Hissing/rattle from 3.5-4k RPM after OFT
 

Hey guys
Running Stage 1 program on the OFT. I have a TRD catback. After 1 tank of gas I've noticed its very nice, open and smooth. Sounds a lot better too.

However from 3.5-4k RPM I notice what sounds like a rattling from under the hood. It's so short in duration thats almost like a hissing sound...

Any thoughts on what this could be? Is it a boxer thing? Airflow changes? Should I be concerned? Any ideas on how I could investigate/check it out further?

Much obliged gents...

AVCS. all vendors do it for stg1 to reduce the dip

AS stated, its the cam timing. Tuners make it very aggressive to help with the dip. It's a resonance, nothing serious or anything to worry about.

Excellent. thanks for the confirmation
I actually like the sound.. Very addictive :-)

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To expand on the previous answers, the tunes for EL headers (including stock with the OFT stg1) will have that aggressive cam profile. Tunes for UEL headers don't make that noise.

Ahh Ok good to know.

Will gladly exchange the 2 seconds of resonance for some o dat UEL gurgle ;-)

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The UEL tunes absolutely make the same noise. Mine does it right at the same RPM the OP mentioned. Emails to Shiv confirmed this. Running OFH and OFT.

Basically it's nothing to worry about. It's pretty annoying though.

Weird. I had the noise when i was on stg1 with stock header, but now that I'm on stg2 with a catless UEL, the noise is gone.

I'm not running an OP or catback. Maybe it's just more audible since there isn't as much noise?

I would check you actually running the UEL tune as the cam timing are different in the UEL tune so it should not make the raspy noise arround 4000.like the EL header tune or stage 1 tune.

The noise may also be the overpipe or some other exhaust component loose or hitting on subframe or skid plate or plug up the sound tube

I've been running stage 1 oft tune for about half a tank and haven't noticed any noise difference in my nameless axleback. Only difference I can feel is maybe a little smoother 1st gear. Will the car and exhaust be feel and sound smoother after a full tank?? Also, the dead pedal effect is still slightly there, but not as bad as right after a fresh flash.

I have wondered about the rattle. Maybe it's time to get the car back up on the lift.

There's a snake in your boots

Checked last night and it is the UEL stg 2 tune. Running the Grimmspeed intake so no sound tube. The noise is definitely metallic in sound. There is some hissing noise too but normal for an aftermarket header from what I can tell. The metallic rasp is what bothers me. It's pretty loud. It's noticeable upon acceleration but VERY noticeable upon decel.