You got 27 bhp with a bolt on exhaust upgrade to a 1.6 liter engine? Good luck on this one now!

 

As I mentioned before, as soon as teh car gets here, we will be doing our own independent testing with all control methods shown. We are very diligent in our testing methods. We will include before and after as well as ambient and car conditions for the dyno, same gear acceleration numbers before and after, and weights.

I also know that Stratmosphere has purchased an R56 and plans to do testing of their own.

Between all of us, we should have pretty good info available .

Hope that helps!
Randy

 

27HP gain is awesome. I was hoping you had tested before so you'd know for sure it was that much gain and not already a 'strong' MINI before testing.

good job!

happy about interchangable tips too. I prefer the two tips myself.

waiting to hear the catback results!

 

I think they are saying that those dyno results were "given" to them...not their results. It sounds like there are no before results, so the assumption is that the before is the sticker bhp. It should be very interesting to see the comparative results as well as how much hp people get out of this car if there is a potential for 20+ hp from just an exhaust. I'm gonna have to trade in my "new" mini for a new new mini.

 

[EDIT] Car was NOT baseline dynoed before (stock).

All I could say since then is how FAST that darn car is. No wonder, it's making over 200hp along with a big fat early torque curve. Can't wait unitl our car arrives in Feb. -Pete

 

Does changing the exhaust on a turbo car have more effect than on a non-turbo car? I was wondering if a free-flowing exhaust means faster flowing gasses spin the turbo better so you get a double benefit. This would mean the exhaust gains on a R56 could be more than on an R53. Just a guess - any ideas?

 

I don't like the tips.

 

Changing the exhaust on a turbo car can have the most benefit. Next in line for benefits would be the supercharged engine (forced induction again). Last would be a normally aspirated car.

Febmoon1- We have two tip styles in the pic. You dislike both? -Pete

 

Yikes - I had sworn myself off tinkering, but this sounds like such easy and safe hp. Any chance there will be a less expensive version without the gratuitous polish? I'd want the hp, hold the bling.

Also, how much louder does it get? After living 5 years with a SS system on my acura I can't say I'm into turning up the volume any longer.

 

Changing the exhaust on modern cars such as the MINI, with no other changes (such as ECU) typically results in nominal or even loss of HP. On the 2007 MINI, a car touted to have a highly efficent exhaust and a ECU that has been carefully matched to the components that make up the engine system, any positive change in HP with a single bolt-on is highly questionable. With today's engines, only by carefully matching component upgrades in conjuction with an ECU reflash, are these type of gains feesiable.

Here is an excellent study (with dyno results) of an exhaust and airbox upgrade on a R53: http://www.motoringfun.com/2007/01/2...no-day-part-1/

Note how the addition of the exhaust bolt-on results in a nominal loss of HP. With the addition of the airbox, a modest gain is recorded. An independent dyno study, such as the one outlined on the R53 above will give a true picture of how this R56 exhaust bolt-on impacts the current engine and its management system.

 

with the increased exhaust gas flow i think this mite reek havoc with the turbo so there could be warranty issues

 

Fair enough Slag. Point well taken. Now I'll give counterpoint. Until a bunch of tuners strap various exhausts up to the R56, we won't know if MINI chose a more restrictive exhaust on the R56 in an effort to
a) maximize low-end torque
b) maximize fuel economy
c) allow for massive improvements on the engine when they go to JCW tuning.

So that's wild speculation, and my personal opinion from everything I've read on the subject is that on paper, turbo cars are not as responsive to exhaust tuning, contrary to another post above. Why? Because with forced induction, turbo, supercharger, or both, the scavenging effect of a crossflow combustion chamber is not as important. Why? Because forced induction gets a healthy charge regardless of whether or not the exhaust pulse helps pull air in. N/A on the other hand, is reliant on that crossflow head design and the extraction effect pulling in a charge (only vaccuum acting on the intake side here) assuming duration in the cams are set to allow for exhaust staying open during the intake stroke. This is why variable cam timing is used, because at low revs that phenomenon won't work.
Supercharged engine can definitely be happier with less exhaust restriction as reversion will put dirty exhaust pulse back in the combustion chamber and inhibit the perfect charge.
Traditionally, turbos are the least responsive to extensive exhaust tuning, because the turbo itself is a huge restriction in the exhaust path and is very close to the head. Maybe with the twinscroll there's much more of the exhaust charge being uninhibited, and if that were true then turbo cars could in fact be more responsive to good exhaust tuning.

Of course, manufacturers have a lot of factors helping to decide whether to make the power, the torque, the noise, the fuel economy, so the gain from changing to an unrestricted exhaust has to compared to the stock exhaust and what its compromises are.

 

I have been following the tuning threads since the MCS was introduced and this is the first showing a loss with a cat-back. I have had a Magnaflow and Borla on my car and using a G-Tech Pro came up with a 10hp increase for the Magnaflow and 5hp for the Borla - this is consistent with other tests I have seen run on a dyno. I don't agree that swapping the exhast generally reduces power.

 

Traditionally shops rely on head work a lot more on NA cars because when there is no forced induction, every bend, rough surface and unmatched port is a detriment to the perfect charge.
Again when you move to force induction, this head work give less % improvement.
So was the replacement head on JCW kit for R53 overkill. The army of folks who elected to do a pully, exhaust, and intake showed that it probably was (as did their dyno numbers), but I guess there's always the pride on the JCW side that your car was done "right". I'm a firm believer that MiniMania's power gains needed those worked heads too, but that's big power.

When the bean counters ask about the logic of JCW shipping a car to a dealership with a head installed and then asking a dealer to tear it off and replace it with an ever-so-slightly better head (without hand port matching, mind you) you have to figure out if the dealer labor charges are the best place to get $ from customers (it may be?)
From what we've read on Motoringfile, JCW is taking a whole new direction, so if there is an improved head, it'll be installed in the first place.
But maybe they won't even go there, and maybe this Miltek exhaust is telling of how the JCW kit will improve on power on the Prince

 

The bottom line is that we won't know until the unit and the car gets here and we can strap it on.

This new car may have specific differences that account for gains that would otherwise be unheard of on a turbo. Or, the numbers may be skewed, but still the best out there (I've seen that before in the beginning of the R53 testing - Magnaflow).

As to which cars benefit the most from exhaust tuning, I would offer that the standard exhaust would be the most significant variable in what a new tuned exhaust may or may not do. All things equal, I agee that tuning on an NA motor is much more critical than on forced induced, but again, if the turbo is being restricted by the turbo-back exhaust, it will prevent more efficient spin-up of the compressor section of the turbo.

Hope that helps - can't wait to check it out!

Randy

 

Just a point of claification. We have been tuning turbocharged motors for 7 years here. The gains seen on the Milltek are a bit more than we would normally see on a stock car. But not necessarily by a large margin.

The cat is close to the turbo on this car and probably the cat improvement (HJS 200-cell stainless, best available) is having a large impact. This result is *very* similar to VW Golf/Jetta 1.8T. Usually software changes provide another large gain. In the case of this new Mini, it could be that the OEM software quickly adapts to the new mechanical condition seen with the Milltek installed.

From our many years of exhaust development normally aspirated cars see gains of 2-3% with exhaust changes. Turbo cars 5% and beyond. This is a gross generalization but what we expect to see each time. Cat changes can add another dimension.

With the Supercharged Mini the path to increase was usually...

1) Pulley
2) Software or Exhaust

With the turbo car I predict that path will be...

1) Software
2) Exhaust

Since we have no software data yet, it will take some time to see if if plays out this way. -Pete

 

Pete, now that people are done accussing you of lying do you have any idea about my questions:

 

lava- Ha, no worries. The production units won't be polished on the pipes. The muffers will be shiny. The pricing hasn't been announced but it will be within reason. I think the sound is great. These cars are more quiet than the Supercharged model. Downpipe/cat will add more sound. -Pete

 

Ok - the whole thing looked shiny in the image - I know that people that like their bling want the whole system polished. Thats fine, they can polish the pipes themselves - builds character...

I'll have to wait to hear it myself someday. I'm more likely to wait till the oem system corrodes out, and then replace with something like this.

 

I do not have a bunch of tuning experience w/ turbo cars. However I have been thru the full set of tuning with the Subaru STi. The basic upgrade power path is ECU tuning then exhaust.

Bolting on just a turbo back exhaust can gain 25-30hp (10%) however boost creep, fuel cutoff, and extremely lean conditions usually happen.

A ECU tuning change will also get 25-30 hp. This is by changing the boost levels, cam timing, ignition timing, and fuel maps. By then adding a down pipe (much less restrictive) another gain of 20-25 hp is made. However the powerband is also widened at this time over stock. Further custom tweaking of the ECU maps can net another 25-45 hp. Now this is on a 2.5L motor. Each step is about 10% change.

I would like to see a picture of the stock exhaust. Also specifications of its size vs. the Milltek exhaust would also be benifical. The STi stock exhaust is ~2.5" most aftermarket are 3" with big hp systems using 3.5".

Reducing the backpressure on a turbo will get better flow but most importantly quicker flow. This is the main reason exhausts work really well on turbo cars. Better cats is also in the equation. My Cobb exhaust removes the cat right after the turbo but has the one in the midpipe. This helps a bunch with spool-up of the turbo. My torque peak is down 1,100 rpm from stock and the hp peak is up 500 rpm. This is a huge change along with the +80 hp and +120 tq.

I really look forward to what happens when the ECU is cracked and a good exhaust system is matched and tuned. I just hope the injectors are not pushed past their limits.

 

A %10 positive change on the new MINI would result in 17hp... I agree, carefully matching ECU changes combined with other bolt-ons is the key to enhanced performance, they go hand in hand. Another key factor is impact on engine longevity and heat dissipation, both which could prove promblematic. There has been reports that Munich is struggling with finding the right balance for the JCW version.

 

Like wrx_xb9r I also have a WRX (2002, not and STi) with an upgraded exhaust and computer reflash (Cobb stage 2). I added the exhaust before the reflash since boost creep and the lean issues didn't seem to be problems for the 02 model year cars. The affect of the exhaust system on low end torque was very noticeable. I no longer found myself turning off the a/c every time I left a stop sign and 5th (top) gear could actually be used to accelerate the car, not just maintain speed. I used an OBD 2 logger for all the changes and although the change to the boost curve doesn't look very drastic, the feel of the car was very different.

That being said, when I get the Mini, I won't consider an exhaust system until after a reflash has been developed or there is sufficient testing, logging and experience to show the exhaust without the matching reflash does not cause any problems.

Below are some quotes from Jay, an engineer at Garrett. It's a long read, but I promise it has some very good information. This is an old post from NASIOC for which I don't have the original link, just the text I copied into a word document for future reference:

"Post 1:
This thread was brought to my attention by a friend of mine in hopes of shedding some light on the issue of exhaust size selection for turbocharged vehicles. Most of the facts have been covered already. FWIW I'm an turbocharger development engineer for Garrett Engine Boosting Systems.

N/A cars: As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium here.

For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header). You'll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you'd get if you just got boost sooner instead. You have a turbo; you want boost. Just don't go so small on the header's primary diameter that you choke off the high end.

Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.

Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range.

As for 2.5" vs. 3.0", the "best" turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this power level won't get you much, if anything, other than a louder exhaust note. 300 hp and you're definitely suboptimal with 2.5". For 400-450 hp, even 3" is on the small side.[/FONT]

Hope this helps.
Jay


Post 2:

As for the geometry of the exhaust at the turbine discharge, the most optimal configuration would be a gradual increase in diameter from the turbine's exducer to the desired exhaust diameter-- via a straight conical diffuser of 7-12° included angle (to minimize flow separation and skin friction losses) mounted right at the turbine discharge. Many turbochargers found in diesels have this diffuser section cast right into the turbine housing. A hyperbolic increase in diameter (like a trumpet snorkus) is theoretically ideal but I've never seen one in use (and doubt it would be measurably superior to a straight diffuser). The wastegate flow would be via a completely divorced (separated from the main turbine discharge flow) dumptube. Due the realities of packaging, cost, and emissions compliance this config is rarely possible on street cars. You will, however, see this type of layout on dedicated race vehicles.

A large "bellmouth" config which combines the turbine discharge and wastegate flow (without a divider between the two) is certainly better than the compromised stock routing, but not as effective as the above.

If an integrated exhaust (non-divorced wastegate flow) is required, keep the wastegate flow separate from the main turbine discharge flow for ~12-18" before reintroducing it. This will minimize the impact on turbine efficiency-- the introduction of the wastegate flow disrupts the flow field of the main turbine discharge flow.

Necking the exhaust down to a suboptimal diameter is never a good idea, but if it is necessary, doing it further downstream is better than doing it close to the turbine discharge since it will minimize the exhaust's contribution to backpressure. Better yet: don't neck down the exhaust at all.

Also, the temperature of the exhaust coming out of a cat is higher than the inlet temperature, due to the exothermic oxidation of unburned hydrocarbons in the cat. So the total heat loss (and density increase) of the gases as it travels down the exhaust is not as prominent as it seems.

Another thing to keep in mind is that cylinder scavenging takes place where the flows from separate cylinders merge (i.e. in the collector). There is no such thing as cylinder scavenging downstream of the turbine, and hence, no reason to desire high exhaust velocity here. You will only introduce unwanted backpressure.

Other things you can do (in addition to choosing an appropriate diameter) to minimize exhaust backpressure in a turboback exhaust are: avoid crush-bent tubes (use mandrel bends); avoid tight-radius turns (keep it as straight as possible); avoid step changes in diameter; avoid "cheated" radii (cuts that are non-perpendicular); use a high flow cat; use a straight-thru perforated core muffler... etc.

Jay

Post 3:
Sorry, I've been busy wrestling alligators.

Anyway, back to the subject. Here's a worked example (simplified) of how larger exhausts help turbo cars:

Say you have a turbo operating at a turbine pressure ratio (aka expansion ratio) of 1.8:1. You have a small turboback exhaust that contributes, say, 10 psig backpressure at the turbine discharge at redline. The total backpressure seen by the engine (upstream of the turbine) in this case is:

(14.5 +10)*1.8 = 44.1 psia = 29.6 psig total backpressure

So here, the turbine contributed 19.6 psig of backpressure to the total.

Now you slap on a proper low-backpressure, big turboback exhaust. Same turbo, same boost, etc. You measure 3 psig backpressure at the turbine discharge. In this case the engine sees just 17 psig total backpressure! And the turbine's contribution to the total backpressure is reduced to 14 psig (note: this is 5.6 psig lower than its contribution in the "small turboback" case).

So in the end, the engine saw a reduction in backpressure of 12.6 psig when you swapped turbobacks in this example. This reduction in backpressure is where all the engine's VE gains come from.

This is why larger exhausts make such big gains on nearly all stock turbo cars-- the turbine compounds the downstream backpressure via its expansion ratio. This is also why bigger turbos make more power at a given boost level-- they improve engine VE by operating at lower turbine expansion ratios for a given boost level.

As you can see, the backpressure penalty of running a too-small exhaust (like 2.5" for 350 hp) will vary depending on the match. At a given power level, a smaller turbo will generally be operating at a higher turbine pressure ratio and so will actually make the engine more sensitive to the backpressure downstream of the turbine than a larger turbine/turbo would. As for output temperatures, I'm not sure I understand the question. Are you referring to compressor outlet temperatures?

The advantage to the bellmouth setup from the wg's perspective is that it allows a less torturous path for the bypassed gases to escape. This makes it more effective in bypassing gases for a given pressure differential and wg valve position. Think of it as improving the VE of the wastegate. If you have a very compromised wg discharge routing, under some conditions the wg may not be able bypass enough flow to control boost, even when wide open. So the gases go through the turbine instead of the wg, and boost creeps up.

The downside to a bellmouth is that the wg flow still dumps right into the turbine discharge. A divider wall would be beneficial here. And, as mentioned earlier, if you go too big on the bellmouth and the turbine discharge flow sees a rapid area change (regardless of whether the wg flow is being introduced there or not), you will incur a backpressure penalty right at the site of the step. This is why you want gradual area changes in your exhaust.

Jay"

 

there a guy on mini with a custom exhaust with a rolling road read out of 210 bhp but settled for 192 bhp so its possible to get 200bhp

 

Please explain this from MINI2:
http://www.mini2.com/forum/2nd-gen-e...ml#post2880002

 

I like it very much but like SS should offer a variety of tips.