Ozz1967

iTrader: (4)

Hey guys,

I'm just curious. Carbed 355 here with CC Qjet. I know I need to install a wide-band 02 sensor in the Ypipe, down after both collectors join it so I can get an accurate reading on my A/F mixture, but what is the best way to tell if one side of the carb is running lean/rich? Would that be a narrow band 02 sensor in each header collector? Or am I way off and need to look in another direction? Just looking for some tuning help in this. Any help would be appreciated!

Sonix

iTrader: (1)

What would make you think one bank would be running rich or lean? Generally they'll be the same, and you don't have to worry about it.
You can measure the header temperatures with a temp gun, if one side is different, that'd be an indication.
The only thing I could think of that would cause this would be a vacuum leak on the intake manifold. I'd catagorize that as vacuum leak, rather than one side being lean. If you take that information to mean "one bank is lean" then you'll try to fix it via the carb, rather than actually finding the problem.

naf

iTrader: (7)

The dual plane manifold will have each side of the carb feed two cylinders in each bank. It's unlikely a pure carb problem will cause one bank to run lean. Some vacuum leaks may, however, affect one side more so than the other. Verify you don't have a leak in the accessory vacuum connection on the manifold behind the carb. You can also get crazy with the starter fluid around the manifold gaskets.

Dribbling water on the headers at each cylinder while it's warming up is supposed to be a method, but I've not mastered that trick.

Ozz1967

iTrader: (4)

I started thinking about it because I've burned up three #3 plug wires at the plug. It sits nestled down kind of cradled by the headers so I know it's getting a good bit of heat soak. Probably from running at high idle when the choke kicks on mostly. Anyway, they crack, turn white and flake off causing the plug wire to arc against the header manifold. I've picked up a set of them boot protectors, the nylon ones to see if this will cure the problem. If it doesn't, I'm going to be looking into one of those infared thermostats to see if any of the ports are running hotter than the other.

That said, all I really need is the wideband sensor down after the collectors merge into the one pipe to get a good A/F reading?

Orr89RocZ

iTrader: (20)

Those boot protectors rated to 1200+ deg F work very well My turbo headers/downpipe practically sit on the plugs and havent burned one yet. It reaches surface temps well in excess of 700 deg. It glows red sometimes

grumpyvette

http://www.professionalequipment.com...d-thermometer/

http://forum.grumpysperformance.com/...php?f=44&t=773

fireturd350

iTrader: (8)

I think FAST makes a kit that has dual wide bands and a hand held it's kinda pricey at $450+ for the kit.

The only reason I could really see for wanting to know each side on a street car that's NA would be dial in your idle mixture screws exactly instead of the normal 1/4 of turn then average them out. Most dyno shops I've seen only use one probe.

RyanEricW

Laser therm would be the cheapest way imho. Just be careful if you have a shiny metal, as the laser readings will NOT be accurate.

I heard something a few years ago in my performance classes that the numbers in 100's of degrees (exhaust gas directly) correlate to the air:fuel mixture ratio. Example, if your exhaust port gases out of cyl 8 is 1200deg Fahrenheit, then the ratio is 12:1. There was only one number that could have been either/or, and that MIGHT have been 17:1, where it could be too lean or too rich depending on the circumstances.

TBH if you want to get the most accurate readings, get exhaust gas temp sensors placed at every cylinder, and feed that back to a readout for hte most accurate readings. That could get expensive, but not as much as widebands in every socket...

The math/theory behind the EGT's is we all know that as the engine gets leaner, the exhaust gets hotter. The cooler, obviously more rich. The great thing about EGTs is they wont die or become inaccurate nearly as often as the expensive widebands, yet still give the same functionality.

Sonix

iTrader: (1)

This isn't true, although it's a widely held belief. The hottest your exhaust can be will be at stoich. Any leaner, and it'll cool down. Any richer, and it'll cool down. However, HP drops off faster when you lean it off, vs when you richen it up, so we generally tend to err on the side of rich of stoich.

Link for more reading;
http://www.sdsefi.com/techegt.htm


Ozz - I think measuring your AFR in each exhaust bank is a waste of time for your purposes. A temp gun is a good indicator, but I have a funny feeling your headers are all pretty close to the same temp (indicating a relatively similar AFR). I'm guessing your plug wires are just closer in that area. That happened to me too, uncoated headers tend to burn plug wires very often. Boot protectors should solve it, or you may be able to bend yourself a sheet metal protector (similar to the factories god-awful scotch lock setup).

Ozz1967

iTrader: (4)

I am starting to think this too because it's only one plug that keeps messing up. I picked up a set of these Jegs Sparkplug Boot Protector

They should be good for me. Only problem is, I am out of red sparkplug wires to swap, so I am going to have to swap all of them to this set of black plug wires (I really prefer red..) that I have. They are the MSD Streetfire, should be ok, though they aren't the higher-end ones I normally get. I just hope this fixes my problem.

RyanEricW

Thanks for the link, I will be forced to pull out the books to verify the information from years ago. I find it hard to believe that a guy who used it on his own dragcar, and also shown us in class was wrong. There's obviously something going on here. I'll post with an update once I get my books, as I'm more inclined to trust a professional school with credibility than a 3rd party performance source. If they are indeed wrong, I will be making some phone calls to the department of their curriculum =)

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Wow Oz, you paid $40 for those?

Apeiron

Still wouldn't be useful unless you had 180 degree headers.

naf

iTrader: (7)

A good heated O2 in the collector on one side will work just fine.