i keep on reading about those mods and am not to sure what they are....can you tell me what they are and how to do them....

thanks

 

https://www.thirdgen.org/newdesign/t...matetbi2.shtml

 

Any thoughts on it the ultimate TBI mods and are worth it, I mean actual physical measurements? I'll probably try it anyways since I have a free TBI, but I just don't see the claimed results since the small bore of the TBI doesn't seemed to be limited by the inj. pod height and TBI casting itself (never done any actual measurements).

I pull 4.84 volts at WOT on my MAP sensor now = ~101 Kpa.

 

They are an excuse to waste time grinding.

Lik

 

Id like to see you try them since you always manage to get track times. Grinding down the throttle shafts is a guaranteed flow improvement that has been done on all manner of race carbs for years. I would not be surprised if you saw 20-30 more CFM out of the thing just with that modification.
As for the injector pod, part of the mods involve fabricating a spacer for the injector pod and grinding the casting on the rear of the TB so that the pod can be raised high enough to have the spray cone of the injector hit above the edges of the throttle blades which is important for part throttle fuel atomization, I think increased airflow is a side benefit since the injectors are further away from the bore and present more area for the barrels to draw air from.

As for the ridges around the bores, if you pick up a book on induction for example david vizards book on carburetors and intake manifolds you will find a section on the optimal shape for the end of a pipe feeding single barrel carbs since apparently there is great variety in that market or you can make your own.
Youll see that a straight pipe drawing air will actually flow less than its size would suggest because air gets drawn from behind the opening and around the mouth which creates like a low pressure region around the opening like when you pour water from a bottle it curves out it doesnt immediately bend over the opening and run down the bottle. It obviously straightens back out once beyond the opening of the pipe but the opening is only flowing air mostly in the center
He goes on to present other designs that have like a rolled lip and increase in diameter like a trumpet opening to keep the air flowing smoothly along the wall of the pipe and shows the efficiency of each design, he basically concludes that the optimally air should be drawn from a flat surface curving inward with a gentle radius.

You can apply this same theory to the throttle body. When I first did the mod I just thought it would present more area for the throttle bore to draw air from which still makes sense to me, you have alot more space from a side angle with them removed. Now while i still believe that part is a factor I think the theories above are probably a larger factor especially with the non drop base filter. The non drop base has a nice radius to it and it just continued smoothly I think youd see the most flow out of the TB unfortunately those ridges take whatever air just slithering along the surface to jump up and curve back around and over creating the open pipe effect sucking air (or any fluid).

I have not personally tested this crazy talk of mine on a flow bench and nor do i have really conclusive track testing (aside from just totally unscientific Gtech runs) id like to see someone do it in steps with trap speeds after each one. Granted that wouldnt be 100% scientific either since the fuel mixture is a variable. In the end I think the flow bench would be the true test. Still, being that you're car is running rich as it is, any airflow gain should increase your power output.

Im not so sure the Map sensor is totally reliable either for determining if the TB is too small and while I dont think I know how to explain it, I feel that even on alot of engines that are starved for air you dont easily see them pulling alot of vacuum at WOT maybe im wrong. I know for a fact though, that my car which had a single plane and was only running high 14s was pulling near 2 inches of vacuum at 5500 rpm with the stock throttle body. That was on a sears vacuum gauge tapped into one of the manifold vacuum ports on the front of the TB.

That tiny throttle body simply cant do the job. I dont think it flows much more than 350 cfm if that. The unmodified 52 mm TB flows like 474 CFM.

as a by the way, there is another mod you can do that I did not write about (because i didnt know at the time)
In addition to thinning the throttle shafts and smoothing out anything hanging in the breeze, carb guys also knife edge the throttle blades which should look like a crescent around the edge since you dont want or need to do it to the sides of the blades.

Check out David Vizards "Carburetors and Intake Manifolds" for more info on this stuff.

 

Not true speedy

 

Pablo you dont need to defend yourself here. You've done more R&D on TBI's before these guys even knew what the hell a TBI was. You and I were modding TBI's when everyone else switched to TPI.

BTW, Pablo-- I have a GrandPrix GTP now. Since I retired my bird.
In stock form 14.4@95mph. Now with just a couple of mods I run 13.75@101.64mph. By the end of this summer I'll be in 13.0's, not bad for a 4 door grocery getter.

If you ever decide to switch to a V6, call me/email me and I'll give you the hook up.

Go AMERICAN POWER!!

 

TBI master! Hey long time no see man!

I saw your name in the thread and I had just made the comment to one of my car buddies here at work that you were the only other guy around messing with tbi back years ago before a TBI board could have even existed.

Those GTPs are badass cars, dont think ill be going V6 anytime soon though Good luck on the 13.0

as for the tbi mods, i wasnt trying to defend myself, I frankly would like to see some conclusive testing done myself. I just posted the reasoning behind why I did what I did.

 

You and I have spent hours and hours talking to these people about the same crap. "What does it take to make the TBI faster?"
And everytime, someone starts waving the BS flag. I was so tired of re-explaining myself that I had enough. So I stopped posting. When I do give out "incorrect" information I make sure to correct it.

On the hand, I do miss some things about my bird.
The first thing is rear wheel drive. I love power slidding!!
The second thing is the body. Its a head turner when the car is painted nice and taken care of.

Things I dont miss: working on it every GODDAMN DAY!! LOL!!

Talk to ya later TOPFUEL.