Hello guys.
Since ive decated my r53 i noticed an exhaust smell inside the cabin and it got worst and worst on long drives. Feeling tired and Sleepy.
So i went and bought a Carbon Monoxide meter. Sure enough the numbers are spiking. But here’s the problem.

It only spikes up when i have the circulating AC button activated. If i turn of off. There’s no exhaust leak inside st all. Zero on the ppm meter.

Do i i have an exhaust leak? Or since it’s a hatchback the draft coming in from the trunk bring the exhaust gasses in?

Any help or inputs are greatly appreciated. Thank You.

Ps. I’m running headers with no cat to Borla exhaust.

 

You're smelling what the unfortunate person behind you in traffic gets to smell since you took the cat off. No sympathy from me. Anyway, you have an exhaust leak. For your own health, fix it. For the health of everyone else and the planet, put the cat back on.

 

My sentiment too for road cars, and I would go one step further. I would like to see track cars imposed with emission control too. Count we are lucky while we have not been legislated off the roads yet but that day is coming up fast. Sitting in grid at the track next to a catless V8 can shorten my life on track greatly.

 

I guess if you want it fast and no emission go with a Tesla.

Well the good good news is i found the leak. It’s where the catback starts. Broken gasket. Also where the clamps are are leaking. The muffler shop warned me about this.

Theres gotta be a way to seal those without welding.

 

The purpose of test pipes / cat-less exhausts on race cars is due to the level of heat contained within a catalytic converter. A proper race car participating in an event would very likely fail due to the constant use and heat the catalytic converter(s) would retain.

On a road car it's ignorant to run without catalytic converters.

 

I am not going to get into the political aspects of this thread, but the rear hatch is adjustable. The two rubber bump stops on the hatch can be turned out or in, to get the gate to seal and not rattle, which is a happy medium. if the gasket is torn (that surrounds the hatch) replacement is required.

 

No. It is not a political subject. It is a civic responsibility and the laws.

The air all the living things that breath is far from political. Willful ignorant has no excuse. Let me just point out a few things pertaining to emission and society's attitude change. Social attitudes change at glacial pace for the ignorant. But for those with keen sense of environmental awareness the pace is faster than you like.

• All the world's most highly regarded professional road racing have race cars that have catalytic converters. You cannot design a high performance catalytic converter is an ignorant myth. Everything in design and engineering is about compromises. Given enough priority just about anything is possible.
• Porsche factory prep'ed race cars like their GTx Clubsports you can buy come with catalytic converters. If I have not mistaken the WRC cars also are equipped with cat (if you can't spell the full word like me) and same goes with all international high profile races.
• More and more your local municipal race tracks are under pressures to change or cease to exist, and Portland Internation Raceway is no different. It is not just exhaust emission. The first to hit is noise emission (that's right, noise is an emission and most annoying). In many tracks in CA, the fine is stiff and it should be. Your act and choice to have fun impact the residents around the event site and most don't share your enthusiasm.
• In many European cities they outright ban certain vehicles (usually older ones and some diesels) from driving into the green zone. Sooner or later this will be common place including the North America.
• Willful tempering of emission equipment is a federal offense. Sure, you can gain some cheap HP but most has no driving skills to take advantage of it. Just because of ICE is not a zero emission power plant does not free you from willful pollution. Why do you think they clamped down so hard on the diesel gate? Automotive executives go to jail for these crimes and it is high time.
• If you have young child can you explain to him/her why is it OK for daddy to willfully defeating the most important air emission abatement device on a street car?

 

This thread turned into a weird direction. OP asks about exhaust leak, thread turns into preaching about emission controls.

I hope the preachers also change their oil no sooner than six months, use only distilled water and water wetter instead of coolant, only use their AC with the windows up, keep their tires inflated properly, etc, etc

 

OP asked about the exhaust because he happened to notice how vile is the de-cat'ed exhaust because of the small leak make it back into the cabin, or else he would have lived in ignorance is bliss. BTW, he should weld those pesty joints shut so only the poor soul behind him need to suffer. You are doing well as an Angry 15-poster on NAM.

And yes, I am not a compulsive obsessive oil change neurotic and I don't always use distilled water or wetter than water wetter for coolant. Seems you can use some coolant to calm your trouble soul.

You are so insightful too, on my tire obsession. I happened to invested in a tire pyrometer because of my obsessive compulsive about the rubber that meets the road. BTW, whatever happened to your wt/hp or hp/wt list in your signature? I had the impression that you are seasoned SCCA racer because of it.

 

Hmmm.......WRC cars run cats. As do a lot of other series.

 

Well, just an update, went to the muffler shop today, they said they fixed the leak, changed the gaskets and gobs of RTV, coming home had the AC circulating again and still seeing my ppm meter going up, not as fast as before.. hence my shifter box cover is slit due to the short shifter.

but still , how can exhaust gasses still making it inside the cabin?

is the draft from the hatchback bringing the exhaust fumes back in? I wonder why kids always falls asleep in cars ( just a thought ).

 

My guess is the rear hatch is causing a vacuum and sucking in the Co2/Cm. It is also possible the door glass can be doing the same thing, when they are up.

 

Really? Interesting, I was unaware (obviously, by my previous statement). I support that, of course, but have always read that cats retain too much heat and would fail in short order in a consistent hard-use scenario.

 

Door glass? I don’t think the gasses will it that far bough and i already adjusted all the wind noises on both doors. It’s sealed tight. Was having wind noice at 80mph. Now nothing pass 3 digits on the highway.

I also added extra foam seal in the back on the lower part of the boot.

Question. I see some vent holes in the trunk. Some old foam material falling off. Where does that lead to? Battery area?

 

They usually run a high flow cat with materials different from typical street cars that can handle the higher temps. But, proper race cars have a much shorter replacement schedule, ie. WRC cars replace turbos after every race due to the anti-lag system.

 

WRC cars also use a rear-mounted cat.
1. It reduces the heat load on the cat
2. If it fails, it just blows out the back instead of taking out other components (e.g. mufflers)
3. It removes the fire risk from UNDER the passengers
4. It must be inspected after each stage - putting them at the back means quick/easy swapping

These are remarkably cheap for what they are:
https://shop.namelessperformance.com...-tip-w-v-band/

 

I am very surprised as to how cheap these are. I said I thought WRC cars have cat because I spotted these at the tail pipe in racing videos and they were glowing orange.

 

There are outside exhaust vents for the air conditioning system. Pulls in through the cowl, pushed out through the trunk.

You'll want to patch that foam with screen door material or something - I had mice get in through those vents.

 

So that’s where it goes out when i have the circulating button off. Then i don’t get any carbon monoxide in the car. But when i have it on. That’s when it comes in.

Still trying to figure out where the gasses are coming in from 🤷🏻*♂️

 

Here's a quick test, put duct tape over those sill vents and see if it still comes in on recirc. Might at least eliminate the vents as a cause.

 

GOOD CALL ! thanks

 

Taped it and problem still there

went to muffler place to redo all my flanges. They did silicone rtv seal on all of them. No leaks underneath.

Also did soap test on my headers and no leaks there

mind boggled right now

 

Did you ever solve this? Same issue in mine. Going to replace the outer trunk seal first.

 

nope still getting it. I invested on a carbon monoxide meter and it still goes in when i have the circulate button on.

And i have no leaks underneath. I think it’s just being a hatchback and having no CAT. 🤷🏻‍♂️