Datalogging and Performance

B6/7 S4/RS4
#1

Hi guys, I’ve got an 06 B7 RS4 that I’ve had for about 12 months now. The performance of the car has always felt a little flat. I did some datalogging in summer, and saw that a pretty huge amount of timing was being pulled from 3k to 8k. Putting it down to our very hot/humid summers here in North Queensland, I put the datalogging on hold until winter.

Well, I’ve just done some more datalogging the other night, where ambient temps were about 19degrees celcius. My 3k-8k times improved from 11.34s to 10.81s, but I’m still showing timing retardation, and those acceleration times seem to be pretty far off what is normal for a stock car.

What IATs are you guys normally seeing when the timing is not being pulled?

IAT for summer run was ~45deg C
IAT for winter run was ~24deg C

Car is 100% stock at the moment. Feels like everything is running well, and I can feel the torque increase at around 5k rpm.

I’m unsure whether the car has ever had a carbon clean, though I suspect it hasn’t. It currently has 150 000kms on it. Would carbon buildup increase the propensity for the timing to be pulled?

Be interested to get some other thoughts from people who have done a bit of logging.

Cheers.

PS: Here is a copy of the summer and winter logs: https://www.dropbox.com/s/cqo4h1j7imhd21g/WintervsSummerLogs.xlsx

#2

I really have no idea about the timing, but I would highly suggest having a carbon clean done if you are unsure. From what I have read, you’re symptoms of feeling “flat” sounds a lot like carbon build-up.

#3

The flat feeling I’m almost positive is a result of pulled timing. It feels worse when it’s hotter for sure. Also my feelings are likely off, as my other car is a tuned Evo VI, and this has a very different power delivery to the RS4. I was convinced that it was much quicker when I first purchased the car, but they are about neck and neck.

The problem with carbon cleaning as well, is the nearest workshop that could do it is about 1500kms away (yes, you read that right lol). So I’d have to find the time to pull off the inlet manifold and do it myself. Looking to rule out any other potential issues before going down that road.

#4

You have a ton of timing being pulled, esp in cylinders 3 and 4. Up to 11*. Almost no retard in cyl 2. Check ECU2 for cyl 5 - 8 also.

#5

I will bet a coke you have a vacuum leak. Perhaps a test would be in order.

For perspective, my car did 3k-8k last summer on a 28 celsius day in around 8.9 seconds. On a cold day it would do so in around 8.2-8.4 seconds.

Your performance is so far from that it is not carbon. It’s a vacuum leak.

Carbon might account for up to 20 hp. Mostly high end. On a 3k-8k maybe half a second. A vacuum leak can mean losing 60-80 hp for a good part of the curve.

#6

And with vac leaks you don’t always get a code. My S4 had a bad one, was slowing down my rpm/second by 10-15% without tripping a code

#7

I Can definitely do the vacuum test to know for sure, but I originally ruled that out as I thought the vacuum system was all linked, and the exhaust flap definitely works. Would a vacuum leak cause timing to be pulled? I can measure the other banks as well I suppose, but I’d be surprised if it wasn’t showing a similar amount of retard.

#8

Yeah, good to know beemercer. I found some other references on the net about leaks happening at high enough rpm so as to not trip a fault. Would also explain why exhaust flap seems to be working perfectly at idle, but might not be noticable at full noise/high rpm.

Only one way to know for sure… Vacuum test time this weekend :slight_smile:

#9

Is your car stock? There’s been a few threads on carbon and fuel filter replacement that I’m sure will help performance. The vacuum systems on our cars is very complex. There’s many vacuum pick-up points. So having one vacuum related item working isn’t an indication that there’s not a possible vacuum leak elsewhere.

#10

Good call on the fuel filter Hyden. The car is 100% stock at the moment. I want to make sure that everything is running to spec before starting down the modification path. At a 11s 3k-8k, I’m a long way off where the car should be.

Car is also going in for routine service next month, I’ll be doing fresh plugs and air filter, so I’ll get the fuel filter done as well. Wasn’t aware that the fuel reg is actually in the filter, so all the more reason to make sure it’s all running well. Also, it seems you’re spot on regarding the vacuum system. I’ve run across many different examples of the system “kinda” working when looking at components individually, but leaking in specific scenarios that can hurt power, but not be obvious from something like the exhaust flap working at idle. I’ll be running the vacuum leak test tomorrow so will see if everything appears to be actuating properly.

After spending so much time tuning and tweaking the Evo, I’m so glad that there is a good datalogging solution on the VAG vehicles so we can get good, repeatable acceleration data and diagnostic logging. Nothing beats good data for troubleshooting!

#11

Just did the vacuum leak test. The air box flap didn’t actuate at all, but the manifold flaps were fine. Not sure I can test definitively for a leak without a vacuum gauge.

Would a stuck closed air box flap cause this amount of power loss? When I have more time, I’ll get in there and make sure the mech is moving freely.

#12

So you’re on the right track!

Based on your description, still sounds like a vac leak. If your vacuum is leaking, it may not have enough force to open a sticky flap. For example, my flap is definitely a bit “sticky”. I have cleaned the edges of the flap contact area twice to keep it functioning well.

I’d recommend wiping down everything you can reach on the power flap actuator door and mechanism. I can snake my arm into the airbox and reach the door with a rag. Force the door open, and wipe everything you can reach down. Then try the test again.

#13

Yep, definitely heading in the right direction I think. Just to clarify, you managed to clean it through the upper intake hole when you pull the snorkel off? Or you unscrewed the top of the airbox (as you would to get to the air filter) and cleaned from there? I can get my hand in the top snorkel opening, but didn’t know where the pivot point was for the intake flap, and did want to go poking around too hard in case I broke something.

I’ve also just ordered:

  • New Plugs
  • Fuel Filter
  • Oil Filter
  • K&N Air Filter

Just to make sure I have all the maintenance items done as well.

#14

I took off the snorkel and top of the airbox, then snaked my arm/hand to the flap. It is vacuum actuated, so you won’t break anything. Just be firm and gentle at the same time. :slight_smile:

#15

Isn’t that what she said… ??

#16

Just got the car back from the service and car is already feeling much better. They loosened up and lubed the airbox flap and the mech is working well. They also ran a vacuum pump on the lines and there are no leaks which is good. I still need to do the actuator test in VCDS though to see if the flap is moving, as I suspect it’s actually the solenoid that’s gone as I didn’t hear any clicking when doing the test last time.

I’ll do some more logging this weekend to see what improvements have been been made from the filter and plug changes.

#17

What’s the total work you had done?

#18

K&N Air filter, Fuel Filter, Spark Plugs, Oil Filter (this was pretty new anyway).
The paper filter that was pulled out was pretty dirty so that wouldn’t have been helping.

#19

Did you ever check the carbon situation? That’ll make a bug difference as well.

#20

Bug differences are important.

Sorry, I couldn’t resist. :wink: