by "AestheticsInMotion" (aestheticsinmotion)
Published 01/29/2017 at 22:07
by "AestheticsInMotion" (aestheticsinmotion)
Published 01/29/2017 at 22:07
Tags: Zoomzoom
; Miata
; Mazda
STARS: 3
That said, I have a few questions and concerns and was hoping a more experienced person could give me some advice.
Short recap, my exhaust sheared off cleanly right before the cat six months ago. I just noticed last week when trying to remove it and I ended up getting the studs in the cat out and pulling the chopped midpipe even further from the cat so it became EVEN LOUDER. I didn’t remove it because I needed to find hardware to mount the new one.
Done!!! Replaced the studs with stainless bolts and lock nuts and swapped exhausts. Felt good throwing that disgusting piece of rust away. Pictures and sound clips on the car later this week.
Onto the concerns/questions...
First off, it’s a good thing I put extra insulation under the carpeting a few months ago (floor underlay for laminated wood) otherwise even with the top down I think the exhaust gasses coming into the cabin would have KO’d me, driving the past few days. It’s nice not having to worry about that anymore. BUT, I’ve gotten so used to my exhaust terminating at the cat that the new setup sounds soooooo quiet. I’ve already decided on replacing the cat (there’s something rattling around inside) but I’m not sure with what. I can go with a stock cat (not happening), a high flow cat or a test pipe. I’m hoping to get the loudness between what it was with the sheared off exhaust I’ve had for six months, and what it is now. So... Test pipe or highflow? How big of a difference would this make? Pros and cons?
Two, I feel like the car got faster. Seems like throttle response is quicker. Is this possible? With the exhaust exiting at the cat I would assume putting a midpipe and muffler on would restrict the flow, and make it feel a little bit slower (if there was any noticeable difference). Am I just crazy?
Three. Well... My passenger door won’t open. I jacked up the back all the way, one side at a time and put the stands in the proper places. I’m worried I bent the frame just enough to keep the door from opening..... It’s possible the door latch just broke (it feels a little funny) so I’m not too worried yet, but.... I don’t know. Bent frame would be bad.
"bob and john" (bobandjohn)
01/29/2017 at 22:12, STARS: 1
if the car bent just from being jacked up and thats whats not letting the door open, then it is NOT safe to be on the road, period.
as for the feels faster, motors need SOME back pressure to function correctly. there is a noticeable torque dip on my SV when I took the can off VS when I have the can on.
"AestheticsInMotion" (aestheticsinmotion)
01/29/2017 at 22:18, STARS: 0
I’m going to have it checked out a body shop if it isn’t just a bad door latch that picked the worst time to fail. I really don’t know enough to say what shape the frame is in.
Huh... That’s probably it then.
"for Michigan" (formichigan)
01/29/2017 at 22:22, STARS: 4
Do you know how much the new exhaust weighs compared to the old one? You probably didn’t drop more than 1% of the weight, but I don’t know.
My vote is always for catted over uncatted. Cats serve an important purpose. None of us really want to be breathing all that extra crap just so a car can be a little louder.
"AestheticsInMotion" (aestheticsinmotion)
01/29/2017 at 22:27, STARS: 1
Went from 32ish pounds to about 15 if I remember correctly.
Good point. Highflow cat is looking like the best choice
"TheD0k_2many toys 2little time" (thed0ck)
01/29/2017 at 22:36, STARS: 3
no they dont. they need exhaust velocity. backpressure is a myth from forum bros.
"TheD0k_2many toys 2little time" (thed0ck)
01/29/2017 at 22:37, STARS: 0
i run a stock size straight pipe from the factory headers to a vibrant straight thru muffler. Sounds great IMO
"for Michigan" (formichigan)
01/29/2017 at 22:41, STARS: 0
IDK what year your car is, but assuming it’s a 1.6 NA with no options, you just went from 2150 lbs to 2133 lbs and we’ll assume power is a steady 115 hp. In that case, you just went from 18.7 lb / hp to 18.5 lb / hp. I doubt that’s a noticeable difference.
Although, if there were a 5 hp difference between the broken stock exhaust and the Fujitsubo exhaust, that would be a 1 lb / hp difference, which would probably be noticeable.
That’s really all just speculation on my part, though.
"AestheticsInMotion" (aestheticsinmotion)
01/30/2017 at 02:26, STARS: 2
This is just as embarrassing as it is relieving, but the reason my door wouldn’t open? It was locked......
Haven’t locked the doors in over a year, so it’s not something I really even notice anymore haha
"bob and john" (bobandjohn)
01/30/2017 at 09:32, STARS: 0
LMAO. okay, thats just funny
"ateamfan42" (ateamfan42)
01/30/2017 at 11:35, STARS: 0
as for the feels faster, motors need SOME back pressure to function
correctly. there is a noticeable torque dip on my SV when I took the can
off VS when I have the can on.
As was already stated, back pressure being good is a long standing myth.
What is desirable is a high exhaust velocity, to aid in cylinder scavenging. A big diameter, low restriction exhaust will promote better flow at high rpms, but will have slow exhaust speed with flow volume is low (at low rpms), leading to torque loss. A smaller exhaust will promote higher gas speeds at lower revs, but can be too restrictive when the flow volume is high at higher engine speeds.
The trick to exhaust tuning is striking the right balance to have high enough speed at low rpm without adding too much restriction at high rpm.