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Old 12-01-2011, 09:31 PM   #1
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Default Help Quiet Awful Intake (?) FM2 Sound

Hey...

I am really liking the power of the turbo, but absolutely despising the sound under the right side of the hood under acceleration. Not 100% sure what it is. I love the whoosh sound of the blow off valve, that's not the problem. The problem is that under just about any acceleration, the sound coming from the engine (air filter?) sounds like metal shreds bouncing around (very hard to describe sound and i have never heard this sound on my NA miata or on a Superchargered miata that i remember, but sure hear it on the turbo!

I actually took the custom 3 inch exhaust that had no cat (didnt have to do smog test in Oklahoma) and i took OFF the muffler, and it was loud but i liked it since it mostly drowned out the awful sound from under the hood...now, in Texas and have to add a cat and at least a resonator/muffler, so now the exhaust will be much quieter and i will hear that grating sound upon acceleration all the time. What can i do about this? Is it the K/N air filter making this sound. Is there a way to deaden it?

The car is a 95 so enclosing it in a sound deadened box will not work i dont think since the headlights are right in from of the air filter box and i couldnt run a hose to the front to get air into the filter...

I found this thread about using foam...does that really work? It seems that it would keep air from reaching the air filter at all!

http://forum.miata.net/vb/showthread...r+filter+sound

This sounds petty, but it makes me want to take the turbo off just because of that awful sound...its the only sound i have ever heard from an engine that i hated. I like old sports car loud, but not this weird grating metallic sound...

Thanks!
Randy
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Old 12-01-2011, 09:33 PM   #2
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It's a 1995 with FMII turbo kit gt2560 by the way...surely there has to be a way to muffle this very hard to explain and loud sound coming from what must be the air filter...again, i love the BOV whoosh sound, hate the continuous sound coming from under the hood upon acceleration...

Randy
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Old 12-01-2011, 09:57 PM   #3
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the only noise hte turbo should make is a whooshing sound of air being sucked in. anything else is not good...
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Old 12-01-2011, 10:00 PM   #4
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Metallic rattling.... Does it sound like a bunch of grains of rice being dropped onto a sheet of aluminum foil?
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Old 12-01-2011, 10:09 PM   #5
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It sounds like you may be experiencing detonation.
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Old 12-01-2011, 11:06 PM   #6
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is it sad that didn't even cross my mind. marbles in a can?
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Old 12-01-2011, 11:28 PM   #7
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sounds like detonation. i just recently heard that noise for the first time while trying to road tune my sled. I really dont know how much detonation a car can handle...from what ive read itll blow headgaskets and destroy rod and crank bearings very quickly. really sounded like valve train noise and the funny thing is that the car will still accelerate pretty hard while its happening so its pretty deceptive. when it happened to me i really diddnt know what it was i thought something was rattling around in the trunk cuz i was hauling *** and the car was pulling hard running nice and rich, having never experienced pinging or detonation before i really expected the car to like hesitate or something but nah it still pulls. i thank the car gods that my motor is not knocking but yea man be very careful thats all i can say.
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Old 12-02-2011, 12:55 AM   #8
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Are you running a Hydra? How much boost are you running? Do you have any logs to upload that are taken during the bad noise?
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Old 12-02-2011, 10:33 AM   #9
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First of all, its not a new FM2 turbo like a hydra, its the older one...running 9.5 or so lbs of boost...

The sound is during any acceleration and all thru the band at about the same level of sound.

Was thinking on the way to work how to describe the sound...very hard to describe, but maybe imagine air going thru a metal can that has metal pellets in it, and the can spinning upon acceleration, causing the metal pellets to bounce around in the can, along with the loud sound of air going thru the metal can...its very noticeable to me and it really bothers me (only sound that has ever bothered me on a car before!)...again, i was able to deal with it up to now due to having a very loud exhaust mostly drowning it out, but can't do that anymore as Texas law requires a cat and a muffler or resonator...

Hadn't thought about detonation...if it's that, then the car has been doing that for over 5K miles of driving it, wouldn't that have destroyed my engine by now?!

The car is about to be totally retuned by Gary Schuhart of Track Dog Racing in Dallas. He says he can make it run much better, but due to the loudness of the no-muffler exhaust, he didn't really notice the sound i am talking about yet (he will once we put a cat and muffler on it though for sure!). If it IS detonation, then Gary will fix that no doubt...again though, that would have toasted my engine by now, right? So, it has to be something else i would think, and the only thing i can think of is the air filter, and it SOUNDS like the sound is coming from right about there when driving it, but its so hard to tell on sounds where they are actually coming from...

Keith of Flying Miata messaged me and said that you CAN put foam around it (the right kind of foam) and really deaden the sound, and that the intakes on a turbo are much louder than the intakes on a N/A (maybe much loader than on a Sebring Supercharger too, which i had before?), so that is why i am noticing the sound now and didnt on my previous miata, he says.

I need to drive some other people's FM2 turbos and also some K/N filtered NAs and K/N filtered supercharged cars to get a comparison...

Given that the headlights are right in front of the air box, can i build an enclosed box around the air filter and somehow still get air to the filter? Keith of FM also said that FM is working on a enclosed top for the air filter box, but how would air get into the air filter with that?

I know this whole thing sounds petty, but i really hate that sound, and now that my exhaust is going to be not ridiculously loud, i will really hear that sound every time i accelerate, so i have to find a way to get rid of it or it will seriously detract from the enjoyment of driving the car!

Thanks
Randy
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Old 12-02-2011, 10:37 AM   #10
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Quote:
Originally Posted by Braineack View Post
is it sad that didn't even cross my mind. marbles in a can?
Close, read my description below...

What exactly would detonation sound like?

It ALMOST sounds like valves clattering (it has a metallic sound to it on some level, but also an air sound at the same time)...

Again, it is NOT the BOV whoosh sound, that sounds great and is a totally different thing than this constant upon acceleration sound...

Randy
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Old 12-02-2011, 10:39 AM   #11
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Quote:
Originally Posted by Jeff_Ciesielski View Post
Metallic rattling.... Does it sound like a bunch of grains of rice being dropped onto a sheet of aluminum foil?
Maybe metal rice being dropped on a sheet of aluminum foil, along with the sound of air in there somehow too...

Randy
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Old 12-02-2011, 10:49 AM   #12
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That definately sounds like detonation to me. My car does the same rattle sometimes when I hit near 7psi. It's not my tune, it's the fact that my car burns so much oil, and burning oil causes det. It's been like that for a while. If I was running a bigger turbo and more boost, I would've broke something a long time ago. If you're not burning oil, then it has to be in your tune. Are you running a Link?
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Old 12-02-2011, 11:03 AM   #13
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what you describe sounds exactly like detotation. Is the same noise made when accelerating with little to no boost?
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Old 12-02-2011, 11:03 AM   #14
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fail thread, lol. I feel for ya man, now get the checkbook out and try again. Where are you in OK?
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Old 12-02-2011, 11:15 AM   #15
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Quote:
Originally Posted by rainman10 View Post
The car is about to be totally retuned by Gary Schuhart of Track Dog Racing in Dallas. He says he can make it run much better, but due to the loudness of the no-muffler exhaust, he didn't really notice the sound i am talking about yet (he will once we put a cat and muffler on it though for sure!). If it IS detonation, then Gary will fix that no doubt...again though, that would have toasted my engine by now, right? So, it has to be something else i would think, and the only thing i can think of is the air filter, and it SOUNDS like the sound is coming from right about there when driving it, but its so hard to tell on sounds where they are actually coming from...
There is a reason I use electronic det-cans and don't rely on a knock sensor. A lot of "professional tuners" think a knock sensor does the job and that it's archaic technology (the human ear, lol). I've also been running for three years on a "suicide" spark table and tuned 4 track cars that are still running just fine.

I've seen some racecars loud enough that you can't hear detonation in the car on the track, and they run all season, gradually chipping away at pistons and the head.


Wait, is your car that ice-blue color?
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Old 12-02-2011, 03:58 PM   #16
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fail thread, lol. I feel for ya man, now get the checkbook out and try again. Where are you in OK?
Hey Hustler...no, I am back with a good long term job in Dallas (McKinney actually), so Track Dog Racing is close to me (and so are you!)...

Yes, my car is not 'ice-blue' it's powder (think gulf racing or old 60s TR3 blue)...very cool color i think...

Randy
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Old 12-02-2011, 04:04 PM   #17
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Quote:
Originally Posted by Braineack View Post
what you describe sounds exactly like detotation. Is the same noise made when accelerating with little to no boost?
Yes, it makes that sound without boost kicking in i am sure, would have to look at the boost gauge on acceleration again...

This is sounding really bad...leak down and compression test recorded two weak cylinders also, but Gary at Trackdog said that I could go another 2 years or so with living with it burning some extra oil before needing an engine rebuild...

If it is detonation, then can that be fixed with proper tuning, or both proper tuning AND an immediate engine rebuild...engine rebuild is $$$...not good...

Gary has not had a chance yet to play with the car other than a couple of quick spins (with the really loud exhaust, so he claims to not hear the sound i am talking about), so he may quickly figure out its detonation upon starting to retune it...

Randy
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Old 12-02-2011, 04:05 PM   #18
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By the way, its not one of the new FM2s and i have a megasquirt + LC1

Randy
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Old 12-02-2011, 04:10 PM   #19
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Trollollollo?
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Old 12-02-2011, 04:15 PM   #20
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Quote:
Originally Posted by rainman10 View Post
Yes, my car is not 'ice-blue' it's powder (think gulf racing or old 60s TR3 blue)...very cool color i think...
Seriously?

Show us your fuel and spark tables. Is TDR going to use a dyno or drive it up and down the street to tune it?
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