The Grapes of Rasp

[Swolzee]

BREAKING NEWS, this just in. A catless exhaust is loud AF!

My setup:
- JDL 4-2-1 EL,
- 2.5" stainless OP
- 2.5-3" stainless FP
- Perrin 3" resonated CB

I'm not sure what my expectations were initially but this wasn't it. The db's are a real thing but the raspyness of it is unreal. I have had many loud exhausts from many types of 4cyl and that's certainly a factor but the rasp is next level.

I could live with the db's being what they are especially once I get my rear seat delete barrier installed with acoustical foam glued to the back and I drop a bag of rockwool safeNsound in the spare tire and rear seat cavities.

To directly combat the issue I first plan to install the 5 STI exhaust cushions (there is a tremendous amount of vibration resonance), and weld in a 3" vibrant ultra quiet resonator into the FP.

Are there any other recommendations to help eliminate the rasp?

[spcmafia]

Originally Posted by Swolzee

BREAKING NEWS, this just in. A catless exhaust is loud AF!

My setup:
- JDL 4-2-1 EL,
- 2.5" stainless OP
- 2.5-3" stainless FP
- Perrin 3" resonated CB

I'm not sure what my expectations were initially but this wasn't it. The db's are a real thing but the raspyness of it is unreal. I have had many loud exhausts from many types of 4cyl and that's certainly a factor but the rasp is next level.

I could live with the db's being what they are especially once I get my rear seat delete barrier installed with acoustical foam glued to the back and I drop a bag of rockwool safeNsound in the spare tire and rear seat cavities.

To directly combat the issue I first plan to install the 5 STI exhaust cushions (there is a tremendous amount of vibration resonance), and weld in a 3" vibrant ultra quiet resonator into the FP.

Are there any other recommendations to help eliminate the rasp?

Catless FP are a contributor to rasp on a setup, due to proximity to headers. A double resonated one like HKS would be ideal. Or even a HFC. The JDM hangers will help with vibrations/drone. But other than that it would come down to Catback choice.

[Swolzee]

Originally Posted by spcmafia

Catless FP are a contributor to rasp on a setup, due to proximity to headers. A double resonated one like HKS would be ideal. Or even a HFC. The JDM hangers will help with vibrations/drone. But other than that it would come down to Catback choice.

This is correct.

So who wants to buy a catless front pipe lol.
I went ahead and swapped back in the the stock front pipe and it resolved about 75% of the rasp and actually improved the sound to a deeper burble not as sharp and tinny. Free flow and HP be damned, it was intolerable.

Thanks!

[wbradley]

I thought this was a.discussion of Steinbeck's work.

[cmiovino]

I was just popping in to say the OEM front pipe is really good at keeping rasp at bay, especially with catless headers people often go to. Remember that swapping to aftermarket front pipes tend to only net a few minor whp and it's generally not worth the money and added headache (literally).


If you're running a catless header, stock front pipe, and still have volume/rasp issues, it's likely the catback you're running at that point.

[JBezugs]

I have the JDL 4-2-1 header as well but with no real rasp to speak of. Like others have stated, that's because of using the OEM front pipe with the OEM cat. My catback is a bit drony at highway speeds when under load (going up hills) between like 120-135kph, but the JDM "exhaust cushions" (Hangers) cured maybe 50-60% of the drone. I'm still looking to add a vibrant resonator to it to help curb the remaining drone, or just swapping the catback out all together and going back to stock there, as I drive all highway these days.

With the swap you've done on the front pipe, that's a huge help! But with JDM STI hangers, you should see a significant cut down of drone on your setup as well.

My setup:
- JDL 4-2-1 Header
- Stock OP
- Stock FP
- Invidia R400

[Racecomp Engineering]

Originally Posted by JBezugs

I have the JDL 4-2-1 header as well but with no real rasp to speak of. Like others have stated, that's because of using the OEM front pipe with the OEM cat. My catback is a bit drony at highway speeds when under load (going up hills) between like 120-135kph, but the JDM "exhaust cushions" (Hangers) cured maybe 50-60% of the drone. I'm still looking to add a vibrant resonator to it to help curb the remaining drone, or just swapping the catback out all together, as I drive all highway these days.

With the swap you've done on the front pipe, that's a huge help! But with JDM STI hangers, you should see a significant cut down of drone on your setup as well.

My setup:
- JDL 4-2-1 Header
- Stock OP
- Stock FP
- Invidia R400

Do you run all 5 JDM hangers?

Is the Rage Against the Machine version of "The Ghost of Tom Joad" better than the Bruce Springsteen original?

- Andrew

[RToyo86]

You'll want a cat to help with rasp.

I took some back to back when I had a HKS dual resonated installed vs a 2.5" high flow catted and resonated FP, both with OEM catbacks. Catted setup removed the rasp.

The rasp with the UEL headers was only low RPM and heavy load. Obviously different headers, I don't imagine you'll get rid of all rasp with just resonators.



Sidenote, got any exhaust clips? My JDL is showing up any week now and I'm always looking for options.

[JBezugs]

Originally Posted by Racecomp Engineering

Do you run all 5 JDM hangers?

Is the Rage Against the Machine version of "The Ghost of Tom Joad" better than the Bruce Springsteen original?

- Andrew

Yes to both inquiries!

This is what the setup currently sounds like for reference. Mic is placed on the rear bumper.

[Spuds]

Originally Posted by RToyo86

You'll want a cat to help with rasp.

like this?

[kevaughan]

I did the STI hangers (two the rear) and a Vibrant Resonator. Drone was significantly reduced. OEM front pipe helped the most of course.

[JBezugs]

Originally Posted by kevaughan

I did the STI hangers (two the rear) and a Vibrant Resonator. Drone was significantly reduced. OEM front pipe helped the most of course.

Which Vibrant resonator did you end up getting installed? Did you install it onto the front pipe, or on the catback portion?

[Grady]

Best way to eliminate rasp is to install a turbo!!!!!

[Lantanafrs2]

After the header, stock is best