What is Tuning? By Definition

[AJxtcman]

Originally Posted by submariner409

those who believe there is some magical way to tune a late Northstar FWD PCM for significant gains in power and "speed".

Originally Posted by stbtt

I have tried a read on a 2003 STS but I get denied access. Security access denied invalid authorization code when the type of car comes up it will tell me that it is a 2006 DTS it was unknown before my last update I think. It will tell me it is a 06 DTS on the scanner too

Originally Posted by Bill HPT

Nope, if our software won't read it its likely because we don't support the pcm and haven't written the bootloaders for it yet.

Originally Posted by AJxtcman

I have the ability to Recalibrate Northstar PCM's. I am working on unlocking more functions and a program to let people do it with a laptop.

As I have said all along I use TIS and a Tech II for Northstar's

Another conversation

Originally Posted by AJxtcman

do you have access to TIS and a Tech II or a MDI?

Yes, TIS2WEB (ACDelco TDS) plus a Mongoose and TechII.

Originally Posted by AJxtcman

Great I will send you an email on a process I use to flash custom tune with TIS.
Maybe you already know how.

Thanks but I really have no need, I have a feeling I know what you do though as all TIS files that get flashed are cached on the PC

As you can see from these conversations the main issue is the communication with the Cable and the PCM.
The way around that is the Tech II and TIS and I am not the only one that knows how to do that!!!!!!!!!!!!!!!

[submariner409]

Good ol" Quadrabog - mostly brought on by those who fooled with the secondary air valve spring wrap, causing a big midrange stumble.

Most QJ secondaries (the mechanical linkage throttle butterflies) start at about 50% to 60% BUT the upper secondary air valve will not move until there's sufficient engine rpm and vacuum to begin to push them open, and secondary enrichment comes from the secondary air valve cam and hanger lifting the metering rods as the air valve rotates. If the engine does not have the cubic inches and air volume demand, the secondary air valve will never fully open regardless of the carb's CFM rating, so a QJ self-adjusts its airflow to each engine it is installed on. (Holley uses a somewhat similar self-metering approach with vacuum secondaries, you change to light secondary diaphragm springs and BINGO ! - midrange stumble.)

Not sure what those PCM enrichment tables are saying, but they are NOT saying that enrichment lags TPS by 5 seconds. Maybe 5 milliseconds, but not 5 seconds - that's enough time to hole a piston from lean burn at high rpm.

[AJxtcman]

Power Enrich Fuel
Power enrichment tables are used when the VCM detects wide open throttle (WOT) operation and provides extra enrichment to achieve maximum power.

Power Enrich Mode Delay
This constant specifies the amount of time (in seconds) the power enrichment is delayed after all the power enrichment enable conditions have been met.
Power Enrich Mode Delay Bypass RPM
If the engine RPM is above this threshold the Power Enrich Mode Delay will be bypassed. Above this RPM power enrichment will be enabled immediately after all the enable conditions have been satisfied.

This is from a 99 Chevy Truck 5.7L 100% stock tune


This is from a 2004 SSR truck with a 5.3L 100% stock tune


This is from a 2004 Silverado SS 6.0L 100% stock tune


This is from a 2002 Carmaro LS1 Z28 with a 5.7 100% stock tune


This is from a 2003 3800 Bonnie 100% stock tune


This is from a a 2000 car with a 5 second delay just like a Northstar 100% stock tune

[N0DIH]

Like my 454, setup for HD towing, is 60 seconds! And the bypass rpm is set to 4900 rpm, redline is set to 4500! So you will never see it.

So that means when you are towing that 10K trailer through the pass on I70 in Colorado west of Denver, you are towing heavy @ 14.7:1



So even if you back off for more than 0.2 seconds it will reset the PE Mode timer and you will have to wait again for 60 seconds to get enrichment back.

And people wonder why the 454's were dogs. This is why. ALL 2500 and 3500 trucks/vans are setup this way, 100%, Ford and GM even. Ford V10, LQ4 6.0L, L29 454, L31 350. All with a 60 sec delay. 1500's didn't get the 60 sec delay, but the 2500/3500's did.

[submariner409]

OK - I missed the rapidly decreasing delay times at 80%+ throttle opening - and the PCM also delays timing quite a bit at part-throttle acceleration.

Looks like on a 2000+ Northstar, if you stick your foot in the firewall, enrichment comes immediately.

[AJxtcman]

It isn't the same for all of them.

Exports with RPO K29 PCM or R1X Noise Control have a 2 second delay before the car downshifts. This is a very common export RPO. That means German Export cars suck.

Now this is a Factory Hot Rod
This is from a 2004 Silverado SS 6.0L 100% stock tune


Now this is a Stock 6.0L PE Delay from a Burb


This is a Stock 02 GMC Denali 6.0L PE Delay


This is a Stock 02 GMC Truck 6.0L PE Delay


This is a Stock 02 Escalade 6.0L PE Delay



Now not all of the other PE parameters are the same on the ones with 0.00 second delay and the same goes for the ones with a 60 second delay.

GM has this stuff all over the board

[N0DIH]

Some do, you would think the HD trucks that have the huge delay in PE mode would eat pistons or something, but they don't. I think it relys on Piston Protection Mode and/or Cat Converter Over Temp (COT) mode to enrichen, but it is typically VERY rich, like 10.5 - 11:1. So it goes whacko in fueling.

I am guessing that it the >8600 GVW Emissions Cert that covers the pathetic things they do.

It will help mpg some by keeping you out of PE so easily, like my 454 has a stock PE Mode table (and how much it adds, think EQ Ratio as the Stoich - EQ Ratio = Commanded AFR) like this:

But as you can see, on a 454, yes, the vaunted 454, PE mode is forever cursed @ 60 seconds! Even if you flatten your foot on the firewall for the whole quarter mile or more! Or imagine with a trailer in tow, 10K worth trying to move into traffic and never get the extra power from PE Mode.

What good is a good engine if you can never use the power from it? And to make matters worse, GM installed the cam on the 454's 6-9 degrees retarded!

Originally Posted by submariner409

OK - I missed the rapidly decreasing delay times at 80%+ throttle opening - and the PCM also delays timing quite a bit at part-throttle acceleration.

Looks like on a 2000+ Northstar, if you stick your foot in the firewall, enrichment comes immediately.

[N0DIH]

Yup, what I have noticed is LQ4's are never put in 1500's, so they get the cursed 60 sec PE mode timer, but the LQ9's are only put in 1500's and they do NOT get the PE Mode timer set to 60 seconds....

Originally Posted by AJxtcman

It isn't the same for all of them.

Exports with RPO K29 PCM or R1X Noise Control have a 2 second delay before the car downshifts. This is a very common export RPO. That means German Export cars suck.

Now this is a Factory Hot Rod
This is from a 2004 Silverado SS 6.0L 100% stock tune


Now this is a Stock 6.0L PE Delay from a Burb


This is a Stock 02 GMC Denali 6.0L PE Delay


This is a Stock 02 GMC Truck 6.0L PE Delay


This is a Stock 02 Escalade 6.0L PE Delay



Now not all of the other PE parameters are the same on the ones with 0.00 second delay and the same goes for the ones with a 60 second delay.

GM has this stuff all over the board

[submariner409]

N0DIH, Your observation that most GM 454 cams are retarded is spot on. Even in the marine engine realm, we find that the engines are running with a log tied to them: cam timing.

Retard the cam and the power band moves higher in the rpm range, costing midrange torque and power. Advance the cam (4 degrees) when you stab it in and the power band moves down a tad, giving a midrange lift in torque and power: the cam "comes in" faster. Allowing for chain stretch and age, the cam will still be in timing specs tens of thousands of miles (or hundreds of hours) out............Many cams are purposely ground with about 2 degrees of advance for just that reason.

(Kicker is that we're fooling with Northstars and not 454's or any other non-Northstar engine, so all the above non-Northstar tables are moot and serve no purpose other than to add to the confusion.)

[N0DIH]

Agreed, I was showing what GM does on the engines, we have found on nearly all have the PE Delay in some sort. Performance engines often have none, and non have several seconds to as long as a minute....

Originally Posted by submariner409

(Kicker is that we're fooling with Northstars and not 454's or any other non-Northstar engine, so all the above non-Northstar tables are moot and serve no purpose other than to add to the confusion.)

[submariner409]

What's the rationale for holding off on power enrichment for such lengths of time ? Emissions ? Efficiency ?

A well-tuned QJ or Holley, allowing almost immediate enrichment at any point in the throttle opening, can be an incredibly clean burning carburetor. Why the electronic delays - when an electronically adjusted fuel delivery is much faster in response than a mechanical system ?

[N0DIH]

My guess on the heavy trucks is towing they would be in PE mode a lot and aside from mpg, the emissions could be "bad" or out of 14.7 as that is the only place the cat converter is efficient at would be "turned off" essentially the whole time and the converter also would cool down. So it keeps emissions better on average at the sacrifice of power.

[AJxtcman]

Originally Posted by AJxtcman

This is from a Northstar PCM. Not the LS1 PCM setup.

Power Enrich Enable Delay Time Vs. TPS   
TPS   Seconds
0%       5.00
5%       5.00
10%     5.00
15%     5.00
20%     5.00
25%     5.00
30%     5.00
35%     5.00
40%     5.00
45%     5.00
50%     5.00
55%     5.00
60%     5.00
65%     5.00
70%     5.00
75%     5.00
80%     3.00
85%     1.00
90%     0.00
95%     0.00
100%   0.00

Power Enrich Enable % TPS Vs RPM   
RPM         TPS %
0%          75.00       
400         75.00 
800         75.00
1200       75.00
1600       75.00
2000       75.00
2400       75.00
2800       67.50
3200       60.00
3600       60.00
4000       60.00
4400       60.00
4800       60.00
5200       60.00
5600       60.00
6000       60.00
6400       60.00

Originally Posted by submariner409

N0DIH, Your observation that most GM 454 cams are retarded is spot on. Even in the marine engine realm, we find that the engines are running with a log tied to them: cam timing.

Retard the cam and the power band moves higher in the rpm range, costing midrange torque and power. Advance the cam (4 degrees) when you stab it in and the power band moves down a tad, giving a midrange lift in torque and power: the cam "comes in" faster. Allowing for chain stretch and age, the cam will still be in timing specs tens of thousands of miles (or hundreds of hours) out............Many cams are purposely ground with about 2 degrees of advance for just that reason.

(Kicker is that we're fooling with Northstars and not 454's or any other non-Northstar engine, so all the above non-Northstar tables are moot and serve no purpose other than to add to the confusion.)

The thing is the code above is an 2000 to 2003 Northstar!!!!!!!!!!!!!

This is a 2006 DTS PE



This is a 07 XLR PE.