acMAX

Sup guys.....

I was wondering......I've got an HKS rear section exhaust on my 2k1.
What size b-pipe would provide the most optimal gains on my car with
my HKS?

2.5"? or 2.25"?

What size are our stock b-pipes anyway?


Same question for the y-pipe....which size will provide most gains?
2.5"?
3"?

Thanks

jhans114

iTrader: (3)

If your naturally aspirated, then stick to the smaller size pipes because you wil loose too much back pressure and may actually loose power,, now if you decide to supercharge then go with the bigger pipes.

suds1

Stock B-Pipe is 2"

acMAX

what size y-pipe would you recommend for a "naturally aspirated" car like mine (just an intake)?

3" would probably be too big right?

y2kse

iTrader: (1)

Ah yes. The backpressure myth rears its ugly head once again.

There is no such thing as "good" backpressure. ALL BACKPRESSURE IS BAD. The key to making power is exhaust stream velocity, not backpressure. If you're interested in exploring this further, take a look at the following article:

http://www.magnaflow.com/05magazine/05sportc.htm

I'd suggest you use at least 2.5" piping throughout. On the other hand, you might be better off with 3.0" piping throughout. For an explanation as to why I say that, check out the letter called "Exhaustive Research" on page 26 of the May 2002 edition of Sport Compact Car.

max'n out

2.5 is what you need.

Stock is 2.5 at some place and at others little more than 1.

sleepermax

iTrader: (5)

Well I think we're just using different terms/words to say the same thing. Granted "backpressure" may not be a technically accurate phrase. However, exhaust velocity increases because the pressure at the manifolds increases due to the additional flow resistance of smaller piping. Think of it this way, if the pressure were the same at the exhaust manifolds as it was at the muffler tip - there would be absolutely no flow (as is the case when the engine is off).
Here's another analogy: when you blow air through your lips you increase the speed at which the air comes out by either pursing your lips further and/or exerting more pressure from your gut, i.e. increasing "backpresssure"/flow resistance/exhaust velocity/evacuation ect, ect.

Thus, when someone says you need "a little backpressure" - they are referring to the increased resistance that smaller piping creates. This increases resistance raises pressure at the manifolds ("backpressure") which pushes the exhaust to a greater velocity.

acMAX

okay....so according to all this information I would
be wise to go with a 2.5" y-pipe and a 2.25" b-pipe.....
right?

or possibly a 3" y-pipe with 2.5" B-pipe.....

keep in mind I have just an intake and HKS (rear section)
exhaust.

Let me rephrase this a bit....

If YOU had just an intake (JWT w/ custom midpipe) and an HKS (rear section) exhaust and you are now about to buy an aftermarket
y-pipe and a custom-b......which sizes would you choose and why?

Thanks again guys...

y2kse

iTrader: (1)

"Whad he say, ma?"

"I dunno, son. Beats the **** outa me!"



Man, that's what I call weird science. Before you dig yourself in any deeper, sleepermax, I'd suggest you look at the letter in the May 2002 edition of Sport Compact Car that I referred to above.

sleepermax

iTrader: (5)

I'll try to state this in a simpler way (this is not my opinion, it's simple thermodynamics). What makes gas move faster? A greater difference in pressure (an increased "pressure drop").

acMAX

okay....so according to all this information I would
be wise to go with a 2.5" y-pipe and a 2.25" b-pipe.....
right?

or possibly a 3" y-pipe with 2.5" B-pipe.....

keep in mind I have just an intake and HKS (rear section)
exhaust.

Let me rephrase this a bit....

If YOU had just an intake (JWT w/ custom midpipe) and an HKS (rear section) exhaust and you are now about to buy an aftermarket
y-pipe and a custom-b......which sizes would you choose and why?

Thanks again guys...

sleepermax

iTrader: (5)

Go with the standard 2.5" Y and make get the B-pipe the same dimeter as the small pipe section attached to the HKS muffler (it's likely either 2.5" or 2.25" - either will be fine).

y2kse

iTrader: (1)

I understand. But it strikes me that there's more to this than just a pressure drop. After all, isn't there some "push" happening as the gas escapes the cylinder? And how do the "push" and the "pressure drop" interact? And even if you explain it to me, will I know what the hell you're talking about?

The idea that a smaller diameter pipe increases flow velocity is challenged in the letter I referred you to. My recommendation once again is to read that letter. I'm quite confident it will give you food for thought.

sleepermax

iTrader: (5)

I read the letter. Problem is they don't define what "backpressure" is - this is what confuses the issue.

The push is the effect of the pressure difference in the cylinder from that in the atmosphere. This is the only "force" that will cause gas to move in an atmospheric environment.

There are many factors that go into tuning an exhaust system. These depend on what you want to achive and maximize under varying loads - do you want low-end torque?, do you want maximum horsepower?, do you want more mid-range torque? ect.
The "trick" is to achieve a balance (pipe diameter being one factor) that gives you the most of everything.

y2kse

iTrader: (1)

That's great, sleepermax. I assume that you read BOTH the letter that appeared in the May 2002 edition of Sport Compact Car and the article that appeared in the November 2001 edition of Sport Compact Car. I also assume that when you read the letter (as opposed to the article), you noticed that there was a direct relationship between pipe diameter and horsepower increase.

The author of the letter (as opposed to the article) implied that a normally aspirated 3.0L engine should use 3.0" piping to achieve the greatest flow rate and horsepower increase, and he had the data to back up his assertions.

Any comments?

sleepermax

iTrader: (5)

Did you actually READ through the Magnaflow article you mentioned????

quotes from the Magnaflow article:
"An exhaust pipe that is too big in diameter has low backpressure but lower velocity. The low velocity reduces the effectiveness of this scavenging effect, which has the greatest impact on low-end torque.
Low backpressure and high exhaust stream velocity can be achieved by running straight-through free-flowing mufflers and SMALL PIPE DIAMETERS."

"PIPE DIAMETER GUIDELINES
Some basic exhaust pipe diameter guidelines for [non-turbo] cars are as follows:
1,500cc-2,000cc engines : 2-inch
2,100cc-2,500cc engines : 2.25-inch
2,600CC-3,000CC ENGINES : 2.5-INCH"

If you're running your engine all-out, all the time, as in a racing situation - then yes biger pipes will help. However this will be at the expense of low-end torque. Considering we're operating our cars in the low-end of the rpm band 99.9% of the time (under 4K rpm or so) - 2.5" or 2.25" piping is the way to go.

max'n out

I'd hate to stop the argument and answer this but I will:

You want 2.5 y pipe, mandrel bent 2.5 b pipe and your hks muffler.

This will work up until your boosted with over 10psi.

y2kse

iTrader: (1)

Did you actually READ through the letter I referred you to in the May 2002 edition of Sport Compact Car that rebuts some of what was said in the Magnaflow article, particularly with respect to pipe diameter guidelines????

acMAX

Hi Jayson

I'll be getting the 2.5" y-pipe but in regards to the b-pipe.
I'll probably be getting a 2.25" b-pipe. Do you think this size
might be "restrictive"?

max'n out

Why would you not want to maintain the same size the whole way back? More or less thats stock. Stock is 2.5 at some place and smaller in others, down to as little as little more than an inch, the gain comes from keeping it consistant the whole way. So having a 2.5 y, 2.5 b, 2.5 cat, and the muffler would probely give you the best setup.

sleepermax

iTrader: (5)

no need to get testy now.....I would think Magnaflow knows what they are talking about regarding exhaust matters since this is what they DO.

Guest

I don't like these threads.
2.25" N/A 2.5" Boosted.

Y 2.25" Bigger you make the piping, the louder the exhaust tone.
After a discussion w/ acMax, I told him 2.5" w/ resonator and HKS will be louder than his stock B-Pipe w/ resonator.
The 2.25" w/ resonator will increase sound marginally, but will flow better than the factory B-Pipe, giving his HKS rear section a better tone. The Y-Pipe will introduce a potential "rasp" and have warned him about it, but worse comes to worse, we get a second resonator after the first bend to passenger side to kill some of the rasp before getting to the HKS rear section.

I redid ToyLet902's exhaust system a few days ago, and it sounds alot better than my 1st attempt when I built his system. His car now sports dual 3.5" oval tips that fill in the rear valence lovely. The exhaust tone is deep, and not raspy.
Nissanmaximas, Playero, Max420, 1HOTMAX, Crazy4maxima, Golden glory have all heard this exhaust, and its perfect w/ 2.25"

I run 2.5", only because, thats the only SS size I could get, and since it was my first time playing w/ a TIG welder, made my exhaust system my first project. Obviously I have a purpose as mentioned above. My factory muffler has a subtle tone to it now, definitely louder over stock, and for races, I have a flange that I can unbolt, and remove my factory muffler, and install (2) 4" resonated tips I custom built for the ultimate flow, and have no regard to the sound of the set up. Makes Mustang Flowmasters sound like a mouse squeak, especially around 5000-redline.

acMAX

dude...I don't know why I even bother with these posts and sh*t...
next time I'll just call you direct....

thanks man...

sleepermax

iTrader: (5)

Chimp - good to have you back.
so what does "No Y-Pipe, No Intake For A Reason." mean again?
(btw, I'm the guy that sold the VB to Rba)

Guest

iTs a sTock air box and a sTock exhaust manifold pipe.
for some reason it makes my car somewhat, quicker ?
I can peel 1st, lots of low end torque from the stock setup.

ToYLeT902

iTrader: (12)