Well guys, I got my Diablo Predator tuner today and couldn't wait to get to tuning. No dyno results yet (would like to fine tune first), but I an tell you that my "seat-of-the-pants" dyno tells me that if uncontrollable wheel spin and the sideways angle of the car are any indication, this thing certainly made some ponys in my car. Now comes the fun part, tuning. So, all you guys that know a hell of a lot more about this car (and tuning it) than I do, here is my question. For my car, with the mods listed in my sig, what are the real world stats that I need to pull from the diablo to know what to change and how to change it for the ultimate performance tune with this product. In otherwords, when I use it to "Scan" what am I looking for and what do I do with the information?
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Stacey J. Manning, J.D.
"All go... that IS the show"
Thanks JB. Now I'm just waiting for info on custom settings. From what I've read, it doesn't sound like timing advance is appropriate, but A/F ratio may need to be changed based upon my mods. I just don't know what to look for while doing a "scan" or how to change what I'm seeing. I'm hoping someone can walk me through the process.
I just made runs on the street with two Predator programs and here is the data. Maybe you guys can help me sort it out for optimal tuning with the Predator. (Amoco 93 octane/outside temp = 57/temp control = 80/trac control on). Tell me what you think.
1st Run with A/F = -5% and Timing = +2%
Idle
LTFT1 = 13.28%
LTFT2 = 13.28%
02S Bank 1 = considerable variation
02S Bank 1 = 715 mv
02S Bank 2 = considerable variation
02S Bank 2 = 670 mv
Cruise (65 mph)
LTFT1 = 12.50%
LTFT2 = 9.38%
02S Bank 1 = 90 - 695 mv
02S Bank 1 = 790 - 845 mv
02S Bank 2 = 65 - 770 mv
02S Bank 2 = 760 - 830 mv
WOT (5th from 60 mph)
LTFT1 = 15.63%
LTFT2 = 14.06%
02S Bank 1 = 695 mv
02S Bank 1 = 935 mv
02S Bank 2 = 720 mv
02S Bank 2 = 930 mv
2nd Run with Stock Predator Tune (A/F=0%/Timing=0%)
Idle
LTFT1 = 10.16%
LTFT2 = 11.72%
02S Bank 1 = 60 - 830 mv
02S Bank 1 = 780 - 790 mv
02S Bank 2 = 80 -860 mv
02S Bank 2 = 690 - 710 mv
Cruise (65 mph)
LTFT1 = 10.94%
LTFT2 = 7.81%
02S Bank 1 = 80 - 785 mv
02S Bank 1 = 850 mv
02S Bank 2 = 120 - 815 mv
02S Bank 2 = 815 mv
WOT (5th from 60 mph)
LTFT1 = 10.16%
LTFT2 = 10.16%
02S Bank 1 = 905 mv
02S Bank 1 = 935 mv
02S Bank 2 = 910 mv
02S Bank 2 = 935 mv
Well I'm no expert and don't have any experience with Predator or power tuning (yet), but from what I've read, a "Scanner" is not all that useful for fine tuning puposes. I believe typical Scanner functionality is more for general EFI OBD-II troubleshooting.
Accordingly, most "D-I-Y" scanners are a poor choice for any form of power tuning.
The problem is not so much the scanner built-in to Predator, as it is the O2 sensors that came with the car.
A factory O2 sensor generates a voltage signal based on oxygen content in the exhaust. Stock sensors are not all that precise and only serve as an "esitmate" of stoichiometric conditions.
Under normal driving conditions, ideal AFR is 14.7:1, and the PCM is constantly "self-correcting" via small changes to the EFI pulse width in response to continuous left/right bank O2 inputs. Also, EFI control to maintain the ideal AFR is based on a host of lookup tables and progressive engine load fuel maps, pre-established by GM for a variety of parametic control (and environmental) conditions.
All you can "measure" with an inexpensive scanner is O2 signals in +/ - variations from a center point calibration of 450mV (which equates to 14.7:1). Apparently, Predator converts the O2S signal voltages from millivolts to percentage offset, either + or - from 450mV. (For example, I suspect an average reading of 495mV of both O2S, left and right bank, would convert to +10%).
The problem is, at WOT, the PCM control mode goes into open loop and ignores the O2S partly b/c of the inaccuracies and partly b/c it is no longer desireable to maintain 14.7:1. The PCM is programmed to intentional skew the AFR lower. This is called Power Enrichment Mode.
As I understand it, and this is an oversimplification, the PCM factory programming contains a biasing or offsetting factor. This is implemented as a multiplier applied to the Power Enrichment WOT fuel map table that changes as a function of engine rpm.
To power tune the LS6 engine we have to somehow "adjust" the multiplier in that table appropriately to achieve a normalized AFR for WOT. The desired WOT AFR is commonly believed to be within the range of 12.5~13:1, assuming the pump octane rating of the fuel is ~93. This form of tuning requires a very delicate balance of adjustment to avoid overcompensating AFR and going too lean.
From what I've learned the only way to get accurate AFR measurements is with a fairly precise measuring device know as "wideband" O2 analyzer. (Apparently the factory O2S are essentially "narrowband" and only reasonably accurate at exactly 14.7:1).
The dyno shop with a wideband O2 analyzer hookup is the answer. There are two types. One that simply mounts into the end of your tailpipes (probably a single sensor for only one half of the exhaust system, left of right). The second type is really the same type of analyzer but hooked up via a bung inserted into the exhaust header pipe. A modified version of either type would be an "averaging" analyzer with dual inputs, with two sensors one in for each half of the exhaust system. The latter is not very common, but probably the best for the most precise form of fine tuning.
Hope this helps to explain what you're up against. A dyno shop with wideband 02 analyzer is key to effective power tuning with Predator (or LS1 Edit) and plenty of available time to do trial and error adjustments.
Not having unlimited access to dyno and air fuel ration meters, I'm trying to work with what I have (like most guys probably). If I can see gains with a Predator (I have ween sotp gains with the stock Predator tune) and tweak it a little bit for even more, I'll be happy. That is what I am trying to do. Since my last post, I made some more modifications to the tune and my last one was -2% Air/Fuel ration and 0% timing advance. If these numbers seem good (I'm no expert and I hope someone who is will confirm the quality of the tune given these elementary numbers from a handheld tuner), I will stay with them and go to the dyno for some before and after results. If these numbers suck, I'll go back to the stock Predator tune and then go to the dyno for some before and after numbers. You guys tell me.
93 octane Amoco gas; 55 degrees outside.
Idle
LT1 = 11.71 to 12.5
LT2 = 10.16 to 12.5
O2S1 = 760 to 770
O2S1 = 505 to 535
O2S2 = 770 to 805
O2S2 = 500 to 515
Cruise (65)
LT1 = 8.59 to 11.72
LT2 = 7.1 to 8.59
O2S1 = 720 to 770
O2S1 = 700 to 785
O2S2 = 710 to 750
O2S2 = 720 to 745
WOT 3rd Gear (higher rpm; rolling at 30 and hit wot)
LT1 = .78
LT2 = .78
O2S1 = 870
O2S1 = 935
O2S2 = 895
O2S2 = 930
KR = 0 (no ping detected)
WOT 5th Gear (lower rpm rolling from 50 to 60 mph then hit wot)
LT1 = .78
LT2 = .78
I am saying that these numbers are useless and mean nothing. You cannot just look at one number. You need to see a range of number covering the entire RPM range.
You cannot just glance at OBDII numbers and know what is going on with the car. These parameters are changing very quickly. You have to look at a data log created while driving down the road.
You need to check the car out with a wideband and a full featured OBDII scan tool. FWIW, the stock O2 sensors are not even close to accurate at WOT so you will not get a good readings from these even if you have Autotap. You need to check them with a wideband.
I'm with Ross (rbartick) here ... however, a lot of people are using the wrong kind of wideband now-a-days, thus resulting in totally off ratio readings, but oh well ... gotta learn somehow ..
Thaks for the input guys. I'll take all I can get. Btw, at this point, she pulls great and seems to be running well. I'll hit the dyno later in the week and post some results.
Will do. BTW, I do realize that scan resuslts from the Predator using the car's own O2 sensors are not the most accurate way to tune, but I think for a great many guys (me included) we don't have unlimited access to dyno's and tuners. If we did, we wouldn't be trying to do some modest tuning with handheld devices like the Predator. I am hoping that the numbers that I am getting are close to accurate. By the way it is running, I think it may be. I may be all wrong, but I will find that out when I do go to the dyno. If I'm way off with my A/F mixture, I will find out then and can go back to the 0/0 set-up that came with the tuner. I'm hoping to do a pull w/the predator set up with -2% A/F ratio and another with the stock tune. If the -2% A/F ratio is way off, I'll do one more pull with the Predator out-of-the-box tune. Max out of pocket for dyno pulls, $225. Minimum cost, $150.00.
Originally posted by Waterfreak Will do. BTW, I do realize that scan resuslts from the Predator using the car's own O2 sensors are not the most accurate way to tune, but I think for a great many guys (me included) we don't have unlimited access to dyno's and tuners.
Actually, looking at a few real-time O2 readings is not accurate at all. You are wasting your time there and PITW.
You need to check the car over the entire RPM range with a wideband and a real data logger. That is the only way to do it. If you want real results then shortcuts are not possible.
H2O freak, you're right about the appealing nature of a "layman's basic tuning approach". For many that is all one can afford or has time for. I know exactly what you mean. It can be very tempting to just take a shot in the dark.
BTW, I have a question for you.
If you are adjusted Predator to "-2% AFR" are you doing exactly that? That is, are you literally reducing the A/F ratio by 2%? If that is what Predator is doing to your PCM, then by decreasing the A/F ratio, you are making the engine run "richer".
Conversely, if you are actually biasing the WOT PE fuel map by -2% using Predator, then that would result in "leaning" out the engine, and probably not a good idea.
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Now comes the fun part, tuning. So, all you guys that know a hell of a lot more about this car (and tuning it) than I do, here is my question. For my car, with the mods listed in my sig, what are the real world stats that I need to pull from the diablo to know what to change and how to change it for the ultimate performance tune with this product. In otherwords, when I use it to "Scan" what am I looking for and what do I do with the information?
Linear Mode
