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Discussion Starter · #1 ·
Anyone run turndowns as opposed all the way out? I'm doing new exhaust, and don't like seeing the tips protrude. I've had turndowns right under the back seat before and didn't bother me. I was thinking maybe over the axle, then dump toward the ground under the gas tank.

Sanderson shorty headers, 3" mandrel bent extensions, then eventually tapering to 2 1/2 before the mufllers.

Any pics too if you have turndowns? Noise level?
 

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Definatly run them as far back as you can as exhuast gases sometimes get caught under the car and enter the car.

As far as noise, the shorter the better.

LOL
 

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Discussion Starter · #3 ·
I've never bought into the fumes entering the car theory. For example, what about the countless hatchbacks, and SUV's where the whole vehicle is passenger area. What about jeeps that have side doors and windows. I don't see anyone dying from fumes in those applications. Last, suppose 2 cars are at a stop sign. One of them with full pipes, and one with dumps. Depending on the air movement, the one with full pipes could have more fumes collecting under the car as a function of air direction.

If the car is tuned properly, it shouldn't be causing excessive fumes IMO.
 

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Mine is turned down right after the mufflers and I dont have fume problems. Even when my trunk pan was rotted with a foot long hole in it there were no fume problems. If I can get my phone to post a pic I will.
 

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my 76 F100, moderate performance 390 with longtube headers, 12inch glasspacks, 4ft of pipe and a turndown. Click picture for sound.




No smell issues, noise is fine cruising, mild drone but I don't mind it at all.
 

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Might want to check local ordinance for exhaust. I had a cop once tell me my exhaust wasn't legal because on a four seater exhaust has to extend passed the rear tires for safety. Mine are at the rear axle on my 66 XL 500. Gonna run straight to the back. I like that look. The noise in the car is pretty loud too.
 

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Yeah Jozy, I make it a point not to "get on it" in town. I don't find the noise objectionable, I also lived on boats running 149 series Detroit diesels and V 16 Emd's for long enough I think many things aren't that loud to me, but are to others.
 

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The cop told me that 28 years ago when I was a dumb kid. I haven't had a ticket in 22 years. Knock on my imitation dash wood. The sound inside doesn't bother me much but causes some vibrations in the old beast that can be annoying.
 

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I've never bought into the fumes entering the car theory. For example, what about the countless hatchbacks, and SUV's where the whole vehicle is passenger area. What about jeeps that have side doors and windows. I don't see anyone dying from fumes in those applications. Last, suppose 2 cars are at a stop sign. One of them with full pipes, and one with dumps. Depending on the air movement, the one with full pipes could have more fumes collecting under the car as a function of air direction.

If the car is tuned properly, it shouldn't be causing excessive fumes IMO.

IMO dumping CO under the passenger cabin is risky business. I bet the inspector in your state will agree with me.
 

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I'd say it depends on how the air flows around your particular vehicle, but I would never recommend turn-downs under the car. I have exhaust under my work truck right now. It is exhausting underneath, and anyone who drives it for more than 1/2 hour around town gets a big headache that lasts for hours, but the headache doesn't start right away. It is tuned well and does not stink - just gives you a thumping headache. I don't dare take it on the highway for any distance until I get it out from underneath.

And, yes, we had a family friend die from exhaust CO. Not in a car, but in a small airplane from a small exhaust leak only 1 foot from the tip. The coroner tested him positive for CO and blood oxygen deprivation. The FAA report said a tower operator asked if he was OK because his speech sounded slurred, and he responded he was fine. He didn't even realize he was less than 10 minutes from passing-out, so I am a bit sensitive about the issue. It is a silent killer because you can't tell that it is affecting you. My 2 cents.

David
 

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X2 on several hours. CO is gobbled up by red blood cells. They love the stuff and won't give it up for hours. So even it you take in just a little per breath it will accumulate without reduction. The good news is death by CO is quite painless.
 

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The noise in my wagon is minimal , I am in the process of piping in my bellfower tips soon tho . In the uk all exhausts he a to exit to the outside of the vehicle so mine are illegal and should not pass the inspection on fri but they will ;)
 

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My turndowns are just in front of my axle housing close to the 3rd member pointed in slightly. I have 3" exhaust with chambered mufflers and 27" glass packs, love the sound. Haven't noticed any fumes yet. Was at a car show in a nice park last year and parked in the grass off of a limestone road. When I was leaving I noticed I was sturring up a lot of dust as I accelerated to leave. Was catching some dirty looks on my way out :frown:
 

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Discussion Starter · #17 ·
I'd say it depends on how the air flows around your particular vehicle, but I would never recommend turn-downs under the car. I don't dare take it on the highway for any distance until I get it out from underneath.

David
That's terrible you have a friend that died from it, spooky stuff for sure. I'm still not understanding how turndowns are the culprit though. An exhaust leak in the system, or poor weathersrtipping etc makes much more sense to me. Like I pondered before, why don't the hatchbacks/jeeps have a problem? As for highway use I would think you would feel safer at those speeds on account of air movement.

In my case, the plan was to run the mufflers out past the back of the interior, with the tips pointed at about 45 degrees toward the rear, and slightly outward. I would imagine the velocity of the exhaust even at idle would clear the body.

What do you think about that setup? Not a true dumped exhaust right under the floor, but also no tips visible under the bumper. Thanks for the input.
 

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... I'm still not understanding how turndowns are the culprit though. An exhaust leak in the system, or poor weathersrtipping etc makes much more sense to me. Like I pondered before, why don't the hatchbacks/jeeps have a problem? As for highway use I would think you would feel safer at those speeds on account of air movement.
I'm not saying you do or will have an issue, but under-car exhaust outlets are effectively the same as an under-car exhaust leak. I am only basing my input on my experience. An example is when I did an EFI conversion and the new lean-burn settings at 70 mph highway cruise began to burn-out the old carbon-packed guts of the catalytic converter. I didn't notice it until my daughter in the back said it was getting smoky. Sure as hell, I see the haze and look in the rear-view and I'm blowing a cloud of brown smoke from the exhaust and it's getting in somewhere even though I had the front windows down. I never found where it was getting in, but the tailpipe was short and it was partly blowing into the inside of the rear quarter panel and ran all-around underneath from there.

What was odd, is that I tried testing it again on the road by just jacking the system rich. No stink. I put the driver's window down and BAM... instant stink. Beats me, but I moved the tailpipe location and it stopped. I don't pretend to know how the airflow is around your car, but I have heard the factory places the tips where they do by experimentation to minimize exhaust intrusion. In any case, under the car is less likely to freely pass exhaust away from the car from underneath than at the edge of the body, as many cars have forward airflow under and behind the car. I would assume this is why most regulations require it. Again, I'm not an expert on this, but I have a very healthy respect for Mr. Monoxide.

BTW - rich mixtures make more CO, so lean cruise is not as dangerous. However, endurance racers often use CO filters for their helmet air supply to avoid CO poisoning while racing in and around cars that are definitely not running lean. ;)

I have an idea to test for it though - fuel fragrance additive. You can buy race fuel additives that make your exhaust smell like grape or cherry or other 'flavors'. Add some to a low tank and drive around at different speeds and window configurations. Smell it? You have a problem. No smell? Then you're probably good. Cheap $5 CO detectors are also available that you can put in your car just to test for a month or two, and can also be found at your local small airport. No matter what exhaust you use, I would just want to know if there was any danger before it was too late. And, I don't like headaches.

David
 

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Discussion Starter · #20 ·
I have a very healthy respect for Mr. Monoxide.

BTW - rich mixtures make more CO, so lean cruise is not as dangerous. Cheap $5 CO detectors are also available that you can put in your car just to test for a month or two, and can also be found at your local small airport.
David
Good points. Run rich, more CO2, run lean, more NOX. No free ride I guess, Lol. I thought about one of those stick on testers. I think I'll go with the dumps, and the tester, and see how it goes. Worst case scenario is I get headaches, or the tester shows accumulative results, and I drop the pipes and run them longer.

I've had turndowns in several cars, daily drivers, for decades with no problems. That doesn't mean there's no potential for long term harm though, especially with kids riding in the back. Maybe I'll do 2 testers, one in the passenger area, and one in the trunk. If there are variances in the readings, I'll know where to start looking for weatherstripping issues, holes, etc.

Thanks guys!
 
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