Delorean auto parts/ John Hervey hot air dam - How is it held into place?

[David T]

The fuel in the tank gets heated several ways. Ambient temperature, being pressurized and passed through the PPR, the coolant pipes pass right next to the tank. Finally the airflow off of the radiator and condenser. If you have a kinked hose or dirty pick-up filter in the tank and the level is low it is very easy for the fuel to vaporize. And now with all of the alcohol/methanol in modern fuel it is even more prone to vaporize. Anything you can do to reduce this is good to do. There does not seem to be any downside to using the "heat dam". A lot of cars have one and no one has ever reported any ill effects. If you notice problems when the car is very hot or a loud fuel pump a heat dam is a good idea but I would also recommend going inside the tank and inspecting everything to be sure everything is in good condition and properly installed. I also like a spring inside the pick-up hose. When it gets hot it gets soft and that fuel pump can pull a hard enough vacuum to collapse the hose, starving the pump and making it noisy. Once it gets noisy it starts wearing out prematurely.
David Teitelbaum

[Chris_Von_Bron]

hi guys,
I would like to create a hot air dam (as well as try and insulate my coolant pipes) to help reduce heat to the tank during the hotter weather.

Sourcing neoprene rubber isn't difficult. What I'm curious about is the thickness. Too thin and it won't be effective enough and too thick will make it hard to fit, secure and add more weight than necessary.

What do you think the optimal thickness would be (Hervey doesn't show the thickness on his site and emailing him 12 days ago with the goal of ordering resulted in no reply). The site wouldn't let me update my address/payment details due to errors which I mentioned in my email to him.

Thanks in advance
Chris

[SS Spoiler]

I made my own hot air dam with some bailer
belting from a farm store. I think it was about a
quarter inch thick. Also works great for under the
car skirting. Beings that it's rubber and flexible it
just bends going over bumps, and still looks good
after28 years of driving....

[DrJeff]

hi guys,
I would like to create a hot air dam (as well as try and insulate my coolant pipes) to help reduce heat to the tank during the hotter weather.

Sourcing neoprene rubber isn't difficult. What I'm curious about is the thickness. Too thin and it won't be effective enough and too thick will make it hard to fit, secure and add more weight than necessary.

What do you think the optimal thickness would be (Hervey doesn't show the thickness on his site and emailing him 12 days ago with the goal of ordering resulted in no reply). The site wouldn't let me update my address/payment details due to errors which I mentioned in my email to him.

Thanks in advance
Chris

Hi Chris,

I just measured a Harvey air dam I have sitting around. It is 7mm thick. It has a ply in the middle of the 7mm thickness.

Jeff

[Chris_Von_Bron]

Hi Chris,

I just measured a Harvey air dam I have sitting around. It is 7mm thick. It has a ply in the middle of the 7mm thickness.

Jeff

Thanks guys,
Very interesting how you're both within a few mm of each other, quarter of an inch (6.35mm) versus the 7mm thick Hervey version.

I wonder what folded/laminated material was used for the ply in the middle? I guess we'll never know, but it's interesting to note (if I'm understanding you correctly) that a total dam thickness of just 7mm overall is effective enough.

Cheers

Chris

[DCUK Martin]

If the job of this "dam" is to deflect air flow under the car rather than over the top of the chassis, then it doesn't matter what it's made of or how thick it is, so some light aluminium sheet would be my choice... if I thought it'd make any appreciable difference, which I'm afraid I still don't.

It's one of those things that seems logical - like boxing in of the lower arms. And it isn't a matter of opinion - in this case it needs testing.

The main coolant pipes, being aluminium, have an excellent heat transfer capability, and they live in an enclosed space with the tank sitting directly on top, constantly pumping heat at 80-something degrees into that space by conduction. It's like a pan sitting on a stove.

But yeah, the dam is unlikely to cause any harm

[Chris_Von_Bron]

http://dmctalk.org/showthread.php?37...of-1768/page25

The above has been handy to show that it is possible to insulate the coolant pipes. I imagine that the insulating properties of Neoprene wrapped around the coolant pipes that run below the tank would help reduce the heat transfer from the pipes to the tank.

I've expanded on this via the following new topic:-
http://dmctalk.org/showthread.php?16...319#post232319

I'm keen to explore as many areas as it takes to resolve this.

[DCUK Martin]

I imagine that the insulating properties of Neoprene wrapped around the coolant pipes that run below the tank would help reduce the heat transfer from the pipes to the tank.

You don't have to imagine, you can look it up. As an insulator, you want a low value for thermal conductivity.

neoprene*: 0.19W/mK

polyurethane foam of the type used to insulate household hot water pipes: About 0.02 W/mK

So about 10x better

And just for giggles, the conductivity air in the cavity without modification** is 0.03-0.04 W/mK

So in fact adding neoprene around your pipes would likely increase heat conduction to the tank over the air gap that's present originally..

*Wetsuits are made from neoprene foam, a value for the conductivity of which I can't find from a quick google search.

** This ignores convection which will improve this conductivity, but trying to model it gets very complex very fast. The point of a foam insulator is to trap air in a way that prevents convection currents.

[Chris_Von_Bron]

Great info Martin, thanks.
As the fuel tank plate hides the coolant pipes near the tank a household based material as mentioned would hopefully not perish as it wouldn’t be attacked by the elements. Is the tank held in place by the plate, I.e. when the plate is removed, will the tank fall or is it secured beyond being wedged in foam pads?

[FABombjoy]

polyurethane foam of the type used to insulate household hot water pipes: About 0.02 W/mK

In my experience this material works very well, even in the engine compartment (if kept away from direct exhaust heat). I used it in a few selective spots to loom and acoustically insulate, and on my AC hose & turbo water return hose as a "long-term temporary" anti-chafing measure.

One thing that adding a heat shield seemed to help with was my original steering rack. Before I had it rebuilt the steering would get sloppy as the car warmed up. I installed a very thick piece of polyurethane foam pipe insulation (probably 8cm outer diameter) on the rack body and onset of sloppiness was delayed. Usually enough to not be noticeable on shorter drives.