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Offline hazy

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Keep cat with Austin Racing exhaust?
on: August 05, 2021, 03:18:56 AM
Gonna be expirementing soon, figured I'd see what folks on here thought.

Current setup is a decat factory header and Austin Racing gp3 pipe/silencer (silencer is a very loosely used word here)

Sometimes I get the feeling that the absolute lack of restriction (even with baffle installed) is potentially causing a bit more lean condition than I'd hope, despite the fact that they say no tune required. Maybe it's a bit of hypochondria, but maybe not? I keep reading that the 20+ models are questionable w the fueling after installing an exhaust...

So I ordered a factory header off eBay and I'm going to cut it up for the same setup and just keep the cat installed. Figure that'll help w any leaning out, and potentially quiet things down a bit.

Anyhow, main question is if anyone's run a similar setup? Figure if it completely sucks not a big loss, only out about 100 for the used headers, but I'm thinking that there's potential I'll like and keep the setup

Will do what I can to keep updated here w the results

Offline RobZ900

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Re: Keep cat with Austin Racing exhaust?
Reply #1 on: August 05, 2021, 07:10:29 AM
Or a better option would be to save the 100, and put it toward a tune. Then then bike will be running the best it can and youll know its not lean.
Motorcyclist - noun (moh-ter-sahy-klist)
: a person willing to take a container full of flammable liquid, place it on top of a hot, moving engine and then put the whole lot between their legs!

Online PJ69

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Re: Keep cat with Austin Racing exhaust?
Reply #2 on: August 05, 2021, 08:25:55 AM
*Originally Posted by hazy [+]

despite the fact that they say no tune required.

Every time I read something like this, I ask myself What is the motivation of the writer? In this case, for me, if they wrote re-map needed theyd reduce their potential customer base, and Id be prompted to ask for the data that made them come to that conclusion. Most likely, their answer would be we run it and no lambda errors come up so the mixture & exhaust must be fine / within manufacturers tolerances or something similar.

The government cannot give anything to a person it has not first taken from someone else.

Offline Cazzy_R

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Re: Keep cat with Austin Racing exhaust?
Reply #3 on: August 05, 2021, 08:35:52 AM
*Originally Posted by hazy [+]

......ordered a factory header off eBay and I'm going to cut it up for the same setup and just keep the cat installed. Figure that'll help w any leaning out, and potentially quiet things down a bit.

Anyhow, main question is if anyone's run a similar setup? Figure if it completely sucks not a big loss, only out about 100 for the used headers, but....

 The Race-fit pipe is a similar arrangement to the Austin Racing.
 There are actually 2 cats in the BFO pipe and the Race-fit retains just the front one.
 Ras had one.




 
Last Edit: August 05, 2021, 08:47:14 AM by Cazzy_R
Tighten it 'til it strips then back it off half a turn.

Offline hazy

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Re: Keep cat with Austin Racing exhaust?
Reply #4 on: August 05, 2021, 05:02:52 PM
ok sweet that's good to know, thanks!!

Guess what i'll do is just make the cut and install it with both cats in place, and then I can drill one out if I feel like it.

Main thing I'm looking for is to smooth out the throttle some.  It's not exactly "snatchy" like some on here have described, but I do think it can be quite "on/off" at certain RPMs/loads (generally 2-3k rpm under low loads, like 2nd @ 25mph, for example), and even though I only had about 200 miles on it when I put the exhaust on, I feel like it was smoother in those RPMs w the stock setup.  So my thought process is that if I toss the cats back in then it'll help richen the mixture a bit and potentially help resolve that low load, low rpm twitchiness.  Maybe not, but for 100$ it might give me some peace of mind to know that I'm not gonna lean out the motor and burn a ring/piston/valve

Wish I had time to get to a dyno for an AFR check just to see where it stands with the gutted factory header on the current setup, bc there appears to be alot of disagreement on whether the 20+ models need a tune after a full system.  Obviously it'd be ideal to get one if for no other reason than to maximize the change, but would definitely be good to know how it responds to an exhaust with no tune vs the 17-19 models.

Hopefully the "new" used factory pipe will be here soon, so I'll get to chopping it up and swapping out as soon as I can, and report back!


Offline Its about speed

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Re: Keep cat with Austin Racing exhaust?
Reply #5 on: August 05, 2021, 07:08:36 PM
Tuned exhaust 101.  :440:

We've already experimented for more than 100 years on motorcycle exhausts. What's the odds you'll discover something new?

Do you know how a 2 cycle expansion chamber works? How about a 4 into 1, 4 cycle header? It's called vacuum. It "sucks" the exhaust out and the fuel in. It's rpm adjustable by how it's welded up. The diameters and lengths are critical.

The Z900 ECU can tune the air fuel mixture within engineered parameters. If your after market exhaust over scavenges the combustion chamber, lean over heating and detonation arrives. Pre-ignition is an engine killer.

In today's world motorcyclists ought to experiment on a chassis dyno. Nobody gets hurt and the errors can be avoided.

Our Z900 in OEM tune produces enough power to remove your leg at the knee joint.  :005:

Last Edit: August 05, 2021, 07:11:06 PM by Its about speed

Offline hazy

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Re: Keep cat with Austin Racing exhaust?
Reply #6 on: August 05, 2021, 08:45:55 PM
*Originally Posted by Its about speed [+]
Tuned exhaust 101.  :440:

We've already experimented for more than 100 years on motorcycle exhausts. What's the odds you'll discover something new?

Do you know how a 2 cycle expansion chamber works? How about a 4 into 1, 4 cycle header? It's called vacuum. It "sucks" the exhaust out and the fuel in. It's rpm adjustable by how it's welded up. The diameters and lengths are critical.

The Z900 ECU can tune the air fuel mixture within engineered parameters. If your after market exhaust over scavenges the combustion chamber, lean over heating and detonation arrives. Pre-ignition is an engine killer.

In today's world motorcyclists ought to experiment on a chassis dyno. Nobody gets hurt and the errors can be avoided.

Our Z900 in OEM tune produces enough power to remove your leg at the knee joint.  :005:

Not sure I get what you're trying to say here...well aware of how engines function with regards to tuning and header length/diameter.  My experience has mostly been with GM's LS motors, but I've had motorcycles for going on 20 years now and have tinkered about with them, as well.  The operating theory of an engine is not a foreign concept.

I don't think I'm looking to discover anything new, I'm merely trying out a few things that I think will (probably) help the bike run better on the OEM tune.  I don't have a tuner local to me, and I don't have the desire to pull the ECU and send it out for remapping, thus I'm looking to play around with a setup within the means that I have available.  By putting on a wholly open exhaust with the setup that I currently have, my gut feeling is that the bike is running a bit leaner than desirable, and the OEM tune may not be able to adjust enough to compensate.  Now, I don't want to say that with certainty, as getting on a dyno to check AFR is the only true way to tell.  But there are other indicators that one can sometimes "feel".  Perhaps I'm being a bit of a mechanical hypochondriac here, however it wouldn't be unreasonable to find out that the bike is actually running a bit too lean with a wide open exhaust.

Therefore, I'm gonna chop up this "new" header, leave the cats in, and see how I like it.  Nothing ventured, nothing gained, and if it helps what I feel is a bit of an issue, then my solution works!  If nothing changes, then no big deal, I blew 100$ and a bit of time.  I've spent far more time and money on WAYYYY more stupid things in the past hahaha

Either way, with no time to get to a dyno, and no desire to pay for it even if I could, I think I'll be fine just messing around here. 

Here's a link to my last ride, if you're interested...416ci LS3 stroker with a few goodies bolted on.  It was a fun ride :)

Offline Its about speed

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Re: Keep cat with Austin Racing exhaust?
Reply #7 on: August 06, 2021, 01:18:47 AM
"Gonna be expirementing soon, figured I'd see what folks on here thought."

I think you're on to a good idea now that I know about your skill sets.

"I don't think I'm looking to discover anything new, I'm merely trying out a few things that I think will (probably) help the bike run better on the OEM tune."

Without the emissions the Z900 should run considerably better at low to medium rpm.

Will the OEM adjust enough for Colorado elevation and an unrestricted exhaust? Yikes!
We both know the OEM tune is lean for emissions. How close to the edge is my concern.
I would dial back some ignition timing until I got the AFR squared away.

I think mechanical hypochondria is entirely acceptable behavior.

Offline hazy

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Re: Keep cat with Austin Racing exhaust?
Reply #8 on: August 06, 2021, 04:18:53 AM
We shall see! Even if it turns out to be just chasing ghosts, it'll give me something to mess around with for an evening or two with some brews after the kids hit the sack

Offline hazy

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Re: Keep cat with Austin Racing exhaust?
Reply #9 on: August 10, 2021, 12:22:11 AM
Welp. Got everything swapped out today. The pipes I ordered we're looking not too hot, so spent a couple hours polishing them up with solid results.

As for the way it runs- noticeably smoother in the ranges I was looking to improve (2nd gear, 20-25 mph, around that 2-3k rpm range)

I kept both cats in, and I'm thinking the bike was definitely a tad lean on the factory tune with gutted everything and straight thru pipes. Maybe at lower elevations it'd be fine, but I'm near Denver and regularly get up to 10k feet on rides they the mountains.

Haven't gotten it out for a real test, just a quick jaunt thru the neighborhood w my lil kids on the back, but if that's any indicator, I think I'll feel much safer ripping on it now, esp at the higher altitudes

The sound is a tad more mellow, but is definitely less raspy than before. So far I'm digging it. Will report back after I get a chance to run thru the mountains next weekend

So I guess the experiment was successful so far.
Last Edit: August 10, 2021, 12:24:16 AM by hazy