Guest bastaad525 Posted December 23, 2003 Share Posted December 23, 2003 or just possibly help out the aerodynamics of the car slightly, or possibly both. Has anyone tried either installing a diffuser on the rear of the car, or, what I'm thinking is, to tap 3 or four holes, roughly 2-3" in diameter, along the lower valance, in line with the cutout for the exhaust tip. Would this affect either the aerodynamics (in a positive way) or help with the way exhaust gets sucked along behind the car? I'm thinking of having this done.... Quote Link to comment Share on other sites More sharing options...
fl327 Posted December 23, 2003 Share Posted December 23, 2003 I dont know about the diffuser, but in the meanwhile, you could always roll both windows down, that helps. Quote Link to comment Share on other sites More sharing options...
Guest freakypainter Posted December 23, 2003 Share Posted December 23, 2003 blueovalz made a diffuser for his, looks very nice too, but I havent seen anyone with an aftermarket diffuser like an str. I would think that a rear diffuser would help with lift not exhaust fumes. Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted December 23, 2003 Share Posted December 23, 2003 Rolling the windows down makes it worse waaayyy worse. i have been struggeling with this same problem since I have had my car...I always drove with the windows down thinking it was the best option. Then it got colder and I started driving with the windows up. About 80% better!!! Once I replace my seals and get the AC going I will never roll them down again!!! There is a huge dicussion on this topic HERE. Rufus Quote Link to comment Share on other sites More sharing options...
Guest 240hybrid Posted December 24, 2003 Share Posted December 24, 2003 I found that a good rear hatch seal will get rid of the fumes. The one I had when I bought the car let fumes in, even though it was in good shape. After buying a good thick one from Advanced auto parts there are no more fumes except for alittle bit when the windows are rolled down. It cost $30 and I had 1' left over....its the kind that has the wire reinforcment in the part (welting?) that goes over your edge/flange and kind of clamps and holds itself on. It was a lot thicker than the other self-adheisive junk I have seen. I think that the hatch seal has a lot to do with it. My $.02 Oh yeah, like you I smelled like cigars after going for a spin due to the fumes, but after the new seal, I don't get one smell of exhaust unless under hard acceleration with windows down. Good luck Chase Quote Link to comment Share on other sites More sharing options...
CruxGNZ Posted December 24, 2003 Share Posted December 24, 2003 B, Try looking through ZR8ED's post about his "rear underbelly fins idea/exhaust prob fix". Some good information. http://www.hybridz.org/phpBB2/viewtopic.php?t=14817&highlight= !M! Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted December 24, 2003 Share Posted December 24, 2003 After I get home from driving my Z my boys (3 years old) say... " You smell like you hotrod dada!! Makes me laugh every time. Quote Link to comment Share on other sites More sharing options...
Metro Posted December 24, 2003 Share Posted December 24, 2003 Not exactly sure what a difuser is, but 75-76 280z's have 4 rectangle holes in line with the exhaust cutout on the rear valance. 77-78 280s have 1 hole next to the exhaust cutout too. I was wondering what those hole(s) are for.. Anyway, I haven't driven mine yet, but maybe someone with a 75-76 can chime in if they have the exhaust problem too. erm, I just noticed EvilRufusKay has the problem.. so uh nevermind Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted December 24, 2003 Share Posted December 24, 2003 I am pretty sure those holes have something to do with the original bumpers...mine were gone when I bought the car. I don't think they are any kind of vent or have any areodynamic properties. Quote Link to comment Share on other sites More sharing options...
Metro Posted December 24, 2003 Share Posted December 24, 2003 I am pretty sure those holes have something to do with the original bumpers...mine were gone when I bought the car. I don't think they are any kind of vent or have any areodynamic properties. I dun think so, I took the original bumper off mine, I'm not talking about the holes for the bumper shocks. As far as I can tell they serve no purpose. You can see what I'm talking about here Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted December 24, 2003 Share Posted December 24, 2003 Gotcha...yea I have those as well.. I don't think they serve a purpose either...I plan on patching them up. Quote Link to comment Share on other sites More sharing options...
Guest 240hybrid Posted December 24, 2003 Share Posted December 24, 2003 Thats a good one metro/rufuskay. I wonder if they act as a diffuser or not? I have 1 question though about those holes.... how can those holes affect/disturb the air flow when the fuel tank is so close to that area? With the fuel tank so close, I don't see much air going through there to cause enough disrruption of the air to get ride of the swirling affect near the rear of the car. The air will tend to just flow under the tank (a nice smooth surface without many restriction) and keep on going out the rear of the car, NO?? I might be wrong though, as it's been a while since I crawled around under a early 280 to see how much room there is between the tank and the rear valence, but in the 240 its pretty tight. It would be neat to see who has the most problems with fumes to test your' theory...the 240z owners, 260z owners, and 280z. As the 240z (and 260z's) don't have these holes, just an indentation in that area under the bumper. If it does turn out that these several holes help stop swirling of air aft of the car (which I doubt), this may help the problem...a few holes under the bumper. I still think that adequate sealing of the rear hatch and taillights is the most important though. Call me narrow minded... Chase Quote Link to comment Share on other sites More sharing options...
fl327 Posted December 24, 2003 Share Posted December 24, 2003 I guess I lucked out, my hatch weatherstrip is toast, and I still dont get fumes. I run a 3" straight pipe exh with a straight thru muffler with no tip, and my driver side tailight is darker than my passenger side And NO stink...must be the boost. KNowing my luck, when I replace it Im going to get the stinks. My v8z had me stanky everybody who got in the car, girls and guys said the same thing when they got in "smells like gas" Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted December 24, 2003 Share Posted December 24, 2003 Yea I am pretty sure my main problem is simply poorly tuned carb... I plan on trying EFI... I hope it helps. Going really fast only works until you have to slow down!! Quote Link to comment Share on other sites More sharing options...
Guest 240hybrid Posted December 24, 2003 Share Posted December 24, 2003 Yeah that raises another question, as to fl327's setup, since he says that he doesn't get the fume stink in his Zcar with a turbo setup, but did with the V8 setup. I'm just posting what experiences I have encountered with the NA L28 I have currently...we'll see what happens with the my L28et, but I suspect it'll be even less of a problem since it'll be a freshly built motor. I'm starting to suspect, tuning and setup plays a roll in this problem too. My thermotime sensor on the current NA L28 isn't in the best condition (plug is broken and wires saudered directly to the sensor), and causing it to run a bit rich I suspect. But my new rear hatch seal cleared my fume problems up real quick. If I remember correctly, bastaad525 has replaced the rear hatch seal with new and new taillight seals also to no avail. Maybe its just a very rich, or poorly tuned motor, or bad sensor thats causing it to not completely burn the fuel. I know that every setup isn't going to burn all the fuel completly, but some will do better than others. I'm not trying to imply or offend anyone, but just trying every varialbe there is. Bastaad has covered every other option/solution that there is to remedy this problem and it still persisit. I'm starting to draw a blank as what else to help assist his problem. If you haven't inspected the firewall seals and inner shift boot, I would start there. I think I suggested these before, but leave no stone unturned right? I'm at a loss with this one if all else fails... Chase Quote Link to comment Share on other sites More sharing options...
Georgia Flash Posted December 24, 2003 Share Posted December 24, 2003 Listen to this guys, the other day I took off the vinyl cover on the inside of my hatch (located on the underside below the window) while putting on my rear spoiler. This cover hides several large holes on the underside of the hatch. I drove the car to work the next morning with the cover still off and almost passed out due to the fumes! This is an area, that to my knowledge, has never been discussed on this site. I replaced the piece of vinyl and in the process I put a litte RTV around the edges before screwing it back into place. No more exhaust fumes, period! I stumbled onto this exhaust leak problem purely by accident. All I knew was that before I pulled the cover off, my car had zero fume leakage and after it was off they were horrible. I hope this helps someone else out, I would have never guessed that the little piece of interior trim could hold back all those fumes! Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 24, 2003 Share Posted December 24, 2003 First off, I'm running an L28ET, with stock injection, and my fumes are worse now and have ALWAYS been worse than when I had my N/A with SU's. Well it went like this, when I first put the N/A motor into the 240 body, ALL the weatherstripping was toast, and yeah at that point the fumes were eye wateringly bad with the windows down, so-so with them up. So I went and got a brand new hatch seal, and new tail light seals (this was about a year ago), and the smell was 99% gone, only got a tiny wiff with the windows down on hard acceleration or quickly decelerating with the car in gear. Otherwise, no smell, windows down or up. This was with the SU's set to run on the rich side. Then I installed the L28ET, and the fumes went back to being really bad. At first I thought the car was just running way super rich, considering I'd already replaced those seals, but the plugs looked fine and the exhaust wasn't overly blackened either. Well after much searching I found out I had some exhaust leaks at the manifold and between the turbo and DP. Fixed those, and then the smell was mostly gone again. Then it came back after a month or so. Then I put that piece of trim on the lower part of the hatch, the vinyl section Georgia Flash is talking about, and sealed all around it with fresh silicone, and also went and sealed just about any hole I could find at the rear of the cabin. It went away again. Sorta. Now... a month later, and nothing has changed as far as I know or can find, but the smell is mysteriously back and just as bad as ever. I went and dynoed the car last week, and at cruise it's not running too rich or anything, though it does run rich on boost, for what that's worth. But I get bad fumes in the car even when just cruising, and of course when accelerating hard it gets really bad. Also a new trend has started, where I will get fumes the worst when I'm taking a turn at speed, like on a freeway-to-freeway junction ramp. And I get fumes now whether the windows are up or down... this has gotten so bad in the last week that I've decided to stop driving the car. And again, nothing has changed so far as I can tell. I've gone thru and checked all my seals, all are still in great condition. I checked the bolts on the exhaust manifold and they are all tight, no evidence of an exhaust leak anywhere in the system. I decided maybe it was blowby exiting the crankcase or valve cover vents, which I had open to atmosphere (with filters on them). So I replumbed them back into the intake. I even went and replaced the hoses that run from the fuel tank to the vent tank inside the car. No dice. So... I just about give up, I really dont know what else to do and I have NO idea what could possibly have changed so dramatically to go from being able to cruise with the windows down no problem to having watery eyes and hacking cough any time I drive for more than 10 mins, windows down or up. The car doesn't feel like it's running any differently, and the plugs dont look any different than they have for the last couple months. This smell is a mixture of exhaust and sometimes what I think is burning oil. It's driving me nuts. I'm strongly considering throwing some performance out the window and installing a catalytic converter. Will this make the exhaust stop stinking, and stop burning my eyes, throat and lungs? My concern is that I'm not sure it will help only because I'm not 100% sure that it's exhaust coming out of the tail pipe that's finding it's way inside the car... but damn I have checked and tripple checked EVERYTHING else!!! Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 24, 2003 Share Posted December 24, 2003 OH and I've also tried extending the exhaust tip out a few inches with no results. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 24, 2003 Share Posted December 24, 2003 blueovalz made a diffuser for his, In reality, mine is just a belly pan for aesthetic reasons and functions only. Airflow directionality, as well as speed under the car is not controlled to the point of where I would call it a diffuser. ZR8ED has one that would be a step closer in the direction of what a diffuser would be. The air under my car could be assumed to be turbulent and chaotic, at which point it may reach the edge of the rear bellypan and either go over the leading edge (which helps cool the fuel tank, fuel pump, and fuel filter from the heat generated by the two mufflers under them), or under the pan, but either way, there is no uniform direction to the air flowing under it, and hence, little affect gained in lowering the air pressure under the car. I still say a slight positive pressure inside the car will eliminate the odors. Quote Link to comment Share on other sites More sharing options...
Guest 240hybrid Posted December 24, 2003 Share Posted December 24, 2003 Yeah, GAflash makes a good point about the rear hatch panel, but I haven't even reinstalled mine yet and no fumes enter the car as-is. If you don't have those metal bumpers or stops (whatever they are) that are on the side of the hatch, you'll prob. have the problem with fumes. I'm at a loss as to your problem bastaad...everything has been covered I believe. Chase Quote Link to comment Share on other sites More sharing options...
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