crich88848

So I am planning on doing some modding here in the next couple of months and have been doing some research on headers and downpipes. I was reading a thread on here about a guy that was wondering if he should get DT headers or a high flow catted downpipe. Now bear with me here as I am not an automotive genious, by why can you not do both? Do the DT headers eliminate the downpipe or what? I am very curious about this as I am in the city and need a cat for emissions. I plan on going with a magnaflow catback as well, also curious if I should get a wideband O2 sensor and would appreciate any thoughts on that (I do plan on getting it tuned this summer after I get some mods on it). Thanks in advance!

wesdean78

A lot of people have been asking me that question through my site (LS4Store) recently. Here's a picture I just found online:



The downpipe is the plumbing surrounding #13 on the picture -- it goes between the rear exhaust manifold (#18) and the resonator (unlabeled, but just above the "< FRT" arrow).

Doug Thorley headers include this plumbing already. Here's a picture from the Doug Thorley web site:



So, to answer your first question ("Do the DT headers eliminate the downpipe or what?"), the answer is yes.

I use a universal Magnaflow catalytic converter as well as a Magnaflow catback like you've mentioned. I also have a DMH cutout installed roughly above where #8 is in the first picture.

I don't run a wideband O2 sensor, but I don't do a lot of tuning beyond what DiabLew helps me out with.

I hope that helps.

crich88848

Is there more piping that comes with the DT headers or is there some fab work that needs to be done to get the headers to the resonator flange? It appears from the picture you show that the piping on the headers won't reach all the way back to the resonator. You know I was just thinking today that I might want to put a cutout in there as well, how does that position work out for you? I am probably going to go with the diablew tune as well as I am not experienced tuning and don't want to mess anything up, so if I go that route I don't need to get the wideband O2?

wesdean78

Here's a link to the installation instructions (the disassembly instructions are on the other side of the paper):

http://static.ls4store.com/static/im...stallation.png

Here's a picture I took of the headers before I installed them in my car; the headpipe on the photo seems longer than the prototype image..



In the stock configuration, the catalytic converter sits between the rear exhaust manifold and the resonator on the downpipe. During installation, you'll cut the downpipe off before the catalytic converter and weld it onto the headpipe off of the headers. The portion of the downpipe that you'll be using will have the flange to mate up with the resonator. You'll also need to weld the crossover pipe to the headpipe.

The position of the the cutout works well for me. If it were anywhere else, I imagine it would be even louder in the cabin than it already is.

As for working with a DiabLew custom tune, Lew will send you instructions on how to log data using your DiabloSport tuner. You'll collect some data, export it off of the tuner to a PC, then email it to him. He'll do his magic on it and email you back a custom tune. You then install the custom tune, test it out, and repeat the process. Lew's a great guy and he really knows his stuff, so I wouldn't hesitate for a heartbeat to go back to him for tuning.

crich88848

Thanks for all the info! I think I got a pretty good grasp on it now.

DougThorley

There is one weld required which is from our down pipe to the inlet of the factory cat. The slip fit on the connector pipe gets clamped with the supplied band clamp.

Thanks!