Pop N Wood Posted September 12, 2002 Share Posted September 12, 2002 My 1970 Z has never stunk of exhaust fumes. Wait, I take that back. It did one time. But that was because I had a bicycle in the back with the hatch propped open. When I bought my car used 13 years ago, the guy who restored it had replace all of the rubber seals. Thus that is my guess. Replace all of the rubber, adjust the hatch so there is a solid seal all the way around, check the taillight gaskets and make sure there is no rust or exhaust leaks. I have always wondered why some cars (like Volvo's) run the exhaust pipe all the way to the rear, then at the back of the car make 2 90 degree bends to have the exhaust dump outside of the rear corners. Last idea. Ever drive an old station wagon with the rear roll down window? Those use to be exhaust fume death machines also. But most of them had a curved spoiler at the top of the back hatch that blew air down from the roof past the hatch. Don't know if that would work with a Z but it did with the old wagons. Quote Link to comment Share on other sites More sharing options...
Bob_H Posted September 14, 2002 Share Posted September 14, 2002 280Z stinks of exhaust fumes, like nearly every other gen one Z out there. The fact is, they didn't when they were new or they would not have sold. Important fact, the stock exhaust pipe was cut at a 90 degree angle and extended out near the edge of the bumper as I mentioned in my first post. As soon as you start changing ANYTHING with the exhaust tip, that goes out the window. I have all new seals in the back of my car, and the rear hatch has contact all the way around,(good contact). I had the smell/fumes pretty bad at about 45 mph. While I haven't changed my exhuast from the 45 degree tip cut I have on it right now,(vain bastard) we did try something. Borrowed a 90 degree cut pipe,(not a bend, but a flat surface) to go over my tip, about the same overall distance, i.e. just behind the bumper as you look straight down. Significant difference in how much "smell/fumes" came in the cabin at the speed mentioned above. The best is to angle it down. Angling it up as Scott has is the worst possible combination for the exhaust. It should be fairly apparent that the area right behind the tail lights is a dead spot airflow wise. He is dumping his exhaust right into that spot. So if there is any reverse flow up the side of the car,(common on bodies at slower speeds), he will smell the fumes, sealed hatch and seals or not. While there is no denying the cool factor of the rear diffuser, I don't think it addresses the problem. It may help, but I think he will still find some fumes present. It is a quick simple check to turn it upside down and see what it does. If the muffler is welded in place, then purchasing a cheap-o 90 degree bend for each tip at the local auto parts store,(that puts them 45 degrees down vice 45 up). It may mean he has to get rid of the cool muffler he currently has, or modify the tip if he finds the above suggestion works. I was saying it gently the first time. This time I will say it a little more clearly. Scott, your exhaust tip is a major factor in your smelling fumes. And having the rear spoiler only makes that dead spot more prominent. Go for the rear difusser if you want, but I don't think it will solve the exhaust probs,(but it will look awesome!) -Bob Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted September 25, 2002 Author Share Posted September 25, 2002 As always things seem to snow ball on me.. Thanks all of you very much for the comments. I completely aggree with your theory of my muffler.. but it looks too cool to lose it.. So I'm going to suffer with it, and try some areo effects to help ease it.. I guess I'm a slave to Form over Function.. Darn proud of it or I'd be driving an electric car to the cruise nights. hehehe I'm proceeding with the veritical diffusers, but now as per my usual thoughts of "I can do anything if I throw enough time and $$ at it" I'm going to experiment with installing a rear belly pan. There is another Z'r that has his car serviced by the Z Master, and he is copying my front belly pan, and is currently setting up for the rear pan, so I'm going to help him, and take the ideas over to my Z.. It should work out much better this way.. My front pan is removeable, and so I'll make my rear one the same... Best part is once I have the pan in place, I can shape my diffusers to the pan, and have them tig welded to the pan!! No worries for mounting!! All this fooling around while I'm in the middle of installing the new motor in the Z. Its almost done.. week or so needed to finish it off. I'll take pics as this progresses, naturally. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted September 29, 2002 Share Posted September 29, 2002 ZR8ED even if it does nothing it looks kinda neat Quote Link to comment Share on other sites More sharing options...
Mudge Posted January 21, 2003 Share Posted January 21, 2003 ZR8ED, any feedback on this yet? Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted January 21, 2003 Author Share Posted January 21, 2003 I made up some templates for the "fences", and other than that, everything I'm planning, is on hold till spring. I don't have access to the car during the winter, so I can't take any other measurements or trial fitting. As it stands, the car still has an exhuast problem unless the windows are fully up, or fully down. I won't give up on this project er..quest..hehe Quote Link to comment Share on other sites More sharing options...
Mudge Posted January 22, 2003 Share Posted January 22, 2003 Yep, if I pull the windows down about 2" it begins. I was told on an email list I'm on, by a knowlegable guy that most diffusers are 4-11º, his will be 9º, how long? I dont know. http://www.corner-carvers.com/ There is another board which may be helpfull, I saw track records there some time ago and never knew they had a forum Quote Link to comment Share on other sites More sharing options...
strotter Posted January 23, 2003 Share Posted January 23, 2003 Speaking to the "it smells because seals are worn" theory, I may have an appropriate thought to test it: I was watching "This Old House" a couple of years ago, and they had a neat technique for finding air leaks in houses (which they were looking to insulate). They installed a fan in the front door to pressurize the house, and then used a smoldering pencil-sized "dealee" to generate a bit of smoke which they held in likely areas to determine if air motion was taking place, thus isolating the leaks. Lots of leaks around windows and electrical outlets and whatnot. I looked at Home Depot and nobody knew what "smokey pencil dealees" were, so I came up with the next-best-thing: incense. I closed up the car, turned on the heater fan, lit up the incense, and proceeded to find *at least* six HUGE sources of air motion. Under the car (past a seal that looked good), in the back (wiring seals and tail-light bolt holes) as well as a couple on the firewall. This weekend I'm going to get the silicone out and go crazy, see if I can eliminate that damned monoxide stink that's ruining my day. I'm also going to try a straight-ended extension pipe on the exhaust. On a practical note, make *damned" sure you like the incense smell before you try this, as your car is going to *reek* of it after you're done. Quote Link to comment Share on other sites More sharing options...
WHP Posted January 24, 2003 Share Posted January 24, 2003 Right, the cars did not stink when they were new. When the window is opened the inside of the car becomes negative pressure sucking air in anywhere it can. Check hatch seal, taillight gaskets, signal bulb sockets, rubber body hole plugs in rear hatch floor area, rust holes in spare tire well, gromets around emission hoses behind the rear interior panel, leakage thru rear hatch latch into rear hatch (pressboard cover panel is probably warped and leaky by now), quarter panel or inner fender well rust holes, exhaust system leaks near the shifter boot, etc. There are a lot of possible air entries on a 30 yr old car. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted January 24, 2003 Share Posted January 24, 2003 Rolling the windows down 2 inches will suck air out of the passangers compartment, not blow it in. Use to put the windows at that height when I smoked cigars to draw out the smoke. Any farther down and the turbulence kinda blows it back in. Must be like a venturi. But if the windows are drawing out air, then it has to be replaced from somewhere. This might suck in the exhaust from leaks in the rear of the car. One other thing. On zcar.com there is an excellent write up about Z car aerodynamics. This ariticle claims the smooth rear hatch allows the air to flow so fast it actually creates a few hundred pounds of lift off the rear wheels. This could easily pull open the seams of the rear hatch. Perhaps the answer to excessive exhaust fumes lies in managing the airflow over the top of the car and not underneath??? Maybe some type of spoiler/bump at the top of the hatch? And Scott T: Instead of incense, just invite a couple of buds over and turn the Z into a giant bong Quote Link to comment Share on other sites More sharing options...
Z_Dust Posted January 25, 2003 Share Posted January 25, 2003 I use to have another brown colored 77z that my friends called the snickers bar. It ran great and pulled hard. Never did I had exhaust fumes problems wit it. I do remember that the pipe from the exhaust extended past the bumper about an inch and a half if not two. My current 77z can smoke a bad date off your car in three seconds flat, just roll down the windows. With the windows up it's very minimal, so I suspect some leaks. Quote Link to comment Share on other sites More sharing options...
strotter Posted January 25, 2003 Share Posted January 25, 2003 Ah, but Jim, it's fuel injected. No more *carburator*! Yuk yuk yuk! Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted February 6, 2003 Author Share Posted February 6, 2003 Hey guys. While reading a post in this same forum about "whats the 240's drag coefficient". I read an interesting article reagarding this issue, and touches on the rear slope of our cars causing lift.. Ok now... remember the 82-85 Toyota Supras? with that wing near the top of the hatch? (actually designed as a sunshade for rear passengers) A spoiler of that type might disrupt the flow of air over the roof of the car..maybe this might help that dead area behind the z.. might help with fumes getting in... (I know they didn't do it stock, but I'm getting tired of smelling fumes when my window is down, have made a ton of fixes and I'm grasping at straws now..) Anyways someone who's z is not in winter storage could try this.. I was thinking of how to experiment with this without making permenant holes etc.. on our cars to test a wing... Then it hit me. Imagine a wing like that on the back of Blue Ovalz car.. angled and essentially a flat sheet (I'm simplifing this a bit) You could make this from aluminum, and bend a lip in it that could be tucked between the hatch seals and close the hatch on it to hold it in place... (hmm didn't some of the cars in mad max had a rear roof spoiler kinda like this ?) You could then drive the car and (hope it doesn't fall out and scratch the car) and see if it reduces the exhuast fumes... technically it should kill a lot of rear lift according to the article... it might not have to be all that tall to disrupt the air...1-2" high? I'm just sitting here thinking this stuff up...its been a long winter so far.. Anyone have any thoughts on this.. Anyone with a not painted car want to try this?.. (incase it fell out) Anyone have a fume ridden cabin desperate enough to try this? I'm going to file this till spring...I'm crazy enough to try just about anything at this point.. Quote Link to comment Share on other sites More sharing options...
Mudge Posted February 6, 2003 Share Posted February 6, 2003 Originally posted by ZR8ED:A spoiler of that type might disrupt the flow of air over the roof of the car..maybe this might help that dead area behind the z.. might help with fumes getting in... (I know they didn't do it stock, but I'm getting tired of smelling fumes when my window is down, have made a ton of fixes and I'm grasping at straws now..) "Ed", someone mentioned a possible firewall leak, any thoughts? Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted February 6, 2003 Author Share Posted February 6, 2003 I did find 2 firewall leaks.. for harnesses passing through the firewall.. I've since plugged them with sealer.. not sure on the effects though, as I did them in the fall, and it was too cold to drive with my windows down. It is a good thing to look at though.. everyone looks at the back of the cabin.. And to who ever mentioned "carbs" not FI add to this problem.. I have a FI car.. Quote Link to comment Share on other sites More sharing options...
Mudge Posted February 6, 2003 Share Posted February 6, 2003 I wonder about those fargin holes on the floor boards, why are there holes and no plug? Maybe my plugs are just gone... Quote Link to comment Share on other sites More sharing options...
Guest livewire23 Posted February 6, 2003 Share Posted February 6, 2003 my plugs must be gone too. If I look down, I can see the road go whizzing by. Talk about scary. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted February 9, 2003 Author Share Posted February 9, 2003 http://www.hybridz.org/ubb/ultimatebb.php?ubb=get_topic;f=13;t=000358 Just wanted to link this to the "Coefficient of drag for 240Z" thread since the two topics are kinda crossing over here. Quote Link to comment Share on other sites More sharing options...
strotter Posted February 9, 2003 Share Posted February 9, 2003 A follow-up to my "incense" idea. I applied silicone to every leak-point I could find, and a couple I just imagined. Car stunk of silicone. After it set up a bit, I went for a ride - there was *still* an exhaust smell, though not as bad. Last week I was in Kragen getting some oil, and I noticed that they had some cheapo chrome exhaust extensions. Made me think about Bob H's comment about the exhaust tip. Eight or so inches long, 45 degree angle cut on the end. Picked one up, fastened it to the exhaust outlet with a hose-clamp so that the bottom was about 2" past the bumper. The top was probably 4" past. Looked stupid, but I tried it anyway, and IT WORKED. Window down all the way, window down 4", both windows down, etc etc etc. Seems Bob H was right! Try it! The little exhaust extensions are cheap, it's an easy experiment. Think about what the original Z exhaust looked like - it stuck out an inch (or more?) past the bumper. Perhaps that's what everyone is suffering from - muffler wears out, they replace it with a better-looking one (that's shorter, 'cause those long ones look goofy), and *boom*, you've got a headache. Could it be that simple? Quote Link to comment Share on other sites More sharing options...
dot Posted February 10, 2003 Share Posted February 10, 2003 I was at a party for a close retired friend. He was an engineer whose field of specialty was aerodynamics. His company built the wind tunnels for Porsche and Honda. I asked his opinion on the topic. I got a typical 88 year old’s response. “How should I know? Sounds like you got a vortex working there.†He later told me how a Jag he had in the seventies that had the same problem. The factory cure was to put some funny looking “S†pipes on the rear that put the exhaust out in the wind stream instead of taking advantage of the vacuum area at the rear. Scott is on to something. It would be interesting to see what a ribbon tide to a pipe would do at speed. But this raises the issue of fashion over fumes. Brings tears to my eyes… Quote Link to comment Share on other sites More sharing options...
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