came accross this. guy claims he gained 11rwhp by adding an x pipe

 

came accross this. guy claims he picked up 11rwhp by adding an x pipe

 

For what it is worth, I tend to follow the generally accepted popular opinion at the moment,,, H is good, but X is better....

But H is easier (cheaper) to manufacture and usually easier to implement. (due to space considerations)...

We used an H on the 66...

So, I voted X, but we used H (and would do the same again)...... The H is simple and cheap to do with virtually no possible downside... An H pipe will probably add like $10.00 to the cost of a system, making the debate about their real value practically a moot point... IMO of course!!

 

As I understand it, when Ford built a car with dual exhaust from the factory they used an H pipe. I just had a new dual exhaust setup installed in mine last week and with an H pipe for that reason.

 

I found some information in what I think was some Chevy magazine article this afternoon that I can put up a link to tomorrow (the page history is on my work computer and I don't remember which of several searches turned it up). Deeper tech than the usual write-ups.

Another good starting point is anything written by David Vizard. He was onto the benefits of exhaust flow sharing, gradual transitions, and crossovers way back before 1981 (when his softcover "Performance With Economy" came out). He was getting close to the "X" pipe design as we now know it at that time, but hadn't gotten all the way there if his book sketches were telling everything he knew. I think he currently writes a column for either Circle Track or Stock Car Racing and has touched on exhaust systems - an article that compared different header designs IIRC - fairly recently. Who knows, he might even field a well-written question or two.

I also checked over on an automotive engineering site and found a few considered opinions by some pretty sharp people but nothing with any solid numbers behind it.


Norm

 

without the H/X you're missing a bit of a bassy note. As well as peak HP.
But those 2.5" straight into a Flowmaster sounds great! agressive.

Here are mine:
http://www.youtube.com/watch?v=ugymBIBwrAI


no x/h, as far as I know stock (unported) heads and I guess original cam. Not too sure though. I have no way of telling.
You'll hear a very high pitched rattling in my video. This was the handbrake lever touching my exhaust. It's sorted now.

Have to make a new recording at some stage

Kalli

 

Here is the link I mentioned last night. Perhaps not surprisingly, it's a David Vizard piece.


Norm

 

id do an h at the minium, but an x if you want to spend a little more.

 

Kalli, that is a great article. I have gotten some of my questions answered, but also created some questions. So sorry for the hijack, but it does play into the general theme of good exhaust performance.

Answers: Crossovers may provide some help or no help, but they do not hurt. Crossovers reduce sound by 1-3dB. The crossover should be between 2.25 and 2.75" in diameter if it is going to work.

Questions: How does the secondary length play into the tuning equation when you have mufflers (i.e. if you have 4 feet of pipe from the primaries to the muffler does that mean you have a 48" secondary)? If this is the case, wouldn't the position of the muffler would be key in a tuned system? What is the resonator box thing and why do you not see it in the aftermarket world?

 

I am sorry for the hijack, but this also plays into the exhaust performance question.
Except from the Article:
"As for the secondary length-that is from about the middle of the collector to the end of the secondary (or the first large change in cross-sectional area), we find a great deal more sensitivity than is seen with the primary. Ironically, few racers pay heed to collector length even though it is easy to adjust. In practice, collector length and diameter can have more effect on the power curve than the primary length. A basic rule on collectors is that shorter, larger diameters favor top end while longer, smaller diameters favor the low end. Except for the most highly developed engines, many collectors I see at the track are too large in diameter and either too short, or of excessive length. For a motor peaking at around 6,000-8,500 rpm, a collector length of 10-20 inches is effective."

In my case, I have 3" collectors and 3" exhaust pipe. "The first large change in cross-sectional area" is my muffler. Does this mean my secondary length would be measured from the primaries to the muffler? If that is the case, then the placment of the muffler would be one of the most important measurements of the exhaust system.