K3500 Gearing

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Pinger

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What I'm not getting here is that you guys seem to know when it goes PE while driving - or do you just know it will?

I still don’t understand GM’s logic behind setting the delay on PE to 60 seconds and then when PE does come in it dumps fuel at 11.5:1 afr which is way below optimal power afr. It makes no sense, but surely they have their reasons. It’s not like the optimal afr for power wasn’t figured way before the 1990’s.

This is age old. When radiators were still made of soldered brass (read expensive) under-specifying the cooling capability and 'fuel cooling' was the norm. It still is to some extent principally to pull in-cylinder temps down to resist detonation. The cooling of the incoming air by giving up heat to vaporise the additional fuel will increase its density which can increase power.
 

Supercharged111

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My trucks have widebands and they're both programmed to enter PE before a downshift from 4th.
 

andy396

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11.5:1 will produce more torque than 12.5-13:1 and provide more cooling.

So I guess this means I shouldn't have leaned out my PE from 11.5 to 12.5 if I'm going to be taking on heavy loads for more than 60 seconds? (i.e. pulling a trailer up a grade)

What I'm not getting here is that you guys seem to know when it goes PE while driving - or do you just know it will?

If I understand your question correctly, I think the answer is we know when it goes into PE because we've looked into the factoring tuning and/or modified the tune.

This is age old. When radiators were still made of soldered brass (read expensive) under-specifying the cooling capability and 'fuel cooling' was the norm. It still is to some extent principally to pull in-cylinder temps down to resist detonation. The cooling of the incoming air by giving up heat to vaporise the additional fuel will increase its density which can increase power.

I wonder if this holds more true for carbs and TBI's vs multi-port. Multi-port doesn't have as much runner length to vaporize the fuel and more relies on the atomization of the injector.

So now I'm feeling really guilty for dragging this so far off topic. Maybe start a new thread?
 

Supercharged111

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The only way I could see 11.5 creating more torque is if you ran more timing and actually beeded the fuel to hit MBT timing.

It's in a tuning book, I can get a snapshot when I get home. I run mine in the 11s because of the heat of the blowers. I know timing is a part of it.
 

L31MaxExpress

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It's in a tuning book, I can get a snapshot when I get home. I run mine in the 11s because of the heat of the blowers. I know timing is a part of it.
Interesting...I have never seen this on a dyno. On E10 I usually find peak torque around 12:1 and higher rpm around 12.6 on Chevy small block heads. The 8.1 is said to run best around 13.4:1 at high rpm although I have it in the 12.6 range as well for cooling.
 

Pinger

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My trucks have widebands and they're both programmed to enter PE before a downshift from 4th.

If I understand your question correctly, I think the answer is we know when it goes into PE because we've looked into the factoring tuning and/or modified the tune.

I think you have understood my question and if I've understood the answers.... you guys are re-mapping the stock ECU (PCM) - yes? Or is the PE programmed in and you are just monitoring it?
 

Pinger

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I wonder if this holds more true for carbs and TBI's vs multi-port. Multi-port doesn't have as much runner length to vaporize the fuel and more relies on the atomization of the injector.

What I was referring to was from way way back. I think (or thought) it ended around late 80s early 90s (if not before) when manufacturers got their act together to improve fuel economy (MPI, electronic transmission control, etc). But, 'fuel cooling' was never really dispensed with and the downsized turbo units are pretty reliant on it to contain temps and thus detonation (otherwise lower boost and/or CR is required). I'm just surprised it plays such a part on these big unstressed NA V8s. It also has me wondering where I stand with my 5.7 Vortec as it runs on LPG and although it could be richened, introducing the LPG as a vapour not a liquid removes its cooling properties. It would (or should) help speed up combustion at least - welcomed with LPG.

So now I'm feeling really guilty for dragging this so far off topic. Maybe start a new thread?

I'm new here - but a bit of thread drift isn't so bad - IMO!
 

JavaMan

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What I'm amazed by is that with all the pressure on MPG ratings over the decades that they still use excess fuel to cool anything. They added a DEF tank to diesels years ago. Why have they not added a water tank, inject water into the cylinders to help cool the engine.
Some high MPG experimenters have used water for years to help increase MPG and power by decreasing intake temperature as well as taking advantage of how much water expands during vaporization.

Sent from my SM-G965U using Tapatalk
 
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