Engine lugging boom 1

[vibrostics]

Could any one explain about the "Engine lugging boom" and its importance in NVH targets.

 

[GregLocock]

Depends who you work for. If you work for dead Henry then send me an email from work, I'm on CDS, but I won't be back at work for a week.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[vibrostics]

Greg,

Thanks for your reply. I don’t work for the said dead man and in no way associated with his company. Any how I request you to through some light in generalized words.

Thanks.

 

[GregLocock]

Lugging boom is the loud low frequency (firing frequency) noise you get when you run the engine at a reasonable throttle opening, at fairly low rpm, such as when you stay in top gear going up a hill.

There are several causes, and many cures.





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[vibrostics]

Greg,

Is that associated with any specific mode shape? What are the considerations needed in terms NVH like engine mounting points.. etc.
Thanks.

 

[Rob45]

You have high levels of low-frequency inputs because of the low firing frequency at low engine speeds. High levels because of the high loads.
It would be worse with a 4-cyl engine than with a V-8, for example, because of the lower frequencies at a given RPM.

Considerations?
One is to make sure that your exhaust system doesn't have a primary acoustic mode identical to a cabin acoustic mode.
Then you'd have something like the "Corvette boom" noise.

Another is make sure the powertrain in general and the exhaust in particular is well-isolated from body panels having low-frequency modes.

Another is to assure that items like a transmission support cross-member don't have resonances in undesirable operating frequency ranges. Early Jeep Grand Cherokee, for example.

Good luck