Running a Td4 with a straight-through CAT?

I have a question concerning my Freelander 1, Td4, 2004, exhaust system.
What are the chances my Freelander would run better with a straight-through catalytic converter, before the large back-box?
And please ignore the MOT test for this question as I know a CAT is required – I think.
It’s performance I’m after, and I’m led to believe a straight through exhaust would be beneficial.
If a straight-through cat was fitted (no baffles or whatever), what might, if any, be the affect?

ITs a simple breathing mod, easier flow = more BHP, so yes it will make more performance, and being perfectly honest with you, I don't think it makes that much difference to the emmissions, although I'd check with an MOT station, see if they could do just an emmisions check for you after you decat it. Even with everything removed form the exhaust, these things are still pretty quite, sure, they aren't mercedes e-class quiet, but a "straight through'd" TD4 freelander is no noiser than a 1.8 k-series freelander.

Thanks Jayridium. That's what I was hoping for. My plan is to get a box and rip its guts out, so it looks the part while giving me better performance & mpg.
I'm aware 2 strokes need a back pressure but not 4 strokes.

No turbo needs back pressure, Naturally Aspirated engines fo need some back pressure for pulse tuning, but thats a whole lot of black magic in and of itself.

Your answer is wizard. Thanks.

a.f.a.i.k the test done to a c.a.t. would be to measure it's temp ..
is the emissions test for a diesel not just about smoke particles emmited ?
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anyhow .. i kept the c.a.t. intact and fitted a straight thru backbox ( stainless.s )
works fine .. as in .. a tad better response from lower rpm .. sounds good as well

It’s performance I’m after ..

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well do take a look at :
https://www.landyzone.co.uk/land-rover/intercooler-problem-mod.126484/
( pics on page1 are a bit blurred for some reason ..
( be clearer pics on page 2
i.e. the quicker the air flows across the maf. sensor ..
the quicker the engine will respond to go-pedal input
particularly from the lower rpm range
( the main drive-abilty issue with the td4/m47r in stock format .. i.m.h.o. )
adding some heat insulation to the air intake .. negates the engine bay heat soak effect ..
i.e. 'cause the heat be registered with the air temp sensor .. and reduces fuel input ..
resulting in potential sluggish response until cooling air enters and drives away built up heat
.. the egr delete-mod would be part of that a.i. modification ..

then .. with the added torque at the lower rpm ..
consider adding slightly larger tyres to raise the gearing a bit
( unless you go off-road .. might be detrimental in that case )

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The blurred pics seem to be something Photobucket is doing, just to let you know.
Would a downstream O2 sensor after the cat not throw codes or make the ECU a little bit unhappy if the cat was modded to straight through? Just something to keep in mind.

I have to say you've all given me good info and something to consider. I do like the ss backbox idea. Where did you buy that?

I do like the ss backbox idea. Where did you buy that?

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i'm not sure where i got mine be making them anymore .. however ..
take a look at .. https://www.muddymods.com ..
( the owner is a member here .. )
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here's the 'exhaust'page ..
https://www.muddymods.com/collections/freelander-1/Exhaust
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The blurred pics seem to be something Photobucket is doing, just to let you know.

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cheers .. thought that might be the case ..
but have never used photobucket m'self ..
p.s. the diesel td4 fl1 doesn't have an o2 sensor
( i think that's just for petrol engines .. no ?
( i could be mistaken
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btw: removing that foam surround from off the airfilter helps as well
unless you go off road were as some twigs or similar might be drawn in ..
( be a case of every little bit helps .. even in a small way
( all adds up ..
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using a fuel additive can help as well to smooth out the combustion process
'n keep the system clean ..
i've been using 'diesel rhino' since day 1
( because i've used it before with hgv vehicles over a few years )
so far .. nearly 190k miles .. original injectors and glow plugs
both operating fine ..
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That's what I want! I'm getting one.

paul99 said:

Would a downstream O2 sensor after the cat not throw codes or make the ECU a little bit unhappy if the cat was modded to straight through?

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No downstream O2 on the TD4, nothing to worry about there.

Hard Drive said:

That's what I want! I'm getting one.

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I made my own straight through back box, which did improve low speed pick up, but no noticeable improvement at the top end. I've kept my cat though, but removing it's guts would likely improve pickup more.

Nodge68 said:

No downstream O2 on the TD4, nothing to worry about there.

I made my own straight through back box, which did improve low speed pick up, but no noticeable improvement at the top end. I've kept my cat though, but removing it's guts would likely improve pickup more.

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Hi Nodge. I'm considering grinding-off the final pipe from the Back-box, with a view to ripping out the internals to make it a straight-through, before welding the pipe back on - as a project and recording its progress. This might be of some use to others, I guess.
I'm in the process of ordering a s/s Back-box, but might hold-off until the virus thing ends.
What might be your opinion concerning my cannibalisation of the box, as explained?

what i were thinking of doing ..
were to get rid of back box all together ..
and have the exhaust come out by .. in front of .. the nearside rear wheel
.. with a down turned exit bit facing the road surface .. ( thinking of pedestrians )
so can open tailgate window fully .. without having exhaust fumes sucked in ..
( don't know if that's legal .. or not )
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Hard Drive said:

I'm considering grinding-off the final pipe from the Back-box, with a view to ripping out the internals to make it a straight-through,

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You're better off removing the box completely, as the internals of the box aren't easy to modify for better flow. This is why I went for a DIY solution.

You're better off removing the box completely, as the internals of the box aren't easy to modify for better flow. This is why I went for a DIY solution.
Nodge, that is a good bit of engineering! I've taken on-board all that's been written and will replace my baffled back-box with a straight-through s/s ready-built unit.
I've just watched a YouTube video showing what a Back-box consists of and reckon a cut-out panel on top would allow me access to remove the innards quite easily, welding an overlapping plate to cover the hole.
I like a challenge. I also like what you did. You might consider manufacturing and selling it on the QT to LZ FL1 members? It looks pretty good to me.
EDIT... Ah, I've just had another look and can see how you did this. Hmm, I might have a go myself. Nice one.

Hard Drive said:

You might consider manufacturing and selling it on the QT to LZ FL1 members? It looks pretty good to me.

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I wanted a budget option (mine cost under £80 all in), but Warren of Muddymods sells ready made, custom fit straight through boxes for all models of FL1.

Yeah, I've seen them and am impressed. I would buy one of these, except I'm impressed enough with seeing what you did to try it myself.
Your budget option has given me the nudge (by Nodge) to try it.
I'm now looking at available parts.
Thanks again.
Another edit. I think I've just seen your YouTube video.
Nodge Mod back box.
Very impressed.

Hard Drive said:

I'm now looking at available parts

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Ebay was my friend here.
I went with a 63mm ID stub box 500mm long IIRC. I went for stainless steel, for long life. I cut the pipe off the standard box, right at the box, and used that cut section to insert into the new SS box. I did need to use a shim of stainless to reduce the box diameter down, and use expanding assembly past to make the joint permanent. If I was doing it again, I'd go with 60mm ID exhaust stubs, as no shimming would be needed. The downturn is just a mandrel bent 90° SS pipe, of the correct OD to suit the box, which was cut to fit the space. I made up hangers using modified exhaust clamps. I also used Jetex band clamps, for maximum clamping capacity.

Nodge, you're a mind-reader. I came back to LZone to ask you for details and you beat me to it. I've copied what you have written in order to copy. I hope you don't mind.

Thanks.

Nodge68 said:

Ebay was my friend here.
I went with a 63mm ID stub box 500mm long IIRC. I went for stainless steel, for long life. I cut the pipe off the standard box, right at the box, and used that cut section to insert into the new SS box. I did need to use a shim of stainless to reduce the box diameter down, and use expanding assembly past to make the joint permanent. If I was doing it again, I'd go with 60mm ID exhaust stubs, as no shimming would be needed. The downturn is just a mandrel bent 90° SS pipe, of the correct OD to suit the box, which was cut to fit the space. I made up hangers using modified exhaust clamps. I also used Jetex band clamps, for maximum clamping capacity.

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I've been trying to find a similar Stub Box, as per your measurements, but alas cannot locate similar. Might you be able to point me in the right direction?