2004 Yukon SLT 4WD L59 E85, Power increase?

[Police428]

I own my 04’ Yukon SLT. I know that my truck is E85 compatible as it has the Z code on the VIN. My question is, 100% stock. How much power does running E85 add to the tires compared to
normal 87. If it does add power, is it worth running it?

 

[corvette744]

Wont add any power unless you have higher compression pistons-its just a higher octane rating of 100-105.Your engine is 9.5 to 1 compression wont do anything but get worse gas mileage.

 

[swathdiver]

I own my 04’ Yukon SLT. I know that my truck is E85 compatible as it has the Z code on the VIN. My question is, 100% stock. How much power does running E85 add to the tires compared to
normal 87. If it does add power, is it worth running it?

Don't know if the L59 gets more power burning ethanol, it does on the Gen IV 5.3 motors. It's a tuning thing.

These motors love running on the stuff. It's like cheap race gas that cleans the injectors, heads and pistons. Endurance is less but if the cost variation is enough, it can sometimes come out less expensive to operate per mile.

I mix my fuel at the pump in an attempt to reach a desired alcohol percentage and octane rating for maximum power which yields even better mpgs than running straight gasoline. These motors do well running 15-20 percent or so ethanol content.

18 gallons of 87 @ 5% ethanol content and 4 gallons of E85 @ 80% ethanol content yields about a 90 octane rating and 19% ethanol content.

if you run one tank and switch back again, you'll never get to really experience the benefits of using it. The motors run smoother and cooler too.

 

[1BADI5]

My built LMG I picked up a huge 4rwhp/4ftlbs on E45, on Full E85 maybe 10/10 max.

The real gains with E85 are with forced induction, then you can see 25-100+ at the rear wheels

 

[Mudsport96]

Green manifolds and 93 octane
Red headers and 93 octane
Blue headers and about e50

 

[Mudsport96]

Here is the video i took the graph from

 

[1BADI5]

^^ well those 2 post pretty much confirm what I said, and I have heads, cam a bunch more beyond headers and tuning

 

[corvette744]

Green manifolds and 93 octane
Red headers and 93 octane
Blue headers and about e50
View attachment 347359

So what im seeing is he gained 1 horsepower and 1 ft pound of torque using e50 over pump gas 93 and headers.I would be interested in seeing e85 vs e50 but he is bumping timing 4-6 degrees over stock also.The original op is not going to be using his laptop and bumping timing i assume.So no gains in my book-especially if he is not running it forever and goes back and forth with pump gas 93.What i am shocked at is how much horsepower and torque headers gave the stock tahoe 41 hp 39 ft pound of torque.Im stunned if this is normal i will go buy headers right now.Thats as good as a cam swap or head mods in my book.Very nice gains.Anyone know what headers are making this power so i can look into it.I agree it will make it run cooler but without mods compression or forced induction stock motor its not going to make any difference.I need to see a stock manifolds e85 test why didnt they do that-that would solve the mystery.One more question if i install headers do you have to get the ecm tuned also or bolt up and go.Seems like tuning is giving some power here not just the headers.

 

[Mudsport96]

Pretty sure its long tube headers and offroad y pipe. You should watch the video, i think he explains it all

 

[corvette744]

Pretty sure its long tube headers and offroad y pipe. You should watch the video, i think he explains it all

I watched the video 3 times then went in to his channel.Found the headers 1 7/8 inch for forced induction and off road pipe your right.No cats here in illinois wont fly emission test every year.Impressive power gains with that set up though.Again original question was how much power will e85 add to a bone stock 5.3 over 87 octane im still going with nothing except worse gas mileage by at least a few mpg.I ran it in my 2012 silverado bone stock for almost a year when it was $1.75 a gallon and gained nothing that i felt but never dynoed it.