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.

metalic rattle on decel sound mechanical ie exhaust hitting on something

I'm glad this is normal. I also experienced this after flashing the Stage 1 OFT tune to my BRZ and was hoping this new sound wasn't something wrong.

Well there's some dispute and no one can actually explain what (specifically) is causing the noise. Everyone seems to just be ok with the "it's the variable valve timing, bro" explanation, but I've never seen anything more specific than that.

I just fitted up a PSR + over pipe and flashed the OTS Stage 2 UEL e85. I have the exact same symptom.

The vibration is hideous, in that very narrow band around 4K. Obviously the alignment of something changed in the removal and refitting. I wonder if it's related to the mid pipe hanger, it seems to be coming from right under my seat (RH drive). I undid that at the pipe end to get the over pipe out.

Has anyone hunted down what this was? I'm not really looking forward to getting back under the car and looking for it.

For me the sound changed over time and after about a week it was clearly the VVT. It actually became harmonious and pleasing to the ear lol.

However your description is more a vibration and not a sound onlu, so I'd say it's probably not from the VVT

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sounds like overpipe on the front sway bar mount.

try this,

undo the midpipe hangar bolt completly, move the bracket with hole in it aboce the bolt hole and replace bolt so bracket is now above bolt, this will loft mid pipe and overpipe slightly. Put large washer on bolt and tichten with bracket still above bolt.

see if that helps

Did you get new ones with the slip joints above the tubes or second hand ones that are below? If they're the old ones it will rub at exactly 4k.

Is it advisable to try to remove this noise from the Stage 2 EL E85 tunes? I installed a Perrin CAI and ran the stock tune. The intake sound is absolutely awesome.

Then I installed the Stage 1 EL 91 tune, the 4k rasp just completely overshadowed the CAI noise... :( I can only hear it at 3000-3500rpm, then from 3500-4000 it's just a high shrieking noise lol.

Went to the Stage 2 EL E85 tune and absolutely love the smoothness of the car now. Absolutely wonderful.... until 3500rpm again.

Ideally I'd love to be able to run E85 and NOT have the rasp. I can live with the torque dip.

Hissing/rattle from 3.5-4k RPM after OFT
 

@Wayno @steve99 thanks guys. I do have the slip joint on the bottom - so looks like the way I can choose between the two scenarios would be to remove the alloy tray and take it for a drive. Does anyone know if the rear fibrous tray is secure without the alloy tray - or should I remove that before driving as well?

Assuming it's the slip joint is there something I can put between the tray and pipe that will survive heat and abrasion or am I taking a dremel tool to the plate to make a new window?

you might just be able to just dent the tray. look for the rub mark and put a dent in that area

The heat shields on my o2 sensors rattled because the sensors were not seated all the way. Always rattled around 3500 rpm. I could watch them spin while someone else revved the car.

Exactly. Use a hammer. The metal isn't that hard. Don't drive without the skid plate

This means sensors not screwed in all the way, this can cause incorrect reading as sensor tip not in exhaust flow or leaks.


Best to remove sensors, run a M18 by 1.5mm pitch thread tap/chaser through 02 bungs in header then sensors will seat properly

Hissing/rattle from 3.5-4k RPM after OFT
 

Well, I found the culprit. It was indeed the rear slip joint touching an inopportune bulge on the skid plate.

Not any more.
http://www.ft86club.com/forums/pictu...988912&thumb=1

Ok - found my original post. Below...