Measuring stock exhaust restriction

[Multiades]

Originally Posted by bluemax_1

Kewl. Were those airflow differences measured vs stock ATR dual or single shot? And aside from weight, do you know of any airflow differences between the ATR dual and single? I got mine from DR when it went on sale about 2-3 years ago and I figured at the time, if Matt could hit 10's with it, should be enough for me. Don't think anyone else really had something that was proven to be better back then (that I was aware of anyway) aside from maybe the crazy 4"(or was it 4.5") JIC (Pitroad?) full titanium that cost and arm, a leg and left nut. Super light and big enough for a cat to crawl into but uh... money better spent elsewhere.

So you guys just got a shop with a mandrel bender to put the 30 degree bend in a pipe and tacked on any muffler you liked? Interested to see where the bend is. There's not a whole lot of room to route the pipe under there.

I don't know the exact data. The figure above is what my friend quoted to me after testing it himself (I wasn't there).

This exhaust formula isn't exactly revolutionary. Any of the big Supra exhausts have one bend near the back, then leave the muffler to exit at an angle. The bend goes at the back under the rear suspension. You may have to bend slightly off the downpipe if you're running an ATR and don't want to reconfigure the downpipe to shoot straight back.

This isn't just a mandrel bend, either. It's straight tube rolled so that it has a center line radius that a mandrel bender can't do. It's not the most critical part, but there are lower losses through a larger radius bend. This exhaust plan takes that to the extreme.

-Chris

[RobBeck]

I would like to see similar data that FWombat produced here for this comparison. I too have the ATR single shot, and althout it has a couple of bends... I would really doubt it would cause any significant backpressure. The design is really good IMO, and fits well. The cost however is fairly high.

Rob

Originally Posted by Multiades

Not that the ATR isn't nice, but as I just mentioned, it doesn't compare favorably to the minimalist one-bend exhaust my friend has been producing.
-Chris

[Multiades]

Originally Posted by RobBeck

I would like to see similar data that FWombat produced here for this comparison. I too have the ATR single shot, and althout it has a couple of bends... I would really doubt it would cause any significant backpressure. The design is really good IMO, and fits well. The cost however is fairly high.

It's too late for the comparison I think. The ATR is off and in pieces.

Even so, the ATR single shot has two 90-degree bends and that 45-45 kink in the middle. Those are probably 1.5d-2d bends, so I bet the losses at high flow are significant.

[RobBeck]

"High Flow" is too vague for me to call that bet.

Rob

Originally Posted by Multiades

so I bet the losses at high flow are significant.

[Multiades]

Originally Posted by RobBeck

"High Flow" is too vague for me to call that bet.

You're right, but to simplify matters which configuration would you rather have at maximum exhaust gas flow?

[RobBeck]

I would have to 1)see them both installed, 2)compare the costs, 3)compare materials, 4)hear them (preference and muffler pending), and 5)get backpressure data to make an educated decision on that. But 1-4 would probably suffice for the most part. I agree with what you are saying, I just think the flow would have to be pretty substantial to see a remarkable difference.... such that 3" would probably be undersized to begin with.

I would be more concerned with the stock (or even DN precats) before the ATR single shot catback... flow-wise.

Rob

Originally Posted by Multiades

You're right, but to simplify matters which configuration would you rather have at maximum exhaust gas flow?

[Multiades]

Originally Posted by RobBeck

I would have to 1)see them both installed, 2)compare the costs, 3)compare materials, 4)hear them (preference and muffler pending), and 5)get backpressure data to make an educated decision on that. But 1-4 would probably suffice for the most part. I agree with what you are saying, I just think the flow would have to be pretty substantial to see a remarkable difference.... such that 3" would probably be undersized to begin with.

3" is a bit undersized for the kind of power anybody with TD05s is after.

[AdamVR4]

This is why I don't run an exhaust, period. I want a 4" downpipe...

[bnorris85]

Wow good info. I have a single shot exhaust..but then again i have all my cats. Cant bring myself to gutting them, i love the way my exahust sounds too much lol

[J-Ville VR-4]

Wow, really interesting info I'd like to see how much pressure builds up in the headers on a stock turbo/exhaust car at 15 psi