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Two-Wheelin just told me that I might be the first person to post that they've done this mod, so I'm starting a thread here to document the mod. Most of this is a C&P from a thread I started on Tech.

Our stock horn is 63mm. Mine is at 68mm. I also removed about 2mm from the IM part of the TB, but I dont recall the total measure now. I dremeled probably 3mm off the top and bottom of the shaft and put an edge on the leading edge of the plate sharp enough to cut paper.

Here are a few after pics. Sorry for the crappyness. Notice how low profile the shaft is now. Viewed from the front the shaft is almost perfectly flat now.


EDIT: See post #104 for my final assessment of the effectiveness of this mod.
 

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Discussion Starter #2
I PMed with TW regarding the 3" flap wheel that he reccomended for this mod. I initially found that it simply would NOT fit into my TB horn. He said it should be a very tight fit, but could be compressed manually into the horn. This girl couldnt do it. I had a Black and Decker flap wheel, so maybe that brand is a lot stiffer and cant be compressed .5 inches.

I used my dremel and coarse grit sanding disks. It took me a whopping 2.5 hours and three 60 grit sanding disks to remove the 4mm of metal. I held the TB in my lap, making gentle sweeping motions with the disk over about 1/5th the circumference of the horn at a time. Since the dremel disk is tiny and there's the chance of indvertantly creating varying thicknesses, I stopped after each complete circuit around the horn and ran my finger along the inside to feel for variations. After the sanding was done, I polished it with a buffing wheel. If you look into the CAI/accordian side of your TB you'll see a very distinct ridge what seperates the larger bore horn from the smaller bore inner section where the plate it located. I completely removed that ridge. The transition from the larger to smaller bore is so subtle now that you you have to touch it with your finger to feel where the ridge used to be. While I was in there, I reduced the profile of the shaft even more.

Last night I did two sets of two-way 0-60 runs to document acceleration with the original bore.

Stock TB horn:

First two-way run average was 7.06 and the second was 7.13. Ambient was 70 degrees and humidity was 59%.

Modded TB horn: (+5mm)

First two-way run average was 6.77. Scratched twice on attempts at second set.
Ambient was 70 degrees and humidity was 56%.


Reflections on this mod.

For me a really helpful tool turned out to be a 4 piece drum sander set for my drill. It came with 3 sanding sleeves, fine, medium and coarse, and the drum sander itself. Since the drum was almost as long as the horn was deep, it turned out to be a great way to get a good, even grind. I used it on the IM side of the TB for a few minutes and easily removed 1mm.

I did eventually suceed in getting the 3" flap wheel into the horn, but it was such a super tight fit that my 3/8 drill bogged down. I had to give that up for fear I'd burn up my drill. I should've used the drum sander attachment a bit longer to enable an easier fit.

I expected maybe a .2 improvement to 60 from a standing start, and I observed a .32 improvment. Nice! I'l take that. Yes my old ass G-tech may be inaccurate, but I'm more interested in the difference between the pre and post mod times, not the times themselves. Yes it lacks the sensor to cancel vertical acceleration interference, but it lacked that on both runs. The .32 improvement is supported by the booty dyno as well.

To summarize, if you have trouble getting the 3" flap wheel into your stock horn, then you can quickly remove enough metal with the $4 sanding drum attachment to make that fit possible. Utimately you'll want to get the big flap wheel into the horn since it will enable the most even grind, with no deviations in bore at all. The cost for both those attachments wont exceed $10.
 

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Nice work :)

Not to burst your bubble but Shadrag ran a 6.75 on his atx, cp-e intake and springs. So I don't think your TB mod really improved 0-60times that much. Im not doubting though that the car is a bit more responsive though. Now do something about that Intake manifold for some nice gains :)
 

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I did the coolant bypass, but it still gets really :angry: considering it's bolted to the engine.
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we need a phenolic spacer now :yesnod:
 

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Discussion Starter #11
Nice work :)

Not to burst your bubble but Shadrag ran a 6.75 on his atx, cp-e intake and springs. So I don't think your TB mod really improved 0-60times that much. Im not doubting though that the car is a bit more responsive though. Now do something about that Intake manifold for some nice gains :)
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It improved mine .32 seconds. That's good for $8 in supplies.

Regarding the IM, I port matched it to my TB. I dremeled the IM inlet to also make it 65mm, like the IM side of my TB is now.

So you bored the horn to the butterfly and stopped there? or is the butterfly bigger as well?
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There's still about 3/8 of an inch in the middle of the TB that is still 60mm, the stock diameter. Still using the stock plate. The horn is 68.4mm and the back side of the TB is 65.3mm. I ordered a TB plate for $10, but the guy hasnt answered my email yet.
 

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Not to burst your bubble but Shadrag ran a 6.75 on his atx, cp-e intake and springs.
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I did power brake to get that number though, which Willow didn't mention. And I can't comment on the temperature and humidity because I didn't record it.

I have been considering TB mods (especially if it will give me another .2s or more!). Though with my luck, I would expect for my TB to go bad right after I put all the work into it.
 

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Discussion Starter #13
I did power brake to get that number though, which Willow didn't mention. And I can't comment on the temperature and humidity because I didn't record it.

I have been considering TB mods (especially if it will give me another .2s or more!). Though with my luck, I would expect for my TB to go bad right after I put all the work into it.
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Nope, no power braking here. :)
 

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Sounds like this might evolve into two suppliers one that does 2.3 work and another that does 3.0 work. I am sure both of you would be comfortable working with either throttle body though.
 

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Discussion Starter #16
GREAT JOB. BIG news. thats a LARGE improvement.
woot. ive gotta get a TB now and start fuckin with it. :)
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LOL....that's the spirit.


Start with a 60 grit 3" flapper wheel. Make sure your power drill is a good 6 amp model. My old crappy 4 amp one couldnt turn the flap without bogging down since the fit will initally be as tight as a nun's pussy if you manage to squeeze the flap wheel into the stock horn.

I invested in a new 6 amp model tonight though, and it spun the flap wheel with no problem though.


If you just cannot squeeze the new flap wheel into the stock horn, you'll need to use sanding drums initially like I did. No biggie though since the set was only 4 bucks.
 

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can you give us a bit more indepth with perhaps some pics of how you kept the stock butterfly?

im willing to bet it would take me FOREVER to do this with a dremel, that and i know i'd need a junkyard TB because i would need alot of time to make it perfect.


i cant get over the performance increase. bottlenecks bottlenecks bottlenecks!
 
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