TOPIC: 2007 Chevrolet Avalanche ZLT 5.3L Vortec flexfuel

This is just an update on this vehicle, having two throttlebodies allows me to experiment a little.

TB-A has the groove placed at 19.7 throttle plate position,
idle position - 17.3 @599rpm
engine temp 190F.
Load % 18.0
MAP 9.7
SHRTFT1 -.8/-3.1
LONGFT1 -10.2
MPG Highway was 17.3mpg on this configuration with no arguements from the ECU.

TB-B has the groove placed at 18 throttle plate position,
idle position - 18.4 @597rpm
engine temp 190F.
Load % 18.0
MAP 9.7
SHRTFT1 -.8/-3.1
LONGFT1 -10.2


After a run on the highway with local streets to and from
idle position - 16.9/17.3 @ 597rpm
engine temp 194F
LOAD % from 18.0 to 17.6
MAP from 9.7 to 9.5
LONGFT1 from -10.2 to -11.7

Pedal reaction also changed, that almost 2 degree change went from a delayed pedal reaction to a quick/clean response to the pedal along with a healthier engine response as well.

Took the truck for a run today, 10/4/2012, got to my turn around point and reset the AVG MPG reading, on an 18 mile return run it reported an average mpg of 19.3mpg.

This is an 18 mile stretch of State Rt 16 west of the Tacoma Narrows Bridge that has some uphill climbs along with the downhill runs. Average speed was between 60 & 65. 60 when the police cruiser went by.

I'll get more numbers after the fill-up and get some more miles in.

Karl Fortner
Tacoma, Washington

Well, since I've been using this vehicle for trips to Seattle the past two weeks the engine and ecu have had time to settle in to a routine.

256 miles per week.

The original readings...
TB-B has the groove placed at 18 throttle plate position,
idle position - 18.4 @597rpm
engine temp 190F.
Load % 18.0
MAP 9.7
SHRTFT1 -.8/-3.1
LONGFT1 -10.2

and the latest update...

TP - 18
RPM - 597
engine temp 194F.
Load % 18.0
MAP 9.3
SHRTFT1 -.8/-3.2
LONGFT1 -14.8

The trips include long waits in traffic due to the natives inability to drive.

With that I was still getting an average mpg of 16 or better.

I just regapped the spark plugs as well... the two right rear plugs are a bear to get to (passenger side) but not impossible

Original gap .036"
New gap .060"

Current stats with this change at operating temperature

TP - 17.6
RPM - 595
engine temp 194F.
Load % 17.6
MAP 9.7
SHRTFT1 -.8/-3.2
LONGFT1 -14.8

Will be running up to Seattle next week so I'll be getting more feedback in short order.

Karl Fortner
Tacoma, Washington

I'm looking forward to seeing the results of this, Karl!

Have you insulated the O2 sensors yet?

Just did the plugs on Friday, want to see the results from that first.

Have the wrap, will do that this weekend... one monster at a time.

Karl Fortner
Tacoma, Washington

Hi karl
can you tell me witch one is the better one, 18 or 20 degress,
Thanks
Markus

For ???

The throttlebody I had in the engine had the groove cut with a medium sized bit.

After some run time the ecu started coming around and accepting the changes which was giving me an average of 16-17mgp on the round trips to Seattle.

I just swapped out the TB, this one grooved with the large bit, throttle plate position approximately 17.1. I actually used the stain marks on the intake side of the TB to set the plate position.

Once that was done, I closed the TB completely and grooved the other side of the venturi (manifold side of the plate) with the medium bit. I'm looking for flow effect on this side without throttle plate intervention.

Current numbers from the OBDII

TP - 14.1
RPM - 650
engine temp 190F.
Load % 19.6
MAP 9.5
SHRTFT1 -.8/-3.2
LONGFT1 -17.2

Prior numbers
TP - 17.6
RPM - 595
engine temp 194F.
Load % 17.6
MAP 9.7
SHRTFT1 -.8/-3.2
LONGFT1 -14.8

Monitoring the interactive fuel monitor as I was taking a short run for effect

local street at 30mph, mpg went from 20mpg to 47mpg on the same streets (this in 4cyl mode)
at 60mph highway average went from 19mpg to 27mpg... not accounting for foot sensitivity.

Hoping to see an improvement on the combined average on this one.

Day's are getting longer and starting to warm up so the opportunity to tune and test other items will increase.


On a side note; when I took the intake plenum off, the reservoir that catches the moisture had a substantial amount of water in it.

What I want to look for is a bladder valve that I can install under the reservoir to allow it to automatically drain when there is no vacuum on the intake. We'll see.

Karl Fortner
Tacoma, Washington