The situation is that with my M50 swap (e30), I'm using a header off ebay as many do. The header is split into banks of three, that come down into twin pipes (and then a collector aft of the transmisison). Anyhow, each "set" has its own 02 bung (with caps). Since I'm using an OBD1 M50, it only has one 02 sensor.
So obviously I can weld a bung in downstream past the collector and before the cat. This isn't hard to do, but this being a stage rally car that puts the sensor and wiring in a pretty vulnerable position to getting damaged by large rocks and stuff (even oriented fairly upward, we take a lot of exhaust hits).
Other option would be to run it in one of the two header "banks." Since assuming the car is running correctly, the A/F mixture in both "banks" of cylinders should be the same as each other (and the same as post-merge), correct? So is there any downside to just popping the sensor into one of them and running it off 3 cylinders?
Do it. I see early Toyotas like that. I'd have to look, but I think the O2 sensor in my Doug Thorley header on the 22R Truck is just in one runner, or 2 at the most after they come together.
I think three cylinders will be fine, if putting the sensor in the collector puts it in harm's way.
In your circumstance one bank is the preferable option. I have experienced 02 sensor failure due to road strike. You do not want to!
maj75
HalfDork
3/11/19 10:04 p.m.
Don’t do it. If you have a bad coil or coils in one bank, your O2 sensor won’t “see” it. You can weld a bung in the Y pipe and tuck it up where it will be relatively protected, i.e. not the lowest point of the car.
It's dumb but as far as I can tell that's how my '87 GTA was setup normally. The headers thet came with the car only have an o2 bung in the driver side collector. Nothing on the y-pipe. My 2000 Dodge truck was setup with dual exhaust with no crossover and both the up and downstream o2s it would have had were on the right bank.
maj75
HalfDork
3/11/19 10:17 p.m.
Daylan C said:
It's dumb but as far as I can tell that's how my '87 GTA was setup normally. The headers thet came with the car only have an o2 bung in the driver side collector. Nothing on the y-pipe. My 2000 Dodge truck was setup with dual exhaust with no crossover and both the up and downstream o2s it would have had were on the right bank.
‘87 GM fuel management < BMW M50 fuel management ;)
In reply to maj75 :
I agree, thats why my 87 gta is bumping up to 2000s GM fuel management.
maj75 said:
Don’t do it. If you have a bad coil or coils in one bank, your O2 sensor won’t “see” it. You can weld a bung in the Y pipe and tuck it up where it will be relatively protected, i.e. not the lowest point of the car.
I mean, I would assume I'd notice a misfire if that is the case. I don't have any stock gauges so it's not like I'll get a SES light or anything. So even if a coil goes bad, i'd have to use the under-hood diagnostic port to check it.
Nothing is "protected" on the bottom of a rally car. Just ask my old oil pan, my 12 gallon gas tank that only holds 10 gallons now, my passenger floor, and my old exhaust, which looks like it's right out of world war 3.
Still wil look into putting it downstream, but looking for other options.
maj75 said:
Daylan C said:
It's dumb but as far as I can tell that's how my '87 GTA was setup normally. The headers thet came with the car only have an o2 bung in the driver side collector. Nothing on the y-pipe. My 2000 Dodge truck was setup with dual exhaust with no crossover and both the up and downstream o2s it would have had were on the right bank.
‘87 GM fuel management < BMW M50 fuel management ;)
clearly you've never had a K-Jet BMW lol....
I will say, mine is at least TPI and not TBI. Of course the hardware is pretty much the same other than the intake and injectors themselves. Now there's a '79 Datsun with an L28E in this shop too if we want to talk about archaic EFI. I think that one's L-Jet. Has a mass air meter that's actually a meter. I know that much.
Daylan C said:
I will say, mine is at least TPI and not TBI. Of course the hardware is pretty much the same other than the intake and injectors themselves. Now there's a '79 Datsun with an L28E in this shop too if we want to talk about archaic EFI. I think that one's L-Jet. Has a mass air meter that's actually a meter. I know that much.
anything is better than Renix. I still have nightmares about my XJ with that awful system.
If you damage the 02 sensor under the car, especially if it shorts the heater to the sensing wire, your problems are far worse than a miss fire. Keep it up and protected. I damaged my then DD Volvo 240 on an ice chunk, and suddenly it would only idle, or run above 4000 rpm. I am surprised it did not seem to damage the computer. LH jetronic with hot wire MAF. I must laugh at Daylan calling a Datsun with L jet old. Look at Djet for old
.
In reply to irish44j :
Oh yes. Glad my XJ was a '96.
It'll work fine on one bank. And actually, not seeing a misfire on the other bank is good. It means that if you end up with a miss, you've got a 50/50 shot of it being on the non-O2 bank and correspondingly not forcing the engine to run super-rich. A misfire dumps lot of extra O2 into the exhaust, so the sensor will read super lean and make the engine rich to compensate.
Only thing to note is that if the fuel rails are plumbed in a way where one bank is more likely to go slightly lean under heavy load, that's the bank that should get the sensor (erring a little rich is better).
rslifkin said:
It'll work fine on one bank. And actually, not seeing a misfire on the other bank is good. It means that if you end up with a miss, you've got a 50/50 shot of it being on the non-O2 bank and correspondingly not forcing the engine to run super-rich. A misfire dumps lot of extra O2 into the exhaust, so the sensor will read super lean and make the engine rich to compensate.
Only thing to note is that if the fuel rails are plumbed in a way where one bank is more likely to go slightly lean under heavy load, that's the bank that should get the sensor (erring a little rich is better).
I wonder how one would figure that out...
May be moot - if I do a single bank, it'll have to be the front bank, since that's the only one of the two 02 ports I can actually access with these headers stuck in a car they're not meant for, lol.
IDK, I'm going to start assembling exhaust and then see what I can do about protecting the 02 somewhere in the main pipe, and then go from there.
