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Tony Hanna
07-19-2006, 01:26 AM
I'm running a mitsu with a 2.5" downpipe connected to a 3" Dynomax race bullett and 3" side exit. I'm happy with the sound level. With the windows up, you barely hear it as a background noise. The only problem I have is that it pops like crazy on decel. I'm curious as to what causes the popping and what can be done to eliminate it or reduce it significantly. I'm sure going with a different style muffler would do the trick, but I'm short on cash at the moment so I'd like to try a different option. I'm thinking of making an anti-reversion cone similar to what they sell for Harleys with drag pipes, but I'm not sure if it would do any good, or if reversion is even an issue with the turbo smoothing out the exhaust pulses.
Any thoughts and advice would be appreciated.
Thanks,

iTurbo
07-19-2006, 02:03 AM
The only time I get loud popping on decel is when the speed sensor and/or wiring has failed. Are you getting a code 15? Could be a clogged AIS passage too.

turboaddict
07-19-2006, 02:27 AM
my 87 doesnt have a decel lean out as most newer fuel inj. cars have. basically on decel the engine is still being given fuel which burns n the exhuast system. i like the sound of it.

Mario
07-19-2006, 02:29 AM
The only time I get loud popping on decel is when the speed sensor and/or wiring has failed. Are you getting a code 15? Could be a clogged AIS passage too.

That's what I was about to say.

But most of the time when I've had a speed sensor fail, the engine would want to die when I let off the throttle/came to a stop unless I played with the throttle. He didn't mention anything of the sort.

iTurbo
07-19-2006, 04:06 AM
I have two cars right now, both with bad speed sensors. Idle does go a bit low when coming to a stop, but they don't stall, mainly just snap crackle pop out the exhaust on decel. Not annoying enough to fix yet though. Might be worse with auto trans, but I have manuals in all my cars.

Tony Hanna
07-19-2006, 02:24 PM
That might be it then. I'm running an auto trans computer on a manual trans car. Might be the sds too as it does idle a bit low when coming to a stop. It's never stalled though. Would a bad sds cause a check engine light or just set a code? I'll check for a code 15 and clean the ais passage later this evening.
Thanks for the suggestions!

Tony Hanna
07-19-2006, 02:32 PM
Ok, just pulled the codes. It's all clear, nothing but a 12.
I'll check the ais passage later this evening after it cools off some.

tryingbe
07-19-2006, 03:27 PM
My 89 Daytona Shelby pops all the time when I'm decelerating with using the cut out.

It's normal, to stop it, put a muffler on it or shift out of gear.

Dave
07-20-2006, 12:14 AM
It's normal. Just raw fuel being burnt in the exhaust system instead of the combustion chamber.

Garret
07-20-2006, 12:23 AM
unplug the AIS and set your idle manually and the problem goes away, just gotta blip the throttle more when you slow down

butchsuppe
07-20-2006, 01:15 AM
Advancing the timing a tad at a time got the popping out of my car - 2.5" mendral bent, no cat + ultra flow muffler.:thumb:

Tony Hanna
07-21-2006, 12:08 PM
Thanks for all the help. I think the biggest issue is that this computer doesn't have the decel fuel cut. Maybe because it's an auto computer? If I ever get a cal done, maybe I can get that fixed. For now I'll try out some of the suggestions here and if all else fails, I'll just try to find the best flowing quiet muffler I can.

shadow88
07-21-2006, 02:18 PM
Do you run a cat? Mine made alot of popping without one, and nothing noticeable with one.

Darkapollo
07-21-2006, 09:42 PM
naw. my auto pops all the time.. i love it. scares little children.

Tony Hanna
07-22-2006, 12:18 AM
Do you run a cat? Mine made alot of popping without one, and nothing noticeable with one.
Nope, no cat, but it popped with the stock one in place (exhaust was rusted in half before the muffler).

Tony Hanna
07-22-2006, 12:32 AM
naw. my auto pops all the time.. i love it. scares little children.

That's what I'm trying to get away from. That which scares little children usually attracts the attention of the cops. The Sundance is pretty low-key and I'm trying to keep it that way. It even still has the luggage rack on the trunk.:) The only thing that even remotely looks sporty on the car are the 16" pumpers. Crap, I think I've just talked myself into trying to find a decent flowing quiet muffler.

GLHNSLHT2
07-22-2006, 12:31 PM
it's the fact that the fuel isn't being totally cut when you drop the throttle. The S60 is really dumping fuel at idle and decel vac levels. Anyway it's normal for these cars. If you want to get rid of it you need to recalibrate the puter and turn the fuel off in decel.

86Shelby
07-22-2006, 02:21 PM
get a regular old straight through type muffler. Those race bullets are horrible about that.

Tony Hanna
07-22-2006, 10:39 PM
get a regular old straight through type muffler. Those race bullets are horrible about that.

What are you calling a regular old straight through type muffler? AFAIK, the race bullet is a straight through muffler. The construction is almost identical to a cherry bomb or other straight through type glasspack. The only difference is that the race bullet is shorter and stays 3" through the core. All the other ones I looked at necked down considerably inside the muffler. The 2.5" cherry bomb I had on the Daytona looked to be closer to 2.25" core size.

After going back over my goals for the car, I'm thinking more about switching to a chamber style or "turbo" muffler. Any suggestions on something that would be really quiet but still flow well?

For reference, I'd like to eventually turn the Sundance into something capable of running mid 12's in the 1/4 and still carry my butt back and forth to work every day and make the occasional trip to GA to visit the parents.
If I could do that and keep it looking and sounding like something that grandma would drive to church, that would be perfect.
Thanks,

86Shelby
07-22-2006, 11:19 PM
Ok, the bullet type mufflers I reffered to are pretty much race-only style mufflers, just enough muffling to pass as mufflers at the track. Supercrackerbox had one on his CSX-T, it was very loud and harsh sounding. Especially during decel in gear.

I believe I have a Magnaflow on my R/T, not quite straight through style, more of an angled -\_ type. It stays the same inner diameter all the way through. The main difference is that it has several times the sound deadening material around the core than bullet or glasspack style mufflers do. Typical bullet muffler in my experience has about 5/8-3/4" of material around the core, figure 1.5" or so larger outside diameter around the core. My muffler an oval style with a 3" core with 3" I/O. It's got a good exhaust note, reasonably quiet on the highway(resonates a bit though) and around town and doesn't let any of those decel backfires come through loudly at all. They are just little burbles in the note. Not brash, or harsh loud sounding exhaust. Check around with Magnaflow, they are usually a straight through design and come in 3" I/O, they should be the same diamter inside, but ask to verify.

Bullet style IMO:
http://www.dynomax.com/products/bullet-pic.jpg

Not bullet but straight through style:
http://www.magnaflow.com/02product/parts/12649.jpg

Tony Hanna
07-22-2006, 11:26 PM
Gotcha.:thumb:

Another alternate solution I've been considering is capping the 3" side exit with a removable cap (cutout) and then tying a stock over the axle pipe into the system with a stock style muffler in the stock location. The more I think about it, the more I think it might be a better bet. Then I can uncap it at the track, but have a basically stock sounding exhaust on the street.
Any thoughts?
Thanks!

86Shelby
07-22-2006, 11:36 PM
That's not a bad idea. A 2.5" cat back should fit pretty nicely and give you better power and quicker spoolup than the stock 1.X" pipe that goes over the axle. Or just use the over the axle portion of a 2.5" system with 3" and cutout for the rest.

Tony Hanna
07-22-2006, 11:52 PM
I wish I could afford that right now. Sadly, I'll probably have to resort to the
1.whatever crimp bent $20 crap from one of the discount parts stores. That is unless I could get an exhaust shop to bend me up an over-the-axle pipe in 2.5" for a reasonable price. This being out of work stuff stinks. The G/F keeps me fed, but I hate to ask for money to spend on the car. As soon as I get finished working on the house and back on the out of work list at the union hall, it won't take long to get the money to do this right. Until then, I'm operating on a very minimal budget.
Thanks,

puppet
07-23-2006, 01:03 AM
I like your idea Tony. 3" (nothin' in it) capped out the side "tee'd" into a *stock (*forget the 2.5" ... no need) out the back system with a nice muffler.

FWIW, I've got the big 6" round DynoMax muffler 3" out the side ... pretty quite but he still pops on deceleration. Your idea should kill it.

Tony Hanna
07-23-2006, 01:39 AM
Cool!
Another thing I like about this idea is that I've beat the crap out of the end of the 3" where it hangs so low coming out the side. If I go with the cap, I can cut it back and tuck it up tighter for better ground clearance. It wouldn't be hard at all to fab up a mating flange with a 3" turn down that I can bolt on in place of the cap when I'm at the track.
Thanks for all the help and ideas!

MoparN75
07-23-2006, 10:29 AM
Not sure what you mean by "popping", mine all gurgle {what ever that means;}}. especially my Lebaron, somewhat like you might hear from a mustang v-8 that has aftermarket exhaust...but at a differant pitch.I recently removed the cat and it was really loud after that. After removing the cat I found I needed more fuel so I turned the pressure up 5lbs...that seemed to reduce the gurgling. Mines to loud like this, I'm going to put a muffler on it.
I could be wrong about this but I suspect that a back fire would be the result of excessive unburnt fuel, "gurgling" as result of a leaning out during decelleration.

boost geek
07-23-2006, 02:58 PM
Gotcha.:thumb:

Another alternate solution I've been considering is capping the 3" side exit with a removable cap (cutout) and then tying a stock over the axle pipe into the system with a stock style muffler in the stock location. The more I think about it, the more I think it might be a better bet. Then I can uncap it at the track, but have a basically stock sounding exhaust on the street.
Any thoughts?
Thanks!
That's basically what I'm running on my Shelby Charger, except my 3" dump connects to a 2.5" crimp bent over the axle with a cheapy thrush turbo muffler. This really woke the car up, is still quiet, yet I can easily make it loud. I rarely have the cap off, because it sounds so much like a beater. Some guys like noise, I usually dont. My Greddy type S BOV is almost too loud for me, it is very loud inside the car. This exhaust has no cat, and also pops a bit on deceleration. I think my sds is hooped, was throwing a code 15 and running SUPER lean in T1 log, before I changed to T2. Would a newer sds work in the place of the stock one, and would it make the car run lean? I have a GLHS stage 2 computer, doesn't ping anymore, but usually runs only about 7 pounds boost, with a huge (12x24x4") intercooler. In T1 it would ping at no boost, but if you got mad and floored it, it would seem not to ping too much.

JuXsA
07-24-2006, 01:43 PM
I have been told its the valves since in decel it runs a little lean

iTurbo
07-24-2006, 10:43 PM
I think it will likely pop on decel no matter what if the exhaust is opened way up and there is no backpressure whatsoever.

Long ago, I made some recordings of my Shadow ES with various exhaust systems. It would pop loudly with an open downpipe and even with a 3" system all the way to the the rear bumper with no cat or muffler. Adding an Ultraflo muffler helped a lot with the decel pop.

www.turbosedan.com/jerm/ (scroll down to 'sound files'.

tryingbe
07-24-2006, 11:12 PM
Popping on deceleration is normal. Just ask any guy with an exhaust cut-out.

Tony Hanna
07-26-2006, 01:05 AM
I think it will likely pop on decel no matter what if the exhaust is opened way up and there is no backpressure whatsoever.

Long ago, I made some recordings of my Shadow ES with various exhaust systems. It would pop loudly with an open downpipe and even with a 3" system all the way to the the rear bumper with no cat or muffler. Adding an Ultraflo muffler helped a lot with the decel pop.

www.turbosedan.com/jerm/ (scroll down to 'sound files'.

I have to think building a decel fuel cut into the cal would put a stop to it. At least until the rpms dropped enough for the computer to turn the fuel back on in preparation for idle. I'm sold on the idea of a quieter muffler and a cutout for the track now though. I just wish I'd gone that route in the first place.

GLHNSLHT2
07-29-2006, 03:28 AM
heheh, it's just the fuel in the cal. For $130 you can have your SMEC converted to flashable (if you're not good at that type of stuff) and run Dcal on a laptop and cut the fuel yourself. Then you can run straight pipe and have it not pop. I run 3" straight pipe from the ported 2.5" Swingvalve back and it's quiet unless you're on the boost on the freeway onramp :)

Tony Hanna
07-29-2006, 03:37 AM
That sounds like a nice setup. I just don't trust myself to fool with my own cal though. I'll probably go with a custom cal eventually, but I'm going to wait until I get everything else finished first. The way I see it, there's no sense in shelling out the money, and then having to have it redone a month later to accomodate a lager turbo, head work, or whatever.

WVRampage
07-30-2006, 01:21 AM
Im using a Warlok 3" with the cut out and a 3"glasspack inplace of the cat and with the cap off of the Warlok its not to bad at all to drive and the turbo sounds great and not to much popping.

Tony Hanna
07-30-2006, 03:18 AM
That sounds like a nice setup.

WVRampage
07-30-2006, 04:30 PM
It doesnt sound to bad and its not to bad in the car to drive with the cut out plate off.

fleckster
07-30-2006, 06:01 PM
A loud harsh crackling where your car sounds like an old truck with glasspacks is sometimes caused by an exhaust leak at the header/manifold area or leak high up in the exhaust system when in vacuum (not under boost) when slowing down. The exhaust passing through sucks in cooler air through the leak be it a crack, warpage, or being loose and this makes for a serious cackling on decelleration. You might check for this as it would take the harshness of the sound away. It could be costing a bit of power too under boost.

TrrboJeep
07-31-2006, 03:12 PM
it's the fact that the fuel isn't being totally cut when you drop the throttle. The S60 is really dumping fuel at idle and decel vac levels. Anyway it's normal for these cars. If you want to get rid of it you need to recalibrate the puter and turn the fuel off in decel.
+1 :nod:

I've run mine richer to get the popping, and leaned it out to eliminate it. Different mufflers will "muffle" it in different ways, but if you want to eliminate it, you gotta cut the fuel back on decel. :nod:

Tony Hanna
07-31-2006, 07:59 PM
John, I think the exhaust is tight where the manifold meets the head and where the turbo meets the manifold. It may be leaking slightly around the donut though. I'll check that out.

Joel, I think just quieting it down considerably on the street would be enough for me. Right now the decel popping is plenty loud enough to attract unwanted attention. Hopefully I can get it to a reasonable level with a slight rework of the exhaust system.

Thanks,