paddlenbike

iTrader: (1)

Choose your exhaust system carefully. I have a total of $618 invested in a cat-back system for my Supra and I don't like it at all. It sounds really good between 3,000 and 6,500 RPMs, but resonates so loud below 3,000 RPMs that you can't hear yourself think. I had several people tell me that it doesn't matter what kind of exhaust you put on a turbo car, that it will be quiet regardless. Whatever...

The exhaust uses a free-flow cat, a Flowmaster baffled resonator that resembles the factory one and a Dynomax Super Turbo baffled muffler. After four changes to the exhaust and $618 spent, I am removing it and buying the $535 HKS system. (A friend has the same car with the HKS exhaust--it sounds very close to stock.)

Be prepared for noise if you go with a straight-through design.

Dr. Zhivago

Actually, the mufflers you chose in your current system only compound the resonance problem. A Borla Style "Lazy S" muffler will be quieter and drone less. I used to own a Supra Turbo. If I were you, I'd get a 2.5" or 3" Borla and slap on some crush-bent pipe. It'll rock, trust me.

Good Luck!
Dr. Z

paddlenbike

iTrader: (1)

Dr. Z, can you explain this? I am still trying to figure out where I went wrong on this system. What I didn't tell you was this is actually my fourth exhaust setup in less than one month. It all started with a high flow 3" cat, 3" mandrel bends all the way to a Xcelerator brand straight through muffler on the back. It was loud as hell. The shop then added a 24" long glasspack after the cat and before the muffler--it helped a little. I figured the straight-through muffler was the problem, so I had that cut off and had the baffled Dynomax muffler installed. That may have dropped the sound level 1 db, maybe. Finally, I had the glasspack taken out and a Flowmaster baffled resonator installed--don't think that changed a thing. The only difference in appearance between my exhaust and the nice, quiet HKS system is the physical size of the rear muffler--the HKS is much larger and could probably be the reason why mine is so much louder. But look how many times I've been wrong so far.

paddlenbike

iTrader: (1)

BTW, I apologize for hijacking your thread Patrick. Maybe we can all learn something from my foolish mistakes.

HBoss

Started this into a new thread for you, paddlenbike.

Al

Dr. Zhivago

Well, when you say loud? How loud is loud? I never drove my car below 3000 RPM on the freeway, so that may be part of your problem. Sorry, I couldn't resist. My system was deep in tone at low RPM's and it wasn't loud in the cabin, but it was loud outside.

Chambered mufflers like the Flowmaster or DynoMax SuperTurbo will enhance any resonance problems you have because that's what they're designed to do. Well, not enhance problems, but resonance, yes. The chambers inside them are designed to enhance the low tones by removing the high-frequency tones, which can make them drone-y. I don't have any personal experience with the Xcellerator mufflers, so I can't comment on why it was too loud for you. It could be that it's designed to be louder.

A Lazy S muffler has the best flow characteristics and usually a decent volume. But, what's quiet enough for one person, may be too loud for someone else. Turbos by nature have a somewhat muffled exhaust note because all the exhaust is funneled through the turbo's impeller housing and out the exhaust port. I ran my car without a muffler for quite a while. Pairing a turbo car with a muffler designed to enhance low tones can lead to an unpleasant exhaust signature.

One thing that comes to mind is leaks. Are you POSITIVE that you do not have any leaks? Another thing that comes to mind is the High-Flow Cat. That's possibly the culprit. IT might be resonating and giving off a horrible sound that is hard to fix. Are you sure the unpleasant note is coming from the exit of the exhaust and not somewhere upstream?

Maybe if we talk about it some more, we'll pinpont the source of the problem.

Dr. Z

Patrick D

Hey no worries man, you don't have to apologize everyone is cool on this forum . Hey do you have any pics of your car? Especially under the hood?

paddlenbike

iTrader: (1)

The exhaust is extremely "boomy" between 2000 and 3000 RPMs, almost as if you had 20" subwoofers in the back playing the same deep note.

I was bored so I set my video camera up and did a couple of passes. As it turns out, the exhaust is not too loud outside, it just resonates *inside* the car.

Hmm, my first setup had a straight through muffler and it sure wasn't any quieter. If a baffled or chambered muffler enhances low tones, what kind of muffler suppresses them?

The shop has looked at the exhaust four times now, so I don't think there is a leak--it sure doesn't sound like it's leaking. One thing I've noticed about both of the mufflers the exhaust shop tried on the rear of my car were dual outlets (like the stock exhaust), but I think these two particular universal mufflers were designed to have exhaust pipe after them---in other words, perhaps they weren't tuned to be hanging off the back of the car. Who knows...I've tried so many different things to no avail.

I'll keep thinking about this one....thanks for the help.

paddlenbike

iTrader: (1)

I am such a geek. I was bored so I got the 8mm out and shot a few videos. I learned something...the car sounds great outside but not so good inside.

The first video shows the dashboard (including tachometer) so you can see where the resonance starts on deceleration. I made a few passes to the redline, but focused on trying to capture the sub-3,000 RPM resonance. The subwoofer on my computer vibrates when the tach gets below 3K. The camera fell over twice when the boost kicked in.

Go here ( http://home.off-road.com/~kemanuel/Supra-vids/ ), right click and do a "save as" on inside.avi (3.9MB)

I shot the other two for fun.

behindexhaust.avi (740kb) is exactly that--I set the video camera behind the exhaust and revved her up. You can hear the turbo spooling on some of the revs.

I did a couple of full throttle starts just to see how it sound outside. The car sounds pretty darned good in this vid: takeoff.avi (3.2MB)

I know, I am such a nerd...

Mog

I just had a dynomax super turbo installed with monza resonating tip this weekend. I find it super boomy/ annoying at rpms under 2000. Been giving me a headache. Hope i'll get it used to it.

paddlenbike

iTrader: (1)

I don't have any good pics, just a couple I took when I bought the car:

7M-GTE engine

Front-end getting new paint next spring

Side shot

I bought it less than 3 months ago for $700. I will have a lot more than that in it by the time it's done.

Patrick D

Damn thats a nice deal! Personally I like the sound of your exhaust both inside and out, sounds like a race car .

When you were doing the 3 drive-bys what was that high-pitched shreeking sound that came from your car?

paddlenbike

iTrader: (1)

turbo.

Dr. Zhivago

Hey,

Sorry for taking so long to reply to this, but I wasn't at home yesterday. I listened to / watched the vids you posted. It's hard to get a sense of how loud it is in the car, but it does seem to have an awful lot of low end and hardly any midrange. It could be that you used 3" tubing. I used 2.5" on mine which would have less low end sound. The outside sounds remind me of what my car sounded like.

I think the Cat has something to do with the excessive resonance inside the car. That's my best guess, but I could be wrong about that. Has any of the heat shielding been removed? Or are any of the interior panels in the rear of the car missing? The hatchback area is a great acoustic chamber to amplify resonance. If any of the stock panels or sound absorption materials are missing, that would cause some problems.

I should have clarified a bit more about the chambered mufflers. Since they are hollow and have NO packing in them, they can become very rumbly or "echo-y". On a V8, that can be really cool, if you like that sound. But I know a lot of exhaust guys who don't like them and recommend a Straight Thru muffler over them, especially on a Turbo car.

Your thinking about the mufflers chosen thus far being designed for a more Upstream application rather than the Terminus of the exhaust system is probably correct. Maybe a different muffler would help. I'd choose a Borla if it were my car. A SHORT one, around 14" long max. The shorter the muffler, the less the low end should be enhanced.

Does the shop that did the work agree with you that the sound of it is not pleasing below certain RPM's? Or do they not care? I would hope that they are willing to work with you to make you happy.

I hope you get this solved. Good Luck!
Dr. Z

Dr. Zhivago

One more thing: I'd lose the Glasspack since it made no difference in tone and is just another restriction now.

Peace!
Dr. Z

paddlenbike

iTrader: (1)

It may seem like I am picking your post apart, but I just want to make sure I have my facts straight.

When I watched the video on my television, I couldn't hear the rumbling below 3,000 RPMs. When I watched on my computer which has a subwoofer system, the rumbling would shake my entire computer desk. Time to upgrade your speakers! lol. But I have always known a larger exhaust to take away low-end power. I have NO problems with low end, but you are correct, top end power is lacking. There are two main reasons; one is that these motors have a long stroke and a small bore, which means they are low end torque motors and not top end power makers. The second reason is my turbo makes 7 pounds of boost at 2200 RPMs and fades to 4.5 pounds at redline. An electronic boost controller will "fix" this issue.

Good point, but all heat shields and interior parts are in place.

You are correct. As you may recall, the first exhaust setup on my car used a straight through muffler. When I had that cut off and the baffled Dynomax installed, the sound levels were barely reduced at all. I was expecting there to be a much larger difference in sound between the straight-through and the baffled. Just one of my many exhaust misconceptions.

I don't know that I necessarily agree with you on this one, but I am trying to keep an open mind and understand. One thing about my exhaust versus the quiet HKS system is my muffler is much shorter and not as large. I tend to think the larger the muffler, the more sound cancellation will occur. Ever heard a diesel without a muffler? That's why my dad's Cummins turbo diesel has 55 gallon barrels for mufflers.

The shop thinks the car sounds awesome. I agree, it does sound awesome outside the car. But they say policy prohibits them from driving customer's cars or riding with a customer, so they can't experience the buzz. I really don't think they care. But they have been respectible, giving me as much credit as possible when I have made changes. They charged me $45 for the glasspack, including cutting the exhaust up to fit it. They charged me $45 to cut the Xcelerator brand muffler off the back to install the Dynomax. They charged me $130 to cut off the glasspack, replace with straight pipe, cut the system elsewhere to install the Flowmaster resonator. Could have been worse.

In all honesty, I think I am going to cut this exhaust off and just buy the HKS. There are too many other variables for me to dump more money into this exhaust. The 3" pipe could be thinner than the HKS system, the resonator may not be in the right physical location or of the right volume/design inside to reduce certain resonances, I suspect the muffler is physically too small and is not designed to be the end of the system (described above)....who knows. This has been very interesting though and believe me, when I replace the muffler on my truck, I am having a stock one installed...I know they are quiet!

One more thing to add--the shop added a 3 pound counterweight near the rear of the exhaust. Apparently Ford and Lexus use many of these on their high-end cars. This did more to reduce the resonance than anything. The resonance used to start around 3,000 RPMs, now it's down to 2,700. Maybe I need about 20 more 3 pound weights!

I'm sure everyone on this board thinks I am being too picky, but everyone that has ridden in the car thinks it is damn annoying.

BTW, the glasspack was cut off one week ago and replaced with a Flowmaster baffled resonator.

Thanks for all your help!
Ken

paddlenbike

iTrader: (1)

It looks like Christmas at this guy's house! :eek:

The HKS exhaust is the black one on the far left in the pic.

Dr. Zhivago

Alrighty! Well, good luck and the HKS is probably the way to go.

Have a Mery Xmas!

Dr. Z

paddlenbike

iTrader: (1)

hehe, I hope I didn't frustrate you too much.

Dr. Zhivago

No, not at all! That was fun, you big weenie!

Peace!
Dr. Z