sound DB measurement for Laguna Seca

[F82K2S0]

I'm not sure if this is better placed in the Engine/exhaust thread or track thread, but has anyone any experience with DB levels using different exhaust setups to pass DB restrictions @ MRLS?

My lovely Frankenstein system :
gintani downpipes + Active autowerks midpipe + dinan axle back

I don't expect to pass DB restrictions.
Does anyone know if retaining one of either stock downpipes or stock midpipe will bring DB level to pass or would both stock DP+midpipe be needed to pass?

Anyone in socal have a device to measure db ?

Thanks

[w00tw00t]

to add to this, I wonder if keeping flaps closed with even an aggressive setup such as the above will pass the 90db limit..

[F82K2S0]

Originally Posted by w00tw00t

to add to this, I wonder if keeping flaps closed with even an aggressive setup such as the above will pass the 90db limit..

I was thinking the same thing, toggling the flap closed near the sound trap turn on each lap.

[w00tw00t]

That doesn't make sense. When I'm on the track the last thing I want to worry about is toggling the flap on and off near T5... I am 100% focused on my line, car control etc.. I just keep mine closed all the time while I'm at Laguna.. Open for other tracks...

[F82K2S0]

All you do is toggle the M button. I'm so used to doing this anytime I see the police to hide the loud exhaust and silence the stupid burble it is second nature on the wheel for me with the thumb just like hitting the paddle of a DCT

[w00tw00t]

All the M setting is doing adjusting your throttle, suspension, and steering based on how you set them up.

the exhaust only remains closed in efficient throttle setting, in sport and sport+ it opens up, changing your throttle sensitivity while entering a turn at high speed is not such a good idea IMO.

I always keep my throttle in sport+ on the track and also on the street. I have a BMS Flap controller module to control my flaps.

I currently have a stock exhaust but soon hope to get a Remus + AA Midpipe so I'm hoping that using my BMS flap controller I can keep my flaps closed all the time at laguna and pass limit.

[F82K2S0]

My EDC is coded out for coilovers, and steering remains the same in sport with both M and out of M mode, so as you said all that is changing when I toggle my M button to off is the engine turns to efficient mode and closes valve. Then a turn or so later at a safe place I can toggle the M mode back on for sport+ throttle. Not at all ideal in any way I agree. I am just trying to estimate if I should put both my primary and secondary cats back on or just the DP is enough to pass DB. Input from anyone who has been black flagged for DB would be helpful to know what to expect for different exhaust setups db level.
Thanks

[bd307]

Some events have high db requirement at MRLS and that can make a different.

There are apps that you can use to test the db. Find an empty street and go WOT without getting caught

Your event may also have a test station for you to use at MRLS for finding out your db level from the exhaust. Contact them to find out.

Suggest you to go easy on throttle when reaching that section instead of pushing buttons around the track.

[Jimbooo]

This is probably wholly irrelevant to you guys but as a related bit of info my mpe which has 16000 miles use with open flaps measured 109db with revs held at 5500rpm on a recent track day in the uk.
Last year at a previous track day different track it read 104db at 4000rpm.
This is the static test before being allowed on track.

The fly by on track limit was 95db and I got close but didn't get red flagged. Yellow a few times which means within 5db of the limit.
All this was with flaps open.

Should add that this is a standard mpe with no further mods aside from replacement k&n panel filters and cg precision valve controller. Everything else as standard.

[F82K2S0]

Thank you Jimbooo, curious if your car in England has stock primary and secondary cats similar to cars destined for USA? That has to be the primary bottleneck for DB regardless of the axle back exhaust portion. I'm starting to feel like I need to go fully OEM to comply with DB limits at MRLS. and also change my stage2 to a stage1 tune to match

[larryn]

If it is any help, I just helped a buddy install dinan exhaust and X pipe, which keeps the stock cats, and that system would easily trigger the 90dB limit at MRLS, powering up the hill at T5 to T6.

[F82K2S0]

That does help larryn thank you.

[///Machiavelli]

Originally Posted by Jimbooo

This is probably wholly irrelevant to you guys but as a related bit of info my mpe which has 16000 miles use with open flaps measured 109db with revs held at 5500rpm on a recent track day in the uk.
Last year at a previous track day different track it read 104db at 4000rpm.
This is the static test before being allowed on track.

The fly by on track limit was 95db and I got close but didn't get red flagged. Yellow a few times which means within 5db of the limit.
All this was with flaps open.

Should add that this is a standard mpe with no further mods aside from replacement k&n panel filters and cg precision valve controller. Everything else as standard.

Thanks for the info.

I'm booked for July HPDE at track which is new to me. Now I'm a little concerned because even with throttle set to comfort at redline the flaps are going to open on my mpe. The track has the following noise testing and regulations:

Screening Test – After a brief visual muffler check, a stationary test is undertaken. Sound levels will be measured 15 feet in front and behind the vehicle while the engine is revved at the maximum allowable rpm or the red line of the tachometer.

Cars, the average should be no more than 100 dbA with no single reading over 104 dbA.
Motorcycles, the average should be no more than 98 dbA with no single reading over 100 dbA.

Pass-by Test – With the vehicle under full acceleration on the track, a reading will be taken from 50 feet. The maximum level allowed is 92 dbA. This level and standard is the most commonly used in North America and Europe and is where the entire industry is headed. Tests are valid for 9 months unless modifications to vehicle are made.

[afadeev]

Originally Posted by w00tw00t

to add to this, I wonder if keeping flaps closed with even an aggressive setup such as the above will pass the 90db limit..

Don't you have more important things to worry about on track?
Like learning to drive properly?

[Jimbooo]

Originally Posted by ///Machiavelli

Thanks for the info.

I'm booked for July HPDE at track which is new to me. Now I'm a little concerned because even with throttle set to comfort at redline the flaps are going to open on my mpe. The track has the following noise testing and regulations:

Screening Test – After a brief visual muffler check, a stationary test is undertaken. Sound levels will be measured 15 feet in front and behind the vehicle while the engine is revved at the maximum allowable rpm or the red line of the tachometer.

Cars, the average should be no more than 100 dbA with no single reading over 104 dbA.
Motorcycles, the average should be no more than 98 dbA with no single reading over 100 dbA.

Pass-by Test – With the vehicle under full acceleration on the track, a reading will be taken from 50 feet. The maximum level allowed is 92 dbA. This level and standard is the most commonly used in North America and Europe and is where the entire industry is headed. Tests are valid for 9 months unless modifications to vehicle are made.

The distance for measurement is a lot closer for UK tests. this is a copy/paste from the circuit noise test info from cadwell park in the UK

"The initial test is a static test which is carried out using a handheld meter. Each car is measured 0.5 meters away from the exhaust at a 45 degree angle when the engine is being held at ¾ of the maximum RPM. In cases where the vehicle has two separated exhausts the measurement will be taken as below from the median point between the two."

so the mic is far closer meaning it will read louder but its only 3/4 of the redline rpm. however i dont think there is a huge difference in the db between 3/4 and 100% of redline.

so in summary this info is still clear as mud! its one of those things you cant really know for sure until the day. you could as an educated guess use an iphone DB meter app and get a mate to stand in the appropriate position and replicate the test.
it wont be perfect but will give you an idea.

[Jimbooo]

Originally Posted by F82K2S0

Thank you Jimbooo, curious if your car in England has stock primary and secondary cats similar to cars destined for USA? That has to be the primary bottleneck for DB regardless of the axle back exhaust portion. I'm starting to feel like I need to go fully OEM to comply with DB limits at MRLS. and also change my stage2 to a stage1 tune to match

im 99% sure the MPE is identical wherever its supplied. i havent had anything "removed" as such, no fiddling with anything just dealer fitted MPE and thats it.

one thing we dont have is the charcoal filter in the airbox's so that will improve airflow a tad but doubt it makes a huge difference. then again i imagine most of you rip that out on day one anyway lol

[Jimbooo]

This is the oem m4 exhaust that was removed. No idea how many cats it has. If two then the other must be on the remaining bit on the car. :

[F82K2S0]

The big box looking object near the bottom of your picture is the resonator, beyond that still attached to your car on the midpipe is the secondary cat, and on the downpipe is the primary cat. Both cats are the huge bottleneck, and for myself are completely removed.

I think I'm just going to roll with what I've got and deal with getting black flagged and booted at some point during the day if lifting on the metered turn every lap does not work as planned.

[F82K2S0]

Originally Posted by afadeev

Don't you have more important things to worry about on track?
Like learning to drive properly?

Nah, its not like the M button is in the glove box, its on the steering wheel. Multitasking with the thumb is no more distracting than pulling on the paddle to shift up.. also on the steering wheel.

Compared to MT heel and toe is way more involved than a thumb press on the wheel and can distract/worry people learning to multitask, once learned it is just second nature muscle memory. no worries