- 1,825
- California
Does anybody know about the Lan Evo/ Subaru Impreza WRX? Because those are supposed to have turbos the size of the UK, aren't they? Same goes for the RUF BTR... I mean, its name IS "Big Turbo RUF" 
Enormous turbo lag/ really high boost threshold
- Thread starter Not_A_Guest
- 77 comments
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Do you drive (or tried previously) turbo car in real life? If the rpms are high enough (lets say 2000+ for petrol engine) then there is no lag to throttle respone. Reaction is instant. The problem is with low rpms when turbo doesn't spin up fast enough and you need to wait until it reaches it's optimal rpms (~100.000rpm or so).
I think you are imagining different kind of 'lag'... (which is non-existent in real life.)
It does. And we aren't talking about some pre 1980s cars. Let's not go to the extreme here. For a normal road car, 2000rpms+ is enough to make turbo spin up fast enough
The implemented lag in the game
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- 2,187
- Kansas City
- PsuPepperoni
0:45
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- 379
- PNW
- Zenmervolt
This is wrong, wrong, wrong, and just plain wrong. You have clearly not owned or driven a turbocharged car (at least, not one with a manual transmission).
If I'm cruising at 75 mph in 5th gear in my Porsche 951, the engine is spinning at over 3,000 RPM. This is above the boost threshold. However, at a steady 75 mph, the turbo is NOT producing boost because the throttle is mostly closed. In fact, at that speed in 5th, the engine is actually seeing negative pressure in the intake manifold (10-15 inches of mercury to be specific).
Mashing the throttle to the floor from cruise at that speed while remaining in 5th does NOT give "instant" response. Instead, there is a 1-2 second "lag" where the throttle is open, but the turbo has not yet come up to speed (since at the steady-speed, mostly-closed throttle condition of cruise the turbo is barely spinning). After the brief period of lag, the turbo comes on and acceleration begins.
That is what lag is.
Now, this is more noticeable in my 951 than in modern cars for a few reasons. (1) The 951 is an older design, with one large turbo that has relatively high inertia. (2) The 951 uses high boost, which means a lower static compression ratio and therefore makes almost no power when the engine is off boost. (3) The engine is NOT boost limited at lower RPM to produce a flat torque curve, which accentuates the perception of lag because the result is that the turbo comes on "all at once" (as I tend to accidentally remind myself about once a year when coming out of a slow 2nd gear corner and not being straight before the lag ends).
Modern turbocharged engines use smaller turbos that spool faster and reduce the lag time, as well as artificially limiting boost to create a flat torque curve (as my Volvo T5 does to create a constant 243 ft-lbs from 2,700 RPM all the way to 5,100 RPM; this is achieved by electronically opening the wastegate to prevent the turbo from fully spooling too early).
Lag is also often disguised by downshifting; if I drop into 3rd before accelerating in the 951, I barely notice the lag at all. Similarly, on my Volvo, since it's an automatic and downshifts on its own accord if I mash the throttle from steady cruise, I don't notice much lag due to the downshift.
- 379
- PNW
- Zenmervolt
Does anybody know about the Lan Evo/ Subaru Impreza WRX? Because those are supposed to have turbos the size of the UK, aren't they? Same goes for the RUF BTR... I mean, its name IS "Big Turbo RUF"
The CTR actually had a larger turbo and more severe lag in real life than the earlier (and less extreme) BTR. But as I said earlier, the CTR definitely does not have lag implemented in the game.
I have, i did and i know what I'm talking about.
The throttle can not be mostly closed on a race track in GT6. We aren't talking about such situation. Take your 951 to the track and then talk about reaction.
No it's not. That's an old Porsche with poor turbo implementation or old engine which has some problems or whatever. Normal, current road cars, have no such turbo lag in the mid-high range of rpms.
Now you just said that there is no turbo lag during optimal rpm range. You are contradicting yourself by comparing old car vs normal modern cars which we are talking about.
- 379
- PNW
- Zenmervolt
Clearly, you do not.
I have never disputed this. The fact that lag does not typically come up in track scenarios (the Porsche 917/30 being a notable exception, as recorded interviews with Mark Donahue make very obvious) does not change the fact that lag does exist.
"Lag" is what happens in the scenario I described. It is not a scenario typically found on a track (with the exception of certain low-speed corners, as I alluded to in my post), but, as I have just said, that doesn't mean the situation never comes up.
And for the record, I do track the 951. That's how I know about the lag coming out of a slow 2nd-gear corner.
Yes. A fresh engine with mild race modifications that dynos 300 ft-lbs of torque and 275 hp at the rear wheels is clearly an engine with "problems" and a "poor turbo implementation." *eye roll*
That is not even close to what I have said. Perhaps there is a disconnect here since you are, presumably, not a native English speaker and are having difficulties parsing what I am saying.
I did not say that there was "no" lag. I said that the feeling is disguised by downshifting and that the feeling is further disguised by modern electronic systems that artificially limit the build-up of boost, and that lag is reduced by using smaller turbos with lower inertia.
Clearly you have no idea what you are talking about.
No, the lag we are talking about (and OP as well) is the one that's very clearly shown in the Top Gear video above. This is the lag we are talking about.
I don't want and will not go into details about your old Porsche and what it has and what it doesn't. I take modern, most popular, cars as an example and if the engine is working properly, there won't be any '1-2sec lag' from mid-range and up. Your Volvo is an example as well.
There is no disconnect and your presumption is wrong. I understand perfectly what you are saying and where are your mistakes. The 'downshift' has nothing to do here, your modern Volvo will have normal response even in the same gear going from 3k and up. And you know it and you can test it again by yourself.
If you don't feel it (meaning you get proper response without any delay) then there is no lag. And it doesn't matter which systems make it disappear.
- 1,460
- England
Please @YZF, it is quite obvious to me, from your last few posts, that you are most definately confusing turbo lag for boost threshold.
Jeremy Clarkson is not the be - all and end - all of motoring knowledge.
Please stop with the arguing, as anyone who genuinely knows what they are talking about is laughing at your last few posts.
Go and buy this month's fast Ford magazine, has a great little writeup regarding turbo myths, and specifically the common misconception that boost threshold is turbo lag.
People have been confusing these for years, so don't feel bad. Just do some more research.
None of this post is intended as a personal attack, just a friendly 'leave off'.
Jeremy Clarkson is not the be - all and end - all of motoring knowledge.
Please stop with the arguing, as anyone who genuinely knows what they are talking about is laughing at your last few posts.
Go and buy this month's fast Ford magazine, has a great little writeup regarding turbo myths, and specifically the common misconception that boost threshold is turbo lag.
People have been confusing these for years, so don't feel bad. Just do some more research.
None of this post is intended as a personal attack, just a friendly 'leave off'.
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The closest way I know to simulate turbo lag in a GT game is to skip the clutch/flywheel upgrades.
Basically, turbo lag happens because the turbine isn't directly synchronized with the engine. Extreme differences in throttle input will cause turbo lag because the turbine can't react fast enough. Especially if the turbine needs time to reach its operating RPM.
GT doesn't simulate this. Turbo engines have a static torque curve just like NA engines.
Basically, turbo lag happens because the turbine isn't directly synchronized with the engine. Extreme differences in throttle input will cause turbo lag because the turbine can't react fast enough. Especially if the turbine needs time to reach its operating RPM.
GT doesn't simulate this. Turbo engines have a static torque curve just like NA engines.
- 40,419
I do like that despite almost the entire first page being people trying to head off this discussing by clearly explaining what turbo lag is and what boost threshold is not, this thread has still devolved into people misusing the word to defend something that GT6 does not model.
Clearly.
Linky.
That's a car that makes 922 pound-feet of torque at 2200 RPM. Boost threshold really doesn't apply; and I really doubt he was cruising in 7th gear when he did that. And yet he is still describing hesitation in the throttle response. And that review is parroted by others who have also driven the car; most notable of them being Gordon Murray.
So how is it non-existent?
Clearly.
Yes. I in fact learned to drive in one (a Dodge Shadow ES Turbo), and several people in high school and college had some that I drove as well over the years (a Thunderbird Turbo Coupe, a Dodge Daytona IROC and a Golf IV GTi). Mom's car had a good amount of torque pretty low (and the lag wasn't very noticeable because the engine itself was quite large and the turbo didn't really do that much but add more torque to an already torque-focused engine. The Turbo Coupe was much worse at hiding it, if I had to guess mostly because the stock engine was relatively gutless and the turbocharger nearly doubled its power. It also had a much higher power band than the lazy revver in the Shadow. The Daytona was a cross between the two, with an earlier torque rush while still being much more rev happy, but still not particularly nice if you got into it in a turn after being off throttle. The GTi was a saint compared to all of them, with torque available just off idle seemingly all the way to redline; but the throttle response still wasn't what anyone would call instant and I as a result greatly preferred my other friend's VR6 Jetta.
No it's not. It absolutely is not. You have never driven any car with a turbocharger (or even opened a book about the subject) if you're making this statement. It is physically impossible for a turbocharger to "instantly" respond to throttle response at any RPM. That's why manufacturers largely abandoned them in the 1990s for larger engines or superchargers; and why Volvo just announced a twin charged engine a month ago. You can attenuate the effects and/or work to lower the delay time (lighter/ceramic blades, smaller turbo, electronically controlled wastegate, throttle retardation by the ECU) and that is what most of the efforts in the field for the past decade have been focusing on, but a turbo can not instantly deliver power because it needs to have time to build pressure from the exhaust gasses first; and that time is turbo lag.
Ah, you mean boost threshold.
Here's a review of the Bugatti Veyron:
Linky.
That's a car that makes 922 pound-feet of torque at 2200 RPM. Boost threshold really doesn't apply; and I really doubt he was cruising in 7th gear when he did that. And yet he is still describing hesitation in the throttle response. And that review is parroted by others who have also driven the car; most notable of them being Gordon Murray.
So how is it non-existent?
I don't think the first massive proliferation of turbocharged cars on the market is an "extreme", and you're still describing boost threshold anyway.
You mean the boost threshold. And you can perform those exact tests with normally aspirated cars, and I know this because based on the exact argument you're making I've seen people claim that cars with really peaky powerbands have turbo lag even when they don't have turbos.
There clearly is a disconnect because the words you put into his mouth are not even remotely like the words that he actually said.
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Please, instead of reading magazines, try driving turbo car yourself. IRL. Then the myths and 'knowledge' that you have will change and you'll accept the only real lag (which you call 'boost threshold').
Majority of normal road cars (and race cars as well) have good enough response at mid-range/high-range of rpms that the fictitious 'lag' you believe in - is non existent.
- 1,825
- California
EVERYBODY! STAHP ARGUING ABOUT WHAT THE THREAD IS ABOUT (turbo lag v. boost threshold)!
So I guess it can be assumed that this thread has turned to turbo discussion, which can be done elsewhere. Should I ask for a mod to close it? `Cause this is the epitome of off-topic.
So I guess it can be assumed that this thread has turned to turbo discussion, which can be done elsewhere. Should I ask for a mod to close it? `Cause this is the epitome of off-topic.
- 7,526
- Exorcet
- OE Exorcet
That is turbo lag. And since the turbo RPM and engine RPM are independent, you can have turbo lag at any RPM. You're saying that if the engine is revving enough, the Turbo will instantly go from low speed to max RPM. That's not possible.
He's describing real turbolag, which you are confusing with threshold.
The throttle can't be closed? What about when there is no one pushing the gas pedal, like what happens before a corner.
That modern cars have low lag does not make it fictitious. At least in someways you're getting closer to correct with this statement.
You might do well reading magazines before the next time you get in a turbo car so you can understand what the car is doing. You may or may not have real life experience, but it isn't helping you at all.
- 1,460
- England
Whilst I agree, it is slightly OT, if people can't understand the difference, then how can they know what you are asking for?
I notice you changed the title, so if the thread is now asking for both cars with lag, and cars with an exceptionally high boost threshold, then it would be beneficial for all to understand the difference.
Please. I'm not here to try and convince you. If you want to be ignorant, go for it. On the other hand, you could concede and learn somthing.
Whilst I agree, many modern turbo engines dint suffer from extreme lag, it is minimal compared to older turbo cars.
But, does the existence of modern cars mean all old cars disappear? No. I was in an Escort RS turbo less than 10 minutes ago. It suffers from turbo lag, and has a boost threshold of about 2.5k..
If modern cars do not suffer from turbo lag, or if it is completely fictitious, why does the latest range of WRC cars still have anti-lag systems?
Anti lag systems will not affect Boost threshold on their own. But in conjunction with air injectiors it might help a little.(I know sweet FA about the ins and outs of anti - lag, I have researched it, but most of the specifics I don't remember)
I only referred to the magazine article, as it's something you can go and get right now, and have a little read.
Alternatively, contact ANY reputable turbo supplier/specialist and ask them.
Turbo dynamics: http://www.turbodynamics.co.uk/contact-us/
CRturbos: http://www.crturbos.co.uk/index.php/about/contact-us/
I'm done arguing. Carry on mate 👍
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Let's shed some light here.
There are three (different) things we are talking about and they are all related:
1) the time between the moment you press on the throttle and the moment rpms start to rise.
2) the time between the moment rpms rise slow and the moment rpms start to rise fast.
3) the point in rpm range, above which rpms rise fast. This is what you call 'boost threshold'.
When you say 'lag' you mean first thing and when i say 'lag', i mean second thing (and you think it's the third thing or whatever).
The first issue is almost non-existent. You press throttle and you get instant reaction. That reaction may be very weak (if it's below 'boost threshold'), but it's still a reaction. The engine won't wait '1-2seconds' to do something...it will start making power right away. Maybe the increase in power will be slow, but nevertheless it will start 'doing the job' instantly.
The second issue is what matters most. You press throttle (and you get instant response), but the rise of rpms is very slow. You have to wait and wait until you 'feel' something and this feeling is the rapid increase of rpms. Not just increase, but rapid increase. It happens when rpms rise above 'boost threshold'.
The delay from first issue might be ~0.2sec or so. I don't know exact numbers but it is almost instant. No matter at what rpms!
The delay from second issue might be 2-4 seconds or more, depending on the size of the turbo. The bigger the turbo, the higher is 'boost threshold' and the longer you have to wait for full boost to arrive.
What all engine manufacturers want is to lower the boost threshold a.k.a 'issue no.2' and that's why WRC cars have anti-lag systems. The anti-lag works by creating extra exhaust gasses and making turbo spin at it's maximum (or so) rpms all the time so that when you need power it's already there, you don't have to wait for engine rpms to rise.
That's why there are twin-turbo systems: to reduce lag. Which lag? The time it takes to reach full boost, e.g. from 1k rpm to 2.5k rpm in your case (not the 'throttle response time').
Try driving with your Escort RS at 3500rpms, in 2nd or 3rd at a steady speed and then press the throttle. You'll notice reaction instantly. There won't be any lag. Because you're above boost threshold and there is no 'issue no2'.
- 4,992
- Nowhere special
- SweetLilPoppet
- SweetLilPoppet
Jeremy has mistaken a high threshold for lag. Does that evo actually have lag then?
- 4,992
- Nowhere special
- SweetLilPoppet
- SweetLilPoppet
- 1,460
- England
I'm no expert. I don't pretend to be.
I have read the rest of your post and I can agree with some of it.
But you are under the impression that pressure (any pressure), can jump from one value to another (much higher) value.
It doesn't.
Pressure must build. This can be slow or fast, but either way, there is a 'lag' between you hitting the pedal, and the car producing full boost.
I have read the rest of your post and I can agree with some of it.
But you are under the impression that pressure (any pressure), can jump from one value to another (much higher) value.
It doesn't.
Pressure must build. This can be slow or fast, but either way, there is a 'lag' between you hitting the pedal, and the car producing full boost.
- 4,992
- Nowhere special
- SweetLilPoppet
- SweetLilPoppet
The thing is though both me and you know what you are saying is correct, and it is, and yzf is making snide and unfair remarks to you like "you don't know what you're saying" and "oh please, go drive a real turbo car", and it's not fair that he's saying that, especially when you're correct, which to be fair, is only going to make him look super silly in the long run. Enough please with mean comments!
- 11,660
- GTP_Orido
Both GT5 and GT6 IMO have faulty boost gauge 
- 376
- Kingston, ON
- Phillguy
So I gather from this argument that:
1:Turbo lag is the time it takes for the turbo to reach full(ish) boost when the RPMs are above threshold when the throttle goes from nothing or almost nothing to open.
2:Turbo threshold is the lowest optimal engine RPMs for the turbo to reach full(ish) boost. Below this acceleration is slow regardless of total HP.
I think the OP was asking for Turbo threshold not Lag as in my humble opinion lag is almost imperceptible in most of the GT franchise.
Nuff said....
A stock F40 has slow turbo, a Supra (the RZ?) is terrible a low RPMs. The turbo kicks in like a mule. The Pagani Huayra also is bad at low RPMs.
1:Turbo lag is the time it takes for the turbo to reach full(ish) boost when the RPMs are above threshold when the throttle goes from nothing or almost nothing to open.
2:Turbo threshold is the lowest optimal engine RPMs for the turbo to reach full(ish) boost. Below this acceleration is slow regardless of total HP.
I think the OP was asking for Turbo threshold not Lag as in my humble opinion lag is almost imperceptible in most of the GT franchise.
Nuff said....
A stock F40 has slow turbo, a Supra (the RZ?) is terrible a low RPMs. The turbo kicks in like a mule. The Pagani Huayra also is bad at low RPMs.
- 3,211
- Brisbane
- Punknoodle_Nick
I really need to film the boost gauge, the tachometer and my accelerator at the same time in my car and explain what is happening at different stages of acceleration. I feel it would help this thread.
Turbo lag above boost threshold does exist in real life, even modern cars with modern aftermarket ECUs and professional tuning using aggressive ignition timing to try and reduce it.
If I'm above boost threshold but off throttle, and the engine is in vacuum, or even at atmospheric pressure and I nail the throttle, the turbo has to build boost, it takes time to get to the 16psi which is full boost in my case. This is shown clearly by the boost gauge needle moving gradually as opposed to just jumping straight to 16psi when I mash the throttle.
It really is simple physics.
Turbo lag above boost threshold does exist in real life, even modern cars with modern aftermarket ECUs and professional tuning using aggressive ignition timing to try and reduce it.
If I'm above boost threshold but off throttle, and the engine is in vacuum, or even at atmospheric pressure and I nail the throttle, the turbo has to build boost, it takes time to get to the 16psi which is full boost in my case. This is shown clearly by the boost gauge needle moving gradually as opposed to just jumping straight to 16psi when I mash the throttle.
It really is simple physics.
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- PNW
- Zenmervolt
You have completely misunderstood. Not one single person in this thread has talked about #1. No-one.
If you are above the boost threshold and cruising at a steady RPM, the turbo is loafing along at perhaps 10,000 RPM or so and is not producing boost. This is true even if the engine is WELL ABOVE the point where, if it were at wide-open-throttle, the turbo would be producing full boost and spinning at over 100,000 RPM.
When you are in the above steady-state condition and suddenly open the throttle fully, there is a 1-2 second delay before the turbo produces any meaningful boost because the compressor and turbine wheels have to spin up to ~100,000 RPM and that cannot happen instantly.
During this delay, the engine does indeed technically start producing more power, but, because it does not yet have boost (because the turbo takes time to spin up despite the RPM), this increase in power is negligible and there is much less acceleration. This reaction is weak EVEN IF THE ENGINE IS WELL ABOVE THE BOOST THRESHOLD.
That is turbo lag. The delay between when you open the throttle and the time at which the engine's full power is available. This is what everyone, myself included, has been saying from the start.
This is different from naturally aspirated and supercharged engines because on those engines there is no such delay; full power is always immediately available and there is no two-stage delivery as there is with a turbocharger.
This effect is most exaggerated in high gears because the engine's weakness when off boost is not compensated for by the increased torque multiplication in lower gears. However, the effect remains present even in lower gears.
This is flat out wrong.
At a steady speed, even in low gears, the turbo is still not producing boost when you're just sitting at a constant RPM with the throttle mostly closed (as you would have to be to hold a constant 3,500 RPM in 2nd or 3rd gear). There will still be a delay while the compressor and turbine come up to full speed and the engine will still be soft for a moment before the boost comes on.
This is the delay to which I alluded when I mentioned low-speed 2nd-gear corners. With a turbo car on a race track, you are always getting on the throttle out of a corner slightly before the point at which you actually want the power. You do this because you have to account for the time it will take for the turbo to come back up to speed after having slowed down during corner entry and the practical result is that you're usually on the throttle a half-second or so before you actually want full power.
If you misjudge this, you don't immediately know (as you would with a naturally aspirated or supercharged car) because when you initially apply the throttle the turbocharged engine's response is soft since there's nowhere close to full boost, DESPITE BEING ABOVE THE BOOST THRESHOLD. With a naturally aspirated or supercharged car, you'd notice the back end start to slip immediately and would have more time to back off in reaction. With a turbocharged car, everything seems great for a moment until the turbo comes back up to speed, at which point the engine's power increases suddenly and dramatically and, if you were just a bit too early with the throttle, you end up facing the opposite direction.
Remember, the amount of boost provided by a turbo is dictated mostly by the amount of throttle opening. RPM is merely a secondary variable. Throttle opening has far more effect on the amount of boost produced than simple RPM. Boost threshold is only really applicable at wide-open-throttle ("WOT"). Under part-throttle conditions, especially steady-state cruise at relatively low RPM (and 3,500 RPM is relatively low), the turbo is loafing along, making no real boost (indeed, the intake manifold will register a vacuum and not positive pressure in these situations) and spinning at perhaps ~10,000 RPM. To make boost, the turbo needs to be spinning at ~100,000 RPM.
Obviously, it's not physically possible for the turbo to "instantly" increase its rotational speed by a factor of 10, and the delay between the time the throttle goes wide open and the time the turbo has finally reached. Because of this, there is a moment where the engine has much less than rated power. This moment is lag.
That lag exists even in the lower gears. It is less noticeable because the lower gears provide more torque multiplication and the difference between off-boost and on-boost acceleration is less extreme than it is in higher gears, but the lag remains.
- 3,211
- Brisbane
- Punknoodle_Nick
Except the bit where you say that in turbo cars you accelerate before you would in an N/A vehicle to anticipate the boost response. This isn't always the case - I've been in quite a few high capacity turbo vehicles and the throttle response off boost is just as savage as a lot of N/A vehicles! The turbo just adds another level of insane on top, one that you had better he aimed in a straight line for!
Punk, he meant his very particular case, wich probably a combination of big turbo, large diameter exhaust pipes, long pressure lines, low compression ratio, low displacement. Modern cars learned their lessons and improved all the above aspects.
Throttle response is imediate because your car is turned on... Modern regular cars have tiny turbos, wich by design are made to lessen to the biggest extent turbo lag, trying to make the engine feel normally aspirated. They have max boost at low rpm and cannot hold that same boost all the way to redline.
Stock turbo+tune
Golf R turbo(on a gti)+ tune
Stage 3 turbo
In all takes from a split second, to a few seconds to spool up.
The 2014 f1 cars will bring one of the biggest innovations in turbo, wich is an eletric motor to spool the turbo and avoid the lag.
Throttle response is imediate because your car is turned on... Modern regular cars have tiny turbos, wich by design are made to lessen to the biggest extent turbo lag, trying to make the engine feel normally aspirated. They have max boost at low rpm and cannot hold that same boost all the way to redline.
Stock turbo+tune
Golf R turbo(on a gti)+ tune
Stage 3 turbo
In all takes from a split second, to a few seconds to spool up.
The 2014 f1 cars will bring one of the biggest innovations in turbo, wich is an eletric motor to spool the turbo and avoid the lag.
