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

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!:mad1: 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

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

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

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

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Originally Posted by RobertISaar

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

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

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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

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.

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

Quote:

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Originally Posted by 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

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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

dave,
just to throw this out here the previous owner/tuner could have tuned it for operation in 4lo. useing 4lo considerably changes the load on the engine. I know on our shops big race truck we dyno and tune it in 4lo.

Hard to feel a TCC lockup in a truck with 46 inch tires but it is being commanded on at as low as 37 MPH that's got to be thrid gear. Maybe allow in OD at higher speed/higher RPM if the truck can handle it, like above 55 MPH if VSS is correct?... Looks like all TCC paremeters were changed to a 700R4 bin from that Turbo 400 bin...

BLM pig rich bottomed out 108 at idle. Goes good mid, goes lean upper made me look at BPW and sure enough it was raised from stock 135 to 155. This is exactly what happens to BLM when BPW is tweaked beyound a few digits. I've increased Injector Bias by as much as 50% instead with good results if some more fuel is needed but again fuel pressure is a better way with BPW calculated. Higher pressure = lower BPW.

Error code 43 is set and not a single knock count during the log, so knock system is not working... not good with that timing table and 46 inch tires, 4:88 gears work well with 36-38 inch tires, I'm guessing you'd never hear knock in that truck.

Idle is low 40s MAP at 800ish RPM so I'm guessing a cam at your elevation? Stock would be lower with no vacuum leaks. Problem with idle is IAC counts in 90s! TPS voltage .33? Throttle blades need to be opened up to let fuel mix with air/lower IAC count/raise TPS voltage to .54ish. They may have closed throttle blades in attempt to lower idle? Totally warmed up and driven IAC counts under 20 is where I shoot for.

That really makes me think distributor base timing has been messed with as well? Curious where you find it. I'm tuning a truck right now that had a mail order tune done and timing was said to be set at 8 BTDC, it was 8 ATDC? Looks like the timed it without disconnecting bypass wire... 0 works well with modified Vortec timing table to go with these Vortec heads and 9.4 : 1 compression and cam.

Not sure how the Shifter Postion will effect the tune? Since it has VSS... or what the difference is between turbo 400 and 700R4 wiring is to fix that issue?

Mark,
That's about the same write up I gave the customer. His comment was "Fix It". The customer has a modest budget, so fix it I will! I'll post back with what I end up doing. For the time being, I'm going to disable EGR, disable ESC, inspect injectors (maybe some OEM numbers are on the injectors?), check timing, and check, fuel pressure. I'll start with a modified stock tune (7.4 engine parameters / 5.7 liter 700R4 parameters),and go from there. I have a vacuum referened fuel pressure regulator in reserve, if needed to fix the rich idle / lean upper RPM. It's going to be a long weekend.

I've had good results increasing BPW to about 145 on some '7747 applications.

dave w

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Originally Posted by PJG1173

dave,
just to throw this out here the previous owner/tuner could have tuned it for operation in 4lo. useing 4lo considerably changes the load on the engine. I know on our shops big race truck we dyno and tune it in 4lo.

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Once I get the 2WD tuned, I'll test 4WD Lo, good thinking!

dave w

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Originally Posted by dave w

Mark,
That's about the same write up I gave the customer. His comment was "Fix It". The customer has a modest budget, so fix it I will! dave w

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Truck does not sound like a modest budget? Maybe funds were mis apprproiated on engine, tires, suspension and gearing and forgot a tune?

Maybe he can cancel a remote location journey to pay and get the truck running? Just one trip at 8 mpg tops would pay for the tune day with me...

You won't find much to be had from a 4lo tune espeasilly this ECM, I can't even see a dyno work in 4lo with 46 inch tires or a dyno owner trying? Those tires would only need 20PSI for the street, drop them down to 10 for a load on data.

I've noticed in some OBDII cals that torque managment really restricts 4lo, probably to save drivelines. Real easy to break any and everything in driveline 4lo... double torque.

Quote:

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Originally Posted by EagleMark

Truck does not sound like a modest budget? Maybe funds were mis apprproiated on engine, tires, suspension and gearing and forgot a tune?

Maybe he can cancel a remote location journey to pay and get the truck running? Just one trip at 8 mpg tops would pay for the tune day with me...

You won't find much to be had from a 4lo tune espeasilly this ECM, I can't even see a dyno work in 4lo with 46 inch tires or a dyno owner trying? Those tires would only need 20PSI for the street, drop them down to 10 for a load on data.

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This thing is so "over-the-top", it is most likely towed on a flat bed trailer to the play grounds. It's so "over-the-top" ramps to load / unload on a flat bed trailer are optional!

My idea of modest might not be the same as yours. I won't earn a full mortgage payment for my services, but something close.

dave w

I thought the modest budget meant he spent all his money and couldn't afford a tune...

How much motor work is done? Your lucky it seems to have the fuel to support WOT to begin with. That is usually overlooked on builds... should actually be easy with this done.

Pics as promised.

dave w