos spool and the boost build.

The car does have good power off boost. I mean, it is a 4.4 liter V8 after all. But to say there's no lag is a fallacy.

+1

Absolutely correct.

[bm323]

Originally Posted by Needsdecaf

I'll say it to Chris Harris or anyone else. If you're not already on it, you'll get lag in an M5. I've driven a 1/2 dozen, both 2013 and 2014. If you're tooling along at low revs, you can definitely feel the turbos spool and the boost build.

The car does have good power off boost. I mean, it is a 4.4 liter V8 after all. But to say there's no lag is a fallacy.

Originally Posted by catpat8000

+1

Absolutely correct.

Fat hopes if you both think the F80 M3 has zero lag It's a question of degree and how the cars are driven

[swamp2]

Originally Posted by Boss330

You don't want to shift before torque at the wheels in the gear you are in are equal to what the next gear will give you.

Just to be clear and 100% correct this is only the shifting "rule" in engine/transmission combinations where the torque to the wheels curves actually cross. The obvious counterexample is the S65 (and most cars with similar shaped power curves). In such cases the curves never cross so it is always shift at redline. Also, in such cases the wheel torque is always lower immediately post shift.

Originally Posted by Boss330

Remember that the S63Tu behaves different in Normal mode vs Sports mode. It has a version of the "pre tensioned" turbos we will get in the S55, but that is only active in Sports mode (as it's detrimental to fuel consumption).

I've not heard that is uses a system similar to the one in the upcomming S55. Can you provide a reference? Is there a description of the way the system works? To me this is somewhat negative for the S55 if the S63Tu already has a similar system and clearly exhbits some lag. Now surely the system can and likely will be improved but it just isn't the true "lag elimination" device many are hopeful for.

[ybbiz34]

Originally Posted by Boss330

Wow. SL63 was mighty impressive there.

[Boss330]

Originally Posted by swamp2

Just to be clear and 100% correct this is only the shifting "rule" in engine/transmission combinations where the torque to the wheels curves actually cross. The obvious counterexample is the S65 (and most cars with similar shaped power curves). In such cases the curves never cross so it is always shift at redline. Also, in such cases the wheel torque is always lower immediately post shift.



I've not heard that is uses a system similar to the one in the upcomming S55. Can you provide a reference? Is there a description of the way the system works? To me this is somewhat negative for the S55 if the S63Tu already has a similar system and clearly exhbits some lag. Now surely the system can and likely will be improved but it just isn't the true "lag elimination" device many are hopeful for.

Thanks for the clarification and obviously 100% correct that on a engine where the curves never cross you will allways go to the redline before shifting

The info on the anti lag measures was in my post on page 1 and was taken from the info when the F10 M5 was released:

http://f80.bimmerpost.com/forums/sho...69&postcount=7

Software/mapping:
Now, both the S63 and S55 will use some sort of mapping to aid spool up and keep the turbos "pre tensioned" in Sport modes. How much more advanced that is on the S55 compared to the S63, I do not know. But here is how BMW explains how it works on the S63Tu:

In Sport or Sport plus mode, a suitable VALVETRONIC controller and the waste gates keep the turbocharger in the higher speed range. Normally, the waste gate used to regulate the charging pressure opens so that the exhaust gas flows out with the minimum possible loss. Pressure is built up again only when I hit the accelerator. For an improved response, I leave the waste gate closed until I need it for regulating. The exhaust gas then always passes over the turbine, which then runs at a considerably higher speed. When even more power is demanded, it is immediately available. However, I have a gradually rising counterpressure that causes a slight rise in consumption. This function can therefore be switched on and off. By the way, in the BMW 1 Series M Coupé the same function is activated at the M Button.

This interview has some really good descrptions in addition to what I have written above:

http://f10.m5post.com/forums/showthread.php?t=588858

[swamp2]

Originally Posted by Boss330

I sure hope the system on the S55 is superior to that on both the M5 and the 1M. I did not know the 1M had this type of system. Both cars have distinctly noticeable lag. The 1M from both my personal experience and journalists, the M5 from forum members and journalists (no personal experience).

[mkoesel]

Originally Posted by swamp2

I sure hope the system on the S55 is superior to that on both the M5 and the 1M. I did not know the 1M had this type of system. Both cars have distinctly noticeable lag. The 1M from both my personal experience and journalists, the M5 from forum members and journalists (no personal experience).

Such anti-lag measures - which are only available in more aggressive ECU modes, and which are really there to keep the turbos spooled rather than to get them spooled quickly - aside, is there any technology we are aware of in the S55 design that could hope to give us a lag-free experience from idle? It seems unlikely at this point, no?

[/// M sa]

Originally Posted by mkoesel

Such anti-lag measures - which are only available in more aggressive ECU modes, and which are really there to keep the turbos spooled rather than to get them spooled quickly - aside, is there any technology we are aware of in the S55 design that could hope to give us a lag-free experience from idle? It seems unlikely at this point, no?

If your in 5th gear at 2000 rpm and slam on the gas you will get lag regardless (not as much with new systems but it's there) I get small lag at high gears in my GTR but with a tune it's almost goes unnoticed.

[Jockey]

Originally Posted by //M sa

If your in 5th gear at 2000 rpm and slam on the gas you will get lag regardless (not as much with new systems but it's there) I get small lag at high gears in my GTR but with a tune it's almost goes unnoticed.

Hmm, didn't know you've driven the S55 already.

[/// M sa]

Originally Posted by Jockey

Hmm, didn't know you've driven the S55 already.

I am talking about most turbo cars not s55 but to think the s55 will have 0 lag is just futile. I think it will have less lag than M5 but it will still have some lag.

[aajami]

Originally Posted by //M sa

I am talking about most turbo cars not s55 but to think the s55 will have 0 lag is just futile. I think it will have less lag than M5 but it will still have some lag.

I think this the statement to close out this thread with, and your first sentence is likely true for any turbo engine.