There have been some recent discussions pertaining to the HP gains of aftermarket exhaust gains AFTER a pulley and/or ECU upgrade. In short, the HP gains for a car with a pulley and/or ECU are minimal over a stock exhaust. The fact that the HP numbers are better tells me that they must flow better (be less restrictive) than the stock exhaust. If that is correct, then why not test the least restrictive exhaust...no exhaust. Has anyone dynoed their car without the exhaust? (I'm talking about cat. back)

 

Check out this months European Car Magazine - Project Street S MINI Part 2. Dyno of two popular exhaust upgrades resulted in a max HP gain of under 3HP at 4,100 and an actual decrease of about 1HP at 6,100 RPM. Intake replacement resulted in 6HP increase across the range.

So, unless you just want the sound and looks of an exhause, stick with stock. Replace the intake which is relatively cheap.

I have 15% pulley and evoTech ECU upgrade - works well and is cost effecient (30 HP for $1100). Next most cost effecient is intake (6 HP for $250). Exhaust is way down the list if at all (+3 to -1 HP at $850).

 

Hey James, when did you get a pulley and ECU!!?

FYI, the Euro car mag article is speculated to be quasi-sponsored by BMP, and adjusted to make it look like the Supersprint exhaust has as much gain (or not, in their article) as the Magnaflow. The Magnaflow exhaust is THE most dyno tested exhaust for the MINI, and it's rock-solid common to get between 9 to 13 HP peak from the exhaust alone, of course depending on other mods (more mods, less gain, duh!)

Back to the question: No exhaust may be the least restrictive, but that doesn't make it optimal! Internal combustion engines (ok, those that are naturally aspirated or supercharged) NEED a certain level of backpressure to function at maximum efficiency. This is why a "race muffler" will create more power than an open header! Too much restriction (and typically less noise) like the MCS's stock exhaust, and you "choke" the engine, not allowing it to pump air like it needs to make power. Make sense? (whew, I hope so!)

Good luck, and Cheers,
Ryan

 

Another member here on MCO and I both have the same pulley and intake. I have the Magnaflow exhaust. We were both dynoed at the same facility on different days and he actually made a few ~ 7hp more than me. I don't have the exact numbers at the moment but I can post the difference in torque and h.p. if anyone is interested.
I don't know If I just got a "weaker" Mini S or if the Magna actually made me lose power. I would have been interesting to dyno my car with the stock exhaust also to see I my vehicle is just "weaker", but that wasn't done. Anyone else see this phenomenon?...
I'm not that disappointed with the numbers that were generated, cause the sound of those duel trumpets is music to my ears. Ok perhaps a little disappointed.

 

I've got the BMP intake, pully and ECU upgrade from Evotech. Exhaust is stock. The pully and ECU were done at Renntech during the Florida Pully Party. Right after the install(s) my car dyno'd at 172.9 HP and 159.9 Torque. All with stock exhaust. Never got a "before" dyno. The cars with exhaust were making more power, but not much more. At least the ones I saw.

I'm currently inclined to stay with the more subtle modifications. The sounds of the supercharger with the pully and intake are great. I don't have any need for the extra noise - especially with a dollar per HP increase that makes it questionable value for HP results. If you like the sound great - it's just not for me.

 

Ryan,

Yes, Randy Webb's tuning - Alta pulley and MTH (evotech, I think) ECU - I've only drive the combined upgrade a few miles, but so far both provide a meaningful difference. I drove the pully-only upgrade for a few days, now have both. [the guy in Germany did not show last Sunday to send the modified software back, so I had to send the ECU to Randy who turned it around quickly]

Interesting about the European Car review. But in any event, the exhaust upgrade does not seem cost effective in the same catagory as the pulley, ECU and intake. I play to have the Alta intake installed next week.

 

Madness-Intake, Helix Pulley, Stock exhaust.

Before: 159.6HP 135.2 Torque

After: 170.5HP 149.4 Torque

TwoMINIs, did you get the fax I sent you from Charlie?

-Jim

 

Jayoung and I were dynoed at the same location, different days.

madness intake, Magnaflow exhaust.


Before 147.5 hp 129.6 torque

Added pulley

After. 167.4 hp 144.5 torque


As you can see I produced LESS HP and Torque with the Magnaflow than Jayoung with stock exhaust with other equal mods.



His, Chile RED all over, Madness intake, MINI-Motorsport Airbox Mod, Magnaflow Exhaust, BMP spark plug wires, RDR rear sway bar and Helix P/D 15% reduction pulley.
Hers, EB UJ on top and BONE stock.

 

TwoMinis, the question your post and Jayoung present us with is his mod only netted him 11hp while yours netted 20hp. Sure, different dynos on different days but the delta is remarkably different.

I'm in the same situation where I have the pulley, ECU and intake but with the stock exhaust still. I just don't know if it generates enough hp to be worth the money. Hopefully others will chime in and clear this up.

Regards,
Jim

 

TwO,

My Dyno was on April 2nd. I met you at International Mini on the 23rd. You got the pulley on May ?? It was dynoed on the same machine by the same guy but temperature was different. (shrug) Charlie did do my car warm both on the baseline run and afterward.

We should do it again side-by-side but I don't think I can get that by the CFO. Best of all, put a Magna back on my car and see how it changes.

-J