AKRAPOVIC owners: Got a super annoying exhaust rattle when lift off.

celicatoe46m3 · 05-31-2021, 05:11 AM

When in any gear when the tach hits 1800 rpm, it gives a nasty rattle that I've pin pointed to the driver side.

Some facts:
- got akra
- i have my valve wired open
- driving very slow in the morning doesn't make the noise
- only after a warm up, and I need to get up to speed before it starts making the noise
- my exhaust rubber valve tubes are connected - and not shut/plugged
- It sounds like a metal rasp

From what I can also diagnose is that it's not the valve or the mechanism that's rattling at idle or anything.

It happens in any gear, and its super annoying. When going down a small hill and beside a wall, if I can keep the speed consistent, the sound can always be heard, but its always during the 1800rpm-1700rpm range ONLY.

Things I haven't done yet is close the valve. I've tried to put my gopro on the bumper area to get a better noise, but it's got alot of wind noise so its hard to hear. But with windows down, its super easy and quite loud.

I can't seem to find anyone with the same issue, as the closest is someone with akra, having a vibrating issue noise when idle. But this isn't the problem I'm having.

I assume its the exhaust? Or am I looking in the wrong area?

Gel2al2d · 05-31-2021, 08:33 AM

are you sure its not wastegate rattle? thats a known problem with our cars

m5rosco · 05-31-2021, 11:33 AM

Do you have decats as well?

celicatoe46m3 · 05-31-2021, 05:56 PM

Quote:

Originally Posted by Gel2al2d

are you sure its not wastegate rattle? thats a known problem with our cars

Yes I know that sound as well, but my wastegate is not loud at all.

The sound is almost like a small saw buzzing sound, where a saw comes into contact with metal for a brief second. If I keep my speed constant and the tach is at 1800 rpm, the sound can be sustained.

celicatoe46m3 · 05-31-2021, 05:57 PM

Quote:

Originally Posted by m5rosco

Do you have decats as well?

Sorry I forgot to mention that I don't have many mods. Only AKRA with the flap-open mod.

I was also considering that the noise maybe the vacuum pump?

celicatoe46m3 · 06-14-2021, 02:32 AM

OK I solved my own problem.

Seems like the flap mod wasn't completely set to open, so I guess the vacuum pump tries to close it.

So I zip tied it again to be super tight and now it's fully open. Totally no rattle anymore.

celicatoe46m3 · 06-16-2021, 11:07 PM

Actually I spoke too early. Rattle is still there but not as loud..

I'm puzzled.

Boosted M5 · 06-16-2021, 11:59 PM

I had a rattle and needed to adjust the rod where the vacuum chamber is. Since you're forcing the valves to stay open I would disconnect the vacuum hose and plug it properly as there's no need for you to have it plugged in.

celicatoe46m3 · 06-17-2021, 08:34 AM

Quote:

Originally Posted by Boosted M5

I had a rattle and needed to adjust the rod where the vacuum chamber is. Since you're forcing the valves to stay open I would disconnect the vacuum hose and plug it properly as there's no need for you to have it plugged in.

So I need to do 2 actions? 1. Adjust the rod in what way?

2. Plug the hose by zipties is ok?

Was yours quite audible when windows are down?

celicatoe46m3 · 07-11-2021, 10:25 AM

I solved it. Finally had a day to fully diagnose the problem, and eliminate one thing at a time.

1. Removed the tips, and then removed my zip ties that keep the valves open

- tested driving around in normal mode, no buzzing. When in M mode, buzzing like crazy on lift off.

2. Removed the rubber hose from both sides, and plugged them with a golf tee and then zip tied them shut.

- tested fully and zero buzzing in normal and M mode.

Voila.

I think its the valve problem on the akra's left side. So I just left it plugged and tucked it away in the heat shields.

Took such a long time to diagnose as I didn't have any tools.

05-31-2021, 05:11 AM	#1
celicatoe46m3 Private First Class 47 Rep 170 Posts Drives: E60 M5 & E46 M3 Join Date: Dec 2010 Location: Vancouver iTrader: (3)	AKRAPOVIC owners: Got a super annoying exhaust rattle when lift off. When in any gear when the tach hits 1800 rpm, it gives a nasty rattle that I've pin pointed to the driver side. Some facts: - got akra - i have my valve wired open - driving very slow in the morning doesn't make the noise - only after a warm up, and I need to get up to speed before it starts making the noise - my exhaust rubber valve tubes are connected - and not shut/plugged - It sounds like a metal rasp From what I can also diagnose is that it's not the valve or the mechanism that's rattling at idle or anything. It happens in any gear, and its super annoying. When going down a small hill and beside a wall, if I can keep the speed consistent, the sound can always be heard, but its always during the 1800rpm-1700rpm range ONLY. Things I haven't done yet is close the valve. I've tried to put my gopro on the bumper area to get a better noise, but it's got alot of wind noise so its hard to hear. But with windows down, its super easy and quite loud. I can't seem to find anyone with the same issue, as the closest is someone with akra, having a vibrating issue noise when idle. But this isn't the problem I'm having. I assume its the exhaust? Or am I looking in the wrong area?
	Appreciate 0 Tweet Quote

05-31-2021, 08:33 AM	#2
Gel2al2d Private First Class 54 Rep 188 Posts Drives: '93 Toyota MR2, '14 BMW M5 Join Date: Dec 2008 Location: SoCal iTrader: (5)	are you sure its not wastegate rattle? thats a known problem with our cars
	Appreciate 0 Quote

05-31-2021, 11:33 AM	#3
m5rosco Second Lieutenant 211 Rep 250 Posts Drives: 2016 F10 M5 Join Date: Jun 2020 Location: UK iTrader: (0)	Do you have decats as well?
	Appreciate 0 Quote

06-14-2021, 02:32 AM	#6
celicatoe46m3 Private First Class 47 Rep 170 Posts Drives: E60 M5 & E46 M3 Join Date: Dec 2010 Location: Vancouver iTrader: (3)	OK I solved my own problem. Seems like the flap mod wasn't completely set to open, so I guess the vacuum pump tries to close it. So I zip tied it again to be super tight and now it's fully open. Totally no rattle anymore.
	Appreciate 0 Quote

06-16-2021, 11:07 PM	#7
celicatoe46m3 Private First Class 47 Rep 170 Posts Drives: E60 M5 & E46 M3 Join Date: Dec 2010 Location: Vancouver iTrader: (3)	Actually I spoke too early. Rattle is still there but not as loud.. I'm puzzled.
	Appreciate 0 Quote

06-16-2021, 11:59 PM	#8
Boosted M5 Private First Class 69 Rep 193 Posts Drives: F10 m5 Join Date: Dec 2018 Location: Sf bay area iTrader: (0)	I had a rattle and needed to adjust the rod where the vacuum chamber is. Since you're forcing the valves to stay open I would disconnect the vacuum hose and plug it properly as there's no need for you to have it plugged in.
	Appreciate 0 Quote

07-11-2021, 10:25 AM	#10
celicatoe46m3 Private First Class 47 Rep 170 Posts Drives: E60 M5 & E46 M3 Join Date: Dec 2010 Location: Vancouver iTrader: (3)	I solved it. Finally had a day to fully diagnose the problem, and eliminate one thing at a time. 1. Removed the tips, and then removed my zip ties that keep the valves open - tested driving around in normal mode, no buzzing. When in M mode, buzzing like crazy on lift off. 2. Removed the rubber hose from both sides, and plugged them with a golf tee and then zip tied them shut. - tested fully and zero buzzing in normal and M mode. Voila. I think its the valve problem on the akra's left side. So I just left it plugged and tucked it away in the heat shields. Took such a long time to diagnose as I didn't have any tools.
	Appreciate 0 Quote