Enzo/P 4/5 coil heat shields

We actually had this same problem with our Formula SAE car. The heat shield wasn't actually protecting the plug wires and they were beginning to melt. We ended up redesigning the car for this year to allow for a bit more space to run the wires further away and threw in an extra sheet of insulation. I'm assuming that you will go with a design that is less thrown together tho.

 

Ask yourself what kind of heat transfer is killing your coils?

Convection - hot air rising up to the coils and heating them up

Conduction - the fact that they are in physical contact with the hot engine is heating them up

and/or

Radiation - Infra-red heat radiation from the exhaust is heating them up?



Each form has its own solutions:

Convection - Just make sure that the hot air will not get there. Shields mostly need to be air-tight between heat source and heat victim

Conduction - Insulating the coils with a rubber or phenolic pad or something from the hot metal may help there

Radiation (the most likely villan): infra-red is just very red light. The more shiny your heat shields, the better they reflect this light. You don't need fibre material in these shields, nor do they need to be heavy. They just need to be highly reflective, and may be mere microns thick to do that job.


Or maybe the heat originates in the coils themselves? You are pushing a lot of amps through them, and the more revs you make, the hotter they're likely to get. Shielding them from (potentially cool) surrounding air may make things worse, rather than better. How about blowing some cool air over them with a small fan?


Not having a P4/5, nor an Enzo at my disposal, I can't comment more than above generic observations. Hope it's of some use...

Good luck!

Hans

 

How about the Gold Heat Reflective Racing Film used on race cars ?

http://www.hrpworld.com/index.cfm?form_prod_id=310_5325&action=product

Jim

 

This company produces heat shields for race cars and has material property data lists on their website.
http://www.aerotecheng.com/
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Are those just simple snap-fasteners?

Your re-design looks pretty similar to the originals.

 

Stopping the radiant heat from getting to the coils is good, but if you are trying to control the temperatures you need to take away the heat generated by the coils in addition to the heat coming from the nearby hot parts.

If you just insulate, no matter how well, everything it will, eventually, all get hot since the coils are generating heat too and it has no where to go. No idea how much air is passing around in the engine compartment to help take the heat away, but you need to direct some air between the heat sheilds and the coils if you want to control the temperature of the coils.

Tightly wrapping the coils is a bad idea, so what you want to do is try to prevent the direct radiation from "seeing" the coils (that is, try not to have a direct line of sight between the manifold and the coils) and then try to keep an air gap between the coils and the insulation sheild. That way air can pass between the coils and the shield and take heat away from the coils as well as making the heat shield much more effective.

Also look at where the air is coming from that will be around the coils. You don't want the air from directly around the manifold to be acting like a convection oven and rising up over the coils.

Pic of the general area would help....

Good luck.

 

Really odd, my P4/5 does not have this issue

-dsd

 

Ours are of a newer spec.

 

Yes, easier to see now...

Still, one basic rule still applies. If you tightly wrap the wires you don't get as much protection to the wires as if you wrap more loosely and let free air circulate between the wires and the shields. Not sure why the shields degraded so much, I would have expected a typical stainless covering to have not fallen apart.

One other option is to wrap the headers over that gap where they are close to the wires. That will greatly reduce the heat that the outside of the shields see.

 

Go to the source... wrap the headers. Granted it won't be as pretty but it will eliminate your issue. If you don't want to do that you need a heat shield for the headers as well. Doing both is the optimal solution along with your new wire heat shield.

 

You mean you will keep an eye on it next time P4/5 is doing many hot laps on a full F1 circuit with track temps at 110f? Will probably not be today or tomorrow that these conditions will recur

Interesting comments from posters about heat. Learned a lot

 

Suspect that is the answer. I am a big fan of header wrap

 

There are a number of ceramic header coatings out there, some have low conductivity (surface stays cooler but still radiates heat), some have low emissivity (don't radiate as much heat but the surface stays hot), and others are primarily there for corrosion prevention. Not sure what kind of coating is on yours and you really can't tell by looking.

If you have a lot of air going past a low conductivity coating may work the best. While wrap works, it is ugly, gets full of junk and generally looks crappy over time. NASA has developed a low conductivity (so called "Low K" or "half K" thermal barrier coatings that we are using on turbine engines. These coatings are used on turbine combustors and have essentially half the conductivity of more conventional yttria based zirconia coatings. If you have a good bit of flow around the headers a coating like this might get you a big drop in surface temperature. Here is a NASA presentation on the material...

http://gltrs.grc.nasa.gov/reports/2005/TM-2005-213857.pdf

Another approach would be to make custom sleeves that were made of very thin stainless sheet with an internal layer of ceramic insulation. I used to know a supplier that would make them up for custom installations such as this but I can't seem to find their card in my stack of stuff..