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I think there is a very slim change exhaust fumes would travel all the way up over the back deck and glass to enter the sunroof opening. They may be entering thru somewhere in the rear panel. Perhaps thru the light assemblies or from under the car and are being sucked forward due to the airflow over the open sunroof.

A friend of mine had a 1966 Mustang 2 + 2 that he put a sunroof in and it did the same thing after the installation. He also thought the fumes were being sucked over the top and in but after taping a few pieces of yard around the back of the car and driving it we could see there was no airflow coming forward.

After he replaced the tail light gaskets the fumes went away so we figured the airflow over the top created a slight vacuum inside and sucked air forward out of the trunk.

Hth
Brian
 

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boomerang opeler
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i would think it would pull fumes in through the rear lights or the point where the gas line exits the bottom of the car (right next to the exhaust)
if the lights have a good seal try a run of gaffer /duct tape round the pipe under the car and see if it helps
 

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Back to the metal hacking,

If anyone is considering losing the whole roof, the advice on stiffening the frame and adding a rollbar should be heeded. I've always liked this analogy of torsional rigidity:

Take a shoe box with the lid taped on, and try to twist it along its long axis. Then take the lid off and try it again. This is why it is a bad idea to make your own convertible using nothing more than a cut-off saw! :D

jtb
 

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Discussion Starter · #24 ·
Yarn flow test for back draft

OrangPeEL said:
exhaust fumes (slight) in cabin when moving ... Only happens when the top is OFF, and door glass is partially/fully down. ...I believe these fumes are entering over rear of sunroof opening... GT has a front air dam.
... I'm wondering if targa owners experience this? and/or could one of those euro-style spoilers (across top of back window) move low-pressure pocket rearward... or scrape that backdraft away from roof?
bq97 said:
...(friend) thought the fumes were being sucked over the top and in but after taping a few pieces of yard around the back of the car and driving it we could see there was no airflow coming forward...
Hey Brian(bq97)- Thanks for idea!... I've been looking forward to testing this all evening! Just got done... I tried taping on some yard as suggested, but I just mowed Sunday and grass is a bit too short to indicate flow well! :D ... but yarn worked great! 4 points close behind roof opening, & 4 points on rear window. With top off & windows up: middle yarns by roof hole hopped in and out; yarn on back glass fluctuates only slightly rearward (almost neutral, even at 50mph...no exhaust smell). When I begin to roll down door glass (2" or more), roof yarn hops right in, and window yarn swings forward (& exhaust smell appears :( )! Draft was much more positive than I expected to see.

Feels like top edge of hole GT is punching is about 8"(or more) above rear roofline, so I'm doubting a window spoiler would help. Moving my hand into air path affected glass yarns little/none. Maybe this front air dam clears too much air, & I need to allow more under car to dilute/shed these fumes?

-Dan

PS. Hey Adam(spdkilz02)- yep! All that stuff is out; roll bar is in... no rigidity problems... useful space gained. I've got a few interior pics up in the gallery.
 

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OrangePeel,

How far past the rear valance do your exhaust tips extend? Maybe increasing their length slightly will help.

Brian
 

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Pathologic Opeler
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exhaust leaks

besides the usual gaskets for the rear lenses AND Side marker leaks...
check the calisle 2005 thread, i have several photos of exhaust exits,it seems best if it sticks out a ways, flush to almost the bumperettes...mine is not out far enough, is my opinion

1-also look under the car for black spots around the welds of exhaust pipe...black spots are carbon from leaks

2- check holes where emblems poke thru...missing prongs in the emblems result in an unfilled hole in the tail

3-check hole where wires pass thru from the license plate bulbs

4- remove wooden tray for spare tire,shine a light from all points outside of car, get in trunk with lights out, you will find holes..some could be around the gas tank base
 

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Discussion Starter · #27 ·
The REAL reason my children easily fall asleep in the car

bq97 said:
OrangePeel,

How far past the rear valance do your exhaust tips extend? Maybe increasing their length slightly will help.

Brian
Tips extend 'bout half-way thru length(depth?) of rubber on bumperettes.

I've read lots of posts regarding cabin fume woes & entry points... thinking, "that's not me"... BUT... credit where due, opeldean & baz mentioned it again, so tonight I found I've lost a brake lens screw & that one of the drain boots is marginal. From the string-draft test, I doubt this'll cure me, but may help some... and I really appreciate not cracking/losing that lens! Thanks!

I string tested with the top ON tonight (Brian, I dunno why, but I love this test!) Rear glass strings appeared to have a little more rearward flow (still surprisingly neutral though)... unaffected by open door glass. So my back-draft IS abnormal to and caused by the top hole; and probably fed by thicker exhaust fumes pocketed by the front air dam. I've got a much less aggressive front spoiler I'm saving for AFTER front is lowered (and wheels are made; and stripe is painted; and swaybars are on; and...) Guess it's going on a little earlier than planned.

-Dan
 

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Discussion Starter · #28 · (Edited)
Free spoiler

Front spoiler/dam GONE... now so are backdraft fumes into sunroof! :)
-Dan
 

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Discussion Starter · #30 ·
interesting

jeff denton said:
Now that is interesting. You have changed how the air moves around and especially under your car.
I can imagine a wind tunnel test... top off... and ramping that air right of the windshield into the sky, with low pressure swirling in behind/below it (rather than following line over & down back deck... like a plane wing). Crack a side window & move that swirl lower. But, front spoilers strong affect on rvs.draft from bottom-rear of car all the way to top middle? ... interesting... like evil-voodoo. :eek:

greensmurfs intact-top GT will be wearing the front dam in the future! :cool:
 
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