my big bore throttle body

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kevo
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Post Sun Aug 10, 2008 8:49 pm

how do all, i've made myself a big bore throttle body, after considerable investigation i discovered the diameter to bore it to, and it was pretty much as big as you can go. heres a couple of piccy's.

firstly stripped the thing down and strapped her down to the machine bed, i bored it out to 57mm up 3mm from the standard 54mm.

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next came making the throttle petal, the first thing to do was to calculate the angle of the thing as it's not round but eliptical. i measured it and measured it then estimated it and ended up coming to the angle of 14
degrees, at this point i noticed that there was a number stamped on the front of the petal, funny enough it was 14. ah well i wasn't to know, but it was nice to confirm it anyway.
so on to manufacture, firstly i turned down some aluminium bar 57mm, next came to machine a 14mm angle into the face of the bar, once this was done a 3mm sliver of it was cut off in the band saw at the approximate correct angle. this was then skimmed to a final thickness of 2mm and cleaned up and finely deburred syill leaving a tidy sharp edge.
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here you can see the finished product next to the original, with the all important now eliptical shape and the edges cut to fill the form of the inside diameter fully and neatly.

next came the fitting of the thing and assembling the nightmare like springs that clip and attach to everything and catch your fingers continuously, i knew i should have paid more attention when i took it apart :roll:
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anyway heres the finished product all finished and fettled with a nice tight seal all round the butterfly.

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I'll be fitting it in the next few days and will let you know if it makes any difference.
Kev
march109
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Post Sun Aug 10, 2008 8:59 pm

Your getting pretty handy lately, considered selling those?
325i Tech 1 Touring, breaking.

2.5 high comp. M20, 3.64 LSD, Fully undersealed, Spax springs & Bilstein shocks, s/s exhaust, Alpina rep wheels and more.
zaust
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Post Sun Aug 10, 2008 9:02 pm

Nice work fella. It will make a difference, When you know it work's fine it will be worth filling the screw head's and smoothing them off too...
M30 Tech 1 Touring on gas.
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Wilson325i
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Post Sun Aug 10, 2008 9:03 pm

nice work, but i can not work out what car that is from.
DHFiS
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Post Sun Aug 10, 2008 9:05 pm

Wilson325i wrote:nice work, but i can not work out what car that is from.
M42?
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hoshy
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Post Sun Aug 10, 2008 9:20 pm

yeap - looks like an m42 tb to me.
E46 M3 CSL but dreaming of another E30.
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kevo
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Post Sun Aug 10, 2008 9:47 pm

oops sorry yeah its my m42 318is tb. i doubt i'll be selling them tbh, but never say never.
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kevo
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Post Tue Aug 12, 2008 11:27 pm

tried it on the car just now and it made a good difference, the car is a lot freer revving up the higher end of the rev range. a definite improvement. what did others who have it done notice?
Kev
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Post Wed Aug 13, 2008 1:03 am

Well done Kevo, that's impressive.

If you do decide to offer these, let me know. I would be interested in getting one.

I know Feens has one on his IS and found it made a good difference.

I have one for my 325, but haven't got it fitted yet.
e301988325i
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Post Sat Aug 23, 2008 10:44 am

I had a similar style twin throttle body on my previous french bag of **** R19 16V.

I took a spare body apart and milled each butterfly spindle to 1mm thick each side, across the whole width of each butterfly, and shortened the screws to suit. Thereby increasing the area.

I also took the butterflys to the linisher and tapered them to a thickness of 0.25mm into the airflow increasing to 2mm at the spindle. You have to be carefull here as you can only linish one side without wrecking the seal of the buterrfly, and it's easy to slip.

Doing these 2 things made a big difference, enough that after a high revs run it wouldn't idle properly as the ammount of extra air confused the ECU when it was idling.

I've also done this to my 325i throttle body which has made a noticeable difference.

Anyway, nice work all the bset
I said:

Can anyone suggest how to test if the boot lights are staying on with the boot shut?

e30topless said:

lock the wife in there