Exhaust System Question

[MStiller]

I was put in charge of designing the exhaust system for a vehicle my company is building, and I was reviewing the Code of Federal Regulations as it pertains to vehicles, and under the section for exhaust systems it says:

"No part of the exhaust system shall leak or discharge at a point forward of or directly below the driver/sleeper compartment."

which seems to fairly definitively say that you cant have an exhaust tip in front of the driver. So, my question is, how is the Mercedes SLR road legal, because the exhaust comes out right behind the front wheels. Does Mercedes have an exemption for the system, or am I interpreting the regulation incorrectly? Any help is greatly appreciated.

Thanks

 

[JonKBmw]

I think you're misinterpreting the rule slightly. It says that you cannot have any exhaust emitting device under the driver/sleeper cabin. However, you can probably have an exhaust that exits the vehicle before the driver, but not under. Reason being, any exhaust that dumps "under" the car, is a potential carbon monoxide hazard. As long as you get the exhaust exit out from under the car I'd imagine you'd be fine.

 

[MStiller]

Turns out that the standard I was told about doesnt apply to cars, only to motor carriers (i.e. tour buses, etc.), so nevermind!

Thanks for the assistance though

 

[patprimmer]

In Australia, no exhaust can exit in front of the rear of the rearmost opening window. This is to prevent exhaust gas entering the cabin. Even this is not foolproof as wagons with open tail gates can suck exhaust in from behind the car.

The concept of exiting exhaust in front of an opening window sounds positively dangerous to me.

Regards

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[MStiller]

Pat-

I would agree theoretically agree with you, but the issue is a low pressure question. Behind a moving vehicle, you get a low pressure zone which sucks the exhaust up behind the car, so if the rear window is open, it goes right in the vehicle. But at the sides of the vehicle, the air moving past is enough to blow the exhaust away. There have been plenty of side-pipe cars that work fine, the issue was whether or not in the US if you could have the pipes exit ahead of the passenger compartment, a-la Mercedes SLR, or if it had to be behind the passenger compartment, a-la Dodge Viper/Old Vettes

 

[GregLocock]

Great, so long as you are moving.

Otherwise Pat's objection is entirely sensible.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Lou Scannon]

Of course if the vehicle has modern day emission control the hazard is greatly reduced - not eliminated!!

 

[Casey911]

Ford had a exhaust that was right in front of the rear wheel on the F150 in 1999(probably to save money on the length of exhaust system) The ended up having to redsign the system to behind the wheel because the exhaust gases were corroding the aluminum rims. (funky green corrosion)