Exhaust thread

Sup Veeky Forums
So today I put a mandrel bent y-pipe on my car (VQ30), which removed the restrictive precats. I also installed a hi flow cat at the same time.

I already had a straight pipe catback before this install, but now my car has the same problem that every other straight piped vq has; an ungodly rasp at 3-4k rpm that makes a straight piped honda sound like a kazoo in comparison. It sounds amazing cruising around, but I cant get on it or let off the throttle above 4k or all hell breaks loose.

Because im running a side exit i dont have room under the car to fit a standard muffler. I can only go with a resonator, but I dont know what would work best here. What does Veeky Forums recommend?

Also post neat sounds

Other urls found in this thread:

en.m.wikipedia.org/wiki/Placebo
youtube.com/watch?v=o7QGW-77XfM
twitter.com/AnonBabble

"I fucked with my car and now it's worse"

go back to stock or buy a daily

>install a mod that nets significant, proven gains
>go back to stock
nigga no

>muh rasp
>V6
Well there's your problem......

But seriously if you want to smooth the cunt out a bit go buy the biggest glasspack hotdog you can fit under there - if you run a hotdog that's larger diameter than your pipe (e.g step up from 2inches to 3 inches then back down again) that will smooth it out even more provided you use some nice cones.

What effect would a baffled resonator have vs a glasspack?

>significant gains
>on an NA car

lmao got me

+12-20hp in the upper rev range is pretty significant user, especially when the engine only puts out 190hp stock

Depends on the style.
I ran a straight pipe into a stock tail muffler on a straight 6 and it made a choppy slappy rasp under acceleration.

Glasspack hotdog = smooth, even if you only run a small one with the same dia.

>12-20
>only in the upper range

i actually cant stop laughing and it gets better when I factor in what it probably cost too

Id like to see you explain to me how $300 for a 20hp gain is not significant and/or a waste of money

if you have space, i'd recommend a vibrant ultra quiet resonator. not a shill i swear.

They're a straight through design, not baffled type and theres a bunch of videos on youtube showing before and after.

pic related

You have a v6, that's why it sounds like shit.

My CTS-V came with a Billy Boat Exhaust cat back. X pipe. Better than stock. Not quite a Corsa.

It's a waste of money if you're going to come on here and bitch about how it sounds looking for ways to spend more money to fix what you just did

Can't have it both ways

Also you're full of shit with the +20 hp numbers but that's a separate issue.

It's probably the same logic that's stopping me from getting an MS3, headers, catback and high lift cams. The dollar to HP ratio of a turbo/super will always win, but you still need to sink in the initial bill to actually get it is where that logic falls flat.

The part where most busracers forget is that "+20" hp figure is usually in the upper mid/top end, but these mods can significantly alter the bottom end and torque, where it's most noticeable and why it's actually done. A catback may only free up 5hp on car X at peak power, but it could be up 15% from 1.5krpm to 5krpm and that's worth 40hp on the top end, if that makes sense.

>significant gains
>NA 6cyl
>no tuning

A free flowing exhaust should never drop your torque unless your ecu can't compensate and needs a tune.

Except that exhaust mods tend to lose low end torque which is what you need in a daily driver you fucking retard

>It's a waste of money if you're going to come on here and bitch about how it sounds looking for ways to spend more money to fix what you just did
No because the power doesnt magically disappear because I add a resonator. I can, in fact, have it both ways.
20hp is generous but again, gains are proven and not insignificant like with a random CAI. Double digit gains for any n/a mod is significant. There's a reason why its a go-to mod for people with this engine.
You're free to keep being a faggot though
Yeah turns out the vq30 gets starved for airflow in the upper rev range. An intake manifold upgrade and y-pipe are the the two most significant mods to make additional power even without a tune, granted you can make plenty more with a good tune.
dont tell me what i need faggot

Imagine being this much in denial. You didn't get much power for how much you spent. Make better choices next time.

Nigger who the fuck are you
If I want to drop 3-4 grand on a power mods ill just buy shitbox that already has a turbo
Instead ill drop a few hundred bucks on some new pipe for my current shitbox and enjoy my noticeable gains

Lol please go back to whatever circle jerk forum you came from

Maybe you'll stop being 17 one day and realize how dumb you were but if you're anything over then...well...good luck in life

>Noticable gains

en.m.wikipedia.org/wiki/Placebo

>3-4 grand on a power mods
>turbo car

Think you have it backwards there friendo :^)

>Instead ill drop a few hundred bucks on some new pipe for my current shitbox and enjoy my noticeable gains

Wow you sound really nonchalant there it's almost like you're trying to back pedal and play down how much of a retard you look like

>Oh no guys I really don't care about this car it's just a shitbox
>It's just a couple hundred why wouldn't I spend the money
>I'll get a new car that will be way better like a turbo like if I wanted to but I don't now

>DO IT MY WAY!!!!!

Wow you sound like a bit of an elitist faggot mate, some people like to do basic mods on their old shitboxes - deal with it.

i mean you're free to be upset. im happy with my gains so far. I just need to get the rasp under control.
what the fuck am i even reading
where is the back pedaling? where did i say i didnt care about my car? Is that fact that its only a few hundred dollars not a valid reason to make my car faster?
Is dropping 3-4k on a factory turbo car instead of turbo a car I already have not a smarter decision?
get your shit together

I cant stand people that throw a fuss like this over n/a mods. Shit drives me up a wall.

...

Why not remove your ac and ps too? It's free and improves power.

>i was only pretending
Its a daily driven car. Make no mistake, id have bought underdrive pulleys by now if anyone made them for my car. Maybe ill put my cad skills to use and draw some up

...

Stealing this thread for my own question. I have a 1993 Honda Accord, manual, 4door. What options do I have for exhaust stuff?

If I have this car for long, I plan on turboing it. But besides that, I wanted to go straights from about the middle to the rear. Mind you this is a 4cyl Accord. Am I gonna have to custom fabricate at that point? If so, what can I look at for welding tutorials?

If you have to custom fab anything for a honda you're probably doing some crazy shit
I would just avoid putting an exhaust on it altogether until you turbo it. Maybe just swap out the muffler for an aftermarket one.
Hondas almost always tend to sound extremely raspy when you put cheap systems on them
Turbos on the otherhand can be straight piped without issue, as the turbo acts as a muffler, thus cutting down the rasp.

This, if your muffler is flanged just get "sports" muffler, bolt it on and enjoy the drone.

Well I ask cause the muffler is dying of rust (but the rest of the car isn't. that I know of anyway) and right behind the muffler where the pipe connects to it, there is a small hole creating an exhaust leak right before the muffler, so it's not really dampening the sound too much anyway.

That's why I ask tbqh.

>Its a daily driven car
But a shitty straight pipe is okay

Ive dealt with that a few times. cheapest solution would just take a sawzall to it, buy cheap section of aluminized pipe from pep boys or something, shove the bitch on there and clamp it down. maybe add a little jb weld to seal it off.

how is it possible to be so mentally challenged and yet still have the capacity to use a keyboard?

I don't think it's particularly expensive to get an exhaust shop to chop it off and weld a new section + muffler in.

A common misconception is that reducing backpressure will result in power loss. What has caused this is in the old days, on carbureted engines, people would open up their exhaust with no other modifications and indeed often lose power. The reason was that the loss in back pressure leans out the mixture.

To benefit from the opened up exhaust it was necessary to rejet the carburetor. Since this was something beyond many folks, the belief that power would be lost was born.

On a Corvette,Camaro,Mustang etc any flow increase is automatically compensated for due to the increased flow through the Mass Air Flow sensor. The increased air flow is compensated for by the ECM resulting in MORE power.

Open exhaust produces MORE power IF the mixture is compensated for.

This, which is why AFM is the GOAT.
>tfw have only MAP sensor and TPS
>tfw freed up intake and exhaust only to lose power and risk leaning out my engine
Damnit Toyota.....

truly suffering

>have carb car
>remove exhaust and air filter
>can't figure out why it runs better with the choke on

To be young and stupid...

add 2 more cylinders

youtube.com/watch?v=o7QGW-77XfM

actually speed density accounts for this pretty well, however once you get down to the 0 point of atmosphere, it becomes inaccurate to such subtle details without tuning.

I'm not sure what you are saying but a MAP sensor measures the vacuum in the intake plenum. Less restrictions on the intake (air filer etc) = less vacuum = the computer thinks it's getting less air = puts in less fuel (when it's actually getting more air).

If you ask me MAP should always be accompanied by AFM.

I have no idea why that one guy is shittin on OP so hard
All he has to do now is mess with the ECU and he's fine

Literally the entire point of the thread was to ask about what would make a decent resonator
but niggers gonna nig, what are you gonna do

Did you put it on a dyno? The difference in sound alone is enough to throw off your butt dyno.

What do you mean "all hell breaks loose"?

Cell phone video of a Kline inconel turbo-back catless exhaust.

>I'm not sure what you are saying but a MAP sensor measures the vacuum in the intake plenum. Less restrictions on the intake (air filer etc) = less vacuum = the computer thinks it's getting less air = puts in less fuel (when it's actually getting more air).
that is some monumental misconception. time for school junior because you're dumb as fuck

That's literally how it works, prove me wrong.

The map sensor usually sits behind the throttle plates which are what control vacuum. Closed throttle plates means high vacuum open throttle plates mean less vacuum. Restrictions=/=normal engine vacuum

Since this is the exhaust thread I guess I'll ask here.

What's the best setup to get a good bassy rumble out of an sbc without it being retard levels of loud? Completely rebuilding the engine in my truck. Was gonna go with a nice set of longtube headers, but beyond that I'm stumped. Catalytic converter not needed, but nice in case I move or something.

Yes a MAP sensor works together with a TPS.
But that doesn't change the fact that less vacuum (at a given throttle and RPM) = less fuel.

your actually thinking of it backwards, the closer you get down to 0 vacuum the more fuel the computer injects. Its called speed/density and it works just how it sounds.

it measures the speed of the air going into the intake (tps sensor) and the density of said air(vacuum/pressure sensor "MAP") and then calculates how much fuel to inject.

From what your saying, the more vacuum an engine creates the more fuel it should inject to compensate. However your thinking of it wrong, the lower the amount of restriction the throttle body is creating, the more fuel needs injected due to the larger amount of air that is going through the intake.

Again what im saying is that speed density is a calculating type of measurement system, where as MAF or mass air flow systems actually measure the physical amount of air going into the intake, and then calculate how much fuel to add to a known true number of air.

You're disregarding two very important points:
(1)
Vacuum is created not just by restrictions but also by airspeed, the higher your air speed the higher your vacuum - this is the main function of the MAP sensor.

(2)
>it measures the speed of the air going into the intake (tps sensor)
All the TPS does is measure the amount of throttle you are using so that the computer can accommodate for:
>the lower the amount of restriction the throttle body is creating

however this isnt true, opening the throttle body up does not induce a vacuum, it reports atmospheric pressure (or 14.7 on the absolute scale). and thus is the problem with full throttle situations with speed density is that the difference between 0.01 in/hg and .05 are so minute that changes may not be made at all due to the formatting for VE cells, even if they are interpolated.

Also TPS is mainly used for fast acceleration, like an accelerator pump. fast movements of the throttle could lead to lean spikes unless compensated for by multiplying the VE*xx variable according to the tps differential over time. Its also used for decel cuttoff and leanburn calculations.

Literally all that a speed density engine needs to run is a map sensor, in your theoretical world if a map sensor read higher vacuum when the engine was moving towards wide open throttle, then turbocharged engines would lean out and die as soon as the turbo supplied positive pressure.

>thus is the problem with full throttle situations with speed density is that the difference between 0.01 in/hg and .05 are so minute that changes may not be made at all due to the formatting for VE cells, even if they are interpolated.
I don't think that's too much of a problem. 1 or 2 kPa doesn't make a huge difference. Or at least it doesn't make as much of a difference as the affect of changing intake or exhaust components has on the engines volumetric efficiency.
The feedback from an o2 sensor can help to correct errors. I believe some items run o2 correction full time on NA applications.

Anyway, I can not believe the ignorance of some of the guys in this thread. It's not like any of this stuff is kept secret. You can't just make up an engine control strategy.

>what is air speed
You still don't get it.

i agree the o2 sensors would make up the difference in the long term/short term trims, however its good for people to know how/why fuel injection strategies account for the infinite amount of variables that could take place on an intake/exhaust system.

air speed does not represent vacuum unless you have a clogged air filter, even then it would represent a clogged air filter, not the speed of the air.

>opening the throttle body up does not induce a vacuum, it reports atmospheric pressure (or 14.7

No naturally aspirated engine has ever in the history of the world filled up an entire combustion chamber with 14.7 psi.

>air speed does not represent vacuum

>how does a carburettor work
>how does vacuum advance work
>how does a fucking spray painting gun work

Shutup idiot.

At this point you have to be trolling. Or at least trying to troll.
The speed part of the control strategy is engine speed, not air speed. The map sensor is positioned to read a static pressures, not a stagnation pressure.

Air speed creates vacuum, get that through your thick skull already.

Yes they have. Some can achieve pressures above atmospheric.
Go and read about finite amplitude wave tuning of intakes and exhausts.

That's not disputed. Im aware of the changes in potential and kinetic energy of a gas in response to changes in velocity.
But this is not how a speed density control algorithm calculates mass air flow.

It has been disputed several times in this thread.

How then does a pressure sensor measure air flow?

this is just wrong in the way the engine strategy sees it, if the map sensor was put on an intake runner then i would agree, it would see vacuum.

However that is why the map sensor measures the vacuum/pressure of the plenum, not the runner.
This is wrong. many drag engines have produced positive pressure in the chamber by taking advantage of port and cam design with the intertia of air.

>if the map sensor was put on an intake runner then i would agree

Like on a 20v 4AGE?

Depends on how the air flow is determined.
The MAP sensor in a speed density setup does not measure airflow. It measures pressure.

The intake pressure and engine speed are the x&y axis of a 3d look up table used by the ecu. the z axis of that table being volumetric efficiency.
The mass air flow is then calculated using the engine speed, volumetric efficiency, and air density (which is calculated from air pressure and temperature).
This method relies on good modeling of the 've table for correct air flow determination.

>20hp is generous but again, gains are proven

>The mass air flow is then calculated from air pressure (or lack there of)

AKA vacuum!
Now apologize.

I dont know how the 4age actually calculates the fuel injection map, it should be alpha/n and not speed density strictly.

Air pressure in the intake manifold is not a function of airspeed.

I'm telling you it measures vacuum.

There are two causes of vacuum in the intake manifold:
>Air speed
(this depends on the location of the vacuum tube)
>the engine sucking in air
more so when there is a restriction at the other end (like say an air filter)

Both these are functions of how much air the engine is sucking in.

then tell me why does alpha/n exist if vacuum tells you how much air is entering the combustion chamber.

I don't know what the fuck you're talking about.

I think you're out of your depth here. And this is Veeky Forums!

how do i cut out my middle resonator and replace it with a straight section of pipe? i dont know how to weld

>oh yeah well then how do you explain "X" (not the thing we were talking about)
>You're just out of your depth bro!

That's a red herring argument if ever I've seen one. And the man who didn't realize air speed creates vacuum is telling me I'm out of my depth......

alpha/n was created just for this problem that you posted a picture of, ITB's.

alpha/n takes both TPS input and map input to create a composite load which then can be correlated to a fuel map. Usually this is used on engines with ITB's because of the issues with using a map sensor without a plenum as the vacuum drops off dramatically just off idle yet engine load has not been increased.

So a generic alpha/n map would look like this: >20% TPS range use MAP input for idle and tip in.

Also to alleviate this issue, like your posted picture they have created a "plenum" in which air is stored in order to be able to read the actual vacuum of all four combined cylinders, instead of a single cylinder which in between pulses loses vacuum almost completely at low rpm's.

No. Air velocity is a function of pressure differential. You can have low pressure without any air velocity (in a vacuum chamber for example).