Decat and other exhaust pipes to fully take advantage of the cam and BB

[sam2019]

@Sasa brought it up: to get max improvement out of a cam and big bore the cat has to go.

A few questions arise in relation to that proposal:

• do subsequent emission control tests without cat result in a pass?
• can the OEM pipe of the first Hima iteration (BS3 in Indian terms) work as well? should be much cheaper! but will it fit?
• Just changing to a K&M filter is enough for more air flow or do we need to change the entire airbox to be more "free flowing"?
• finally will this be necessary for only the cam or cam + BB or just BB alone?

Opinions?

 

[Sasa]

@Sasa brought it up: to get max improvement out of a cam and big bore the cat has to go.

A few questions arise in relation to that proposal:

• do subsequent emission control tests without cat result in a pass?
• can the OEM pipe of the first Hima iteration (BS3 in Indian terms) work as well? should be much cheaper! but will it fit?
• Just changing to a K&M filter is enough for more air flow or do we need to change the entire airbox to be more "free flowing"?
• finally will this be necessary for only the cam or cam + BB or just BB alone?

Opinions?

Here is my take:

I’ll go in order, following your questions:
1) it hasn’t been tested yet, my advice is to keep the cat pipe and source a new one: for the emission test you can always revert back just for the test to have more certainty you’ll pass.
2) yes it should fit without issues and it’s cheaper there than Delkevic. Delkevic is higher quality and probably on par with BS3 regarding prices here in Europe (including shipping an import)
3) k&m and DNA are excellent choices, provide you install the open flange as well to take full advantage of the higher flow. There is no need to go full airbox delete, although it would improve the flow even further. Airbox delete would be more dangerous for dusty roads or off-road use.
4) it isn’t necessary, but any configuration would take advantage by removing the cat, the more the mods the higher the advantage. I’d say between 1 and 2 hp, depending on your configuration, but also throttle response and engine liveliness would greatly improve.

 

[Dool]

OEM airfilter is more than adequate for most applications, the snorkle needs to be removed
BS3 pipe would be missing the O2 sensor plug ?
People have had the cat removed but retained the restriction because of Muffler choice ( wrong choice IMO ).

 

[sam2019]

No O2 sensor plug means fuelx pro is useless?

 

[Dool]

yes

 

[sam2019]

OK, the part came today - in general it looks high quality (for the price). There are a few improvements I will suggest to the manufacturer:

1. Pipe is a bit thin (bigger diameter = more air flow)
2. the end piece towards the silencer does not have the correct diameter - too big for naked silencer, too small for the RE gasket ring that goes there
3. the attachments for the heat protectors do not have screws welded inside - so the attachments can not be fitted (its an easy fix - if you can weld)
4. the attachment towards the front is ONLY available on the BS3 version - I suggest to add that part to the set so customers do not have to struggle to obtain it
5. It is a tiny bit (1.5cm) too short for a tight fit towards the silencer (not a design problem, that part is covered by a heat shield)
6. Make sure the pipe is fixed in the right (low) angle or the pedal for the rear brake will be blocked by the pipe
7. You have to bend the holder for the clutch cable inwards a bit else the cable will touch the pipe

First impressions: heavy engine popping when closing throttle. Perceivable gain in forward thrust - possibly nearing the carby model's performance, spark plug is a bit too white already so a lean machine got leaner - got to do some adaptions to the mapping (@Sasa - any tips?)

 

[sam2019]

about the popping. google tells me:

If your engine is getting more fuel than it needs, a rich fuel to air ratio is the result. When your car has leftover fuel in the exhaust and the cylinders, that fuel explosively burns and creates a loud popping sound. Specifically, here we mean delayed timing, which causes the backfire.

the fuelx pro is set to 10 which is the richest AF ratio. I will set it to 3 and check if the popping goes away

 

[sam2019]

but then it also tells me:

Popping usually indicates a lean air/fuel mixture, meaning you're getting too much air and not enough gas. The #1 cause is vacuum leaks, followed by exhaust leaks, CIS issues, and finally a misadjusted mixture.

so what the fuck ??!!

 

[Dool]

Less restriction equals greater Flow. Does your muffler have a removable silencer?
First pic , the vertical section of pipe where they put their name, has been extended? The welding makes me feel better about my own

 

[bcrist]

but then it also tells me:


so what the fuck ??!!

Popping or backfire on decel is generally due to an overly lean mixture. Not sure about the science, but many, many jetting changes on carb bikes over the years confirms this in my experience.

 

[Sbinf74]

I finally removed the catalytic converter from the original pipe
I only made one cut, the catalytic converter was removed in pieces , here after wire welding and finally on the bike.
the color of the metal was reproduced using a gas torch.
I used a MAG welder with AISI 304 wire

 

[sam2019]

Looks clean. No emission control where you live?

 

[Sbinf74]

I think that reassembling the original terminal is sufficient to pass the inspection

my exhaust

 

[KTM AL]

I have just cleaned up my exhaust, but before I get carried away and cut it in half to remove the cat, (2019 euro 4) I will have to retain the after market exhaust baffle as it will be too loud for where I live with out it, and probably even louder with the cat removed. So would it be worth removing the cat if I retain the baffle?

 

[sam2019]

I removed the cat on my BS6 euro5 and I do not feel any discernible power increase. but I have a lot of back firing when shutting the throttle, enough for trouble with police if I lived in the west I guess. In India nobody cares luckily.

 

[KTM AL]

Thanks for your reply, I will try the Lextec without the baffle first and see how it goes. Though, I think it barks a bit when I crack the throttle, probably why I left it in.

 

[Dool]

I use a lextec slipped over a Delkovik Header with the reduced section of the header pipe removed, no back firing because it is Fueled correctly.
Its all about the mixture, reducing backpressure increases flow and without extra fuel it runs lean and backfires when you roll back the Throttle.
No Cat but I keep the baffle in except on the Dyno, it is removed to install the O2 sniffer.

 

[sam2019]

Regarding fuel, I did ,in increments, add up to 40% more in PT alone thru the entire rev range plus run fuelx pro on level 10. Still backfiring.

 

[Dool]

Backfire at zero throttle?

 

[sam2019]

It only backfires when closing the throttle quickly. If I do it slowly there is no backfiring.
Also if I rev up in neutral and close, no backfiring either.