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Andrew Bayley

Can a rear spoiler reduce exhaust fumes?

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I just wanted to add something to this thread, I haven't read the whole thread so if this has been mentioned already, I apologize. I was replying to anouther thread about the bottom of the fenders rusting out because of the water draining from the plenum getting caught in the fender. Here is a link to the thread http://forums.hybridz.org/showthread.php?t=107620

 

As I mentioned in that thread, leaves and pine needle often get trapped in the fender bottom where the plenum drains and cause rust. Well from experience as a paint and body man for over twenty five years, I know junk can also get trapped in the plenum itself, causing the firewall to rust. Sometimes this causes exhaust fumes to be vented into the interior from the engine compartment. Also, because the pressure inside the car is lower then on the outside, any holes in the floor boards can also allow exhaust to leak into the car. Often people don't even realize there are holes in the floor boards because carpet or undercoat is hiding them.

If you have replaced your rear hatch seal and the tail light seals or confirmed they are in good shape and exhaust is still entering the car, this may be your problem. Checking the floor panels for holes isn't that difficult, but really checking the firewall is tougher. The dash really must be removed to get a good look. Sometimes you can crawl under the dash with some caulk. Also any holes in the trunk / spare tire area or even the inner quarter panels could allow fumes in.

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Sadly' date=' the 240-60-80Z has one of the worse shapes in terms of aerodynamics of cars in recent memory. It has small cross sectional area, which greatly helps. But apples-to-apples, it had more drag and un-downforce (lift) than cars like the Chevy Chevelle. Basically, the reason is that for good aero performance, the car’s body should be smooth and swoopy in some places, but sharp and abrupt in others. Generally, the smooth part should be up front – the grill area, the headlights, the hood/windshield juncture. The sharp and abrupt part should be in back – the trunk, rear of the cabin, etc. The Z is swoopy and smooth in precisely the wrong places, and sharp and abrupt – again! – in precisely the wrong places. It’s almost as if the Z’s designers worked long and hard to deliberately do a bad job on the car’s aerodynamics. And to add to the injustice – cars like the VW Rabbit and Ford Pinto had far superior aerodynamics![/quote']

 

dose that mean i need to swap my Z so i drive looking out the hatch? >_> or swap the shell around..... err sorry ill stop beign cute..... But let me ask this is a 240z more aerodynamic in Reverse then it is when in 1st gear?

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I question whether the fumes come through the hatch. My 280Z smelled horrible. I put all new weatherstripping in. My 280Z smelled horrible. I put a new exhaust on the car. My 280Z smelled horrible. I put in an SR20DET. Smell was gone. Does anyone wonder whether the smell is coming through the firewall or up the transmission tunnel? Now, when I blow a turbo gasket, I get the smell again. The rest of the time, I have no odor issues.

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In all the efforts to reduce or eliminate exhaust fumes drawn into the car has anyone tried to minimize the low pressure area in the rear? I was thinking that narrow plastic scoops mounted in the rear wheelwell opening (out of view) could be vented up and out the rear valance, just below the bumper, via hose. The outlets could be installed to look factory and visually pleasing. The idea is the low pressure would draw air out of the wheelwell (and from under the car). This might have a positive effect on downforce and lower that notorious low pressure area too. It might help to reduce fumes getting pulled into the car with open windows. I wish I had access to a windtunnel to test the theory. This would supplement the replacement of all rubber and filling of all holes, of course. It's just a thought... What are your opinons?

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I think it makes a lot of sense. (That holes in the floor board would let fumes in)

 

As long as I keep my windows up imy car stays fume free. But the second I even crack a window I get a proverbial smack in the face from obnoxious fumes. I'm gessing that its coming up through a couple small dime sized holes right beneath the seat. I'm going to make it a point to seal those up. Somehow. Suggestions?

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You might try body seam sealer to plug the holes and gaps in the floor and firewall. it`s also possible that your fan is drawng exhaust fumes from the engine compartment through the cowl panel. BUT...

If your exhaust system if working properly, you should NEVER get exhaust fumes from the engine compartment.

 

DENNY

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Guest Heuristicism

I AGREE with Denny411 !!

 

Take care of the problem that exists, you don't need a 'band-aid' ahemm I mean spoiler.

 

Lets see, smelly fumes could equal, rich running engine, oil leaks, coolant leaks (headgasket), bad cat, bad exhaust system, bad sealer for tailights, rust holes, and the list goes on.

 

I think that if you FIRST address these possible problems it would reduce the smells that you are experiencing.

 

Once solved, go ahead and get that spoiler....

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Guest Carolina280Z

Man after reading all of that , is there a laymens explanation anywhere, that was some post

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rear quarter panel damage can end up leaving a gap between the inner fender and the out rear quarter panel... it can also cause gaps in the little panel that has the filler neck gromet... Nissan used a thick bead of tar-like substance to seal the inner and outer fenders... check that this is still in place and actually touching the outer quarters.

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I suspect some of the problem might be because of the Carbs too. I've long suspected that my un-filtered su's are not sucking in all the fuel that is getting to them, because as soon as you open the hood, you get hit by the fume fist-stinging eyes and all. I read an article in Grass Roots Motorsports detailing their conversion of a Volvo 122 from dual Su's to megasquirt fuel injection, and they described how their fume problem magically went away after that too. This is in keeping with the Sr20det story mentioned above, as well. It can't be the only thing, but it's something to think about. Anybody have any "I used no filters/open element filters, and when I switched to a plenum my fumes went away" stories?

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Great thread to revisit.

 

I may have missed it and if I did, I apologize for being redundant, but in regards to “sealing” the back of the car, I saw no mention of sealing the latch under the hatch and behind the license plate. These are areas that exhaust fumes from behind the car come into the rear hatch area via the vinyl interior cover of the underside of the hatch itself.

Back in the early to mid ‘90’s when I had the dual exhaust on my L-28 powered 280-Z exiting out of the OE rear bumper holes, only about 2” out past the rear valance, I did get fair amount of exhaust fumes in the car. I had no fin, wing etc, see pic below… When I swapped in the V-8, I retained this exhaust arrangement, except it was dual 2.5” instead of dual 2”.

 

 

280Z1.jpg

 

 

 

 

So I set out to seal the back of car 100% from any air flow in or out. What I mean by the “back of the car” is the entire rear valence/taillight area.

At first I recognized that even if the taillights are sealed good, and the rear hatch sea itself is in good condition, that the exhaust fumes can easily get behind the license plate and between the hatch and body itself, then up through the hatch lock, and into the space between the outer and inner hatch skin and ultimately into the interior through vinyl covering that allows access the hatch lock mechanism. In the first picture using a parts car as the example, the upper circle is the area between the hatch and the body of the car that needs to be sealed, (the bottom picture shows one method of using weathering strip to do just that). The lower green circle in the upper picture shows the latch hook as it is behind the license plate which allows exhaust fumes up into the hatch itself. (These pics are of a 280, the 240 would be similar). On my personal Z car back in the day, I just used duct tape to seal off the latch hook under the license plate. This is the BUBBA way out, but it did help. I’m sure that someone could easily make a Fiber Glass cup that could easily be attached under the license plate to seal that off, of course make it removable to be able to make hatch hook adjustments.

 

 

 

 

 

LAtchLarge.jpg

 

 

Latch1Medium.jpg

 

 

Just thought I’d throw out my $.02

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I solved my stinky exhaust problems by pointing my exhaust tip to the side, behind the left rear tire under the bumper. Just cut a round hole and stick that supertrap out the side. I drive about 4,000 miles a month on the interstate in my 71 240 and it was killing me, problem fixed zero fumes.

Karl

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Guest skar280

Just a question for Michael. What would the effect of a primary spoiler mounted in front of the hatch at the back of the roof be? Would it create enough turbulence to minimize the back draft behind a rear mounted spoiler and perhaps assist with downforce (kind of like an older toyota supra)

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The spoiler you are refering to doesn`t really generate downforce. It actually reduces lift by disrupting the airflow that is flowing over the hatch at speed.

if you search, there is a very long thread about this and other aerodynamic features of the s30.

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I solved my stinky exhaust problems by pointing my exhaust tip to the side' date=' behind the left rear tire under the bumper. Just cut a round hole and stick that supertrap out the side. I drive about 4,000 miles a month on the interstate in my 71 240 and it was killing me, problem fixed zero fumes.

Karl[/quote']

Karl,

 

Dou yoou have a picture showing the exhaust tip job. Fumes are driving me crazy..

 

thanks

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I too had done everything mentioned here (except BRAAP's) and still had fumes. I was especially frustrated that after the expense of changing the hatch seal that it was no better. In my case, sometimes things were great, and other times eye watering.

 

After a lot of noodling, I came up with the theory that over bumps the chasis was flexing and the rear hatch was moving around on the seal and at times, allowing gaps to form. This of course would allow the poor aerodynamics to vent fumes into the cabin.

 

I got in the back with the hatch closed and took a small piece of paper and tried to push it between the hatch and seal. Where there was a good fit the paper would just buckle, but there were a lot places where it slid right in with almost no resistance. That confirmed that even with the car standing still on my flat garage floor, the hatch didn't fit the seal very well. I'm sure some of that was due my not being sensitive to this issue when I glued the seal down, but since it was already done, I needed to try something else.

 

I did notice that I had more "gaps" on one side than the other, so I opened the hatch, and grasping the corners, "tweaked" it to get it closer. I then tried moving the latch mechanisms up and down (and forward and backward) and eventually found a combination that allowed the hatch to close rather easily, and where the paper buckled almost everywhere. This is how I have it now, and the fumes rarely come in.

 

My conclusion is that after you have done all the fixes, there is still some trial and error involved to get the hatch set "just right" to maximize how well the seal fits. I'll add that I still need to add a rear strut bar, and am hoping that will stiffen things up in the rear to help even more.

 

Note: if you think about it, the hatch is only held in 3 places: at the top left and right corners (by the hinges) and in the center of the bottom by the latch. That leaves a lot of room for it to move around, expecially when you consider how "flexy" the rear of the Z is.

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Mario, sorry I have not gotten back sooner. I do not have a digital camera, but I assure you that It works. You can also just put a 90degree smooth bend on the end of your current exhaust pipe and point It away from the car, this is what I did the first time I tried It. I drive alot to see my wife and kids and the fumes were killing me. I found the cure on accident while building a bike rack, I pointed the exhaust to the side so the heat wouldn't get to my mountain bikes shock and the fumes were gone. I had tried everything else listed here but nothing worked, now with all the driving I do I have zero fumes. I am getting ready to do a 7MGTE swap and am going to point the turbo exhaust out the same hole (I'm gathering rear end parts for the r230 swap, have everthing else, and with CLIFTONs help It will be awsome) good luck

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I got my rid of my fume smell a little while ago, thought I would share my limited knowledge.

 

I replaced the hatch seal and the taillight seal. this didn't change the smell one bit. I found the leak after i put on this weird plastic valve cover and the engine started to pull oil into the carbs. you could see the smoke coming in from the interior vinyl hatch cover. I used lexan and some foam weatherstripping and sealed it.

 

Problem solved. the car's floors were not sealed nor the vapor line grommets. but I had No fumes at all. Maybe this breif info will help someone.

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