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Old 05-21-2013, 08:46 AM   #1
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What I Drive: 2002 Rally-Spec SVT w/ 2.5L swap

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MainiaX Rally $1 Throttle Body Mod

I know this is a bastardization of like 3 other mods - but you all know i am dropping a 2012 Ford Fusion 2.5L I4 Duratec Lower End under a 2.3L Head in my Rally Car - and when i wait for parts (new crank bolt / timing peg kit) i get fidgety - do decided i did not want to spend the $249 for a Billet TB - and went to work on mine.

Took about 1.5 Hours - more like fine surgery than hacking - MANY things you can mess up that will put you in the market for a new TB. Procede with patience

I am not a fluid dynamics engineer, however, on inspection you can see this is a mass produced part with several blatant aerodynamic faults. Lets Correct them !

2 Part Epoxy
Round File
Dremel Type thingy from Harbor Freight
220 Grit
440 Grit
900 Grit Paper

Took TB off the Car - did a lil work to the Cosworth Style Intake to mate up perfect with the air flow from the TB


1. Ground down the screws where they protrude on the TB Butterfly Flap - BOTH sides - but on the head side left a little meat so they dont dislodge

Dremel First
Then Paper from course up to smoothest

2. Ground down the BUMP(s) on the INTAKE side (meaning side to your CAI) - but dont take too much or you will go through the body of the plastic - then have to weld it up with plastic epoxy.


3. Clean the whole thing out - and rough up (220grt ) the duck tail side of the TB butterly flap with the recesses in is. Clean again

4. Carefully - oh so carefully mix up a batch of 2 part epoxy and fill the two voids with just enough epoxy to not tumble out, and do NOT get any on the sides of the TB tube, or the lip - you will need a good Vice Grip or something to insure this Flap DOES NOT MOVE while the epoxy sets - and is 100% level on your table. Failure to do this may result in a glob of epoxy in the wrong place - hindering operation, or if unoticed and breaking off during operation - fill your cylinder with a non combustible substance ;)

4. Filled the duck tail in layers if you must. I did two. Layer one 60% filled the void. Be patient. Let it set. Layer #2 filled it completely and then a bit. Let is set overnight. You cannot sand/grind wet epoxy (ask me how i know ;)

5. Use this type of attachment and begin to FEATHER SAND the rough epoxy off. Your goal is to create a smooth, uniform surface that is FLAT. We are looking for unrestricted airflow here - dips, divits, peaks, bumps are our enemy.

6. Now sand from 220 up to 900 to get the flap perfectly level and smooth - do this by hand, pour a cup of coffee - you are gonna be a while. Do NOT take any off the out riing lip of the flap - or it will create air leaks around it hindering idle (i suspect)

7. Inspect, tune, tweak, etc. - NOTE _ take the gasket out, fully clean the channel and gasket before you re-install - i probalby should have taken it our fist - but ...well, not too smart, i admit :)

NOTE: This is going into a Rally Car, a race car - rough idle is OK, and daily driving is not in the life of this Foci

It drives Rally Stages which are 2 to 15 minutes long. Then transits to the next stage to do it all over again a few days in a row. I am not sure what the daily driving effects of this mod are - but for smoother flowing air - i gotta believe throttle response and WOT will be improved over stock. Also, throttle response is super important because we use the right peddle (gas) to drive the FRONT of the car, and left foot braking to drive the rear of the car. Its all about rotating the car.

Enjoy - sure a number of you could figure this out - just thought i would share !

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Old 05-22-2013, 10:00 PM   #2
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Old 05-23-2013, 05:33 AM   #3
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Wow - i like that detail way better than my write up - great stuff - thanks for posting that link - seems like there for sure is performance to be squeezed out of these TB/s

Bravo !!
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