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That's absolutely true. It is a noticeable hunk louder running open without the cat. With the valve back in the circuit it's hard to tell if there is a difference between before and after. I put a number of miles on today to try and get the measure of the thing.

I still can invoke that rev hang thing when being an ass but I think it doesn't stutter as much when rev matching the downshifts.
It feels faster but that has to be psych related, right? The sounds coming out of the tail coupled with the supercharger whine (I have a K&N ) are tres exotique. As good as you need. The smooth, unbroken slightly 'metal humming through a French horn' tone that the car has always had is unchanged but a bit more amplified and maybe just a touch lower in pitch. I should have done before after measurements because that's what I did for forty years, but oh well.

So it is louder in a pleasing, familiar way and seems to have no negatives. I will probably be closing the valve more around town but there's another plus. It doesn't drone at 75 or 80 or on steady throttle. And .it feels faster even if it isn't, which my rational brain tells me couldn't be.


Greg's pipe itself is quality yet shows that it was custom made for this application, probably one or three at a time. Very Lotus.

I gotta do more of this. You people are a bad influence.
 

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Just to reiterate others’ comments and add a few of my own after driving from Las Vegas to Tucson with the newly installed decat pipe. As a side note, the service manager at Lotus West said they will be recommending the decat to all their customers after daily driving my car a couple of days to make sure it was all put back together properly after the pack rat fiasco.

I drove a couple of 400s while I was living in Dubai, but the intervening time in my US 400 had caused me to forget just how incredible the soundtrack is with only 2 cats. This is an absolute must for all 400 owners. And so inexpensive from @GregsRaceParts. The car now has what is for me the exact right volume and character. At idle and low speeds, you get an awesome rumble especially in race mode that isn’t there before decatting. At wide open throttle, there is hell to pay. I’m not judging any of the straight pipe folks, but I just can’t imagine wanting anymore volume than the car now has. In fact, I finally started using the exhaust button to close the exhaust valve in sport mode while I was cruising at highway speeds. With the decat pipe, the difference is noticeable when cruising around 70-80mph. Without the decat pipe, there is no real need to silence the exhaust while highway driving.

In summation, the car now has a soundtrack that says the car means business without being completely obnoxious. It’s like James Bond (classy, but will kill you) rather than musclebound goons that Bond regularly dispatches. You can decide which cars fill in for the goons in that analogy. And there are now 3 meaningfully different ways to enjoy the soundtrack—sport mode, race mode for even more bass, and valve closed mode while in sport during highway speeds to save your ears while still providing the alacrity of sport mode. I suppose you can add the default neutered normal mode, but the only reason I will ever drive without sport or race mode is long distance highway cruising just on the off chance it somehow increases fuel efficiency.
 

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In fact, the difference between open and closed is even more pronounced, which makes sense I suppose. Open, a smooth, sonorous flow of tone, rising in level and sincerity along with the revs. I don't know if the car is any faster but it feels more like the 4 second car it is now than it did before. With the valve closed, the party is over, the band picks up its gear and goes home and you can get some rest secure in the knowledge that everybody had a good time.
 

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So, I already have Greg’s decat pipe and love the sound and slight power increase. But, has anyone determined the HP increase with the intake after doing the exhaust mod? More noise is great as long as there is a performance advantage as well. The only dyno I’ve seen is for the combination of the decat and intake.
 

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I finally got around to installing mine. Did it in my driveway with hand tools, floor jack, and jack stands. It was pretty straight forward. I highly recommend a rubber mallet to aid in getting the stock cat out of the muffler and renting a pipe expander tool to make inserting the decat pipe much easier. This really does dial up the sound a ton with the valve open and I'm super happy with the final result. I also noticed that the throttle blips are much more consistent now than they were before as others have mentioned.
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US Evora 400 owners, if you have not gotten the decat pipe (A132S0230F) that removes the unnecessary secondary cat that comes on US/Federal cars, you are doing yourself a huge disservice.

Just had mine installed today, and it COMPLETELY changes the exhaust note in a massively good way. The majority of Evora 400 reviews on YouTube talk about how amazing the exhaust sounds, but when I got mine I was pretty disappointed relative to my Evora S with Larini decat and exhaust, which I loved. Most of the reviews were on ROW cars which come from the factory without the secondary cat, while US/Federal cars have the secondary cat.

The 400 with the decat pipe makes the car sound like it should. It's loud, but not loud just for the sake of being obnoxiously loud (a la Jaguar F-Type). It's hard to believe that a Camry engine can sound this good. I could drive around for hours with the windows open just enjoying the exhaust note. It really is that good.
Is there any drone on the highway ?
 

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I don't know if I would say it has drone (I have had cars with bad drones so I know what it sounds like) but I generally shut the valve if I'm just steady cruising at 75-80mph. It's just a constant noise that I would rather not listen to since hitting the button makes the car become much more serene. Once I'm off cruise control I open the valve again as I like to hear the noise when it's not steady state.
 

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So we didnt purchase the OEM part posted by OP, rather we just cut out the cat and installed a straight pipe.

Sound improvement is noticeable but modest. It is slightly louder, particularly under WOT, however not significantly so. Happy I did it, however, it did not produce a significantly different exhaust note.
Good Info. Was on hte verge of doing the same thing as well. I wanted to keep the sport exhaust button functional but might spring for the plack exhaust instead. Love the SportsCarWorld people ive met there. Nice Peeps
 

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I am not sure what the last few posters are on about. With GRP decat pipe, the valve button remains fully functional and car is serene/quiet/stock on highway. There is zero drone. It definitely changes the tone of the exhaust at moderate loads, and pushes the 'scream' down in the rev range and makes the sound more accessible.

There is no need to think so hard about this mod. The answer is always DO IT.
 

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The reality is that it isn’t really a mod. It’s restoring the car to its original design. The “mod” was Lotus adding the 3rd cat to meet California air standards.
 

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When Jay Emm visited America two years ago, he stopped here in Nashville and we put him up. We took my car down the Nachez Trace where he had an opportunity to wring it out. He commented to me how much quieter my car was than his even when used in anger.

We quickly surmised that was due to the addition of the third cat which they don't get in Europe. As BJBJ says, our cars are delivered with that third cat, a feature the European cars do without. So there!
 

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Just do it, people. The car sounds so much better (yet is still whisper quiet with the valve closed), the engine response is improved, and you drop a little weight off the back of the car. I cannot imagine anyone being uphappy with the modification.
 

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The only reason not to ditch the 3rd cat is California CARB, or if you are installing headers, in which case the 1st/2nd cats are deleted and the 3rd with modification to accept the O2 sensors is needed to be a steward of our air.
 

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Julian's comment begs the question: how much negative effect does removing the third cat cause vis a vis emissions compared to retaining it? Probably a hard one to answer.
 

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Julian's comment begs the question: how much negative effect does removing the third cat cause vis a vis emissions compared to retaining it? Probably a hard one to answer.
Well, I'm in CA, and haven't had a 3rd cat since I bought the car. I've passed 2 smog tests so far, with values nowhere close to the limits. The great thing is most shops have zero clue as to how many cats the car is supposed to have, so it passes visual and emissions based on the 2 primaries. Of course YMMV depending on your state's smog laws, testing procedures, etc etc.
 

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^Good to know. I guess I'll find out for myself this year when I re-register my car. TN does annual inspections, not that we have particularly clean vehicles here. Rolling coal anybody?
 
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