Originally Posted by v10viper04

how would it not plug right in? The tbi harnesses are the same... and its the blazer's motor with the blazer comp.. why wouldn't it work? its the whole 7747 ecm hooked up not just the chip...

Originally Posted by v10viper04

What are your inputs on data-Logging software? What one do you guys use and which one is the best?

Originally Posted by RFmaster

WinALDL
ScannerPro
- both should work well with 7747ECM.
A word of caution - NBO's are not very accurate at fuel mixtures away from 14.7:1. WBO is the next best thing to dial in WOT performance.

ECM comment
A stock 7747 can be equipped with EBL which can support extended RPM operation or convert to later PCM
//RF

Originally Posted by Fast355

I can think of a couple of reasons that you are having problems.

1st, the 700r4s in the TBI trucks were calibrated to upshift by 4,200 rpm or so. The injector pulsewidth is pretty much maxed out by about 4,000 rpm. Running much over the WOT Upshift RPM of a TBI truck will make the injectors run static.

2nd, the ignition control modules used in the cars and some trucks have a built-in spark latency change as the rpms increase. This was done purposely to limit the maximum rpm of the engine. What happens is as the engine runs over 4,300 rpm, the timing starts to retard until around 5,000 rpm it peaks around 9* retard from the latest entry in the spark table.

3rd the camshaft and valvetrain in your L05 unless upgraded were designed to run with the 4,300 rpm WOT upshift in mind. The cam was a very mild grind and the factory engineers wanted it to live a good long life. Being a hydraulic flat-tappet cam the engineers used valve springs better suited for childrens slinkys. The later model TBI trucks even had a 4,800 rpm fuel shut-off programmed into their PCMs.

Originally Posted by v10viper04

That sounds like the exact problem... when the rpms get high it runs like crap and looses all power. How can i get around that? My next mods are cam and heads. I was gonna have my ECM "reflashed" by some guy where you send in your ECM and he reflashes them for $50. Then sends it back. Any ideas? and how hard is it to change a camshaft?

Originally Posted by RBob

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:


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.


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.

Originally Posted by Fast355

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.



A camshaft swap is fairly easy, but takes some mechanical knowledge and lots of time. Its not something that you would want to do in a single weekend.

I doubt that a mail order tune is going to help you any. You really need a larger camshaft, better valvesprings, and a non-mail order retune of the ECM.

Originally Posted by v10viper04

Well i swapped out the Truck ECM for a buick roadmaster ECM and my top end power is back it pulls all the way to 5500 rpm, But to really gain the benefits from that particular ECM i have to get bigger injectors right? B/c the roadmaster L05 used bigger fuel injectors than the truck L05's right?

Originally Posted by v10viper04

someones gotta know about camshafts here.......... I know there is someone here lol

Originally Posted by kdrolt

Probably not.

The RM LO5 was rated at 180 fwhp during 1991-1993; truck LO5 were at 195 or 210 fwhp (not sure). The trucks had a different (flat) tappet cam that was slightly warmer than the peanut cam used on the RM 350 (same peanut roller as used on 3rd gen Fcar 305), and a better exhaust, so they were rated higher and MAY have used something higher than 61 #/hr.

So IMO they either used the same (flow rating) injectors, or the trucks got slightly larger ones.

Originally Posted by DM91RS

2.73's ?

Originally Posted by v10viper04

i am still irritated, i feels like its running good but its still putting down upwards of 8 sec 0-60's, i just took a vid from 15mph -60mph and it takes 8 secs. thats terrible! Any ideas? I'm starting to want to just give up on it.

Originally Posted by Fast355

When in doubt go back to the basics. The engine requires several things to run properly. Adequate compression, a good air/fuel mixture, and a properly timed spark. Partially deprive it of any of the preceding and the engine will still run, but will run poorly.

A.) Check the Compression
B.) Check the cylinder leakdown
C.) Check for proper valve action
D.) Check the ignition timing
E.) Ensure that you have 61# 350 injectors in the TBI unit
F.) Test the fuel pressure to make sure you have atleast 12 psi (Spec is 9-13)
G.) Measure the backpressure on the exhaust system during a WOT 2nd gear pull (should be less than 3 psi)

The cam in that engine is VERY small and does not respond well to minor bolt-ons. I mean the intake valve is only bumped off the seat .350" and the exhaust valve .385", it is also not at peak valve lift for any time and the ramps are not all that aggressive. A LT1 cam, a full exhaust, and a properly tuned ECM will wake this engine up incredibly. I ran a LT1 cammed L03 (added flat-top pistons) truck engine on the stock 1992 Van ECM in my van with the only other additions being headers and a 2 1/2" dual exhaust system. The van HAULED BUTT! Easily ran 0-60 in 8-9 seconds despite 3.08 gears and the stock 1,600 rpm torque converter.

http://youtube.com/watch?v=UEeZ5ruugWA

http://youtube.com/watch?v=PX5Av4pS1RA

This is a stock 4,200 lbs Buick roadmaster which uses something near a 2.56 gear. 0-60 in 9 seconds (12-3=9)

http://youtube.com/watch?v=1U7O-U4EF00

Originally Posted by v10viper04

i was told before that i should be getting 7-8 sec 0-60s with the setup i have right now, which i assumed was including the 2.73's.
----------


Your L03 RS has 3.73's right and a T5? Whats your 0-60 time?

Originally Posted by DM91RS

I don't know but I'll bet with my one wheel peal it will spin forever if I tried. I'm working on a Torsen and a bit lower gears which might let me try soon. My engine has alot of miles and it's my DD so I don't beat it too hard anymore until I get a fresh short block in it....BUT it does pull strong for what it is IMO so it might not be too bad. I do remember that the same engine with the same mod's [full exhaust], but with a 2.73 and auto was a dog compared to the 5 spd/3.08. I hated the auto/2.73 combo. It was in an 89 RS.