Sensor readings

[Tleg93]

Overall, my car runs pretty ok but I do have some issues and I wanted to know a couple things about what I should basically expect to see when I look at Vikash's scan tool.

My O2 sensor is reading .9v when I'm on boost, fluctuates wildly when at a constant speed and when I let off the gas after a hard acceleration it reads 0v. I know this isn't right and is most likely due to my O2 sensor being too far out of the exhaust flow. I can't turn my boost much beyond stock even using the laptop as a boost gauge. There are some key concepts that I'm a little foggy about when it comes to timing and some of the other values.

What should I basically expect to see at 10 psi for some of the other readings?

Thanks

[THAWA]

Well, to get a basic idea of what ranges you want, open up the fsm, you can get it from josh's site. And go to page 226 in the pdf, page 99 of section 2-7, or T900. It shows what the select monitor should display when looking with it. It's essentially the same deal right?

As far as the actual readings, I dunno.

[vrg3]

My O2 sensor is reading .9v when I'm on boost,

Sounds right -- you run rich on boost.

fluctuates wildly when at a constant speed

Sounds right -- you're in closed-loop when cruising, so the signal bounces around above and below about half a volt.

and when I let off the gas after a hard acceleration it reads 0v.

Sounds right -- the injectors cut off when coasting so the sensor reads a huge amount of free oxygen.

What should I basically expect to see at 10 psi for some of the other readings?

Umm... I dunno... just off the top of my head, ignition timing should probably be in the 15 degrees BTDC ballpark, maybe... Timing correction should be two or three degrees maximum... Airflow signal somewhere in the mid-to-upper 4 volts region... load numbers somewhere around 230-240ish...

[Tleg93]

Thanks for the tips. When I turn my boost up my car doesn't seem to go much faster. I haven't installed the FCD yet since my boost gauge isn't in but even so, when I'm just below fuel cut I can't really notice any difference yet. When you were in my car, Vikash, I was running around 10 psi. If I turn it up a crack it runs pretty much the same. Matt was kind of saying that the intercooler doesn't provide much protection if it's heat soaked so I haven't turned up the boost or installed the FCD yet. Sorry about the rambling.

[vrg3]

There's an easy way to see for sure whether or not you're getting more air at higher boost -- look at the airflow signal. If the voltages are higher, you're flowing more air. Just pick an engine speed to read it at.

But at this point you may be nearing the plateau of the curve with your stock turbo...

[douglas vincent]

And your oxygen sensor readings sound right to me. Thats basically what I get.

[Tleg93]

Hmm, well maybe the turbo is maxed. It seems like Subarina was pulling a lot harder before the turbo swap than mine is now though.

[vrg3]

Well, variance in memory aside, Subarina's exhaust is nicer than Majen's. That, and the transmission, may have something to do with it. I dunno, though... Majen was surprisingly quick to me.

[Tleg93]

I'd probably lean towards the tranny being more the issue. Even though Subarina's exhaust is mandrel, I can't see it being that huge a factor since we're both running 3". If I was pushing over 280 hp I could probably see it being an issue.