Help to quiet HKS hi power on S13

[Scb1712]

Hi all,
I’m new to the forum but have been lurking for a bit. I’ve got a mostly stock 92 S13 coupe with the KA motor, and just installed a HKS Hi Power cat back exhaust. Outside the car it sounds fine, but inside it’s deafening! It runs about 95db while cruising at highway speed. I don’t know it it’s just how noisy the exhaust is, or if it is just resonating the car to produce a lot of cabin noise. Any suggestions on how to quiet it? Dynamat? Anything? Thanks

[afishysilvia]

Hi all,
I’m new to the forum but have been lurking for a bit. I’ve got a mostly stock 92 S13 coupe with the KA motor, and just installed a HKS Hi Power cat back exhaust. Outside the car it sounds fine, but inside it’s deafening! It runs about 95db while cruising at highway speed. I don’t know it it’s just how noisy the exhaust is, or if it is just resonating the car to produce a lot of cabin noise. Any suggestions on how to quiet it? Dynamat? Anything? Thanks

Does your trunk have all of the little rubber grommets near the spare wheel? Is the rest of the exhaust stock?

[Btaztic]

Welcome!

I would suggest starting off by getting a silencer for your exhaust, that is if you don't already have one. They're fairly inexpensive and can make your exhaust a bit quieter. It is a far easier solution than doing sound deadening or anything like that. Enjuku sales one for about $50.

[Scb1712]

Does your trunk have all of the little rubber grommets near the spare wheel? Is the rest of the exhaust stock?

I’m not sure what rubber grommets you’re referring to but I don’t think anything’s ever been taken out of the trunk. And yes-the rest of the exhaust is stock. Was considering switching to the ISR MBSE Type E Catback système instead. Any thoughts?

[Scb1712]

Welcome!

I would suggest starting off by getting a silencer for your exhaust, that is if you don't already have one. They're fairly inexpensive and can make your exhaust a bit quieter. It is a far easier solution than doing sound deadening or anything like that. Enjuku sales one for about $50.

I’ve read that the silencers only reduce the noise by about 7db. That will still leave me around 90db at highway speeds.

[jedi03]

I would reinstall the sound deadening material in the doors, dynamat or similar...theres many ways to reduce exterior noise...

[unicoder]

I have this exhaust, and it is not loud in my car at all. I would believe something is allowing the sound into the cabin. Maybe some of the interior or underlying sound deafening material has been removed? Maybe a rust hole somewhere letting the sound in?

Make sure your exhaust is hanging correctly and not touching the body, as it could cause loud noise as well

[FaLKoN240]

HKS Hi-Power is one of the quietest exhausts you can buy.

That ISIS MBSE exhaust fits very poorly and if your car is lowered it will scrape itself into oblivion.

[nismo35]

Are you running a header? That exhaust will produce a pretty good noise level at cruising speed on a NA car. I'm running a Super Dragger on my SR car and it's super quite.

[Bnr32gtr]

Go ka-t or get a Sr,rb,jz swap and boom fix no more rice sounds... or just stick a silencer in it if yo cheap ass. They do wonders on na motors. Please don't replace your nice real name brand exh with isr junk

[brndck]

silencer + dynamat

or just get earplugs

[Kingtal0n]

turbo will quiet it down

or put stock exhaust on it

or both (thats what I do)

[Scb1712]

Thanks for all the suggestions. I’ll look into the silencer as well as dynamat or Siless 80mil mat in the trunk, etc. I’d love to swap to a turbo but don’t have that kind of coin to solve this. I had the exhaust installed by a shop but will check it over to make sure it isn’t touching the body etc. Would different hangers make any difference?

[NiSilS14]

I've found adding a resonator or muffler as close to the header as possible noticeably helps with in cabin with certain exhausts. You could try adding a resonator but could mean cutting up the exhaust and HKS hiper is pretty mild for noise. As already mentioned you could add sound deadening in trunk area and/or floor pan to help with noise. Check for exhaust leaks near any flanges, if there's any big leaks, that's noise escaping as well. Solid or poly hangers would help in keeping the exhaust where it needs to be, meaning it could help with minimizing exhaust leaks over time.

[carcrazee]

i also have the hks hi power, I have a SR, it so quiet I can actually hold a conversation inside the car, not sure how this exhaust is too loud lol

[jedi03]

I have been told that if you keep your foot off the gas or key out of the ignition it will also keep the exhaust quiet...sry...I wanted to do one silly post in my life! this is a good exhaust! gl with getting it quieter!

[Croustibat]

OP has a hole somewhere on his exhaust, a leaking gasket or his exhaust is touching the car. There is no way this exhaust makes so much noise.

BTW do not believe your phone when it gives a sound level. There is a reason meters are expensive. Also the procedure of measuring sound level involves setting a distance and orientation from the noise source. And -3dB = sound volume HALVED. This is a logarithmic scale.

[Wookie384]

Dude, you're seriously complaining about noise at 95 db?! That's the legal limit for noise for cars in California. My 2004 Scion xB made that much noise with the stock exhaust! lol

Just get the silencer, what you're hearing is the muffler doings its job. Not much you can do about it other than using the silencer. Just curious do you still have a cat? If you don't that's probably not helping.

[Scb1712]

I am actually switching out the Hi Power exhaust to the HKS sport exhaust instead. It doesn't look quite as ridiculous as the 5" tip on the hi-power and is way quieter.

As for the noise - HKS rate the hi-power at 98 DB. Driving on the highway at between 3300-4000 rpms (~120 km/h) it's impossible to have a conversation without shouting, or even hear the radio. It's just too much for my aged ears to handle.

Thanks for all the help and suggestions though. And if anyone is interested in a barely used HKS Hi-Power, let me know. It's got less than 1000kms on it.

[spooled240]

How old is the Hi-power? The packing may just be shot from years of use or possible backfires/2-step/anti-lag/who knows what lol


The Hi-power is a very quiet exhaust for what it is, especially on a stock engine with stock downpipe and a cat.


I'd say the HKS sport is a bit more quiet, but not silent as it's still a racing style straight-through muffler w/ no resonator.

[Scb1712]

The hi-power is brand new. It’s got less than 1000kms on it. I’ve heard the Sport is much quieter, except for wot. Here’s hoping it is