desr32, TBI heads are great for torque production. The problem with TBI heads is that that they run out of breath around the 3500 rpm mark.

Hmm?....


Edit: I have a 1994 K Blazer 5.7L TBI....is there a specific year "369" module to ask for?

To fix the module problem is pretty simple, just grab a 369 marked module from a 5.0/5.7 TBI fullsize van. Rbob recently did some testing with the 369 and 048 marked modules. I had noticed a high rpm power drop-off when I installed my replacement module in my van. After reading this post, I went and grabbed a "369" module from a 1993 fullsize G20 Van. My power over 4,000 immediately increased.

048 and 369 modules

Here are the results of his testing.

Quote:
Originally Posted by RBob View Post
Have some interesting information to add this this thread.

First item to note is that in the opening post of this thread, the table shown as for AUJP is not. It is the latency table used for AXCN & ANHT. Which are Corvette large cap distributors. The poster in the thread that liquidH8 linked switched the two tables in his post.

AUJP uses table 2 in the following:

Code:

Table 1 Table 2
RPM usec usec

6375 137.34 305.2
6000 137.34 305.2
5600 137.34 305.2
5200 137.34 305.2
4800 137.34 305.2
4400 152.6 305.2
4000 152.6 289.94
3600 137.34 320.46
3200 167.86 305.2
2800 183.12 244.16
2400 137.34 274.68
2000 137.34 244.16
1600 106.82 305.2
1200 45.78 274.68
800 0 213.64
400 0 0
0 0 0


I have been able to identify two different ignition modules for the small cap distributors. They are the 048 and the 369. Check out the picture of the modules. It is the first 3 digits.

I ran 2 each of the 048 & 369 along with a Holley module through some tests. This was done on a live engine using a marked balancer, timing light, and the What's Up Display to show the commanded SA timing and the engine RPM. The EBL Flash had 5 calibrations banks set up for testing.

Bank 0 was the stock calibration to start up the engine and let it settle in.

The other four banks all had the main & extended timing tables set to 20 BTDC. Temperature comp, PE, launch mode, and whatever else was zero'd out.

Then each of the four banks had different latency tables. Banks 1 & 2 had the two tables shown above. Then banks 3 & 4 had the same tables with the low RPM latency values of 0 filled in with the first value greater then 0 from above it.

Code:

Instead of this:

1600 106.82 305.2
1200 45.78 274.68
800 0 213.64
400 0 0
0 0 0

It was:

1600 106.82 305.2
1200 45.78 274.68
800 45.78 213.64
400 45.78 213.64
0 45.78 213.64


The reason for this was that it was found that the at-crank timing dropped off with the stock table values of 0. The was still latency at the low RPM's that needed to be accounted for.

With this change running the RPM from 800 through 3200 had each module with the appropriate table holding a steady SA. Switch the table and the advance moved around as the RPM changed.

The Holley module (part # 891-103) matched table 2. This was from 800 through 3200 RPM. Did not test past this RPM.

You may be thinking that 3200 is a low RPM. However, look at the engines/vehicles the ignition modes are used in. None of these engines are high RPM. Trucks, Vans, TBI 3rd gens, Caprices, Wagons, even the TPI engines aren't high RPM engines. Note what happens in the following tests. . .



Another test: while checking the timing as the RPM was increased, both the 048 & 369 modules held steady until a particular RPM. This was with 048 & table 1, then 369 with table 2.

The 048 module, it held steady timing until about 3800 RPM where it retarded 4 degrees. Then by 5000 RPM the retard had increased to 6 degrees.

The 369 module, it held steady timing until about 3200 where it gained 2 degrees of advance. This held steady to 5000 RPM, which is the highest RPM it was checked at.


If we could get a sampling of the ignition module in various 3rd gen engines it would be helpful. Under the cap check the 3 digit number and post back. Along with whether it is TPI or TBI. If you know the stock BCC that too would be helpful.

Conjecture:

I know that the latest f-body TBI calibrations use table 2. This matches module 369. Same as the AUJP TPI calibration. I wonder if the 048 modules are for performance limiting, and are set up to limit the engine RPM. With the timing retarded, the power drops off, and most people either up-shift or lift.

Where the 369 modules (the ones I have are from 5.7l full size vans) are more performance oriented. What is interesting is that the 369 modules I have are newer then the 048's. Some even look to be replacements (too new for the age of the vehicle). Maybe a GM upgrade?

RBob.

As you can see 5,600 lbs van with 3.08 gears, 1,600 rpm stall, and P295/50/R17s being pulled by a 305 can run a 15.006 @ 92.30 with a terrible 2.28s 60' time.