Very unusual '7747 .bin ~ 7.4 liter / 700R4

[dave w]

I've been asked to tune an 88 Suburban 4x4, TBI 7.4 liter / 700R4. The Suburban has 46" tires, and many other upgrade$. The attached .bin files are what I currently have. As best I can figure, the original engine was a 5.7 liter not the 7.4 liter that is in the Suburban. It's very apparent the "Read" .bin is nothing like the AKUN .bin found here: http://www.gearhead-efi.com/Fuel-Inj...Information-42 . I've installed the WBO2, and found the PE is almost a perfect 12.5 AFR, but not much else is close. I suspect the vehicle has been on a dyno? I've posted the "Read" .bin because it's so very different from anything I've ever encountered!! The vehicle owner has stated, "this thing just doesn't run right... FIX IT!"

Earlier this year, I thought a Supercharged TBI 454 with a '7060 was a challenge. This Suburban is a '7747, now that's a challenge! I'd like to upgrade the ECM, but the vehicle owner travels to some very remote areas and getting service and/or parts is a concern.

I'll get some pic up tomorrow.

dave w

[Six_Shooter]

It would probably be easier at this point to find a '7427 than a '7747, if the need for a replacement ECM ever arose.

[RobertISaar]

53* of advance?!??! at low load, but still....

i took a look..... almost every single byte of calibration has been changed....

[dave w]

53* of advance?!??! at low load, but still....

i took a look..... almost every single byte of calibration has been changed....

I've read a few aftermarket TBI Chips, and have seen +45* of advance in a couple of them. Seems to me the math of a V8 distributor cap would limit no more than 45* of advance.

dave w

[RobertISaar]

it's possible that some tables/scalars used to skew the advance downwards for whatever reason(coolant temp?) could mean 53 in the table could come up to somewhere near 45 in real-world.

but that max advance scaler would definitely be getting checked against and probably used when it gets near that range.

[EagleMark]

Max timing allowed in a V8 distributor is 41.84 degrees allowed in most bins and this one is not changed. So 53.79 - 9.84 = 43.85 and cut back to 41.84

Warm Spark bias is 9.84 on small block and this one is a small block starting bin with 9.84 so take that off the entire timing table. When you start with a BB bin there is 0 warm spark bias.

AE is very differant on a stock BB to SB and this one is still stock SB. Can't see how a motor would run well with less then stock AE?

Max timing in the Read bin Spark table is 28.12 minus the 9.84 bias is 18ish total timing? Now there is some big changes in actual timing because SB Spark Latency is differant in spots up to 6 degrees to actual to SB. Still don't know why GM did that? Wonder why I always say "So where is your actual timing?" But 18 is hardly max timing in that motor...

That spark table sucks! Where is distributor set? Bin says 0... Idle timing up to 33 minus bias is 23, stock BB motor is 20.04, so not much idle timing change for a stock BB engine and only 2 degrees at WOT max...

Fuel is even worse. Just add up VE1 and VE2 and you'll see he is out of fuel at 100% near 1200 RPM up at WOT.

A real question would be if TCC is working? On 46 inch tires I would not use it unless it's not loaded and has 5.xx gears, but is it being controlled and how? That bin was for a turbo 400. I did build a ASDU bin to 7.4L 700R4 with lean cruise and ESC test done if you want it? (Forget lean cruise on that truck...) If that has a knock sensor then with an aggressive timing curve the ESC test will sure make it rattle when it goes off. It adds 11 degrees for first test and 22 for 2nd test if first fails... rattle rattle... knock retard only takes out 8.xx

The PE AFR has been worked on in that Read bin so that may be the only reason WOT is tuned in...

Here's an updated $42 xdf as the last one I think you got had an issue with Main VE only allowed to 40% lowest... The stock ASDU for 700R4 changed all engine paremeters to 7.4L

[dave w]

Max timing allowed in a V8 distributor is 41.84 degrees allowed in most bins and this one is not changed. So 53.79 - 9.84 = 43.85 and cut back to 41.84

Warm Spark bias is 9.84 on small block and this one is a small block starting bin with 9.84 so take that off the entire timing table. When you start with a BB bin there is 0 warm spark bias.

AE is very differant on a stock BB to SB and this one is still stock SB. Can't see how a motor would run well with less then stock AE?

Max timing in the Read bin Spark table is 28.12 minus the 9.84 bias is 18ish total timing? Now there is some big changes in actual timing because SB Spark Latency is differant in spots up to 6 degrees to actual to SB. Still don't know why GM did that? Wonder why I always say "So where is your actual timing?" But 18 is hardly max timing in that motor...

That spark table sucks! Where is distributor set? Bin says 0... Idle timing up to 33 minus bias is 23, stock BB motor is 20.04, so not much idle timing change for a stock BB engine and only 2 degrees at WOT max...

Fuel is even worse. Just add up VE1 and VE2 and you'll see he is out of fuel at 100% near 1200 RPM up at WOT.

A real question would be if TCC is working? On 46 inch tires I would not use it unless it's not loaded and has 5.xx gears, but is it being controlled and how? That bin was for a turbo 400. I did build a ASDU bin to 7.4L 700R4 with lean cruise and ESC test done if you want it? (Forget lean cruise on that truck...) If that has a knock sensor then with an aggressive timing curve the ESC test will sure make it rattle when it goes off. It adds 11 degrees for first test and 22 for 2nd test if first fails... rattle rattle... knock retard only takes out 8.xx

The PE AFR has been worked on in that Read bin so that may be the only reason WOT is tuned in...

Here's an updated $42 xdf as the last one I think you got had an issue with Main VE only allowed to 40% lowest... The stock ASDU for 700R4 changed all engine paremeters to 7.4L

Mark, I really appreciate the files you posted! The vehicle has 4.88 gears. I agree 5.xx would be a better choice. I have not felt the TCC lockup. The attached .xdl is from my first assessment test drive, after installing a 3 wire O2 sensor. The .xdl shows the vehicle is always in park.

dave w