Ditmeion

iTrader: (1)

I decided to get my car dyno tuned today. I went there with O2s showing between 890-900 at WOT.



Anyways, my A/F was about 13.6 (per their wideband) from 2K-4200 RPMs, but then it goes rich to about 11.5 from 4200+...this is not a gradual increase either... it goes to 11.5 within 400 RPMs & stays there through 6500.

I changed ....Fuel>Power Enrich, PE Enrichment>V8 Mult vs. RPM in HP Tuners with absolutely no difference
(1st run 1.200 in those fields... last .9) (7 pulls total) did not make much difference at all.

The guys there said I shouldn't of messed with the VE tables (but it runs sooo much better than on stock VE tables)

I'm running 28* timing with no knock at all.
I do have the SLP 85mm MAF, with resistor removed & Z06 tables loaded.

I only picked up 3HP & 20 ft lbs torque since only having a MAFT & now tuning with HP Tuners.

Can anyone shed some light on why it runs rich @ 4200-6500 ?
TIA

white2001s10

iTrader: (4)

How much exactly did you pull from PE vs RPM?
If your VE is way too high then a little change to the PE wouldn't have made much difference.

I assume you've ruled out other possibilities like the COT

Oh, and how/where was their wideband installed?
If it was just in the tailpipe then I wouldn't rely on the data.

TXCAMSS

iTrader: (60)

I had the same thing happen to me as well as another friend of mine. We had our VE tables all lined out + or - 3 across the board, but when I went in to get it dyno tuned with the WB it was very rich and PE changes had very little effect on the AFR. We had to scale down the VE table to get the AFR in range. We did have COT turned off in both cases. I was running in SD and the other guy was not.

Should we keep our VE table closer to the lean side to prevent this? Like you I was wondering if I was missing something.

ringram

Tuning your VE with LTFT's is bad IMO for this reason. LTFT's chop the VE table into 6 parts instead of the hundreds which it actually is. So LTFT based tuning is a rough attempt at tuning the VE. You need to use a wideband then you will see EXACTLY what you are running at each RPM and MAP point.

I think you guys might be finding this out.

Someone with more experience in LTFT tuning might be able to confirm this suspicion.

Ditmeion

iTrader: (1)

I did a total of 7 pulls....graph shows 1, 6 & 7.

So adjusting PE vs RPM DID make a difference from 2000 - 4200 (1st run was about 11.5 all the way across), but all 7 had the dip after 4200.

I haven't touched COT settings yet, but I did let the car cool down after a couple pulls....no help.

I first started to only pull a little from PE vs RPM (1.200 -> 1.080) then the last run I set it to .9000 for testing...I've since changed them back to about 1.050.

The wideband was installed by putting the sensor up one of the tailpipes.

Now my O2s showed about .950+ from 4200+, so it is running rich at 4200+

I can try to go back next week & mess with lowering the VE tables...they were suggesting messing with the MAF settings to fix this

SSpdDmon

iTrader: (10)

My money is on the cat overtemp setting. I had the same problem tuning mine on the highway...cough...cough...I mean dyno in 3rd gear. The COT protection would kick in every time...until I killed it.

white2001s10

iTrader: (4)

Turn off the COT.
If you still have the problem after turning off the COT, then the above quote suggests to me that your VE is WAY off in that load/RPM area. PE should never have to go down to 1.0 or lower.

Ditmeion

iTrader: (1)

I'll give disabling COT a try..makes more sense than my VE table being off, because my VE table does not drastically change from 4000->6000...practically levels off after 5000. If dyno shop is open tomorrow, I'll see if it fixes my problem & let you all know.... Thanks again