Niku-Sama

ok so i was wondering, would not having a middle muffler/cat cause popping exhaust when you decelerate?

snwbrderphat540

thats always there, not having those just makes it more appearant

teenbmxer

yes its possible and the larger the pipe ad less back pressure the more apparent and the louder it will be.

teenbmxer

and thats why i think stock hondas with 3" exhaust sound like fart cans because the have to much exhaust with no need this loss of back pressure will cause a loss in torque which the already have a lack of. haha

Niku-Sama

i was just wondering if it helped because todays the first day i drove the car with the windows down and its kinda poppy, not backfiring though, and the middle/cat is gone.

glasspack yay or ney on the helping?
i'm not going glasspack alone

snwbrderphat540

you should get a real exhaust made up. 2.5 inch with your choice of muffler. and if you need to pass emmiions some type of CAT

260zturbo

^^^^ do what he said but get mandrel bent be careful bc alot of shops do crush.

snwbrderphat540

i was lucky enough that a local TUFFY beleive it or not had a mandrel bender and an amazing welder they borrow from the city. he's a bit pompous but did good work. and it only cost me 150 bucks for teh exhaust to be made and 20 for the muffler a shop special.... basically, i made out like a fiend!!! i just wish it was a more oval muffler and less canister style.

teenbmxer

ya deff. go with 2.5 mandrel bent at the largest, unless u have a turbo car cause then in that case u dont really need back pressure.. no matter what try to get madrel bends. what i did was got a performance cat the is flow through and the catalist is on the outer edge of the inside of the cat. but if you go to big you will lose to much back pressure and by doing tht you will lose some torque

Niku-Sama

2.5 is decent with turbo, or atleast any ammount of turboing i may do in the future, its already 2.5, the previous owner did open up the exhaust and lickily its over 20 years old so i dont have to pass emmissions.

i was thinkin of getting a decent muffler, like a tanabe medallion G ("93db" performance muffler) but something to get the old chogy poppy sound out and have a nice humm

FubarI33t

At least you don't backfire with mean flames like I do

snwbrderphat540

ive backfired with a flame about 2 times now... on my turbo car though. lol.

teenbmxer

haha, unburnt fuel......i had that happen

hoov100

i hate my current exhaust and i lose alot of low end, its 3.5 inch o2 elbow back and it sounds like ***.

Z33Driver

Oh, the dreaded backpressure myth. I don't think this myth will ever die. My fellow Z friends lend me your…eyes as I try to show you the light.

First off, backpressure is bad and every measure should be taken to reduce it. I think that you are confusing backpressure with exhaust velocity. The goal of a performance exhaust system is to achieve the highest possible exhaust velocity and reducing as much backpressure as possible. I have posted some links that go into more detail. Enjoy.

Destroying a myth
Backpressure: The Myth and Why It’s Wrong
The Mighty Backpressure Myth

snwbrderphat540

and now my friend you are misslead. you realize every engine needs backpressure? even F1 cars need specific amount of back pressure to oporate properly. to little you DO loose low end torque and if it is lost enough you will blow piston rings. back pressur robs mid-high end power but you still DO need it. this was already THUROUGHLY discussed on this forum about a year and a half ago in the Z32 section. maybe ill post the link if i get around to searching for it. but what your saying is that you want to eliminate all back pressur, so just run open headers over sized right? why run any sort of manifold at all, why not just an open head?

Z33Driver

Snwbrderphat540 did you read through any of the links?

snwbrderphat540

well, none of them do good explanations, the first one is vague and covers nothing but saying a lean mixture burns valves, its crap. the next two are honda forums so i just automatically skipped them. im finding mine.

hoov100

theres a reason running open heads will kill power, but please lets not go into header designs and header tuning.

Z33Driver

Just because they were on Honda forums doesn't mean they are worthless. You should at least read them before dismissing the information.

I understand why you say, "to little you DO loose low end torque". For example, you install a 3 inch exhaust on an N/A car, have a dyno done before and after and notice that you lost some low end power. You know that bigger piping will reduce backpressure, so you make the conclusion that reduced backpressure will decrease low end power. (reasonable argument)

But that's not the whole story. If you re-examine that dyno you will notice that although your low end power suffered you will have more power up top. The reason for this is exhaust velocity. The larger piping will allow a higher exhaust velocity in the upper RMPs leading to more peak power. However, the larger piping is too large to maintain exhaust velocity in the lower RPMs. This is why smaller piping provides more power in the lower RPMs.

Backpressure defined from Dictionary.com
Backpressure:A resistant pressure exerted by liquid or gas against the forward motion or flow of an exhaust or pipe system. Residual pressure opposing the free flow of a gas or liquid, as in a pipe or an exhaust system.

snwbrderphat540

i mixed facts with other facts to create new "facts" from the thread i was thinking of. sorry.... but in essence i was right, in how i delivered it, i was wrong.

https://www.zdriver.com/forums/showt...t=backpressure


also, i have a problem with this velocity term, because velocity will yield a back pressure reading the faster it is because that shows it has the pressure behind it to create it. and yet they complain about not having velocity. and that last thread is to ****ing long. im not reading that crap

Z33Driver

Just to clarify things, are you saying backpressure is good or bad?

I think you're misinterpreting backpressure. Backpressure is resistence to flow. It doesn't help flow.

Sorry, I didn't mean for you read the entire thread. I just meant to read the main post which gave the explanation.

Z33Driver

Here's another explanation of backpressure from a different thread on this forum

hoov100

"maximum mid-to-high RPM power will be achieved with the lowest possible backpressure. Period!"

now i dont know about you, but i like my power down low. considering that most z motors make peak power at 6kRPM


but also look at a bikes exhaust system, they have a flapper that controls back pressure, what does that tell you?

Z33Driver

The flapper that you are referring to is an attempt to maintain the highest amount of exhaust velocity as possible, not to increase backpressure. Making an exhaust is difficult because you usually have to sacrifice low end power or top end power. Using a flapper or some kind of vavle can help to achieve both low and high end power. The goal is exhaust velocity, not backpressure.