CO in cabin - webers and sporto muffler - measurements made.

[jwetering]

Kind of a long story...but not uninteresting. It involves my 3.0 litre, 40 IDA webers, GE60(ish) cams, sporto exhaust, pre-74 heat exchanger motor and the 1978 sunroof coupe with back dated heater it lives in. I always drive with the sunroof open, even in a light rain sometimes.

A month ago I pulled my car out of winter storage and started to drive/tune it. Some good days some bad. Lot's of fiddling with the carbs, mostly leaning out the idle. Damned if it didn't make my clothes stink every time I drove it though, and damned if I wasn't feeling kind of woozy sometimes. I borrowed a gas analyser from work, the kind we use to check atmospheres in confined spaces and on my drive home I did some baseline measurements.

40 ppm CO pretty much right away. We kick people out of confined spaces at 25 ppm so I shut down the heater and immediately diagnose rusted exhaut pipes leaking into my heat exchangers. Oh well, I've been meaning to buy SSI's for a while now, so I bite the bullet.

Fast forward a week or two and the SSI are installed. Car is idling kind rough, but acceptable. Go for a drive and geez it's better - kind of, but now my eyes are stinging - WAY to rich I think, but I've been leaning the car out bit by bit for weeks now so what gives. I make a run with the gas analyser and measure a peak of about25 ppm - better, but still not great.

Time to get serious about setting the carbs up. Get my balancing air flow meter and get that bit sorted - no problem. Turn each of the mixture screws out two turns in preparation for the slow and methodical leaning out ritual and whoa! the car is idling strong and even. Guess I was WAY to lean all that time. I make a run with the gas analyser, and get a peak of about 15 pm CO. Strange but true, richer mix makes for a less smelly cabin - my eyes didn't even water any more.

So tonight I go out and do a semi-controlled experiment (I'm a chemist by trade). I take readings with the heater on full/half, sunroof open/closed, windows open/closed, low rpm/high rpm, sane speed/insane speed

Here's the basics:

- The worst readings were at high speed (100 mph) 5000 rpm, sunroof open, heater on full. This was making 16 ppm or maybe worse - I was kinda watching the road so I can't say where it peaked exactly.

- At higher speeds, closing the sunroof dropped the readings significantly and opening the drivers window got the readings well below 10 ppm even at higher engine speeds ( I wasn't pulling a ton anymore, but still going pretty good)

- Closing the sunroof and opening the window at normal highway speeds got the readings down to 2 ppm with the heater on full. That's fine.

- A typical drive for me is sunroof open, window cracked, city street speeds, heater on half, 2 or 3000 rpm. This made 4 or 5 ppm. I've yet to decide if this is acceptable.

Well, at least I know how I can keep from gassing myself - close the sunroof. The next step is cleaning up the cabin air completely. Here's my plan:

1) Try a muffler where the outlet(s) point to the corner(s) of the car. I cut about two inches off the ends of my Sporto muffler because I was banging my shins on the pipes. I suspect the short pipes exhaust right into a negative pressure vortex area behind the car and the fumes are drawn into the engine compartment. Notice that all mufflers except the Sporto has pipes pointing to the corners?

2) Investigate how badly my oil tank vent is gassing the engine compartment. The oil tank used to vent into the intake manifold on my old CIS system. Now with the carbs it vents into the engine compartment. I've seen some trick looking oil tank vent seperators on this site, but it looks to me like the gasses still end up in the engine compartment. hhmm.

I guess I've got all summer to sort this out. I don't really run the heater in the summer much. Any thoughts guys?

[jwetering]

Oh yeah - I know how everyone like pictures

[gerard vaglio]

This is interesting, I always assumed that heat exchangers with no rust meant there were no fumes in the cabin?

Maybe that good feeling I get from driving my car is just carbon monixide.

[RoninLB]

I figured that if I have to vent the case&tank 'cause of fumes I would run a 1.25" hose down under into the air stream. I'd slice the hose tip at 45deg with the open slice facing rearward.

meanwhile I run open roof and open rear 1/4 all yr and no prob.

Did you get headaches w/high CO ?

[galwaytt]

well, on my 87 a while ago, I too noticed - a haze - I thought in the cabin, and a whiff of something........I had the kids in the car too, so wasn't happy with the thought of all that CO around, sooooo.......I got depressed.

Another thing to fix, I thought.......beginning to get 911-cheesed.......

So, I open up the engine lid, and da-na !!, there's the oil filler cap sitting on the right rear engine mount...........I'd forgotten to re-fit it

So, refit, all gas gone..........which is kinda where you're at now.........you need to vent - to a tank, to a valve, to outside the car.........but you need to get rid of it.

Very curious, I thought, imagining a whole host of heat exchanger/oil leak issues.

It did leak though................but that was much later, and a whole other story...........

[Wil Ferch]

Nice looking ride....

I deal with confined space entry/occupancy issues at work too....and CO is nasty business.....

A human's physiology causes CO to be "preferentially" absorbed into the body instead of O2...when given a chance...and it doesn't take high dosages before it becomes lethal....

Hint to everyone....if you get a chance...run a portable CO detection unit in the passenger seat of your car...and take measures to bring the CO values down in your car....hate to lose any *one* of my Pelican buddies...

....would make for a bad-hair day...

- Wil

[jwetering]

Originally posted by galwaytt

So, I open up the engine lid, and da-na !!, there's the oil filler cap sitting on the right rear engine mount...........I'd forgotten to re-fit it

So, refit, all gas gone..........which is kinda where you're at now.........you need to vent - to a tank, to a valve, to outside the car.........but you need to get rid of it.

Oh yeah..that's interesting.

One vent line to the outside coming up for ol' jasp! I was looking at routes for the vent line last night. Nothing obvious - guess I'm going to have to do some cutting.

[Wil Ferch]

Here's a link we should be familiar with. Look especially on para 5 on exposure limits and consequences...

http://www.cpsc.gov/cpscpub/pubs/466.html

Wil

[73911guy]

I found that routing the oil tank vent into the watershield covers on the Webers (instead of just using the K&N filter in the engine compartment) got rid of almost all of the smell inside the car when using the heater.

Also, I've noticed a difference since I changed from a factory style muffler (where the exhaust outlet runs out from the muffler at an angle) to a Dansk Sport Muffler (where the exhaust outlet runs straight back). After a long highway run, I now have to clean off the left rear bumper and the rear edge of the duck tail. Seems the factory knew best, that routing the exhaust out into the air stream running along the side of the car worked better than running it straight back - your sport muffler and the CO issues seem to support that.

BTW, there was a PCA member in Central Indiana that said he had to extend the tips on a sport muffler to somewhere around 14 inches to keep his rear bumper clean during highway driving.

Jim