Mandrel Bent Exhaust - Do You Really Need It?

[sketchman]

I just got a downpipe in for my B6-ME swap, and I was instantly horrified by the crush bend. It looked mandrel in the image, but wasn't. I'm kinda fanatical about stuff like that. I know it doesn't flow as well and it just looks ugly. Yep, I know nearly no one will ever see it, but it just looks wrong to me.

So then I had a thought. Does it really matter anyway? I've always heard it does, and it sure looks like it would.

So I googled it, and well, it's really not that much of a difference.

http://www.bobsmuffler.com/dyno.htm

The website I linked says 3-5% gain from mandrel bends. But the thing is I've called around locally to price a full catback for a Festiva before. It was pretty cheap compared to ordering bends and lengths and doing it myself the "right" way.

I guess if every HP and TQ counts on a race engine, sure mandrel it up, but I'm not so sure anymore on a street car. You could easily compensate for the 3-5% loss by going up a size when you go to get your system done, and then there would be no loss at all.

Thoughts?

[villageidiot]

Check out http://www.coneeng.com they sell bends very reasonably, I have the luxury of them being 10 minutes away. I also have the luxury of access to a mandrel bender for stainless exhaust, though the smallest it bends is 2 1/4" so, too big for most festivas.

Even with access to all the stuff to do it "right" I still use crush bent exhaust on 90% of what I do. As long as it's not the crush and multiple little kinks....... That's just wrong.

[sketchman]

The only places I looked before were summit and eBay. I'll check them out.

You could further help with the flow by just using a bigger size in the bends. Maybe 2" straights with 2.25" crush bends in between. So you'd still get no loss in the bottom from too big a pipe coming off the cat/DP/header/etc but the bends wouldn't be choked off.

[bhearts]

3 to 5 percent would be the same as upgrading from stock air filter to a "cold"cone filter. Mandrel bends aren't terribly priced anyways, like 15 dollars a piece. And the festiva needs 3 90s and a 45? That's not terrible considering it'll be a mod to make you enjoy your car, and the satisfaction in knowing it was right. I like Columbia river mandrel for my orders

[Hot_Wheels]

I have ordered alot from http://www.mandrel-bends.com/catalog/. Thet sell kits too. I ordered the stuff for my headcollectorser and intake from them. I also use coneeng for collectors

[villageidiot]

And do yourself a favor and do it in 304 stainless, so ya only have to do it once

[bhazard]

I really wouldn't worry about it on a 80-some horsepower engine

[sketchman]

^My thoughts exactly.

[Aaronbrook37]

I really wouldn't worry about it on a 80-some horsepower engine

Agreed completely.

[bhearts]

But similarly enough. What's 3 percent going to be on a 400hp setup. It'll be just as unnoticeable or noticeable of a change for both.

[sketchman]

On the dyno sheet that the link shows it was something like 8hp gain on a 157hp engine.

On a 80hp 3.5% hit is only 2.8hp. I doubt you'll ever notice, and you could probably gain that back with increased ignition timing and higher octane fuel or just running a free flowing muffler and intake.

[bhearts]

So you'll only do the mod if your guaranteed 10 percent?

[sketchman]

Nah. But with this example to get the parts yourself it's $5 for a 2" crush bend vs $15 for a mandrel bend. Is 3 times the price worth a 3-5% difference which equates to probably 2.5-4hp with my engine? Not to me. I can turn the dizzy for free, and higher octane fuel is only marginally more expensive.

I'd probably still do it if I were building it myself, because I'm anal like that. But do I think it's really worth it performance wise? Nope. But that's just me. I guess it would be different if I needed a new exhaust too, vs. just doing it for the the "gain". And for my example that started all this, it's just one bend that's already bigger pipe than the stock one anyway, so I won't worry about it.

[Damkid]

I'm going mandrel bent, better flow plus easier to build my exhaust setup from just little elbows since I need to be very picky on my piping placement to fit everything lol