ECU mapping for noise reduction?

[Steve_D]

Does anyone know if it is possible to alter engine mapping to quieten the engine?

My challenge is a 640BHP Chevy LS7 V8 which is too noisy when tested at certain revs. I was wondering if perhaps retarding the ignition and perhaps running it rich would take out a few Db.


Thanks in anticipation.
Steve

[TheEnd]

I would say it's highly unlikely, unless you drastically cut the power.
The majority of the noise will be from the exhaust system resonating.

[anonymous-user]

retarding the ignition may actally make it noisier! As you will be burning the charge later in the cycle, at EVO there will be a higher cylinder pressure and so more energy will be lost out of the exhaust (and you will have a higher exhaust mass flow to get to the same engine speed)


Assuming that the engine is tested without load (i.e. just open throttle in neutral) then you might (note the might!!) actually be able to massively over advance the ignition (won;t det, but might get pre-ignition) and this will quieten it down a bit.

worth a try, but probably only a few % difference in noise - best idea is to er, "adjust" the rev counter cal for the noise test........... (not that i could possibly recommend that sort of cheating ;-)

[stevieturbo]

Lean and advance will quieten it a bit.


But obvious thing to to is tune it with the db meter stuck where ever it will be when getting tested. That way you can get noise down to a minimum. Although big silencers also help.

[Steve_D]

Max_Torque said:

........best idea is to er, "adjust" the rev counter cal for the noise test........... (not that i could possibly recommend that sort of cheating ;-)

This has been mentioned before in other threads but the tester has an audio box which counts the engine beats. He sets the number of cylinders and the readout tells him the revs no matter what it says on your dash.

stevieturbo said:

Lean and advance will quieten it a bit.

But obvious thing to to is tune it with the db meter stuck where ever it will be when getting tested. That way you can get noise down to a minimum. Although big silencers also help.

It already has big silencers but being mid engined there is not much space and the system is no where near as long as it should ideally be.

Thanks for the input Guys.
Steve

Edited by Steve_D on Tuesday 12th October 23:57

[andygtt]

Steve_D said:

Max_Torque said:

........best idea is to er, "adjust" the rev counter cal for the noise test........... (not that i could possibly recommend that sort of cheating ;-)

This has been mentioned before in other threads but the tester has an audio box which counts the engine beats. He sets the number of cylinders and the readout tells him the revs no matter what it says on your dash.

stevieturbo said:

Lean and advance will quieten it a bit.

But obvious thing to to is tune it with the db meter stuck where ever it will be when getting tested. That way you can get noise down to a minimum. Although big silencers also help.

It already has big silencers but being mid engined there is not much space and the system is no where near as long as it should ideally be.

Thanks for the input Guys.
Steve

Edited by Steve_D on Tuesday 12th October 23:57

you know what im going to say... try and get some extra length in the exhaust as I did.... you dont need more silences just some bends and meter of extra pipe and you will loose 3db.

[blitzracing]

Tried decibel tubes?

[Steve_D]

blitzracing said:

Tried decibel tubes?

No.
Do you have a link? Tried Google but it didn't find me anything.

Steve

[V10Mike]

Can you siamese the exhaust so that the flow is shared between both silencers? Usually worth about 3dB.

[stevieturbo]

Or a balance pipe...same odds


Db tube or whatever people want to call it is basically a bung that restricts the tailpipe.

OK for static tests, but maybe not always ok for drive by, as you may not have it installed for a drive by.

[Steve_D]

Each side of the exhaust system takes the 4 primary pipes into one then into a CAT then bothsides go into a V large silencer across the car with 2 tail pipes coming out the other side of the box.

There is no more room for extra pipe length.

Without being specific this is to pass a one off static only test.

I'm interested to try the decibel tubes but have not yet found where to buy them.

Steve

[andygtt]

is there room inside the exhaust to fit some temporary restrictors?

[stevieturbo]

Steve_D said:

Each side of the exhaust system takes the 4 primary pipes into one then into a CAT then bothsides go into a V large silencer across the car with 2 tail pipes coming out the other side of the box.

There is no more room for extra pipe length.

Without being specific this is to pass a one off static only test.

I'm interested to try the decibel tubes but have not yet found where to buy them.

Steve

Any pics ? Are both tubes interlinked at any point ? ie after the cats ? either an X-flow or H balance pipe type will help reduce noise, and usually offer a performance benefit too, albeit small.
What is the makeup of the silencer ? Chambered ? striaght through perforated tube ?

The insert could be as simple as a restriction at the tailpipe.

[blitzracing]

http://www.merlinmotorsport.co.uk/p1527/JETEX-UNIV...

They do restrict a tad, but I think the idea is to bounce some of the shockwaves back into the wadding to reduce the noise, more than simply restrict the gas flow. I have them on my 4ltr Ginetta with short side pipes and have not noticed a drop in power. Ive seen them in various sizes other than this.