1998 C1500 truck 5.7L Vortec tuning

[3strokeEngine]

Thanks again! I added the channel and was able to log the MAF freq into my custom chart. I used your method to reach steady state and It worked for me, specially because I'm in a region with a lot of mountains so it's easy to have the MAP steady with any throtle position going up in the hills.



I'm using std version 4.4.4 of the suite. I was able to open your file. Actually we have the same engine/trans combination. I added my last tune for you to try again.

I did the tuning backwards, starting with VE, then MAF and now timing. I'm using goat rope garage method adding 2 degrees to the entire table and running a decent log to see if there's knock at any cell to revert a degree or two, but I'm thinking about letting the timing in some zones nearly stock i.e. idle and decceleration. I saw your timing table and it's configured way different than mine. What method did you use to dial the timing? Dyno?

Can you please explain a little deeper on fuel to wall concept? I saw you have fewer values (part of the table) compared to my table. I want to give it a try but knowing what I'm doing hehe. Thanks in advance!

Generally Vortec heads like about 30-32 degrees of ignition timing for best cylinder pressure. With a higher duration camshaft like the ZZ4 you loose low RPM volumetric efficiency (hence why cammed cars tend to run so rich untunned at low RPM). Because their is less air charge in the cylinders a cammed engine needs more timing to make best torque. Keep in mind the factory likes running REALLY late ignition timing to keep the exhaust hot and Catalytic converts efficient which is why you see factory tables setup the way they are.

I set my ignition timing on an EFI setup the same as if it was a Distributor. For a type mild cam with mild compression (higher compression needs less ignition timing) in a Vortec headed 350 SBC you typically want Somewhere between 18-24 degrees at idle ramping up to 32 degrees at WOT past 3000* RPM. This is your "Mechanical advance" which is the RPM axis on the timing table.

Typical vacuum advance adds around 10-14 degrees of timing at a high vacuum cruise. In my setup i found increasing ignition timing beyond a certain point wouldn't cause any spark knock but would loose power (measured this on the highway cruising at 75 mph with cruise control and averaging how much TPS% was needed to maintain a steady state cruise).

Those are the basic numbers to start with for building a timing table for mild cammed 350, you can play around with how fast the mechanical advance comes in to try to make up for as much of the torque loss as possible but i found on my setup anything more than 30 degrees before 3000 RPM would make make LOUD spark knock under hard acceleration (that intrestingly enough the knock sensor would only pick up about half of the time) so i backed it off some. Back in the good ole days everything was done by feel and hearing no knock sensors to keep things safe, and these early style vortec knock sensors can only pull at most 4 degrees in the stock tune, not something i would rely on for a tuning aide like you can with the dual knock sensor LS stuff.

[3strokeEngine]

Forgot to add: The fuel to wall concept requires an understanding of how the Transient fuel system works.

Impact factor is used as the throttle blades are opening (positive MAP change). The values in the cells are percentages that tell the ECU how much fuel sticks to the intake port walls and doesn't make it into the cylinder. Increasing these values tells the ECU more fuel is needed to maintain the requested EQ ratio in the cylinder during throttle opening.

Evap/Fuel boiling is used as the throttle blades close (negative MAP change). The values in the cells are percentages that tell the ECU how much extra fuel is left sticking to the intake port walls that will instantly evaporate (aka boil) as soon as vacuum builds in the intake port area. Increasing these values tells the ECU less fuel is needed to maintain the requested EQ ratio in the cylinder during throttle closer.

For racing purposes the only one of these tables that matter is the impact factor table because that's the one that gets used under acceleration. The Fuel evap tables just help out with fuel economy not throttle response

[Fast4.7]

Are you using beta version? I can't open the file...

I have 97 k1500 with a vortec 350 zz4 cam swap and i can help you out. First thing you're going to want to do is give that thing some more ignition timing.

You're correct that there is no way to force the blackbox PCMs to MAF only, you have get your speed density dialed in first, then once you're ready to do MAF tuning setup your error histogram with a filter that only logs when in steady state (also no PID for steady state you have to do some custom math with TPS and MAP sensors to log steady state MAF).

Here is a copy of my tune maybe you can copy paste some of the spark tables and base running airflow to your setup and see how it responds.

Also fuel to wall impact factor in the transient fueling tab is kinda like your accelerator pump. Ive increased those tables aswell

Full specs: 1998 Tahoe PCM, 350 vortec zz4 cam bone stock other than that, 4l60e

You certainly can force the black box to MAF only.

[3strokeEngine]

You certainly can force the black box to MAF only.

If so please explain... There is no high rpm disable in dynamic airflow table on the black box computers. That's how you force the LS/LT stuff into MAF only, after the high RPM disable it uses filtered Mass airflow only. Black box OS doesn't have this...

[Hondaeater]

Hey Hondaeater, I'm using the formula provided in my WB sheets [2811.10]*2.3750+7.3125 and actually is fairly the same that shows the gauge (part #03.0300). I've added a screenshot to confirm. Why do I have to take that 5 volts out? In that case, having a 10.56 AFR will result in poor performance. Actually when I reach PE my AFR goes to 12.4 and the AEM WB gets around that value.

To double check it, when I'm near stoick on my WB it's confirmed by the regular narrowband sensors of my truck.

That is good that the Voltage in Scanner and the Voltage output from WB is same, no offsets needed. The EGR Scanner Volts put into the manual's formula works oh that's great ( a little sarcasm). I can't really use a Voltage logged in scanner to quickly know the AFR, sure I can get my calculator out but the New Maths User defined is for you to log the data as a usable AFR value in the Scanner. The problem is when you make the User defined Math Channel to log/watch AFR in the Scanner it must be as I wrote it. Please Try to do it without and then you'll see. The ECU uses the DIFFERENCE of the 5 volt internal sensor reference and subtracts the returning voltage from it to make computations.
This may clear it up.. hopefully. Take a 5 volt ECT sensor. There is 5 volts OUT from ECU reference to the ECT sensor 5v IN,(screwed into block for ground no wire) there's an internal resistance based on temperature, and the OUTPUT returning voltage to the INPUT ECU pin. ECU takes 5v minus returned volts and makes a calculation on the DIFFERENCE to determine the temperature. Same with AEM WB pin. To create the User Math you will need to make the calculation formula as the ECU sees it. Hope that makes more sense. If you only wanted to see the WB value but not use it in the Scanner for open loop calibration and WOT Fuel adjustments, why put it on the ECU pin just look at the faceplate? I would assume it was to make use of the data for those purposes and this will get the Volt to AFR conversion you need. You will still need the EGR in Channel section for that is where it gets the data to calculate for Chart.