Marc,
Good questions, let me see if I can answer them and put some of the other questions and statements to rest.
First, anyone that says they have the best TB for all situations is either driven by greed or is smoking something. The simple truth is that there is no one solution that will handle all possible variables that you can throw at these vehicles. They are no different than cams and can be mis-matched just as easy. You wouldn't select a cam that has duration figures that generate a powerband from say 4,000 - 8,000 unless you had something really special (weird) in mind. The TB's are the same. Dodge actually did a fine job with these given the goals that they had in mind. The engines are powerful and develop their power down low, offer decent fuel mileage and are emissions friendly. The variable venturi (the restriction above the plates) was placed there for a purpose and actually makes the machine operations from the factory more complex. The restriction is placed there to make the vehicles more docile off idle by shrouding the half of the throttle plates that swing upward. This i!
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s all part of the power and emissions equation. Almost every change made can have both positive and negative results. What seems generally positive to some can be viewed by others as obnoxious or down right unacceptable. Removing the shroud above the plates with no other changes will make the engines more jumpy just off idle. Some like this and others don't. The other area that everyone seems to be making a big deal about is machine work. Honest truth, todays CNC machines are capable of repeatability down to .0002 inch (a heck of a lot better than the days where we cranked knobs). Putting down one's machine work without knowing how they are performing their work is just plane stupid. We send out our throttle shafts to have them centerless ground and they come back from the grinder with tolerances of plus or minus .0002 inch (way better then you actually need). Some have commented on attach methodology, whether the plates are attached with countersunk cap screws, buttonheads, w!
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elded in place, staked in place, the list goes on and on. It really doesn't matter as long as the plates don't come loose. The bottom line is all of this is really moot. What is important is the flow numbers and how our trucks react to the changes. We have tried almost all possible combinations and feel we have arrived at a change that best addresses our goals and just as I says this, I am sure that others have made changes different from ours that make power in different areas. There is nothing magical here, just testing and verification. The work that we perform on these for our Stage I's is more complex then just punching out the bores to a larger diameter, but we know it works and increases power throughout the entire powerband. The work on the TB is as follows, first we locate the TB bore centerlines. We do this with a contact probe in the CNC, four points are touched in each bore and the centerline is calculated. This could be actually performed with a dial indicator. On!
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ce centerlines are known, then the TB is bored (variable venturi is removed) and final diameter is set at .015 inch smaller than the throttle body bores themselves. The boring head is then moved .007 inch towards the back of the throttle body and bored again. In essence, what this does is leaves a partial shroud for the plate halves that swing upward. Once complete, we then remove the air horns that rise above the top of the TB. We do this on the CNC and leave four tabs for the gasket. The next step is to machine the air compression angle. This is performed with a carbide end mill. The angle is 7 degrees and actually starts .050 inch above the plates and continues all of the way to the top of the TB. Two words of caution, you don't want to start this angle any lower than .050 above the plates and you don't want to intersect the holes at the top of the TB where the hold down bolts go through because you will allow unfiltered air to enter the TB. In regards to the throttle shaft!
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s, we make new ones. We chose this route for two reasons, we didn't want to work with the factory one because of the half shaft approach that we use, re-working the factory would be a compromise and take too much time, the second reason is that stainless steel wont rust. We re-use the factory plates but we do tumble debur them and ship them out to be anodized. Some people have commented on the lousy machine work out of Dodge in these, let me put this to rest. The factory plates are stamped and tolerance on these are accurate to within .001 inch. Bore centerlines have been accurate to within .004 inch and bore diameters have been accurate to .002 inch. The bottom line on the above work is an increase in flow of approx. 100 cfm and no loss in velocity through the TB. I hope the above info helps, any other questions, send a post.........
Frank
---------------------- Forwarded by Frank T Holloway/CA/KAIPERM on 12/13/99 08:03 AM ---------------------------
Mtbfed@aol.com on 12/11/99 09:38:00 PM
To: dakota-truck@buffnet.net@Internet
cc: (bcc: Frank T Holloway/CA/KAIPERM)
Subject: DML: Re: Re:Best throttle bodies?
Well Frank, first off thank you for this info. Now, seeing that the stock
manifold flows around 650 CFM, and a worked over
stock plate TB will flow about the same, how much work are we looking at? Is
this as easy as maintaining the lower bore
diameter up to the top, or is that 670 CFM reached by a thinner shaft,
countersunk bolts, and tapered bores...etc.
The reason I ask is that I have access to a shop that bores motorcycle carbs.
What do you guys do to the $90 TB's
BTW, where are you located?
Marc Federici
99 SLT+ CC 5.2 5sp 4x2 3.55sg
<
<After a tremendous amount of work both on regular chassis dynos and DynoJets
I figured that I would give my two cents <worth. In stock form, the V-8 TB's
flow approx. 570 CFM @ 24 inches. With stock plates and work, the TB can be
pushed up <to approx. 670 CFM @ 24 inches. Larger plates can be installed,
but the size for a streetable TB is limited by the web <thickness between the
two bores (actually a support for the throttle shaft) and the throttle shaft
bearings themselves. We have <used larger plates (out to 2.025 inches)
without compromising the center web and without actually hitting the
bearings. Flow <@ 24 inches nets you approx. 710 CFM with the larger plates.
All work has been done with either the stock shaft or one of <our SS half
shafts. Whether you use larger plates or the stock plates depends on your
needs and your goals. The stock <intake actually becomes the limiting factor
at around 650 CFM. If you are contemplating a different intake (MPI) and
using a <healthier cam, !
<then you will reach a point where you need to go to more CFM through the TB
whether you choose to use a 4 BBL or <increase the plate size in the stock TB
is up to you. One thing you need to remember is that our engines use a MAP
sensor, <the setup is actually a speed density setup whereby the amount of
air reaching the engine is calculated based on MAP signal <at the base of the
plates. The problem with larger plates is that the velocity through the TB
actually decreases, the computer <recognizes this and supplies less fuel. The
results are a reduction in peak HP through the mid/upper RPM ranges. You can
<see this with scan tools and also see it on the dyno. This doesn't
necessarily mean that big plates are bad, you just need to <take the
appropriate steps within the computer to adjust accordingly. If you don't
plan on going the custom route with <software, then smaller plates are better
(you need to keep the velocity up through the TB). If done correctly, the
factory plate <size will net you more HP and Torque throughout the powerband
with all after-market bolt-on equipment then larger plates will. <This
includes cam changes. We have been down both roads and it really doesn't
matter to me if I use larger or factory size <plates. The goal is to match
the work to the intended modifications.............
<
< Frank
<
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