Here’s the deal. 2.5" duals are hanging on the Miata right now, and are equal length, about 4’ long each, dumping out underneath the driveshaft. I don’t feel like running them to the rear because it’s a horribly tight fit.
Now, ground clearance is almost non-existant in this thing. I might, might be able to weld in a flattened h-pipe, but is it really needed? The piping is equal length, and a bit short (4’.) I understand the extra balance helps the scavenging effect, but I really haven’t seen any proven dyno results. Everyone on LS1Tech just says “crossovers make more power” but no one ever backs up that claim.
I saw several posts on there from guys just running seperate tubes with mufflers, dumped out, and no complaints. I think this is the route I’m going to go unless someone can show me a significant power increase. Probably getting the Moroso SpiralFlows, by the way. Moroso claims 5-7dB drop over open headers, and they’re only 4" diameter, so I should be able to squeeze them in there.
The crossover will equalize the exhaust pulses, that’s reall all. X’s flow better at higher RPMs, H’s flow better at lower RPMs. I’d rather have a crossover than not on duals.
Exactly! No one ever answers past “you should have one.” Not pointing fingers at anyone, I’m just saying. That’s something else I got, was the exhaust note. However, I don’t think my car sounds bad at all. It has the loud pop/rasp downrevving, but I think it sounds great.
I said f-it, though. I’m building straight pipes. They’re done, actually, but I ran out of paint and don’t have a vehicle to go get more right now
5-7dB is a decent bit for a free-flowing muffler. The bullet/straight-thru mufflers don’t do much, and the big (read: I can’t fit them) mufflers quiet it down and make less power.
I’ll tell ya what. Going from essentially 2.5" open headers, to a 1’ long piece (a 90* off of the header) changed the tone a lot. I’m guessing just the extra volume is going to quiet it down a good bit compared to what it was. I’ll grab some video whenever I fire it.
I was going to do side pipes, but after looking at it again and again and again, it’s not worth it. I have to relocate my fuel filter, and everything is such a tight fit, that it’s not worth the hassle.
So, dumps with the OEM muffler hanging in the rear FTW.
EDIT: I’m aware of what the crossovers do, I’m looking to see if there’s proof of significant power loss/gain.
There was an H vs. X dyno comparison on MustangExhaust.com before they re-formatted it. Now everything is gone.
The gain is minimal though. The different shapes of the crossover just change the tone and where the power it does add goes. I doubt you’d be able to tell the difference in the seat of your pants.
Im not familiar with the floor plan on the Miatas, but what about a Y into a 3" exhaust that routes out the back? Im sure there are 3" exhausts for that car that people make for turbo applications(by this I mean in theory a 3" should work), maybe Jeff or Domination can give you some heads up building one from scratch. Im sure it would quiet it down a bit and you would still have a muffler in the rear thats not there to keep you from gettingpulled over
I’ll get some pics, but it’s very, very tight. I’d have to run under/around the rear diff, and it’s going to scrape like a motherfucker if I do that.
The original plan was to use the 3.5" from the DSM, and after I got the car together, there was no way it was fitting.
As for the look of a “finished” exhaust, I’ll say this. If I get pulled over, it’s going to be because the cop heard the car, not because he saw the muffler
Thanks for the link redneck, but I was trying to find a no crossover vs crossover dyno. The popular consensus is to run a crossover, but no one can tell me what power loss, if any, is had from not using a crossover of any kind.
The exhaust is done though. I’m waiting for the high-temp paint to dry, and I’ll grab some pics of everything.
For any performance exhaust system, some type of crossover connecting the two sides of a dual exhaust system is important because it acts to balance the two banks of the engine. The common H-style crossover is good at balancing sound pulses between the two halves, but does little to promote scavenging because the exhaust gases tend to follow the path of least resistance, which is straight through each pipe rather than taking the 90-degree turn through the H-pipe into the other half of the system. In an X-pipe system, however, where the two sides of the system intersect, the gasses have no choice but to intermingle as they pass through the junction. This promotes improved scavenging effects by smoothing out uneven exhaust pulses from the engine’s firing order. It also helps quiet down the exhaust, resulting in a mellower, less raspy tone. The faster acceleration of the gasses through an X-pipe causes them to flow in a linear fashion parallel to the walls of the tubing rather than tumbling. This “laminar” flowing gas is much quieter than tumbling gas, resulting in an exhaust tone up to 8 decibels quieter than a traditional H-pipe
LMAO thanks, but I know what the differences, pros, and cons are. I’ve spent some time searching LS1Tech, and have gotten every answer except this one.
i can mention that when we had open header on the corvette. there was kooks long tubes with 3 inch duals with an x-pipe no mufflers. the car was not that bad. it was loud at wide open throttle but was too loud for normal cruising. my opnly guess is that the x pipe Helped muffle the car.
sorry JesseW - I thought it was an x vs h discussion.
I have no crossover on my truck. Off each header is a 2 ft pipe then an 18" glasspack and a dump right after the cab under the truck. I don’t have any dyno data, but it sure made a difference in sound and power when I got rid on the single exhaust that was on there.
It’s just crazy how unproven information spreads like wildfire. I’m not claiming that a crossover makes more/less power, by the way. That’s why I’m asking if anyone has ever seen some proof. I’m just curious.
