Turbo Lag? fact, or fiction - stock vs tuned - or just TCU?

[RudyH]

This is actually a question for both 8V and 8Y owners...how bad is it?

I have been spending some time watching videos to preoccupy myself in my wait. One item though that keeps popping up, especially when comparing the 8Y RS3 to say a MK8 R, is the turbo lag. I know we are talking about only 0.5L of a displacement difference and over 100hp, so something needs to give. Other articles mention its no different then previous version of the RS3.

Most of my driving is city, with the odd quick sprint from a slow roll. Highway, I find Dynamic mode always keeps the revs a bit higher.

I must say that I am pretty sure my 8Y S3 has turbo lag, more then my Stage II MK7.5 R did (mind you it was 6MT with a hefty clutch). I only say that because I find it sluggish and not sure if it's the TCU hunting for what its supposed to do, is the TCU being too protective, or if its turbo lag. With the 8Y.5 S3 facelift, I noticed that Audi uses a 'pre-loaded turbo to reduce this, so I think this is more the issue then anything. Of course that is something to be determined. The lag seems more evident with the low torque Stage I ECU tune I have, but also power is being cut for the fact the TCU won't allow it.

Question a bit more towards the 8V's, is this fixed with an ECU tune? I noticed too that Iroz Motorsports mentioned too that they got the ECU tuning side of things going, but are looking forward to getting things a bit more sorted out with the TCU. Wondering if that's more so the issue.

[HODL_B58]

I’ve been curious as well, when I was stock/jb4 I remember there being some turbo lag but don’t remember it being so bad, but probably still more lag on stock turbo than my B58 on a Borg Warner full frame. Now that I’m tuned on a 750hs the turbo lag seems unbearable, from a stop it takes about 3 seconds to build boost so just about any car on the road can beat me 0-15MPH assuming I’m not launching. Tuner comes this week so hope I can make it better, idk. Now I see why 75% of RS3 sellers were upgrading to a M3, even on the big HP builds, one less cylinder seems to really add a lot of lag.

How long/what RPM/at what MPH are you hitting boost? I never took a log on jb4

[robotvoice]

I only have about 1k miles on my 8Y but I think the stock transmission tune leaves a lot to be desired. I appreciate the comfort/auto modes for more laid back or traffic heavy driving (a bit improved over the 8V IMO) but even in auto you have to absolutely bury the pedal to get back up to speed and then I feel like the TCU over compensates too late and now you're revving like crazy after you already passed someone and are slowing back down again.

The turbo lag is noticeable but definitely not as much of an issue for me in manual mode since it's easier to keep the car in the power band. The turbo lag is less of an issue to me than the poor TCU programming logic out of the box.

I think a nice ECU/TCU combo tune that complements each other would be a game changer for the 8Y once it's available.

[Cyrus27]

My non-engineer take (from someone who replaced a MK7 Golf R with the 8Y RS3): The RS3 has way more lag and in auto mode, the engine/transmission combo is a bit of a mess. The Golf R is far smoother.

[Jetdriver]

I don't notice much turbo lag, but then again, I don't lug the engine. If I'm in D, just cruising around, I'm not really concerned about turbo lag anyway. In S or M, there is very little lag if you're up over 2k RPM.

I am on a JB4, map 6 with e30, but I didn't notice much lag stock either. This isn't a turbocharged engine of the 1980's.

The TCU could use some tuning.

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[DrMerl]

Of course there's lag. The stock turbo used to be a fairly large size (like an old Garret GTX) for 2 liters, the extra half liter helps, but stock turbo doesn't shine until around 3200-3500 rpm. Once you're on boost and keeping the RPMs up there's no perceptible lag. Turbos are like cams, where do you want your torque? Low, med or high? Want high end power till redline, then low end is going to suck. It's nice we have all the fancy cam timing, turbo design, etc. to mitigate lag. There's a reason why you see so many vids of the DAZA taking the top end of a race. I prefer top end and change driving style to adjust for the lazy bottom. DAZA not a torque monster like S58. Annoying thing in traffic is the lag, need to get into a 60 mph gap and you're merging at 25mph, if you just mash it there's a wait, then the DAZA goes to warp speed - not very smooth, can be puckering in some situations. Adds more engagement in understanding how to use the power band =)

Not lugging the engine is key if you like Manual mode. This is still a "little" engine, I garner about 200 HP without boost. Keep the RPMs up if you want to zoom. Hair pulling doesn't start till 3400RPM.

A TCU tune will give you a crisper shifting picture, main purpose is to align with engine torque output. Doesn't do anything for lag except get you into the proper gear quicker. Improving lag is improving pressure differential (think waterfall). Exhaust side is usually first, DP, larger pipes, you generally build boost quicker by a few hundred RPM (and slightly lower EGT). You can help "lag" by dropping vehicle weight, sprung and unsprung. Ball bearing turbo centers will help slightly (some hybrids), good turbine engineering (Xona seems to be up there) with proper size selection. Audi gave us more thrills up top, aligns with the German "long legs" philosophy.

[Rguy]

Below about 2250RPMs this engine isnt making any worthwhile boost. There is a reason why sport modes keeps the revs high.

[AdamSheikh]

Of course there's lag. The stock turbo used to be a fairly large size (like an old Garret GTX) for 2 liters, the extra half liter helps, but stock turbo doesn't shine until around 3200-3500 rpm. Once you're on boost and keeping the RPMs up there's no perceptible lag. Turbos are like cams, where do you want your torque? Low, med or high? Want high end power till redline, then low end is going to suck. It's nice we have all the fancy cam timing, turbo design, etc. to mitigate lag. There's a reason why you see so many vids of the DAZA taking the top end of a race. I prefer top end and change driving style to adjust for the lazy bottom. DAZA not a torque monster like S58. Annoying thing in traffic is the lag, need to get into a 60 mph gap and you're merging at 25mph, if you just mash it there's a wait, then the DAZA goes to warp speed - not very smooth, can be puckering in some situations. Adds more engagement in understanding how to use the power band =)

Not lugging the engine is key if you like Manual mode. This is still a "little" engine, I garner about 200 HP without boost. Keep the RPMs up if you want to zoom. Hair pulling doesn't start till 3400RPM.

A TCU tune will give you a crisper shifting picture, main purpose is to align with engine torque output. Doesn't do anything for lag except get you into the proper gear quicker. Improving lag is improving pressure differential (think waterfall). Exhaust side is usually first, DP, larger pipes, you generally build boost quicker by a few hundred RPM (and slightly lower EGT). You can help "lag" by dropping vehicle weight, sprung and unsprung. Ball bearing turbo centers will help slightly (some hybrids), good turbine engineering (Xona seems to be up there) with proper size selection. Audi gave us more thrills up top, aligns with the German "long legs" philosophy.

This. Recent GTI and R models have loads of torque right away (from 1800rpm or so), so turbo lag is almost imperceptible in day to day driving. The 2.5T has more of an "old school" feel and needs some revs to stay in the power band and on boost. Around town and at slower speeds it may feel a bit lazy in comparison, but it has way more poke on boost and feels much more dramatic in how it delivers power. Not to mention how strong it pulls all the way to redline and how effective it is at medium to high speed cruising (highway/autobahn). It's part of the charm of this powertrain IMO.

[djn876]

Turbos need a certain amount of exhaust flow in order to spool, the bigger the turbo is, the more flow it will need, this is most often what is perceived as "lag". This engine isn't doing much power wise under 3k RPM, and by 4k it's very happy. Smaller displacement engines cant produce as much flow and generally have turbos built to help with lower end torque that spool faster (generally smaller in size). Those turbos tend to die off though at higher RPM as they aren't efficient at those turbine/compressor speeds, so it's a trade off. With this engine having 5 cylinder and a little more displacement, it can tolerate a bigger turbo that doesn't need to provide as much low end torque for daily driving.

That's why the folks running huge turbos making 1000 HP are making it all above 5k RPM, it's not a street friendly setup.

That being said, if you keep the RPMs above 3k, you won't have any appreciable delay in power application, it's all in keeping the engine where the turbo will be able to do it's job properly, that more or less eliminates any real "lag" or turbo spool time. I almost prefer manual mode for the transmission just to ensure it's ready to go. RS mode I've never really had an issue with either, but sometimes even dynamic shifts too early IMO.

Coming from a 3.0T motor it was a huge change in the way I needed to drive the car. That engine with the supercharger made so much torque everywhere you could be pretty lazy driving it. With this one you have to be more engaged in keeping it in the powerband.

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[Jetdriver]

That being said, if you keep the RPMs above 3k, you won't have any appreciable delay in power application, it's all in keeping the engine where the turbo will be able to do it's job properly, that more or less eliminates any real "lag" or turbo spool time. I almost prefer manual mode for the transmission just to ensure it's ready to go. RS mode I've never really had an issue with either, but sometimes even dynamic shifts too early IMO.

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Amen. Anyone driving a 2.5L motor around below 2,000 RPM expecting there not to be turbo lag doesn't know how to drive small displacement turbo-charged cars. I've been driving these types of cars for the last 15+ years; mainly 4-cylinders. Even after I tuned them, they didn't go anywhere under 2,500 RPM. If I got caught in the wrong gear, I was dead in the water. With the RS3, you can get away with 2,500 RPM. Nail the gas here and you're not going to get much lag. Nail it at 3,000 and there's pretty much no lag at all. Anything above that and it's just off like a freight train.

[DrMerl]

The butt-dyno effect. Few hundred ft/lb of torque at low RPM is plenty to creep around, but when you get on boost and it doubles or triples, you start thinking why is it so slow down low?

[hberg002]

My take coming from 8V to 8Y RS3 is that Audi tried to alleviate the turbo lag in the 8Y by letting it build/hold boost at lower RPMs and cruising. From what I can remember, the 8V on stock tune wouldn't register much or any boost when just cruising around on the street or highways. On the 8Y, you notice that the car is making boost (holding wastegate closed or almost closed) when just cruising around. This definitely helps when you need that last minute passing power.

On the 8V, the best daily driving tune I experienced was DS1 ECU and TCU, tuned by Darin. I would suggest asking him for a non-amax TCU tune for daily driving just so you can have both options. Here the TCU tune made the biggest improvement. I was finally able to leave the car in Dynamic and Auto without worrying about it holding gears too high and for too long when cruising around town.

On the 8Y, the added performance modes help "Dynamic" mode not be so aggressive in holding RPMs. It also downshifts at an acceptable rate when you need extra passing power. If you use the performance modes, they hold gears way too much for street driving, but Dynamic is pretty good on my opinion for stock tune. I'm sure improvements will be made once tuning becomes available.

The 5 cylinder + DQ500 DSG drivetrain has its quirks, and you do have to adjust your driving to get around this "lag." As long as you can accept that you'll be fine. Easy fix is driving it mostly in Manual mode and downshifting a gear or two when you need the power.

[Crowlski]

I only have about 1k miles on my 8Y but I think the stock transmission tune leaves a lot to be desired. I appreciate the comfort/auto modes for more laid back or traffic heavy driving (a bit improved over the 8V IMO) but even in auto you have to absolutely bury the pedal to get back up to speed and then I feel like the TCU over compensates too late and now you're revving like crazy after you already passed someone and are slowing back down again.

The turbo lag is noticeable but definitely not as much of an issue for me in manual mode since it's easier to keep the car in the power band. The turbo lag is less of an issue to me than the poor TCU programming logic out of the box.

I think a nice ECU/TCU combo tune that complements each other would be a game changer for the 8Y once it's available.

I think you are more likely experiencing the lag in the gas pedal than turbo lag while in comfort mode. This is why I run a pedal optimizer. You still get the softness of comfort mode but a bit more throttle response with the optimizer. Fully adjustable too.

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[djn876]

I think you are more likely experiencing the lag in the gas pedal than turbo lag while in comfort mode. This is why I run a pedal optimizer. You still get the softness of comfort mode but a bit more throttle response with the optimizer. Fully adjustable too.

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Those devices just change how the electronic signal ramps in, it's not a delay in response from the pedal stock. In comfort or auto, it likely ramps in slower than in dynamic or sport mode, where it will likely be more linear. Ultimately you get the same effect just pushing the pedal down more, but if you like the mapping then go with it.

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[IanCH]

Lotta random numbers being thrown around here... people making things up on the internet? No way!

2800 is in the boost stock, below that you're not getting anything. There's no denying the turbo has lag but the top end being all the way up at basically redline mean its functionally no lag.



Compare to a IS20 turbo that makes it down low but loses it up top. Power band 2300-5600

(6800-2800) > (5600-2300)

Only way to get both is to twin turbo it, like the BMW engines. Having full top end and a lower boost bottom end is the best you can hope for on single turbo.

[djn876]

Lotta random numbers being thrown around here... people making things up on the internet? No way!

2800 is in the boost stock, below that you're not getting anything. There's no denying the turbo has lag but the top end being all the way up at basically redline mean its functionally no lag.



Compare to a IS20 turbo that makes it down low but loses it up top. Power band 2300-5600

(6800-2800) > (5600-2300)

Only way to get both is to twin turbo it, like the BMW engines. Having full top end and a lower boost bottom end is the best you can hope for on single turbo.

This looks to me like what most of us are saying. 3k RPM and you are more or less maxed out on torque and power is pretty well built in by 4k....the graph is helpful to visualize though.

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[robotvoice]

I think you are more likely experiencing the lag in the gas pedal than turbo lag while in comfort mode. This is why I run a pedal optimizer. You still get the softness of comfort mode but a bit more throttle response with the optimizer. Fully adjustable too.

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It's not a lag in the input from the pedal but more a combination of having to push the pedal down more than I would have expected plus the transmission trying to calculate what to do and then over revving because the tune logic isn't really optimized. I hate anything that messes with throttle feel anyway as it usually gets way too sensitive. Not a huge deal as I lean towards driving this car more in manual mode now anyway which feels great.

[S3DUDE]

In my honest opinion the RS3 8V and 8Y have a decent amount of turbo lag. At the end of the day the turbo is basically a 7163 which in some other car platforms it is a big as a turbokit for Subaru for instance, I refer to BorgWarner EFR 7163 for instance.
I had a a 8V S3 before, stock at first then tune and I also had the 8V RS3 in stock form and tuned on 91 oct and E-85. The most significant differenece is the E-85 tune on the RS3 because it transforms the way the car responds. Throtle is almost instant and the power is like: Now!!.

The S3/Golf R mounts the IS38 turbo but the 2.0l engine is very efficient and responsive in the midrange. I said it in the past and many other owners have also said it the S3 in my oopinion has better characteristic(response) in the midrange but just dies up around 6000 rpm. I took my 8Y RS3 stock) to a small racetrack with tons of slow turns and the turbolag was killing it, I had to let go of the gas and press on the gas again and the response was mediocre.

In summary, yes the RS3 has some turbolag but it also has a ton of torque and even though you said that you will be driving in traffic you wouldn't noticed it because the car has plenty of torque. If you drive it on S mode it will also help a lot. Don't overstress the turbolag, buy the car it is a great car. If you want to be shoved on your seat just buy a M2/M3/M4, these engines have an incredible amount of response.

[Crowlski]

Those devices just change how the electronic signal ramps in, it's not a delay in response from the pedal stock. In comfort or auto, it likely ramps in slower than in dynamic or sport mode, where it will likely be more linear. Ultimately you get the same effect just pushing the pedal down more, but if you like the mapping then go with it.

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Yeah I see what you are saying but I do like the quicker response while driving in Comfort mode. The drawback on the optimizer is it can get a little jumpy or jittery if you dial up the sensitivity too high.

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[TheContrarian]

RS3 8V with stage 1 ecu tune and car in S mode, I find the lag off idle to be tolerable. My wife's SQ5 with stage 1 ecu definitely has more thrust off of idle.

B9 RS5 EA839 using twin turbos and air-to-water intercooling is how to create a powerful top end with better daily driving characteristics.

[RudyH]

Thanks for all the feedback! All the comments were very useful, and definitely helps

I think looking at the dynos are helpful, just using an Unitronic dyno....for no reason but looking at it.

MK8 Golf R Stock vs Stage I overlay:
It seems like they are pulling up to like ~2.4k, where pulls harder on stage I to that ~2.6k, going with a bigger turbo pushes that way out (APR has a GTX 2563S that's out in the 4k)


8V RS3 Stock vs Stage I overlay: (interesting Unitronic took down their 8Y page...)
It seems like they are pulling stock up to ~2.6k, where pulls harder on stage I to that ~3kish


Obviously yes comes to the turbo, and possibly the MK8.5 / 8Y.5 being a little more responsive

Loosely, I had been looking at it from a power perspective as something like:
stock 2.0T < stage I 2.0T ~ stock 2.5T < stage II 2.0T < stage I 2.5T < stage IIIish 2.0T < stage II 2.5T

Even with the 2.0T I drive in S because of lag, but I guess if I had to put it all into a statement - 'if you go to stage III 2.0T and want to daily drive, you might have been better off sticking with the 2.5T'.
For me I generally stop at Stage II anything, but with the 2.0T and cost savings, I was weighing 'well I could go Stage III 2.0T' but will it be as good as a stage II RS3...likely not!

***edit

wanted to add one more thought...the RPM's that the max torque is being generated in either case...2.6kish is that sweet spot for both making similar power...