Further discussion of minimc's exhaust Sticky
 

First question

Is this information accurate relating to forced induction as well?

If you listen to the arguments here and in other forums there is the constant mantra of bigger is better in exhaust design.
Big header primaries, 3" exhaust systems, etc.
There seems to be no concern for tuning headers and exhaust systems for designated RPM bands.

One thing I didn't note in this great piece of info is collector length. Collector tuning used to be a useful tool. Don't know if it's still relevant.

Rave on folks

Header design is very important,
 

no matter what's on your motor. Some follow up...

There is too big, it reduces scavaging.

But the point about exhaust needing "backpressure" at low RPMs is just wrong. If you think about it, at any time other than WOT and redline, any exhaust better be oversized, or you will choke the crap out of the motor.

But scavaging has to do with valve overlap and the like. So cam comes into play as well, and can interact with the exhaust.

The Dinan tech article about exhaust basically says post header, the back-pressure theory is BS. But you do want to tune your header for how you drive the car. For versitile cars, a tri-y is good, because you can tune it for a wider range. For full race, where you'll live at red-line, 4-1s rule, as a rule, that's often broken! ;)

Matt

Matt

So I gather you are saying that even on FI cars header tuning is still relevant.
I susoected as much but you never see that being discussed by any of the vendors or even member here.
Most times there isn't any info about the ID of primaries true equal length and especially effective RPM range.
They all tune for WOT and so aren't of much use on the street or auto-x really.

Tri -Y is what I'm looking for but as noted elsewhere here, there isn't much selection in that design.

Two ends of the spectrum,
 

OBX header is a tri-y, and very nicely priced.

Then there's http://performanceweldingheaders.com/ , you'll get what you want, but it'll cost you.....

Matt

Nice link thanks.

I've been watching the OBX thread. 2 issues for me.
1. I'm lazy and want things to work out of the box
2. Nobody I know of in my area is worth a crap with stainless exhaust systems. So I don't have anyone I can depend on to do the Cat work right.

I just didn't worry...
 

Cause with the money the OBX saves, you can always get it fixed, or even replaced later! But there are more options out now.... I just haven't kept track, because I'd closed the book on the header a while ago...

Matt

Obehave, Okay, rave mode on!:grin:
“Is this information accurate relating to forced induction as well?”
Yes:nod:
Headers that are available to us from our MINI vendors don’t post any of the pertinent information, why?
I don’t know why for sure that our MINI vendors don’t share all that vast wealth of header design knowledge either but most likely it’s because most don’t have a clue. Because if they didn’t do the tuning and design work they don’t have it or weren’t smart enough to ask for it. Maybe they farmed it out to a builder but don’t feel obligated to share the numbers because it’s for a MINI and those dummies will buy anything.:sly:
Yes, that’s how I feel when vendors make claims they don’t back-up with the data. It’s the disrespectful attitude that you get when you ask and that attitude needs to change. The consumers want to know the details as they are part and parcel of the deal.:nod:
Did the builder do the tuning or did he just mock up a cool looking header design behind the OEM header that was sent to him to copy dimensions from as a performance part for the MINI community.:eek:
That was just a guess of what goes on and you my friends are asked to spend BIG $$$ without the details.:roll:
“If you listen to the arguments here and in other forums there is the constant mantra of bigger is better in exhaust design.”
I would contend that a lot of this argumentive stuff is just noise, it comes from some who haven’t bothered to do research the subject, and some are content to just spout off hearsay, rumors and myths to keep their post count up while acting like they know something.:sad::sly:
Rave/rant over.:grin:

All of your questions are right on and valid the only thing I can recommend is to educate yourself and either build it yourself, contract a build or take your best shot at what’s out there from what you learned by researching.
So here is what I offer, links to information on exhaust flow theory, parts and builders.
www.headersbyed.com/ < Just scour the whole web site. He also has an opinion on
the industry and sells parts http://www.headersbyed.com/bildbetr.htm and stepped headers, http://www.headersbyed.com/stepped.htm

Hy tech designs and builds stepped headers they are recommended by Endyne for his Honda work.. Cost about $1,300.00 + for a one off build (MINI) because they don’t make one for our MINI engine. They must know something though.
http://www.hytechexhaust.com/ < not a lot of info but some pretty pictures to look at.

This is about 2 cycle motorcycle engines, why am I including it? Read and see,
http://www.motorcycle.com/mo/mcnuts/em-pipes.html
More really good stuff,
http://www.burnsstainless.com/index.htm < Lot’s of info, sells parts, builds.
Technical articles, http://www.burnsstainless.com/TechAr...harticles.html
For bigger is better after the header check out the BMW E30 M3 article is good.:thumbsup:

Don’t miss this report it summarizes 16 months of study into the improvement of the efficiency, power and reliability of light aircraft exhaust systems. < Graphs, charts, theory:thumbsup: http://www.cafefoundation.org/aprs/EPG%20PART%20IV.pdf
For me an OBX header will suit me just fine if I ever get the darned thing installed.