Question for you EFI guys...I installed EFI out a 1988 T-bird back around 1993 in my '77 Mav. I am in the process of removing everything and rebuilding it in my '72 Grabber(The '77 has seen one too many Michigan winter...and the '72 spent it's whole life in Alabama away from the salt......). I am curious how others have dealt with the O2 sensors...or do you run them at all? At the time, I drilled a hole in each exhaust pipe as close to the manifold as possible and welded in a "bung"..I am thinking about going this route again. Thanks for any input!
Yeah, using the bung is the only way to put the o2's in. It is best to put them as close to the engine as possible, but still have them being hit by every cylinder (i.e. in the collector on headers). I would highly advise against not using them, they are the primary sensor the computer uses to determine a/f ratio (second is the MAF sensor, don't know if you have one or not).
No, I don't have a MAF, this is the older Speed Density system. I know that GM computers can run in what is known as an "open loop" state with out the O2 sensors, where there are default settings that are used instead of the feedback provided by the sensors...but I am not even sure that Ford computers operate the same way. The more I think about it...there really is no other way than to weld in the bung...even with stock manifolds, they are basically unique to the Mav, so manifolds that accept an o2 sensor probably would not fit...
Yes Ford computers work the same way. Having ox sensors go bad is not a reason to shut the engine down. The system will run with out them but you really should use them for fuel milage and general drivability.
Actually, you really don't want the 02 sensors as close to the manifold as possible. They will get too hot a prematurely fail. They ideally should be about 30" from the cylinder head exhaust ports. If you're going to use headers, the bung should be welded in at the collector centered between two of the exhaust tubes. Hope this helps.
GS, I hope you will accept this respectfully. The oxygen sensors as used in the Ford system must operate at 650 degrees min. and Ford specifies the location to be ideally close to 15 inches from the nearest exhaust ports as evidenced by their location on stock engines at the manifold outlet or just a short way down the head pipes and is Ford references.. From about 93 up, the computer processor speed was increased to the point where the processor can correct the air/fuel ratio change on one cylinder between firings therefore the distance the sensors are located in the pipes become somewhat important so the change can be made that fast. Putting the sensor to far away especially in long tube headers can cause a delay in heating and responce time due to the cooling area that exists on the exhaust gases. The sensor heater that is built in is not for the purpose of making them operate properly but to help bring them up to operating temperature faster at cold start. The amount of power they draw for heating is not nearly enough to completely heat to operating level of 650. I have already run them in long tube headers with poor results in a large diameter, very efficient system. The system was changed over to shorty headers with the sensors added just below the header outlets. I understand there are some who think their systems are working fine in long tubes but suspect they are not awhere that they could work alot better. Iv'e done a lot of research by putting insulation on the collectors and found an imediate improvment but was not the total answer. I even built a pair in internal collector restrictors placed behind the sensors to back up the heat effect and that also made improvment but the problem was still always a 'cool down" at a light or a stop sign.
This is interesting. I have long tube Jet-Hot coated headers. I'm in the process of installing an O2 sensor, not for EFI, but just so I can run an A/F ratio gauge to keep tabs on the carb's state of tune. Some people I've talked to feel the ceramic coating will maintain enough latent heat in the header to "light off" the sensor and others aren't so sure. Guess we'll find out!
You will get the same kind of heating delay for you monitor gauge, just that it is not controlling the EFI system so there is no effect on how the engine runs. The gauge will seen to be most useful under complete hot running and WOT. On my early EFI exhaust, the engine would tend to dog from a stop then at about a 100 feet it would light up and fly. Doing the insulation testing changed that time interval. I run an Auto meter 270 degree dial A/F gauge sampling the right bank. During the cold start and warm up, first the gauge indicates total lean because it is not being used by the FI system due to the ECT, ACT sensors controlling the fuel injected. Then as the oxyen sensors come up to operating temperature they will see the rich cold injection that is being applied by going 1 or 2 lites into the green. When the engine is up to full operating temperature, the A/F gauge will fall back into the yellow and cycle from off to red to yellow as the system begins to be controlled by the sensors and the gauge continues to show the tracking of oxygen content in the exhaust gas. This kind of action is the parallel to the correct operation of an automatic choke on a carb. On a sudden application of about 7/8 throttle or more the gauge will register 1 to 3 bars into the green rich area as one would want to see it do. This action is the parallel to the acelerator pump on a carb. The Computer tracks the 'rate' of change of the throttle (tps) and applies a richer fuel supply. Nearly all oxygen sensors used to control fuel injection are calibrated to cross over at a 14.7 ratio, so there are limits to how far above or below that center ratio, the gage will be accurate becaue the output of the sensor flattens out at the exremes above and below but they are still quite useful for tuning and trouble shooting.
No offense taken K. Merring. Your theory is interesting & probably more accurrate than my source. My source is from Advanced Engineering West, which does alot of R & D work for Ford, but that isn't to say what he has told me is gosbel either. Although I do respect most things that he has past onto me. That probably explains the slight hesitation that I have at mid warm-up. The car runs very well cold & at operating temperature, but has this hesitation in between those warmup modes. It also depends on where you take your measurement from to come to the 30", but my girlfriend's 89 5.0 is exactly 26" from the front exhaust port to the 02 sensor. The 02 sensors are placed at the bottem of of the pipe, just in front of the transmission. I also have an 85 5.0 & the 02 sensors are much closer to the head than the 89. My headers on my Maverick are aluminized & thermal rapped, but I'm unsure how much this corrects or effects the 02 sensors.
Just some food for thought....On the turbo mav, the Ox sensor is located 2" downstream of the turbo, a total of 12" from the nearest exhaust port. It cools down during long periods of idling, like sitting at a stoplight for more than 3-4 minutes. Also, they're not absolutely necessary to use in a MAP style EFI, but the engine will run much cleaner with them installed. Basically, if you leave them out, it will run in open loop mode, just like the engine is cold (Ford ECU's don't use the O2 until the engine warms up to operating temp) and the mileage will suffer. It also doesn't use the O2's during wide-open throttle operation. As far as using one for a tuning aid, in my application it's very hard to watch a voltmeter while accelerating. Trying to keep the car straight and watching a meter is downright scary even on the freeway. Even when I can use it as a tuning aid, it's not totally accurate...they only get you in the ballpark. Good luck
The reason i said that it is important to get it "as close as possible" to the point where all the exhaust exits on each side is because i have had several friends who had problems with their fuel injection because the oxygen sensor sat too far back in the exhaust to be heated adequately, and therefore never reached operating temperature. Many of my sources have said that with a long-tube header, the o2 should be in the collector. With the o2 not hot enough and the computer running in open-loop mode, you will not only lose gas mileage but also performance...as the computer intentionally runs it too rich in open-loop to prevent detonation...thus defeating the point of fuel injecting a mav in the first place!
Wouldn't that kick the check engine light on? It's my understanding that it will & I haven't had my check engine light come as of yet. I installed & wired a fully functional check engine light with my EFI conversion.
Oh boy, now there's something i miss not having on my maverick...a check engine light! Gosh i love those things! Only kidding (i know, they're a necessary evil). Anyways, I don't know for sure if that would cause a check engine light or not. For that matter, all mustangs that are fuel-injected will use HO2's, heated oxygen sensors (don't know if you used heated o2's in yours or not...anything with three or more wires is heated). That way they heat up faster (regardless of placement in exhaust) and are less prone to cooling. If it hasn't caused a check engine light yet, it probably won't. If you get a code indicating a slow response from an o2 then you know what to do!
Yes, I'm using the 3 wire 02 sensors as all 89 5.0 Mustangs did. I utilized the seat belt light in the dash for the check engine light. The seatbelt light always bugged me anyway & was useless as far as I was concerned. So, although bothersome, the check engine light is definitely more useful.
