X vs H pipe, any benefit over the other?

Topic: X vs H pipe, any benefit over the other? (Read 4194 times) previous topic - next topic

X vs H pipe, any benefit over the other?

Reply #30 – July 27, 2009, 08:21:36 PM

You also need O2 sensors with longer wires, O2 sensor extensions, or to solder and extend the current O2's.

X vs H pipe, any benefit over the other?

Reply #31 – July 28, 2009, 02:12:19 AM

I don't understand this line of thinking. Your motor is like an airpump. The more bends and restrictions you have, the less efficient the setup is as a whole. HP is a measurement of torque and the other way around. I don't see how you could gain one and lose the other by making it more efficient.

And if your going to an H.O. setup later on, why would you even consider getting 2 1/4 pipes? If I had enough money I would be going with 3" duals. A bigger exhaust will always show power over a smaller one, just like swapping intakes. No one says that swapping on a H.O. intake kills torque.

X vs H pipe, any benefit over the other?

Reply #32 – July 28, 2009, 06:59:45 AM

No it won't.
An engine requires a certain amount of back pressure to function correctly at given performance levels.
If you ran open headers on an SO for instance you would loose a substantial amount of torque due to the complete loss of backpressure(exaust scavenging).

Quote:
Exhaust Scavenging

When an engine starts its exhaust stroke, the piston moves up the cylinder bore, decreasing the total chamber volume. With the exhaust valve open, the high pressure exhaust gas escapes into the exhaust manifold or header, creating an exhaust pulse comprising three main parts: The high-pressure head is created by the large pressure difference between the exhaust in the combustion chamber and the atmospheric pressure outside of the exhaust system. As the exhaust gases equalize between the combustion chamber and the atmosphere, the difference in pressure decreases and the exhaust velocity decreases. This forms the medium-pressure body component of the exhaust pulse. The remaining exhaust gas forms the low-pressure tail component. This tail component may initially match ambient atmospheric pressure, but the momentum of the high- and medium- pressure components reduces the pressure in the combustion chamber to a lower-than-atmospheric level. This relatively low pressure helps to extract all the combustion products from the cylinder and induct the intake charge during the overlap period when both intake and exhaust valves are partially open. The effect is known as scavenging. Length, cross-sectional area, and shaping of the exhaust ports and pipeworks influences the degree of scavenging effect, and the engine speed range over which scavenging occurs.

The magnitude of the exhaust scavenging effect is a direct function of the velocity of the high and medium pressure components of the exhaust pulse. Performance headers work to increase the exhaust velocity as much as possible. One technique is tuned-length primary tubes. This technique attempts to time the occurrence of each exhaust pulse, to occur one after the other in succession while still in the exhaust system. The lower pressure tail of an exhaust pulse then serves to create a greater pressure difference between the high pressure head of the next exhaust pulse, thus increasing the velocity of that exhaust pulse. In V6 and V8 engines where there is more than one exhaust bank, Y-pipes and X-pipes work on the same principle of using the low pressure component of an exhaust pulse to increase the velocity of the next exhaust pulse.

Great care must be used when selecting the length and diameter of the primary tubes. Tubes that are too large will cause the exhaust gas to expand and slow down, decreasing the scavenging effect. Tubes that are too small will create backpressure against which the engine must work to expel the exhaust gas from the chamber, reducing power and leaving exhaust in the chamber to dilute the incoming intake charge. Since engines produce more exhaust gas at higher speeds, the header(s) are tuned to a particular engine speed range according to the intended application. Typically, large primary tubes offer the best gains in power and torque at higher engine speeds, while smaller tubes offer the best gains at lower speeds.

Many headers are also resonance tuned, to utilize the low-pressure reflected wave rarefaction pulse which can help scavenging the combustion chamber during valve overlap. This pulse is created in all exhaust systems each time a change in density occurs, such as when exhaust merges into the collector. For clarification, the rarefaction pulse is the technical term for the same process that was described above in the "head, body, tail" description. By tuning the length of the primary tubes, usually by means of resonance tuning, the rarefaction pulse can be timed to coincide with the exact moment valve overlap occurs. Typically, longer primary tubes resonate at a lower engine speed than shorter primary tubes.

Some modern exhaust headers are available with a ceramic coating. This coating serves to prohibit rust and to reduce the amount of heat radiated into the engine bay. The heat reduction will help prevent intake manifold heat soak, which will decrease the temperature of the air entering the engine.

Similar aspects apply when an intake is too large or too small.
Dual 3" exaust is way too large and you would suffer the same fate.
3" exaust would be a requirement at around 5-600hp levels.
I run 2.5" on my 500hp setup and it works excellent.

X vs H pipe, any benefit over the other?

Reply #33 – July 28, 2009, 06:57:59 PM

Quote from: Haystack;284170

HP is a measurement of torque and the other way around. I don't see how you could gain one and lose the other by making it more efficient.

And if your going to an H.O. setup later on, why would you even consider getting 2 1/4 pipes? If I had enough money I would be going with 3" duals. A bigger exhaust will always show power over a smaller one, just like swapping intakes. No one says that swapping on a H.O. intake kills torque.

Your first statement is partially true...horsepower is calculated from torque...but it certainly does NOT work the other way around...torque is a measurement of torsional forces(twist) and that's it. A larger exhaust will NOT always show more power...that's the "bigger is better" trap that a lot of people fall into.

Increasing airflow will make the engine more willing to run at higher RPM's...but always at a loss of low speed torque. Too large of an exhaust may gain you 5 hp over 4,500rpm, but at the same time, the torque curve shifts higher and you lose valuable low speed torque. Any loss of low speed torque will greatly affect acceleration in an AOD car.

It's all about the "power under the curve"...peak power and torque numbers are all fine and well, but it's about how broad you can make the torque curve.

Dominator, thanks for writing that up...saves me some hassle. Now if people will only read it! lol

X vs H pipe, any benefit over the other?

Reply #34 – July 30, 2009, 02:39:26 AM

That must be why alot of people run open headers at the track then.

X vs H pipe, any benefit over the other?

Reply #35 – July 30, 2009, 06:41:09 PM

Quote from: Haystack;284472

That must be why alot of people run open headers at the track then.

Only when it's right for THEIR combination. I've seen dirt track cars run varying length extensions from their header s to tweak the torque curve for particular tracks.

If you have a flyweight mustang with 4.10's or more and a stick with a nice H/C/I, then you aren't worrying about low speed torque anyway. The fact of the matter is, most guys just THINK that bigger is better...and if that's the case, none must be the best! I've seen a lot of guys running open headers who are in the 13's and 14's...it's a dumbass idea at that point.

FWIW, I've also seen back to back dyno tests(same day, same car) every exhaust system made more power and torque than open exhaust...and this was on a car making 365-385rwhp.

Everything Dominator posted previously is SPOT ON, there is no B/S there. If you choose to follow the path of a few idiots...be my guest, we're only trying to guide people down the right path(while explaining why).

Good luck,
Don

X vs H pipe, any benefit over the other?

Reply #36 – July 31, 2009, 04:06:25 PM

I've also seen a dyno sheet of a stock 87-88 mustang with a chip to correct the air to fuel mixture moving from the stock exhaust to duel 3.5" and gained all over the board, including low end. When you change your exhaust you also change the air to fuel ratio as read by the O2's. If you tune your car to run with open exhaust it will run fine on open exhaust. I really wish I could find it.

"1. There is an overly common practice to try to generalize everything using one simple metric..... and ... BTSTDT, in this case a x" exhaust system is not required for a setup making less than "y" HP....

2. The way I have always seen, noticed, confirmed a better engine behavior has been by either running open headers, or tuning the open exhaust with some old school "stingers", and "equalizing" the intake to the better exhaust flow. Simple breathing basics..... if you can exhale better, make sure you compensate on the inhalation cycle.

3. As with #2, a bigger ID exhaust system (aside the header configuration which does affect with a bigger impact) past the collector/extension... sort of, kinda, better simulates an open header situation.

4. The focus is usually placed, erroneously , in the "velocity" of the exhaust flow rather than the flow itself.

5. The scavenging effect is usually mentioned to justify the velocity over the lesser flow of the tubing yet, it has always been my understanding and results, that the pulse based scavenging is concentrated at the header-extension level after which, an unobstructed flow takes importance over velocity.

6. Anytime an open header or bigger exhaust ID system setup drops in performance, the cause is not excessive exhaust..... it's a lack of A/F."

kinda like the guy who swears by the flowmasters with 350hp, until he pulls them off and gains 35RWHP.

All of the quotes here are from guys that run a minumum of 3" exhaust on cars with anywhere from just cammed to full out race cars, and most are driven daily. several have ran 3.5" and wished they went bigger.

X vs H pipe, any benefit over the other?

Reply #37 – July 31, 2009, 10:26:54 PM

If you would like to follow more of Haystack's line of thought there is some excellent information on sbftech.com in the myths and rumors section regarding exhaust size (3" exhaust too big for a 302). If you are new to that site you need 10 posts to have access to the section.

There's a wide variety of hot rodding "lore" which has been accepted as fact for decades dispelled there (ie: the need of back pressure in exhaust and the ever classic: small cylinder heads make more torque because they create more "velocity"). It's well worth the read (and there is a lot there to read), but be prepared, it can really stretch your thinking. The indoctrination of the old school stuff is pretty hard to set aside.

X vs H pipe, any benefit over the other?

Reply #38 – August 01, 2009, 08:48:32 PM

After re reading alot of what I posted, I sound pretty pen 15y, and believe me, this is not the case. I have not modified my car much past stock and don't plan to. But I am just trying to share information that will help someone who has not looked into it so much. I am not trying to sound pen 15y or like a know it all. I just really think that having 2.5" exhaust is way to small for a v-8, at virtually any power level. being as civics with 3" exhaust gain everywhere and only have 1.5 liters N/A, I don't see how a 5.0+ liter v-8 couldn't use more then 2.5" duals.

X vs H pipe, any benefit over the other?

Reply #39 – August 01, 2009, 11:20:53 PM

Tried and true, repeatable results on a chassis dyno speaks volumes more than someone with a bunch of "theory".

I agree that running open headers on a STOCK 5.0 mustang and retuning the A/F curve will pick up HP...over a STOCK system...because you're eliminating 4 catalytic convertors and any other possible flow restriction...HOWEVER...it WILL pick up more power and especially low speed torque, with a properly sized system.

I guess companies who manufacture exhaust systems know absolutely NOTHING....some have been doing it for more years than many of us have been alive, but still haven't figured it out yet...they've got nothing on "theory".

As for those honda's with 3" "pipes"...I'll bet donuts to dollars there is a massive 1 3/4" to 3" adapter just in front of their fart cans...I see it day in and day out....hence why they are "stupid ricers".

FWIW...flowmasters make much more power and torque @ the 350+rwhp range than open pipes. Dyno charts prove it. I'll have to dig up the article...because it's not B/S.

Think about it...years of well-proven results VS. "theory"...seriously.

-Don

X vs H pipe, any benefit over the other?

Reply #40 – August 02, 2009, 04:26:00 AM

I also like reading all the MMFF articles where they pick up XRWHP and then you read the actual build on the internet where they swapped everything out but the block. Dyno's don't really show anything. You take a car to the track and it runs faster, the car is faster. You throw a 100lbs flywheel on the car and the peak HP would still be pretty close, but it would be a turd on the road. And before you start talking theory, then you really should get over there and start reading.
There are guys with right around 300hp bragging about it, and every other person throws in that there car should be good for 10's. Reading the MM&FF, they have problems getting a 550hp car with a supercharger to run 12's most of the time and the "E -cam" is the end all. I know this is not true. I'm not saying you can't run an alphabet cam, but there really isn't any reason to.

X vs H pipe, any benefit over the other?

Reply #41 – August 03, 2009, 05:10:07 PM

A lighter flywheel will make it feel like when leaving stops. I know multiple people who've used aluminum flywheels on the streets and hated it...you lose so much rotating inertia that it's much harder to get going without stalling, once moving however they're great. How we got on to this topic, nobody knows.

Believe what you want man, I guess some people just have to learn the hard way.

Good luck,
Don

X vs H pipe, any benefit over the other?

Reply #42 – August 03, 2009, 06:50:03 PM

Backpressure is NOT the same thing as exhaust scavenging or pressure wave tuning.....If I shove a banana on each of the collectors of an open header type exhaust; it sure as heck aint gonna help none.
http://www.popularhotrodding.com/enginemasters/articles/hardcore/0505em_exh/index.html

Quote

Dyno's don't really show anything. You take a car to the track and it runs faster, the car is faster. You throw a 100lbs flywheel on the car and the peak HP would still be pretty close, but it would be a turd on the road

Dynomameters are tools. They can tell you engine output at certain RPM's and are helpful in determining possible other changes in the car driveline and can give a good baseline. FWIW-- they showed me just how much power I gained on a simple re-tune and that my A/F ratio is good. Remember; everything working together is what makes the car run how it does. It's about the combo

Quote

I agree that running open headers on a STOCK 5.0 mustang and retuning the A/F curve will pick up HP...over a STOCK system...because you're eliminating 4 catalytic convertors and any other possible flow restriction...HOWEVER...it WILL pick up more power and especially low speed torque, with a properly sized system. I guess companies who manufacture exhaust systems know absolutely NOTHING....some have been doing it for more years than many of us have been alive, but still haven't figured it out yet...they've got nothing on "theory".

Theory is the basis. In reality stumbling blocks like a cramped engine bay, interference from other components (steering shaft for one), and cost effectiveness (a BIG issue on the OEM side) are the things to work around. Different companies might attack those stumbling blocks differently; hence different results.

Quote

There are guys with right around 300hp bragging about it, and every other person throws in that there car should be good for 10's. Reading the MM&FF, they have problems getting a 550hp car with a supercharger to run 12's most of the time and the "E -cam" is the end all.

This goes back to the overall combo. A shiznit suspension and hard tires will win over ANY 550 HP motor. And the E-cam makes a GREAT paper weight IMHO....

There are N/A S197's that make less power than me that are just as fast in the quarter.....I have a feeling I get MUCH better gas mileage and I know I have more top end, not to mention I'm not spinning my motor to the moon on a road trip.

In the end; it all boils down to what the person wants from their vehicle. No 2 people want the same exact thing. Except Camry owners :hick:

X vs H pipe, any benefit over the other?

Reply #43 – August 03, 2009, 07:17:26 PM

Also,H-Pipe or X-Pipe,once they are bolted on (say for example,both of them are off road pieces),you're not going to "feel" a difference in the seat between the two.Just grab one you can afford and bolt it on.

X vs H pipe, any benefit over the other?

Reply #44 – August 04, 2009, 04:01:30 PM

Quote from: vinnietbird;285115

Also,H-Pipe or X-Pipe,once they are bolted on (say for example,both of them are off road pieces),you're not going to "feel" a difference in the seat between the two.Just grab one you can afford and bolt it on.

Not sure about that,i always heard x pipes where better for low end torque.