Holy crap... that was some good common sense smackin me in the face. I guess it continues to blow my mind the level of technical discussion in the Mini community. My wife drives a 2005 Mustang V-6, so on occasion I spend some time seeing what's going on in their forums, and let's just say there is truly no comparison to the level of intelligent discussion that NAM provides... which is often over my head.

Now, if this was a forum on the USAF, being a 2W151, or how to please a woman (pm for details ), I'd be playing the part of andy @ rosstech or Dr. Obnxs.

...but seriously, help me out!

 

We're thinking alike

 

I really don't see the stock cat as a "bottle neck". No doubt it is a back presure causing point but really how much? It was designed to handle the amount of gases the engine produces? And its size (length) as a % of the entire exhaust path is small. No doubt a larger cat would be less restrictive, just like increasing tubing diameter but its my layman understanding that a certain amount of back pressure is necessary to obtain a balanced exhaust system (i.e. hp & torque).

I installed the OBX header w/ the stock cat first to a 1-ball and later swapped out the 1-ball for the OBX exhaust. In both cases I found the car to rev free'er which I interpreted due to everything being less restrictive.

The difference I found between having the 1-ball and the OBX exhaust was that the OBX exhaust enhanced the top end.

These comments are all based of seat of pants driving and clearly I'm not one of the MINI-OBE-ONE-KANOBIES of the board. Perhaps one of them will chime in and educate on this matter.

 

Why doesnt somebody take it upon themselves to get these venders on here to give you there test data on there own headers and then you can compare them yourself than goin off of other peoples butt dyno's.

Cuz unless someone taking a bone stock S and starts swappin headers of different companies to run dyno's on, none of the info given is gonna be accurate with all the different combonations of mods than can be done to our cars.. For the prices seen with most of the knock-offs out these days, anyone will do over stock.

 

1 Nm = 0.738 lb-ft
1 kW = 1.34 HP

HP = lb-ft * RPM / 5252

 

i would agree but i would rather the restriction/back pressure come via the pipe diameter and not the cat!....also how much back pressure is needed, anybody know this!?!?!?

so has anybody on here question these vendors on their test data/(Hp #'s) ??
*g00d point 1FSTMINI **but do u really believe this "For the prices seen with most of the knock-offs out these days, anyone will do over stock"........well i guess it could be to an extent

 

Thanks Andy... do you mind checking my math?

First run at 28 C (82.4 F) before the OBX header was installed, the 2003 MCS had " 56,5mm pully, mth ecu, beru spakplugs, k+n CAI and remus exhaust."
It put 225.33 hp (I presume to the crank... ) and 184.02 lb. ft.

Second run at 56 C (132.8 degrees F?? in Germany? I'm guessing these temps were not ambient outside, but perhaps under hood?)
It put 226 hp and 194 lb. ft.

So the OBX added 10 lb. ft and approx 1 hp (yes, I know, higher temps on 2nd run, so apples to apples, better than that really.)

 

I don't put any faith whatsoever in dynos that claim to show power at the crank. To show how nonsensical their "coast down" calculations are, check out the first post in this thread. The same car, on the same dyno, showed a "drivetrain loss" of 38.7 kW (51.9 hp) on one run, then 32.9 kW (44.1 hp) on another run. Does a header change the relationship between bhp and whp? Of course not.

Luckily, these graphs show the actual power at the wheels, which is 124.3 kW (166.6 whp) with the stock header and 125.0 kW (167.5 whp) with the OBX header. Looks like just under 1 whp gain to me and both those figures look reasonable for a MCS with the stated mods.

 

Ok... so the numbers I was looking on the chart was indeed the dyno's estimations of crank hp right? And the numbers you listed here are what it measured at the wheels. What is your take on the ambient temp listed? Underhood temps?

 

We measure the power usualy at the crank in europe.
The temps are degrees F and measured in the closed room where the dyno stand.
The OBX with stock cat brings the most gain (about 10 NM) in the middle rpm range between 3000 and 5000 rpm.
Tomorrow we get a power quote of an highly modified CooperS with the OBX and an 100 cell metalic racing cat.
Beside the original Supersprint, the OBX is the best designed header for the CooperS on the market.
In january i will do some testing with the obx and no cat at all but with modified ecu (espacialy insensitive bank 2, to get no engine light)
I´ll keep you informed.

 

So if you dont use the cat you will throw a CEL? Where can i get a O2 sim?

 

So using Andy's math thats 7.83 added pounds of torque between 3000 and 5000 rpm. :smile: What exhaust was affixed to the OBX header and stock Cat?

Can you go into more detail why you think the Supersprint / OBX is the best header for a MCS? are you comparing these two to other 4-2-1 designs or 4-1 design?

 

You dont need a O2 sim, you have to change the sensitivity of bank2 in the ECU.
I you use MTH, Franz can do that for you.

 

Even better.....I have the MTH flash as well.....TY

 

Do yourself a favor and download this calculator from Microsoft, it's free and convert all metric to Std. for anything you can imagine.
http://www.microsoft.com/downloads/d...DisplayLang=en

 

Had my local shop install the OBX header yesterday (including welding on the stock cat), and the difference is phenomenal.

The throttle feels crisper and lighter - where there seemed to be significant "drag" in first gear past 2800 RPM, now it begins around 5300 RPM, making first gear much more suitable for street driving. The sound is definitely much deeper and throatier when the throttle is open past 4000 RPM, but not to the point of being too loud or obnoxious. Exhaust burbles sound warmer and less metallic. Finally, there is a perceived gain in torque through the entire powerband. Overall, it was worth the $350 in parts and labour for me, if only in the perception of more power and better sound. No dynos to back up any of this, unfortunately.

The OBX header was certainly a more cost-effective solution than the competition, but only time will tell whether or not it was a wise choice for me. My shop informs me that the joint on the header is likely to become loose over time and begin to leak, requiring tightening every so often. On the other hand, I would not have upgraded the header if the OBX hadn't been so affordable compared to the Supersprint, Milltek, etc.

 

my sentiments the same. I felt it complented the torque curve as well and that OBX opened the door for many of us to try the header do to pricing.

I found that when I changed to a free'er flowing exhaust the header was even sweeter .

 

i used the stock cat and had it cut. but it's diameter where it has to meet the header is still smaller than the obx diameter so it could hang together to the drive to the muffler shop. but the muffler shop had the cat weld to the header with some of the smaller diameter of the cat in the bigger obx pipe... so my question is that would it cost any flow problems?

 

After breaking-in the OBX header and allowing the ECU to adjust, I'm getting 3 MPG more than before. Driving a 100-mile round-trip route that I take quite often with similar pre-OBX driving habits, my mileage increased from 22 MPG to 25 MPG. I can only attribute that to better breathing. So far, I'm loving this! My only regret is not having had this done sooner.

 

I also have the stock Cat.

I had placed the obx piece against the Cat and drew a circle on the cat where the piece touched and cut it there so I did not go down in diameter from the OBX piece diameter.

The cat itself is restrictive compared to no cat or a high flow cat but I am delighted with the results and can't imagine that using a high flow cat would give "a lot more" (yes some small percentage more but not worth the extra $ to me).

From the cat I'm running the stock 2.25 pipe to the OBX exhaust.

 

Anything new from you who've had the OBX on for a while?

 

Bolted on, heat sheilds in place, you wouldn't know its there by looking...

Matt

 

Wish I had done it sooner! No problems whatsoever.

 

Cool, thanks Not so much worried about problems, although that IS good to hear! One member I heard from said that his doughnut gasket failed, but he said he was running it hard on the track.

My main interest is even more OBX-Racing Header Dyno Results!

Some time has passed since the thread was active, & I figured a few folks might've dyno'd their cars since - hopefully a baseline, then OBX dyno. Would love to see delta/graphs of a late 05/early 06.

Also:
I've seen at least 2 ways of attaching to the OE cat - ball/socket & flex joint. Several related questions:

Wondering if the folks using flex-joints are using the OE or something aftermarket? I believe the OE is 2.25 I/D but the OBX is (supposed to be?) 2.5 pre-cat. Is there any concern of the OE flex-joint being restrictive?

Those using a flex-joint... how/where have you incorporated it? what length? bungs etc?

 

I'm using the ball / socket - I had a mechanic do the install and he says that it is important not to over tighten. He used copper nuts instead of the OBX nuts because he said they never come lose.

This is the easiest route, you can always change if it fails.