del91_305

i recently swapped by TBI over to carb, and have completey got it up and going yet. I am in the process of tuning the carb, i have an autometer air fuel gauge installed and was wondering if it is accurate enough to tune the carb by. Its the stock O2 sensor and it has been relocated because i added hedders and had to invest in a custom Y pipe. the car does really good up in the RPM's but right out of the hole from and idle to WOT in stumbles a little

Apeiron

Not really. It might help tell you when you're close while cruising, but when you're at WOT.

92_ZED

I'm going to say both yes & no. The stock O2 sensor will let you know if the carb is going lean or rich. If at WOT and the O2 is less then 800mV I'd be concerned.

Off idle it can let you know whether the AFR is dropping lean or going way rich.

OTOH, with headers and the O2 located downstream it may not be getting hot enough for a good reading.

Al.

P.S. swapped the distributor out for a non-computer controlled one?

del91_305

Of course,

So i should just stick to the vacuum gauge alone?

Apeiron

Stick to the vacuum gauge for tuning the idle mixture. For WOT tuning there are the tried-and-true methods of plug reading and timed runs. If you want to be more scientific about it, you could use a wideband O2 sensor.

del91_305

Ok so let me ask you this. With the O2 sensor a little farther down, its gonna to read leaner than it was in the stock position right? I have got the car running pretty good now, got the IMS Dialed in just right and the timing and choke are all right.But it still acts like its running a tad bit rich, small hesitation right out of the hole and rich smelling exhaust. When at or close to an idle it reads rich, then at part throttle it goes to around ideal sometimes gets close to lean, then at WOT it just goes to the tip of rich.

Also what does this mean? I can test the sensor to see if its right? How do i check?

NastyL98_T/A

Learn to read plugs the right way.

dimented24x7

iTrader: (2)

The stock O2 is useless. Its only intended to provide a sharp, non-linear signal on either side of stoich to the ecm to tell it whether the fuel is heading lean or rich. OTOT, its very sensitive to temperature changes and it stops responding when the temp drops below 600 deg F. Getting a WB wouldnt be a bad idea in addition to whats already been stated. I have one from innovate and its a really slick unit. You can even datalog with it.

brutalform

I agree with dimented. The LM-1 WBO2 meter is the bomb. You can get dialed in with EFI, or a carb. Here is a link. Not real expensive, but it will pay for itself in the long run. Check out the training videos on it.
http://www.innovatemotorsports.com/

del91_305

Which would be???

dimented24x7

iTrader: (2)

My guess would be do a WOT run, immediatly pull over and shut down, and start inspecting the plugs.

92_ZED

If under 800mV at WOT I'd be concerned that the engine was running too lean. As others have noted in this thread a NB O2 isn't the best. However, it can be useful when used as a general guideline for tuning.

Only way to check the O2 sensor is against a known good one.

Al.

del91_305

Ok, well i guess ill pick me up a wide band. Any idea how much these run?

brutalform

Innovate's LM-1 is $299.00, for the WBO2, meter, wiring, etc. This is the basic set. You can purchase their RPM converter seperately, or I do believe the instructions are on Craig Moates site, to build your own. Without the RPM converter, you will only be able to log AFR over time, as to RPM, MAP etc, if you do get one. Innovate has different kits you can get, but are more expensive than the basic kit.

Auggie

Well, I probley will get flamed for this but I do all my carb tuning with an K&N Air/Fuel Monitor. I have a buddy who builds engines for a living and he said that they don't work. I said why don't you try it. So he bought two of them and off to the dyno he went. Installed an 02 sensor in each header (down stream) and taped the monitors to the window. Went through normal cam breakin procedures and made 25 pulls. The sensors lit off right away and the dyno A/F ratios were exately the same as the monitor readings. He was so impressed he installed them in his Corvette. Anyhow heres how I go about tuning the Q-Jet carb. First of all you will have to get the pri. squared away so I install a rubber band on the sec. throttle plate lockout to prevent them from opening. Find a nice quite stretch of road and make a WOT run on the two barrel (what a pooch) and make adj. useing the rich stop. Then make some runs between 60 & 80 mph and use the lean stop. I set the WOT runs to 13.5 to 1 and the midrange runs at 16 to 1. When you have that done add the sec. system and work with air valve opening, air valve opening rate, metering rods and hangers. Works like a charm and doesn't cost an arm and leg either. Just my .02.

Auggie

Auggie

Carb pic.

brutalform

There IS more than one way to skin a cat. One thing with the LM-1 is you can get detailed info from your logs. You will know your AFR at any RPM and at any MAP and TPS reading. This is very helpful to the people that have EFI, and are tuning the eprom for WOT.