Growing up doesn't have to suck

[iamdub]

Correction: I didn't let the test fuel sit long enough. It settled out to show it was 65% alcohol:






A little more than what I was expecting, but also far more than what my Tahoe calculated it to be. To me, it seems like a waste to run it if it's only gonna adjust for 22% alcohol even though it's actually almost three times that.

What scanner showed after filling up with Texaco 93 (either E10 or E0- I'll try to remember to confirm next time I pass there):



...And the fuel trims:

 

[iamdub]

Spent about 4 hours under it this afternoon trying to figure out how I'm gonna do my crazy ass exhaust. Well, about 2 hours of that time was working on the valve. I unbolted the motor drive from it and found that one of the butterflies was really dragging near and at the fully closed position. Used my Dremel to clearance the metal and got it operating about 99% freely. The motor drive must be a torque monster cuz it moved through that interference with ease. I know it'll be fine after some exhaust buildup. I'll just have to remember to cycle it a few times to keep it clean. That shouldn't be a problem, though.


I made cardboard templates of each of the mufflers to figure out placement and orientation. The smaller one I'm currently running is a centered/offset configuration, the long one I'll be adding is centered/centered. I was trying to determine which one should go first and how it and the valve will be clocked. It looks like it's gonna come down to me modifying the cross member for the extra space. That cross member isn't really structural, but I'll still reinforce it after modifying it.

Yes, I'm still working on that damned mower... Sometimes.

So far, I'm thinking this is a winner. Put the bigger one first and angle it and the valve as pictured so that I can tuck it up as high as possible with nothing extending below the frame rails with about 1/2" to spare. The second muffler will be clocked the same. The 3" straight pipe will run parallel. It will be on the ground/far side of the system so the mufflers will act as a sound barrier between it and the floor of the cabin. They will merge together right at the arch that goes over the axle.

I also tested out the DPDT rocker switch on the valve. I'll do all the wiring at the switch so I'll only have to run two wires to the switch (12V+ and ground) and then two wires (+ and -) from the switch down to the valve to have bi-directional control.

 

[iamdub]

Sketched out my exhaust idea. Did overhead and under-from-passenger-side-rear perspectives:

 

[George B]

Correction: I didn't let the test fuel sit long enough. It settled out to show it was 65% alcohol:

View attachment 255851

View attachment 255852


A little more than what I was expecting, but also far more than what my Tahoe calculated it to be. To me, it seems like a waste to run it if it's only gonna adjust for 22% alcohol even though it's actually almost three times that.

What scanner showed after filling up with Texaco 93 (either E10 or E0- I'll try to remember to confirm next time I pass there):

View attachment 255854

...And the fuel trims:

View attachment 255855

Thats odd. Will be watching to see what you lean. I wonder/suspect that it still adjusts the spark advance further due to less knock to too. Wouldn’t the fuel trims balance out over time?

 

[iamdub]

Thats odd. Will be watching to see what you lean. I wonder/suspect that it still adjusts the spark advance further due to less knock to too. Wouldn’t the fuel trims balance out over time?

It's supposed to adjust the injector duty cycle and timing accordingly. E85 has about 27% less energy than straight gasoline, so it takes about 27% more E85 than E0 to operate. My MPG on 93 is around 22 and it drops to around 16 on E85, which is a 27% loss, so that math works out. Yes, since ethanol has a higher octane rating (north of 100 for E85), the timing is advanced. These engines are rated at something like +11HP/13TQ when running E85, and that's why I was running it.

Before this fill-up with the 93, my trims were staying around 9-13ish, which indicates lean. So I'm wondering if, since it calculated the content to be only 22-23%, it didn't open up the IDC to get enough fuel into it and that's what made the trims lean. I still need to find out how it calculates the content in the first place. It shouldn't run lean because the O2 sensors would indicate such and the PCM would adjust. Also, I learned that idling will throw off the trims, and I was doing lots of idling when playing with my scanner to find them numbers.

 

[HiHoeSilver]

It's supposed to adjust the injector duty cycle and timing accordingly. E85 has about 27% less energy than straight gasoline, so it takes about 27% more E85 than E0 to operate. My MPG on 93 is around 22 and it drops to around 16 on E85, which is a 27% loss, so that math works out. Yes, since ethanol has a higher octane rating (north of 100 for E85), the timing is advanced. These engines are rated at something like +11HP/13TQ when running E85, and that's why I was running it.

Before this fill-up with the 93, my trims were staying around 9-13ish, which indicates lean. So I'm wondering if, since it calculated the content to be only 22-23%, it didn't open up the IDC to get enough fuel into it and that's what made the trims lean. I still need to find out how it calculates the content in the first place. It shouldn't run lean because the O2 sensors would indicate such and the PCM would adjust. Also, I learned that idling will throw off the trims, and I was doing lots of idling when playing with my scanner to find them numbers.

Do you know if you have the actual sensor or the "virtual" sensor? I think it happened in 05, but not 100% sure.

 

[iamdub]

Do you know if you have the actual sensor or the "virtual" sensor? I think it happened in 05, but not 100% sure.

Virtual. Yeah, from what I gather, they switched to virtual sometime during the GMT800 era.

I've been doing some reading and found that the calculations can be thrown off by lots of short trips or running higher than 10% alcohol during the calibration/relearn phase. I don't have a way to initiate a relearn but I'm wondering if resetting the PCM would do it. To reset the PCM in my older trucks, I would pull the PCM fuse while it was running. It'd have to relearn idle and all that. I'll have to look this up since I currently have a full tank of 93 that's possibly E0 and plenty of cruising distance around me.

 

[Fless]

@iamdub

Here's the South Main Auto reset on a 2012, not sure it can be done with yours. He resets it around 4:30.

 

[iamdub]

@iamdub

Here's the South Main Auto reset on a 2012, not sure it can be done with yours. He resets it around 4:30.

Thanks, but I don't have a Tech2

However, that did tell me that the calculated alcohol content "overrides" what the PCM adjusts for based off the O2 sensor.

 

[Fless]

Thanks, but I don't have a Tech2

However, that did tell me that the calculated alcohol content "overrides" what the PCM adjusts for based off the O2 sensor.

He did say that other code tools may be able to reset it....