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| MrChain | | Set |  | | Reg. Date | : | 17/12/2009 | | Posts | : | 21 | | Location | : | Australia |
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| | Posted : 15 May 2010 - 07:39 Post title : Angle for home made cat bypass | | | Just bought a length of stainless and made (tried to at least) a cat bypass same as the Staintune one. I bent the pipe to 30 degrees where it is supposed to join with the TORS pipe, but this was not enough and I will have to put a further bend in it. Does anyone who has already made a cat bypass recall the correct bend angle at the TORS end? (By the way the cost for 1.2 metres of 38mm or 1.5 inches stainless was $36).
Please help.
Mr Chain.
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| tbird1600 | | Set | |  | | Reg. Date | : | 10/04/2010 | | Posts | : | 39 | | Location | : | Ozztralia, NSW, Australia |
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| | Posted : 15 May 2010 - 07:48 Post title : Re: Angle for home made cat bypass (Re: MrChain) | | | About 40 deg mate..
I took my cat to an exhaust joint and they supplied and bent up 2 x 1.5 inch pipes I used plain old mild steel pipe as you dont see any of it once the shields are in place
Jono
| | If it aint broke don't touch it :>
Mods>Taller Tbars, BC Hog slayers, Unifilter
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| MrChain | | Set | | | Reg. Date | : | 17/12/2009 | | Posts | : | 21 | | Location | : | Australia |
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| | Posted : 15 May 2010 - 08:36 Post title : Re: Angle for home made cat bypass (Re: tbird1600) | | | Thanks for that. 30 degrees didn't cut it, so will have to take a sickie Monday  he he he and get the job done to 40 degrees. With the bypass and TORS in place it should be pretty loud. Hoping to gain some HP and torque of course but that will be just a bonus.
Cheers,
Mr Chain.
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| mat1600 | | Thunderbird | |  | | Reg. Date | : | 06/03/2010 | | Posts | : | 8,596 | | Location | : | Bridlington, Democratic Independant State of Yorkshire, United Kingdom |
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| | Posted : 15 May 2010 - 08:38 Post title : Re: Angle for home made cat bypass (Re: MrChain) | | | Do you need a change of tune for that mod.
| My first natural instinct is to breathe. My second is to evade tax's.
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| MrChain | | Set | | | Reg. Date | : | 17/12/2009 | | Posts | : | 21 | | Location | : | Australia |
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| | Posted : 15 May 2010 - 09:19 Post title : Re: Angle for home made cat bypass (Re: mat1600) | | | Well last week I had the bike dynoed and and A/F mixture evaluated. It was running rich with the TORS tune. The dyno shop said that the bike would benefit from having the snorkel removed and the cat removed. So I have removed the snorkel (the rubber ring that sits over the air filter housing) and will shortly install the cat bypass. I suspect that those mods will not casue me any major issues.
Cheers,
Mr Chain.
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| mat1600 | | Thunderbird | | | | Reg. Date | : | 06/03/2010 | | Posts | : | 8,596 | | Location | : | Bridlington, Democratic Independant State of Yorkshire, United Kingdom |
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| | Posted : 15 May 2010 - 10:08 Post title : Re: Angle for home made cat bypass (Re: MrChain) | | |  Could you keep us posted on this issue. 
| My first natural instinct is to breathe. My second is to evade tax's.
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| tbird1600 | | Set | | | | Reg. Date | : | 10/04/2010 | | Posts | : | 39 | | Location | : | Ozztralia, NSW, Australia |
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| | Posted : 15 May 2010 - 10:28 Post title : Re: Angle for home made cat bypass (Re: MrChain) | | | What sort of numbers was the Dyno showing
| | If it aint broke don't touch it :>
Mods>Taller Tbars, BC Hog slayers, Unifilter
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| MrChain | | Set | | | Reg. Date | : | 17/12/2009 | | Posts | : | 21 | | Location | : | Australia |
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| | Posted : 15 May 2010 - 11:07 Post title : Re: Angle for home made cat bypass (Re: tbird1600) | | | Well it was a hot day 27 degrees and there was a lot of smoke in the air from backburning in the Blue Mountains but the bike showed 65 hp at the rear wheel and 88 foot pounds of torque. With the snorkel removed it went to 68 hp and torque went up to 89. I got them the install the BB tune, but this did not work at all so went back to the TORS tune. On a cooler day with no smoke in the air eating up the availabel oxygen, I should be pulling better numbers.
Cheers,
Mr Chain.
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| tbird1600 | | Set | | | | Reg. Date | : | 10/04/2010 | | Posts | : | 39 | | Location | : | Ozztralia, NSW, Australia |
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| | Posted : 15 May 2010 - 11:21 Post title : Re: Angle for home made cat bypass (Re: MrChain) | | | Cool i've just fitted some BC pipes no cat with K&N running the TORs tune 2 days ago
| | If it aint broke don't touch it :>
Mods>Taller Tbars, BC Hog slayers, Unifilter
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| MrChain | | Set | | | Reg. Date | : | 17/12/2009 | | Posts | : | 21 | | Location | : | Australia |
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| | Posted : 15 May 2010 - 12:35 Post title : Re: Angle for home made cat bypass (Re: tbird1600) | | | What are your thoughts on that open set up T-Bird?
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| MrChain | | Set | | | Reg. Date | : | 17/12/2009 | | Posts | : | 21 | | Location | : | Australia |
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| | Posted : 23 May 2010 - 06:38 Post title : Re: Angle for home made cat bypass (Re: MrChain) | | | Installed the cat bypass with Short TORS. Man what a noise. When I made the bypass I had an angle bend as opposed to a mandrel bend put in it so that the pipe would be compressed somewhat to create some additional backpressure. Well this worked well with no loss of torque and the thing reved much freer.
One of the problems though was the noise. Just a little toooooo much. Tried it with the standard pipes but still too quiet.
In addition I noted a lot of decel popping. When I had the bike dynoed the other week the A/F mixture was 13:1 up to about 4000 rpm after which it fell to 12:1 and below the closer it got to 6500 rpm. The decel popping suggests to me that with the open set up and no shroud over the filter the bike is running too lean. Fast but lean, which is no good for long term longevity.
If you guys are considering making any cat bypass I would suggest that you need to ensure some restriction in the bypass to retain low end torque. I might try as Keets seems to have done, the 1700 tune. This does not work on a 1600 with CAT (already tried it) but Keets seems to report good results with his home made cat bypass and 1700 tune.
Keets, any views on that, especially the decel popping with open set up and 1700 tune?
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| FTL40 | | Jupiter | |  | | Reg. Date | : | 13/10/2009 | | Posts | : | 1,122 | | Location | : | massachusetts, United States |
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| | Posted : 23 May 2010 - 20:26 Post title : Re: Angle for home made cat bypass (Re: MrChain) | | | what was your hp and tq from the dyno?
| 2010 tbird 1700 silver (fastest color) BC exhaust, BC airbox removal
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| DizzE | | Thor | |  | | Reg. Date | : | 12/07/2010 | | Posts | : | 3,141 | | Location | : | Sunnyvale, CA, United States |
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| | Posted : 03 Nov 2010 - 13:28 Post title : Re: Angle for home made cat bypass (Re: FTL40) | | | not sure what happened to McChain....having too much fun, I suppose. It's an interesting thread. More relevant than ever.
We can map fuel to these experimental mods and make some objective measure of results.
So, it seems to be all about gas flow. You don't want back-pressure. That would give reversion of the exhaust gases into
the fresh charge. But, you do want a depression wave that reflects back up the exhaust to the opening of the intake valve.
Ideally, a positive pressure wave runs into the cylinder from the Induction side also, just as the intake valve opens. That
avoids exhaust reversion up the intake side. Gases can go in the wrong direction and are controlled somewhat by pressure waves.
How much control? As usual, not 100% and subject to hi/low rev compromise.
Yeah, a tuned system is doing a lot of compromise work about wave tuning. But wait there's more. Waves
are acoustic, but the gas vol still has to exit the system. This is why Short pipes work better, seems to me. It seems most of the
pressure reflection is happening at the crossover. H-pipes, Y-pipes, X-pipes. We have H-pipes. After the cross-over it's
all about flow, I think. Shorts get the exhaust gas out better at the low rpm and don't restrict much at higher rpm.
I'm trying to figure a easy, cheap, fast way to measure the flow restriction of the cat by using a shop vac and measuring
velocity change.
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| mag10 | | Set | |  | | Reg. Date | : | 05/02/2010 | | Posts | : | 485 | | Location | : | Wisconsin, United States |
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| | Posted : 03 Nov 2010 - 16:44 Post title : Re: Angle for home made cat bypass (Re: DizzE) | | |
DizzE wrote:
Yeah, a tuned system is doing a lot of compromise work about wave tuning. But wait there's more. Waves
are acoustic, but the gas vol still has to exit the system. This is why Short pipes work better, seems to me. It seems most of the
pressure reflection is happening at the crossover. H-pipes, Y-pipes, X-pipes. We have H-pipes. After the cross-over it's
all about flow, I think. Shorts get the exhaust gas out better at the low rpm and don't restrict much at higher rpm.
I'm trying to figure a easy, cheap, fast way to measure the flow restriction of the cat by using a shop vac and measuring
velocity change. |
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I am working on my cat less set up right now. I measured the differential flow thru the cat using my carb balancer and the shop vac. the values are relative, but I am seeing a 1/2 inch of fluid column difference from one side of the cat to the other. As there appears to be flow alround the inside of these cats, I check both inlet and outlet on the same side and diagonaly (block off the openings not being tested at the time) the same delta for both ways.
I have designed a simple cartridge unit to slip into the pipes that replace the cats piping to restore or be slightly less restrictive than the cat was. Differential measurements will be made with the same set up as the cat.
Before anybody gets upset and points out that I can't make torque or hp by restricting the exhaust, I know. I would prefer to address the apparent loss of low end power with a tuning solution but I do not have that yet. A large part of my interest in building this cat by pass is the have a place to put the wide band O2 sensors so I can track A/F changes. I figure that restoring the stock back pressure is the best way to determine a base line.
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| DizzE | | Thor | | | | Reg. Date | : | 12/07/2010 | | Posts | : | 3,141 | | Location | : | Sunnyvale, CA, United States |
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| | Posted : 03 Nov 2010 - 17:12 Post title : Re: Angle for home made cat bypass (Re: mag10) | | | I knew there were projects going on.  Thanks for sharing. Lost of thoughts here.
1 inch of water or Hg? Big difference. The gold standard for flow testing, I imagine you know,
is a readin of 28" of Mercury. Why? That took a lot of digging, but here 'tiz.
When you do the conversions you need a reference to get to CFM. Standard pressure, , 29.92 "Hg 14.7 lbs/sq in.
but also, mili-bars, micro-pascals choose your poison.
If you do the math 13.7 psi = 28" Hg. If you can pull down 1 psi of vac. then CFM is easy to calc.
But, can't get that with a shop vac. There are also big boiler gauges that can read smaller drops.
You can find them on ebay. You drill and tap places, in the airbox, for example, to see what the
dynamic running pressures are. But, not for a cat I guess.
I just wonder why you'd put anything back to replace the cat box. You would just be simulating
a baseline. Catless and base tune is a baseline.
Are you going to place your WB that far back in the exhaust stream? I was thinking about the
crossover for 1 WB. Reading both cylinders, but still well before any outside air contamination
from the back pressure.
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