So to start, I'm plotting out my exhaust setup currently and I'm pretty sure I'm going with the Invidia catback. For headers I'm a little more undecided because I see the Megan Racing ones with the test pipe on waymotorworks for only $199 and I have seen other people using them. But on the other hand, outmotoring has the Milltek set with the high flow cat and they run for over $1200.

So my question actually is, what is the reason for the Milltek being so much more expensive? Or is the Megan Racing set actually not that good of quality? Has anyone else paired either of these with the Invidia setup and what was the result? Also, if anyone has any other headers they would recommend for the setup that would be great too.

Money isn't the factor here. I can save up and get the Milltek if I wanted, it's more of just questioning if one set is overpriced or the other is just low quality.

 

Well bad news is the Megan is out right now. There are none in the world as the factory messed up the jig and has to make a new jig before they will even be producing any. So my best guess it will be months or longer before those are available.

The Milltek Header is a good header as we just installed one last week on a cabrio. It has a cat and is a much higher quality part than the Megan.

Another option we offer is our Flashpoint header. It's similar to the Milltek, just a much better price tag. The quality of it is great also as it is all nice tig welds, a high flow cat, and polished finish.

 

I've been wondering why the megan is out everywhere. Good to know! Silly Question tho, stock exhaust with a header or frowned upon? Sorry I'm an exhaust newb I s'pose.

 

The quality and welds of the Megan headers are quite poor, I have seen the welds crack on them at the flange. The price is a dead giveaway of the quality. The RMW headers fittment is perfect, top notch product, milltek is right there with them. Just make sure your lower torque mount is in good shape, excessive engine movement puts unnecessary strain on the welds. Hope that helps you decision.

Stay away from the Megan's, they are cheap for a reason...

 

On a mildly modded Mini (pulley, exhaust, CAI)....what kind power gains are usually seen with swapping the oem header to an aftermarket one? I'm thinking about doing this also....just don't know if the money justifies the gains.

 

Just dyno tuned my car by Jan/RMW. My car has 17% pulley kit with belt and colder plugs, Milltek cat back, DDM CAI & Intercooler diverter. Stock headers. Saw other cars with aftermarket headers (Milltek, RMW, Megan) get tuned with same setup as me and they all made less torque on the dyno. Like nearly 8-10% less. From what I observed and have been told headers are pointless unless you're doing an upgraded head (mine is stock), and cam upgrade. Big $$$...

 

I also added 450cc injectors when I had my car tuned. It's like a totally new car now!!

 

Look at the RMW shorty header! It's TIG welded stainless steel with equal length primaries and a high flow cat.

 

Mind me asking what your car dyno'd at? Did you do one with and without tune?

 

BUMP! I'm going to have almost the same setup, very curious.

 

Don't mind at all...didn't really do a pull pre-tune because I was running the car on stock injectors and right before tune dropped in a set of 450cc injectors which I got from Jan/RMW. I did a pull with all bolt on stuff with a map Jan uploaded from a similar setup and it pulled 198whp and 156 torque at the wheels on Helix' mustang dyno. My car was having boost issues (mostly creep at the top end) which proved to be due to a faulty MAP sensor and my pre-cat failing. Switched the MAP for a new one and Helix had a set of stock headers which I switched mine to. Creep issues were gone. End result was 205whp and 168 wheel torque. I used to own a tuning shop and have years of experience tuning other brands (mostly VW/Audi, Subarus and Mitsus) so I know the importance of a good tune and why after doing my research elected to go with Jan/RMW. It's not so much the end numbers that count but the smooth and linear power curve that the motor makes. Needless to say my tune was as smooth and linear to the point of perfection and now that I've been driving the car for the last few weeks on the tune and put about 800 miles on the car I have to say that the powerband is tremendous and the car pulls all the way to (the new and higher) redline. It idles smooth and highway MPG's are up a lot too. I've seen over 34mpg from the onboard computer whereas pre-tune on stock injectors (keeping in mind I was doing everything not to build boost beyond 7-8psi and short shifting all the time) I never saw more than 27mpg on the highway. Improvements all around and couldn't be happier!

 

on a jcw car, is there any benefits of getting an aftermarket header with no tune?
was simply wanting to punch the cat out but it seems the pre cat causes flow restrictions also
instead of destroying the cat and pre cat, i thought of buying low to mid priced headers just to replace these items

 

an aftermarket header will do better than the stock, they will have better ports, longer runners. and less bend per distance. which all equates to better flow. better flow more power =)


I noticed a difference when I replaced my stock header with a catless 4-2-1

 

I've heard that opening up the exhaust to much on a stock boost supercharger can actually result in less boost and less torque. I'm not sure how true that is but I've read it a few times and NYMADMINI says seems to back that up. He's got dyno time to prove it.

 

Tuning of manifolds (both intake and exhaust) relies on the proper combination of velocity (for inertia ramming effect) and managing pressure waves. They are interrelated. In a 4 cylinder, you try to eliminate exhaust interference tuning between cylinders by either running a very long 4-1 header or a 4-2-1 where 1 & 4 and 2 & 3 are paired. Interference tuning is when cylinder "A's" exhaust pressure wave hits cylinder "B's" exhaust port (at the valve) during the end of cylinder "B's" exhaust stroke. This disrupts cylinder B's exhaust scavenging and increases the exhaust residual fraction (aka "internal EGR") in the cylinder at the start of the intake stroke, costing power.

Also, when the exhaust gasses see a big step change in section area (such as exiting the head and going into a large diameter primary), this also creates a pressure wave, and a huge drop in gas velocity that can disrupt cylinder scavenging, especially at low rpm's. This is why large diameter primaries are a loser in the rpm range this engine was designed to operate in.

We tested different primary runner ID's when doing the S/C engine development. The original Rover header had 1.25" ID runners which were costing about 6HP and even costing a couple of HP on the R50 engine. It made less power than the cheap Chrysler cast iron manifold. Plus they were severely swaged down at the collector, making it even worse. When we ran 1.5" primaries, they made slightly less torque than 1.375" and no more power, even at 6800 rpm. We recommended that Rover change the header to 1.375" ID and redesign the collector. I can't remember if they did or not and haven't measured my car to determine. This effect was true even running a huge pulley ratio (very small pulley) and making 200HP with stock cam and production cats. Yes, "bigger isn't always better" when it comes to exhaust tuning.

So I'd estimate that unless you are trying to make >250 HP, primaries that are larger than 1.5" ID will cost you overall performance (area under the usable torque or power curves) and for a JCW type package (210HP), 1.5" ID primaries will not be better than 1.375" and might be slightly worse.

Now, if you're running a race set-up with ultralight retainers with higher load springs, and setting the rev limiter at 8000 rpm, that's a slightly different story, especially if you're racing the car and hardly ever going below 4500 rpm on the track.

I've yet to see an aftermarket header than I'd consider ideal for a stock engine or JCW type package. I'm still looking.

AFA boost effect, lower boost via better exhaust scavenging is a good thing, it means that the mass airflow through the engine is higher and the resulting lower boost will also produce lower inlet air temperatures. So a good flowing exhaust has a synergistic effect on the intake side.

 

Just wanted to point out people are saying good things about OBX headers for the R53s. Their build quality is apparently excellent, despite what the price would imply ($175 for ceramic coated mild steel, but most go for $250 stainless).

 

Thanks, seems like that's been pretty much the consensus over the last 9 years. Helix mentioned in a post last November that OBX changed the design of the primaries and made them more restrictive, but I can't find any hard numbers on that. Any idea what ID primaries and secondaries they are running now? I definitely prefer a well done 4-2-1 manifold over a 4-1, as they are more effective when overall primary runner length is limited by the vehicle package (as it is in the Mini and almost all rear exhaust 4 cyl. production vehicles), and they perform better in the RPM range that a street car will run. Interestingly, Rover groups first prototype manifolds were 4-2-1 and we had that modeled to produce some nice numbers. In the end, it was just too expensive (had pre-cats at both 1st Y locations) and cat light off times too long for emissions certification.


I will probably end up with the OBX 4-2-1, and production main cat welded in, although I've seen some posts of people showing a 4-1 and calling it an OBX, which is a bit confusing, since OBX doesn't have a 4-1 shown on their website for the Mini. I'm only looking for about 220 BHP with mildly ported BV head, "DaveF type" airbox, header, 17% pulley, 380 cc injectors and maybe (still not decided) a street grind cam and maybe an upgraded Intercooler. Don't think much more than that is of much use without an LSD. Definitely going for the sleeper R52.


AFA the Megan header. The pictures I've seen of the flange, runners and collector look very good and compatible with a mildly ported head and it's very tempting to go with this as splicing in the production Cat should be easier than the OBX. However, the flex joint looks very short with likely insufficient convolutes for durability. IOW's, I expect that the flex joint doesn't last long.


The "donut style" of the OBX is a bit old school and was common in production vehicles 15-20+ years ago. The typical problem with those are leaks and squeaks. But replacement seals are cheap.

 

I don't know the sizes, and won't be getting my OBX header until they are back in stock. Apparently this is OBX's most popular product, so hopefully it won't take long.

Consider getting an LSD. I ordered my car with one, and I'm pretty sure that's part of what makes my R52 behave so much better than most front wheel drive cars, under acceleration anyway.

I intend to put my stock catalytic converter in the OBX, as well. There is apparently plenty of room to widen the inlet and outlet of the stock piece to match the header's outlet.

I also found the old school donut connection a bit odd. They will be squeaky someday, but they will still just be squeaky long after a cheap flex joint has withered and died. If it gives me any trouble, I'll probably weld in a very good quality flex joint with an interlock liner. I've used Vibrant's flex joints before. They are beautiful. See them at Verocious Motorsports. I don't really anticipate trouble from the donut/toilet bowl connector.

I would love to be building my own header and exhaust system, but I'm just not quite set up to do that well. With these being as cheap and, reportedly, as high quality as they are, I can't justify the trouble of building one.

 

where can i get obx headers from?
i have tried to find and even emailed obc but no reply