Cabin pressure

[350Matt]

Hello Chaps

I'm trying a few things to get my 92 4.3 less noisy on motorway trips, don't worry its only wind noise I'm trying to reduce.

One thing I'm trying to sort at the minute is some sort of cabin vent that reduces the positive pressure you get at speed which bows the windows out and away from the seals.

Now the 500's have a pair of grills into the boot which I've sort of replicated by fitting some rear speakers and spacing them away a little to allow air to flow around and behind them.

I then drilled a hole through the corner of the boot floor and glued a pipe in to try and tap the supposed low pressure under the car which would draw the air out from the cabin.

This doesn't work

What it does do is when you have a window slightly open is draws exhaust fumes into the cabin, despite being a foot or so back from the tailpipes....


I toying with the idea of making a venturi to create some local low pressure over the pipe intake but this is getting more involved than I would like

Where do the 500's vent the boot? Over the diff?

Any ideas welcomed
Matt

[Ballistic Banana]

The boots vented by three rather large holes in the bottom of the boot.
If you can see down the back of the petrol tank ( cabin side ) you may be able to see them,otherwise from underneath they are rear of the rear wheels. I'm sure i have a pic of them somewhere hold on i'll have a search.

Ok its on my other pc will look it and post next week

BB

Edited by Ballistic Banana on Monday 31st December 00:13

[spend]

Yes Matt, there are some big holes in the gfibre just behind the diff (forward facing). Whether a splitter &/or spoiler is required to make them effective I have my suspicions.

I think an earlier thread came to the conclusion that the aerodynamics bowed the windows and hood so that unless you radically changed the bodywork there is little you can do about it. Careful alignment & tiptop seals seems to be the best way forward to reduce any gaps that open up at speed (buffeting noise). I fitted Corrado mirrors and they seem to be quieter - but that nay be placebo??

I regularly have a smoke, just to see where the air is the flowing

Dave

[Hoover.]

I don't have any problems with "cabin pressure" in my 4.3.

Are the 2 holes un blocked where the roof meets the body at the rear..... mine had paper wedged in them when I got the car.

[trackcar]

there's a marked low pressure area at the side windows .. that's why lowering them a little improves the through-put of the heater and is drawing your exhaust fumes back in the cabin Matt.

Spacing your speakers out is also reducing their bass output, the low frequencies are not very directional so you'll get interference from behind the cone reducing the bass output, so put those flush with the bulkhead again to restore the infinate baffle effect.

You might get some gains for your windnoise by playing with small spoilers off the side of the A pillars? also being absolutely anal about the fit o the doors and side windows will help .. it's amazing what a bit of extra rubber padding here and there can do.

[Uncle Fester]

An earlier thread found that the exhaust was getting in by being sucked past a defective boot seal.

IIRC the low pressure around the windows was pulling air throught the 'speaker vents' from the boot. This was dragging the exhaust gas past the iffy boot seal instead of the vents by the diff.

Edited by Uncle Fester on Tuesday 1st January 17:48