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OK, so we finally got around to doing a full end to end test relating to the removal of the cat from a Thruxton 1200R, and documented each of the changes, with dyno runs and full A/F measurements.
I'll be posting a full report on it all soon, but I've left the preliminary document with a tuning specialist to check all the facts and correct any mistakes I've made. That will be a more complete account of the fun, but I'll post the "too long, did not read" version here.

The bike was a 2,500km Thruxton 1200R, with no modifications for the first dyno runs. The dyno was Platinum Motorcycles in Victoria (http://platinummotorcycles.com.au/) where they have a DynoJet dyno and do lots of race bike tuning. We explained that the reason this was being undertaken was to document both the default state of tuning on a standard Thruxton 1200, and the effect that changes such as de-cat and slip-ons made to factors such as A/F, performance, and responsiveness.



We were sent down a cross-pipe from Meerkat to perform these tests, and Peter Herrington also sent down a set of his race slip-ons to use during the test runs. It was made clear that the results would be released even if we discovered issues, and he was perfectly happy to accept that. The products arrived the next day, and the quality of finish on these was stunning, particularly given they were hand-made. This is not a plug for Meerkat by me, but a recognition of incredibly impressive workmanship.



So... here is the first dyno run from the stock bike. The idle/cruise/gentle throttle (in closed loop) recorded an A/F of 14.8, as expected, and this shows the AF mixture, going slightly rich, then slightly lean (from a power perspective, not relative to stoich) in the midrange, then over-rich at the top end.
So this is the baseline for a typical Thruxton 1200. Not at all lean during idle and cruising, which is where lean running would be a concern for engine longevity, and only slightly non-optimal over the full rev range (A/F 12.6-13 is ideal for power. 14.7 is ideal for efficiency)



Next was to fit the decat (or decat the bike?). This was about 2 hours work, not all that tricky (particularly with @Fenech doing most of the work!), and the Meerkat unit which looks like a work of art, fitted perfectly. I thought I'd also mention that the frame bolt everyone complains about is extremely easy to reach from above with a 14mm ring-spanner, so I'm not sure what all the fuss is about.

So here's the cross-pipe fitted, with the shield removed from the engine to tidy things up:



Back to the dyno with the OEM pipes still fitted, and we plotted the best standard run against the best decat-run:



As you can see, there was a huge increase in torque over the entire rpm range. This is an average of about 7% increase, from off-idle all the way to the rev limiter!
Awesome stuff, and very noticeable when you're riding. The low-end pickup is stronger, without the slightly hesitant feel you get from standstill if you don't slip the clutch enough, making the feel more relaxed.
Remember this is across the whole rpm range, not just the top-end, so the bike accelerates 7% faster from opening the throttle all the way to changing up, and the bike feels as though the sports mode is on because you get the same power by throttle position in standard mode. In sports mode it's even more impressive!

So what about the dreaded A/F ratios? Well you can see from the chart that it is about 2% leaner (as expected, there's a less restrictive gas-flow), but it is still far below lean. The idle/cruise closed-loop remained unchanged at 14.8, indicating that the ECU loop has no issue adjusting, and the open-loop tables in the ECU are rich enough for it to simply not be an issue at all.

OK, so the final step... what happens when the slip-ons are added? I honestly predicted this would make no difference, as the OEM can is relatively open with some mild 'waffling'.
Well here's the chart comparing OEM to the Meerkat cans:



What's happened is that the torque has shifted slightly down, probably because the slip-ons were shorties which tend to increase low torque at the expense of top end torque.
What's also interesting is that the A/F ratio has increased again by about 2%, suggesting the mild-mannered OEM cans do actually have more impact than expected, probably because of the cat removal.
In spite of all this, it's still perfectly within safe tolerances, but it does demonstrate that there may be more airflow restriction at the filter side, but any additional changes will probably need a mixture adjustment to keep the mid-range A/F more optimised.
The tuning specialise at Platinum estimates an additional 6-8hp should be achievable simply by resolving the factory fuelling instability, keeping it at a constant 13ish across the whole range. If this is so (and that might be the next project) it will mean an additional 13-16% power across the spectrum.

So here's the finished setup. I left the shorties on because I like them a lot. Guess I'll have to change address so Peter at Meerkat can't find me to ask for them back.





Oh, and finally... noise (or sound, if you prefer)
In short summary;
Decat with the OEM exhausts is still very socially acceptable. Popping is slightly louder, but not very loud. The bike sounds like it should have done from the factory, like a highly-tuned twin with road-legal mufflers.

Now decat with the slip-ons is another story. This setup is for the men, not the boys! It's not harsh or crackling like a Harley, but on idle it sounds like a classic 2-stroke, with a burble and throaty sound that is awesome.
Opening the throttle wide makes a real powerful roar. Again, not horrible and painful like Harley pipes, but more like a performance tuned rally car roaring past you, and personally I think it sounds wonderful.
Overrun definitely introduces popping, which can be stopped by pulling in the clutch, but again I like it. It tends to be more a set of small crackles than bangs, whereas the slash-cuts I used to use with the cat gave much louder 'pops'.

So in summary, for me the bike is now really quite awesome. The power increase is very noticeable and makes the throttle response much nicer, the sound may be 10% louder than ideal for me but I just don't care, and I feel the appearance is vastly improved by removal of the dual whales and replacement with beautifully engineered hand-made mini versions of classic pipes.

Sorry the TL;DR ended up so long, but after spending all this time and money researching I want to make sure I get as much info out there as possible.

Please feel free to post questions, and I'll be sure to include a link to the full report once the tuning specialist has corrected all my misinterpretations


As an actual plug in gratitude to Peter at Meerkat for his provision of the decat, you can call him directly on (07) 5482 7553, or email him at [email protected]
He's got more pictures of decats, including black ones (for you 'I want it all black' nutters), on his website at http://meerkatmufflers.com.au/

Make sure you allow ample time because Peter likes to discuss in detail, and you won't get away until he knows exactly what it is you want constructing, but when it arrives it's well worth the wait!
So, based on this, just removing cat with x-pipe gives the bike 7% more torque so all of the people who say their bikes "run like crap" after doing it is incorrect. And there was no map change.
 

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So, based on this, just removing cat with x-pipe gives the bike 7% more torque so all of the people who say their bikes "run like crap" after doing it is incorrect. And there was no map change.
Jsobells write up was pretty clear jd...bike runs great no remapping. I've read nowhere about bikes running poorly except for when people have punched the guts out of the standard cat

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Even if I never install it, could not pass it up... ordered! It was US$85.00 + 29.00 for shipping
It is a really good deal at that price. BC and Freespirits are much more expensive. Too bad they didn't have more parts you needed, I think shipping is a flat rate. Should take about 2 weeks to get to you
 

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Discussion Starter #28
They don't have to be independent, usually they are connected with a balance pipe.

Example from euro racing in bangkok:
...
The reason we undertook this whole experiment was to separate opinion and assumption from facts and measured results.

Once we see someone go through the same before/after process with detailed dyno and A/F measurements on these replacement headers, we'll know if the idea of independent pipes works, and if the balance pipe makes any difference.

My guess (and it is a guess based on common sense and some experience) is that the balance pipe shown in those photos will have little effect when there is any volume of exhaust gas present. The difference between a 90° balance pipe joint and the 0° join of a cat eliminator is huge. I can imagine the balance-pipe shown creating a low level Venturi effect at high RPM, much like the tiny balance pipe on the OEM headers, but with even less effect given the long length and diameter of the pipe. The cat eliminator essentially runs the two exhaust paths parallel acting largely as a 2-1-2, which was the effect the original cat had.

Who knows? If you're buying some of these headers, do it properly and get professional dyno runs before and after. I'm a little sceptical as I've seen nothing professional released regarding the results of these, but if all you want are titanium pipes and brag factor, go for it.
The existing torque curve on these bikes is very nice. The Meerkat decat retains that curve but shifts it up in its entirety, which I find perfect because it eliminates power-bands.
My guess is that removing all that cross-flow is going to affect something, and as a wild guess I'd say you'll get a different torque curve and I wouldn't be surprised if it turns out to be a lot more bumpy with bands, but I'll be fascinated to see it.

Even re the cross-pipe, other manufacturers may or may not match our results. The fact that they all have four more welds than the Meerkat in the path may or may not affect it as they will all have slightly different cross-flows. My results only relate to the Meerkat brand of cross-pipe, so if you're fitting another brand please post your before/after dyno results so we can see how they compare.
 

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I was just looking at the Meerkat & the Moto-Trio x-pipes....It looks to me like the Moto-Trio pipe is a plated steel tube where as the Meerkat is Stainless Steel. The Meerkat also has fewer welds, simpler construction and maybe more balancing area where the two pipes meet. Might be part of the reason the Moto-Trio is cheaper. I am thinking of going the Meerkat route with the SS tube. Glad to see there are finally some measured results.
 

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Wasn't there a discussion (maybe a rumour) going around about the oxygen sensor on non-US Thruxtons being wideband allowing the ECU to tune itself while North American Thruxtons didn't have the self tuning capability due to narrowband O2 sensors? I wonder if that was ever proven or disproven?
I remember searching for information about the 02 sensors on these bikes when I found out about the full systems and what appears to be a lack of 02 sensor bungs on the headers, I couldn't find any info, perhaps that is true.
I have a US bike so am I going to have AF problems?

I was just looking at the Meerkat & the Moto-Trio x-pipes....It looks to me like the Moto-Trio pipe is a plated steel tube where as the Meerkat is Stainless Steel. The Meerkat also has fewer welds, simpler construction and maybe more balancing area where the two pipes meet. Might be part of the reason the Moto-Trio is cheaper. I am thinking of going the Meerkat route with the SS tube. Glad to see there are finally some measured results.
I talked to Moto Trio today and they told me their part is stainless. I'm ordering it.
 

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Discussion Starter #32 (Edited)
I'm sure the Moto-Trio units are fine, although I think they look strangely 'cheap' - have they chromed the stainless steel? Why do they have those weird triangular braces?

The Meerkat design uses 42mm pipe (1.7") instead of the other brands' 38mm (1.5"). This meant a more complex weld between the clamp fittings and the U-pipes, but meant that the U-pipe intersection was larger and more open, and the volume much greater to more closely match the expansion features of the original cat and encourage the system to be more flowing and less turbulent, and removes the need for an additional welded extension in the middle.
The other cross-pipes, X-pipes, decat, etc are all using 1.5" pipe, which equates to 20% smaller (or 100cc of expansion space) in terms of volume.

Does it make a huge difference? I have no idea, but it's another variable worth bearing in mind in the quest for more power.
 

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I'm sure the Moto-Trio units are fine, although I think they look strangely 'cheap' - have they chromed the stainless steel? Why do they have those weird triangular braces?

The Meerkat design uses 44mm pipe (1.75") instead of the other brands' 38mm (1.5"). This meant a more complex weld between the clamp fittings and the U-pipes, but meant that the U-pipe intersection was larger and more open, and the volume much greater to more closely match the expansion features of the original cat and encourage the system to be more flowing and less turbulent, and removes the need for an additional welded extension in the middle.
The other cross-pipes, X-pipes, decat, etc are all using 1.5" pipe, which equates to 25% smaller in terms of volume.

Does it make a huge difference? I have no idea, but it's another variable worth bearing in mind in the quest for more power.
Now that you say it, I agree that it looks a little cheap and weird. I have asked for more specs.

About my question regarding havinga US bike, do you think it will cause any problems?
 

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I'm sure the Moto-Trio units are fine, although I think they look strangely 'cheap' - have they chromed the stainless steel? Why do they have those weird triangular braces?

The Meerkat design uses 44mm pipe (1.75") instead of the other brands' 38mm (1.5"). This meant a more complex weld between the clamp fittings and the U-pipes, but meant that the U-pipe intersection was larger and more open, and the volume much greater to more closely match the expansion features of the original cat and encourage the system to be more flowing and less turbulent, and removes the need for an additional welded extension in the middle.
The other cross-pipes, X-pipes, decat, etc are all using 1.5" pipe, which equates to 25% smaller in terms of volume.

Does it make a huge difference? I have no idea, but it's another variable worth bearing in mind in the quest for more power.
Now that you say it, I agree that it looks a little cheap and weird. I have asked for more specs.

About my question regarding havinga US bike, do you think it will cause any problems?
Already got an answer from moto trio and it looks like 36mm
 

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Discussion Starter #36
Now that you say it, I agree that it looks a little cheap and weird. I have asked for more specs.

About my question regarding havinga US bike, do you think it will cause any problems?
The only difference between US and European models is the removable baffle in V&H after market pipes, and some strange undocumented difference in the cat (they have a different part number), none of which is related to a decat.
The US and non-US models all use the same tune. Everything you read about wide band sensors on US models is twaddle.

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Now that you say it, I agree that it looks a little cheap and weird. I have asked for more specs.

About my question regarding havinga US bike, do you think it will cause any problems?
The only difference between US and European models is the removable baffle in V&H after market pipes, and some strange undocumented difference in the cat (they have a different part number), none of which is related to a decat.
The US and non-US models all use the same tune. Everything you read about wide band sensors on US models is twaddle.


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Great. Thank you.
 

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Discussion Starter #38 (Edited)
Moto trio
:) Well they're measuring the size of the clamp points rather than the body of the pipe, but you can see it's a straight path so they are obviously using 1.5" pipe for the bends.

What's really weird is the British Customs version of the cross-pipe, where they don't even bother with the V-clamp! They have some weird thing where you clamp a straight piece of pipe with a T-clamp. I don't know how you are supposed to get a proper seal with this setup, and it's also 1.5" throughout.



Until I see someone testing the system with the thinner pipes personally I'm recommending the Meerkat. It's cheaper than all but the Moto-Trio, and is the only 1.7" model.
 

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The reason we undertook this whole experiment was to separate opinion and assumption from facts and measured results.

Once we see someone go through the same before/after process with detailed dyno and A/F measurements on these replacement headers, we'll know if the idea of independent pipes works, and if the balance pipe makes any difference.

My guess (and it is a guess based on common sense and some experience) is that the balance pipe shown in those photos will have little effect when there is any volume of exhaust gas present. The difference between a 90° balance pipe joint and the 0° join of a cat eliminator is huge. I can imagine the balance-pipe shown creating a low level Venturi effect at high RPM, much like the tiny balance pipe on the OEM headers, but with even less effect given the long length and diameter of the pipe. The cat eliminator essentially runs the two exhaust paths parallel acting largely as a 2-1-2, which was the effect the original cat had.

Who knows? If you're buying some of these headers, do it properly and get professional dyno runs before and after. I'm a little sceptical as I've seen nothing professional released regarding the results of these, but if all you want are titanium pipes and brag factor, go for it.
The existing torque curve on these bikes is very nice. The Meerkat decat retains that curve but shifts it up in its entirety, which I find perfect because it eliminates power-bands.
My guess is that removing all that cross-flow is going to affect something, and as a wild guess I'd say you'll get a different torque curve and I wouldn't be surprised if it turns out to be a lot more bumpy with bands, but I'll be fascinated to see it.

Even re the cross-pipe, other manufacturers may or may not match our results. The fact that they all have four more welds than the Meerkat in the path may or may not affect it as they will all have slightly different cross-flows. My results only relate to the Meerkat brand of cross-pipe, so if you're fitting another brand please post your before/after dyno results so we can see how they compare.

Thank you for the explanation.

My uneducated guess was that a less complex system (a straight through pipe) would yield better results. Also, I'm keen on the weight savings as well as the aesthetics of the titanium headers.
But your point seems valid to me and I will hold off till we see some concrete results.
 
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