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Discussion Starter #11
This is the feedback from our first guy. We are waiting on a second guy to get his on for his feedback.

I was using voice dictation on my phone on the drive home to jot down my observations on differences I noticed.
I didn't expect to notice much with only the upgrades to the airflow. Well, not only do the changes look great,
they also seem to improve on an already pretty awesome design from Chevy.

1) The truck seems to shift a little harder. This may indicate more responsiveness. If it is responsiveness,
then that might be a positive. It did smooth out later on. This might also be the truck trying to engage 4wd.
I was almost to the Lawrence exit before I notice the switch was in the wrong position. It didn't engage,
though, and I made sure I didn't screw anything up when I got home.

2) You guys managed to break my 50 mile average fuel mileage through Kansas City where my new record is 32.5 MPG.
This is a 2.0 MPG improvement over my past 30.5 MPG. This includes some slow traffic and a minor traffic jam.
Most of the time my speed didn't exceed 60 MPH.

3) The highway RPMs are lower than before the new breathing tubes. I ran a steady 2000 RPM at 70 MPH where I
now run 1800 RPMs at 70 MPH.

4) There is more underhood noise than before. For someone hoping to fool people into thinking this is a gas
engine, this could be a negative. For me, I love people asking if it really has a diesel engine in it! A
little more noise that screams 'Babymax' is a great thing.

5) I drove for a bit with the windows down at <40 MPH and could lightly hear the turbo kick in. Previously,
it was nearly impossible to hear the turbo.

6) I can't be sure of this one, but it seems to accelerate to highway speeds on entrance ramps a little quicker.
That might just be perception.

Also, since you have another Colorado that will be testing some parts, it might be good to find out if he has
a tonneau cover on his or not when looking at MPG comparisons. I've read the tonneau cover will add 2-3 MPG, alone.

So far, it's looking good! I'll try to note any new observations and let you know. If you have any new ideas
after we get moved, let me know and I'll try to get the truck to you.

Thank you very much!


1,173 Posts
Discussion Starter #12

Second day update:

1) It looks like I am still averaging a +2 MPG increase, even while at city speeds. Because it is a lot of stop & go traffic, I'm using the computerized average which is holding fairly steady between 25 & 26 MPG. The stopping drops the average (naturally), while steady 40 mph speeds are showing 35 - 40 MPG. With a light foot, the truck used to show 22-24 MPG averages in the city, which is reflective of the rated 21 MPG City rating.

2) Since I purchased the truck (stock), I've notice the little 4-cylinder has a definite 'sweet spot' for the best fuel mileage. In the top gear (6th) it really liked 60 mph before the upgrades. My best fuel mileage numbers have come from that cruising speed. Since the upgrades, the truck has a new 'sweet spot.' Now the best mileage for the highway is 68 mph, which is better for me since most highway driving is now 65+ mph. I've also noticed, as referred to previously, a new 'sweet spot' appearing at 40 mph. This is in a lower gear, but the truck is finding the right power to maintain these speeds at the best fuel economy. The 68 mph point is running a steady 28-30 MPG, while the 40 mph point is showing 35-40 MPG.

3) I have a little oil seepage coming from the front boot of the boost tube. According to what I've read, the oil is normal as the oil recirculates and is reinserted into the cylinders after the turbo. I'm hoping the seepage can be stopped by tightening the clap connecting the boost tube to the front boot. This is common after installing a Banks boost tube to a larger diesel engine.

4) Since I restarted the truck a few times, another difference I noticed is how the motor first starts. The first cylinder fire after the starter rolls the engine 'lurches' the truck more than any of the gas vehicles I've owned, including a previous Towanda 454 and my SSR's 6.0 LS2. My step-father's diesel does the same thing when first fired up. It makes sense due to the more violent pressurized explosion of a diesel engine vs the sparked explosion of a gas engine. Since the upgrades, the first crank over seems a little more violent. I'm leaning toward the assumption that the engine has more available free air (oxygen) at start-up to compress at ignition. This results in a slightly harder 'first-fire.' All of the other minor changes since the intake upgrades would back up this theory.

The service manager at the dealership took a little time to look at the upgrades and ask some questions. He is curious about the power numbers after the changes, too. He thought all three tubes looked really good and, when compared to the stock tubes, clearly saw the improvements in air flow over OE.

If I can give you any more updates, I'll keep them coming.

Have a great day!


5,569 Posts
Nice work on the tubes!!

Curious, as to any other changes besides those on the truck?

Wondering how new CAC tubes would lower the rpms by [email protected]

1,173 Posts
Discussion Starter #14
No other changes. My guess is if indeed the rpm changed it is because we changed where the convertor locks up. That's the only thing I can come up with.

6 Posts
Me too.

whatcha got cooking?

VERY interested in anything to improves fuel economy or something that improves power without negatively impacting fuel economy.

I bought this truck instead of an Accord ;)

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