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Exhaust Fumes ??

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TonyR

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We have a 100 and wonder why we have a smell of exhaust fumes whilst driving with the top down?

There is no sign at all of fumes coming from under the bonnet.
It seems that the air flow around the car encourages the fumes to attack us from behind.

Should I shorten the exhaust pipe or take off the upper angled extension?

Anyone suffer from this?
 
Take off the upper angled exhaust extension-----Keoke
 
I haven't experienced this, but have heard of the problem when the exhaust pipe is too short. All the exhaust systems I've used had tips that bent slightly upward--for ground clearance I suspect (or maybe looks)--and none had a problem. All extended an inch or two beyond the rear bumpers.

Have heard said it's important that the tips be cut so that they are perpendicular to the ground; i.e. not squared-off. I've also always bought or built systems this way.
 
Bob_Spidell said:
I haven't experienced this, but have heard of the problem when the exhaust pipe is too short. All the exhaust systems I've used had tips that bent slightly upward--for ground clearance I suspect (or maybe looks)--and none had a problem. All extended an inch or two beyond the rear bumpers.

Have heard said it's important that the tips be cut so that they are perpendicular to the ground; i.e. not squared-off. I've also always bought or built systems this way.
Click to expand...
I read once where the Healey exhaust must be angled up the way it is and the pipe cut as you have suggested. Something to do with horsepower or whatever, but important.
Adding and extension is the best way to take care of the fumes. I did an extension and never had a problem.
Patrick
 
You know that I'm not an aeronautical engineer, but I have a Classic Mustang buddy who works for Boeing in Bellingham, Washington who is and in discussing the airflow over, around, and under a Healey with him, he pointed out several things.

The rear of nearly all cars have a very thin layer of air, called the boundry layer, that flows UP and forward under the main rush of air flowing down and rearward over the trunk lid. In the Healey, this may be exagerrated because of the rounded back end and long sloping trunk.

At speed, because of the air flowing up over the bonnet, then up over and around the ends of the windshield, the entire cockpit is a low pressure area.

Depending on the vehicle speed, wind direction and speed, it is possible that low pressure of the cockpit area is pulling the boundry layer all the way up the trunk lid and into the cockpit.

One reason that many modern cars have have a small "lip" spoiler on the trunk lid is to help merge the air flow over the car into the merged airflow at the rear of the car and prevent the boundry layer from advancing farther forward.


100046.jpg


If your exhaust pipe is angled upward and/or too short, you might be introducing exhaust fumes into the boundry layer which then get sucked up to the cockpit.

Many performance cars (Porsche, Crossfire) have a small, servo driven spoiler, that raises at speed to disrupt and stop the boundry layer.

I'd lower the angle and/or lengthen pipe so that the tip protrudes more into the airflow from over and under the car and farther from the area that feeds the boundry layer.

Please let us know what you do and what happens.

Tim
 
Do not have the problem with my 100, but had the issue with a V-12 E-Type I had in the 80's. We tried all sorts of stuff and could never get it right..


Pete
 
Had the issue with a V-12 E-Type I had in the 80's. We tried all sorts of stuff and could never get it right..



Well for a haed top. if you had put a wing on the roof of the car forcing air down the back of the car much like old station wagons and suburbans. You would have solved the problem.---Keoke-- :wink:

OH!! this problem exists in aiecraft and boats too it is referred to as the "Station Wagon Effect".
 
tiga2 said:
Cottontop is right on! Bring it out the side where it "should be" !
Click to expand...

OH !! Sure that's why they all come out the back.--Keoke-- :rolleyes:
 
:iagree:

That just might do it.---Fwiw--Keoke- :frown:
 
tiga2 said:
You know, British engineers have been known to get it wrong at times! ;-)
Click to expand...


Yep!!!---Keoke-- :lol:
 
Well I believe I have somewhat cured the problem, that is I only appear to smell fumes a little on the overrun.

I cut off the angled up piece of the tailpipe and affixed a pipe that is straight with a slight bend on the end that exits the fumes slightly to the left.

It is a lot more pleasant to drive now. The weather over here in the UK has been excellent for the time of year...have been in the car every day for the last six days.

I would like to see a picture of a 100 that doesn't suffer from a fumes issue though!

Thanks,

Tony
 
TonyR said:
I would like to see a picture of a 100 that doesn't suffer from a fumes issue though!
Click to expand...

Good job on getting your pipe out of the side-to-side boundry
layer feed zone up at the level of the license plate light.

Here is a pic of my Ford V8 powered 100-6.

Image41.jpg


I've never smelled exhaust fumes.

Tim
 
Next time you get caught in the rain with the top down, notice how much water gets on the inside of the windshield.

If there was ever a car that needed pass-through wipers...

That thing about driving faster in the rain to stay dry, wasn't written by a Healey owner!
 
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