Hi JCW community. My first post on here, just had a question. I was planning on changing my headers for my 2004 JCW MCS. I heard that the 4-1 headers really strangle the engine (is this true?). I know that the 4-2-1 headers are good for mid range power and torque, and since it's pretty rare that I redline, I was thinking of swapping to it. I need some help one what things to change and what parts I would need. I was thinking Xforce headers with the JCW exhaust system I have would be pretty good. If anyone has any info, it would be great.

 

Now that's a first that I've ever heard, 4 into 1 headers...strangle...an engine.
I'd bet that 99% of the true exhaust headers on cars or in the shops waiting to be bought, are of the...4 into 1 design !
Yes, there ARE...VERY bad designed 4 into 1 header designs. The ones with a VERY short collector, yes, are not very good at making power. A collector in the neighborhood of 6" to 8" is much preferable to the 2" or 3" long collector in some designs.

Yes, the 4 into 2 into 1 are also a good design, but cost more and are worth only a small amount in HP over the more common, (longer collector !) 4 into 1 . They also take up more room to build...properly.
For your Mini, that you "rarely" run to redline, if you can get them cheap, yeah, go for it, but don't be too concerned about loosing 2 or 3 HP by staying with the more conventional 4 into 1 header.

A MUCH, bigger problem in my mind, is the mismatch between the JCW, enlarged exhaust port...and the SMALLER, header that comes on ALL Mini's !
Get out your grinder, and measure the cylinder heads exhaust port dimensions, and make the header..."match" the exhaust port, or slightly larger.
Having this step going from the port to the header is MUCH worse than than any but the worst design 4 into 1 header.
I've found that even most (NOT ALL, but most) aftermarket headers...also...have the smaller opening in the header flange, vs. the larger port in the JCW head.
Buyer beware !

Mike

 

Agree with OCR and the other best bang for the buck is to modify the stock header to eliminate the pre cat and that gets you the same gains as the expensive aftermarket stuff.

 

I agree with Mike (OCR), but do check your exhaust gaskets also. The JCW head has slightly larger exhaust ports, and I have seen exhaust (header) gaskets that were slightly smaller than the JCW ports, creating their own restriction. As long as the gasket is larger than the port, you can hang it on the header bolts (both on head & on header to use it as a reference to transfer & mark the stock header flange for enlarging as Mike described.

With factory head, cam & injectors, enlarging the stock header flange is worth the same 10hp that an inexpensive aftermarket header will provide. However, the stock header rapidly becomes the limiting factor when you add a cam and maybe a big-valve head, and spin it past 7000 RPM.

As far as 4-1 vs. 4-2-1, the RMW shorty header (with cat) and their race header are widely acknowledged to be among the best performers on a R53 Mini, and both are 4 into 1 designs.

 

I heard the RMW Headers are the best for R53, I have a modified R52S, and I'm considering those, but with the recent law change I need a CARB compliant exhaust for NY State emissions.

I was thinking of reaching out to RMW and or Racing Dynamics, and seeing if they'd weld in a 3rd party CARB compliant CAT for me, or maybe cut my original Mini CAT out and weld that in . The Racing Dynamics header has no cat option with the O2 sensor fittings.

Anyone else go down this road?

 

Any reason for two duplicate threads on the same subject? https://www.northamericanmotoring.co...-2004-jcw.html

 

Unsure where RMW has their headers produced but seems unlikely to me "in-house". From my experience with headers on various cars going back to my very first new car (1968 Camaro SS350) on which I installed Hooker equal length headers for bracket racing (yes, I'm an old guy) to JBA shorty headers installed on former from-new 1991 Mustang GT 5.0 and 1992 Big Bronco 5.8, I'll state that fitment issues compared to OEM manifolds can often result. With aftermarket performance parts, no "free lunch" with 1st Gen MINI being no different. My (sig) R53 has 4-1 headers with high flow cat installed at same time in early 2006 as other performance mods (unknown mfr, however likely sourced from Europe at that time). Several pics of that posted in my topic but if I was shopping headers at this point, pretty sure I'd choose Milltek's SSXM460 product. Why? Milltek has been making those a long time with welding jigs possibly producing more uniform fitment clearance than lower volume manufacturers for the W11 engine application. Unknown to me whether Milltek's flange ports are properly sized for the OEM JCW or subsequently ported cylinder head.

Here in AZ, periodic emissions testing is a requirement depending on county location. In mine, no testing is required but in Maricopa County (Phoenix and adjacent) is required - including passing emissions test prior to used cars changing ownership. The prior original owner of mine wasn't aware not required for me, so he had the car tested successfully the morning before I drove down to buy it with that "PASS" certificate furnished to me. So a question on compliance might be; pass emissions test only or that plus visual inspection required in your locale? Seems unlikely most inspection stations would put the car on a lift to check underneath nor do a close visual inspection within the engine bay for OEM equipment compliance. Happy I no longer live in SoCal or other areas subject to such scrutiny!

 

Yes the fitment issues I do worry about, everything in my Mini is a tight fit, and I don't look forward to struggling underneath the car. I was also considering upgrading to the Milltek Catback High Flow exhaust for that reason.
In terms of Emissions in NY State, they just upgraded them in 2023 to comply with California. I don't know if the mechanics doing the inspection are going to look at the part numbers on the Cat is I upgrade, especially if it passes the OEM emissions. So I may just be overthinking it. But it is my semi-daily driver. I'll keep you posted.

 

Thats because they are sized correctly.

Most of the 4-1 systems you can find for the R53 are really badly sized. Build quality may be good but the collector on most of them is super short & theres almost zero blending of the 4 pipes into 1, they are just cut off with a shaped wrap around that is lucky to be 1.5" long.

If you want a 4-1 header on your mini the RMW is the only ive yet seen with decent dimensions.

I have the XForce header here, its basically a copy of the Supersprint system. The main & the secondarys are not ideal, they both could do to be longer. the build quality is good but the manifold requires careful matching, its nowhere close to perfect out of the box, & without access to an actual cylinder head its a right PITA.

The supersprint system, or any of its clones - OBX, XForce, are probably your best pick for a road driven mini. The Janspeed & Milltek ones will work better than the stock item but they simply are not sized right.

 

I've actually used the Milltek Race header, and then weld your stock cat into the pipe that comes with it. No lights and you have a cat still.
https://www.waymotorworks.com/millte...0-r52-r53.html