Most liked posts in thread: Upgrading the TSW R53 MINI Cooper S

Well, theirs yer problem...

We've figured out that the exhaust system has too much back pressure, but we didn't know exactly where the problem was (although I suspected the welded-six-times OEM header-precat-cat assembly).

So, it was time to experiment.



I added taps to the exhaust system, one in front of the cat packs, and one behind.



These are connected to a couple of high-quality pressure gauges through 1/8" soft copper tubing.



So, we have pressure readings both upstream and downstream of the catalytic converter and pre-cat.

The results? At 4000 RPM and WOT, the upstream pressure was 11 PSIG, and the downstream pressure was 1 PSIG. At 7000 RPM WOT, the upstream pressure was 21 PSIG :eek6::crazy::frown2:. The downstream pressure was 1.5 PSIG. For reference, I have seen about 3-5 PSIG at the collector with 4-into-1 headers on other 4-cylinder engines.

So, the pre-cat and catalytic converter are bad. It doesn't matter which one is hosed (or both) because I would definitely replace the whole shebang at once.

 

Ha, yes, small world.

I did replace the cat (and deleted the pre-cat in the process). Before the work, the difference in pressure before and after the cats was more than 20psi - really awful. Afterwards, the difference was about 3 psi. Now that's more like it. I have not been back to the dyno again, so no new numbers to report. The car was immediately faster (not to mention happier) after the repair, though.

 

Late replies!

Scottinbend - I replaced the cat with a cheapie placeholder purchased from Summit for about $90.00. It got me through a smog test and about 14 months of driving before it went south. Right now, the car throws the "Cat low efficiency" code when the outside temperature drops below 30F.

00zero - no, not that I could tell, the exhaust noise volume was about the same after removing the pre-cat guts.

The original header and cat combo is, by now, a glob-o'-weld, really ugly and now unable to perform its function. I'm sure it would soon crack open again if I left it on the car. Fortunately, I spent the last year saving my pennies and being a good boy.

I'm now installing a new Mynes V2 header and refitting an OEM cat (also supplied by Mynes). Pictures to follow a few days from now.

 

Mynes V2 header, and a couple of extras

As mentioned earlier, I got a new V2 header set from Mynes, along with a ready-to-install OEM cat. Also on the to-do list were a fuel filter and to find an oil leak on the right side of the engine (with the pulley end being the front).




I first cleaned up the garage and put the car up on jack stands.




Since I dropped the subframe (to get a clear view of the oil leak, and to make everything from oil clean-up to header installation much easier), the nose also had to come off. Shown here are the lightweight, hidden links that connect the front of the splitter to the car. You can read more about the splitter here.




The subframe was pretty nasty, so I pulled it outside and cleaned it up.




The oil leak was coming from the oil pressure switch. There was even oil in the sealed connector. Oil was everywhere! I replaced the switch, of course.




Next on the list was the fuel filter. I followed [ame="http://www.lonestarminiclub.com/forums/showthread.php?p=4062#post4062"]k-huevo's how-to [/ame]for this job. It's pretty straightforward.


New filter on top, nasty old filter on bottom. The old filter had 88K miles.


The Mynes V2 headers are really nice. I wrapped them up with a tad less than 50 feet of header wrap ("Titanium" wrap from DEI). I have read a lot of conflicting reports on whether or not header wraps kill headers. For instance, Stahl headers is dead-set against it, although this is for mild steel headers. Many aircraft headers are wrapped. Wrapping stainless steel headers seems to be less controversial. Mike at Mynes thinks it's not a problem (and plans to do the headers on his MINI with the same product). In the end, I decided to go for it.


I wanted to put the head shield back into place, and I'm not worried about keeping the shield original. So, mark...




...and cut. This cut allows the shield to fit perfectly around the new headers.




I did have a problem with the fit to the Magnaflow cat-back. The cat-back has never fit quite right, and with the Mynes parts, the fit was just a bit too bad to live with. I blame the Magnaflow parts - the Mynes parts look great. I think it's a tolerance stack-up issue. Nothing I can't fit with a welder and a Sawsall.




After tacking the flange on the cat-back resonator, I pulled the system out and did a proper welding job, inside and out. I also smoothed down the internal weld. This also joined the inner and outer tubing of the Magnaflow at that point, so the result should be a strong, trouble-free joint.

Driving impressions will have to wait until the bad weather goes away - hopefully sometime next week.

 

After more research, I decided to chicken out and pull the wrap back off. It doesn't seem like a good fit for a MINI that sees more highway driving than anything else.



MINIs tend to run with high EGTs, and the problems encountered after wrapping run from reduced header life to burned-out cat converters. Also, the high exhaust temps tend to kill even the high-tech lava rock product, with reports of wrap found in tatters and baked to a crisp.



Lower underhood temps are apparently the only verified performance gain. I can't afford to replace the exhaust system every 1 to 2 years, so the wrap experiment is cancelled, so to speak.

 

Yes, Mike doesn't seem worried about it, but after reading up, I came back to the same opinion (only that) that I had ten years ago about header wrap. I can't afford to see what happens. Hell, it took me a solid year to save up to pay for these headers.