Autowerkes Equal Length Resonated Tinny Noise

[ASRman]

Hi all

I have an order for the EQ midpipe from Active Autowerkes with the resonated section. I am currently running Akrapovic downpipes and the AA single midpipe.

Since placing the order I've been informed by a few folks running the above set up that there is quite a nasty 'resonance' or 'vibration' which occurs at low speed gear changes at low RPM. As its been mentioned a few times by different people I think that rules out an install error.

Question is why hasn't this been reported on here and if there is an issue with resonator vibrations is Active Autowerkes doing any about this? I think I did read somewhere over on the F87 board they may have redesigned the resonators to resolve this unpleasant noise. Does anyone know whether this has now been actioned and released?

I do not really want to cancel the order as top end the exhaust sounds magical but if its at the cost of sounding tinny at low RPM I may sadly have to re-consider. I have also emailed Autowerkes and will update this thread once they respond.

Any information pertaining to the above would be extremely helpful.

[mike@x-ph.com]

if you get a vibration or resonance, adjust the install. the same thing happened with the shop's M4. its a tricky install but if you do it correctly, you wont get that drone or resonance

[RugbyBro]

Chances are you won’t have to adjust it but just be ready to adjust it and re-tighten everything after it heat cycles a few times. If you don’t mind getting your hands a little dirty then it’s really not a big deal. In my mind there’s only really three possibilities when it comes to rattle:

1. Not seated right to the DPs
2. Touching the heat shield or brace
3. Clamps aren’t tight

[PandaxF82]

Originally Posted by mike@x-ph.com

if you get a vibration or resonance, adjust the install. the same thing happened with the shop's M4. its a tricky install but if you do it correctly, you wont get that drone or resonance

I am having a similar concern on my F82 paired with a resonated AA EL midpipe. I have Catless downpipes paired to a Remus axelback.

I am hearing a slight tinny resonance from about 1800-2200rpm. Seems like it is caused by imbalance of air pressure created by the EL midpipe.

Can anyone provide any insight on a remedy?

[mike@x-ph.com]

Originally Posted by PandaxF82

I am having a similar concern on my F82 paired with a resonated AA EL midpipe. I have Catless downpipes paired to a Remus axelback.

I am hearing a slight tinny resonance from about 1800-2200rpm. Seems like it is caused by imbalance of air pressure created by the EL midpipe.

Can anyone provide any insight on a remedy?

I recommend changing to catted downpipes, I tried resonated EL with catless and could not get rid of the resonance and drone

[PandaxF82]

Originally Posted by mike@x-ph.com

I recommend changing to catted downpipes, I tried resonated EL with catless and could not get rid of the resonance and drone

Primarily in low RPMS when under load in efficient mode is when I hear this resonance more. With valves open not as much.

You still recommend catted downpipes?

[RugbyBro]

Originally Posted by PandaxF82

Primarily in low RPMS when under load in efficient mode is when I hear this resonance more. With valves open not as much.

You still recommend catted downpipes?

My working theory (with no tangible evidence of course) is that the waste gates are open in the low rpm outside of 1st & 2nd gear for efficiency purposes... aka the cruising gears. I think that's also why in the stock exhaust chain, the valves close in sport & sport+ when in those situations and don't open back up until you hit around 3k rpm.

FWIW I just had a single mid on my car and the same sound is still there, however, the single mid does a better job of blending it out since the unequal exhaust tone is more similar to that noise. I think it's more obvious with the EL setup because the exhaust note is less similar to that noise.

[Soul Coughing]

Originally Posted by RugbyBro

My working theory (with no tangible evidence of course) is that the waste gates are open in the low rpm outside of 1st & 2nd gear for efficiency purposes... aka the cruising gears. I think that's also why in the stock exhaust chain, the valves close in sport & sport+ when in those situations and don't open back up until you hit around 3k rpm.

FWIW I just had a single mid on my car and the same sound is still there, however, the single mid does a better job of blending it out since the unequal exhaust tone is more similar to that noise. I think it's more obvious with the EL setup because the exhaust note is less similar to that noise.

A way to test that theory would be to force open the valves, and put it in sport + and see if the noise goes away compared to efficient mode. I will give it a shot when i leave work today. I have a feeling its just the rear exhaust muffler has a different resonance when it's cold compared to warm as the noise goes away when the exhaust has some heat in it.

[RugbyBro]

Originally Posted by Soul Coughing

A way to test that theory would be to force open the valves, and put it in sport + and see if the noise goes away compared to efficient mode. I will give it a shot when i leave work today. I have a feeling its just the rear exhaust muffler has a different resonance when it's cold compared to warm as the noise goes away when the exhaust has some heat in it.

I did do that with my last exhaust chain (stock DP / non res / stock muffler) and the sound was most definitely there no matter what mode in that specific situation of high gear/low rpm and load (for instance cruising in 4th or 5th gear at 1.5k). With the valves closed I could tell the engine was making the same noise but it was suppressed so much that you’d have to listen closely. Right now my chain is the same but with a Eisenmann muffler but I can’t test the difference in valve position because my valves are not working so they’re stuck open… hoping to remedy that soon.

Definitely try it out tho, curious to see if you have the same observation. I’ve heard people get rid of it during cold starts by doing a cold start delete. I’ve also heard that GTS software keeps the wastegates open longer at start up

[mike@x-ph.com]

Originally Posted by PandaxF82

Primarily in low RPMS when under load in efficient mode is when I hear this resonance more. With valves open not as much.

You still recommend catted downpipes?

I had the same issue and the catted downpipes fixed it for me.

[PandaxF82]

Originally Posted by mike@x-ph.com

I had the same issue and the catted downpipes fixed it for me.

Would that negate higher tuned cars like mine or should I resort to high flow cats.

[mike@x-ph.com]

Originally Posted by PandaxF82

Would that negate higher tuned cars like mine or should I resort to high flow cats.

The power is the same on stock turbo between high catted downpipes and catless.

[TopJimmy]

I've had a few AA kits. The vibration or rattle can come from many things, all typically related to install.

1) When installing the Midpipe it's more important for the pipe(s) to be in the middle (top to bottom) of the tunnel, and not so important that the down pipe flanges seat perfectly flat. This way the tube(s) don't push up and vibrate on the heat shields under the car. A buddy suggested placing a 1x4 wood block over and under the pipe inside the cross-brace while tightening flange bolts, then removing the blocks after the tube(s) are centered.

2) When installing the extension tubes make sure the clamp bolts stay low so they don't touch the heat shields either. I've quieted quite a few noises by a buddy pulling down the Midpipe while I rotated and tightened spherical clamps. (I hate saying "ball clamps"…sounds like a torture device.)

3) Most aftermarket exhaust is either larger diameter and/or secondary cat delete, so more noise and pop comes down the tubes. Make sure your valve springs push down nice and hard on the valve flappers. This eliminates the cold start flap rattle, and keeps vibrations lowered with valves closed under power.

4) Catless DPs, even resonated, let even more pop/rasp downstream, so this multiplies the need to cover #3 above. An alternative to messing with the valve actuator spring is runnng with valves open and unplugging them.

[PandaxF82]

Originally Posted by TopJimmy

I've had a few AA kits. The vibration or rattle can come from many things, all typically related to install.

1) When installing the Midpipe it's more important for the pipe(s) to be in the middle (top to bottom) of the tunnel, and not so important that the down pipe flanges seat perfectly flat. This way the tube(s) don't push up and vibrate on the heat shields under the car. A buddy suggested placing a 1x4 wood block over and under the pipe inside the cross-brace while tightening flange bolts, then removing the blocks after the tube(s) are centered.

2) When installing the extension tubes make sure the clamp bolts stay low so they don't touch the heat shields either. I've quieted quite a few noises by a buddy pulling down the Midpipe while I rotated and tightened spherical clamps. (I hate saying "ball clamps"…sounds like a torture device.)

3) Most aftermarket exhaust is either larger diameter and/or secondary cat delete, so more noise and pop comes down the tubes. Make sure your valve springs push down nice and hard on the valve flappers. This eliminates the cold start flap rattle, and keeps vibrations lowered with valves closed under power.

4) Catless DPs, even resonated, let even more pop/rasp downstream, so this multiplies the need to cover #3 above. An alternative to messing with the valve actuator spring is runnng with valves open and unplugging them.

Copy that.

Rattle is not from install. Nothing is touching not vibrating from hitting the bottom of the car.

This sound is purely created from air flow in and out of the system.