90c350

Ive been doing some reading of old threads and came across the one about the stock 048 Module retarding timing at higher rpm's. I did a check and I still have the old 048 module in my disty. I do notice that I get a bit of a fall of above 4000rpm. Now i ordered the 369 module and was wondering a few things? Will I notice a difference in power at the higher rpm's?? Also will i have to change my spark curve or the settings in the spark latency table?? Thanks for any help!!! I would think that I should only see a 2 degree increase in my total time from 3600rpm up if I read the posted correclty. So instead of a programed 34degree's now im seeing somewhere around 28/30. And with the 369 mod I should see 36degree's, with no other changes. Would this be correct?????. Thanks again for any help

Fast355

iTrader: (2)

From my experience, if you have the timing set for 34*BTDC @ 5,000 with the 048 module you will see about 28* and with the 369 you will see about 36*. This is with the stock latency settings for both modules.

Six_Shooter

iTrader: (2)

Couldn't the latency tables be adjusted to compensate for the retard of the 048 module?

RBob

iTrader: (1)

Yes, as can the slight advance of the 369 module. The question is: who wants to stand over an engine doing 6,400 RPM while checking the timing.

RBob.
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90c350, you shoud use the latency table entries for the 369 module. These are listed in liquidh8's thread. As far as a difference in power, it depends if you have advanced the timing to what the engine likes. If so you may find that with the 369 module & latency table there is now too much timing.

RBob.

90c350

Rbob- what happens if I dont use those latency tables for the 369?? will it hurt anything?? And im not sure wich latency table to copy?? there are a few different ones on that thread as far as i can remember. Will it realy make that much of a difference if i dont change the tables?? Thanks again

95chevyTBI

Originally Posted by Badass69
I did a bunch of part swaps on my 94 and it never performed any better. I have MSD wires, cap and rotor, no difference. Advanced my base timing a bit, still nothing. Then I read over on Chevytalk something that Fast305(1983G20Van over there) posted. My 92 always pulled harder at high rpm than a bunch of other TBI's and I never knew why. He has found that part # starting with 369 ignition module advances the timing by 2 degrees at 3200 rpm over the other module (starting with 048) and then holds it all the way through the range. The 048 retards the timing by 4 degrees at 3800 rpm and 6 degrees at 5000 rpm. I checked my 94 and it had a jobber Blue Streak ignition module in it. Checked my old 92's distributor and sure enough it had a 369 Delco. Swapped that module in and the truck is like it has a different engine in it. It used to fall on its face and shift at 4000 rpm at WOT. Now it actually pulls and shifts around 4600 rpm WOT, like a normal truck. The engine is tired and still a dog, but its a lot better than it was. I would check that out because the best supporting parts in the world do nothing if the timing doesn't advance properly.

said by fast 305(355),

It has to do with distributor latency (offset). Basically that means that there is a certain amount of time from the time the trigger signals the module until the coil fires the plug. This time alters the point in which the spark plug will fire in relation to crankshaft angle. If it takes longer the spark will be more retarded. The ECM is programmed with a lookup table to compensate. GM produced two modules with very different latency settings but used the same table for both. In essence they added a built-in rev limiter with the 048 modules. I actually found the 048/369 module difference out by accident when I switched to a new distributor (bushings were worn out) in the van. Unknown to me it had an 048 module and I lost power, a LOT of power up top. I checked the base timing and it was right on the money. It took me a while before I actually tested the engine up to 5,000 rpm while checking the timing with a taped balancer. When I did test it, I found 6* of timing retard. First I assumed it had to be the pickup coil and swapped it for the old one. No change. Then I swapped the module and found my lost power and confirmed the timing change with the timing light. Ever notice how much PE timing the TPI bin ARAP has? Thats to compensate for the 048 module that is in it. Robert Rauscher (DynamicEFI.com & maker of the EBL) also did some testing, through a slightly improved and different method and found the exact same thing as I. I found something even better than the 369 module, in that the spark advance stays consistent, and you get more dwell, more current which results in a hotter, more intense spark. Its called a Dyna-Mod and it is made by D.U.I. Tom (Haulin@$$) and I were talking about it this weekend. We both feel its a much better module than any other module we have found and it sells for $65.00! It made a drastic difference in the spark duration (not peak voltage) on my van running on an ignition scope, before I installed my MSD 6AL.

The Dyna-Mod for most TBI trucks is the 8-pin.

http://www.performancedistributors.com/modules.htm

90c350

Thanks for that reply 95!! I had read that somewhere but couldnt find it. Must have been on fullsize forum. Guess i will just swap them out and see what happens. Thanks again guys!!

95chevyTBI

and yes i was over a fullsize chevy and found the post by fast

RBob

iTrader: (1)

You need to use the correct latency table. Otherwise it is back to square one of not knowing what the at-crank timing is. For the 369 module use this table:

It still has the extra 2 degrees in it. But otherwise is a close match.

RBob.

18436572

I have a spare module that has 419 on it instead of the 369 or the 048. anyone done any testing on it.

90c350

Ok thanks for the table Rbob!! Now can i just enter those numbers into my bin using tunerpro or will i have to copy them from another xdf file?? If it is just a matter of typing in those number thats no problem for me. Thanks again!!

Six_Shooter

iTrader: (2)

You can just type them in.

90c350

Sorry to bother you all again!! Just want to confirm my thoughts? I have just burned a new chip with the suggested latency table, and will be installing the 369 module tomorrow at work. It is replacing the stock 048 module. Now with this table and the 369 module will i only see an increase of about 2 degrees above 3600rpm?? So i shouldnt have to change my spark timing much if at all, correct?? The current latency table was defenatly different than the one Rbob gave me. That is the stock table and the 048 module. The only factor that I understand that may affect my timing is that I thought i was getting 34degrees all in by 3600rpm and in fact would have only been getting 28/30 correct?? I dont have any knock counts currently at those rpm under wot so I may be alright with the timing actually getting what I programmed. And hopefully more power to boot!! Thanks again guys. sorry for the run on paragraph's. LOL Any thoughts to confirm??

RBob

iTrader: (1)

From the latency thread (https://www.thirdgen.org/forums/diy-...y-table.html):

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 your previous calibration was using latency table #1 along with the 048 module, the above shows what the at-crank timing was doing.

With table #2 (which is what I previously posted in this thread) and the 369 module there is a gain of 2 degrees starting at 3200 RPM, through 5000 RPM. I have no idea what the latency is above that point.

By changing from table 1 and an 048 module, to table #2 and a 369 module, the at-crank timing can increase by up to 8 degrees.

If that is worrying, then back down the timing tables and slowly add timing back in until the performance is good.

RBob.

Six_Shooter

iTrader: (2)

All this talk of latency has me wondering how to test the latency of modules, without being connected to an engine.

Maybe using a dual input O-scope, one input monitroing the input to the module, the other monitoring the output? Then align the pulses. Hmm.

Of course there would need to be a trigger system made to trigger the module, but that shouldn't be too difficult.

Looks like I have another project or circuit to add to my test bench.

Fast355

iTrader: (2)

A V8 small cap HEI to trigger the module should work well. The pickup coil itself is possibly part of the latency change. Knock the drive gear off and hook it to a small electric motor with a variable speed. Electric drill is probably too slow as most only turn 1,000 rpm (equivalent to 2,000 rpm @ the crankshaft of an engine). You need an electric motor that has an operating range from 0-3,500 rpm or so. You can hook up a normal automotive tach to measure the RPM.

90c350

THanks again!! I just wanted to confirm my thoughts before doing the swap. I dont think that i should have to take out any timing but we'll see. Thanks

RBob

iTrader: (1)

For proper latency measurements the module is required to be triggered by the distributor. A square, triangle or sine wave input to the module changes everything. The module input filter is designed around the waveform produced by the reluctor & pickup coil pair.

I've tested this on the bench along with putting the distributor in a lathe to spin it. That also allowed for characterizing the ECM circuitry.

At this time I am working on a fixture to hold and spin distributors. The electronics for this was the easy part That part is built & tested. I looked into the old Sun distributor machines but they don't like higher RPMs. Like to be able to spin to at least 3000 RPM, with 3500 RPM being better (6 - 7K engine RPM).

And at the same time set the distributor RPM to any value (instead of discrete steps). This way a latency table can be built from the data.

RBob.