A2 1.4TDI AMF BHC Downpipe - what is the ultimate design - buy or make?

dieselfan

Member
Have searched for a decent downpipe for my AMFs. Have not find any and have made to attempts my selves while waiting for the ideal design.
If it is available to buy... thats good, but if any have a clear idea wrt design that is also worth its weight in gold (bhp) :)

The big disadvantage with what I have made until now is that I have not done any dyno before and after so I have no clue of the improvement numbers... I did first attemt in 60.3mm x1.5 (2.36 inch) down to cat.
This version "feels" to improve low rpm response and ease breathing in general.

1. What is the ideal diameter for a downpipe that shall handle up to 110-120bhp ?

2. Are there any downpipes available to buy that are

3. Have any of you done any dyno testing so you know the benefit of standard vs tuning downpipe ?

4. Any that have tested if there is a benefit to increase bending radius from 3xD to 5xD ?

5. Do any of you have pictures or links to a downpipe that looks promising ?

I hope a lot of you want to participate to the evaluation :)

Cheers dieselfan
 
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Have searched for a decent downpipe for my AMFs. Have not find any and have made to attempts my selves while waiting for the ideal design.
If it is available to buy... thats good, but if any have a clear idea wrt design that is also worth its weight in gold (bhp) :)

The big disadvantage with what I have made until now is that I have not done any dyno before and after so I have no clue of the improvement numbers... I did first attemt in 60.3mm x1.5 (2.36 inch) down to cat.
This version "feels" to improve low rpm response and ease breathing in general.

1. What is the ideal diameter for a downpipe that shall handle up to 110-120bhp ?

2. Are there any downpipes available to buy that are

3. Have any of you done any dyno testing so you know the benefit of standard vs tuning downpipe ?

4. Any that have tested if there is a benefit to increase bending radius from 3xD to 5xD ?

5. Do any of you have pictures or links to a downpipe that looks promising ?

I hope a lot of you want to participate to the evaluation :)

Cheers dieselfan
Darkside Developments have a 2.5 Inch Decat Downpipe for an A2 TDI AMF
 

Menno

Member
Don't have a clue what could be the best design (as straight as possible?), but I've replaced my shot/leaking flex bit on the downpipe of my former Arosa TDI (same AMF engine).
I welded in a flex pipe with a bigger diameter, and it picked up rev's quicker......... but I must say that when i was busy with it, I also removed the cat, which is a greater restrictor then the downpipe itself I guess.
Going larger in downpipe diameter is only a plus if you would install a bigger turbo and remove the cat, but I could be wrong.
 
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Pinkythelabrat

A2OC Donor
You might also need to be a bit careful - bigger isn’t always better because you do need some pressure wave movement for scavenging I’d exhaust gases on the next stroke I think. If you have a choke point it’ll cause rebound too.

It may be less relevant for turbo engines but Engineering Explained has a brilliant video on the function of the exhaust in assisting engine power and the role of performance exhausts. I’ll see if I can find it.


I love this guy’s channel.




Sent from my iPhone using Tapatalk
 

A2Steve

A2OC Donor
I had a custom decat down pipe made up on on my last project car by a company called Longlife exhausts. 2.5 inch stainless steel and it really made a difference to the pickup on the turbo. It cost £250.
 
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