Tuning Advise… installing cam
 

Need to replace balancer so decided to install cam (224/230 .550 on 111+2 LSA). Otherwise stock LS1 including exhaust manifolds. 110k miles and primarily HPDE car.

I’m debating tuning method… originally was thinking MAF and VE by trims adding some extra in the top end to be safe. But now I’m thinking should do wideband.

With cam only, stock exhaust… you think trims are acceptable tuning method for the track?

For WB, I am thinking LC-2 temporary install into front O2 using battery pos and neg posts with maybe a switch. Good plan?

Or do a mail order tune for simplicity? Don’t want to pay for dyno/street tune yet as I likely will add heads/headers later. And I'd want it to be open tune since I like to tinker, especially with E mix.

I wouldn't go thru the trouble and time of a VE tune---Not necessary---If you were a tuner with your own software maybe--But the HP gains are minimal and drive ability will suffer
At your expected HP levels the stock open/closed loop tune with the MAF would be the simplest and easily done via mail order--A VE tune would require taking it to a tuning shop
On larger duration cams I often will disable the LTFT fuel trims as they tend never to settle down or clean up your cam is on higher end of the mild side so you should be able to use the trims------ When using LT headers they will also tend to make your fuel trims go crazy so I would then also turn them off

I have HP Tuners and think I know it fairly well playing around with stock ls1. If I tuned by trims I’d prob do both MAF and VE separately but would have to extrapolate the top end based on CL. Then confirm it by narrow band readings. This sounds ok to me, but if bad idea... I could buy WB plug into front O2 on OL. Or mail order, but it would have to be unlocked.

Anyway, trying to decide. Thanks for the feedback!

without wideband you are like a blind in the dark. you can get them for under $200. and put it into the rear bung.

I hear ya. I’ve never wired a WB before and working with stock manifolds/cats.

I was thinking... use battery pos / neg with switch for temp install plugged into AC sensor. Use front O2 with tune forced into OL, then replace NB after tuned. Good plan?

Just noticed you suggested rear bung... you think post cat is ok? But isn’t it best to tune in OL anyway?

The stock narrow band 02's on cars newer than 99 are actually quite accurate-- Not like the pre 98 02's that were not heated-- On a street car you can get the WOT fueling close enough without giving up any top end HP----as long as you error just slightly on the side of rich---I ideally using the stock narrow band 02's try to get the voltages around .900 millivolts----higher is richer-----

Tuned idle and by trims up to 4,500 rpms... MAF is easy, VE a little painful so far. Quick 2nd gear romp looks ok around 900mv. Will temp wire a WB soon... deciding now whether a simple WOT check with WB in secondary location or doing a full OL tune in the primary position.

Question:
During VE tuning, I failed MAF with 1Hz high freq but did NOT change the DTC. After about 15min of driving CEL and low power... this happened twice. Changing to "fail on 1st error" will eliminate this?

Yes. The MAF DTC needs to be set to Fail on First Error to fail the MAF.

Thanks! Seemed MAF was failed since trims were so diff, but after 10-15min limp mode.

OP, when you change a cam shaft size, any camshaft size from stock you have altered the VE "volumetric efficiency" of said engine. To tune it correctly you need to remap the VE table then turn your MAF back on and tune that appropriately.

I ended up with temp install post-cat... and from the initial scans seems pretty accurate so far. You do have to be careful though... for example right after WOT sitting at stop light think there's residual fuel in the exhaust causing richer readings. And idle is very slightly richer... which seems opposite. But so far at speed seems you can trust the readings.

Doug is correct...most tuners do not take the time or effort to adjust the VE and will even deliver the car with the High RPM Disable at "MAF only" (i.e 400 rpm). The VE is used for transient compensation during the blended strategy and really makes the throttle/vehicle more responsivebut which is a prime desire for an HPDE outing. Drag cars can use MAF only as they are just stab and go... numerous Hard Accel/Decel events leave the MAF airflow reporting seriously in error due to the intake manifolds dynamic nature. Its like a sponge...absorbs air during hard acel (fill the vacuum) and releases air during hard decel thus making the g/cyl calculation to predict cylinder air mass inaccurate thus resulting in overly rich or lean fueling....the place track cars live in most of their lives....

VE can be tuned on the street though it is simpler on a load bearing dyno. Proper use of filters (especially throttle up/down) will help improve your error data and provide quicker and more accurate updates.

As far as the Wideband in a postcat position, not the best spot especially if using OEM cats....after all they wont heat up as much and do consume o2 as a part of their job so it will affect the readings. You will see a leaner reading for sure....I would use about a half a point leaner for tuning purposes. Certainly idle and low cruise could have issues. If this is the only way, then I would almost recomment tuning the idle/cruise with the trims and use the wideband for PE/WOT scenario's.

Ed M

I'm doing a combo of trims and WOT AFR tuning both VE and MAF... I find the car is smoother in SD than MAF only. I don't really trust the fuel cells for filtering and instead using TPS and speed. Actually the WB seems to be richer post cat, which makes sense if cat takes out O2. I'll check it in the front in OL soon... 1 unsure thing about post cat is the voltage offset which will be confirmed pre-cat.

I'm learning a lot with my first comprehensive LS tune. I just changed cam keeping stock exhaust for now. MAF didn't need to be changed much except was pretty rich from the factory. VE table is very different though.

Interesting stuff, isn't it? I am going through exactly the same process now with LC-2 at rear bung. I got the VE almost tuned, and hoping to move to MAF this weekend. I got some false knock that's been slowing me down, as I've been weary to desens the KR.
Need to try racing gas to verify there's no true knock. My target PE AFRs are under 13, and the spark is conservative, but I have an UD pulley that some say can cause resonances that look like false knock.

1 of my first tuning exercises was false knock. I ended up going to an E mix to rule out real knock and increased the global gain which eliminated it.

Also increased decay rate and lowered max retard when on 91... which my 91 map is very conservative, but very occasionally there will be slight KR.

Since doing the cam, I will experiment reducing my gain to see if something may have changed.

You're kidding right?

My conclusion on pre vs post cat WB... slightly leaner at WOT and little richer at idle and most low speed situations. And after WOT causes much richer reading during cruise. During cruise at speed for awhile seems to be fairly accurate.

OL was set at 12.5 though... stoich at cruise/idle would have been better comparing to NB. But this was just a quick session to confirm everything was ok.

And NB aren't bad in precision it seems, BUT have to get some datapoints first. For me roughly 870mv = 12.5 and 920 = 10.X

Josh, interesting findings. Are your pre/post CAT findings based on OEM or high flow cats, Primary or Secondary location etc. The further the O2 sensor is from the exhaust source the cooler the exhaust temp and the more inaccurate the O2 sensor (for both narrowband and wideband) becomes. Even wideband O2's have issues when measuring a high overlap cam at idle

The exhaust temperature effects on the sensor are even worse when it comes to the narrowband being used to tune wot as there is just not enough dynamic range to compensate for the anticipated error. I do not believe that your specific findings would be repeatable across a larger sample size where the widebands greater dynamic range and resultant accuracy are more repeatable.

You are relying on a 50 mv difference between NA and FI target AFR's and that 50 mv window is further compromised by differences in exhaust temp as well as the age/degradation of the O2 sensor itself. To me there are just way too many variables to even consider tuning with the narrowbands especially if they have been moved further from the exhaust port as when installing Long Tube headers.

All I have read (and adhere to) is anything outside of Stoich +/-.5 AFR is not predictable/accurate. Cerainly if you are in wot and your NB is reporting 600-700mv, you should be worried but to tune with them is just too risky for my taste..

I have seen similar writeups but just haven't seen enough evidince to sway me to the dark side.....but will keep an open mind....:cheers:

Ed M

You are right... WB is much better. But if you are forced to tune by trims you can at least confirm "not too lean" with NB. I first tuned my new cam by trims, bumping up VE and MAF to be safe. Ended up close to 0.90g cylAir and 110% IDC targeting 920-ish mv. Car was strong but at 10.x a/f I later confirmed. Now at 0.72g, 95% IDC at 12.2-ish a/f. So you can tune a drivable safe car but have to error on the rich side. Surprised 10-ish a/f felt so good... leaner feels better but not by a huge amount.

Going over my logs I think it would be fairly precise. Maybe I'll export to excel soon and check it more thoroughly. Of course each NB is different... i'm showing 30mv diff but this is likely combo of NB and bank fueling diff.

Now I'm also a little unsure whether I could have an offset in the WB (LC-2). In OL I tuned 12.5, which I should have done at least portion at stoich to confirm it, but I failed to think of it. Taking voltage at the output, it matches obd reading. And pre-start will show 5v and initial start 0v... so I think its accurate.

I have pulled the WB for now though since I need a more solid setup for the track.

edit: Oh, WB was in stock front and rear locations with stock 01 cats.