Oxygen Sensor

[gastonleg]

Folks,

I have a 351 Winsor with four into four FFR headers, and an MSD EZ EFI setup. Where should I install the oxygen sensor?

Thanks in advance.

[Blue MK3]

A dilemma, for sure. Ideally, the sensor should be after the pipes collect, which places it just ahead of the muffler out for the world to see and/or catch on your pants. No room to position it inward toward the body and anything below horizontal (9am and 3pm) is considered a no-no. Placing it in the engine compartment out of sight means only one cylinder is monitored. This is why I replaced a faulty Holley carb with a QF. I considered one of the aftermarket throttle body EFI units, but passed on the idea. I'll be interested to see what others might suggest.

[gastonleg]

Thanks for the quick reply. Sounds like this is not an easy issue to resolve - I understand it's not ideal to only monitor one cylinder but lacking any other option what are the drawbacks?

[Olli]

There is always the option of going with Stainless Headers double merge collector headers. The O2 bung will be in the middle of the merge which will at least give you a sampling of 4 cylinders. Consider getting the caterpillar mock-up header. Adjust the caterpillar for perfect side pipe alignment, return the mock-up and they make your headers. That is what I did. In fact, I just received the shipping notification that my double merge collector headers shipped today.

http://stainless.eclipticcms.com/ima...0LH%20Side.JPG

Olli

[gastonleg]

this is perfect! thanks.

[Blue MK3]

The MSD unit is the one I would choose if you can believe the manufacturers' claims of quick, simple, painless installation and operation, etc. But read through this and the other forum and I think you'll find that aftermarket EFI systems aren't always as simple as they are portrayed in the advertising videos. I like the MSD unit's look, return-less fuel system, and handheld setup control unit. As for location of an O2 sensor, Olli's suggestion seems like a good solution. One side only, as the MSD (and all the others) appear to come with only one sensor. So the best you can do is to monitor only half the engine. I think the MSD retails for ~$2500. then there's the cost of the double merge header ($500?) Total of probably more than $3k.

This response may sound like I'm trying to talk you out of going the EFI route; I'm not. I'd probably have the MSD on my car if the cost wasn't so great. It sounds like you already have the MSD, but is it on the engine? I would think not if you don't have the O2 sensor installed. But with a QF 650 on my car (347 stroker, 450 hp, 4.11 rear), I get great startability, instant return to idle, drive away easily after buckling up, and about 18 mpg at interstate speeds. Cost was less than $700. Granted, I live at sea level, don't climb to 10,000 ft, and drive only in moderate weather.

So ask yourself if the extra $2500 you'll spend for EFI is worth it. Just my thoughts. Have fun.

[skullandbones]

Hi Blue MK3,

I anxed over this for a long time but when it came time to install them, I put them at the most logical position with the given limitations. It's not perfect but it does work and it does not expose the sensors too much unless you are running through brush or very uneven terrain. My 4 tubes on the curve of the side pipes is about at the same level from the ground. I did mount mine at about 4 and 8 o'clock. There may be some concerns about the sensor collecting water or exhaust debris but I have taken mine out and cleaned and inspected them. They look about the same as when I first installed them. The sensor is not sensitive to the orientation. That I know. The readings are limited to a very narrow band so the computer gets a message that the mixture is "lean" or "rich" or "perfect". When I install a wide band O2 gauge, I'm thinking of recessing it into one of the collectors about 1.5 inches to get the sensor right in the center. I still like the location better than having it in one tube of the header. The special headers are a great idea but pricey. I have a pic of the way mine is installed.

Good luck,

WEK.

[CraigS]

Put it in one of the tubes. That's where we welded Bill3422's bung for his efi and it is working fine. Massflo said they want it close (within 15? or 18? inches) to the engine and current street cars have them as close to the head as they can physically get them.

[Blue MK3]

WEK, that's the only location I could come up with for the sensor, given the exhaust system on my car. But I worried that it was too far below horizontal. I guess you disproved that concern. You can't argue with success.

You mentioned mounting "them" when referring to the sensor(s). What EFI system are you using? I have not seen an aftermarket EFI that includes and uses two sensors.

[skullandbones]

This is a stock Mustang PCM but I have a Summit EFI harness that still uses the two O2 sensors like on the Mustang. I had to extend them a little. When I go to the aftermarket PCM, I will do what I mentioned above and only use one side of the exhaust as the wide ban monitor. I think I will try it on both sides to see if there is an measurable difference. I've only seen one wide band O2 that used two sensors and it was very pricey. The vendor for the aftermarket PCM says it is not necessary. I've also heard that the one tube bung closer to the engine works fine as Craig S suggests so I don't know how important this reading is anyway without a wide band sensor. One guy I talked with said you could go without them (O2 sensors) but I didn't have enough nerve to go that route. Good luck, WEK.

[Blue MK3]

I was thinking along the lines of a total package from one of the EFI aftermarket companies that just bolt on and wire up, not a combination of different systems as you seem to describe. Heck, I don't even know what a PCM is.

[skullandbones]

Sorry! PCM=Powertrain Control Module aka computer. On the Mustang it is a metal box about 8x8x2 inches. You have to have a engine harness to connect from the PCM to all the engine management sensors. I chose to use the Summit one because it is so simple and brand new. It is basically a stand alone harness except for about 4 wires. I also have a body harness that was made by American Auto Wiring which used to be the vendor instead of Ron Francis's harness. They are similar. You would have to have an engine harness with any EFI system you put in. I guess each after market EFI system has their own version. The one I plan on going to when I raise the coin is one that will plug into the existing 60 pin connector of my stock Mustang PCM. That is about as clean as it gets (plug and play). Now back to the regularly scheduled program: O2 sensor location. WEK.

[Blue MK3]

And now we return to our regularly scheduled program. WEK, if your O2 sensor location in a 4 into 4 system works, I'd suggest the OP dispense with the idea of the expensive double merge headers and do what you did. Save $ and system alignment problems. I may do the same in the future.

Two items, off topic. Looks like you are missing a bolt from your exhaust hanger. And you mentioned no problems unless driving through debris, etc. I looked at my exhaust and hanger today and noted SOMETHING stuck on the hanger. I pulled it off; don't know what it is (was). Maybe a toad or a ????? It didn't smell, though. It was very dry.

BTW, have you found that famous mine in the Superstitions?