Noisy, thrashing engine is getting old.

[Woodie]

Isn't it every 3dB increase appears as twice as loud to the human ear? That puts a new perspective on the noise levels in some of those other vehicles!!

No, it requires twice as much power to increase the SPL by 3dB. I think 10dB is perceived as twice as loud.

[LPSISRL]

Wouldn't out of spec tappets generate a noticeable clicking sound at idle that wasn't there before?

[murcod]

Isn't it every 3dB increase appears as twice as loud to the human ear? That puts a new perspective on the noise levels in some of those other vehicles!!

No, it requires twice as much power to increase the SPL by 3dB. I think 10dB is perceived as twice as loud.

http://www.sengpielaudio.com/calculator-levelchange.htm my brain hurts after reading that!

Wouldn't out of spec tappets generate a noticeable clicking sound at idle that wasn't there before?

I'd imagine it would be more noticeable at higher revs.

[Ronzuki]

Isn't it every 3dB increase appears as twice as loud to the human ear? That puts a new perspective on the noise levels in some of those other vehicles!!

No, it requires twice as much power to increase the SPL by 3dB. I think 10dB is perceived as twice as loud.

http://www.sengpielaudio.com/calculator-levelchange.htm my brain hurts after reading that!

Wouldn't out of spec tappets generate a noticeable clicking sound at idle that wasn't there before?

I'd imagine it would be more noticeable at higher revs.

Nope, idle would be far more noticeable to the naked ear. I always know when I need to go over the Samurai's adjustment, its clacking gets louder at idle. Purrs nicely when I winder-up on hill climbs and such. Too much other engine noise masking a little valve tick at high rpms to be noticeable. If it is noticeable or gets louder at the higher R's...well, you've got some serious issues then that aren't going to be resolved by a simple lash adjustment. Besides, there's the whole VVT aspect of these engines to consider now. Haven't looked at a breakdown of the mechanics, but I'd imagine it's a fairly complicated ordeal as compared to the non-VVT engines.

[murcod]

Has your Samurai got an engine driven fan (eg. viscous coupled etc)? You've got no hope of hearing any engine noise over them at high revs. I converted my XL-7 to twin electric thermos and it's amazing how quiet it is in comparison. They hide a lot of mechanical noise.

[sx4rocious]

a simple, cost effective solution that would solve the loud engine issue AND make the car appear more refined at highway speeds (assuming all mechanical issue have been worked out) would be to add a couple layers of Dynomat to the firewall and floorboards.

[redmed]

a simple, cost effective solution that would solve the loud engine issue AND make the car appear more refined at highway speeds (assuming all mechanical issue have been worked out) would be to add a couple layers of Dynomat to the firewall and floorboards.

Dynomat has worked for me. Engine & highway noise reduced significantly in my Toyota Corolla which is not known as a quiet car.

[Ronzuki]

Has your Samurai got an engine driven fan (eg. viscous coupled etc)? You've got no hope of hearing any engine noise over them at high revs. I converted my XL-7 to twin electric thermos and it's amazing how quiet it is in comparison. They hide a lot of mechanical noise.

yep, viscous coupled fan. Makes no difference, with zero insulation anywhere, no carpet or matting, a soft top and no doors, I can hear every noise that thing makes and know the diferences between them all.

[11zukizashi]

Hi, I also noticed that my engine sounds louder recently after i replaced the air filter at 30,000 miles. I did not use an oem filter i used a cheap one from rockauto. Maybe that is our problem?

[KuroNekko]

Hi, I also noticed that my engine sounds louder recently after i replaced the air filter at 30,000 miles. I did not use an oem filter i used a cheap one from rockauto. Maybe that is our problem?

From my experience, I've found that air filters have a lot do with engine noise. While I did not notice much noise nor performance increase from replacing a regular panel filter with a K&N drop-in filter in my Impreza, a cone SRI-type filter made a noticeable difference. The intake got noisier and could be heard even in idle. The engine was much more throatier and RPMs revved up faster. It was a neat and cheap upgrade though I doubt it added any considerable HP.

When the intake sounds noisier than it should, make sure that the air filter box is properly closed and the gasket is sealing properly. I once had a noisy intake after replacing an air filter and then later noticed that the air filter box was not closed properly. Once it was set properly, the intake noise disappeared.

I'm about to hit 30K miles and will be ordering a new air filter very soon given stores don't seem to carry the one specified for the Kizashi.