3 inch downpipe flange

So i am making a 3 inch downpipe which is to be used on my Cosworth T3.

I have a Cosworth 3 bolt flange with the cosworth 2.5inch flare pipe and was planning to weld on a 2.5 to 3 inch reducer/enlarger then onto my 3 inch pipe. As per the pics below.

Questions

1. Could i do away with the 2.5 flare and 2.5 to 3 inch reducer and just weld a 3 inch V-Band onto the 3 bolt triangle flange ? Will bolting the flange to the turbo seal ok ?

2. Will my 3 bolt flange need to float enough to pass the bolts when removing the downpipe as currently i dont think i have enough 2.5 inch pipe to allow this.

Dat angle

Whats wrong with the angle im right hand drive remember.

chopperead said:

1. Could i do away with the 2.5 flare and 2.5 to 3 inch reducer and just weld a 3 inch V-Band onto the 3 bolt triangle flange ? Will bolting the flange to the turbo seal ok ?

2. Will my 3 bolt flange need to float enough to pass the bolts when removing the downpipe as currently i dont think i have enough 2.5 inch pipe to allow this.

Click to expand...

1. No. The flange presses the flare against the conical part of the turbo to provide a seal. The flange on it's own won't seal.

2. No. Once you've undone the bolts you can simply remove the whole lot. You don't need to remove the flange from the turbo first.

That looks similar to what I did to get my 3" on a conical 15g (2.25"), but I cut the conical part a little bit closer so that there was only about 2mm of play between the flange ring and conical pipe and welded my 3-2.25" transition from the inside, then buttwelded the rest from there. I would (at least this was how I did it) bolt the conical pipe and flange to a turbine housing, then slip the transition over the conical pipe until it almost touches the flange ring, and weld the conical pipe to the transition from the inside so your weld doesn't cause interference with the flange ring. After that's all done, you can take a 60 grit 2" flap wheel and smooth out your weld. This will also let you run an almost continuous bead to ensure sealing the joint.

Cheers guys.

I just wanted to make sure there would be enough rearward movement to allow the whole downpipe to slip off the bolts I guess if i was removing the downpipe i could unconnect the under car section first making it a bit looser.

The angle is fine. I hope that guy doesn't notice his over-axle pipe...

Get a 3 inch vband and weld that onto the turbine housing and the downpipe.

This is what a fellow T Bricker did with his 3 bolt Cosworth housing.

I cant see whether the conical flange is being used or not

If he has bolts, yes, the flange is being used.

I much rather use 3 inch vband and add flex pipes then using the concial flanges. Yes, it add cost, but it seals better and no issue of removal later on.

Just before I take it to my welder.