wastegate exit pipe to exhaust

[GazzaG60]

Guys i know at least Jamo is aware of this and it wont bother the cast guys too much more the tubulars but will have an effect for sure.

over the last couple of weeks i have been testing at higher boost levels and in general been using higher boost more. last week i did a motorway run and i think the resulting boost runs have had an effect on the manifold wastegate tube.

i have been running the stock exit pipe from the wastegate and now feel the bottleneck it causes has caused high egt in the wastegate feed tube causing the metal to become softer eventually cracking. now with cast it wont be as evident but surely it would cause a generally higher egt in the full cast unit.

the beauty of the tubes is its 2 hours to strip the full lot off from start to finish. today ill get the manifold welded up but i need to get a wastegate tube to prevent this in future. i dont think it mattered at lower boost but at the higher levels say 1.7 and above it matters

does anybody make these to replace factory pipe.

cheers

[terrybullwon]

So your after just a wastegate flexi?

[GazzaG60]

no i want a replacement pipe for the factory flexi. or can you mod the facory one for bigger bore.

its tiny in there and i want to rid it of the restriction. the rest of the manifold is as new.

[Jamo]

You can have these made by an exhaust place probably the best bet Gazza as instead of buying new flanges I had them cut my old flexi for the flanges and remake it.

The OEM flexi is a joke, the pipe inside is only 1", I had mine made from 2"

[terrybullwon]

Um.... I have a flexi in about 1.75" or something you could have but its not got the oem flanges on... If you could get them i could put them on but i would need to check the length of the OEM flexi first

[Billman]

In my new exhaust i have placed the the original flexi approx 50cm after the WG and the WG pipe come in the exhaust stream just before the cat.

[JP]

Couple of things that you need to keep in mind.

As you turn the boost up there is more exhaust gases, doesn't matter how big the hotside is the amount of exhaust gases the engine produces are way too much to pass through the snail. So the wastegate now becomes a crucial part in venting of excess exhaust gases to retain a sensible EGT. So the bigger the wastegate the more exhaust flow you can bypass once at peak boost, to the extend that we once changed a 38mm wastegate to a 50mm on a 3071 with .82 housing and gained close to 40hp (37 iirc) at the top end.

Now the stock Audi wastegate is only 30mm so by the time it has gone through the less than ergonomic valve and round the poorly flowing chamber and made it's 90 degree turn a 25.4mm pipe ain't far of the mark for flow.

Make the wastegate flexi pipe larger and it will benefit to certain degree firstly you will reduce the core temp of the pipe, secondly the pressure drop will help scavenge some of the gases from the wastegate main chamber. Much like the design of a 2 stroke exhaust system.

However this is where the problem occurs the bottle neck is now the wastegate itself. It does not flow very well, I spend a good while on mine reshaping the insides and reprofiling the valve. The end result being no more EGT peak spikes of a 1000+ celsius instead a steady max of around 925. Still running the original wastegate pipe.

Leading me to believe that unless you are upping the wastegate spec by porting or purchasing a larger one then there is no real point in upping the pipe diameter beyond stock.

As a reference point my mates silly 1.8t at 2.3bar of boost and 750hp see's maximum EGT's of around 768-775 celsius down the quarter mile and flat out on a track. He's running 40mm internal dia runners to a twinscroll 1.06 backhousing and a 60mm wastegate. the intend being to turn the boost up tweak the cams and add some nitrous for next season to bring the EGT's into the high 800 bracket as at the moment we feel it is too cold.

[GazzaG60]

i have my exhuast fine billman. is the tubular thats taking the brunt of only 1" of pipe as jamo says. i was horrified to see it i must say.

ill pop to the exhaust man i think.

cheers guys

[GazzaG60]

thanks for the rwd.

i was thinking of a wastegate change. think ill start with the pipe.

my egt only hits 750 or so at 1.9bar. the sensor is not on the gate or manifold though. its about 2 inch from the hotside. so although my egt is good there. at the gate i feel its hotter hence the issues. i have thought about open dump as we have seen grerat results on these on subaru when the flow becomes a little restricted. id rather not though.

any recommendeatinos on gates and fitment from btdt.

[Jamo]

Couple of things that you need to keep in mind.

As you turn the boost up there is more exhaust gases, doesn't matter how big the hotside is the amount of exhaust gases the engine produces are way too much to pass through the snail. So the wastegate now becomes a crucial part in venting of excess exhaust gases to retain a sensible EGT. So the bigger the wastegate the more exhaust flow you can bypass once at peak boost, to the extend that we once changed a 38mm wastegate to a 50mm on a 3071 with .82 housing and gained close to 40hp (37 iirc) at the top end.

Now the stock Audi wastegate is only 30mm so by the time it has gone through the less than ergonomic valve and round the poorly flowing chamber and made it's 90 degree turn a 25.4mm pipe ain't far of the mark for flow.

Make the wastegate flexi pipe larger and it will benefit to certain degree firstly you will reduce the core temp of the pipe, secondly the pressure drop will help scavenge some of the gases from the wastegate main chamber. Much like the design of a 2 stroke exhaust system.

However this is where the problem occurs the bottle neck is now the wastegate itself. It does not flow very well, I spend a good while on mine reshaping the insides and reprofiling the valve. The end result being no more EGT peak spikes of a 1000+ celsius instead a steady max of around 925. Still running the original wastegate pipe.

Leading me to believe that unless you are upping the wastegate spec by porting or purchasing a larger one then there is no real point in upping the pipe diameter beyond stock.

As a reference point my mates silly 1.8t at 2.3bar of boost and 750hp see's maximum EGT's of around 768-775 celsius down the quarter mile and flat out on a track. He's running 40mm internal dia runners to a twinscroll 1.06 backhousing and a 60mm wastegate. the intend being to turn the boost up tweak the cams and add some nitrous for next season to bring the EGT's into the high 800 bracket as at the moment we feel it is too cold.

There are 2 wastegates one is 34mm, older WG are 30mm

http://www.s2forum.com/forum/showthr...237#post367237

This size difference makes a hell of a difference as Newsh can testify http://www.s2forum.com/forum/showthr...0mm#post367238

[GazzaG60]

cheers jamo. ill take a look at the pn after.

when i unstick it from the flange.

[JP]

What engines/years did the 34mm one come on? I want!

[Jamo]

AFAIK It's the 3B that have the 30mm and the post 1993 ABY / RS2 had the 34mm

[GazzaG60]

well mines a 95 N aby so it should be 34mm. dont help when you only got 25mm for gases to get out

[Rusty]

Off the family album -

034 145 705

A = MB
AA = WX
B = 3B, RR & AAN (Checked 93, 95 & 97 !)
E = ABY & ADU
T= WR & GV