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 Post subject: Good Exhuast Write Up
PostPosted: Sun Jul 17, 2005 12:38 am 
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Location: South Point Ohio
Do you REALLY know how important your exhaust system is? Tuning your exhaust isn't about SOUNDING cool. It's about going fast.

I've learned my fair share of tips and tricks over the years, from many people who've been in the racing business for decades. So now it's time to talk exhaust.

Lets start from the engine and flow back (pun intended).

Cylender head- to port or not to port?
The first place your exhaust sees when it's leaving the engine is the cylender head. Your car can only suck in as much air as it can pump out, remember. Although not necessary for engines that are not severely modified, a good port and polish will give you a little HP. A port and polish (AKA P&P) opens up the exhaust ports to a larger diameter (port) and smooths them out (polish) for best flow. Most people take their heads in to have them P&P'd, but if you're willing to take the risk you can do it yourself.

Cam Timing- where being retarded can be better
In order for your exhaust to leave the engine, the cam has to open up the valves so the piston can push it out. Most cars are timed a little bit advanced, which allows for better fuel economy, better low-end torque and cleaner emissions. But (unless you're FastFireTwoTwo) you want to go for top-end power. An adjustable cam gear should do the trick for most cars. Play around with the timing a bit and see where your car likes it best. When you're at the track, make several runs at different degrees of timing and see what gets you the best ET. Also note that when adjusting timing you will want to change your shift RPM slightly (a little higher when you retard it, a little lower when you advance).

Stock manifold vs. Street header vs. Race header
Your stock manifold has one thing in mind- low end torque. While it makes the car more drivable, it also robs you of high-end power. One thing you can do is get your stock manifold ported and polished. This will give you a little more high-end power while not sacrificing much low-end torque. A street header is the best option for a dual purpose (street and race) vehicle. It offers good high-end power and decent low-end torque, keeping the car drivable on the street, yet making it more powerful when racing. A race header has one thing in mind- top-end power. It sacrifices a lot of bottom-end torque while giving you massive top-end power. However it's not very good for a dual-purpose vehicle, because you have to rev higher to start moving.

Your catalytic converter
This one here is actually a no-brainer. Cats rob power. If you can get away with it, get rid of your cat. However if you get caught it's a $1500 fine from the EPA (I'm not responsible for your actions!). If you need a cat, however, go with a nice high-flow cat. In your Summit Racing catalog, look for a good high-flow cat. I know they are available for under $75, and will make a drastic improvement over your stock cat. I know someone who had a stock cat on their car and ran a 17.1, then a month later ran a low 16 with a high-flow cat. So yes, the cat makes a huge difference!

Your muffler(s)
There are LOTS and LOTS of mufflers out there. Don't be fooled. Replacing your stock muffler(s) with a big chrome one doesn't do anything but make noise. IT WILL NOT INCREASE YOUR HP, even if it claims to. Your stock exhaust system was designed to make low-end torque, not high-end power. A high flowing muffler without a high-flowing system is like a band without a conductor... it might make some noise, but it won't do anything productive.

When looking for a muffler to go for power, look for a muffler that you can see straight through, and the muffler body should not be much larger than the inlet and outlet. Also look through the muffler. Does it look like a screen in there or is it louvered? A "screen" muffler will flow a lot better than a louvered one. Another good option (if you have the money) is a Supertrapp muffler. These mufflers sit on the end of your exhaust system (like a tip) but are tunable. You can add discs to them to make them more free-flowing (top-end power) or remove them to make more backpressure (low-end torque).

How big?
When making a FULL exhaust system, make sure all your components line up. Most street cars don't need any more than a 2 1/2" exhaust system. A good rule of thumb is to make your new system 1/4-1/2" larger than your stock system. So if your stock ststem was 2", get your (header/manifold) to be 2 1/4"- 2 1/2"... and make everything else the same size (or slightly larger as you get farther back).

When making/buying a Cat-Back system, make sure everything after the cat (or including the cat) is the same size (or getting slightly larger farther back). A Cat-Back system is nice but often very expensive. Check with your local muffler/exhaust shop before ordering anything. They might be able to make you a system for cheaper. Sure, it won't be stainless steel... but if you're REALLY going for power, that doesn't matter.

A little tip I learned from a Pro-Vee racer
If you REALLY REALLY want power I have a tip. Note this may be illegal. Take a can of cheap spray paint and paint your exhaust system white from the cat back. Drive around for a day or two then look at the system. Most of the system will be black (the paint burned off). Where the paint stops turning black is where the exhaust is mostly cooled and is just "along for the ride". Now get your hacksaw and cut your system off just after that point. Bolt on a high-flow muffler (if you removed all your mufflers). Then target that exhaust right out the side using a 90º or a 45º bend and some straight pipe. This is what I did. It cost me all of $40, made my car sound nice, and made my exhaust flow like the Mississippi.

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PostPosted: Sun Jul 17, 2005 8:54 am 
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Excellent right up, especially for beginners. Looks like I pretty much followed all of your suggestions in the first place, so I'm on the right track. But you just had to mention something about the cats, didnt you? :wink:

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 Post subject:
PostPosted: Sun Jul 17, 2005 9:44 am 
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Not to be negative, but I do have a little experience, and would disagree on a few things in the article.
Quote:
Most cars are timed a little bit advanced, which allows for better fuel economy, better low-end torque and cleaner emissions

Most cars(including our Suzukis) are retarded to the order of about 4-6 degrees. The 89-up 3's are retarded 10 degrees from where they should be, which is about 106 degrees ATDC. This is for emissions.
Quote:
Don't be fooled. Replacing your stock muffler(s) with a big chrome one doesn't do anything but make noise. IT WILL NOT INCREASE YOUR HP, even if it claims to. Your stock exhaust system was designed to make low-end torque, not high-end power. A high flowing muffler without a high-flowing system is like a band without a conductor... it might make some noise, but it won't do anything productive

Try replacing your stcok muffler with a good quality free flowing muffler on any of our Suzukis. It has worked well for me. You will make more power. The stock muffler is very restrictive.
Quote:
Another good option (if you have the money) is a Supertrapp muffler. These mufflers sit on the end of your exhaust system (like a tip) but are tunable. You can add discs to them to make them more free-flowing (top-end power) or remove them to make more backpressure (low-end torque).

I don't have personal experience with Supertrapps, but I've never heard anything good about them, and plenty bad. Don't equate backpressure with anything good, like low end torque. Backpressure in any way is bad for power. It is exhaust flow velocity that will help low end power.
I am starting to learn just how sensitive 16V motors are to change. In the same way that you could use a cam that has 40 degrees more duration in a 2V/cyl. motor, and make excellent broad RPM power, do it to a 4V/cyl. motor and see how your powerband moves up 4000RPM. The smaller the motor, the lesser ability it has to absorb that change without negative effects. I think that you can also use the same theory with exhaust systems. Where I run 2" on my non-turbo 3's, I think you would probably benefit from a good free flowing 1 3/4" - 1 7/8" on your GTi. Exhaust flow velocity will go south in a big way with all the valve area, if you don't size the tubing properly. At least thats my theory. :D

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 Post subject:
PostPosted: Sat Jan 14, 2006 9:56 pm 
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Location: Auburn Wa
Exhaust velocity is very important. You can actually get more scavenging by using an exhaust that creates high velocity. The reason for this is.... the higher the exhaust flow the more it pulls from the exhaust manifold, head, and cylinder. Mufflers slow this pull by creating preasure. Cats create even more preasure.

Would open exhaust be the best you can get, say comming out your headers? Well that depends on your target RPM range. On an economy box geared for an emphasis on milage only you need to focus on low rpm and this means high flow for less exhaust (low RPM). Smaller pipes are suited for higher pipe flow velocity and less volume. Bigger pipes are suited for higher pipe flow and higher volume. What this means is your pipes should be sized for your particular engine size, RPM range, and driving habits. If you like to rev out a bit and then drive the speed limit... maybe your looking for a slightly bigger pipe than stock like a 1/8th inch or 1/4 inch. If you like to drive for highest milage... Then the stock size is probably for you. If your a Street Strip driver than you may wish to go 1/2 a inch bigger or so. In any case a free flowing muffler and cat is what you should be shopping for. With a free flowing exhaust you almost always will get more noise. Best to go to some car shows and listen to what others are running to get an idea of what you would like your car to sound like.

I personally like flowmaster mufflers. They make a deep throaty sound and are quiet when cruising but get louder when your on the throttle. They make a pretty broad range of mufflers. Expensive though.

If working on a v6 or v8 it is a huge difference to run a couple of crossover pipes to share a couple of mufflers and cats. The crosover pipes should face towards the back of the ehaust and not be just a straight T from one pipe to the other.

Always trim the crossover pipe first then make the cuts into your exhisting pipes. That way you can fit them and locate them prior to fitting them. Also the crosover pipe Should not protrude into the main ehaust pipe. The crossover pipe can also be much smaller than the main pipe as it won't be carrying full exhuast flow.

This is a example of a newer crossover design. It makes me go Hmmm. http://members.aol.com/xforcefast/

This is an example of the worst crossover system involving a "H Pipe" Picture is about halway down http://www.carcraft.com/techarticles/69238/
This is not very good as the direction of Exhaust flow has to make 90 degree direction changes and when it enters the main pipe next to it, it actually slows the outgoing velocity of the exhaust gases in that pipe.

This is an example of a "X Pipe" Design. It allows the gases to slam into one another but not nearly as bad as the "H Pipe" design. Flow master mufflers use this design to propogate noise reduction withing their mufflers. http://www.torquetechexh.com/xpipe.htm

The dual crossover pipe design with crossover pipes set at 45 degrees between the two main pipes has long time been my favorite setup of mine. I cannot seem to find a good picture of that setup right now.

This is a pic of the wildest Header setup I have seen to date. It combines two headers to take advantage of the 90 degree pulses of the engine. A truly sweet setup. http://www.thepowerbroker.net/scavenger.htm

Now for the single exhaust. You can use a y pipe towards the back of your exhaust to split it into two cats and two mufflers. This will maintain veloctity down your main pipe and then split the restriction of the cat and muffler into two cats and two mufflers. This should greatly reduce back pressure. Designing a good exhaust may be a bit tricky to get this type of system to work best.

Be aware that when you improve your exhaust flow you have to make adjustments on your fuel air flow mixture. Depending on the amount of improvement.... determins how much adjustment you may have to make!

Good Luck.


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 Post subject:
PostPosted: Fri Aug 03, 2007 2:51 pm 
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Joined: Fri Aug 03, 2007 9:57 am
Posts: 103
Location: Jersey city, U.S.A
Great write-up, but im in no way capable of doing this, i might gonna get addicted to this forum reading all this info!

any performance muffler shop in nj/ny area you guys would recommend. And how much would it cost? Total up-to-date 2007?

thanks in advance.

ponzy


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 Post subject:
PostPosted: Fri Oct 05, 2007 7:48 am 
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Location: ZH
What is the best and most silence exhaust for my 3-banger?

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 Post subject:
PostPosted: Mon Nov 12, 2007 10:48 pm 
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Posts: 569
Location: dunnville, ontario,canada,the world,the universe
lol on my old 89 civic i ran the si MPFI 1.6l engine in my cx (base base model) i ran a ractive 2 1/4" 4-2-1 header and then 2 1/2" mid pipe with no cat, then ran a 2 1/2" magnaflow side mount muffler and man it was a little more lag in the city driving but on the highway at high speeds you really felt the big improvement. just next time i might run a high flow cat instead of none cause when i was doing 190kmh/208kmh you could really smell it bad, but i really enjoyed the back firing :D



one question actually that i have is how much of a lag is it from a stock crimped like exhaust to a mandrel bent exhaust? could you get much of a gain running the same as stock exhaust just mandrel bent? is it really that effective?


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