02 sensor values for cammed cars

[zo6racerx]

I've checked the sticky posts for the major of the day and I saw in one post http://hptuners.com/forum/showthread.php?t=570 where some guys say a big cam will make things more difficult for the O2 sensors to stabilise, mainly because ot the extra air and cooling effects on O2s that result from increased durations.

My 02 Z06 also has LG long tube headers. I seem to have a problem where a give the car throttle and the 02 sensors don't respond for about 4-5 seconds. Sometimes the car will go lean (16.5:1) in this spot. Other than that the car is pretty good drivibility wise and WOT is really good.

Is there a way to adjust the 02's so that it can help the response of the 02's? I tried rear 02's in the front locations (suggested by LG) and it didn't help any. The car was fine with just long tubes but with the aftermarket cam it's been this way ever since. Right now all of my open/closed loop 02 settings are stock for the Z06 calibration.

Anyone?

[EC_Tune]

I personally haven't had problems on Vettes with LT's. Just tune the VE, MAF & Spark to suit your engine.

[Billiumss]

John,

If you still want me to check your car out, let me know!

Bill

[Billiumss]

I saw a post of yours (around 6-11-07) where you posted your tune, I 'd say your VE table needs a lot of work.

[zo6racerx]

Thanks guys. My tune was considerably off. I was able to dial it in considerably better using the wide band and the histogram.

[Billiumss]

Thanks guys. My tune was considerably off. I was able to dial it in considerably better using the wide band and the histogram.

Care to post your current tune so we can look at it?

[zo6racerx]

I saw a post of yours (around 6-11-07) where you posted your tune, I 'd say your VE table needs a lot of work.

I"m the guy that tunes Johns' car.

I saw no point in tuning the VE table over 4000 RPM's since the mass air does all the work over that point. I have since however smoothened the transition over 4000 rpms and I had a couple things I wasn't doing that made my changes counter productive. Thanks to the help of the HP tuner guys I understood the problems and corrected them.

I'm posting my VE tables but it's not really going to help anyone because every car is different and even 2 cars with the same combo are going to react differently. VE is affected by many different engine parts (heads, cams, intakes, Cold air, exhaust, throttle body, maf) There's literaly hundreds of combo's.

John had a mail order tune from a company he bought 30 pound injectors from and from the company that he bought the heads/cams. Reputable people too. Neither tune was remotely close and the plugs and 02 sensors fouled out. It took chopping at the tune up a little at a time.

I came into the picture after he changed the heads/cam and loaded the mail order tunes. Also at that point his 02 sensors were not working which slowed the progression of the tuneup.

I'm a hardcore Ford guy and I know Fords very well. The GM stuff (at least this Vette) has been a little challenging but thanks to several people taking the time out in PM's to help it's helped tremendously.

There were a few major problems I had from things I didn't know.

1. Underestimated the power of the Historgram. I finally used it and hooked the wide band up to the scanner. This really comes in handy and is probably the best tool I've seen on many different types of tuning softwares. The car comes in nice after you tune both SD open loop and MAF open loop.

2. I wasn't getting in Speed Density mode because I was disabling PO103 all together instead of turning off the code with the drop down box. THe drop down box isn't really visable and something you don't see if you don't know to look for it.

3. I had 02 wiring issues were the 02 sensor heater circuits were not turning on because melted wires against the headers were blowing the fuse for it.

Finally after I got the car to really switch to SD I tuned the car in SD mode open loop, then tuned the car in Maf mode open loop and then turned closed loop back on. A/f is within 1% and the trims are dead on.

One thing that I find a little odd is how far GM is behind in Mass air technology. Tuning Ford's is just a tweak of the mass air curve basically. There's no going in between speed density and mass air modes. The mass air on the Ford cars have no problem handling transitions effectively.

Dave King

[Billiumss]

Dave,

Having a tuned VE table in a GM LS1 PCM is more important than you think, ask around on here and you'll understand more and why. I know all too well about the hundreds of mod possibilities, I've tuned dozens and dozens of these cars over the past 4 years.

Glad your making head way on that car, sounds like it has many issues.

One of the nice things about the GM system is that you can run either SD mode or MAF mode with the same PCM and OS.

When you get it running good, post up some numbers, should be pretty good.

Bill

[zo6racerx]

Dave,

Having a tuned VE table in a GM LS1 PCM is more important than you think, ask around on here and you'll understand more and why.

Bill

Like I said in my last post I now realize that the VE tables in SD are looked at not only certain RPM's but also during unsteady MAP transitions because the MAF is unefficent and that it looks at a combo of the two a lot of the time.

I also understand that many heavily modified NA cars and Supercharged guys turn off the MAF. This is a shame because SD can not give you an accurate tune because it can't adjust A/F for any changes in Air or climate. The GM system is very overcomplicated because their mass air system technology is under-developed. You definetely have to put a lot more time into dialing in a GM LS1-LS2's fuel requirements compared to a late model Ford.