SilverSurfer

I was under the impression, maybe mistakenly, that PE was not the main table that the 98 PCM uses for WOT fueling. Yet when I look at tunes on Horist's HP tuner site I see 98s being WOT tuned solely by PE adjustments. The tunes I looked at were supposedly done by TEA and Ed Wright.

Anyone care to shed some light?

foff667

iTrader: (2)

maf is also used in fueling at wot...ive seen some tunes where they ONLY used maf or where they ONLY use PE...depends on the tuner & their philopshophy.

SmokingWS6

iTrader: (1)

Many people have different theories of how to tune WOT. PE functions the same way 99+ pcm's do. For true PE tuning your maf calibration as well as VE fueling should be taken care of before hand.

Perhaps you were thinking of the secondary VE table?

slow

iTrader: (7)

To calibrate the PCM correctly, the “commanded air fuel ratio” needs to be what you are targeting for WOT fueling. The PE and the OLFA table (or whatever it is called on the software your using) will be the commanded air fuel ratio. You need to adjust the fueling characteristics, or airflow characteristics, depending on what you think is incorrect to get the commanded air fuel ratio to equal the measured air fuel ratio with a wideband, regardless of tuning “ideas” this is how it should be done. If your not matching what your commanding, then your lying to the PCM, and that cannot be argued.

I set the PE to what I want the commanded air fuel ratio to be, and then adjust the airflow values to get the actual AF to match the commanded.

Ryan

SilverSurfer

Well, I searched Horist's list for 98 Fbodies. I looked at 2 that were performed on vehices with Ported heads and 224 cams. One had minor VE tuning for idle in the Primary table, but nothing else was touched in VE. Secondary table was stock. Maf tables wasn't touched. IFR table was stock. PE was the only table fully modified.

I thought 98s ran off the VE table and PE was used for 99+ cars.

SmokingWS6

iTrader: (1)

Don't look at the "professional" tunes. As all they do is adjust ifr and pe.

98 pcm's still use the same tables. PE stands for power enrichemnt. All years reference this table when commanded.

soundengineer

iTrader: (16)

the proper way to adjust your PE is to use a wideband....
set your PE to be the AFR multiplier that you want it to be....
then go tuning your VE/MAF as driving normal and making sure to enter PE

you will then use AFR Error % which is 100*((Actual AFR - Commanded AFR)/Commanded AFR))
using this equation you can dial in yoru VE and MAF...just a simple copy/paste multiply by % or Multiply by %-half it it gets too close and starts to overshoot slightly

SRPerformance

In SD car, I added 10 to effected VE rows and this did not change the AFR at WOT.

So, I set PE to 1.32 But 14.7/1.32 = 11.13 AFR and we are only seeing 12.2 Wideband. What else could effect AFR in WOT?

foff667

iTrader: (2)

maf sensor

SRPerformance

This car is SD and does not have a MAF

foff667

iTrader: (2)

ahh sorry...can you post your bin file so we can take a look?

soundengineer

iTrader: (16)

or if you cant post it here..post over on HPT uners forum
www.hptuners.com/forum
we allow direct post of bin and hpt files

SRPerformance

I can not post here, file over 100kb will post to

http://www.hptuners.com/forum/showthread.php?t=4363

Thanks.

soundengineer

iTrader: (16)

well..first thing...it looks like PE delay is set to 5500...I was told that it want supposed to do anything in an F-body car..but that might be why in a holden commodore...set PE delay to 0
also cold PE TPS vs RPM should not be 0 down low...that wil fubar your part throttle fueling down there bigtime...
I like to set it to be about 65 up to 3200..... 40 at 3600.... and 25 from 4k up

usually you put your PE table to the AFR you want....and tune the VE to match when you do an SD tune.. as PE is directly referring to the VE table in SD...

SRPerformance

The PE delay at 5500rpm does not work, I adjust PE from 3200 rpm and it works.

I will try cold PE TPS vs RPM settings, thanks.

I find this interesting as for example one car makes best HP at 12.2 on the dyno. So if I set PE to 1.125 AFR(13.0) than your VE would not be correct, spliting hairs here. Can you determine airmass per cylinder for VE without entering PE. Use part throtlle reaching max rpm before PE and then compute the higher rpm.... or this would be a waste of time?

SilverSurfer

One interesting thing I found is that after making changes to the tune on both my 98 and 02 PCMs and then taking the cars for a run is that I get lots of KR and audible knock. This is a road trip that include some 1/4 passes and not a dyno run. After you make a pass or two the KR goes away as does the audible knock. Am I the only one? If I'm not then based on this, "tuning" becomes alot more difficult in real life than on a dyno.

So PE affects all years and not just 99+ cars?

soundengineer

iTrader: (16)

it goes away because of a factir called Knock Learn...
it sees knock and moves towards the low octane table.reducing timing...
eventually it will return and be learned out again and again...
there are settings you can change to fix that so that it returs quicker

remember that PE is supposed to be a direct multiplier of the VE or the MAF...but its just not tat accurate...
if you tune with PE off....and have a different value in your tune than what you want as your end result...
meaning you have 14.63 for example...and you are shooting for13.0
when you switch the tune over to reflect the 13.0....it will be off and you will have to correct the tune some more....
tune it like you are going to drive it...

if your car makes best power at 12.2 on teh dyno then set youe PE to reflect 12.2 and tune the entire VE with PE enabled..
it will still command stoich at part throttle and PE at WOT..and you will then get the Fuel transitions correct as well and reduce and tip in knock that might occur...you can still get it from impropwer fueling...but it will be reduced greatly.