Does anyone have any information on modifying or modified throttle bodies for our Xa/Xb's? Any input would be appreciated.

Cheers,

David -

 

I too is looking for someone that prob has swapped it out or port and polished it. However, I have bypassed the coolant from going to the trottle bodys therefore keeping it cooler. Have seen a slight improvement and costs under $10!

 

I haven't looked at the xB's TB, but I know many TBs have lots of extra metal that you can remove, including some flush-mounted screws to hold the TB plate on. Probably only worth 1 hp or so, but it usually only costs time.

If you bypass the coolant...how are you keeping it cooler?

 

You are keeping it cooler because hot coolant is no longer flowing through the throttle body. And the tb on 1nz's are pretty thinwalled , not much more can be done , it can only be wallowed out a little bit more.

 

Just a random thought, but I always wondered if a 1ZZ throttle body would fit. . .

 

I doubt you can feel any gains from bypassing the TB coolant. The air moving thru the TB moves too quickly to absorb any heat. There have been tests conducted on this and there is no noticeable temp drop.

 

Why would you modify the TB? It already is capable of moving more air than is required by WOT? There are no gains to be had unless the rest of the engine, intake and exhaust are capable of handling more air. It is not a restriction in the system. You also run the risk of losing power by reducing the velocity of the intake. Don't you think the engineers at Toyota did the reseach on this?

 

my understanding is that the throttle body IS what determines how much air moves at WOT. . . it couldn't be capable of moving more air than it already is, unless you have FI. But by upgrading to a smoother or larger TB, you would increase the possible flow. And if the argument about velocity were true, than there would be no point in upgrading intakes, exhausts, or headers. I'm sure Toyota engineers did their work, but sometimes cars are not designed to squeeze out the maximum amount of performance-- they are built with a minimum cost/maximum benefit outlook, and their benefits are usually things like durability, emissions, etc etc. Why do you think these things cost $14,000? We don't exactly have F1 throttle bodies.

 

The MAF is what measures the amount of air flowing so the injectors know how much fuel to add. The Throttle body controls the amount of air and is sized properly for the engine application by the engineers. Do you even know if the MAF can handle the added flow? The TB diameter and length are part of the equation. A larger TB will not do any good without the OTHER components being designed to take advantage of the increased airflow.
The cost to make the TB a bit bigger is not the factor here.. Its size was chosen to match the engines other variables. Too large a TB and you will affect driveability without increasing output. A smaller TB in this case will create a higher velocity which works with the design of the intake maniifold and matches the need of the engine. Change one of these parameters and you affect something else in chain.
The reason you don't have an F1 designed TB is because its not needed and wouldn't do any good for this application. Ported and polished would not help any until other areas are addressed... A polished TB only benefits a TB when everything else is sized correctly and a slightly smoother airflow is desired. But it really only matters when everything else is addressed first.. Its like icing on the cake.

 

I'm not an engineer, so I'm not sure. . . I just know that improved TB's have increased output on other makes/models. I'm assuming that the MAF measures the air flow, and a throttle body upgrade will increase air flow, which the MAF should pick up. . . but I'm not going to argue with you, as I don't understand this stuff very well. I don't plan on messing with it anyway.

 

The questions that should be asked are how many CFM can the stock TB handle, and is that enough for the modifications being done to the engine over the stock requirements.

 

Or more simply put, "Is the TB a source of restriction at this time?"

 

McBain alot of people aren't looking at any one product to give them lots of power , most people out there are smart enough to know the more mods to the entire engine and it's systems the more power that can come of it.

 

I bore throttle bodies as a side job and I will be taking the one in my XB appart pretty soon and boring it.
Will let you guys know what I find out.
This is my web page by the way
www.maxbore.com