Lotus factory Sunroof question

[Roger 912]

My 1984 Esprit Turbo has the factory fitted sunroof, but I find that when I am driving with it open, i get exhaust fumes in the cabin.

The problem is really bad at high speed. I am just wondering, is it just my car, or is this normal on Esprits fitted with this sunroof?

I have not tried with the glass removed, but that will be my next option.

I know that the angled glass causes a vacuum at the aperture, but I would have thought that the exhaust pipe was far enough away for the fumes not to be sucked in to the sunroof.

Any thoughts on this?

[Andyww]

I remember many years ago when the sunroof model was launched I went for a test drive at Bell and Colvills of their demonstrator. The salesman explained "There might be some noise and exhaust fumes because the air deflector flap fell off and we lost it"  

So is that the answer, do you have the deflector flap?

[Roger 912]

Andy. Yes, I have the deflector but that is only used when the glass sun roof has been removed. It fits on the leading edge and is meant to reduce cabin wind buffeting.

My problem is with the glass top opened. You should be able to see this on the attached picture.  At slow speed there is no problem but at any decent rate of speed the fumes are annoying.

[andydclements]

I've not noticed exhaust fumes, I'd suspect you have a route for fumes from the engine bay into the cabin, and the cabin de-pressurises with the the roof open. I used to have a similar issue with fuel fumes until I sorted the tanks. 

[Roger 912]

It is certainly exhaust fumes. The tanks are in fine fettle and all the vent pipes and fuel lines have been changed. There are no smells in the car at all until the roof is opened up and as I say, it is only at high speed. The exhaust system has no leaks whatever

I am trying to work out the vortexes with the rear spoiler, the louvres and the small spoiler on the roof and then the huge vacuum that would be created by the opened roof. The vacuum that this should create should be taking all the air out of the cabin rather than sucking exhaust fumes in.

This week, I shall remove the glass and run with the small air deflector in place and see how that copes.

Thanks for all the input.

[andydclements]

The low cabin pressure allows external pressure to push fumes in from the engine bay

[ramjet]

I have a deflector as well, but hardly use it as I can't leave the car alone then. I have never had exhaust fumes enter my car with the roof open. Low or high speed. (S4)

Do you have the side windows up or down?

I'm tending to agree with Andy.

[Roger 912]

What I have found is that for the last 9 years of owning this car, I have not had an engine cover, just the tailgate with the louvres.  As I was going to take the car on a long round trip and I was worried about rain filling up the plug holes, so I made a beautiful engine cover with a hole that mated with the shute on the tailgate. It is only since fitting this that the fumes have become more of a problem..

Now I have a theory. The rear spoiler causes a low pressure point at the rear of the car and this brings exhaust fumes from the tail pipe back into the engine bay. The louvres are doing their job and causing a low pressure point, sucking the fumes out of the engine bay, but the low pressure point caused by the opened sunroof is sucking these fumes into the cabin.

A little bit long winded if you will excuse the pun.

 

[ramjet]

Try it with the engine cover off again and see if that helps. Is your new engine cover the same design as original?

[Roger 912]

The engine cover is not an original one, but one that i made and it fits exactly as the original and also has the exit for hot air as the original. It is held in place by the foam around the shute on the underside of the tailgate.

[ramjet]

Odd. If it is new though, it has to be something you have changed. Work backwards.