Toxic cabin

Michael Holmes

Lifetime Supporter
I've decided no more multi-hour drives in the GT until I remedy the toxic gasses in the cockpit. I've done much to eliminate any passage ways between the engine bay and cockpit but without quality fresh air coming in it is still a health hazard.

My thinking is to drill 3" holes in the front bulkhead (same location as original MK1's and venting fresh air in from the NACA ducts on the front wings. I am also considering using a bilge fan to bring the air in regardless if the car is in motion. Comments please.

Also I am considering putting vent holes in the rear engine bay Plexiglas to expedite the removal of unburned fumes from the Webers as well. Comments please.

Thanks
 
I've decided no more multi-hour drives in the GT until I remedy the toxic gasses in the cockpit. I've done much to eliminate any passage ways between the engine bay and cockpit but without quality fresh air coming in it is still a health hazard.

My thinking is to drill 3" holes in the front bulkhead (same location as original MK1's and venting fresh air in from the NACA ducts on the front wings. I am also considering using a bilge fan to bring the air in regardless if the car is in motion. Comments please.

Also I am considering putting vent holes in the rear engine bay Plexiglas to expedite the removal of unburned fumes from the Webers as well. Comments please.

Thanks
If you can pressurize the cabin to a greater pressure than the engine bay you will solve a lot of the issue. That said, very hard to do with the scoops filling the engine bay at speed to a pressure greater than the cabin!

A good seal hunt on the cabin to engine bay will help as will the inlet of fresh, ambient air. The bilge fan idea is probably best if used to extract cabin air thus requiring fresh air to replace the lost volume.
 

Michael Holmes

Lifetime Supporter
If you can pressurize the cabin to a greater pressure than the engine bay you will solve a lot of the issue. That said, very hard to do with the scoops filling the engine bay at speed to a pressure greater than the cabin!

A good seal hunt on the cabin to engine bay will help as will the inlet of fresh, ambient air. The bilge fan idea is probably best if used to extract cabin air thus requiring fresh air to replace the lost volume.
So if I use one of my bulkhead holes as a fresh air in (no bilge fan) and the other as air out (with bilge fan) would that be something to consider? OR is it better to bring as much fresh air in (bilge fans for both sides) as possible?
 

Ian Anderson

Lifetime Supporter
Supporter
I had the same thing on the Dax when I gt it on the road - so much that for a couple of years I drove without the drivers window!

I then started sealing the bulkhead.

First the bulkhead cover for the front of the engine - I ran around the outside of it with 13mm wide 2mm closed cell foam rubber. then screwed it back in place and the difference was huge!

I then lifted the carpet around the handbrake and sealed it with aluminuim tape - then reinserted the carpet

It then almost became bearable but still too hot to drive

So I then had 2 ducts from the front brake ducts plumbed in (with 2 bilge fans (4 inch) for traffic) and the difference is huge - fresh air all the time and at anything over about 15 mph no need for fans

Be aware if you drive in cold weather you may need to stuff a sponge into the duct to reduce the extra cold air as it can be a "bit too much"

See post 132
http://www.gt40s.com/forum/gt40-build-logs/17398-dax-build-up-7.html

Ian
 

Jim Craik

Lifetime Supporter
One thing I have found, although it may be only a temporary fix.

I find if I open the little window vents, it creates low pressure in the cabin and draws air in from both the front and rear bulkheads. If I leave the window vents closed the car stays cooler and has less fumes.
 

Michael Holmes

Lifetime Supporter
One thing I have found, although it may be only a temporary fix.

I find if I open the little window vents, it creates low pressure in the cabin and draws air in from both the front and rear bulkheads. If I leave the window vents closed the car stays cooler and has less fumes.
Interesting thought. I have the small windows off as the builder did not buy the hinge and latches. Guess I will.

Regards
 

Cliff Beer

Supporter
Michael,

I assume you're smelling gas fumes....

One fix that I think works well for multiple reasons is small powered fans on the rear clam shell actively sucking engine bay fumes out the back. This both helps to keep the positive pressure down in the engine bay (less fumes into the cabin), and helps to keep engine temps down. Spal makes nice little 6" low-amp fans which can be either pushers or pullers and they come with a nice frame around the fan for easy mounting. Just an idea.
 

Dwight

RCR GT 40 Gulf Livery 347 Eight Stack injection
Supporter
Chuck's idea may help

http://www.gt40s.com/forum/gt40-build-logs/22083-chuck-ryans-rcr-build-34.html



Re: Chuck and Ryan's RCR Build
Blow Job

The persistent summer heat has not prevented us from driving the GT. The air conditioning makes an evening drive in ninety plus heat quite manageable. But the engine compartment does not seem to be faring as well.

Lifting the clip after an hour drive in ninety plus heat revealed a worrisome issue. The fiberglass above the engine was very hot to the touch and soft, almost pliable. There was no visible damage, but such high temperatures can’t be good. One can’t always raise the clip after shutting down when stopping away from home.

It seems that the hot air stagnates below the clip above the engine. At low speed I suspect there is little air movement. Driving in traffic is tough to avoid. So a means of moving that air was sought.

There are two five inch diameter access openings on the sponsons. They come drilled and tapped for a cover plate. Air drawn from that opening enters from the rear of the sponson; seemingly an ideal source since it is low where the air is cooler and in a area where the aerodynamics of the car should not affect the air flow.

We found the perfect fan for this application. Derale Cooling Products, Part number 16505, available from several sources including Summit. It is five inches in diameter and fits perfectly over the opening on the sponson. It moves 325 CFM of air and draws 3.6 amps. Those are respectable specs for such a small fan.

The fans have three mounting tabs. Two line up perfectly with the existing holes for the cover plate. It was a simple matter to drill and tap the third. Quarter inch nylon spacers were placed below the mounting tabs so that the screws could be tightened down without damaging the mounting tabs.

The fans are only 1.250 inches thick and thus do not interfere with the suspension. Indeed, once installed they are difficult to see, blending in well.

The fans were wired through a relay. The relay is activated by a switch on the dash, giving us the option of keeping the fans on after the car has been shut down. When the car was originally wired an extra wire from the dash fan – override switch was run to the rear of the car for this contingency.

With a total of 650 CFM the fans blow plenty of air. Stopping after a brisk three quarter hour drive in ninety degree heat, one could feel the flow of warm air being blown from those fans at the openings of the rear of the clip above and on either side of the exhaust pipes. The fans move the air from the front to the rear of the clip effectively. This will supplement the natural flow from the side vents when driving at speed.

Most important, when the clip was lifted the fiberglass was not nearly as hot and did not have that soft, almost pliable feel.

The fans are loud. They sound like typical electric radiator fans. You won’t walk away from the car without realizing they are on. Of course the sound inside the cabin is subdued and not that noticeable compared to the sound of the engine a foot from your ear.

Yarn tell tales taped to the rear clip move noticeably when the fans are on confirming the flow of air out the rear of the clip.

Check out the video version . . . . .

http://www.youtube.com/watch?v=v0i3Htxd9I4
Attached Thumbnails
 
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I did essentially what Chuck and Ryan did except with Spal fans. My engine builder blistered the paint over my exhaust during a tuning session. The car was siting still for about an hour with the motor running which led me to extra insulation of the clip portion just over the exhaust. It was about that time I decided to use the fans also, about the time Chuck came up with his. To be safe I added an off delay relay. It allows the fans to run for a predetermined amount of time after the engine is shut down. Later on I will incorporate the electric water pump into the timer to cut down on heat soak. They can be had with any time that you want them to run, from a few seconds to more than several hours. I have mine at 3 minutes which seems like a long time when you stand there waiting for them to turn off, but they do the job.

Bill
 
Another alternative, dont run with side windows in very hot weather, we use these small wind deflectors, mounted into the same fixing holes as the perspex, and these make a very comfortable but wind free cockpit, Frank
 

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Randy V

Admin
Lifetime Supporter
Frank, those look very nice. Particularly the ones on Martin's car. I wonder if they would fit my RCR doors? Fiberglass? Hmmmm....
 

Ian Anderson

Lifetime Supporter
Supporter
I did nention that for the first couple of years I drove mine without side window on drivers side.

Even without the deflectors it was comfortable inside p to about 80mph - after that I got a bit more wind noise but still not badly buffeted inside

If you have rivnuts in the door to screw the window in place try removing it - start to finish I could do it in less than 5 minutes!

Ian
 

Malcolm

Supporter
A source for heat getting into the cabin in a GTD used to be from the engine bay, down past the tanks and up the gear stick mechanism. I used to be able to feel an updraft! A well made gaiter stopped that source of heat and if you are getting fumes they may be getting picked up along the way. My concern over what is being said here is that you should be more worried over the source of the fumes rather than just looking on how to get rid of them better. If gas fumes then perhaps you have a fuel leak somewhere and that ought to be sorted pronto. If exhaust fumes then is the exhaust properly sealed? Heat from the radiator should not be toxic just unpleasant. What other source of auto related toxic fumes are there in a car? But running without windows is nice!
 

Michael Holmes

Lifetime Supporter
My concern over what is being said here is that you should be more worried over the source of the fumes rather than just looking on how to get rid of them better. If gas fumes then perhaps you have a fuel leak somewhere and that ought to be sorted pronto. If exhaust fumes then is the exhaust properly sealed? Heat from the radiator should not be toxic just unpleasant. What other source of auto related toxic fumes are there in a car? But running without windows is nice!
I have done a major reseal of the fire wall, including plugging holes and weather-stripping the rear body work. Given that there is negative pressure in the cabin any fumes, be it unburnt petrol from the Webers, crank case venting or exhaust are finding it's way into the cabin. Worst in stop and go than at speed.

Instead of cutting into the bulk head I have decided to use the access panel (1965 GT40 MK1 #1 Details) just above the foot well to add an electric fan. This would bring in "fresh air" from the front of the car into the cabin. My thinking it is better to bring in this air even if it will be warmer than ambient air given the proximity to the radiator than the stagnent air I currently am dealing with. Additionally my asumption is that it is better to bring air in rather than mount the fan to extract the fumes out. Extracting the air would be creating a greater negitive flow causing more fumes to find thier way in not less.

Comments?
 

Keith

Lifetime Supporter
One of the few changes I made to mine after I got it on the road was related to a fuel smell. I had installed the fuel tank vents/roll over valves up by the fuel filler caps so that they would be hidden under the front clip. Under deceleration the fuel in the tanks would race forward in the tank and vent the vapor out the roll over valves under the front clip. The vapor collected in that area and seeped into the passenger compartment thru the gaps in the front of the doors. The more spirited I drove the car the worse the smell. I fixed it by taking the top caps off the rollover valves and drilling and taping (1/8 NPT) for a barb fitting then running a piece of neoprene fuel line from the barb fitting under the car into the rocker pannel area. The fuel smell went away.
You may want to take a look at where your fuel tanks are vented to see if you have a similar issue...............
 

Michael Holmes

Lifetime Supporter
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One of the few changes I made to mine after I got it on the road was related to a fuel smell. I had installed the fuel tank vents/roll over valves up by the fuel filler caps so that they would be hidden under the front clip. Under deceleration the fuel in the tanks would race forward in the tank and vent the vapor out the roll over valves under the front clip. The vapor collected in that area and seeped into the passenger compartment thru the gaps in the front of the doors. The more spirited I drove the car the worse the smell. I fixed it by taking the top caps off the rollover valves and drilling and taping (1/8 NPT) for a barb fitting then running a piece of neoprene fuel line from the barb fitting under the car into the rocker pannel area. The fuel smell went away.
You may want to take a look at where your fuel tanks are vented to see if you have a similar issue...............
Thanks for the advice. I did make some changes to the fuel venting some time ago, agree. When on the track the first time my eyes watered so bad from the amount of fuel fumes. I am assuming it is not the case today as fuel has a very specific odor. What I am left with after driving is head aches and exhaustion.

I'll keep working on it.
 

Alan Watkins

Lifetime Supporter
I have done a major reseal of the fire wall, including plugging holes and weather-stripping the rear body work.
Possibly peripheral to the current discussion but this reminds me of a diagnostic method I once saw on a TV DIY program. Here they were trying to find door or window leaks, so in a closed garage they turned on the car's heater blower to max, closed the doors and windows, and then walked around the car with a lit cigarette near the seams and openings looking for distrubances in the smoke trail.

OK, obviously this is where everyone runs for the fire extinguisher and the life insurance policy, so maybe there's a better smoke source than a cigarette, but the basic idea seemed useful as a way of finding cabin air leaks.
 
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