Is Mandrel-bent Mandatory?

[joemathews]

A buddy of mine works for a shop that soups up 300zxs, Integras, and other sports cars, and sells them modded for thousands more. He says that he has an extra dual-tipped muffler (one of the ones with the dual tips that point upward out the end of the bumper) that he'll give me for $30, and he can get me the "Street Scene Motorsports" (the company) discount at a local muffler shop for 3 inch piping all the way back welded to the muffler and hung on my car for $100.

I'm pretty sure the muffler shop will be doing press-bends rather than mandrel bends. My question is how important is it? I mean, I understand that mandrel bent piping stays 3" all the way through, and that press bent can be more restrictive at the bends, but if it is only going to cost me a few hp of restriction, I might go ahead and do this for a $130 exhaust setup.

What do you guys think? How important is mandrel bent piping exactly?

[JoeWagon]

Well, the more angle, the flatter a press bent pipe gets. If they do a pretty straight design, which they will because it takes the least amount of time, it should still be decent. 3'' press has got to be almost as good if not better than 2.5 mandrel, which has run quick times all over the place. I say go for it, but skip out on the Shogun muffler (dual tips angled up). Get something that looks stock, or an Ultra-flow round.

[kjewer1]

Yes, it is generally accepted that a crush bent pipe will flow at least as well as a mandrel bend one size smaller. I have one small crush bend in my catback, doesnt seem to be hurting much.

An alternative is to buy the required mandrel bends, and have them weld it up. This is how i built my exhaust. The one crush bend comes from a slight "adjustment" that had to be made for better ground clearance.. When I had the same shop modify my DP to be a full 3" to a 3" O2 housing, I just brought a new flex, the 90 degree mandrel bend, and a 3" flange. It takes about the same amount of time to weld up a joint or two as it takes to crush bend a pipe, so price shouldnt be affected. This way you get mandrel bent exhaust from a shop that doesnt do mandrel bends... BUT, I Wouldnt worry too much about having them crush bend you an exhaust. Odds are it will support all the power you plan to be making any time soon, and its so cheap its no big deal if you decide to upgrade it later. Could probably sell it easily too.

I Would also skip that muffler, classic ricer material. But hey, if the price is right... I would also suggest the usual Dynomax Ultraflow Welded for 60 bucks. The magnaflow version might be a bit cheaper. For a cat back all you would need is the muffler and 2 45* bends if you plan to go that route... Somewhere on this site I believe it was 95gst (hard to remember all the screen names) that did a silimar homebuilt exhaust and posted some good pics. If you can find it you'lll get some idea of what the hell we are talking about, and can relay that to the shop. This could be a nice cheap way to go, but if the shop douches the project you may regret it...