2008 GMC Envoy Denali

[THEFERMANATOR]

You can always decap them. That should get you around 80-100 lb/hr out of them. I'm on the hunt for a set of L59 injectors to put in mine. My marine intake uses LS1/6 style injectors, but with ev6 plugs. So the L59's are drop in's, but flow 33 or 35 lb/hr which will handle anything I will do with it, and drop right in.

 

[n8in8or]

You can always decap them. That should get you around 80-100 lb/hr out of them. I'm on the hunt for a set of L59 injectors to put in mine. My marine intake uses LS1/6 style injectors, but with ev6 plugs. So the L59's are drop in's, but flow 33 or 35 lb/hr which will handle anything I will do with it, and drop right in.

Interesting. I hadn't heard of decapping them before. I'll keep that in mind. Thanks for the tip.

 

[n8in8or]

I was talking to a friend of mine at work today about the Envoy and he suggested trying to plug the cylinder deactivation solenoids in and see if that makes it run a little better. Sounded like it was worth a try! So I disassembled them from the plate and plugged them in. I also unhooked the battery to reset the computer. Well it still isn’t happy and is dropping cylinders, but at least now it stays running in gear....though it still won’t go above idle in gear. At least I should be able to drive it onto the trailer which will help me out on Sunday when I load it up to take it to the tuner.



After that I switched back to the air intake. I cut the ID of the air filter so it will now accommodate a piece of 4” exhaust pipe.



This pipe is just stuck in it for illustration purposes - something else will be in here eventually.



Then I found that a piece of flared 4” was perfect for fitting in the original MAF clamp/grommet so I cut a small piece that is a perfect adapter from the MAF to the 4” silicone elbow.



More to come.

 

[n8in8or]

Finished the intake today. Overnight I was thinking about the air filter connection and decided that using a piece of the bead rolled tube to help keep it in place would be a good idea, so I did that first today.



Then I applied a thin layer of The Right Stuff to the inner surface of the filter. This was a can of it I bought a while ago and to my surprise it was gray! So it didn’t blend in with the rest of the filter, but that’s ok....it isn’t a show truck I guess. Then I smeared it on the outside of the aluminum tube before sliding the silicone tube on and clamping it.



Then I moved on to trimming the silicone elbows and the aluminum tube.

I also drilled a hole in the end of the air filter for the Intake Air Temp sensor. Factory the IAT sensor is part of the MAF sensor, but it can get heat soaked in that location so it’s common to get a separate sensor for reading the temps. I got a breakout harness that was pre-made for the relocation.



In the end it turned out pretty well.



With a little trimming I was able to reinstall the factory cover. At some point I will do some insulation to keep engine heat out and help funnel outside air into the filter. This is just phase 1 though....at some point I will make an extended intake that goes through the washer solvent tank, through the inner fender well and grabs air from behind the bumper for a fresher air charge.

 

[n8in8or]

Today was a gratifying day. The Envoy got its face put back on! But first I realized that I had forgotten to extend the ambient temp sensor harness when I relocated it, so I did that after installing the front bumper cover.



Then it got the rest of it’s face....that felt good!!



After that I drained the 6 month old gas out of the tank so it could get a fresh tank of Shell for the tuning.

Then loaded it up on the trailer to make the trip to the car wash and then the gas station. Back home and it’s ready to make the trip to the tuner in the morning. I’m so excited to hear it run on more than 4 cylinders!!!

 

[n8in8or]

Update so far:

The tuner spent a couple hours getting it to run right on Monday. He said he loaded the tune and it still wasn’t running on all cylinders, so he started checking basics....he tried adding grounds to the coils, nope. Then he checked injector pulses - it was pulsing all 8 while cranking then it would cut injectors once started. He eventually figured out it was an airflow over-limit that was causing it to go into limp mode. Once he got past that he found that I had connected the O2 sensors backwards....and to connect them correctly one was going to need the wires extended. I didn’t hear anything yesterday so I messaged him today. He said he hasn’t had a chance to get it on the dyno yet, but it’s ready for the dyno, so that must mean he got the sensor wires extended and if I remember right he said he was going to do a couple additional heat cycles on the engine too, so those must also be done. It’s getting close!!

 

[n8in8or]

Picked up the Envoy from the tuner this evening. She sounds tasty! Can’t wait to drive it around this weekend!!

He couldn’t get the torque converter to stay locked in 3rd past 5200 for some reason, so he couldn’t get good numbers on the dyno (I think he said it put down 332/306 on the dyno....I need to go get the sheet). However he said the 30lb injectors are running at 89% duty cycle and that calculates to 491hp at the flywheel....huh!! I’ll be taking it to the strip once everything is broken in and then we’ll see what the mph says. So stoked!!

 

[ak diesel driver]

nice!

 

[n8in8or]

nice!

Thanks! I can’t wait to slow roll through the camprground with that idle and a trailer on the hitch. That should make some heads turn! My brother thinks the typical campground person is going to tell me it needs a tune up....sadly he’s probably right. I guess that will just weed out who is worth talking to and who isn’t.

 

[MrMarty51]

Nice that it is fired and tuned. I wonder if a manual over ride switch could be installed onto the TC ? just a thought.

 

[n8in8or]

Nice that it is fired and tuned. I wonder if a manual over ride switch could be installed onto the TC ? just a thought.

I’m not sure, with all the modules and stuff tapping into a wire to try to command lockup sounds kind of precarious.

 

[n8in8or]

Yesterday I did 2 things to get it ready to drive:

First thing I did was change the AC accumulator. While doing it I also changed all of the seals in the AC system so I hopefully won’t have future leaks. I forgot to slide some DEI sleeve over the hose before installing the accumulator so I had to use what I had for leftovers for the sleeve that wraps and attaches with velcro.....it’s a little short, but at least the spots closest to the header are protected.



Then I changed the oil. After that I took it for its first drive on the road! The tuner had told me that it had some issues at low throttle input, but he wanted to get it back to me before the weekend so he left it as-is. Yep, sure enough it’s not happy at low input - it has trouble settling on an RPM. He also needs to work on the shift points and converter lockup a little, too, but it was very gratifying to drive it. It sounds tough and that makes me happy. I went to O’Reilley to get some more oil and when I went back out to the lot there was a guy sitting in an Avalanche two spots over from me. When I started the Envoy I saw him start looking around, trying to figure out what that noise was coming from....took him a long while to figure out it was the Envoy rumbling.....LOVE A SLEEPER!!!

Today I lowered the rear end by adjusting the ride height sensors. First thing I had to do was cut the rear bump stops.



I was able to drop the rear about 3/4” and now it’s pretty level.



I also replaced 3 of the 4 exhaust band clamps with lap joint style clamps because the joints were leaking. Unfortunately I still have some leaks so I need to keep working on it. It may end up that I have to weld ball-and-socket connections in the exhaust. It isn’t a huge priority because they’re just small leaks, but it would be nice to have it all sealed up properly.

After that it was time for a real drive! The girlfriend and I went for a 60 mile drive on back roads. It was an enjoyable drive - it’s a comfortable ride and with the stock cat back exhaust it’s not too loud inside.....in fact the intake talks to you more than the exhaust does. On the way home I get on the highway for a few miles....it sure loves the highway.

I can’t wait to get the low throttle input stuff sorted because then it will be really fun to drive. I’m thinking I’ll probably put a stock throttle body on it and take that variable out of the tuning equation.....the hassle probably isn’t worth the maybe 5 horsepower it might be giving me on the top end. Once it’s sorted we can always try putting the ported one back on.

90 more miles and it will be oil change time again.

 

[MrMarty51]

That engine does have a real sweet sound to it. At least I think it does.

 

[n8in8or]

That engine does have a real sweet sound to it. At least I think it does.

Thank you sir, I’m pretty pleased with it so far. It’s fun having a daily driver that isn’t like every other vehicle in the parking lot. I always enjoyed the looks a diesel Tahoe would get and now a cammed Envoy should have about the same affect

 

[n8in8or]

Tonight I dropped the Envoy back off to the tuner. The ported throttle body was no fun to drive - it would hang the rpm at 1500 for an extended period if you blipped the throttle and it was super hard to modulate the throttle at low rpm. So I bought a used stock throttle body from a local yard last week and scheduled an appointment with the tuner for tomorrow. I drove the truck up onto the trailer and swapped the throttle bodies after that, just in case it didn’t want to run at all. When I fired it up at the tuner’s lot it actually was idling and driving pretty ok.....so I took it down the street a little bit......man it’s so much more fun already!! It’s more responsive and the transmission shift points are much more inline with the throttle input. It’s going to be a blast to drive now, I can’t wait to get it back! Looks like I found the cure for my latest cade of forumitis.

Here’a a video comparing the stock and ported throttle bodies side by side. It makes sense why the computer would be so confused at lower throttle angles.

 

[Will L.]

Sux to learn the hard way- but learning is good long term.

Is the old throttle body big enough to make an emergency air shut down for any of your diesels?

 

[n8in8or]

Sux to learn the hard way- but learning is good long term.

Is the old throttle body big enough to make an emergency air shut down for any of your diesels?

Yep, failure is a much better way to learn than success......unfortunately.

Hmmmm, interesting idea there about using it as an air cutoff. It's a 90mm (3.54") blade in the throttle body, so it might-could work in the right application.....

 

[n8in8or]

I picked the Envoy up from the tuner yesterday. It’s so much nicer to drive now! You can actually modulate the throttle at low inputs and the trans shifts when I want it to even with the loose converter. He said the airflow was ok still, he just had to change the parameters for the throttle opening per angle of input and he had all the stock values saved so it was an easy change - he only charged me $20.

Next big change I want to do is gears....I can do 90mph in second! Not super useful on the street. This has 3.42 gears. A Trailblazer SS has 4.11 gears stock. I already wanted to swap a 14 bolt out of a TBSS so it looks like I’ll be leaving the stock gears in the axle when I do that. Or at the very least I’ll put the axle in to try it out, and if I don’t like it then I’ll
Split the difference with 3.73s. Then of course I have to swap the front diff.....which will suck.

I did a small repair last night. A common problem with the Envoy is that the panel on the side of the driver seat breaks at the mounting tabs and then it’s hanging loose. I bought a new GM replacement panel. I had a little of that plastic epoxy I used to fix the bumper cover left so I decided to use that to reinforce the tabs before I installed it.

First I scuffed and cleaned the panel.



Then I applied the epoxy. I would have liked to use a little more to create even larger gussets, but this is all I had left.



Then I installed it.



I forgot to take the “before” pic so you could see the old one hanging loose. But here’s a pic of where the tabs broke off.



Another thing off the list

 

[Will L.]

Glad it’s more drivable.

The throttlebody air shut off was something Ferm said before. I been lookin at ebay and wondering what might be some large stock ones that may be there for the 6.5...

 

[THEFERMANATOR]

Glad it’s more drivable.

The throttlebody air shut off was something Ferm said before. I been lookin at ebay and wondering what might be some large stock ones that may be there for the 6.5...

The Dmax guys are using the 4 bolt, 90mm GM throttle body for sub 1K hp builds.