This info may also effect other header brands. It's well worth a check on that high dollar aftermarket header you just bought.

I bought a Milltek header while it was/is on sale at ECSTuning.
NOTE - this is info has nothing negative to do with ECSTuning.

Some of you may have read my other post about the stock header flange size vs the cylinder head exhaust port opening size. A quick summery, the header port dimensions fit the "stock"...cylinder head exhaust port nicely. However, the "ported" JCW exhaust port is "larger" than the stock header flange, in width and most likely the height also. This produces a dam/wall, or otherwise restriction that mostly negates the cool JCW porting that we/someone paid for.
https://www.northamericanmotoring.co...t-porting.html

The Milltek...header flange... has the SAME problem. While the primary tube is slightly larger than the OEM header tube (a good thing), the flange is virtually the same opening dimensions as the OEM header flange... which means it has the same negative overhang as the stock header.!? What the hell ?

All this is to say, if you buy a fancy, aftermarket header, you might be well advised to look/measure your exhaust port opening closely (JCW or other ported cylinder head) and to open the new header flange to match (or make slightly larger if possible) the exhaust port opening dimensions in your particular header.
Otherwise, the main reason for buying that aftermarket header, will be for VERY minimum gain, OR...not fully as designed.

NOTE - IF POSSIBLE DO NOT MAKE THE FLANGE OPENING INTO A FUNNEL or TAPERED. AS LONG AS YOU DO NOT CUT INTO THE PRIMARY TUBE, GRIND STRAIGHT (90 DEGREES) FROM THE FLANGE. ONLY TAPER IF THE TUBE IS IN THE WAY OF A CLEAN OPENING.
DO NOT GRIND INTO THE WELD.

NOTE - The "flat" floor is fine (no need to make it round) as is, as long as it does NOT overhang into the cylinder head port.

Mike

 

I enjoy this inclusion thoroughly.

Thanks for the into on the headers!

 

or just buy a Maniflow header

http://www.maniflow.co.uk/index.php?...9&product=1625

 

OCR, yes, you and I were talking in that other thread about the head port size vs the header flange port size...... I also agree that the stock header on my JCW engine is also a bit smaller than the port on the head. I probably could have opened up the header flange a bit, but I already installed the new engine and forgot all about it

Bryan

 

ExclusiveWorkships -
Nice stuff actually, but the header has two problems and one unknown.
1. Carbon steel, not stainless construction.
2. No expansion joint. This is a driver, not a race car. Don't want to be constantly replacing blown out gaskets.
3. Unknown, there's no picture or "any" information about the tube sizes, or the flange opening size in their website.

Though, their "cat-back" exhaust does look very nicely done, better than most (my opinion, according to the photos!)...but again, too much maintenance being made of carbon steel. I'm old enough to remember carbon steel exhaust. But I've been spoiled by today's Stainless exhaust.

A383Wing -
Ah...too bad.
I got the back side exhaust (also Milltek) on. It does fit nicely, the mufflers tucked way up out of the air stream, the pipe tips fit well in the cutout of the bumper cover. I DO NOT like the "Y" pipe tube size or its actual "Y" section where and how it's welded together. The Mini (JCW) guys did a much better job in regards to that part of the design. We'll see how things work out. It's still MUCH better than the crushed main tube on the Mini exhaust. I think the Milltek is a bit lighter also.
I'll wait to put the header on till I can get it squared away as best as possible.
I have cylinder head work I have to finish for other people before I can spend too much time on my personal toys.

I know, it's not a race car, but when I fork out money for over priced parts, they at least should be better designed and assembled.

Mike

 

It seems like MINI put at least a little thought into "crushing" the pipe on the revised exhausts since the width seems wider in that section than if the pipe was simply crushed. It would be interesting to know how the difference in area between a round section and this expanded section or if the shape of the walls have any negative effect on the exhaust flow due to turbulence.

What I really like about the Milltek is how the smaller mufflers tuck up behind the bumper instead of hanging below with the JCW.

 

RB-MINI -

And just how far does that work ?
If the diameter, now thickness is squeezed to...say .25", and the width is out to...3.0" that still has the same flow characteristics ?
Or...if the thickness is now really squeezed to... .06" thick and the width is 3.50", the flow characteristics are the same as a 2.50" dia. tube ?
We "could" go one step farther..!
Somehow, I don't think it works like that..!

I'll measure the area in question and report the square inches, before and after.

Mike

 

i don’t know, but they didn’t squeeze it to those extremes. I also didn’t say total area was the only thing that affects the exhaust flow with pipe shape making no difference. Hopefully someone knowledgeable in fluid dynamics could clear things up.

 

RB -

Funny...I was using those numbers as a "what if"..! Sorry you didn't get that. You still need to understand...where is that point of no-return in your "flattening" comments ? My above examples above point that out.

You need some more real world experience, and understanding. Fluid Dynamics...good one. They should be capital letters if you are going to bring something like this up.

And for the record, Yea, I am (well was, retired) a Mechanical Engineer, with may years of various application testing. I also have MANY hours (about 35 years worth of weekend work) porting cylinder heads and intake manifolds (some exhaust manifolds) with similar hours at the flow bench...testing those shapes. So yes. I do have some idea what works and what doesn't.

Pinched passages...don't flow well..! It's that simple, period.

Mike

P.s - Still looking for a Mini cylinder head so I can learn it's limits if anyone has a bad/junk head they are willing to part with.

 

Why do you think you'll be getting blown out gaskets?

The other vendors don't talk much about tube or flange size for other commonly sold manifolds,

These make the default in mild steel, but this is slightly more flexible and mild steel tends to have a nice lower tone about it, however they will make a stainless one up for you and a custom spec for pipe diameter is also possible, I've got two. Some things for, or on tuned cars don't always get discussed or advertised for the benefit of others wanting to copy, or benefit from them on the track but you can contact them and say what you're looking for, at least you know you're talking to people who've been making competitive exhausts for decades, but they'd make changes you ask for ;O)

As far as that little bit of squashed pipe is concerned it has no negative effect. It doesn't harm the 200chp or 210chp and still the 218chp JCW cars does it? These Mini's don't like a wide open exhaust anyway. A Miltek may make more noise in comparison, but noise isn't power and if I used one or if mine was any more open it'd fail the track noise tests, it may be ok if it has a cat, however I choose to use mine without at present but did have Maniflow make me one. If that little squashed bit is having any effect it's likely positive, helping with a small amount of back pressure maybe helping the cylinders fill. People can make what they want of it, I know what my car makes and that little bit costs me nothing I know, and I doubt it'll likely stop me taking it a touch further but then the software will be at the limit and I'll have done all I wanted, then proven parts get moved to the other car and my turbo kit and other stuff go on instead ;O)

There must be a stack of dead heads on ebay for you to chop about, the good ones are going up though.

 

ExclusiveWorkshops wrote -
Why do you think you'll be getting blown out gaskets?

What ? I never said anything about blown gaskets..! What are you smoking ?

And
As far as that little bit of squashed pipe is concerned it has no negative effect.

Again, funny statement with apparently zero remembrance of your high school Physics class.
When a tube is squeezed in about half...flow WILL be cut. Plain and simple.

And finally -
The other vendors don't talk much about tube or flange size for other commonly sold manifolds,

Many DO in fact mention both primary and collector tube sizes..!

Mike

 

Err...you did in post 5 item number 2?

I'm not so interested in science over this pipe thing, I'm no scientist but what I do know, is the pipe is not squeezed in half, it has a small flattened section near the rear of the centre pipe, and there are many users of this JCW 'squashed' pipe system including those with significant power enhancements likely unaffected by it. I believe you'd need to demonstrate the effect of it's replacement before and after for anyone to take much notice. Otherwise readers will be having sections of pipe replaced when it's not likely to benefit them at their stage of tune anyway, if ever.

Regarding the manifold/ports, this is useful to those unaware but I'd urge anyone reading to hold fire if tempted to alter a part still under guarantee. I hope they have a 'before' dyno report too, before they start on their manifold or there won't be any record of a gain if expected, although I expect it's worth getting right if people know about it I doubt it'll change much as the exhaust gas will still get pushed out adequately and won't cause a huge loss on the average car, and like above, if anyone believes it's a restriction for a performance car, a before and after dyno report in the same conditions is what proves it.

If some vendors quote pipe length and diameter it's more useful info, but the majority buying most of these aftermarket manifolds are interested in shiny, or at least stainless steel, or buying because they're copying someone else, and of course if a potential power figure they might gain is quoted, because some will believe it ;O)

Obviously I don't know what you car makes or is likely to, but mine on the rollers I use is either 233 or 235whp despite a JCW exhaust with it's little flat section. I suspect the only thing that would change from having it opened up is the tone of the exhaust very slightly.

 

ExclusiveWorkshops wrote -

I'm not so interested in science over this pipe thing, I'm no scientist but what I do know, is the pipe is not squeezed in half, it has a small flattened section

Incorrect comment. And it's "obvious" you aren't interested in science, OR detail. Maybe...you should look into that situation..!
As for the JCW exhaust it IS squeezed (about) in half. I've never given exact numbers..! But I'll go out and get exact measurements later today.
And yes, you maybe should go back to your science class's..!

If some vendors quote pipe length and diameter it's more useful info, but the majority buying most of these aftermarket manifolds are interested in shiny, or at least stainless steel, or buying because they're copying someone else, and of course if a potential power figure they might gain is quoted, because some will believe it ;O)

Sorry, me, I like performance well over "pretty..! And also, a bad design vs. warranty...again, I'll fix the performance end, and any warranty problems myself also.

Obviously I don't know what you car makes or is likely to, but mine on the rollers I use is either 233 or 235whp despite a JCW exhaust with it's little flat section. I suspect the only thing that would change from having it opened up is the tone of the exhaust very slightly.

Obviously...!?
And just HOW do you know that my car hasn't been on a dyno ? Are you clairvoyant or something. You hiding someplace in my yard ?
And you somewhat obviously don't know a lot of what it takes to make power..! You ever stop to think...MAYBE, your engine would make even MORE power if you paid better attention to the details...science (that you seemed to have missed in school)..!?
An exhaust header flange/tube that is smaller than the cylinder head port...is comically useless. No real Designer/Engineer would ever stoop that low to design/build a backed-up exhaust system like this. WHY...would one open an exhaust port, just to plug it with the header ? Makes NO sense.

You can continue to skimp on the engineering details on your car(s) all you want, I won't on mine. Never have, never will.
I've been involved with many forms of racing (cars, boats and motorcycles) since the mid 60's. Both my own vehicles and helping others. Internal combustion engine science is the same across the board. My American engine experience transfers over to the Mini engine just fine.
So does my attention to detail.

Mike

 

 

Dave O.

Mostly agree.
Both the MillTek back half and the header are, for the most part (except for the "Y" in the back !?) are assembled (fitted and welded) in what I would call a very good quality. The fitup and welding are done very nicely. There was no problem attaching the back half to my car (fit wise).
The header collector is in my opinion...junk, torque/power wise, but...it's better than the OEM header collector. THAT was my thinking.
The Milltec flange...WHAT WERE THEY THINKING ? A PROPER fit to the JCW exhaust port size, would have been a VERY good/intelligent move on their part. It would not have negatively effected any other combination if it FIT the JCW head.

Agreed, the RMW header (seems to be...in pictures) is a nicely designed part. But you pay for it. If I were racing, or this was a weekend "fun car"...yea, I would have forked out the much higher price. Most of my money is going into 3 other "old" cars I'm putting together and one motorcycle I need to finish..! Money wise, I probably shouldn't have even bought the Milltec stuff in the first place..! Oh well.

Mike

P.s. - If the RMW Shorty Header ever goes on sale...!

 

Do you have any pics of your Milltek manifold showing the issue - is it possible to modify the flange or is the Milltek substandard on a fully ported head?

 

I think this will be in my future. I have an 06 JCW that needed a new cat and flex pipe so I bought the miltek and bolted in with the rest of my factory JCW exhaust. Been battling one exhaust leak after another, had it good for about a month and now have the sound of a new exhaust leak but sounds to be coming from the head/manifold area. While under it I cannot see or hear any leaks with a stethoscope, but can hear it up toward the head. Manifold bolts have been checked and are tight, wondering if the gasket has given out already, about 6 months and maybe 3500 miles, and also just realized this size issue could be an issue. I will have to take it back out and look to see if it is in fact a smaller inlet than the head and get to grinding to open it up.