When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I think that's correct. Spintech to Magnaflow and picked up like 40HP...
Cutout to Magnaflow was like 2-5HP.
That sounds correct Jake. I can't remember how much power he was making. N/A, boost, etc.
I'm going to do some searching later and see if I can find the the thread. I'm actually surprised we don't see more people running a 4inch setup. IMO, it's only been recent, realitivly speaking, that dual 3 inch has become more common. Back in the day you either had to cobble together some jank *** dual 3 inch system from crush bends you bought at AutoZone or drop big money on a custom exhaust.
I've thought about doing a 4" several times. The ground clearance issue isn't much worse than dual 3" but the idea of running a crossflow muffler that's actually quiet with a 4" cutout is a good compromise for a good decent HP system...
A 2.75” (stock) single system is good for a 310hp engine with zero loss… A 3” Single system is good for a 370hp engine with zero loss… A 3.5” Single system is good for a 503hp engine with zero loss… A 4” Single system is good for a 657hp engine with zero loss… A 2.25” dual system is good for a 457hp engine with zero loss… A 2.5” dual system is good for a 513hp engine with zero loss… A 3” dual system is good for a 812hp engine with zero loss…
I bought a bunch stainless rods, and hardware my brother and I are going to fab up some extra hangers to hopefully solve SE's low hanging after the x pipe, If its still not up to par afterwards ill be selling and putting the new headers and Y pipe on with a 4" system on it.
That's a ridiculous amount of gain going from dual 2.5 to dual 3.0.
Based on David Vizard's calculations when he used to publish those articles in Hot Rod all the time.
Based on zero loss... so that's the calculation for an exhaust with no restrictions, mufflers that flow like an open pipe, etc. for how much power they support before they start to rob an engine of power. And dual 3" is overkill for a lot of guys. But cammed LS cars really need a dual 2.5" or single 3.5" setup to show no loss. And for most heads/cam and even 400+ cid motors, 4" is plenty. Once you get to 700HP though, dual 3" is the way to go. (That's for NA cars or Supercharged motors).
That's a ridiculous amount of gain going from dual 2.5 to dual 3.0.
Figure the circle area differences alone, besides the internal surface areas being swept by flow. It will amaze you.
This also shows the OEMs are on the right track with single 3" and 3.5" exhausts on many of today's trucks.
My stock 04 5.3 (about 290HP)Tahoe has a 2.75" pipe to the muffler with a 3" tailpipe. A full 3" catback will be going in. As long as the muffler is good, that will be plenty big for the 5.3.
I've thought about doing a 4" several times. The ground clearance issue isn't much worse than dual 3" but the idea of running a crossflow muffler that's actually quiet with a 4" cutout is a good compromise for a good decent HP system...
A 2.75” (stock) single system is good for a 310hp engine with zero loss… A 3” Single system is good for a 370hp engine with zero loss… A 3.5” Single system is good for a 503hp engine with zero loss… A 4” Single system is good for a 657hp engine with zero loss… A 2.25” dual system is good for a 457hp engine with zero loss… A 2.5” dual system is good for a 513hp engine with zero loss… A 3” dual system is good for a 812hp engine with zero loss…
Originally Posted by LilJayV10
That's a ridiculous amount of gain going from dual 2.5 to dual 3.0.
It's also not totally accurate in the real world. Made 1100+hp on a single 4", 800+hp though a single 3", also made north of 700 on dual 2.5". Perhaps "zero loss" can be skewed a bit, the percentage of loss as HP goes up is more important to me.
It's kinda like the stock muffler debate, people swore they were restrictive because they were quiet and necked down considerably inside. So a few people on the dyno tried it and stock mufflers basically are only worth 5-7hp vs an open pipe or something much louder.
Those are for NA motors. Turbos are a different ballgame.
4" single downpipe is good for 1000HP usually before you need to get into a 5" to really show big gains. But that's because we are looking at turbo efficiency, backpressure, and turbine housing as bigger indicators.
But for an NA motor... the exhaust port, header size/design/collector size has a lot more of a say than the exhaust. But the idea is the right sized pipe will allow for no loss... so if you went with cutouts, you'd gain essentially nothing. When guys put cutouts and pick up 40+HP that means their exhaust isn't really optimal for what they are trying to do.
I've been running a Mufflex 4" system with a Magnaflow straight in/out muffler forever.... and plan on it keeping it with my new N/A 434. Last combo made 565 to the wheels all motor, new one should be near 700. If it were easy and acccesible I would bolt up dual 3.5"s just to see how much it would pick up.
I did my own on my third gen. Dynatech muffler. I wanted dual outlets so I had to get creative. I had a 3 inch with a Spintech crossflow before and it feels like it picked up all of 50 hp with this setup.
I remember a loooooong time ago on LStech. There was a guy with a black Camaro, SS I think. Who had a Mufflex system on his car and either had a Flowmaster or a Spintech muff(chambered) and switched to a Dynomax or Magnaflow straight 4 inch muff and picked up a stupid amount of power.
Yeah I know there is a lot of ambiguity in that statement but that's the best I can remember from drinking for the past 15 years.
I would go back and search for it but I'm afraid I might get my dick smacked if I post in a thread that old.
Similar experience here although not as drastic. Had a dual 3" to single 4" setup on my M3, and had a removable rear section with a 4" Flowmaster 1 chamber for events that required passing sound. Cam only LS1 made 398rwhp with muffer on, 409rwhp no muffler. Went to an LS3 and it made 486rwhp with muffler, 504rwhp no muffler. We tuned with no muffler then just bolted the rear section on to see what it lost, so could've left a few hp on the table with tuning.
Another friends RX7, cam only LS3 made 476 on same dyno, 3" straight through single muffler (unknown brand), actually lost 1hp but gained a bit of torque dropping the muffler, so within noise, which was pretty surprising considering the 3" single exhaust. Wish we could figure out what muffler it was, was very light too, and quieted it down significantly.
We may test dual 3" versus 4" single on my new combo, I actually prefer the way the single sounds and it is lighter and a bit easier to package as well.
Update: End Result got the SE true duals tucked up in my opinion really high, used their seat belt bolt hanger, and made a couple of my own to aid it as well. Car is staying with dual 3" for now. Ill take some pics next time i go home. Have sound clip just can't upload here for some reason.
11-14-2019, 06:54 PM
