So, I finally gave in and got the Mina exhaust to eliminate my droning problems in my '08 XK. I also took a couple of performance measurements with the stock exhaust and with the Mina.

First, the good news; the Mina exhaust claims 15-18HP increase at the top end. My test easily bears those claims. The test was accelerating from 70 to 110 MPH, starting in 3rd gear and finishing in 4th. Of course, it was done in a controlled, safe environment so, boyz, don't try this on your public roads...bad...bad...bad...

All conditions, road section, temperatures etc being the same the stock exhaust produced an acceleration time of 12.71 seconds while the Mina exhaust beat that handily at 9.28 seconds. That is a SIGNIFICANT gain in power to produce nearly 3.5 sec. difference.

The Mina exhaust is a piece of art, most certainly the best made, most beautiful piece of exhaust I ever come across. Too bad most of it is hiding under the car as it should be seen and appreciated. My muffler shop commented how great the quality was. I'd say, expensive but, well worth the price in quality. No, I am not associated with them in any ways.

Now, the bad news; my senses tell me that the high RPM gains came at the expense of some low end losses. The car will not pull away as smoothly from extreme low RPMs, such as 1500 RPM, particularly at slight uphill driving, as the stock exhaust. When you try there is a definite sense of lugging the engine and the accompanying drone. So, downshifting is pretty much a must to prevent lugging the engine and the booming drone that goes with it.

The sound from the Mina is not as loud as I expected from reading comments here. At start up and take off the sound is superior to the stock exhaust; it is a pleasant, sophisticated deep rumble as opposed to the (for me) not so pleasant sounds from the stock muffler. At wide open both mufflers sound aggressive and good with the stock sounding more like an American muscle car wide open vs. the Mina sounds more like a refined race engine with a sharper tone at wide open. The Mina does not sound louder than stock at wide open, just different.

I have not driven my regular 150 mile freeway distance yet to see if the dreaded 2000 RPM drone comes in after a half an hour; I hope not. Will find out this weekend.

Albert

 

Awesome write up! Thanks for taking the time to give a full and informative review.

When my stock needs replacing I plan on going with the Mina as well.

One question, is it from the cats back or mid section?

Thanks again!

 

What pipe diameter is used in the Mina system?

 

Mike; the Mina exhaust is a rear muffler replacement only, leaving the mid section resonator in place and simply attaches to it.

The Mina pipe's outside diameter (OD) is 2.29". I did not measure the wall thickness but, they are heavy duty pipes when it comes to stainless. I am used to seeing thinner wall thickness in stainless after-market piping.

Albert

 

Do the active exhaust valves stay in place with Mina exhuast?

 

No, the active valves are located on the stock muffler and not used on the Mina. The benefit of those active valves is that you retain the low-end torque with the valves closed while have decent high end as the valves open. With the Mina, it appears to concentrate at gaining high end power at the expense of low end.

Albert

 

Corrected the Mina exhaust pipe OD diameter to 2.29". Must have been asleep still when I posted originally 1.29" for it.

Albert

 

Ok; where is the link to the youtube sound clip?

 

Why would restricting the exhaust at lower rpm cause an increase in torque?

Bruce

 

Less restrictive exhaust systems reduce "back pressure". Back pressure is required for low-end torque.

 

Bruce

Exhaust is a science in itself despite its apparent simplicity. Here is one of the better description of why you could loose low end torque with a more open exhaust:

http://www.bigcitythunder.com/pages/...ng_exhaust.pdf

In my decades of high performance experience, I could never tune an engine to where I would NOT loose low-end torque as a result of opening up the exhaust for high-end gains. Perhaps it is possible but, I have not been able to do it.

The Mina gains tons of high-end power over the stock one but, looses a fair amount of low end torque. As I said so many times, all aftermarket additions tend to come with gains AND losses. In most instances the factory figures out a "happy compromise", in this case, good low-end torque with fair high-end, and when you change a component to improve on one, you tend to loose at the opposite end of the curve.

What you have to ask yourself is; what's important for you in a car? If you freeway drive or city traffic drive most of the time, you want smooth low end torque. If you enjoy performance driving, meaning that you spend a good part of your driving time over 4000 RPM, than you will benefit from a free flowing exhaust that will reward you at the high-end. In my acceleration tests, the XK really felt like it was beginning to struggle at 110 MPH with the stock exhaust while with the Mina it was still winding up and cutting through the RPM range as a hot knife would cut through soft butter. On the other hand now with the Mina downshifting is necessary where it was not needed before. That is the difference.

Burg: I do not have a video clip. Moe-she-sa has one with his Mina equipped car on the dyno, you may ask him to post it again.

Albert

 

Tha's the opposite then compared to turbocharged cars, where exhaust back-pressure reduces the turbine's ability to build boost pressure and torque. Superchargers are of course pulley driven instead, which I know is completely different, but I'm curious what is it about back-pressure from a restricted exhaust flow that would help the engine make more torque at low rpm with no boost, or help to increase revs quicker so the supercharger could increase boost pressure and make increased torque from that.

That sounds counter-intuitive, but I'm sure a simple technical explanation would help if anyone can do that. I'm familiar with "scavaging" effects on a normally aspirated engine, but that wouldn't apply with forced induction.

Bruce

 

I think Axr6's car is an XK vs an XKR Bruce. Which sheds light on the differing points of the conversation.

 

Oh yes, thank you, and thanks for the informative link Albert. Turbo-charged engines that I'm used to react differently.

Bruce

 

"backpressure" is a bit of a misnomer.

What is important is to retain the velocity of the exhaust gas column.

That avoids intake charge dilution.

The effect is lessened for turbocharged and supercharged engines as the intake charge is at greater than atmospheric pressure.

 

so does that mean that there would not be low end torque issues with a mina exhaust installed on the XKR?

 

Mina should create an exhaust with the active valves which balances gains on both low and high.

 

Mina claims a mid range gain of horsepower...it's on their website. I was considering getting their exhaust but I think I'll just stick with the stock exhaust system and consider more the ECU tune upgrade.

I originally posted they claim a low end gain...their website doesn't reflect that now and I may have been mistaken in that regard; I could have sworn that I read that some time back on their website. Anywho, the loss of low end torque is a big concern for me since I don't drive my XKR at 100+MPH very often...

 

One more observation to add to my posts regarding the MinaGallery exhaust.

Prior to installing the Mina, I had the factory brackets installed by the dealer to eliminate the 1200 RPM drone. It did that but, I thought that it transferred to drone to 2000 rpm, my usual cruising zone. So, I removed the brackets to see if the 2000 rpm drone would go away. In removing the brackets I had to cut and throw away the driver side bracket. In the end, removing it really did not make much difference in the 2000 rpm drone.

So, when I installed the Mina, the 1200 RPM drone got much worse, louder as well as wider in range from 1000 - 1500 rpm. The 2000 rpm drone was about the same with the Mina. Last weekend I re-installed the passanger side brace and put a "makeshift" ring around the driver side cat converter to reduce the drum effect that obviously originate from the cat converters. The result is the near elimination of the 1000-1500 drone. I am confident that with both factory braces the drone would be completely gone at these low rpms when using the MinaGallery exhaust. 2000 rpm drone is unchanged, still. I have the feeling that the cat converters are just not a right match for the exhaust frequencies that the Jag 4.2L V8 produces. If they were the factory would not have come up with the braces, which basically is a band-aid fix for the droning problems.

Albert

 

Hi,

Does anyone have info on how this exhaust may perform on a naturally aspirated 4.0 liter? I am far more concerned about my low- and mid-level torque than I am about high-end performance, and I don't want to spend money only to lose where I want to gain.

Thanks!