This topic got broached in another thread I recently started on poor mileage with my 4.9L. I am planning to install an Allante intake manifold. Raydar brought up the different MAT sensor locations and the fact the Allante had no EGR while the 4.9L does. Without EGR and a MAT sensor location less prone to heat soak from the cylinder head, the Allante MAT will run much cooler

Tunercat has the definition files for both engines. After looking at the documentation there are 6 tables that relate to the MAT:

MAT Spark Advance Correction Factor Vs. MAT
MAT Spark Advance Compensation Vs. MAT at Idle
Base Pulse Compensation Vs. MAT
Sync. A.E. MAT Correction Vs. MAT (not sure what Sync A.E means)
Heavy Load Spark Retard Vs. MAT in Low Gears
Heavy Load Spark Retard Vs. MAT in High Gears

The equation for fuel injector Base Pulse Width is:

BPW = BPC * MAP * MAT * A/F * VE * BVC * BLM * DFCO * DE * CLT * TMB

where:

BPW = base pulse width
BPC = base pulse constant
MAP = manifold absolute pressure
MAT = manifold absolute temperature
A/F = air fuel ratio for other than closed loop
VE = volumetric efficiency
BVC = battery voltage correction
BLM = block learn mode
DFCO = decel fuel cut-out
DE = decel enleanment
CLT = closed loop i.e. the value from the integrator
TBM = turbo boost multiplier

It would seem like values in all six of the above tables need to be changed when swapping to the Allante intake

[This message has been edited by sanderson231 (edited 06-27-2022).]

I imported the Allante IAT tables to the 4.9 PROM image. Don't think I messed with those other tables.
Since both applications use 19# injectors, I just multiplied the 4.9 BPW (thought I remembered Base Pulse Constant, but I could be wrong) by 1.1 (Which is, essentially, 4.9 divided by 4.5.) to accommodate for the increased flow of the Allante intake system on the 4.9.
It's a crap shoot, but those two changes give me BLMs of 127-129, in part throttle cruising.

I want to say I imported the Allante VE and spark tables, too, but it's been a long time, so I'm not really certain. I was chasing a "phantom ping" which turned out to be intake noise, so there's no telling what I changed. (I actually made notes, with every change, but it's been a long time.)
Of course, all the "EGR ON" tables were stuffed with "EGR OFF" values.
EGR Enable parameters were set to something absurd, so that EGR would never be commanded.

[This message has been edited by Raydar (edited 06-24-2022).]

Raydar,

I am going to get the Allante definition file and do a side-by-side to the 4.9L. If the spark advance vs MAT table was not changed that may explain why you had to advance the base time to 20 degrees. I think I've go this under control now so don't spend time looking for old notes. Thanks for your help

quote Originally posted by sanderson231: Raydar, I am going to get the Allante definition file and do a side-by-side to the 4.9L. If the spark advance vs MAT table was not changed that may explain why you had to advance the base time to 20 degrees.

I had (have?) both files as well.
I'm not sure there were any changes (at least on the face of it) that would warrant an additional 10 degrees of lead, but I could be wrong.
Please let me know what you find. There are at least two other 4.9/Allante installations, besides mine, running ~20 degrees base timing.
One of them was even "massaged" by a well known chip tuner.

[This message has been edited by Raydar (edited 06-25-2022).]

quote Originally posted by sanderson231: Sync. A.E. MAT Correction Vs. MAT (not sure what Sync A.E means)

AE is typically Acceleration Enrichment... Makes a little sense that that would be calibrated to IAT/MAT because AE is basically a calibrated guess, empirically determined, anyway.

[This message has been edited by Will (edited 06-27-2022).]

Thanks Will - acceleration enrichment makes sense.

Just ordered hardware and software from Tunercat. I'll use the compare feature in tunercat to check differences between the two definition files. It may make sense to use the Allante definition file and just change the base pulse constant (BPC) from the 4.9L to account for larger displacement.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

Got the hardware and software from Tunercat and realized the difference between a definition file and a calibration file (.bin). The definition file just configures the tunercat program to work with a certain PCM. The calibration file is what contains all the data. I did not get a definition file for the Allante from tunercat. Does anyone have an Allante calibration file either broadcast code ATTL or AUMF. I can buy a new prom from Autozone for $55 but just trying to save the bucks.

quote Originally posted by sanderson231: Does anyone have an Allante calibration file either broadcast code ATTL or AUMF.

Check your email.

Thanks Raydar for the Allante .bin file>

The Base Pulse Constant is 167 for the 4.5L and 183 for the 4.9L. These differ by the ratio of the displacements

Concerning the tables that involve MAT:

]MAT Spark Advance Correction Factor Vs. MAT[/b}
there is no difference between the 2 engines

[b]MAT Spark Advance Compensation Vs. MAT at Idle[b]
there is no difference between the two engines if the MAT is above 20 'C

[b]MAT Spark Advance Correction Factor Vs. MAT
neither engine uses MAT to correct spark advance

Base Pulse Compensation Vs. MAT
there are minor differences in the compensation factor

MAT 4.5L 4.9L
-40 'C 0.066 0.057
-28 'C 0.061 0.054
8 'C 0.056 0.052
32 'C 0.053 0.051
56 'C 0.049 0.049
80 'C 0.045 0.047
104 'C 0.044 0.046
128 'C 0.043 0.044
152 'C 0.043 0.043

This basically accounts for the decreasing air density at higher temperatures


Sync. A.E. MAT Correction Vs. MAT (synchronous acceleration enrichment means pulse widths are widened during acceleration
there are differences but not sure how much difference this would make - this is a multiplier - not sure what the difference between a multiplier and a factor is

MAT 4.5L 4.9L
-40 'C 0.352 0.656
-28 'C 0.352 0.656
-16 'C 0.332 0.645
-4 'C 0.301 0.625
8 'C 0.281 0.586
20 'C 0.281 0.508
32 'C 0.254 0.430
44 'C 0.195 0.352
56 'C 0.117 0.285
68 'C 0.059 0.250
80 'C 0.020 0.203
92 'C 0.000 0.156
104 'C 0.000 0.156
116 'C 0.000 0.156
128 'C 0.000 0.156
140 'C 0.000 0.156
152 'C 0.000 0.156

Heavy Load Spark Retard MAT Factor Vs. MAT in Low Gears

MAT 4.5L 4.9L
-40 'C 0.250 0.996
-28 'C 0.250 0.996
8 'C 0.250 0.996
32 'C 0.500 0.996
56 'C 0.996 0.996
80 'C 0.996 0.996
104 'C 0.996 0.996
128 'C 0.996 0.996
152 'C 0.996 0.996

Heavy Load Spark Retard MAT Factor Vs. MAT in High Gears

MAT 4.5L 4.9L
-40 'C 0.250 0.996
-28 'C 0.250 0.996
8 'C 0.250 0.996
32 'C 0.500 0.996
56 'C 0.996 0.996
80 'C 0.996 0.996
104 'C 0.996 0.996
128 'C 0.996 0.996
152 'C 0.996 0.996

In conclusion there does not seem to be an apparent reason why the 4.9L with the Allante intake likes more timing advance.

There are significant differences in the Volumetric Efficiency Tables. Here is a comparison around WOT (wide open throttle) conditions

4.5l

RPM kPa
90 95 100
4000 84.8 87.1 87.1
4400 88.3 90.6 90.6
4800 89.1 90.2 90.2
5200 84.8 86.3 86.7

4.9l

RPM kPa
90 95 100
4000 83.2 82.8 82.0
4400 84.4 84.4 84.4
4800 84.4 84.4 84.4
5200 82.8 82.8 82.8

Despite the higher volumetric efficiencies for the 4.5L, the 4.9L flows more air under all conditions because of its larger displacement. Interestingly, the 4.9L flows more air at 5200 RPM than at 4400 RPM where the HP is peak at 200. So at higher RPMs the percentage of fuel getting burned must be less.

Some of the volumetric efficiency difference is probably due to the fact that both engines use the same head and thus the head is relatively larger for the smaller displacement engine. Obviously the rest has to be due to the better intake for the 4.5L.

Sorry about the tables. The spacing was not maintained when I posted
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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

[This message has been edited by sanderson231 (edited 07-04-2022).]

quote Originally posted by sanderson231: ... The Base Pulse Constant is 167 for the 4.5L and 183 for the 4.9L. These differ by the ratio of the displacements

BUT... both engines use 19# injectors, and are rated at 200 HP, out of the box.
So, with the additional airflow of the Allante intake, on top of the additional displacement, I figured that the BPC should be increased by that ratio, yet again.
Check the BPC of the tweaked 4.9 file I sent. My BLM at an "easy cruise" hovers right around 127-128, so I have to believe I'm close.

I used 19# Ford Motorsport orange top injectors in my Northstar to make 312 RWHP... so 19's have the headroom for whatever you want to get out of the Allante 4.9.

Interesting to see the differences in VE.
Does the timing drop dramatically between the 4400 RPM power peak and the 5200 RPM top of the VE table on the 4.9? Is there another factor that reduces fuel flow that would result in fuel flow matching real world power?

BSFC varies a little bit, but generally not much at constant MAP, which covers WOT.

4.9L Main spark advance vs RPM vs MAP - EGR off

RPM 85kPa 90 kPa 95 kPa 100 kPa
4000 33.3 32.0 32.0 32.0
4400 35.2 35.2 34.1 34.1
4800 35.9 35.9 35.9 35.9

Not much going on - assume 35.9 holds for 4800+ rpm

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged