: Northstar TB upgrade



Mr. Mohr
04-24-13, 08:55 AM
Does anyone know if there is a larger Throttle Body that can be swapped onto the 4.6 (04 SRX)? I know I can port and polish it, but what about upgrading to say a 80mm or larger TB?

Submariner409
04-24-13, 09:37 AM
Somebody must hype one - - - remember: the engine is PCM controlled - you'll need to have the fuel/air mixture mapping recalibrated.

BlueAngel#07
04-24-13, 09:54 AM
Do you have to remap for a port and polish? Or just the upgrade to the larger body?

Mr. Mohr
04-24-13, 09:49 PM
I don't think so for a P&P. It's not really flowing mire air, just less restrictive I guess.

BlueAngel#07
04-25-13, 07:39 AM
I don't think so for a P&P. It's not really flowing mire air, just less restrictive I guess.

I hope so, I'm thinking p&p and a k&n since that's about all that can be done on the 4.6 without voiding warranty. Thanks for the info.

Submariner409
04-25-13, 05:10 PM
Considering that the OEM throttlebody and air intake system flows more air than the engine can handle at WOT redline, the whole discussion is moot.

Connect a sensitive vacuum gauge to an intake side vacuum port. If you see less than an inch of vacuum at WOT redline, nothing short of forced induction will make it any better ................

30" of vacuum = -14.7 psi at nominal sea level barometric pressure. Atmospheric pressure forces air into an engine depending on throttle opening - the engine does NOT "suck in" air - it creates a vacuum in the cylinders which atmospheric pressure attempts to equalize. (Naturo abhorret a vacuo.)

BlueAngel#07
05-01-13, 01:01 PM
Good to know that it's a waste time, I have officially given up on trying to do anything to my N*, in fact , I am happy with the way it is. Thx for the heads up.

Submariner409
05-01-13, 03:23 PM
Air filters - be VERY careful about spending big bucks for a so-called "performance" oil-wetted filter. The GM MAF does NOT like them. A Fram, AC Delco, WIX, Purolator, PartsMaster pleated panel filter has a LOT of surface area (pull the pleats open) and actually filters down to the micron level. And, for $6.79, you throw it in the trash and drop in a brand new clean one.

GM MAF's - I fooled with a JET Performance MAF in my STS a few years ago - it's a mechanically modified OEM DELPHI MAF - and all it did was to give the engine an off-idle bog, midrange stumble, and cost me ~2 mpg lower gas mileage. Not a seat-of-the-pants assessment, either. Two 1700 mile round trips to/from Florida, using the original MAF one way, the JET the other, same Shell gas, same load. It's still on the garage shelf. Pictures in my albums. (For the cars with a divorced MAF - picture - the tiny black bead at the edge of the bore is the IAT thermistor. The honeycomb "screen" is actually an airflow straightener - just like in a wind tunnel. You can barely see the 3 heated resistors between the bridges which are part of the airflow calculation circuits - don't mess them up and don't get oil on them !)

CadillacLuke24
05-02-13, 12:08 AM
Good to know that it's a waste time, I have officially given up on trying to do anything to my N*, in fact , I am happy with the way it is. Thx for the heads up.

They ain't settin' the world on fire, but they are potent sleepers :D