Turbos run on engine load... specifically fuel consumption.. The more load, the more fuel air is burned per second to create a specific volume of exhaust gas. You can be under high load at low rpms (highway driving) and the turbos are ready to light off, You can be at high rpm under little to no load and the turbos are barely spooling.. It is the exhaust gas volume (and pressure differential across the turbo) that determines lag.
Really nice video, I wanted to fact check what I knew about turbo lag, well I did not learn much from your video because I already figured it out myself by thinking about how the turbo work (also already knowing how anti lag work give big clues), but it was still really informative, both to see in action with your car and the curve figure you gave as example, so thanks ! Basically what I thought is that to make the compressor of the turbo spin you need power because the whole goal of the turbo is to pump more air into the pistons, which need a sufficient air flow rate but also pressure. Power is literally strength * speed, in the engine it translate to both RPM which basically dictate how many time per seconds there is an exhaust stroke, and strength of the explosion which translate to the quantity of air/fuel mixture there is, but they are all dependent as RPM multiply the number of each explosion each seconds and the more load put on the engine, aka the more powerful are the explosion, and the more total power of exhaust per seconds * exhaust pressure there will be. Also there is the turbo itself where the more boost it already provide, the more air/fuel it can push into the engine and the more powerful the explosion get, increasing RPM (because it create more torque which make the car accelerate faster) and also the exhaust pressure per explosions because of the artificially increased volume. Which mean that both low RPM and heavy load and high RPM and low load have approximatively the same effect, while heavy load at high RPM is what spool the turbo the most. While the turbo itself have two components, its speed and the pressure it produce, while the more RPM the engine have the more RPM the turbo require to push enough air by quantity, the stronger the exhaust spin the turbine, the more the turbo compressor can generate pressure. And the turbo need time to acquire the needed RPM to match the engine RPM depending on the strength and frequency of the exhaust stroke, but also during heavy engine load, the turbo constantly force against the pressure it create, making it spool slower than if it did not pushed air into the engine, but if it was the case the engine would simply get a giant kick when the turbo pressure would be directed at the engine, and while building RPM the turbo already help the engine to produce more torque. The pressure itself is almost instantaneous to build unlike RPM, which is why valves have great benefits by reducing the pressure between the turbo and the engine during low load, making the turbo spin freely as opposed to forcing against its own pressure. So the good old violent turbo lag experienced in the 90's was, as I deduced, because the turbo needed higher RPM at high load compared to modern turbo to get enough RPM to generate enough airflow and pressure to feed the engine, which mean those old cars lack the benefit of the turbo at low RPM even under heavy load, and when the turbo started to spool while generating enough pressure, it quickly escalated within the self feeding loop of "more boost = more volume = stronger explosions = more torque = more boost" getting from a naturally aspirated torque figure to a charged one really quickly, which on the first gears was pretty violent. Also I thought about twincharger, and I quickly realized that when at low load, when the supercharger had no benefits, using a bypass its pressure could be used to keep the turbo at high enough RPM, and when accelerating the bypass quickly revert the supercharger pressure to the engine, giving normal supercharger low RPM benefits and while the turbo itself also having a blow off valve (as a recirculating one would generate pressure which would contribute to turbo RPM loss) electronically opened to keep its RPM high, and then at a certain engine load the BOV would close, having a turbo already spool to match the current engine RPM and both turbo and supercharger would push while engine RPM increase and the supercharger slowly loose the lead over the turbo (as turbocharger give more power at high RPM and high load than superchargers). When near redline we shift to the next gear, the turbo BOV would be open and the supercharger bypass would push its pressure to the turbo, reducing the RPM loss during shifting, but more interesting, during downshift (approaching a corner for example) while the engine operate at low load but still peak in RPM at each downshift, the bypass could help the turbo keeping high RPM. It could be an interesting alternative to anti lag. The supercharger would give more torque at low RPM and have instant response from low to high load, it would allow for higher low RPM torque and shorter turbo lag for high RPM conditions, but this would obviously be only interesting for performance only. That's my analysis of it, but I only figured it out in my mind and haven't fact checked it (apart from your video).
Nice video, well explained. You can look into n249 system that audi introduced in 1.8T long time ago. exactly to reduce that lag. Sometimes it feels like n/a engine if turbo is already spooled with a help of n249 (when you step on throttle, then release it and step again quickly, or gear changes on wot). Amazing feeling of instant power. That is biggest turbo engine flaw, spool is somewhat fun, but lag in whole rpm range is not, even 0.2s is felt and big difference to experience in driving and with throttle response.
I get a loss of power at around 70/80 is S7 when I floor it. I think it’s due to the fact it can’t change down quick enough. Have you noticed this? Audi say there is nothing wrong with it. I’ve had 3 RS3 and they’ve all done the same
I believe ECU and TCU tunes do help somewhat, but it's honestly negligible. The car is trying to be somewhat 'smooth' and engage the clutch at the right time. If you want the best possible launch, use launch control.
@@jutjub22 it's the first forced induction car that I own, my family has over 10 cars and it's all either N/A or supercharged, I've driven and felt instant power
@@gazamisheawoh They did good job, big 3litres engine with small twin-scroll turbo, so you have almost non existent lag - But why would you want to feel more lag, there is nothing good about it. Do stage 1, and you will have stronger punch when boost comes on, at boost threshold (spool from low rpm is fun in turbo car, but lag is not :) ). For example, this RS3 on the video is 2.5Litres, but turbo flows up to 500-550HP, so, much more lag compared to yours (but more power too)
@@KoryNunn You know what, my comment might have been a little cheap. I really should have said that it was a little long, and doing it while driving meant your attention was somewhere else. I did not finish the video.
@Kory Nunn Hey Kory, appreciated the vid, just curious whether there’s any other type of lag in the throttle response, say the moment you put your foot down - the car pulls. I ask cause some electronic throttle cars have a hesitation before the ECU will ramp up the engine, this could be due to traction control, protective mechanisms for the drivetrain, safety systems, poor/delayed engine-trans communication or just crappy programming. How do you find the RS3 in this? Same as a hard wired throttles from the previous gen cars? Thanks !
It's not as immediate as a cable throttle but it's fairly good. My gt86 has much worse throttle damping, which annoys me significantly. Honestly I'm not sure if there is any damping once you are moving, because if you jab the throttle it will lurch violently just like a cable throttle.
Turbos run on engine load... specifically fuel consumption..
The more load, the more fuel air is burned per second to create a specific volume of exhaust gas.
You can be under high load at low rpms (highway driving) and the turbos are ready to light off,
You can be at high rpm under little to no load and the turbos are barely spooling..
It is the exhaust gas volume (and pressure differential across the turbo) that determines lag.
Really nice video, I wanted to fact check what I knew about turbo lag, well I did not learn much from your video because I already figured it out myself by thinking about how the turbo work (also already knowing how anti lag work give big clues), but it was still really informative, both to see in action with your car and the curve figure you gave as example, so thanks !
Basically what I thought is that to make the compressor of the turbo spin you need power because the whole goal of the turbo is to pump more air into the pistons, which need a sufficient air flow rate but also pressure.
Power is literally strength * speed, in the engine it translate to both RPM which basically dictate how many time per seconds there is an exhaust stroke, and strength of the explosion which translate to the quantity of air/fuel mixture there is, but they are all dependent as RPM multiply the number of each explosion each seconds and the more load put on the engine, aka the more powerful are the explosion, and the more total power of exhaust per seconds * exhaust pressure there will be.
Also there is the turbo itself where the more boost it already provide, the more air/fuel it can push into the engine and the more powerful the explosion get, increasing RPM (because it create more torque which make the car accelerate faster) and also the exhaust pressure per explosions because of the artificially increased volume.
Which mean that both low RPM and heavy load and high RPM and low load have approximatively the same effect, while heavy load at high RPM is what spool the turbo the most.
While the turbo itself have two components, its speed and the pressure it produce, while the more RPM the engine have the more RPM the turbo require to push enough air by quantity, the stronger the exhaust spin the turbine, the more the turbo compressor can generate pressure.
And the turbo need time to acquire the needed RPM to match the engine RPM depending on the strength and frequency of the exhaust stroke, but also during heavy engine load, the turbo constantly force against the pressure it create, making it spool slower than if it did not pushed air into the engine, but if it was the case the engine would simply get a giant kick when the turbo pressure would be directed at the engine, and while building RPM the turbo already help the engine to produce more torque.
The pressure itself is almost instantaneous to build unlike RPM, which is why valves have great benefits by reducing the pressure between the turbo and the engine during low load, making the turbo spin freely as opposed to forcing against its own pressure.
So the good old violent turbo lag experienced in the 90's was, as I deduced, because the turbo needed higher RPM at high load compared to modern turbo to get enough RPM to generate enough airflow and pressure to feed the engine, which mean those old cars lack the benefit of the turbo at low RPM even under heavy load, and when the turbo started to spool while generating enough pressure, it quickly escalated within the self feeding loop of "more boost = more volume = stronger explosions = more torque = more boost" getting from a naturally aspirated torque figure to a charged one really quickly, which on the first gears was pretty violent.
Also I thought about twincharger, and I quickly realized that when at low load, when the supercharger had no benefits, using a bypass its pressure could be used to keep the turbo at high enough RPM, and when accelerating the bypass quickly revert the supercharger pressure to the engine, giving normal supercharger low RPM benefits and while the turbo itself also having a blow off valve (as a recirculating one would generate pressure which would contribute to turbo RPM loss) electronically opened to keep its RPM high, and then at a certain engine load the BOV would close, having a turbo already spool to match the current engine RPM and both turbo and supercharger would push while engine RPM increase and the supercharger slowly loose the lead over the turbo (as turbocharger give more power at high RPM and high load than superchargers).
When near redline we shift to the next gear, the turbo BOV would be open and the supercharger bypass would push its pressure to the turbo, reducing the RPM loss during shifting, but more interesting, during downshift (approaching a corner for example) while the engine operate at low load but still peak in RPM at each downshift, the bypass could help the turbo keeping high RPM.
It could be an interesting alternative to anti lag.
The supercharger would give more torque at low RPM and have instant response from low to high load, it would allow for higher low RPM torque and shorter turbo lag for high RPM conditions, but this would obviously be only interesting for performance only.
That's my analysis of it, but I only figured it out in my mind and haven't fact checked it (apart from your video).
another good explanation to this is if you do a pull to 6k and let off, you will still have high revs that are slowly going down, but no boost
Can you feel the boost kick in at 3500rpm with a noticeable forward thrust?
Nice video, well explained. You can look into n249 system that audi introduced in 1.8T long time ago. exactly to reduce that lag. Sometimes it feels like n/a engine if turbo is already spooled with a help of n249 (when you step on throttle, then release it and step again quickly, or gear changes on wot). Amazing feeling of instant power. That is biggest turbo engine flaw, spool is somewhat fun, but lag in whole rpm range is not, even 0.2s is felt and big difference to experience in driving and with throttle response.
Awesome vid! Question: you’re a young lad driving an RS3 - are you a CEO or are you broke af?
Neither. Software dev, no debt on the car anymore. I wonder if people would care about a "Who am I" video.
I get a loss of power at around 70/80 is S7 when I floor it. I think it’s due to the fact it can’t change down quick enough. Have you noticed this? Audi say there is nothing wrong with it. I’ve had 3 RS3 and they’ve all done the same
Would a Throttle Control unit help with the initial take-off lag? (I am not talking about turbo lag, but TTRS still has a small lag at the takeoff)
I believe ECU and TCU tunes do help somewhat, but it's honestly negligible. The car is trying to be somewhat 'smooth' and engage the clutch at the right time. If you want the best possible launch, use launch control.
My 535i has no turbo lag but I wish it had a little, I guess that’s the benefit of using a twin scroll turbo
You have some, just it is minimal, you would feel difference if you try n/a car, which is instant.
@@jutjub22 it's the first forced induction car that I own, my family has over 10 cars and it's all either N/A or supercharged, I've driven and felt instant power
@@gazamisheawoh They did good job, big 3litres engine with small twin-scroll turbo, so you have almost non existent lag - But why would you want to feel more lag, there is nothing good about it. Do stage 1, and you will have stronger punch when boost comes on, at boost threshold (spool from low rpm is fun in turbo car, but lag is not :) ). For example, this RS3 on the video is 2.5Litres, but turbo flows up to 500-550HP, so, much more lag compared to yours (but more power too)
@@jutjub22 must be fun when you get a big surge of power, I might go stage 1
@@jutjub22 rs3 has about 390hp
Great explanation, thank you
9:58 you raced the scirocco?😅
My lawyers have told me to say "No"
@@KoryNunn 😑 you would have won anyway
What car do you drive?
Can't tell if this question is directed at me or other viewers. The thumbnail of the video shows the dash of my RS3.
It was for you aha, and thanks
Brilliant
So boring
Thanks mate. It was targeted at a more technical audience.
@@KoryNunn You know what, my comment might have been a little cheap. I really should have said that it was a little long, and doing it while driving meant your attention was somewhere else. I did not finish the video.
I didn't expect a massive amount of people to get through it. 22% average watch time at the moment, I'm surprised it's even that high.
@Kory Nunn
Hey Kory, appreciated the vid, just curious whether there’s any other type of lag in the throttle response, say the moment you put your foot down - the car pulls. I ask cause some electronic throttle cars have a hesitation before the ECU will ramp up the engine, this could be due to traction control, protective mechanisms for the drivetrain, safety systems, poor/delayed engine-trans communication or just crappy programming. How do you find the RS3 in this? Same as a hard wired throttles from the previous gen cars? Thanks !
It's not as immediate as a cable throttle but it's fairly good. My gt86 has much worse throttle damping, which annoys me significantly.
Honestly I'm not sure if there is any damping once you are moving, because if you jab the throttle it will lurch violently just like a cable throttle.