Headers lit my wiring on fire! Too rich? (MSL attached)

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Headers lit my wiring on fire! Too rich? (MSL attached)

Postby mgmuscari » Wed Jul 11, 2012 8:52 pm

So I went out for a spirited drive today, with accel enrichment and EGO correction disabled to test out my VE table settings. I've got it idling around 1400 right now, because the idle gets suuuper lopey around 900 and I haven't quite worked out the idle settings to keep it from stalling out when the fan turns on or I load up the power steering pump. The car sounds great and pulls like crazy. Temps and oil pressure read fine while I'm driving, I'm not hearing any pinging, and in general it's starting to run really well.

Here's the problem: when I got home and pulled the car into the garage, I started seeing smoke from under the hood. I killed the engine and popped the hood and discovered that my wiring harness had melted and was on fire, which spread to my brake master cylinder. Luckily I keep an extinguisher in the garage and was able to put it out quickly... It looks like the driver's side header got so hot that it caused the wiring harness, a good 6-8 inches away, to melt. The plastic loom on the harness dripped onto the header and ignited.

I'm running 1 5/8" equal length shorty headers, but I never expected them to throw THIS much heat - can you guys take a look at my datalog and comment on my AFR's? We have E10 in NJ and I've been told that stoich should be 14.1:1. It seems to be right in the 13.8 range at idle, and the richest it went under acceleration was 11.8:1. There are a number of lean spikes correlated with throttle stabs due to accel enrichment being disabled. Is this too rich? Can too much timing cause this kind of heat? I advanced the timing a lot at low speeds to keep the engine from dying out under 900rpm. I don't think it's running with the timing retarded enough to dump the raw fuel into the headers, which I know can cause them to heat up at idle. I've heard too rich OR too lean can cause overheated headers. Am I good with the mixture, or should I lean it out? How much?
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Re: Headers lit my wiring on fire! Too rich? (MSL attached)

Postby V6 SPL311 » Thu Jul 12, 2012 8:10 pm

I don't think it's related, but your WUE never shuts off. I think it would wreak havoc on your attempts at tuning. Seems the norm is to have the WUE shut down about 20 degrees before the thermostat opens. Your coolant temps hovering ~200 degrees certainly isn't helping underhood temps. I remember breaking in a cam one evening on a SBC and after the 20 mins at 2000 RPM, the headers were literally glowing from the heat. Perhaps a spirited drive and a quick shot with a laser temp gauge might lend a clue as to header temps?

Just throwing some things out there until someone with more experience than me drops in.

Hope it helped a bit.
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Re: Headers lit my wiring on fire! Too rich? (MSL attached)

Postby pit_celica » Sat Jul 14, 2012 6:04 am

Usually, high EGT come from a overly retarded ignition timing.

I would suggest adding 2-3 degree of timing everywhere (watch for knock in high RPM/load condition).

One thing that I want to say is that you've set your AFR table a little too rich under cruise area at 14.1 AFR. I know you are using E10 fuel (as most of us), but you need to know that your wideband is reading in lambda terms and than convert it to AFR. By default, your wideband is calibrated to read 1.0 lambda and display it as 14.7 AFR. So, even if the fuel stochiometry is 14.1 as you pointed out, it still mean 1.0 lambda. So, this is really a 14.7 AFR in your wideband display. So is what's displayed in TS.

So, I suggest you to use a more common AFR table based on the usual 14.7 AFR stochiometric. Because, at cruise and idle, if you're not at stochiometric, you're simply wasting fuel and making more pollution for nothing.

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Re: Headers lit my wiring on fire! Too rich? (MSL attached)

Postby Lapkritis » Sun Jul 15, 2012 8:13 am

Header-Wrap or get some heat shielding for components under the hood would be a step I take alongside adjusting the tune. All kinds of things under the hood aren't intended for increased heat from aftermarket setups.
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Re: Headers lit my wiring on fire! Too rich? (MSL attached)

Postby mgmuscari » Sat Jul 21, 2012 12:10 am

All great suggestions - I haven't had a chance to get down into the garage to rewire that side of the engine and replace the master cylinder yet, been too busy with work.

Good point about the WUE, coolant temps are varying by 10-15F as I drive around. It's been really, really hot here lately (over 100F during the day) which hasn't helped with that. I've got a 190F tstat in the engine. I wonder if I should try running a cooler tstat... I'm a bit worried that lower coolant temp will lead to worse emissions. Then again, replacing the tstat isn't exactly brain surgery.

With respect to engine timing - I actually couldn't get the thing to rev past 2k before I set it up with its current timing. I pulled 4 degrees off, and lo and behold it revs all the way up to 6k all day long with no complaints. I think I actually had too much timing on it before... even though I didn't hear any knocking. The tank is full of high test, and I guess it's running super rich, so that may be why...

I actually did realize the other day that my WB controller would be sending the same signal for E10 at 14.1 as it would for gasoline at 14.7, and that the MS firmware expects lambda = 1.0 to be stoich... I'll be switching this back. I originally had it set that way and richened the AFR tables when I remembered that we have E10. Not like it actually matters a whole lot though with EGO correction turned off. Before the next time I go out, I plan to go over my current datalogs, adjust the VE table to get the mixture as close as I can through calculations, and try to set up EGO and EAE so that driving will be a little easier. So the AFR tables will have to be reset before then...

I don't have a laser temp gauge but I guess I should probably bite the bullet and get one. I'm hoping that my work will let up soon so that I can spend some time working on the car again. I haven't even cleaned the fire retardant out of the engine compartment yet :|

I have some header wrap sitting in the corner that I didn't want to use because these are nice chrome headers. Oh well, I guess I'll go ahead and put it on... I also plan to re-wrap the whole wiring harness with heatshield loom. The black plastic loom from pep boys / advance / whatever is garbage - I wouldn't have to rewire this thing if it weren't for that stuff melting.
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