Modified 1.9 8V Throttle Body

[hoodygoodwood 71 3 Cars]

I decided to modify a spare throttle body from a 309 GTI to see what could be done to allow more air through it .I am not sure if this is the most restrictive part of the inlet system or even if the engine could use more air but I will try it out this summer once my Goodwood is back on the road .

The spindle is 10mm diameter and presents quite a resistance to air entering the inlet manifold , the blunt edge to the throttle butterfly cannot help either .

The spindle runs in 2 steel tubular bushes that are a tight fit in the TB casting , an orange bush provides the sealing against air entering each end .Turned the spindle down to 8mm dia on my lathe , could have gone smaller but the 2 screws would not have had much metal left to grip .Machining it down on a milling machine would have been better but I do not have access to one .

Deburred everything and gave the TB a thorough clean inside and out . The machined taper downwind of the butterfly was very rough so I smoothed it out with wet and dry .Before refitting it I carefully filed a 45 degree chamfer onto the leading edge of the butterfly making sure it was not on the side that almost seals off at tickover .

I then reassembled everything as before .

Got my calculator out and I make that a 6 % increase in area at wide open throttle , will it help ? we will see .

[DamirGTI 342]

Interesting .. i did almost identical job on mine few years ago !

 

Does it have any effect ? i really don't know .. i did this with a whole lot of engine mods so cannot speak for just this one .

But every little helps when chasing all the possible upgrade benefits from an engine ! up to what extent , that'll be kinda "item specific" .. this one should show some flow gains , not much but some do (it's already good as an OE part thus theres not much to gain by modifying it ..) .

 

D

[nick205 12 5 Cars]

Nice to have the skills and tools to do this kind of thing.

 

I can't see it making a noticeable difference until it's at full throttle - although I guess that's where you want the difference really.

[sub205 5]

I testet both the stock throttle and the slightly larger one from the XSI/S16 ... no noticeable difference.

I'm curious to see what the RS-throttle is doing this season, have to wait till april, unfortunately ...

[Dizzee stuff 33 1 Cars]

I have done similar mod back in my mini days but you could remove a lot more material, hand file the spinle flat either side of the screw holes. A mod done by David Vizard.

Edited February 6, 2014 by Dizzee stuff