Turbo Waste Gate Flapper Mod

[Bonjaz]

thanks very much hi psi much appreciated

[johno]

I just had my turbo rebuilt, and my rear housing was cracked real bad. New housing fitted. The bloke buys the housings allready ported ( ATS in Adelaide). 30mm seems to be the normal opened up size.

[Ralph Wiggum]

  On 30/11/2011 at 8:45 PM, JVK said:

Anyone come accross the larger flapper catching on the port and the way around it ?

You need too mill a small amount of material out of the side wall of the housing(red area) and also ensure you dont take too much material (how much is too much,.....???) out of the top of the port (as marked with red lin in picture) the port should resemble a "D" with the flat side of the "D" being the ares uner the swing valve pivot.

Dont forget too open up the throat of the port from inside the housing and make sure you blend the edges of the port inside and out too prevent cracking (it will still crack eventually but no need to encourage it!). i normally create a channel inside the housing to help direct the waste gas through the port.

There some good info here about porting and blending the inside of the exhaust housing. Pics/story relate to a Mazda Miata/MX5 but you'll get the idea. I dont tend too go as deep with the channel but I do make it wider and make it widen out too the full width of the exhuats inlet port towards the bottom.

http://www.bellengin...articles_id=273

Oh and thanks for the Pic 1600Dave!

[arronm]

  On 29/11/2011 at 6:13 AM, Bonjaz said:

bump what is the size of the hole stock and what are people porting them out to??? is 30mm enough???

STD flapper is 33mm and hole is 26mm. So if the new flapper is 37mm then I suppose the new hole will be about 33mm.

26mm area = 530.92mm2

33mm area = 855.29mm2

Edited 01/12/11 12:37 AM by arronm

[Ralph Wiggum]

^ There isnt really an answer too "what size are people porting them out too" The hole isnt round when finished, as mention it should be a D shape. As I mentioned earlier in the thread, I usually leave aprox 1.5mm over lap.As Aronn mentioned the oold flapper is 33m, with this overlap the "round" section of the new port is aprox the same diameter as the old flapper valve. But the squared off section reduces the overall area. Porting and blending the inside of the exhaust side helps overcome size increase lost too this area.

[Bonjaz]

thanks guys very much appreciated

[1600dave]

I ended up buying a 2nd hand FG housing that has been ported but never used. Dunno who did the work, but its a nice job, ported more the way Luke suggested, and nicely blended/flowing. The flap is huge, 43mm and the port would be close to 40mm across. Minimal overlap, but it seals.

Now just to fit it, and the rest of the good bits!

[JVK]

Thanks for the info Luke ,I didnt Quite do the D shape as such but did open up the port considerly and the associated blend work but was worried about the flap catching on the edge of the port due to the way I had opened it up (before the flap was tigged) so I ended up putting a slight chamfer on the outer edge of the flapper face just for that extra bit of clearance when it returns shut.Maybe not the best solution but it works fine.I did also relieve the chamber in the area you marked in your pic.I guess on my next one I will pay a little more attention Lol.

[johno]

I thought the FG turbo is different to the BA/BF?? Maybe that's why the flap and port are so big?

[Bonjaz]

both turbos have the same rear housing but from what I have read the fg has a bigger different shaped hole and flapper standard? I am interested to see how an original ported ba/bf rear housing would go on a fg turbo front housing...would it even be benificial or are the fg ones better from stock???