k i bought the high flo throttle body from RPW last week and when i went to get it installed some serious issues came up...

1. has the butterfly also been machined?
2. it seems all that this has achieved is stuffing up the air flow as when the air reaches the butterfly there is a step for the air to pass over which wasnt originally there, hence restriction

whats the deal? :x

it's probably there to reduce idle lumpiness. that's only a guess.

To my knowledge....
1. BF has not been touched on these "swap over" TBs.
2. That mouth area of the TB has been machined off on purpose to improve low RPM flow and response. Why the "lip" was there? Perhaps to mellow down the action to make the engine feel smooth for ppl buying Magna as "family car" not hoon-mobile like we do.

Corrections accepted - with a bullet from me 8)


k i bought the high flo throttle body from RPW last week and when i went to get it installed some serious issues came up...

1. has the butterfly also been machined?
2. it seems all that this has achieved is stuffing up the air flow as when the air reaches the butterfly there is a step for the air to pass over which wasnt originally there, hence restriction

whats the deal? :x

Sounds probable, but wouldnt a lip cause turbulance and cause restrictions?

ill wait for Dave to clear this up, or if anyone else knows

the lip you are talking about is what gets machined off.

the B/F hasn't been touched.

you sure you are not holding the stock one in your hand?? cos yeah - they machine that little lip off so that T/P doesn't need to be as high to achieve the same airflow hence increasing throttle repsonse.

Manual

That's why it has been machine off. To improve the flow.


but wouldnt a lip cause turbulance and cause restrictions?

What im saying is that it has not been machined all the way to the butterfly, so before the air reaches the butterfly the bottom of the passage raises a few mm, which you'd think cause turbulance with the air flow

unless its machined all the way through, is there a point?

Ha!
Got it now. It's called venturi. Well - at least "us people" call it as such.
decreasing the barrel size in that manner creates a sudden increase in the air speed and so on. How ever, that is more releveant when playing with carburettors, where that increased air speed then creates vacuum/suction and "sucks" the gasoline part of the mixture via the jets.
The narrower the venturi, the more air speed, the more suction, the more fuel. Works better on lower RPM etc. The bigger the venturi, the less air speed in relation and the less vacumm through the jets - works well only on hi RPM. Hence this was the way we used to trim engines to work on different RPM related to cam degrees, head ports etc etc.
Why is the step there with these TBs? Most likely cos it was quite expensive to machine it all the way through and then re-manufacture the BF etc. But obviously fully bored TB was breathing more than this cheaper construction.
And why does the original TB have the lip there in the first place to stuff it up? Ask Mitsu.... Perhaps for the reason I assumed before in this thread.
Hope this helps.



What im saying is that it has not been machined all the way to the butterfly, so before the air reaches the butterfly the bottom of the passage raises a few mm, which you'd think cause turbulance with the air flow

unless its machined all the way through, is there a point?

I thought dave left that ridge and lip there so they didnt have to touch the butterfly because they were having problems with them sticking once they were machined..
also something to do with the cruise control on models with it..
GuRu

There is a massive lip on both sides of the stock throttle body on the upper side on the front I think and on the lower side on the rear.

We remove these lips on both sides to improve low rpm throttle acceleration as well as overall air flow.

We used to machine out the butterfly but the problem is that this throttle body is not a parallel bore. It starts off parallel at the front then goes up parrallel at a 45 degree angle then goes straight and then back down again at a 45 degree angle back tot he manifold.

Hence why we had so many problems machining them out.

There is no air disruption problems with the minor lip that is left behind as the lip you are referrign to is actually there factory if I recall as we machine it elsewhere.

We use to machine out a larger butterfly but the problem was that the throttle bodies are also not centered on teh butterfly shaft in relation to the butterfly Ie the top half the butterfly represented more than 50% of the surface area and when we machiend this out there was too much vacuem on the butterfly holding it open amongst other problems.

We could fix it in some cases with stronger springs but this wouldn't work with cruise control and in the end we decided it was not a viable option as we could not garauntee it would always work.

So the high flowed units which I have found personally on my own car and other customers works extremely well and definitly improves throttle response and acceleration.

David Thomas

can someone actually post some photos of the before and after throttle body ? you cant tell what your talking about when you say " the small a lip near the c port and yeah it was good because of the z"

I don't have any photos at this time but If I get a chance I will

sounds giood, but another prob is that where its been machined the surface is very rough and theres still carbon build up, maybe a few minutes of sanding and polishing would be a good idea to deliver a better product ;)

certainly something to look at yes.