View Full Version : Downpipe Design

6th February 2003, 17:51
I'm thinking about making a downpipe for my 99uk. I've concluded that the best way would be mandrel bent stainless, 2.5inch diameter (to match Magnex mid section which I think is 2.5 inch??) and with a bellmouth design and tig welds. I reckon I can do this at work without much problem. I haven't looked yet though..... does the downpipe have heatshield mounts? Do i NEED the heatshield?
Finally, will I see any overboost or probs. on a uk my99 turbo with magnex mid and bb and k and n 57i?
The more help I get, the better this downpipe will be and I will be able to flog a few considerably cheaper than anything else on the market!!

Cheers people!

Danny Fisher
6th February 2003, 18:53
You shouldn't get overboost issues with just an exhaust system and an air filter.

As for the heat shield, I wouldnt worry to much. I have been running without heat shields on both the downpipe and turbo for ages, like a lot of other people on the BBS.


6th February 2003, 19:13
Have you seen this one for sale?


6th February 2003, 19:26
Good bit of marketing there!!!

Why buy when I can make my own!!

Isn't it agreed that a bell mouth is better for maintaining steady boost pressure as aposed to a twin dump????

6th February 2003, 22:05
I take it you've read the recent thread on here about Exhaust Design (http://bbs.22b.com/ubb/Forum9/HTML/000163.html) which was joined near the end by Michael South who has some ideas about downpipes.


10th February 2003, 22:06
Thanks for the replies! Yes, I have read the thread from the garrett guy!
I've decided on a bellmouth design with a splitter in the turbo housing.
I'm going to extend the "bell" about 10 inches down the pipe, tapering to 2.5 inch tube. I'm also going to smooth off all the welds and lips that form inside.
I'm hoping this will give me the best low down torque response but only time will tell.
I'll try and get some before and after data for those interested.
If i've missed anything then let me know guys! (and girls).