Car slower after AWE exhaust! Alu Kreuz is a disappointment

[elhalish]

Hey guys,

I'm coming the world of Subaru and just got myself a 2012 B8 S4 6MT a few months ago. It was a natural transition from my STi. The S4 is awesome stock, good base handling and power. Anyways, I just got an AWE catback installed on Saturday and aside from 1st gear, the low end is super weak now in all gears. It starts to pick up only after 5,000 rpm. Its not tuned yet and only other power mod is an AWE intake. Is it normal to lose low end torque before the tune?

Also, what is everyone talking about with the Alu Kreuz being the "best bang for the buck" mod. There is no difference in steering response, turning speeds...anything appreciable. Given I already had H&R OE springs on before this mod, but I expected it to add...something.

Am I missing something here?

[Ynnekdude]

Hey guys,

I'm coming the world of Subaru and just got myself a 2012 B8 S4 6MT a few months ago. It was a natural transition from my STi. The S4 is awesome stock, good base handling and power. Anyways, I just got an AWE catback installed on Saturday and aside from 1st gear, the low end is super weak now in all gears. It starts to pick up only after 5,000 rpm. Its not tuned yet and only other power mod is an AWE intake. Is it normal to lose low end torque before the tune?

Also, what is everyone talking about with the Alu Kreuz being the "best bang for the buck" mod. There is no difference in steering response, turning speeds...anything appreciable. Given I already had H&R OE springs on before this mod, but I expected it to add...something.

Am I missing something here?

Not sure if srs...

You should not be noticing any power loss. If anything, maybe some improved throttle response but that's about it. Do you have access to a vag-com? Check for codes. May be a coincidence and there is something else at fault.

[elhalish]

Yeah, I am going to do some logging this weekend. I don't have a baseline pre-exhaust log to compare it to, but i'll see if there is anything obvious

[Ynnekdude]

Yeah, I am going to do some logging this weekend. I don't have a baseline pre-exhaust log to compare it to, but i'll see if there is anything obvious

An exhaust will not cause loss in power (that is, one made by someone who knows what they're doing... AWE does). Intake might cause a little bit of a loss in torque down low but AWE's seems to perform pretty well. Chances are that something else is in play.

By chance did you do all of this on a very hot day? I know that hot weather really makes me feel slow.

[elhalish]

An exhaust will not cause loss in power (that is, one made by someone who knows what they're doing... AWE does). Intake might cause a little bit of a loss in torque down low but AWE's seems to perform pretty well. Chances are that something else is in play.

By chance did you do all of this on a very hot day? I know that hot weather really makes me feel slow.

I'm in Florida, its hot all the time and the car is not any different at night when its 20 degrees cooler. I did the AWE Intake a couple of months ago and noticed improved throttle response, and car felt great down low. Its only after the exhaust that its slower. Does the ECU need to learn around the exhaust a little?

[jdwk]

You need to do some sort of measurement. The human mind can play a lot of tricks. Use a mounted smartphone, a stopwatch, a dyno, or preferably a drag strip.

Mods like the Alu Kruez are only apparent where forces would normally twist the chassis. So you have to be driving at or past the limits of grip to notice any difference. You really need to have it on a race track to properly realize those kinds of benefits. Also, the guys who really rave about it probably are running Hoosier's or at least R compound DOT tires which would greatly exaggerate any flex.

The OE springs would decrease the roll and transfer more stress to the chassis not less. I would think the Alu Kruez would be more beneficial with the stiffer springs, not less.

[elhalish]

I agree with you, jdwk, this could be partly psychological, that with the increased sound I would expect more power. But something is definitely amiss because I can feel a generous amount of pick up beyond 5k rpm, kind of like on a turbo car. From what I understand, an untuned, B8 S4 should start falling flat at higher RPMs

[AKPS4]

you might be feeling the greater power up higher and think that there is less power down low.

i agree that the S4 is weak in first gear at low rpms but anything after that it takes off. exhaust will only hurt lower end if you put on larger diameter exhaust all the way front to back which will certainly decrease torque with the significantly reduces back pressure. i doubt AWE exhaust would cause power loss, especially since i have yet to read a single bad review about this system.

check for codes, otherwise keep driving for a week or so and see if you can convince yourself there really is a problem. make sure all connections are tight and nothing is loose.

[dawei213]

As jdwk has mention, as well as myself before, for the Alu Kreuz, unless you are driving near the limit, you wont't notice much of a difference on day to day driving (unless you are driving at the limit at all time. As for the exhaust, you shouldn't feel any lose of power. Maybe you are expecting at least some noticeable gain but not feeling it , hence you feel it might be limosibg power.

[helix139]

Something is up if you are not tuned and you feel your car is strongest after 5k rpms, seeing as the bypass valve opens at around 5400 and starts to bleed boost and power off.

As far as the Alu Kreuz, what you should feel is less slop in the steering. It doesn't do anything to change the steering ratio or the suspension itself, but it does prevent the front subframe from torsionally deflecting, thus allowing a more immediate response from the steering rack, more feedback through the wheel, and a less vague feel when making steering adjustments over uneven surfaces as the suspension is doing the work it was designed to do as opposed to the subframe of the car. It's a subtle, but very meaningful difference to the driving experience.

[CreoSTi]

It doesn't do anything to change the steering ratio or the suspension itself, but it does prevent the front subframe from torsionally deflecting, thus allowing a more immediate response from the steering rack, more feedback through the wheel, and a less vague feel when making steering adjustments over uneven surfaces as the suspension is doing the work it was designed to do as opposed to the subframe of the car. It's a subtle, but very meaningful difference to the driving experience.

+1

The biggest difference in feel for me in normal driving was going up/down my parking garage at work... When turning and changing elevation, the Alu Kreuz felt much more solid/less flexible than without it (even on coilovers).

[elhalish]

Do you have access to a vag-com?

Yes, going to data log this weekend.

Thanks for all the replies. I'll give it some time. I just know that from past experiences, when I feel something is off, something is usually malfunctioning. But that is with 8 years of Subarus and not 5 months with an Audi.

[Seinsmeld13]

I didn't notice any power loss. I do however have an annoying rattle. I also have PSS10's installed. The mechanic for the coil over said the sound is coming from the exhaust. I took the car to my regular mechanic he said the issue is not the exhaust it's nice and tight. Driving alone there generally are no issues the sound of what I think is loose exhaust appears when there are two or more in the car very strange. I will have to schedule an appointment to have the exhaust looked at I just don't have time right now. All I can say is there was no power loss,however, I have the stock intake. Good luck.

[ENV²]

These cars learn and relearn regularly (at least that has been my experience). If I drive like a normal person all day to work and back etc the car adapts and feels slower when I need to get on it but if I do a few high RPM/High speed highway pulls for a little while and then hit my twisties before pulling into the garage the whole car responds much differently, it even sounds more aggressive at idle when I pull in. I believe strongly that this car adapts to the situation but the ECU makes its changes the more you drive a certain way.

Also make sure you were in dynamic.

As far as the Alu Kreuz, I cannot speak to it alone because I did the sways, end links, and Alu Kreuz all at the same time and the limit of grip is astronomically better than it was before.

[Josh/AWE]

In terms of the exhaust, the car should definitely not feel "slower." As others have said, the ECU re-adapts over time and based on your driving habits it can feel slow based on how you treat it. At the same time, based on the gains from our system (or any for that matter) the difference will not be night and day. The sound is the largest benefit, with added power being a bonus when all (or most) other bits on the car are stock. These gains from the exhaust will further increase when you add software, pulley, etc.

If you are looking for your car to be much faster, an ECU tune is what you should be after.


Unfortunately I do not have and experience with the Alu-Kreuz so I can't comment on it.

[MailmanOdd]

I just recently got my AWE exhaust installed and it feels about the same to me (but sounds oh so sexy). Sounds like there may be something else! Hope you get it figured out!!

[ZILLA]

I thought it was just me. Mine DEFINITELY feels slower than stock. No leaks anywhere, double and triple checked. Feels like a lag in throttle and less torque from low speeds.

[elhalish]

I thought it was just me. Mine DEFINITELY feels slower than stock. No leaks anywhere, double and triple checked. Feels like a lag in throttle and less torque from low speeds.

I wish we had objective data to analyze whether our perceptions are real. Oh well. Time for a tune.

[gringoloco2000]

I have a Revo tune and a AWE intake. I did not notice a huge difference in power, but it did not lose power from what I could tell. I love the sound and it looks good too. I am very happy with it.

[jdwk]

I highly doubt there is that much scavenging occurring on a stock exhaust to make the car feel slower with an aftermarket exhaust. But two people feeling the same thing probably has a logical explanation.

As high tech and complicated as the S4 is, there is still an OBDII port. So you could scan your fuel trims and see if your car is dumping or pulling an unusual amount of fuel. I use Torque on my smartphone and a little bluetooth connector to start any tuning diagnosis. The connectors are only about $25 now and Torque is $5 for the pro version.

[sworksone]

I feel your pain. My car's been noticeably slower ever since I changed the carpet floor mats out for the heavier OEM rubber ones.

[westwest888]

Hey guys,

I'm coming the world of Subaru and just got myself a 2012 B8 S4 6MT a few months ago. It was a natural transition from my STi. The S4 is awesome stock, good base handling and power. Anyways, I just got an AWE catback installed on Saturday and aside from 1st gear, the low end is super weak now in all gears. It starts to pick up only after 5,000 rpm. Its not tuned yet and only other power mod is an AWE intake. Is it normal to lose low end torque before the tune?

Also, what is everyone talking about with the Alu Kreuz being the "best bang for the buck" mod. There is no difference in steering response, turning speeds...anything appreciable. Given I already had H&R OE springs on before this mod, but I expected it to add...something.

Am I missing something here?

You gutted the exhaust and removed all of the back pressure. Your power is all there but it has moved up the RPM curve. You'll see reduced response below 3000 RPM and increased flow in the 5000 range. That is what that mod does.

There's no data on Alu Kruez. I've asked what it does at the limit and no one can tell me.

[Leor604]

There's no data on Alu Kruez. I've asked what it does at the limit and no one can tell me.

I can't speak to the benefits of the AK by itselt as I had it and the full USS setup done at the same time. Had the car on the track the very next day and the combination definitely translates into higher cornering speeds.

I have done quite a few track days with another member here who is APR Stage 2+ with AK. Previously, besides being much quicker in a straight line (I'm stock), his car transitioned from left to right quicker than mine. In chasing him through some transitions, I could see his car just responded to steering inputs much quicker and he would also slowly pull on me in long sweepers. Only difference was AK.

Now, with AK and USS, the tables are turned. I was able to slowly pull on him in the corners, despite him having Pilot Super Sports which are considered to be the best tire right now. I'm on worn stock Dunlop Sport Maxx's.

If I had to summarize it, I would say the AK aids in stiffening up any slop and just making the car feel a lot snappier when you crank the wheel. I certainly felt the difference in the very first corner after leaving Achtuning who did my install. The USS cleaned up the understeer and roll and allows the cornering load to be spread evenly front and rear instead of overloading the front tires.

Hope that helps explain the benefits, at least in my experience.

[PsYkHoTiK]

Truth. Handling mods are awesome. I'm a believer after the last track day.

[jdwk]

You gutted the exhaust and removed all of the back pressure. Your power is all there but it has moved up the RPM curve. You'll see reduced response below 3000 RPM and increased flow in the 5000 range. That is what that mod does.

There's no data on Alu Kruez. I've asked what it does at the limit and no one can tell me.

If he had installed a cam, I'd believe that. Not a header back exhaust. Look at the dyno plot provided by AWE. In fact, I've never seen a back to back dyno on any car with an aftermarket exhaust show lower than stock, certainly not enough to notice.

To me it sounds like the car is pulling or adding too much fuel because of an improper O2 reading. It used to be cars just turned off closed loop at a certain RPM or certain throttle input, but cars are getting more sophisticated and I think the "turbo-like" feeling the OP is describing is the PCM giving up on closed loop at 5k rpms and switching to open maps.

A quick scan with an OBDII reader while driving through that RPM range will tell you if it is tuning related.