Tunin for Throttlebody change

[Naf]

Ok, i changed my original 75mm throttle body for a true 80mm one.

Now i am noticing two things, a lean mixture in cylinders 7 & 8 and a sluggish rev up between 1500-3000rpm. Should i adjust my ETC? If yes HOW??

would it be simply taking (80/75)-1=0.067 and multiplyin it against my resent ETC airflow?

[DrX]

What year, make, model, engine?

Any change to B4349 should be based on the ratio of the throttle opening areas rather than the diameters. Area= 3.14 x (radius^2)

[Naf]

i have a 2006 Tahoe, With a 5.3L fly-by-wire throttle body

So the increase would be ((3.14*(80/2)^2)/(3.14*(75/2)^2))-1
so in my case it would be 13.7%

That is a lot, no?

[DrX]

Stock 78mm TB area = 4776 mm^2
New 80mm TB area = 5024 mm^2

B4349 units are % per square mm

B4349 for stock 78mm TB = 100/4776 = .0209 which is pretty close to the value of .20767 in your factory tune.

B4349 for new 80mm TB = 100/5024 = .0199

Which isn't much of a difference and would only affect idle, if anything. Did you change anything else in the tune?

[Naf]

Well these are the following hardware changes i did to the vehicle

AEM brute force intake
Bassini equal length headers
1.7 summit roller rocker arms
Moroso 9.75" long ultra 40 wires
Bosch platinum +4 sparkplugs
3" catback

On the software side

increased VE by 1% due to leanin
increased MAF by 1% for MIL light
changed transmission Shiftin pattern / timin

Thats about it...I might venture and increase the VE and MAF by an additional 0.5% but i need to see the Ben factor from the log...

Thank you for your help

Naf

[DrX]

What kind of throttle body did you install? Is it electronic(ETC) and similar in design/operation to the stock TB, solid throttle plate with no holes in it?

[Naf]

I installed a BBK and ported the rear end to 80mm instead of the 75mm use to have it for my other vehicle, thats way it was ported...My original TB was 75mm at the plate and 72mm at the rear...

Oh i forgot to mention i installed LS6 springs as well...I use to have 1.8 rockers but it was spoiling sparkplugs on 7 & 8 and she felt really sluggish so i dropped in the original ratios..

I attached two files here, one is my current tune 0000, the other is what i will change to when i get the car back from the dealership...Body mounts are no good, warrantee.

[DrX]

So the BBK uses the motor from your stock TB and there is no separate idle air control motor or holes drilled in the plate?

[Naf]

Exactly like stock, it even uses the stock motor and middle gear as well...