When I get my car dyno'd I was planning on removing the O2 sensor and using that bung to take the A/F reading. I know at WOT the engine ignores the O2 sensor so I'm thinking I should be alright. Any other suggestions? Perhaps I should ground my O2 sensor? I can get a test pipe with a bung for the O2 sensor but then I'd be dynoing without my cat.

Thanks,

Steve

Does the shop have a long probe they can stick up the muffler/exhaust pipe? I think if you test after the cat the numbers might be off a bit though? This is the setup the shop near me has at least...

Just weld a O2 bung in before the cat.

I like Steve's idea best, but you could also make a test pipe just for tuning, with a bung in it. Also useful for track days, but you'd have to plug either one. Hmm...

The O2 bung comes with a plug and you just use some ti-anti sieze. Also, the bung should be easy and cheap to do. Drill the hole yourself and then have the bung welded on at a muffler shop. Most Muffler shops burn holes and dont drill. I prefer the clean hole a drill makes.

Originally posted by CowboyDren
you could also make a test pipe just for tuning, with a bung in it.

I was going to buy a test pipe for the track but didn't know if getting one with a bung would be useful for dyno tuning. The problem with plugging into the test pipe is that it is so far under the car that the shop's sensor probably won't reach.

Any reason not to use the original O2 sensor bung in the header? At WOT the car doesn't use the O2. Will the car go into limp mode of give any erratic behaviour?

Steve

No, it's just that the O2 sensor that came with the car isn't terribly useful below 14:1 or above 15:1. You really need a wideband unit to do any testing and tuning. I don't think that it's practical to use the O2 sensor in the header unless you can just tap the signal; if the ECU detects that there is a primary O2 sensor failure, it could make the whole testing session worthless.

...says the monkey that doesn't even know if Nissan ECUs have a "limp home" mode...

Originally posted by CowboyDren
You really need a wideband unit to do any testing and tuning. I don't think that it's practical to use the O2 sensor in the header unless you can just tap the signal

The dyno shop has a wideband unit; I just need to figure out the best way to hook it up. I wasn't going to use my O2 sensor to take the reading... just use the bung for the shops wideband unit. It looks like I will get a test pipe with an O2 bung and hope the shop has enough length on the wideband unit to reach.

...says the monkey that doesn't even know if Nissan ECUs have a "limp home" mode...

Our ECUs do have a limp mode although the only time I recall it happening is when there is something wrong with the MAF.

Steve

Originally posted by autoxer7
It looks like I will get a test pipe with an O2 bung and hope the shop has enough length on the wideband unit to reach.

Our ECUs do have a limp mode although the only time I recall it happening is when there is something wrong with the MAF.

Steve

Been there done that. Test pipes are a pain. Get a Bung welded on is really the best. Reason number one is that the test pipe will change how the engine responds to the VVL. You will not be able to properly tune the VVL with the test pipe in place. Also, Changing a hot test pipe at the dyno adds about an hour to the time. Then just gettting a properly fitting one is not always easy. The dyno should be set up to read O2 from under the car at the header area. That should be the least of your concerns.