High flow cats Vs. Fully catless X pipe? Torque loss :(

[that_grey_m3]

How much increase of HP is there from deleting the 200 cell secondary cats? Right now I am fully catless, but I notice their is a very noticeable torque loss from low to mid range rpms. For instance, I was going up a hill in 5th and 6th gear at 2700 rpm and i tried to give it more gas and my engine bogged and throttle did not move only bog.

I know a tune will fix this issue, but would I be able to gain more useable torque from a set of high flow cats? That way with a tune I will have even more torque. If there is no great power loss from putting on 200 cell high flow cats I may opt for this.

[Yoko22R]

Why not downshift to a lower gear?

[that_grey_m3]

Originally Posted by Yoko22R

Why not downshift to a lower gear?

I do, just comparing to when I was on stock X pipe. 6th gear up a hill never bogged rpms gradually climbed. If secondary cats only take 5hp id be more than happy to put them back on as it does not make a difference to me..

[strokemycocktus]

I have noticed the same with my catless ESS x-pipe and it was visible on a dyno graph as well.
I have asked one of the members who has a HFC version of this x-pipe and he said there was no torque drop with that setup, so I will be adding casts to mine soon. This x-pipe however has 200 cell cats in the primary section, don't know how having them in secondary would change it.

[that_grey_m3]

Originally Posted by seevin

I have noticed the same with my catless ESS x-pipe and it was visible on a dyno graph as well.
I have asked one of the members who has a HFC version of this x-pipe and he said there was no torque drop with that setup, so I will be adding casts to mine soon. This x-pipe however has 200 cell cats in the primary section, don't know how having them in secondary would change it.

After some researching and reading on the forum, the gain from secondary cat delete is little to nothing (5whp at most). For the sacrifice of useable low end torque for daily driving, I am more than happy to give that up! my magna flow high flow cats arrive this Thursday and I will be getting them welded on to my BimmerWorld X Pipe in the next week.

Also, I read somewhere that placing them in the primary section can rob some power as it can restrict flow since its so close to the headers and it needs more space. But I talked to another guy who welded them in the same place and he did not notice any power difference from the butt dyno. I will be placing my HFC in secondary section.

[strokemycocktus]

I was following the thread you are reffering to.
I don't think you will see as much as 5hp difference with secondary cats - any x-pipe (catless or hfc) gains are pretty much the same as test pipes on NA cars from what I noticed reading people's dynos.
To me the smell and sound quality are the most important and I can give up these few hp, even if there is any actual loss. Also this is the way ESS originally made this x-pipe (cats in primary) so I will follow their idea.
Catless smell was unbearable to the point I put the stock x-pipe back until i cat the ess one lol. And the rasp made it sound a bit cheap
I have seen a few threads comparing test pipes or catless setups vs primary catted x-pipes and the conclusion was there is little to none difference in power. Everyone advises using HJS cats though, but these cost way too much. On the other hand magnaflows look a bit restrictive (the center part especially), so I am not sure what to choose here. I am considering using stock secondary cats, their core looks exactly like HJS and they are 200 cell as well

[SYT_Shadow]

I could never do full catless, the smell it just too horrible. Besides the rasp and polluting a ton for just 5hp more

I have the ESS HGC Xpipe. I haven't felt a torque dip, it feels stronger everywhere than my stock M3 with stock Xpipe

[tlow98]

Originally Posted by SYT_Shadow

I could never do full catless, the smell it just too horrible. Besides the rasp and polluting a ton for just 5hp more

I have the ESS HGC Xpipe. I haven't felt a torque dip, it feels stronger everywhere than my stock M3 with stock Xpipe

Agree. The pollution is insane and for all the other things you give up - comfort, smell, droning.

Good to hear you’re considering cats again. The reality is that 200cell cats flow extremely well, especially the stock units. You’d be hard pressed to find higher quality or flowing units. There have been dynographs that show losses AND gains when cats like this are used which means the delta of these types catalytic converters is so small it’s only perceptible to extremely sensitive testing.

Can’t speak to what it will do for torque, however.

[opihi5]

Originally Posted by that_grey_m3

but I notice their is a very noticeable torque loss from low to mid range rpms.

It’s called s65

[dparm]

Originally Posted by that_grey_m3

How much increase of HP is there from deleting the 200 cell secondary cats? Right now I am fully catless, but I notice their is a very noticeable torque loss from low to mid range rpms. For instance, I was going up a hill in 5th and 6th gear at 2700 rpm and i tried to give it more gas and my engine bogged and throttle did not move only bog.

I know a tune will fix this issue, but would I be able to gain more useable torque from a set of high flow cats? That way with a tune I will have even more torque. If there is no great power loss from putting on 200 cell high flow cats I may opt for this.

Run the 200-cell high-flow cats. It will smooth out the exhaust sound, remove rasp, and make things smell better. The power loss over a catless X-pipe is not going to be that noticeable at WOT. If you really think you can feel 5hp on a car with over 400, you have an unbelievably sensitive butt-dyno.

Remember, the S65 doesn't start making lots of torque until over 3000rpm. As others have said, you need to downshift. Going up a hill @ 2700rpm in 5th/6th gear = downshift.

[inTgr8r]

Originally Posted by seevin

.......
...... On the other hand magnaflows look a bit restrictive (the center part especially), so I am not sure what to choose here. I am considering using stock secondary cats, their core looks exactly like HJS and they are 200 cell as well

The center is where there is the least amount of flow in the system.
Most flow is laminar towards the pipe walls.

[strokemycocktus]

Originally Posted by inTgr8r

The center is where there is the least amount of flow in the system.
Most flow is laminar towards the pipe walls.

Thanks, good to know. Why is everyone so excited about HJS and their design then? I've read many times that they flow better than other 200 cell units.
Magnaflows would fit my application perfectly, I am just a bit worried about their quality. Although it seems some xpipe manufacturers use them in their setups (challenge, AFE, possibly ESS).

[inTgr8r]

Originally Posted by seevin

Thanks, good to know. Why is everyone so excited about HJS and their design then? I've read many times that they flow better than other 200 cell units.
Magnaflows would fit my application perfectly, I am just a bit worried about their quality. Although it seems some xpipe manufacturers use them in their setups (challenge, AFE, possibly ESS).

Most OE CATs are designed for optimal surface area to provide for compliance of designed function while maintaining air flow above minimum required.

HJS flip that around where air flow is the primary objective while still providing compliance to a minimum standard...

Most other aftermarket CATs fall somewhere in between and their primary objective is a reasonable cost solution for OE replacement.

I haven't seen an interior spic of an HJS lately but some of the design differences you see are multi wound cores vs single wound.

The shape also has a big impact.
The flat shaped OE primaries are much more restrictive that a cylindrically shaped CAT.
Also the pipe shape (cones section) for influent and effluent flow has an impact.

There are many other none flow factors relating to the cost of HJS such as materials and the sacrificial coatings.

[SYT_Shadow]

Originally Posted by seevin

Thanks, good to know. Why is everyone so excited about HJS and their design then? I've read many times that they flow better than other 200 cell units.
Magnaflows would fit my application perfectly, I am just a bit worried about their quality. Although it seems some xpipe manufacturers use them in their setups (challenge, AFE, possibly ESS).

I once asked Jack @ CPI about what cats to put into the BW Xpipe and he said the metallic substrate Magnaflow's were perfectly good

I find to reason to challenge Jack, so I'll put those on if I ever get a BW Xpipe



https://www.custom-performance.net/p...idcategory=247

[strokemycocktus]

What about secondary OEM vs HJS? The substrate looks very similar:

Originally Posted by SYT_Shadow

I once asked Jack @ CPI about what cats to put into the BW Xpipe and he said the metallic substrate Magnaflow's were perfectly good

I find to reason to challenge Jack, so I'll put those on if I ever get a BW Xpipe

That's good news, maybe they aren't that bad after all. Guess I won't try to reinvent the wheel, go with Magnaflows and call it day.

[Dave07997S]

The OEM rear cats are 200cpi and are an excellent quality. No need to switch out to the HJS...save your money.

Dave

[strokemycocktus]

I am not even considering HJS, I would be able to buy a new x-pipe for the money spent on cats + labor.
Question is whether messing wih secondary OEM cats is worth it over the Magnaflows - I would need to find a pair of reasonably priced used ones, cut them, weld the cones, etc, which considering labor will cost more than magnaflow.

[SYT_Shadow]

Originally Posted by seevin

I am not even considering HJS, I would be able to buy a new x-pipe for the money spent on cats + labor.
Question is whether messing wih secondary OEM cats is worth it over the Magnaflows - I would need to find a pair of reasonably priced used ones, cut them, weld the cones, etc, which considering labor will cost more than magnaflow.

I won't pretend to be an expert, but based on what Jack said I'd buy the Magnaflow's and call it a day!

I may still do this to a BW Xpipe

[Todd0131]

I put the magnaflows on my BW xpipe that they fir perfect, cut down the rasp and smell. I put hem in the primary location and noticed no loss in power

[SYT_Shadow]

Originally Posted by Todd0131

I put the magnaflows on my BW xpipe that they fir perfect, cut down the rasp and smell. I put hem in the primary location and noticed no loss in power

The BW Xpipe with welded in Magnaflow cats is a pretty cost effective, high quality Xpipe

[tom @ eas]

S65s will eat up the Magnaflows in record time. It's not a very good cat, but it's cheap and people use them.

Go HJS or GESI cats if you don't want to do this a second time. 15+ years later and you'll still find used Supersprint section 2s (uses HJS) being used/sold on E46M3s.

[strokemycocktus]

What do you mean by eating the cat? What can actually happen to it, how does it break?
What are tt cats?
Thanks