rusnak

ok, yes. I read several posts regarding the drawback of a nb. We want a wb.

http://en.wikipedia.org/wiki/Wideband_O2

This is an interesting article. Says 14.1:1 is the butter zone among other things. I now wonder if a permanentl air fuel meter might be useful to monitor the condition of the o2 sensor, as well as vac leaks such as those from intake manifold gaskets and hoses.

rusnak

Ok, finally got around to hooking up the LM-1.

Nice instrument!

I did one pass, and right now I'm waiting for everything to cool down, then I'm going to try a second run.

But it seemed like the CO adjustment stopped responding when the engine got warm. May be just my imagination. But, I thought it might be a good idea to buy a bung and weld it into the exhaust so that I can leave the DME O2 sensor in place.

The instructions say to remove the O2 sensor if it's not going to be powered. That is not the issue here. The issue is that I can keep an eye on the operation of the O2 sensor, and I can see how well the DME is working once the O2 sensor has taken over. I can plug the test bung when the LM-1 is not in use, since I'm not contemplating a permanent installation.

whatayall think?

(the green dot in the first pic is where I'm thinking about installing the O2 sensor bung). In the second pic, I'm thinking about installing a test bung in my catalytic converter in the 3 o' clock position. This second bung will be plugged when not in use.

J. Brinkley

you just want two ports? nothing wrong with that.
life of the sensor is what they are talking about if you leave it in there un powered.


Honestly, I don't know why anyone wants an o2 sensor on a carrera, except for inspection stickers.

here's my advise, not just for you, but anyone that wants to know everything


verify no intake leaks.
And this is where one should take everything off from the throttle body to the air filter.
with the afm in your hands you can inspect it, look for anything wrong. Inspect the set screw, and from all the way closed turn it out seven turns and reinstall.
you can also check all the hoses at the back of the throttle body if you do this.
the pipeline, brake booster hose, check valve, thermoswitch, basically everything back there.
checking injectors would be good to. Then you can check the fuel line from the fpr to the damper.

so you're all back together and starting the car.
let it run till its warm. then turn it off.
set up your lm1
disable oem sensor, put the bypass wire in the socket behind the black plastic plate, or unplug the idle control valve.
go back and forth with the idle set screw and the afm air bypass screw to get around 880 and whatever afr you want, I liked 14.7-15
the closer to lambda the less the o2 sensor is going to adjust, so less flutter on the idle rpm.
This is why i wouldn't run an o2 sensor, you get a perfectly flat idle and solid idle mix.

As the system ages and more unmetered air gets in, the closed loop attempts to fix it within it's abilities. And that's what it's good for. nothing else.
I'd set it and forget it. get a WB display and monitor if you want, but checking it twice a year is good I believe.

rusnak

Thanks J Brinkley!

I'll look for the pin connections to jumper the icv in the Bentley Manual. I think on mine the idle is 800, but in later years it is 880 rpm.

Your post makes perfect sense to me. I'll try it again.

Do you use starting fluid to check for vac leaks, esp. on the intake gaskets and injector seals? Thanks again!!!!

J. Brinkley

actually I've used MAP gas or propane or acetylene. but you can yes.

J. Brinkley

a good shortcut is to take off the oil cap, you car should almost die. If it doesn't, bet money somethings leaking.

rusnak

I have mapp gas, and propane. I don't have acetylene. I think I'll try mapp. It might be more gentle on the gaskets, and you don't have puddles of fuel on top of the motor.

Where did you get that table? What are you using to measure %CO? That would be sweet to add to the LM-1!

rusnak

ok found the location of the jumper connections to disable the ICV.

Since the info is not in Bentley, and is not easy to find, thought I'd post info here to hopefully help the next guy.

Source: (and Kudos) to Steve Wong www.911chips.com

rusnak

Did the whole thing again. This was as close as I was able to get. The adjustment screw stopped responding at 14.1 afr. The unit jumps up and down like it's calculating standard deviation or something. I caught it at a low point with the camera.

J. Brinkley

so what does it do when you take your bypass wire out? and plug the o2 sensor in?

rusnak

Edit:

Did one more test today. The rpm does not change when the jumper wire is pulled out.

I checked the mixture with the DME O2 senser plugged back in, but still dangling on the rear fender support. The test O2 sensor was obviously installed in the cat.

The mixture began to really richen up fast. It went from 14.7 to around 12.5 afr.

So am supposed to ignore this fact, and drive it like that anyway because the afr is set with the dme O2 sensor disabled right? When it is plugged back in and the dme takes over, it wants to richen up the mixture. Is this because it's sampling ambient air?

I'm asking this because I don't want to overwhelm the catalytic converter, and I need to pass smog. What happens if I set the mixture according to the dme O2 sensor plugged back in, while the sensor is danging from the rear fender support? Say I re-install the O2 sensor with the CO mixture set at the newly leaned out level. Will this make the mixture way too lean?

davszabo

Hi, I'm new on this site and also in Porsche's world.
I need some help to have the right solution to buy my 911. I saw a 911 sc 1979 with 179hp in a good condition, but I want more power from this car. Is there any good way to tune this car or should I look after a 911 turbo. It will be good if the car has 300hp.
I live in Hungary(europe) so I have less opportunity than others to find a nice car.
Thank you in advance
David Szabo

Ed Hughes

David:

It is typically not cost-effective to try and get 300HP from an SC. You will spend a lot of money to do that. Most who want to get to the 300HP neighborhood do that with a 993 engine transplant. Turbocharging is also another way, but the few who have done this have had to piece together their own system, as there really isn't a good system being marketed.

rusnak

I will be able to weld in a stainless steel O2 bung in my cat and the cat bypass probably next week or so. I think I might be fighting the dme at this point because it appears the computer won't let me get anywhere near 14.7 afr (Lambda). What is bad is that it looks like 14.7 afr w/out the O2 connected = 12.5 afr with O2 connected = way too rich.

J. Brinkley

I'm a little lost, you have a cat and a bypass and you're measuring using both at separates time, and both have two bungs? or?
for inspection put the cat on with the stock o2 sensor and go do the test. if you don't pass you can fix it at home. But generally if everything is working right it will pass on it's own.
back home after the test do your bypass, unplug the stock o2 sensor, or replace with your wideband and set the idle. Is this what your after?