Just wanted to mention that my 305 is running on the EBL now, repinned from the TBI PCM. Just wanted to know if the setup would run on the Edelbrock 7747 BIN that I have, IT DID. I then swapped over the EBL and am currently playing with it. Runs VERY well, with a few exceptions. It has a rough idle, even in open loop with stable timing readings.

A.)The A/F mixture drifts slightly at idle in open loop as various loads are placed onto the engine and removed that do not signifigantly affect MAP.

B.)The VE table is taking on a heavy U-shape, which means I need to mess with the injector correction offset table, but which way do I adjust them.

C.)I tried closed loop, but the engine idles very roughly once it enters closed loop. I have not been able to correct the closed loop idle surge using the idle term proportional settings. Open loop brings much improved operation.

D.)Highway mode will not function running fully in open loop.

E.)I have pulled tons of MAP AE out of it and added TPS AE, but the engine still has a VERY LEAN tip-in followed by a massively rich MAP AE burst that causes a slight bog around town. At higher RPMs, (above 1,500 RPM), when the pedal is snapped down, it HAULS.

F.)It is too darn easy to cruise 80-85 MPH, even more, and I was pulled over doing 88 mph in a 70 mph zone. Got a stern warning and the highway patrol officer let me go.

 

Fast,

Have you tired playing with the O2 Window Terms for idle?

 

Yes, I have, it is within the window terms, meaning the resultant A/F ratio is where I want it, it just swings too widely. So much so that the integrator starts swinging as well.

 

The wide swings may be due to too much prop gain. I know you usually run high FP. Drop the Prop Gains for idle. See how that works.

 

That is what I am saying, I have dropped the gains, played with them etc. It is a TPI setup, so the injectors have ALOT of flow anyway. I am running 98# worth of injector on each bank. 24# LT1 injectors @ the stock 1986 TPI units 46 PSI. I have everything else dialed in pretty well, its just the proportional gains or the stock LT4 cam would not get along with the PLX widebands, narrowband output.

 

Fast355

Why is your main bus DC is 12.5Vdc - do you have a single wire alternator? I also have a little bit of surge at idle - where in TP do I change prop gain?

//RF

 

The Alternator charges through a Battery Isolator (Dual batteries, one for my Inverter and all the DC loads in the Van, and one for Engine starting). The diodes in the Isolater eat up about 1 volt. I have been meaning to add a resistor to the voltage reference going back to the alternators regulator, to bump the voltage up an additional 1-2 volts to compensate. The house battery was nearly dead on Saturday as well.

I am suprised you didn't mention, my new AC Delco thermostat that is stuck open (haven't changed it yet because it is going to be a real PITA, that might require removing the upper plenum).

What ECM are you running and I can walk you through the proportional gains tables.

 

Fast
I am running EBL Flash based on 6965 ECM with a TBI. It works like a charm straight out of the 'box', but now I am getting into fine tuning...

//RF

 

OH, Whale Body B-car TBI, nice cars.


I pulled this from the EBL tuning guide.

EDIT- Posted this pre-maturely, but now I have corrected it to reflect what I wanted to show.

You want to try to reduce the swing, I would do it by shortening the duration of the added fuel shot at idle and the GM/SEC reading where it is surging.

 

Fast355
Dahh - Should have looked at the manual first. Yes, B-Cars make excellent TBI donors for '70 trucks - same weight category!

This is my EBL configuration. So, I guess I can drop idle prop gain from 5 in 10% steps until I see idle stabilization..

//RF

 

LOL, I've got a 1980 C10 that is powered by a 1991 L03 from a TBI Cadillac Brougham.

I would drop both the gain and possibly the duration. Both affect how much the swing is. If it dips and rises very suddenly, very sharp movements, adjust the gain. If it translates rich or lean over a second or so, I adjust the duration.

Also, if you are idling in Park/Neutral in that snapshot, you need to increase your minimum idle air adjustment (open the throttle plates more). In Park/Neutral with the engine WARMED UP, A/C OFF and all heavy electrical loads OFF, I like to see no more than 5-10 IAC counts on a TBI setup. Having the IAC bypassing too much air, is just like a Vacuum LEAK on a TBI setup.

IAC = Vacuum leak

 

Ok.... Will do thanks for the tips - it is a bit late to do it tonight - delta 40's are not exactly quiet with dual 2-1/2 system.
Will re-park IAC (quasi controlled vacuum leak) first to make sure. No AC on my 3/4 ton, just a simple heater an plenty of metal to go around. GN, will report later.

BTW, my '75 C20 conversion was based on 91 Caprice TBI (with 65lb injectors). B-car harness is longer than truck so it makes for easier routing when needed. What a huge difference in performance and fuel economy - 18 mpg at about 65 mph (6500 lbs)

//RF

 

HAHA, my van has Delta 50s on it with 2 1/2" pipes and headers, I know what you mean.

I used a VAN harness in my C10 for the same reason you stated.

My van got 15.9 mpg running 75-85 MPH with LOTS of WOT acceleration to cruising speed, over nearly 300 miles this weekend. The calculated MPG and actual at the pump was 0.25 MPG less. I used less fuel than the display calculated, but not by much. I tweaked the flow constant by the percent off it was, maybe it will be dead on this time.

My Van was about 5,300 lbs empty. Its 5,550 with me in it. Add in 400-500 lbs of stuff and I am at 6,000 lbs too. Add in a passenger or two and I get to 6,500 lbs VERY quickly.

 

Man you always pound out impressive MPG numbers. I am still stuck around 13 on the freeway.. Could be all the engine though. Got to love those stuck open thermostats.. haha.

 

One thing about the TBI ECMs is that they will fire the injectors 2-4x more then whats needed, which really shrinks the pulsewidth. In batch or alternating fire, you really only need to fire all the injectors once per every one or two revs to fuel the cylinders. Also, did you mod the injector drivers yet? Not sure how the drivers will behave and whether or not they will stay in saturated mode or enter P+H. Depends on what the total resistance and current flow is.

 

So what happens if you go back to using a stock NB? Update rate of INT?

 

I think you need to raise the bias to add more pulsewidth in at low PW region so you dont have to do it in the VE table. Ive seen this a little with the TBI injectors when theyre in the microsecond region, but it may even be worse with the MPFI injectors.