Clever Options For Reducing Exhaust Smell with Catless Headers

[evonschu]

Hey all. Was wondering if anyone has any clever ideas for reducing the smell of exhaust from catless headers on our ZL1's. I've seen a number of people say they have had cats melt when running higher HP numbers, which I am. Maybe some don't, but don't really want to risk it. Also like the loudness and don't want to pay the extra cost to add cats in or have reduction in power.

The smell seems obviously is worst when any of the windows are down. Whats odd is that sometimes I can even smell it while driving. Having some sort of funneled air coming back up due to Bernoulli's principle or something? Having the vent on and windows up I usually can't smell it unless I'm idle.

When idling though with windows down the smell can be pretty annoying if the wind is right. I'm just wondering if anyone came up with any out of the box ideas to reduce this. I was thinking maybe some sort of fins that fit over the rear fascia where the exhaust pipes are to maybe funnel the smell out? Or even some way to reverse pressurize the cabin so air is always being pushed out of the windows when open? Maybe this could be accomplished by using a really good cabin filter and turning the vents on at medium to high speed? Or a fan near the exhaust blowing out? Also the placement of the exhaust pipes? When I got my headers installed I noticed it pushed my exhaust pipe out about 1-2". Could this be causing more of a smell?

If anyone has tried anything or has any tips for this other than "put the cats back on" I'd love to hear it.

Thanks.

[wrtowman]

Your best option is E85. No better smell.

[evonschu]

Ugg definitely don't want to to do that.

[DrkPhx]

^^ Why not? Besides smelling better, it burns cleaner, the car will run smoother and cooler and you pick up power.

- Check for exhaust leaks by the headers and mid pipes.
- You can tune some of the smell out; how much depends on the cam overlap.
- I fabbed up some resonators that bolt in place the of the catless pipes to help tone down the exhaust, I think they helped cut down on the smell a little.

[crazydave]

[QUOTE=DrkPhx;9401725]^^ Why not? Besides smelling better, it burns cleaner, the car will run smoother and cooler and you pick up power./QUOTE]

Other than the initial costs, there are not negatives other that gas mileage.

-No cats here on E67 and no smell at all....and i gained about 50 more HP.

[E. Bryant]

I'll be honest - the smell isn't noticeable in my car, except when I first start it up in the garage, or on rare occasions when the car is at rest and there is a slight tailwind. I'd first take a look to make sure that there aren't any exhaust leaks into the cabin. Leaks around the midpipes would be the first thing that I'd look for, and I'd also check the trunk seal to make sure that exhaust isn't coming in through the back of the car.

[d454brisson]

The old time racers used this when the exhaust was in the front of a rat rod etc car.

https://www.summitracing.com/parts/plu-19769-32

[evonschu]

Originally Posted by E. Bryant

I'll be honest - the smell isn't noticeable in my car, except when I first start it up in the garage, or on rare occasions when the car is at rest and there is a slight tailwind. I'd first take a look to make sure that there aren't any exhaust leaks into the cabin. Leaks around the midpipes would be the first thing that I'd look for, and I'd also check the trunk seal to make sure that exhaust isn't coming in through the back of the car.

I'd assume if it was this then I'd smell it with the Windows up then. I've had 2 different shops look at the exhaust (JDP and PSI) during upgrades and neither noted any leaks.

The weird thing is that after this post I haven't been smelling it as much. I think its just when like you said there's a tail wind or if I'm on an up hill incline that the fumes are pretty bad.

The smelly grape stuff looks good but too much $$$ for long term driving. Good to know that's there though.

Still curious as to if moving the exhaust tips back at all might help? For those that have exhaust done w/o cats how far do your pipes stick out past the rear fascia?