TBI Throttle Body Tear Down and Rebuild.

[Swims350]

Any improvements?

 

[Jims86]

The only way to really tell is at the Pump IMO...and the guys that I did them for dont really worry about the price of gas...their foots are in it all the time.
I think whateverbhelp you can give the throttle body is good, due to injector placement. I have seen some study somewhere, saying the fuel spraying into the throttle body is worth close to 20cfm.
Excellent mid range and top end with the CFM-Tech spacer and injector pod spacer.

 

[89Suburban]

I wasn't talking about those. i meant the ultimate tbi mods, grinding down the top and such.

Ahhhh....gotchya. Should go quick with a die grinder. I have done 3 so far.

Can you please elaborate?

 

[Swims350]

yea on the TB itself in front of the injector/butterfly holes they have a casting lip or ridge, you grind that off and raidus the top area down into the butterfly holes to allow smooth airflow. here ya go....

http://www.gmt400.com/forum/showthr...-TBI-mods-stage-1&highlight=ultimate+tbi+mods

 

[Jims86]

before

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After

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[89Suburban]

Oh, the lips around the bores?

How about cutting a ping pong ball in 2 halves and using them as stream line covers on the top of the injectors?

 

[Jims86]

Oh, the lips around the bores?

How about cutting a ping pong ball in 2 halves and using them as stream line covers on the top of the injectors?

Nope, uh uh....its the area around the lower area of the injector pods that matters.

 

[Swims350]

mines shaved down now and smoothed, going to work it down smoother by hand with some sand paper, that's about it.

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[89Suburban]

Next question, are those ridges there for a reason? Like, as a barrier or a lip for oil from the breather or something? Why would it come factory with those lips?

 

[Jims86]

Next question, are those ridges there for a reason? Like, as a barrier or a lip for oil from the breather or something? Why would it come factory with those lips?

That my friend, would be the 8th wonder of the world. I dont see any reason for them, except to maybe straighten out the air. But when you shave it, its giving more area for air to enter, due to the position of the injectors. Thats where the injector pod spacer comes in as well, but you can only raise them so far up. The pod spacer rasies the injectors 1/4".

 

[89Suburban]

That my friend, would be the 8th wonder of the world. I dont see any reason for them, except to maybe straighten out the air. But when you shave it, its giving more area for air to enter, due to the position of the injectors. Thats where the injector pod spacer comes in as well, but you can only raise them so far up. The pod spacer rasies the injectors 1/4".

Oh, I thought the 8th wonder was my ex wife, lol...

 

[Guardian]

It does serve as a benefit but creates limitations in doing so. The benefit is to increase the air velocity at low speed but starves the engine at the top end. This goes back to the engineering process, they design it to operate in a defined range but we want it to perform in a completely different range.

 

[Swims350]

that works fine for me it doesn't see much rpm's maybe 3k or so on the highway or me just revving it up for the heck of it.

As for the ridges my thoughts....

fuel spray, to contain it in case of maybe it trying to come out? i highly doubt but may on some really fast air pushing in, shoving the stream/spray back?


Now here's a side note, notice how thick the pod gasket is? it's almost 1/4 inch itself. So what good or how much is the 1/4 pod spacer going to do if you DO NOT use a gasket with it?

OR

why not stack 2 gaskets and make your own?


Also on the fuel starving at upper rpms, maybe that's why I've seen some guys make the FPR adjustable to make for more fuel?

 

[Jims86]

Yeah, but I think the guys that are adding fuel(or so they think) with an AFPR for fuel starvation have more modified engines.
When you jack up fuel pressure, the computer is going to try to make adjustments to meet what is programmed in the Fueling tables.
Its always better to tune the chip for mods, instead of adding what I call "Bolt on bandaids".
AFPR's only come atfter the Tuning requires it, contrary to popular belief.
You can add one to a stock engine, but I would recommend checking the pressure that the stock regulator is providing before installing one.
Its funny to watch a Datalog where an ECM is fighting with modification without tuning.

 

[Swims350]

sounds good to me then because I was unsettled on even trying to mess with the FPR besides changing the thing out.