Truck falls flat after 3000 rpm.

[joegreen]

Hello, I have a 78 350 swapped to tbi. I have been tuning the ve table for a few days. It has a th400. If i put it into second gear and floor it once it hits 3000 rpm it feels like i am driving into a massive head wind. It wont really go past 3000 rpm when floored. My camshaft is pretty worn and was wondering if that could cause that issue. Below is a picture of my average blm's on a 20 mile drive and my ve table graph. Looking at stock ve graphs it looks like the graph ramps up from idle to 3200 rpm where as my graph makes a big dip around 2000 rpm. Is that an issue. I have been making the ve adjustments using daves excel spreadsheet. So i guess my question is is does the ve graph look like it has a problem or could it be shaped like that because of my worn camshaft or does the ve graph look fine as long as the blm"s are ok?

[joegreen]

Also i tried all types of searching but i cannot find out how to turn off open loop idle so it idles in closed loop. The open loop idle is throwing off my blm measurements when idling in traffic.

[Fast355]

I am going to guess it is likely timing related. The old heads need a good 8-10° more timing across the board than the TBI heads. Once you fix the lack of timing I am sure your VE fuel tables will look massively different. Dpes the truck still have the old pellet box cat on it?

[joegreen]

What is a pellet box cat? catalytic converter? Ok so ill start messing with timing? I tried looking through all the parameters but could not find a way to tun off open loop idle.

[Fast355]

What is a pellet box cat? catalytic converter? Ok so ill start messing with timing? I tried looking through all the parameters but could not find a way to tun off open loop idle.

Would probably be easier to just swap to a different .bin that had closed loop idle. Fixing your .bin requires altering numerous constants.The pellet box catalytic converter is a horribly restrictive catalytic converter, cat for short that GM started using in the mid to late 70s. .

[joegreen]

this is the .bin that i am currently using. Truck is a 3/4 ton with no emission anything. I am using the 1227747 ecu

[Fast355]

this is the .bin that i am currently using. Truck is a 3/4 ton with no emission anything. I am using the 1227747 ecu

I will have to look at it when I get off and get home to my tuning software tonight. Are you using the ECM to control the kickdown or is it still on the kickdown switch on the gas pedal? If you are still using the pedal switch, try ASDU as a staring .bin. I know it has closed loop idle.To answer your question a flat cam will cause the engine to fall on its face at higher rpm. You could get away with a cam like the Mellings MTC1 in your engine with the TBI.

[joegreen]

i took the kickdown switch out and have not hooked up the ecm kickdown wire yet. Its on my list of thinks to do. Right now i just manually downshift if need be.

[joegreen]

I measured the lift of each cam lobe that's how I know my cam is worn. I am going to replace it but right now this vehicle is my daily. Here are the numbers I measured.

[joegreen]

I see the ASDU bin mentioned alot in various posts and forums as a recommended starter bin. Should I be using that instead of AFBW? I chose AFBW because the tbi system I pulled off a 1987 k30 with 5.7 had that bin in the ecm. I figured it would be the closest stock tune for my 1978 k20 with 5.7. If i do go with ASDU can I still control the th400 kickdown. I see in the long list of bins for the 7747 that some are for 3 speed auto and some are for 4 speed auto and some are for manual. Can I only use the 3 speed auto bins? How can I tell if a bin has closed or open loop idle?

[mmigacz]

I see the ASDU bin mentioned alot in various posts and forums as a recommended starter bin. Should I be using that instead of AFBW? I chose AFBW because the tbi system I pulled off a 1987 k30 with 5.7 had that bin in the ecm. I figured it would be the closest stock tune for my 1978 k20 with 5.7. If i do go with ASDU can I still control the th400 kickdown. I see in the long list of bins for the 7747 that some are for 3 speed auto and some are for 4 speed auto and some are for manual. Can I only use the 3 speed auto bins? How can I tell if a bin has closed or open loop idle?

The ECM will only be controlling the kickdown relay. The other parameters relating to torque converter locking and unlocking will be disabled. In other words, it doesn't matter if its a 3 or 4 speed. Not that long ago I found a good thread on how to do this. I posted it at the bottom........Look at the table open loop - rpm threshold. If the values listed in there are unattainable, the bin is set for closed loop idle. The ASDU should work (with modifications).................................... .................................................. .................................................. .................................................. .................................................. .................................................. ..........................http://www.thirdgen.org/forums/diy-p...47-8746-a.html

[joegreen]

When i look at the open loop rpm threshold table it has an idle off rpm and an idle on rpm. When you say unobtainable do i set them both to zero rpm or 10,000 rpm to lock out open loop idle?

[mmigacz]

Set idle off to 25 and idle on to 50.

[mmigacz]

Set your TCC parameters like I show in the attached picture. The parameter that is circled is the one you want to play with. Currrently, it will energize the solenoid (and downshift) when the throttle percent reaches 85%. Change it to whatever you want.

[joegreen]

Im going to try out the ASDU bin and see how that goes. I was tuning ve before by combining table 1 and table 2. I know its user preference but i thought i read something about leaving some values in table 2 because some other table or something looks at table 2 and if its zeroed out it cant read it, idk. Can i still tune using daves excel spreadsheet by just using ve table 1 and leaving table 2 alone. Also why does ve table 2 go up to 6400 rpm when ve table 1 only goes up to 3200 rpm? Thanks for everyones help so far.