Does boost lag add character?

alfadriver said:

E-boost does not make more power in a boost limited system, it just makes it quicker.

Given that this thread is about turbo lag and its undesirability, isn't that kind of the point?

I think a lot of the reason for things like electric water pumps, electric power steering, and even electric A/C compressors is that it divorces the pumping device from engine speed.  If you size a belt driven accessory so that it can be most useful at idle (like, say, power steering and A/C that need to be strongest when stopped) then it is vastly oversized when driving down the road and possibly dangerously oversized at the engine's redline.

I strongly suspect this is why BMW went to electric water pumps.  Their newer engines could generate huge heat loads at near idle speeds, but a belt driven water pump sized to work well down there would cavitate at high engine speeds.  Electric water pump solves that issue.

codrus (Forum Supporter) said:

alfadriver said:

E-boost does not make more power in a boost limited system, it just makes it quicker.

Given that this thread is about turbo lag and its undesirability, isn't that kind of the point?

But if you can dump a burst of power to the wheels from another source while the turbo spools to provide smoother power delivery, is that not just as good as spooling the turbo faster?  In either case you're getting a smoother, faster power delivery so it doesn't feel laggy. 

codrus (Forum Supporter) said:

alfadriver said:

E-boost does not make more power in a boost limited system, it just makes it quicker.

Given that this thread is about turbo lag and its undesirability, isn't that kind of the point?

 

You pointed out F1's decision to get rid of the MGU-H.  I'm pointing out why I think they did.  And the same does apply to real cars- but moreso since cost is a bigger issue with real cars.

And the current solution for turbo lag vs. boost limits is variable vane turbos are making a comeback.  

Pete. (l33t FS) said:

I think a lot of the reason for things like electric water pumps, electric power steering, and even electric A/C compressors is that it divorces the pumping device from engine speed.  If you size a belt driven accessory so that it can be most useful at idle (like, say, power steering and A/C that need to be strongest when stopped) then it is vastly oversized when driving down the road and possibly dangerously oversized at the engine's redline.

I strongly suspect this is why BMW went to electric water pumps.  Their newer engines could generate huge heat loads at near idle speeds, but a belt driven water pump sized to work well down there would cavitate at high engine speeds.  Electric water pump solves that issue.

Given all of the compromises involved, I would say that is very accurate.  Especially for higher revving engines.

rslifkin said:

codrus (Forum Supporter) said:

alfadriver said:

E-boost does not make more power in a boost limited system, it just makes it quicker.

Given that this thread is about turbo lag and its undesirability, isn't that kind of the point?

But if you can dump a burst of power to the wheels from another source while the turbo spools to provide smoother power delivery, is that not just as good as spooling the turbo faster?  In either case you're getting a smoother, faster power delivery so it doesn't feel laggy. 

No, because of the multiplication effect of the turbo.  Making up numbers, putting 20 hp into that compressor wheel might give you 100 hp from getting the boost sooner, and that's a smaller/lighter motor than putting 100 hp to the wheels directly.  You'd also need to dump power to the wheels for longer, because simply accelerating the car isn't bringing the turbo RPMs up.  If you've got a mechanical system with 500 ms of lag, putting extra power to the wheels doesn't reduce that lag, whereas spooling up the turbo directly does.

alfadriver said:

You pointed out F1's decision to get rid of the MGU-H.  I'm pointing out why I think they did.  And the same does apply to real cars- but moreso since cost is a bigger issue with real cars.

Fundamentally F1 dumped it because Mercedes did such a better job of it than everyone else that they felt it was the only way to stop them from winning all of the championships.  That's not really relevant to street cars. :)

I have never driven a turbo anything on the street that I liked more than a similar hp non-turbo version....lag is the devil.  I've never driven a turbo out on a road course but I'm pretty sure it would be hard to beat in that space, on the street though where you change you mind often and can't always plan the rpm not so much.

I'll diverge a bit and talk no lag superchargers.  I've done a few of those on street car over the years and they drive nice...but Im not sure I'd build another one of these again either, at least not with the near flat boost curve the roots and screw blowers kick out.  The engineer in me loves this setup but personally just something about the way they drove I didn't love.....fast and responsive yes, but the way they drove, once I got over the euphoria of the hp no. 

When I first got my 308 I remember I called my father, who'd tried to talk me out of the idea,  from the car to say how amazing it felt.  It wasn't fast, but the sound, the vibration maybe, don't know but it very much reminder me of my motorcycle racing days.  It was a claimed but tired 235hp@6800 and in town I would shift about 4500 or so.  Then engine rebuild and blower 1 bumper it like 400hp so much faster but I noticed I was now shifting at about 3500rpm.  Blower 2 bumped it to 600ish hp and I was now shifting at 2500rpm and it now reminded me of a bigblock corvette, it would just kind of shake and go.  I t still had most of the magic when driven to redline in anger but in normal driving it was a completely different car in normal driving. Hopefully the 14 year v12 conversion restores all the magic.

Turboson the street though are magic free imho 

In reply to codrus (Forum Supporter) :

As I see it, F1 dropped the MGU-H because no other engine makers were willing to spend the money for such a minor gain.  Especially since it was faster to just put the same energy to the wheels.

codrus (Forum Supporter) said:

 

No, because of the multiplication effect of the turbo.  Making up numbers, putting 20 hp into that compressor wheel might give you 100 hp from getting the boost sooner, and that's a smaller/lighter motor than putting 100 hp to the wheels directly.  You'd also need to dump power to the wheels for longer, because simply accelerating the car isn't bringing the turbo RPMs up.  If you've got a mechanical system with 500 ms of lag, putting extra power to the wheels doesn't reduce that lag, whereas spooling up the turbo directly does.

You do realize that the time lag to apply electrical power to the wheels and the turbo is exactly the same, right?  And the boost then has to be generated and then combusted before it turns into wheel torque.  Whereas the electrical energy just goes to the wheels.   (and since all engines are boost limited, there are limits to how much boost can be generated)

In terms of reality- there are multiple mild hybrid systems out there that use the alternator as a motor to drive the engine, but there are no e-boost systems out there.  Cost-benefit is on the side of the direct drive motor.  It's pretty cheap to turn an alternator into a motor compared to adding an electric motor into a turbo system.  It's just a more efficient (cost, timing, etc) way of filling that lag hole.

My FD RX7 was so smooth with it's power delivery and I think it was one of the first modern turbocharged cars to really reduce lag with it's sequential setup. That said, I was coming from a Precision 66 mm Galant VR-4 with 7.8 to 1 compression. The FD was a better overall car in almost every way except it never left me and passengers giggling and pushed into the back seat.  Had I kept the FD longer, I probably would have put a big single on it. A stock Galant with a 14b wasn't particularly laggy but purposefully making it laggier in exchange for a bigger payoff was a sacrifice I wanted to make. If people want turbocharged cars that don't *feel* turbocharged and have zero lag I could see why but as for me, I like the drama. Street cars aren't competing so it's not about being the fastest but what is more fun to you.

In reply to crankwalk (Forum Supporter) :

Love the pic...and that is why 80s turbos had a bad habit of ending up in guard rails.  

This is what I was saying...its fine on the boost, its fine off the boost but when you change your mind there is no "medium".  You get the on ramp and start rolling in throttle for a little fun then find its now accelerating hard without adding throttle until the its spinning if you don't get out of the throttle quick enough.  Its an unstable system in engineer speak because it requires active input to control.

I had 1990zx6 motorcycle that from the factory the power dropped between 9000-9500 then the climbed steeply to 12500.  On the track you had to keep it above 9500, miss a down shift and mid-corner the you'd find the back walking out  as 9500 throttle was WAY too much 2-300 rpm later..really dangerous.  Lag is like that...bam! the car is spinning.  Nothing charming about it.

mke said:

In reply to crankwalk (Forum Supporter) :

 

I had 1990zx6 motorcycle that from the factory the power dropped between 9000-9500 then the climbed steeply to 12500.  On the track you had to keep it above 9500, miss a down shift and mid-corner the you'd find the back walking out  as 9500 throttle was WAY too much 2-300 rpm later..really dangerous.  Lag is like that...bam! the car is spinning.  Nothing charming about it.

All about preference my man. Talking about motorcycles and lag, my 71 H1 does nothing below 6k and then rockets to 10k with the front wheel up. I love it.

But what about blow through carburetors and old school turbo tech (the worst of the worst to some)? My 82 Seca Turbo does nothing until 5k then boost hits and stretches your arms straight out. On a 120 tire. From an engineering perspective this would all be trash and leave room for improvement and you wouldn't be wrong in a sense.

But I LOVE a turbo rush that makes you E36 M3 yourself occasionally.The question is does it add character and some people like it. When you are familiar with it's characteristics and can control it by respecting and anticipating an imperfect power delivery, it's really enjoyable to me.  Different strokes for different folks.

I've driven turbo cars that 'came on' so hard if you floored it from lower rpm that they would break the rear wheels loose.  I really like the modern twin scroll turbos (a Borg Warner invention, IIRC). as they minimize that sort of behaviour and smooth out the transitions, minimizing lag as long as you don't go too big with them.

In reply to wspohn :

Mazda had twin scroll Hitachi (?) turbos on RX-7s in the 80s.

I think it might have been Garrett or Schwitzer that pioneered it, although given how B-W hoovered up a lot of turbo companies, maybe technically they did 

The tiny twin scroll TD04 on my S40 (dates back to 1996, mine was an 02) may as well have had the boost gauge attached to the throttle pedal. 9psi at quarter-third throttle, any more than that just told the trans what gear to be in.  Fun ride.

crankwalk (Forum Supporter) said:

All about preference my man. Talking about motorcycles and lag, my 71 H1 does nothing below 6k and then rockets to 10k with the front wheel up. I love it......

That's a bit different.  There is nothing very dangerous a about an engine coming onto its power band and nothing really dangerous about rapid changes in power if you're going straight. 

The problem is rapid changes in power mid-corner and even worse is what I described where there was a significant power drop for 500 rpm followed by a rapid increase....it was very dangerous out on the track but almost unnoticeable on the street where you're not normally managing mid-corner wheel slip.

Turbo lag is the same issue.  As long as you're going straight its fine and to you're point can be quite a rush.  Mid corner that rush often becomes a crash.  We had a 2010 FWD VW tiguan....hit the gas to pull out and start the turn then the turbo came on, the front wheels start slipping and the car heads for the ditch until you back off the throttle...just horrible to drive.  Our 2018 GLC is much better for sure but that has a lot to do with the 9spd? trans and better ECU mapping, but its got nothing on our non-turbo 2014 glk so I'll be sad when it dies as its the last on the nonturbos.

On the ferrari I spent a ton of time on the simulator trying to get the power curve looking decent and once its ready for the dyno I'll do what I usually do and play with the tuning to force the curve smooth (pull out a little timing to remove the peak before the dip) so I don't need to worry about who's driving it...more throttle, more rpm = more power as it should be.

In reply to mke :

The best description of driving a 3 liter 930 was that if you were not on the power, you understeered into the weeds. If you got on the power, the turbo would hit late and you would go backwards into the weeds when the tires spun. And if you lifted after the turbo hit, you would snap around and then back into the weeds. 

But if you could time it just right and lift a little just as the turbo woke up, it was seamless. "And if you were very, very good, it would let you do it again"

I am sure a lot of that is the really low compression ratios used on the early turbo cars.  IIRC the 930 had 6:1 at first.  No power off boost.  For one reason or another, higher compression also seems to make a turbo happier.  The most linear, instant-boost car I ever experienced was a 4.5l BGN with 10:1 compression and a 76mm turbo.

mke said:

crankwalk (Forum Supporter) said:

All about preference my man. Talking about motorcycles and lag, my 71 H1 does nothing below 6k and then rockets to 10k with the front wheel up. I love it......

That's a bit different.  There is nothing very dangerous a about an engine coming onto its power band and nothing really dangerous about rapid changes in power if you're going straight. 

The problem is rapid changes in power mid-corner and even worse is what I described where there was a significant power drop for 500 rpm followed by a rapid increase....it was very dangerous out on the track but almost unnoticeable on the street where you're not normally managing mid-corner wheel slip.

Turbo lag is the same issue.  As long as you're going straight its fine and to you're point can be quite a rush.  Mid corner that rush often becomes a crash.  

 

I understand exactly what you're talking about I just disagree. Even vehicles that I would consider laggy could be predictable  in corners with throttle modulation and being comfortable with that vehicle. A lifetime Corvette driver hopping directly in 930 with no frame of reference may have a higher likelihood of losing it mid turn when boost comes on unexpectedly (to them). Some say that's a deadly flaw but to somebody with lots of seat time in a 930, it is viewed as part of the dynamics and can be mastered. Just part of its character. I appreciate laggy, journal bearing 70s and 80s tech for what it is and don't try to "engineer out" its quirks. I think a period correct early turbo tech hot rod is charming and If I wanted no lag and seamless delivery, I'd just buy something new.

I guess I'll say the market voted and turbos were the exception and generally sold poorly until they could be about as smooth as non-turbos.  A modern turbo is at least as smooth and responsive as an 80s/90s non-turbo....and now they're everywhere.

mke said:

I guess I'll say the market voted and turbos were the exception and generally sold poorly until they could be about as smooth as non-turbos.  A modern turbo is at least as smooth and responsive as an 80s/90s non-turbo....and now they're everywhere.

The question isn't "What's better, faster, and more practical?" the question is "does boost lag add character?" and I say yes it absolutely can. It has nothing to do what the market has spoken about. The market has spoken that automatics are better. Infotainment systems are better. Airbags are better. What sells better doesn't have anything to do with character to me. Turbo lag in a early turbo vehicle is like anything else that has since been made "better". Character is a nostalgic part of the experience for better or worse. 

Turbo lag adds character to a car like lead paint adds character to a house 

In reply to mke :

I think the turbo lag character thing is kind of like piston port vs reed valve two strokes. The piston port motor has that drama to it but its drama most people would happily be rid of.

I think it adds character to certain cars. I think I would feel a lot better about the character/lag on a 930 while out for a Sunday drive than I would about the lag on my 2002 WRX wagon while getting groceries. The 2015 GTI handles the latter with aplomb, and manages to be engaging on the former, while admittedly not having much 'character' from an engine standpoint. 

Lots of confusion here between Lag and Boost Threshold.
 

If you can shift into boost, it's a boost threshold issue. If you need to keep your foot down for X time to make boost, reguardless of RPM, that's lag.

While the two are linked, they are fundamentally different things.

mr2peak said:

While the two are linked, they are fundamentally different things.

Different but both dangerous in a similar way.  A steep torque rise is an unstable characteristic and lag means without looking at the tach you can't be sure what's coming next...but you never want the engine output to change with no change in driver input.

The VW I had was even worse because the ECU was lagging the throttle I guess for emissions but leaving a stop sign 100% pedal got me 18% at the engine, until the ECU decided to open the throttle more so the big issue wasn't even real turbo lag, it was simulated lag some jackass programmed into the ECU