DIY: Porting & Polishing a Throttle Body (Video Tutorial) - Mercedes-Benz Forum

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post #1 of 4 (permalink) Old 10-23-2013, 12:25 PM Thread Starter
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DIY: Porting & Polishing a Throttle Body (Video Tutorial)

Video tutorial on how to port and polish a vehicle's throttle body. In order to do this procedure, you must remove the throttle body from the engine so you can probably polish and port the throttle body and the material shavings do not enter the engine. This isn't much of a horsepower increase if any, but it does help with throttle response and reduced the build up of residue on the surface of the bore. Do not remove any material from around where the throttle plate touches in the bore either. Also when doing this procedure, I would recommend purchasing a new throttle body gasket so you won't have any vacuum leaks once reinstalling. Make sure you don't take off too much material either where it will affect the structural integrity of the throttle body. When doing this type of work, make sure you wear safety glasses for your own person protection.

-remove the throttle body from the vehicle
-clean any oily build-up inside of the throttle body
-remove the butterfly from the throttle body, most are held in with 2 screws that go into the shaft
-if you can, also remove the shaft and linkage (some shafts are pressed into bearings, other are not)
-if you can't remove the shaft, no big deal you just have to work around it
-tape around the shaft or the hole where the shaft was so no metal shavings get into that area and cause premature wear for the bushings or bearings
-depending on the finish of the throttle body's bore, there may be edges which you can to smooth out
-in order to smooth out those edges, you can use grinding stones for either a drill or rotary tool such as a Dremel
-when using a grinding stone, it's best to use WD-40 penetrating oil with it so the aluminum material doesn't plug up the stone and it'll no longer cut away any material
-once you are satisfied with the sharper edges being ground down, you can down move onto sanding drums for the rotary tool
-you can also flare out the bore where the air enters slightly so it has a smoother air flow into the throttle body
-you can even port match the throttle body to the intake if the throttle body is smaller
-if you don't have access to a rotary tool and sanding drums, you can also use flap wheel drum sanders that can be used on a drill
-the flap wheel drum sanders are available in a variety of grits such as 40, 50, 60, 80, 120, 180, 240, and 320
-when using the flap wheel drum sander, you can add water to help with finer sanding as to keep the dust down
-if the surface isn't too porous such as what is shown in the video, start out with a finer grit like 120 and move your way up
-once you have reached the highest grit in a flap wheel drum sander, you can now do some sanding by hand with 400 grit and add some water for lubrication
-once satisfied with your product, you can now move up to an abrasive like Scotch Brite
-depending on the color, will depending on how course the abrasive pad material is
-I started out with green and then moved onto the red pad for the finest compound
-you can also use water with this too to help finer sanding and to keep the dust down
-again once you are satisfied, you can now move onto a metal polishing compound
-the metal polishing compound I would recommend is Eagle One
-apply the polishing compound paste and rub until highly mirrored finish (multiple coats can be applied to achieve a higher polished surface
-once you are done with the bore, you can now move onto the throttle plate
-most throttle plates are smooth to begin with so you can skip directly to the Scotch Brite stage using the same procedure and finally move onto the metal polishing compound
-once done, you are ready to reassemble the throttle body
-make sure you peen the thread of the screws on the other side to ensure they don't come out or apply Lock Tight thread sealant
-install new throttle body gasket along with throttle body to your vehicle
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post #2 of 4 (permalink) Old 10-28-2013, 09:35 PM
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There's no question that you are 100% correct and pretty much everything you've said is bang on. Much like myself, you prefer to explain the why's and how it all works too, educating your viewers is excellent, it's just so wordy that you make the task seem far more involved than it is.
This is actually a very easy process though, which I've done for years on countless high performance vehicles (been port matching and polishing intakes for 30+ years).
Will it make a difference on most BMW's on the streets today? Maybe, if you record before and after performance with a quality scope as you 1/4 mile it, but it is peace of mind all the same to know that it isn't being restricted by burrs and rough surfaces. Kinda like how cars always run best right after being washed.
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post #3 of 4 (permalink) Old 10-29-2013, 12:14 AM
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Great video. Very informative
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post #4 of 4 (permalink) Old 10-29-2013, 07:53 AM
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Originally Posted by ozmedia View Post
Kinda like how cars always run best right after being washed.
Mine run way better after carpet vacuuming,
I did polish intake in miniature engines even before ozmedia started his polishing, but that was on 2.5-5 cc engines turning 16,000 rpm. Each percent of extra power was a big deal in small airplanes.
Car engines on other hand run mostly using +- 10% of engine power, so beside extreme situation the intakes are well oversize.
I was having head off on 603 engine and was cleaning huge gunk intakes on those accumulate. Took a look at very rough surfaces and was tempted a bit to sand and polish them, but the shape would never allow me to get in all corners, while I figured out the 27 years old engine run fine for 293,000 miles so kind of late to try improvements on it now.
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