Alan

Some of you may recall I added a Halon extinguisher and an engine compartment remote deployment system a while back.

At the time I mentioned I thought a fire detection system would be useful because its hard to know initially you are on fire until it gets bad enough to affect the engine running or belches out enough smoke to be visible. A lot of damage can occur in that time and it increases the risk you will have to take last minute evasive action to get off the road...

So I plan to develop an early detection system for my car.

So some questions:

1. Has anyone measured engine temperature while running? around the top end - cam covers/ intake area? What is the normal peak temp?

2. For those that have experienced engine fires - where was most of the damage - I assume cam cover/intake areas next to the fuel rails - how about the open area right behind the fans and in front of the engine - presumably this is a major oxygen source but less fuel risk there?

I'm contemplating adding about 6 temp sensors (335 degree trigger NC thermal switches in series) just above each fuel rail and possibly at the front each side of the oil filler. Other thoughts on locations? etc. I'm assuming normal temps are right around 200F - maybe spiking up to 250F max - but I have made no measurements yet - has anyone else?

Other fire sources ? of course Cats but beyond that?

Alan

SharkSkin

You might want to stick a thermocouple in one or more of your intended locations, e.g. above the cam cover where heat from the exhaust will collect. Then, on a real hot day, disconnect the temp sensor on the intake(to simulate failure of that sensor) drive it hard to get it heat soaked then shut it down & park in the sun. Under these conditions you may find that 335 degrees is cutting it close. Wiring an IR smoke detector near the cowl ANDed with the temp sensors might give you an added degree of safety from false triggers.

Worst case, a false trigger might freeze some rubber parts, or worse yet leave you unprotected for a REAL emergency.

Shane

Charcoal canister, and around the fuel tank.

The charcoal canister burns like you wouldn't believe.

The area between the firewall and windscreen where the blower motor/wiper motor sits burns pretty damn good too.

j.kenzie@sbcglobal.net

Alan,
I have a Polder oven/roast thermometer with a probe on a 36" lead. It reads to 450F. You could zip tie the probe wherever you want and hook up the display for reading. Cost about $25. This could help you establish a maximum normal temp as Dave A. suggests.

Alan

Dave (and Dave),
I have no problem sourcing really hot days... even now. I do have thermocouple for my DMM but have not done any measurements yet. If 335F is not a sufficient safety margin - I'd just use a higher threshold switch set but if no falsing lower is better for a faster response. I'm thinking 335F will be OK. I want to keep it simple and reliable all sensor switches in series so any one triggers and wiring destruction or disconnection counts as a detect also... I may consider a dual level sensor system with 2 detection levels (say a 385F set) - adds some reassurance - if only one goes off its suspect - if both trigger in sequence its pretty darned real.... But yes an unneeded deployment is a $70 halon refil and bang goes the ozone layer too (yes we are talking real Halon - it just works the best) so no false alarms!

Shane did the bulkhead area & Charcoal canister go up on their own or just as collateral damage to an engine fire? Don't see a lot of combustion initiation sources there? On my GTS the LP AC connector is behind the bulkhead there - so maybe I will add detection there...

BUT my halon deployment assumes that area is safe and routes the injection jet tubing there... I think that is probably still a pretty good bet overall.

Alan

SharkSkin

As I recall the setup you built -- I suppose false alarms would be OK, since they would not trigger the release of the halon. You just want some kind of audio/visual indicator, right?

BTW I think Shane is talking of his experience when his fuel line let go. I'd be really surprised if a fire started in the cowl area. Maybe if you had flammable refrigerant and managed a spark in there somehow.... otherwise, not a significant risk.

worf928

Alan, PM Louie Ott. IIRC he did some extensive investigation and data logging on underhood temps several years ago.

Alan

Dave(C) - thanks I will... (lots of daves.. tonight).

Dave(A) yes this is for visual indication only deployment is still manual only - wouldn't have it any other way.. I'm thinking a dual color LED indicator amber & red maybe...

BTW I did get the new B-K quick release mount for the halon extinguisher - very cool but pricey and I had to totally reinvent my seat mounting and actually even needed to swap my halon extinguisher for a smaller Amerex bottle - nicer install when done and now I have Halon in both cars!

Alan

heinrich

Alan may I recommend a sensor at the rear of the engine at the cat? As the car drives, air is forced from the top of the engine through the engine, down toward the road and back of the car. Hot air escapes where Vettes normally have their legpipes.

Alan

H Ha! Yes but I'm quite OK with those kind of little fires & explosions

I'm only worrying about the ones that shoot hot air and flames unexpectedly under the hood. Besides I already know my Cats will get well hotter than 335F.... no need to douse the engine in halon every time that happens....

Alan

heinrich

Actually I was quite serious Alan. Put a flare into your engine bay and drive .... you'll see what i mean

Alan

H The problem with trying to detect temperature there is that its just too darned hot anyway around the exhaust - esp when stopped at idle after a good run - a smoke detection system there might work - but that is not so simple or reliable to implement... Maybe the back of the engine somewhere under the MAF could be a spot feasible to investigate....

Alan

SharkSkin

That BK mount is a sweet looking piece of hardware. Got any pics of the mounting face, where it bolts to whatever mounting surface you use? I'm curious if it would fit the intermediate bracket I'm using.

Alan

Dave,
Here is what I did - you could use your existing mount (nice!) - you'd be 90 degrees different - my release arm is underneath - yours would end up in front... just as good - maybe better - I wanted it hidden...

Alan

SharkSkin

Nice setup, Alan... Do you have the bolt pattern & outer plate dimensions?