3rd Cat Delete

Komotec on their page clearly states that this is a track only mod, and not for the street. They also point out that mods like this will very likely void your warranty. If you think "I'll just put the cat back on if I have a problem", it will be obvious to a tech if the factory original installation has been tampered with, so for those of you thinking of doing this, you might want to wait until your warranty has expired. For the first 3 years, considering what we're already seeing from this first production run, a warranty is a good thing to have.
 
Komotec on their page clearly states that this is a track only mod, and not for the street. They also point out that mods like this will very likely void your warranty. If you think "I'll just put the cat back on if I have a problem", it will be obvious to a tech if the factory original installation has been tampered with, so for those of you thinking of doing this, you might want to wait until your warranty has expired. For the first 3 years, considering what we're already seeing from this first production run, a warranty is a good thing to have.
@Eagle7 agree

If there’s no big noticeable difference, it’s not worth risking the warranty
 
Probably worth mentioning that the closely-coupled cats are designed for fast heat-up on cold engine start, and likely lose efficacy at high temp. The cat after the exhaust merge is slower to heat up but usually maintains efficacy into higher temp ranges.

Just pointing out that "primary" and "secondary" don't necessarily mean "main" and "lesser"... in active operation it's possible that the roles are the reverse.
Yes, absolutely true.

You could also call the primary a "pre-cat" and the secondary the "main cat". I think it derives from the EU3 (Euro 3 or Euro 4 emission standard it was), which made it necessary to have a cat installed nearby the cylinder head in order to heat up within 60 seconds to operating temperature because emissions from that standard on were measured right from the beginning of the engine cold start.
 
Is it possible that a design change could mean removing the secondary cat won’t be as dramatic as it was when removed from North American Evora’s. Judging by the video and comment above, He said it wasn’t much louder with the straight pipe
They use a different type of muffler (silencer). The Evora had a single exit in the center, while the Emira has dual exhaust exiting out the ends of the can. That can make a significant difference in how it sounds, and how it reacts to changes.

1675269610793.png

As you can see above, the Emira also has a split silencer inlet where the main exhaust charge coming from the engine is diverted to a narrower input tube, or the valve opens to allow full exhaust flow through. Very interesting design.


For more info on the cat layout... here's the downpipe itself. It looks like each bank has a pre-cat closely coupled to the engine, followed by a merge and a wider section that is either a flex joint or a resonator. This is followed by the "secondary" (as described in previous posts) cat after the downpipe, between the downpipe and the silencer.
1675270066692.png


Close view of one of the pre-cats, closely coupled to the engine in the exhaust manifold. There's one of these per side, and the design varies slightly.
1675272523440.png


Ignore the black arrows throughout these images, those are parts removal instructions, not relevant to the flow direction.

[edit] Fixed above description to clarify cat routing
 
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They use a different type of muffler (silencer). The Evora had a single exit in the center, while the Emira has dual exhaust exiting out the ends of the can. That can make a significant difference in how it sounds, and how it reacts to changes.

View attachment 21970
As you can see above, the Emira also has a split silencer inlet where the main exhaust charge coming from the engine is diverted to a narrower input tube, or the valve opens to allow full exhaust flow through. Very interesting design.


For more info on the cat layout... here's the downpipe itself. It looks like one bank has a pre-cat before the merge, and the other bank has no cat before the merge. Both sides then flow into what appears to be a primary cat, followed by the "secondary" (as described in previous posts) cat after the downpipe, between the downpipe and the silencer.
View attachment 21971

Ignore the black arrows, those are parts removal instructions, not relevant to the flow direction.
@Porter , thanks. Too technical for me, but it appears because of this silencer design, removing the secondary cat could prove to be futile. You may need an entire silencer change to make a significant difference
 
For more info on the cat layout... here's the downpipe itself. It looks like one bank has a pre-cat before the merge, and the other bank has no cat before the merge. Both sides then flow into what appears to be a primary cat, followed by the "secondary" (as described in previous posts) cat after the downpipe, between the downpipe and the silencer.
View attachment 21971

Ignore the black arrows, those are parts removal instructions, not relevant to the flow direction.
As this is CAD print I think what you refer to as primary cat could well be a flex joint which isn't shown properly (only outer dimensions for digital mock-up). I assume this as there must be a flex section in order to compensate the engine movements.

On the picture above you can almost see both pre-cats which are flanged to the merge pipe.
 
Drawing on my previous Evora experience, this setup is almost identical apart from the single v twin outlet. The split, valve-controlled, silencer inlet was similar.
There is a ‘primary’ cat in each manifold (just not quite visible in @Porter ’s pic above.)
The secondary cat was only fitted for certain, strict, markets.
There are no O2 sensors around this cat so removal does not throw codes.
Removing it does make a significant difference to sound.
As for warranty concerns, YMMV, but mine will be removed.

Edit: here’s the Evora setup.
Where it’s labeled “link pipe” is where the ”third“ cat goes.

BADB9BD2-3982-4D1C-8A34-02669C736888.png
 
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As this is CAD print I think what you refer to as primary cat could well be a flex joint which isn't shown properly (only outer dimensions for digital mock-up). I assume this as there must be a flex section in order to compensate the engine movements.

On the picture above you can almost see both pre-cats which are flanged to the merge pipe.
Thanks, I fixed my description. You're absolutely correct.

I also added an image showing the pre-cat location in the exhaust manifold (per side).
 
Who is going to be the Guinea pig and then report back how much better the car sounds with this ?
I’ve ordered one already.

I had an email from Komotec and they needed a National Insurance number for shipping… sounds like you may get an extra tax bill as well as a voided warranty in the process!

Cost inc delivery to the UK was €312.

I’ll keep you all posted how I get on…
 
I’ve ordered one already.

I had an email from Komotec and they needed a National Insurance number for shipping… sounds like you may get an extra tax bill as well as a voided warranty in the process!

Cost inc delivery to the UK was €312.

I’ll keep you all posted how I get on…
We look forward to hearing back from you
 
With regards to the warranty, @TomE do you have any contacts at Lotus who would go on the record about such a mod being acceptable?

Does anyone know what were Lotus’s views on the same mod on previous cars?
 
I'm not aware of any manufacturer that would ever condone removal of an emissions control, even for off-road purposes. The regulatory enforcement risk is extreme.
 
Does anyone know what were Lotus’s views on the same mod on previous cars?

Apparently they'll void the warranty if you change the shift knob yourself, so I'm sure any exhaust modification is out of the question. 🙃
 
Apparently they'll void the warranty if you change the shift knob yourself, so I'm sure any exhaust modification is out of the question. 🙃
It must suck for UK buyers to need to stop by Hethel for factory petrol replacements! Luckily I’m close to my local dealer. ;P
 
If you need evidence of their general position on aftermarket changes to the car affecting warranty, here's a sample TSB regarding changing the Evora air filter to an aftermarket unit:
 

Attachments

  • TSB_2020_01_USA_Unauthorised_Modification_Warranty_Implications_.pdf
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With regards to the warranty, @TomE do you have any contacts at Lotus who would go on the record about such a mod being acceptable?

Does anyone know what were Lotus’s views on the same mod on previous cars?
As @CDM1855 has said, there is now a strong policy of Lotus regarding un-approved modifications as invalidating the warranty.

When I did 3rd cat delete on my Evora S in 2012 the dealer did the work and said it wouldn't affect the warranty.

They have also become much less accommodating about borderline warranty issues and outside warranty goodwill claims in the last 5 years. I had a failed starter motor replaced about 2 years outside warranty free of charge, based on very low mileage, but that wouldn't happen now.
 
Hi
I am not aware of any case where changing to a simple K+N sports filter, for example, led to an error code. Above all, the quality of the K+N plate filter is significantly better in my experience!
regards
 
They have to prove the modification you made is the cause of the issues you are experiencing. They can't void the entire warranty.

Example, if you fit a 3rd cat delete and then bring the car in for a leaky shock, your warranty is still valid and they have to replace the shock under said warranty.

At least in the US that is.

That TSB makes sense, if you install an aftermarket cold air intake and you get misfires they can easily link the 2 and refuse repair... Not that I've ever had issues with an aftermarket intake but that's another story.
 

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