engine and drivetrain There's headers and there's HEADERS

[Scott Sislane]

I had the larger of the two you have there, for a couple months, before I went to a simpler set-up. It definitely made a noticeable diff but the clearance issue and space it took-up, wasn't worth it for me.

It was a VERY noticeable diff. I have side-drafts also. If I didn't do so much around town driving & have kids, I would have kept it on.

The buyer, who is in HI, is on here & installed it. Maybe he'll give you some feedback. ( lighthousemaui - Gary )

I rest my case

What case is that? As the majority of replies suggest, there are no absolutes that bigger is better.

This poster does not state he tried smaller diameter tubing too. If that were the case he might have had better results. He just said he tried a "simpler setup", whatever that means. He mentions "clearance issues" and "space" and "kids" (suggesting decibels level issues). This noise may have also clouded the original poster's perception of improvement too.

I went to smaller exhaust air volume, from the header to the ctr resonator. Went from the stahl header to a shorty header feeding down through a stock down-pipe. Same ctr resonator (ansa), same muffler (ansa) on the back-end. When I pulled the stahl header, and installed the shorty header w/ the stock down-pipe, the loss of power was immediately noticeable. And it is quieter as well, as I expected.

The noise did not cloud my my perception by any means. The diff was very obvious.

I've done all the work to my car(s), including stripping the entire engine bay and replacing almost every single piece, tranny as well. Obviously there's a point where lack of back-pressure becomes detrimental, unless it's compensated for.

I also have a good 02 friend who drove the car b4 & after and he agrees w/ what I'm saying...

for what-ever that's all worth...

[allbim]

The problem with this subject is that you can write a book about it and many books have been written about it. So when you then come up with a simple and short answer, you invariably end up spending lots of time arguing about it. One thing is sure, you don't make big HP with small pipes. Torque is another matter. All properly designed naturally aspirated engines put out about the same amount of torque for a given displacement. The only difference between the low and high performance engine is that the torque is produced at higher RPM. I'm not saying that you can't screw up your engines torque by overdoing one thing or another in the intake or exhaust system. The whole system has to work as a aaaah system. This is of course just another simple and short answer.

[ricortes]

it will loose a lot of low end torque if run with 3 inch collector and a big pipe out of the back, but the peak hp should go up anyhow. Don't see how it's possible to put out less power with larger diameter pipe.

I would use the big header with a reducer and a 2 inch pipe out the back with a good flowing muffler.

Moving air has inertia just like a rolling car or throwing a rock. Haven't looked at the cam specs for a 2002 but I would bet donuts there is valve overlap. Valve overlap is defined by the time in degrees that both the intake and exhaust valves are open. While it may seem counter intuitive that both should be open at the same time i.e. exhaust back pressure preventing new charge from entering or down stroke of piston sucking exhaust gases back into the cylinder instead of fresh charge, it helps engine performance in a manner analogous to a tuned exhaust on a two stroke engine.

It actually wasn't invented by the 'Ram Chargers' of Dodge fame in drag racing. I think the phenomina was first characterized in Europe in ram pumps for moving water. If you've ever noticed when you put your thumb over the nozzle of a hose the effort to restrict flow goes down over time as the water in the hose slows and loses energy.

So yes, it is possible to go too big and not get the benefits of scavaging from the exhaust pulse. It's also possible to have a cam with different degrees of overlap and timing that will not sync with a given header. Kind of like trying to tune a saxaphone: If you take the mouth piece out it just softly squeeks.

Rick

[allbim]

it will loose a lot of low end torque if run with 3 inch collector and a big pipe out of the back, but the peak hp should go up anyhow. Don't see how it's possible to put out less power with larger diameter pipe.

I would use the big header with a reducer and a 2 inch pipe out the back with a good flowing muffler.

Moving air has inertia just like a rolling car or throwing a rock. Haven't looked at the cam specs for a 2002 but I would bet donuts there is valve overlap. Valve overlap is defined by the time in degrees that both the intake and exhaust valves are open. While it may seem counter intuitive that both should be open at the same time i.e. exhaust back pressure preventing new charge from entering or down stroke of piston sucking exhaust gases back into the cylinder instead of fresh charge, it helps engine performance in a manner analogous to a tuned exhaust on a two stroke engine.

It actually wasn't invented by the 'Ram Chargers' of Dodge fame in drag racing. I think the phenomina was first characterized in Europe in ram pumps for moving water. If you've ever noticed when you put your thumb over the nozzle of a hose the effort to restrict flow goes down over time as the water in the hose slows and loses energy.

So yes, it is possible to go too big and not get the benefits of scavaging from the exhaust pulse. It's also possible to have a cam with different degrees of overlap and timing that will not sync with a given header. Kind of like trying to tune a saxaphone: If you take the mouth piece out it just softly squeeks.

Rick

One way to demonstrate the inertia of air is to stick a long piece of tubing (garden hose) in your mouth, blow hard and then suddenly stop blowing.

The momentary vacuum generated in your mouth is very noticeable. Imagine what happens when the gas moves at near the speed of sound.

[NMDerek]

well I just learned alot 13 years later. 

[visionaut]

This belongs here…

 

https://www.bmw2002faq.com/forums/topic/146220-stahl-header-vs-tii-manifold-response/

[66Vette]

I've never used this program so can't speak to the user interface, but this is used by many engine builders for header design.

 

MaxRaceSoftware

WWW.MAXRACESOFTWARE.COM

 

 

I have used Engine Analyzer Plus.  If I remember correctly it allows some of the header parameters to be specified and you can see the impact on HP and Torque.  This program was pretty accurate predicting HP on a small block chevy build.  I feel its best use is to evaluate differences when making changes like cam specifications, not so much on nailing down an exact HP figure.  For an M10, you may have to be creative in entering things like intake manifolds.  And remember, GIGO.

 

https://www.performancetrends.com/