I would like to take a moment and go over PE table usage. Proper usage, improper usage, and different approaches. This is just a culmination of information, my views don't necessarily represent the views of anyone else, tune at your own risk. Note, an AFR of "12.5" is actually an AFR of "12.5 to 1" but is not defined as such everywhere herein.
The best and (hopefully) most common thing to do before tuning PE is to use a wideband O2 sensor to get actual AFR to match the target AFR.
There are many guides available on how to go about doing this, with the MAF and/or VE tables depending on setup.
Alternately narrow bands can be used to tune (only at stoich) when a wideband is not available, however this is not a good idea if the vehicle has anything more than an intake/exhaust. (Even longtube headers can throw off narrowband readings to an extent, they typically slow the switching speed down especially if the placement is poor in the collector)
A wideband is still the preferred measurement device no matter the application, however it is REQUIRED on the following setups
Heads and/or Cam
Stroker
Fuel Change (C16, E85...)
Forced Induction
Nitrous
If you're tuning those setups without a wideband you're going to have a bad time.
With stock setups or near stock setups the factory MAF and VE data is sometimes sufficient, if fuel trims are within 5% or so you may be able to use them, but again, if your vehicle has any of the aforementioned modifications don't even bother trying it.
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How to calculate PE:
This has been covered a lot so I'll be brief.
PE on Gen III and Gen IV motors can be calculated with the following
Stoich AFR / PE Ratio = PE AFR
SO...
If Stoich AFR = 14.68 and PE ratio = 1.20 then PE AFR = 12.23 (14.68/1.2=12.233333...)
See, not so bad!
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Now onto the PE table(s)
The typical thing that seems to be taught is that a PE table should be flat and anything else is very very bad (commonly referred to as PE table "rapeing").
This is simply is not true. Their is a clear difference between using the PE table to command a different AFR across the RPM range and using the PE table to get the vehicle closer to your target AFR, which is the job of the VE and MAF tables.
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Here we see a BAD PE table, done by a "professional" shop.
Attachment 42440
The vehicle is a Twin Turbo Built Motor Corvette Z06 on a 2 Bar Speed Density OS, you're looking at the normal PE table. The idiot tuner not only screwed up the regular PE table, they didn't even use the boost enrichment table which HP tuners provides with the OS! What does this mean?
Imagine driving part throttle, no boost, the PCM targets a particular AFR; now half throttle, let's say 5 psi, car targets the same AFR; full throttle, 15 psi, the vehicle targets the same AFR.
So, for example, it doesn't matter if the vehicle is in boost or not, if you're over 25% throttle at 4750 rpm your targeting 11.1 AFR! Far too rich outside of boost. Additionally the erratic change in the table doesn't make for smooth linear power delivery, its not even a sudden jump to another target AFR! It looks like the beginning of the Millennium Force at Cedar Point!
I'd also like to note that the VE table was off too so the actual AFR at anything other than full boost was richer than 10.0, it pegged the gauge, which is very bad. The vehicle had a dyno sheet of over 960rwhp, imagine what it could have done with a proper tune.
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Here is a STOCK 2006 GTO table,
Attachment 42441
Note the high RPM delay and the step down in target AFR as the RPM's climb. This is a technique used in many applications, and by GM in this case, to run the vehicle richer up top to help protect the motor and meet emissions. Under 3000 rpm the vehicle targets an AFR of 13.6, actually a little lean for making the most torque, but an excellent value to ensure relatively good fuel efficiency when going above 48% throttle but staying below 3000 rpm, "spirited" driving.
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Here's the stock PE table and boost enrichment table from one of my own vehicles, a turbocharged 5.3L LM4.
Below 2800 RPM I target 13.0 for pretty good torque and fuel economy, above that I richen up to about 12.65.
Fuel isn't added at low RPM where is will never be needed and extra is right before redline to induce a backfire when desired. Redline is set past peak power, so if I don't want the turbo-punishing pop I simply shift where I'm supposed to.
If at anytime boost comes on, the boost enrichment table takes over. Where the AFR ramps to 11.56, note the extra fuel added if the boost spikes off the MAP sensor range.
Attachment 42439
Attachment 42442
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Here's a table from a customer vehicle. A 2001 Camaro SS M6 with an intake, and full exhaust, and hardened push rods.
A safe 12.5 is targeted throughout the rpm band, except down below 1600 rpm (leaner) and above 6000 rpm (richer).
Attachment 42447
This car pulls VERY hard, so hard that it still spun 295's with a weak spark through one cylinder. (A spark plug wire wasn't making full contact with the plug, the spark was arcing across)
(This is basically the traditional set one value across the rpm range PE table, with just the small changes mentioned.)
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Originally Posted by danieloneil01
