Poor performance with DB killer

Raga1000r · Apr 15, 2021

Hello guys hope you're doing great, l recently got a SC project slip-on and also got a universal DB killer which is installed between the midpipe and the can, just like the photos shown:

l'm wondering if this type of DB killer is too restrictive for a 1000cc?? l feel power is ok in the low rpms but in higher rpms and wide throttle the bike doesn't pull, l think this type of DB killer with the cap in the end is extremely restrictive for my bike but l'm not sure what to do, removing it would cause trouble with cops and might be too loud, should l drill holes in the top cap of DB killer or what? Appreciate your help.

WyldCFH · Apr 15, 2021

Over about 10.5k rpm, the stock ecu is restricted. Doesn't matter what you put on it. If you didn't change the headers to get rid of the catalytic convertor, the slip on will do nothing but change the sound as the stock muffler is a straight hole all the way through.

Adding the db killer though will restrict the exhaust flow

Raga1000r · Apr 15, 2021

This is my first try with an aftermarket exhaust, with the stock can the bike is stupid fast, l read somewhere that DB killers doesn't kill performance as they create back pressure and the bike runs rich, but this piece of s**t insert is ruining my rides, the bike runs like a 600cc. l still have the original headers with their header valves and all is OK with the stock, l guess l'll have to ride without db killer, i feel the poor engine is drowning in its own gases

John Dumke · Apr 15, 2021

Raga1000r said:
l'm wondering if this type of DB killer is too restrictive for a 1000cc??

Yes, Yes and Yes. The stock exhaust is straight through. The first photo in your post shows that the insert probably has only 20% of the surface area to flow gas. Just those little holes pass exhaust gas, as the insert completely blocks straight through flow. This style of insert will DESTROY your performance.

What WlydCFH said is true, the ETV (electronic throttle valves) and the cat do provide restrictions. However these restrictions might limit the last 10-20% of your motorcycles performance. Your bike with the insert will never even get close to 80% power to feel the ETV and cat limitations. Yes it would not surprise me if your bike had less power than a 600cc.

The stock exhaust can is huge for a reason. It is quiet, but it still performs. My Akra exhaust also is pretty big and it is quiet, but it is still straight through, so it performs. Especially with full headers and a complete tune.

Exhausts can't be both small and quiet. Your slip on with insert is the worst of both worlds, being both quiet and small. If you want loud, get a SC Project slip on or similarly small exhaust. If you want quiet, get an larger size exhaust can. Personally I prefer quiet power, but many on here like loud.

As a comparison. My Akra exhaust is straight through with no restrictions. The Akra probably has 2-3 times the length of the SC project exhaust can. In addition the amount of packing material around the inner pipe is probably 4-5 times thicker. The akra can be inherently quieter by design with no loss of power. The SC project, fully uncorked will provide little extra power compared to the Akra, but if modified to be quiet will destroy performance.

Quiet:

Loud:

philwoods · Apr 15, 2021

My yoshi alpha t slip on isn’t overly loud. It is a sweet sound and gives a satisfying pop when using the quick shifter under wot. It has a db killer that goes into the end of the can though and not inline. Haven’t noticed any difference in performance. FYI bike is Australian and came from the factory de- restricted.

John Dumke · Apr 15, 2021

philwoods said:
My yoshi alpha t slip on isn’t overly loud. It is a sweet sound and gives a satisfying pop when using the quick shifter under wot. It has a db killer that goes into the end of the can though and not inline. Haven’t noticed any difference in performance. FYI bike is Australian and came from the factory de- restricted.

The Yoshi db killer insert just makes the exhaust a slightly smaller diameter. It is a straight through design. It does not completely block the exhaust and just route the exhaust through small holes like the SC Project exhaust above. A much better design.

Yoshi Insert Info

MrGSXRAl · Apr 15, 2021

My L8 has the Yoshi R11Sq muffler with the db killer (straight through restrictor) in place. Personally, I couldn't tell the difference from the stock muffler when I first put it on.. Along with mufflers and restrictors (in or out) could come the need to alter the mapping to suit to new exhaust/muffler, which may prove even more valuable than anything. As far as I know the Yoshi RS11Sq was built with the standard mapping in mind and therefore needs no alteration, although in the real world it probably wouldn't have hurt. I just love the low grumble it gives the bike...

Al

TwistedMister · Apr 16, 2021

try leaning it out some in the upper range that concerns you, however do not live there...

don't these bikes have multi mapping you can swap on the fly already?

create one map might slightly leaner for when you need that power up top, otherwise use the richer mix so you get more cylinder lube from the gasoline..

what you're experiencing is just a kink in the rabbit hole, you just bounced off the wall.. of course when you clog the can gases cannot escape as quickly therefore the top end suffers..

if this model does not have multiple adjustable maps you can switch on the fly the new power commander does, install dyno jet PC let your dyno guy know your objective.. easy fix, altho you may not experience the same top end output you can get close, again just don't live on that map, gas does act as a slight lubricant when it's thinned out obviously it lubrication suffers slightly..

Raga1000r · Apr 16, 2021

Thank you for your answers, you are really helpful. l really don't want to touch the stock fuel maps. l installed the slip on for better looks and let other vehicles note l'm coming. The stock bike is powerful enough for my needs, so l'm not looking for extra hp, however, l don't want to loose performance either, specially in the low-mid range in which l ride most of the time.

l removed the insert and reinstalled the slip on in the pipe. Now, looks like l've a loss of low-mid range power. As far as l know, the exup valves control most of the back pressure in the system, so l thought raplacing a slip on wouldn't cause any noticeable effect but it does.

MrGSXRAl · Apr 17, 2021

If you really want to know more about how the full stock exhaust actually works, I would urge you go onto 'yutub' and look at Brock Davidson series on tuning the GSXR1000 (there's quite a few videos). Find the one where he explains just how the whole exhaust does its job - it's a fantastic video and explains all you'll want to know. If you simply want to get totally educated on this subject, it's well worth watching. Those exup valves do more than provide back pressures...

Al

Poor performance with DB killer

Raga1000r

WyldCFH

Raga1000r

John Dumke

philwoods

John Dumke

MrGSXRAl

TwistedMister

Raga1000r

MrGSXRAl

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