SD and MAF DBW problems

[Gunnin4ya]

On my swap in my 65 I put an 02 5.3 in it with a stand alone harness. I bought an hptuner setup and trying to go sd to get it going. I unplugged the maf and plugged the brown wire from the maf to the iat sensor and black as well. Runs horrible. Goes waaaayyyyy lean when you hit about 3200 rpm. I unplugged the wires and went to drive it again and it ran great. But the iat temp was reading at -38. Which was making it run rich but didn't matter what rpm it ran amazing. I checked the brown wire I hooked up and traced it back. Goes to Red pin 25. Which says it is the iat. What am I doing wrong to not get the correct information? I disabled the po101, 102 to mil on first. If I disable p0103 it disables my dbw pedal. Think this is what is causing it?

[BR3W CITY]

Are you trying to force fail into SD, or are you using the HP Tuners custom OS for 1,2,3 Bar MAP SD?

[davepl]

On a stock LS3 crate motor you can unplug the MAF and drive around all day on a reasonably good SD tune. It's not perfect but it's better than a MAF poorly calibrated to the intake pipe.

Should run just fine and regular with the MAF unplugged. Any chance you've got exhaust leaks near or upstream of your O2 sensors?

This could be totally different based on controller, but that was my experience with the crate LS3 435hp setup.

[Gunnin4ya]

I was trying to get it to fail the MAF, It wasn't working in the DTC's when I put them on MIL on first. Come to find out that my pedal TPS high and low circuit wasn't set to mil on first. I clicked on those after tracing wires and racking my brain to find out the wires were correct. Works like a champ, Now I just have to get started on the VE table and learn mre about HPTuners. I appreciate the help.

[davepl]

I was talking a year or two ago to the actual GM engineer in charge of crate engine calibrations... the topic was the use of a MAF in a crate engine, because they calibrate the MAF long before you ever build your tube, so how can it be calibrated? He was of the opinipon that GM should invest in really getting the SD tune perfect, so people could run without a MAF.

Unless it's a MAF in a calibrated pipe and enclosure, I don't believe in MAFs for retrofit crate engines either.

The best they can do, then, is calibrate it for being in the middle of a 6" straight run. Mine still didn't run worth a damn that way, I had to add those honeycomb laminar flow straightener things, and then it was fine.

In the end, though, i don't know that the final MAF version is any better than the SD version was that first night!

[BR3W CITY]

Dave, I wouldn't hold your breath for that solution unfortunately. GM has put their process focus onto even MORE MAF usage, relying heavily on it going forward.

When GM introduced GMVE/VVE in GenIV, the traditional VE table gave way to the use of GM's VE algorithm and the series of tables it runs. Gen V continues that direction, since the speed of the ECM's has grown exponentially and can run a much much faster correction loop. Going into Gen V-1/2 (not sure if its truly GenVI, since the new 'vettes will run a series of different motors on slightly different design, but the base modelof which still uses E92/E92a computers), its becoming nearly impossible to directly tune VE itself, as it has become entirely reliant on the VVE calculations.

[davepl]

For production motors that's absolutely the right thing, but not for crate motors that have to fit where they have NO control over the intake packaging!

Unless, of course, they come up with a MAF that can read in more flexible ways, but the current one can't.

Part of me says "GM shouldn't foist MAFs on crate engines, they should do it right" but then part of me wonders if the crate engines could be affordable if they were not just copies of the production motors...