So I’ve noticed quite a few of the members here have removed the underhood fiberglass protective “layer”. I’d like to know if any of those members have seen any issues, as pertaining to paint stress or fading on the upper/outer surface of the hood.

I know that it serves a purpose, but could I do without it? I don’t daily my car, and when I do drive, it is only once or twice a week during the summer, and even less during the fall/winter. So extreme heat build up over an extended period of time is not a huge issue.

Anyway, I tried to run a search on this subject, but came up with pretty much nothing. So any help would be greatly appreciated.

Mike

 

been running without it for a while will no issues before I got my vented hood....

 

I've heard it's fine without it, but why take it off if you're is not damaged? Every vehicle has one, there has to be a good reason for it.

 

What is the main reason for removing it? Increased cooling air flow?

I would have thought that it was just there for noise damping for the engine compartment?

2 points that come to mind-

My E39 BMW runs a higher "normal" coolant temp than an FD. It is meant to run constantly at 108C to 110C celcius coolant temps. The radiant heat in the engine bay has not damaged any paint or plastics much.

My SP FD RX-7 race car has a carbon fiber hood (well, we call a "hood" a "bonnet" in Australia) and there is no insulation pad under that. The hood is painted gloss black, and the paint & carbon fiber survives fine? I think the only reason the race car does not have the insulation pad, is to help airflow under the bonnet, and to save weight. But I never questioned why we removed it. We just took it off...

 

I've seen a few FDs over the years that exhibited paint/clearcoat discoloring over the areas where the turbos are due to removing this piece. I'd recommend either sourcing one from Ray Crowe at Malloy Mazda, or look into some DEI thermal barrier material or something similar.

I'm pretty sure I've read somewhere that the OEM piece is designed to smother an engine fire in the case of such an event.

 

Do you want to remove it because it's causing a problem, or because you have nothing better to do?

 

This is what i heard aswell, i would of liked to kep mine but it was torn and could not be saved..

 

http://www.mvfri.org/Contracts/Final...Insulation.pdf

Ok, you're right. Dont remove it. According to this research PDF, in the event of an engine compartment fire, the plastic clips that hold the insulation mat to the underside of the hood are meant to melt, and the insulation mat will fall onto the burning engine bay and smother the fire out.

However, looking at how the strut tower brace in the FD is designed, the insulation mat sits firmly on top of it when the hood is shut. In the event of a fire, the FD insulation isnt going to drop anywhere. There's just no space between the closed hood and the engine for it to drop and smother anything much.

And if the insulation mat is flammable (just look at the flammability of the BMW X5 insulation mat in the tests in the PDF) then its going to assist an engine compartment fire, not smother it. There's no way of knowing unless someone has an old ratty FD insulation mat they want to throw on a bonfire in the name of science :p

Why am I so passionate about this? My 1970 Mopar suffered an engine compartment fire in April of this year (which spread to the interior), and caused over $10,000 worth of damage in 5-10 minutes, and nearly killed me in the process due to smoke inhalation. The car was heavily modified, but I never modified the positive battery cable (thought it looked okay) and it rubbed on the firewall and caused a dead short, and the Optima red top battery fed current into it, welding it to the firewall, and causing a massive wiring loom fire. I had isolated the electric fuel pump before jumping out (with the kill switch) but as the wiring loom heated, the wires fused and the pump got power back again, pumping raw fuel from the tank into the engine compartment, which made things worse. I hate car fires

 

Do not remove unless you want your paint to suffer over time. I've seen it first hand myself.

 

I find this reason kind of funny; how many FD's have been destroyed because of an engine fire? They all could not have had their insulation mat removed. Gasoline burns, the fuel usually leaks from under the UIM, the mat will not smother that.

That being said... Keep it, just in case....


John

 

i took mine off since it was old, dry and falling to pieces...no issues at all here

 

Run a search on "hood insulation" and you will turn up more than a few threads about it.

https://www.rx7club.com/showthread.p...ood+insulation

 

First off, there's no way in HELL this thing will smother an engine fire. Fires typically start under the upper intake manifold. There were engine fires on FD's back when they were still pretty new, that's why Mazda did the fuel line recall and everything. Back then they were all stock and had the hood insulation, it didn't do a damn thing.

I ran without one for a number of years (car didn't come with one) with no ill effects. But, it is quite possible if the car is running very hot that you can discolor paint. I'm not even truly sure how effective it is at insulating the hood from heat, a DEI reflective product would be FAR more effective.

If you're worried about engine compartment fires, do the RIGHT thing and get a fire extinguisher for your storage bin. Had a buddy with an FC this weekend who had a minor underhood fire (leaking oil feed line) and the fire grew and burned the ENTIRE interior of the car, blew out all the glass, car is a total loss. A fire extinguisher would have prevented that instead of standing on the side of the road, helpless, watching your car burn.

So, Dale's Wisdom here -

- Carry a fire extinguisher. I do.

- If you don't have a mat and are concerned with the paint on the hood, get some adhesive reflective barrier from DEI, stick it on the hood above the turbos, there ya go.

- The mat won't do a damn thing for an engine bay fire. Get a fire extinguisher.

- If you really want an OEM mat, they're pricey, like $150 or so.

Dale

 

I have to thank everyone for their responses, and yet I must apologize for not finding the other threads that were previously started on this subject…yeah I suck at searching.

Embarrassingly enough, I had only really wanted to remove it due to some rubbing on my turbo-to-intercooler pipe (polished). It has been leaving a smudge on the pipe, that although can be removed with polish, was still quite annoying. Furthermore, once I get my MS Strut bar back from the polisher I’d hate for this same smudging to ruin/mar its finish.

Yet from reading the responses, it seems that an aftermarket product would serve to benefit our engine bays, at least in terms of heat transfer. Quite possibly saving your paint in the long run as well.

I have not looked into what some of these vendors carry, but wonder if a product is available, such as Dynamat, where one could heat gun the material to almost form fit it to the hood and skeleton.

Multiple benefits:

Heat Transfer
Sound deadening
Extra rigidity to stock hood
Minimal clearance issues (pertaining to strut bars/pipes)

Hmmmm

Mike

 

Put some high temp tape on the undercover where it smudges your polished surfaces.

 

Another good reason to get a lightweight non-metal vented hood. Mine has a cutout right above the turbo area.

If it ever did catch fire, I'd know pretty much immediately from the smoke, and could try to get it under control just by using the extinguisher without opening the hood and just spraying through the vents.

The vented hood combined with all the other things I did like the ceramic coatings has REALLY cut down on the engine bay heat.

 

A vented hood (FEED) is on my purchase list, but it's way at the bottom with the rest of the body kit. So I have to work with what I have for now. Also a halon extinguisher is on the list; was just hoping for SBG to come out with their custom bracket. Hint hint!

Following Rich and Dale's advice, I took a gander at DEI's website and found what looks to be a pretty decent product. "Floor and Tunnel Shield II". Rated at withstanding 1750 degrees, it should be good for our purposes.

Think I'm gonna order a bit of this stuff and give it a shot. Just hope the contrast between the color of the product (silver) and my red hood look okay.

Mike

 

Lets think...Mazda had millions of dollars at their disposal when developing this car so they obviously had a reason for placing a "heat blanket" on the underside of the hood...on all 14,000+ cars that they imported.

 

Yes they had reasons, but not necessarily good ones. Precat comes to mind, EGR, etc etc.

Some things tend to be done just because it's on someone's checklist, good idea or not.

 

I haven't ran one for seven years and I've never had a problem with the paint.

 

The items you listed all have to do with emissions though, which Mazda obviously has no control over and must follow suite if they want to import into the US. Considering one of Mazda's top goals was to make the FD extremely light, the last thing they wanted was excessive material on the car.