Jawnathin

Was talking to a friend about trying to pass sound at Laguna and my plan was to run the Bi-Mode exhaust in 'Quiet Mode' where the bi-mode exhaust stays closed in upper RPMs.

My friend raised a concern about burning out cats or causing other problems because of the restricted exhaust flow.

Anyone have any experiences to share about doing this? Want to make sure I don't break anything.

Car has a mild cam + headers w/ high flow cats, so it'll probably run a little hotter/warmer than a stock car. Exhaust is the OEM Bi-Mode exhaust.

Thanks.

jwebsta32

At first I was going to say a completely stock Z wont pass sound musters, but after finishing the post I saw the mods....What is the sound level restriction?

Jawnathin

90-92dB

Agreed that the car completely stock can have trouble passing and my mods don't help. So I was hoping forcing the bi-mode exhaust closed would be what I need to pass.

After consulting with Mikymu who did this, he believes there could be some damage as a result of too much back pressure.

I have a way of forcing it closed on the fly, so I might just close it as I enter the sound check and open it back up later, but I really don't want to do this every lap.

I think the best experience/my end goal is to change when the bi-mode opens. So lets say I configure it to open at 5500rpm, I can just short shift and run at a lower RPM up Turn 5 and it'll open as commanded for the rest of the track. Should give the car the exhaust flow it needs at upper RPM while staying quiet below that threshold. The risk for damage should no longer be an issue either.

smellya

I have close to the same mods and I am crossing my fingers with the burns exhaust with turn downs. Got to love the 90db at laguna seca.... Damn people move by a race track it won't be loud....

harrydirty

For many of us track day guys, sound limit is 90db at Laguna. With my stock 07z, I was at 92.2db one day; however, keep in mind that sound is almost black magic and can vary due to weather, air density, phase of the moon, etc.

Having said that, I modded my exhaust so I can control it using the LG shift **** with the on/off button. I can force the valves shut while downshifting at entry to T5, then open again going into T6. I tried it a couple of months ago and it seemed to work for one session (no meatball flag), but my brakes failed and I could not test it more completely.

Jawnathin

Good luck. I'd love to run that Burns exhaust but I really like the Bi-Mode, really is the best of both worlds.

Agreed these 90dB days suck. Wish people had the foresight to understand where they were moving to instead of neutering the track. Sooner or later we won't be able to track anything but a Tesla at LS.

Jawnathin

Glad to know you passed doing that, thanks. Hopefully the moon and the planets are aligned in my favor for the HPDE.

It looks like I'll be doing something similar and closing the exhaust by sound check and reopening after the bridge. Really don't want to have to deal with playing with a switch when I'm trying to drive but I'm hoping I get used to it. Just need to be sure I don't forget for a lap and get the meatball and stern lecture.

harrydirty

I agree that I did not want to futz with a switch while driving, but I don't see many alternatives and this seemed like the easiest/cheapest to implement. Having the switch on the shift **** means that I don't have to look or reach for a switch since my hand is already there; this was the least intrusive implementation.

hungryhippo

I bought base model non-npp mufflers for Laguna seca. You can have a muffler shop modify the inlets to 3". Should be around $100 total and takes under an hour to swap.

mikeCsix

"They" do this at airports and gun ranges too, move close-in then complain about the noise. We have the same issues at Pacific Raceways in Seattle.

Would love to be able to run at Laguna Seca someday. I've only been able to visit the track and watch the Mazda's run. For hpde, do they require you to stop prior to hitting the front straight? It looked like a requirement for one of the Mazda sessions I saw.

harrydirty

Turn 11 is a tight turn, so maybe it appeared they were stopping

Seriously, there are no unusual requirements other than sound for running at Laguna. Hope you get to run it sometime, it's a blast!

Jawnathin

Agreed this is our best option so far and likely what I'll have to do for my HPDE next month. Not ideal but better than not running at all.

I think the best solution would be to bump up the RPM that forces the exhaust open, then just short shift and keep the RPMs below that threshold by the sound station. It'll open up when the exhaust really needs the flow. The Dashlogic device I purchased will be adding that functionality soon. Probably not in time for my track day though.

Not a bad idea if you have an easy way to swap exhausts. I don't have a lift, so its a bit of a hassle/impossible. How loud is your car with the non-NPP exhaust? I know they are quieter, but I'm surprised it would quiet it down that much.

The turn into the main straight is very tight, so but besides that there is no stopping before the straight. I've driven on it with a different car and never seen a barrier or anything restricting a flying run onto the main straight. It is a fun track, I like Thunderhill a bit better, but LS is much closer to where I live and therefore much more accessible. Less money on gas, no hotel, less time, etc.



Great course except for the sound restrictions.

hungryhippo

The non-npp exhaust is comparable to the npp with the valves closed. I was able to remove my b&b exhaust on jack stands. I had to trim 1" off the OEM pipes to reinstall. It is easily done with a good jack that goes over 20".

harrydirty

Hmmm, call me crazy, but pushing a button seems a lot easier than changing mufflers..............

Seriously, the initial mods to set up a button control is a bit of work, but once done, it's so simple to control the exhaust valves. If a driver wants, he can keep the valves closed for the entire track day, same as going to the non-npp muffler set. I chose to keep my valves open all day except when I pass the sound check station; sort of having my cake and eating it too. After the track day, I just set back to normal mode and my '07z doesn't know it's been modded (works normally). Best of all, parts cost is largely the LG shift ****; the rest is just some wires and a toggle switch; I can't think of a cheaper "solution".

Jawnathin

Maybe trimming 1" off the pipe is what let you do it, but when I tried swapping an uncut muffler I just couldn't get it out of there.

After a few hours of trying to work it out of there I gave up and put it back together. I understand most aftermarket exhausts are 'two piece' so that would be much easier to install as well.

Thanks for the suggestion but I don't think its a workable option for me.


The Dashlogic device does the same thing without any of the wiring work. Just plug it into your OBD2 port and then you're done. Not to mention all of the other cool stuff you get. Once plugged in, you use the side mirror rocker switch to control between 'Loud', 'Normal', and 'Quiet' modes. Don't even need to setup the wiring. Purely plug and play.

Left Mirror - Loud
Center - Normal/Stock
Right Mirror - Quiet

I can make the car 'quiet' on the straight between 4 and 5, then bring it back to 'loud' on the straight between 6 & 7.

Its going to be a little weird driving the car and messing with this every lap, but if those F1/ALMS drivers can mess with all those dials/buttons on their steering wheel at their speeds, I should be able to play with one switch driving much slower than them, haha.