Guys,

I have made a few posts talking about the trouble that I have had tuning my combo...I got a chance to install the new WB software on my computer and can actually log the runs now instead of stealing glances at the monitor. I made some runs this weekend and looked at them yesterday. I noticed something funny:

At about 3600-3800 RPM my AFR goes from ~14.0 (I know this is too lean) to 12.0-11.5 and stays there for the rest of the RPM range. The change in AFR is very drastic from 14.0 to the much richer condition and occurs very suddenly. I had the PE vs. RPM table setup at 1.06 all of the way across and was planning on playing with it to richen the car up and lean it out one way or another after I found out where it was rich/lean. However, I doubt that the PE table can lean things out that much.

Am I having another problem here? What could cause such a drastic shift from rich to lean? The car is not knock retarding (per Autotap), and the timing seems good (~28 degrees through the runs).

LTRIMs look good when driving around and are usually +/- 1 or 2.

Could I be hitting a wall with the stock exhaust manifolds? Any of you more technically knowledgable guys have any insight on this? What could cause a suddenly rich condition?

I have kind of a nagging feeling that I might not have installed the cam correctly back when I did the heads/cam (2 months ago)...but would the car run badly enough that I wouldn't be able to tell? I have run a 12.8 @ 108 with the car the way that it sits on a 1.9 60ft. What would be some key signs that the cam is in wrong?

Again, here are my mods (the car is a '98Z) :
- ARE Stage II heads (2.08/1.60 valves)...not milled for compression
- Cam Motion 218/218 .518/.518 114 LSA
- LS6 Intake
- Stock de-screened MAF
- Stock exhaust manifolds (I know, I know, but I am waiting for my TTs to come back from Incon)
- ASP pulleys (alternator and crank)
- 7.350 pushrods
- Stock heat range Autolite Plugs
- Taylor 409 wires

I welcome any ideas on this...thanks again!

Scott

 

Where in the exhaust stream did you locate the wbo2 sensor? Does it do this in all gears at wot? Do you start the logging at 1500 rpm or go wot at 3000 rpm and watch it drop at 3600rpm...the sensor needs some time to stabilize.

 

This is repeatable in all gears...the ones that I used for my evaluation of the problem were 4th gear pulls starting at 1500 rpm or so.

The WB o2 is located in the driver's side of the Y-pipe, about 2-3 inches behind the stock o2 sensor and is installed per the instructions that came with my kit.

Thanks,

Scott

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Scott 98Z M6:
<strong>The WB o2 is located in the driver's side of the Y-pipe, about 2-3 inches behind the stock o2 sensor and is installed per the instructions that came with my kit.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Is that before or after the CAT? If after, is it possible that you're just overpowering the CAT at that point?

Ira

 

There are no cats on the car...

I am pretty sure that the readings that the sensor is giving me are correct, they are repeatable in every gear and the shift happens at the same RPM increments.

My questions is why this is happening and what can I do to correct it via LS1Edit...I tried PE vs. RPM and that resulted in an almost undetectable change.

Scott

 

Whats your fuel pressure doing when you go WOT. If you are getting a pressure spike then that would cause what your seeing. Were are you taking your boost/vacuum reference for the fuel pressure regulator?

How do like the software that comes with fjo setup, I was playing with it the other day. Only thing I wish you could change was the exact range for the rpm and afr.

Gary

<small>[ May 30, 2002, 06:52 PM: Message edited by: red ws6 99 ]</small>

 

Fuel pressure stays constant when I go WOT...it usually jumps about 5psi or so from idle when it gets to 0 vacuum.

However, after I am WOT there is no spike, so that isn't the problem in this case.

I had some trouble logging with the WB software at first, but they came out with version 2 and that seems to work pretty well and has a lot more features.

I too wish that the RPM and the AFR were user scalable...0-10,000 is too big and 0-5,000 is too small...

I need to check and see if altering the RPM readings on the laptop will transfer over to the monitor that I bought. It was reading double the RPM when I first hooked it up.

Scott

 

Looks like other people are having these problems as well...at least that is what it looks like from the ls1Edit mailing list.

Scott