mesospeedy

iTrader: (8)

well i have a set of qtp headers begging to be installed on my car, but i can't decide on the rest of the exhaust. i know that keeping the loudmouth won't sound good (i've heard it in person) so its either ory and some kind of muffler to replace the resonator or true duals. i know a guy who can do 2.5" td's out the back for just slightly more money as a qtp ory and replacing the resonator. but how well will crush bent duals flow? the guy has done this setup on a '94 Z28 and it is the nicest over axel setup i've seen. i'm planing on 2.5" orx and sweet thunders, i know that will sound hella sweet! but will i gain any hp over the lm setup?

Redneck Z

iTrader: (3)

Crush bends suck and will never find their way onto my car! A crush bent 2.5" true dual exhaust will flow worse than a 3" single exhaust. If the search button would pull up older posts, I'd show you dyno's of significant gains going from a crush bent TD, to a single y-pipe.

jmm98LS1

iTrader: (28)

+1.....mandrel bent all the way.

GuitsBoy

iTrader: (4)

Please substantiate this with evidence. As for the dyno comparisons, there may be another factor coming into play here. Perhaps the center of the X pipe narrows down to a single 2.5" pipe thus creating the restriction. If that were the case, its due to a faulty X pipe and it wouldnt matter if it were using mandrel bends.

Here are the calculated areas assuming a .065 wall thickness

Single 3" pipe has an area of 6.466 sq. in.
Mandrel 2.5 True duals have a combined area of 8.819 sq. in.
Crush bent 2.5 x 2" oval tubing True Duals have a combined area of 6.958 sq. in.

As you can see, crush bent true duals have a half sq. in. more area than a single 3" mandrel bent pipe, not to mention you still get the scavanging effect from the X or H pipe.

If you have the means, I still highly suggest mandrel bends, however, they wont choke you out as bad as it might seem.

mesospeedy

iTrader: (8)

thanks for the replies. some dyno comparisons would help, but guitsboy has some good info. i could try to buy some pre bent pipe and have it done with that, but i'm not sure if he would go for it, it might be harder to fab up like that. i'm sure it would be more expensive too. i want duals mainly for sound, but i don't want a dumped setup. if anybody else has any info or dyno numbers please let me know asap.

Redneck Z

iTrader: (3)

If the search button would pull up older threads I would. I have seen many dyno's where guys have gained significant hp when going from crush bent TD's, to a good y-pipe setup. Area doesn't tell the whole story. Don't forget about the turbulance and associated energy/hp loss that crush bends cause. It sounds like you are more concerned with sound than power, so I wouldn't worry too much about it. You may make a little better power with a good y-pipe setup or mandrel bent TD's, but it shouldn't hurt you too bad.

GuitsBoy

iTrader: (4)

This is true. However ive seen people gain going TO crush bent duals from a loud mouth. The dyno dosnt necessarily tell the whole story anyway, I recently gained 16 RWHP simply by doing three consecutive back to back pulls. No changes were made to the car. Go figure.

MDoe8

iTrader: (3)

Would a crush bent 2.75" or 3" true dual flow as well if not better than a 2.5" true dual mandrel bent?

99Hawk262

iTrader: (19)

I started with crush bent 2.5" duals dumped when I put on my Pacesetters. I went from 13.62 @103 to 12.98 @ 107.7. My butt-meter told me I gained a lot as well. I think I did pretty good and I doubt I would have gained much more with mandrel bent. Now I have mandrel bent to the mufflers and crush bent behind. I'll fix it some day, but it works for now. And I can always take the pipes off behind the mufflers and run mandrel/dumped if I want to be really LOUD.

s346k

iTrader: (4)

i don't think crush bent true duals would show a noticeable loss in performance compared to a mandrel bent setup. simply because there really aren't that many sharp bends in a GOOD true dual setup.

i think the only time you MIGHT see a difference would be a sloppy 3" crush bent true dual system (+ x pipe) vs. a mandrel bent 3" (+ x) over the axle comparison.

MDoe8

iTrader: (3)

do you think a larger diameter crush bent setup would equal that of a smaller mandrel bent setup tohugh? I'm thinking of going 2.75" crush bent vs. 2.5" mandrel bent

MDoe8

iTrader: (3)

Bump, I'm still curious

Redneck Z

iTrader: (3)

Just do mandrel bends, then you won't have to worry about it! Do it the right way the first time.

ChocoTaco369

just buy a TSP true dual system with sweet thunders. that, i believe is mandrel bent and only costs $400. then, just have the exhaust shop cut off the turndowns, weld pipe onto it and bring it out the back. problem solved. prolly be a hella cheaper too.

01bird58

iTrader: (9)

Sorry if im stealing the thread, but what exactly are the definitions of a mandrel and crush bend.

MDoe8

iTrader: (3)

mandrel bend maintains the perfect (for example) 2.5" diameter all the way through. A crush bent is just that, crushed. It's like taking a hose and putting a kink in it, only it just blocks off a minimum amount of diameter on our setups.

Anyone have any other input on the power difference between a 2.5 mandrel and a 2.75 crush?

-Mike

TheBlurLS1

iTrader: (8)

My system has crush bends after the bullets, you can see pics in my signature. It's 3" crush bent, so it flows plenty.

Wyckedcamaro

iTrader: (2)

i have mandrel bent true duals over the axels.

I paid a kings ransom for it.. but i LOOOOOOOOOVE IT SOOOOO MUCH!

BrianC98Z28

iTrader: (11)

Personally I dont see how this is even a question. Mandrel bent all the way. Just buy the universal x pipe kit and have it made to fit.

MDoe8

iTrader: (3)

Well, my ecxhaust has to be custom made anyway. It's not going on an fbody. There is no such thing as true duals on my car that aren't custom. I know someone who can make it wth crush bends for dirt cheap, that's all.

-Mike