is it bad to take off my muffler, and just run nothing, cept a foot long piece of pipe?

 

Back pressure is something you have to watch out for. On my ranger (5speed) I run 2 feet of pipe. But there is a Cat on that 2 feet. Ford got smart and put the cat before the bolt off. But that cat gives me the proper back pressure to not mess up my 4 banger under the hood. So it all work's out nice. But I don't know about your Z.
My ranger sounds like a very loud Pissed Off WeedEater (not bumple Bee) but sounds sweet. Low rpm's very very deep, high rpm sounds like fast and furios, but louder.

 

Ranger = not a Z...


You can straight pipe your Z if ya want (won't be legal tho). Just need an O2 sensor. Some engines need a lil back pressure to run right (ex: turbocharged cars need a lil backpressure to spool the exhaust turbine) but you deffinately don't want too much back pressure. There is a basic rule of thumb for exhaust size to hp ratio... I can't remember exactly, but it's something like:

1.5" up to 125 hp
2.0" 125 - 200 hp
2.5" 200 - 300 hp
3.0" 300hp+

 

well there is a cat on my exaust, it is located next to the tranny, sort of. then it just runs through to the back into my muffler, well the pipe comin from the cat is 2 inch, and i have a piece of pipe a foot long that goes on the end of where the muffler usualyl goes, and it makes low rpm deep throaty, and then higher pitched high rpms, my friend jeremy and i are going to take off my cat, make it straight through, so its as if theres nothing there. is that ok? i mean is it gana blow my engine up, can i do this for the last month im a civilian?

 

you can't get a foot up pipe from autozone and bolt on there? won't cost much, and take very lil time

 

I haven't heard of anyone "blowing up" their car because they took out the cat. Ya gotta understand how cars work.

 

im soo lost, i dont understand. im gana hollow out my cat, to make it more freeflowing, now i want to take off my muffler, cuz its stock muffler, and put on the end of the exaust pipe where it usually connectos to the muffler, a foot long piece of 2 inch pipe. is that gana hurt anyhing is wat im asking, i have it down to a science, when im not home i take off my muffler, takes me about a minute. literally, then slap on the pipe and run it like that, then b4 i go home i take off the pipe and it takes me 2 mins to put the muffler back on. its because my parents wont leme do any upgrades to my car cuz i havnt payed it off yet.

 

What is it that you don't understand??????

look: check out this link & read about how cats work:

http://auto.howstuffworks.com/catalytic-converter1.htm

 

Now Nismo, be nice. He's just a kid.

You can run open headers without 'blowing up' the motor. Almost nothing you do after the combustion chamber will physically damage the motor.

It may have less power, but it won't break anything.

I wouldn't pull off your muffler and I wouldn't hollow-out your cat.

Enjoy the car the way it is until you learn a little more about it and how motors make power in general and then specifically how to make them run better.

Read a little before you start modifying it and actually LOOSE horse power.

Most modifications that don't require an understanding of the whole system don't make any or very little improvment in the cars performance.

Modifications that do require an understanding of the system done half assed, will REDUCE your horse power.

Cheers!

 

i have headers and wanted to run a straight 2.5" pipe do you think id lose hp

 

stock engine with wide open exhaust? gonna gain 5hp and loose 15 ft lbs of torque.

 

sorry Thermal... hopefully no offense taken.

When I have tech questions... I like to look for pics of what other people have done. Google Images & MSN Images work pretty good as search engines for tech pics. Isn't the web bloody cool???

 

nah no offense taken but i dont have a clue wat the *** im talkin about soo gata bare with me.

 

i have an intake and an accel ignition isnt much but would that help cause i dont want to lose that torque

 

Bleach of course hit the nail right on the head. You need the back pressure to help with torque in an NA engine.

In a turbo, you want as free flowing as possible. Custom mandrel header w/ 1" runners and a 3" down pipe to a 3.5" straight exhaust and that turbo will be your friend forever.

 

Not entirely accurate. Backpressure actually does the opposite for spool up. Backpressure slows exhaust flow thus slowing the flow through the turbine. With a turbo you want as little AS POSSIBLE. None would be preferable. The whole point in backpressure is in the way it affects the exhaust exiting the cylinders. When you stick a turbine in the exhaust stream everything downstream of that turbine does nothing to the exhaust flow exiting the cylinders. The turbine is the backpressure, anything after that is the enemy. Even a little.

As far as removing the muffler goes, there is absolutely no point on a naturally aspirated street vehicle. Replacing the stocker might be rewarding, but running no muffler is senseless (unless funds are a restriction or weight is a concern) when you can just buy a freeflowing muffler that's most likely going to be less restrictive then the small diameter, crush bent piping thats on most cars anyways. Me, I removed my muffler (well actually it fell off) and when I realized how HEAVY it was, I replaced it with a length of resonater piping and a resonater tip MEANT to replace the muffler. Sure it's a little louder than stock, but I've heard cars with straight though mufflers that were plenty louder. And the best part is I payed around $20 for the whole deal (which saved me money), lost a few pounds, and it sounds mean as hell without having to yell over it at idle.

 

I see your point, but disagree...

The wastegate is a good example.... pressure is relieved when the wastegate opens, and the turbine will go no faster... no back pressure... no movie movie the turbine. Am I looking at it the wrong way here? I hope reading "Maximum Boost" didn't make me "dumber."

EDIT:

I should clarify that I meant "backpressure" before the turbo, on turbocharged cars... after the turbo, yes, you want 0 backpressure.

 

You read Maximum boost... Oh well theres your problem . No I'm just playing. I've never even read that book. No actually since the waste gate is upstream of the turbine it doesn't affect backpressure down stream of the turbine. When it vents, it's simply allowing the exhaust to route around the turbine so the turbine has no way to spool. Essentially, it just reroutes the exhaust around the turbine and (in a street vehicle anyways) back to the exhaust downstream of the turbine. The turbo is bypassed. So the wastegate has no affect on the backpressure of the system, it just regulates if the turbine see's that pressure or not.

Now look at this way: The turbine spins by the exhaust flowing through it, correct? Now it would stand that the faster the exhaust flows through the turbine the faster the turbine spins, correct? now any backpressure aft of the turbine is only going to slow exhaust flow through the turbine as the exhaust begins to back up from that pressure. Therefore, spool would be affected negatively. If the backpressure is too extreme, the turbine may actually overheat in high RPM (turbine RPM, not engine RPM) which can range from warping it to complete obliteration of the turbine. And then there's the fact that if the turbine isn't even spooled then that means there isn't much exhaust in the system. So backpressure wouldn't even be an issue without exhaust flow. Now if the exhaust was small enough to produce backpressure before there was enough exhaust flow to spool the turbo then that means once there is enough exhaust flow, and then as you reach higher RPM's that there would be far too much backpressure for the system to operate efficiently.

You can't run too big a pipe on a turbo engine. You can run bigger than is practical however. And then theres the fact that the bigger the tubing the bigger the price. And of course you can TRY to fit a 4" exhaust to the underside of the car SO it would only be reasonable to use the smallest piping you can safely (and then some) get away with.

 

I think we're trying to make the same point... but wording it diff. Anyway... Maximum Boost is a good book... check it out sometime.

 

I have a first edition copy. Back pressure after the turbine is bad. I was actually working with Turbo Tom on a new custom exhaust manifold for my turbo Z before his untimely death early this year...

He got the nickname for a reason. He's the most knowledgable expert on the practical application of turbo's that I've ever come across. His knowledge is primarily derived from his work turbo charging aircraft. Playing with airplanes is a completely different engineering exercise than with cars. When you blow your car motor you're stuck on the side of the road for a few hours, if you blow your aircraft motor, people have a tendancy to die.

1.25" header pipes to a 3" downpipe to a 3.5" straight pipe with no bends or muffler is the best thing you can do for your turbo.

 

Yeah after I typed all that too Oh well. And just to clarify some common myths about back pressure, here's a little info for all you guys who don't know this:

Backpressure in exhaust piping is simply a corner being cut. It's absolutely in no way needed on any type of vehicle if certain steps are taken. The way back pressure works is that it helps (to a point) control exhaust VELOCITY coming from each cylinder. This is important. How you want your engine to perform depends on this. But you don't need back pressure to achieve the "low end" results that are talked about. It's just the cheapest and most misunderstood way (ignorance is bliss ). To say that a certain size pipe is needed at each HP level is ludacris (Nismo I know you were just quoting another source). If anything, those piping diameteres should be looked at as minimums. Dont think oh I only have this much power so I only need this size pipe. No it should be I want to make this much power and I'm going to need this size pipe to able to flow enough air to do that. Anyways, the term backpressure is WAY over used. It's not even back pressure you're after, it exhaust VELOCITY. With a properly tuned set of headers you can achieve any results you'd like from your engines power band. You can tune for high RPM, for low end torque, or for the middle ground and anywhere in between. It can be as simple as using longer primaries to achieve the low end torque you crave. This in a nutshell creates the backpressure needed to control the exhaust pulses in the way neccessary to achieve those results. You could forgo the entire rest of the exhaust system without losing any noticeable low end with a proper set of headers. Want top end, use shorter primaries. IF you really want to get in depth with tuning em you can alter the length, diameter and shape of each individual runner based on the exhaust pulses and timing of each cylinder, to control VELOCITY. You can also decide which cylinders to pair together into secondaries for further tuning based on the same factors. These are all things that are designed into GOOD header. And a GOOD header is worth every penny. It's not just welding a bunch of pipe togegher. Thats where you get mediocre headers from.

Just a little info since everyone is sooo infatuated with backpressure (of any kind). Fubar, go ahead fart here

Oh, and Nismo, I still disagree 0 fore (with the exception of the exhast manifold itself) and 0 aft. Backpressure before the turbine is only going to slow and cool the exhaust flow into the turbine, both have negative affects on spool. Unless you meant before as in how the wastegate affects the flow, in which case you would be correct. If the waste gate posed no backpressure then the exhaust would simply flow through the WG and not the turbo. And let me explain this, the only reason you need the backpressure before the turbine has nothing to do with spool but with evacuating the cylinders.

 

right... and backpressure before the turbine is... ?

 

read the very last line of my post above on that question.

 

Backpressure before the turbine is only good if it increases the velocity of the exhaust as it encounters the turbine. Otherwise, it's bad as well.

The key is to keep the exhaust gas flowing as quickly as possible so it will transfer as much energy as possible to the turbine.

If your exhaust runners are too wide, the gas pulse will expand outward reducing it's velocity.

As J mentions, you have to carefully match the length and width of your runners before the turbine collector in order to maximize exhaust velocity and minimize spool time.

 

that's the only point I was trying to make... whew! too much typing for that one