I recently completed the fabrication, installation and testing of a 2.5� Twin Dump Pipe.
The results were favorable, the 3 Sections showed a 10 HP Peak gain and 10-ft lbs. gain in torque.
(The muffler remained stock) I believe these numbers are conservative, another 10 or 15 percent is most likely. See the HP and TQ Charts for complete results. Picture
A little background on how the pipe was made: I started with a Stromung Cat�d Downpipe to which I added a 1.5� second pipe and a wastegate separator:
The 1.5� piece was cut from a 304 stainless 180 degree U-Bend and the separator was cut from a piece of 2.5� tubing. A 1 & 5/8th� hole for the dump pipe was machine drilled and then the parts were hand fitted. (Lots of Dremel and hand filing). Picture
The dimensions and position on the separator are critical or it will hit the inside of the Turbo housing or the edge of the gasket.
After Swedging the 1.5� tube into the 1 & 5/8th� hole, the pipe was TIG welded, the flange was then surface ground a couple of thousands. Finally the separator was TIG welded to the 2.5 pipe: Picture
I trimmed the turbo heat shield to allow clearance for the Twin Dump. (I tried to leave as much of the heat shield as I could for max. heat protection and retaining most of the attachment holes) Picture
When installing the Downpipe fitment issues were minor, though I had to open the attachment hole (where the pipe mounts to the transmission) by about a 1/8th inch then add a spacing washer to reduce the pre-load on pipe.
After completion of testing with just the Twin Dump Downpipe, I installed the Stromung 3d Cat Eliminator and Center Section Pipe. Picture
Again fitment issues were minor, though I needed to purchase bolts for the Downpipe to 3d Cat Eliminator pipe connection (because previously there was a stud) and the Center Section Pipe to Muffler connection. (The stock bolts were too short as Stromung flange was thicker).
Also the hole in the stock rubber exhaust hanger was larger than hanger of the Center Section Pipe, so I added a piece of hose material to the pipe hanger to take up the space.
I was happy with the end results of the project. The design, building, installation and testing all went pretty well with only minor problems. The test results showed a good power/torque increase, I was particularly happy with the newfound torque in the lower RPM�s. Picture
The only area of disappointment was the small increase in Power/ Torque when adding the 3d Cat Eliminator pipe and the Center Section Pipe. I actually lost about 1 HP down in the low RPM but gained a bit up high. (I thought that I would have gained more from this part of the modification). Picture 1 Picture 2
Note: This exhaust system is intended for racing purposes only and may not meet emissions standards.
Special Thanks to:
Scott Taylor at Stromung Exhaust Engineering (Exhaust Components) www.stromung.com
Clinton and Joe at Custom Aircraft Parts (TIG Welding) www.customaircraft.com
Buns Stainless (304 Stainless tubing) www.burnsstainless.com
Race-Technology (Data Acquisition) www.race-technology.com
Harry at Cerco Tool and Manufacturing (Machining)
1/29/03 Copyright 2003, skoshiracing