L-Series Straight Through

Hello all! (bear with me on this one)

I've had a look through the forums everywhere regardless of Land Rovers (blasphemy!!), and cannot get to the bottom of it! I've put a decat pipe on my L-series freelander and soon after cut the back box off. As i soon found out it wasn't acceptable so bodged the pipe to quieten it down. But after someone told me it needed back pressure to ensure the turbo didn't spool past its threshold, i've since put a new back box on (repeat face palm).

I'm technically minded when it comes to mechanics and engine principles and noticed the difference when it was straight through to when the back box went back on with increased torque blah blah blah, but I'd like someone with personal experience to say whether or not its going to shag my turbo and send the propellor fins down into the cylinders! Apologies for the length but wanted to explain exactly the situation because i cannot (like a lot of people) afford for my engine to go bang along with the turbo.

Advice good or bad welcome….be gentle

So very temped to cut my cat off, but will fail the mot.

I was always under the impression the least pressure the better. I have no backbox but it doesn't make it much louder, in fact I often have to point it out to people

Thats my thought exactly. I believe as of feb this year tdis need cats so ive kept it for the test in October. The decat hasnt really changed the noise level but made it evvveer so slightly deeper in note. Mpg is improved and turbo lag is reduced

https://www.google.co.uk/?gws_rd=cr&ei=7WOBUrXRMsfQtAa_pIHIDA#q=can+low+back+pressure+damage+a+turbo

from passat-world
"A Turbo DOES need backpressure, after all - and some more Exhaust stuff"
A Turbo DOES need backpressure, after all - and some more Exhaust stuff
( edit: seems the post be about pipe diameter and lack-of-velocity causing added backpressure
( was another article re pipe diameter as re velocity - too large a diameter decreases exhaust velocity
( depending on bhp / exhaust flow of engine
( be tons of articles about exhaust back-pressure - flow -etc on the net

supposed to be - according to google - something in here about reduced back-pressure and turbo issues
skimmed the article - didn't see it
Buying a turbo car - Turbo Technics
( edit: found it - just sais :
( " Uprated or non-genuine exhaust system. Reducing the exhaust back pressure with a free-flow exhaust system can cause oil leakage from the turbo oil seals, leading to blue exhaust oil smoke."

In case of L-series... old diesels NOT NEED BACKPRESSURE. as rover ron described it here lseries2

Diesel do NOT NEED BACKPRESSURE unlike petrol engines. The less restriction the better.

Click to expand...

Conclusion is simple - fastest travel of exhaust gases is better,


http://www.dieselnet.com/tech/diesel_exh_pres.php

At increased back pressure levels, the engine has to compress the exhaust gases to a higher pressure which involves additional mechanical work and/or less energy extracted by the exhaust turbine which can affect intake manifold boost pressure.

Click to expand...

Excessive exhaust pressures can increase the likelihood of failure of turbocharger seals, resulting in oil leakage into the exhaust system.

Click to expand...

Less restrictions = lower pressure = safer

Winu said:

In case of L-series... old diesels NOT NEED BACKPRESSURE. as rover ron described it here lseries2



Conclusion is simple - fastest travel of exhaust gases is better,


Engine Exhaust Back Pressure



Less restrictions = lower pressure = safer

Click to expand...

This^^^^

Lower pressure in the exhaust the better. It will allow a couple of extra horses and the turbo will spool up earlier.
It won't over pressurise as the turbo has a waste gate to prevent it.

Thats what I wanted to hear thanks guys i think because of ease and security with the weight remaining on the hangers, im going to modify I.e cut into the back box and remove some of the packing along with blocking the perforations of the pipe. See how that pans out...

charleyb123 said:

Thats what I wanted to hear thanks guys i think because of ease and security with the weight remaining on the hangers, im going to modify I.e cut into the back box and remove some of the packing along with blocking the perforations of the pipe. See how that pans out...

Click to expand...

Why not see if you can order one of SES88 new low profile back boxes
Here
http://www.landyzone.co.uk/lz/f9/an...h-smaller-more-compact-back-boxes-255102.html

hmm might have to give him a shout, thanks it would be on my list of things to do soon but due to the nature of my luck, the IRD needs replacing……

I have been told that as from last year 2013 it was only new cars that needed a cat on other wise fit a through pipe and that was from LR main agent Stratstones

My personal experience of doing exactly this, is that straight through is far too loud, but buy a Disco back box (which is tiny) for £27 ish and cut off the excess pipe, weld to your existing exhaust, fashion a hanger and weld that on and Bob's your uncle

Hi
I have been running my L series with a straight through system for around 100,000 miles. What I found was a sudden loss of power as I accelerated. Eventually I traced this to the turbo sucking the inlet pipe flat! I renewed the air filter and now do so frequently and have had no further problems (with the exhaust anyway!) it's never a problem at MOT time and is only a bit noisier but deeper sounding than standard. It has a Longlife stainless straight thru system from the down pipe flange. Hope that helps.
Happyhippo

teddywood1 said:

I have been told that as from last year 2013 it was only new cars that needed a cat on other wise fit a through pipe and that was from LR main agent Stratstones

Click to expand...

Removing the CAT from a diesel is not a MOT failure, never has been. Removing a DPF when one was fitted as standard is if a fail the tester is sharp enough to know.

Removing the CAT is only an MOT failure if the car would be subject to a CAT function test as part of the MOT - i.e. post '92 petrol engine cars.

Tannaton said:

Removing the CAT from a diesel is not a MOT failure, never has been. Removing a DPF when one was fitted as standard is if a fail the tester is sharp enough to know.



Removing the CAT is only an MOT failure if the car would be subject to a CAT function test as part of the MOT - i.e. post '92 petrol engine cars.

Click to expand...

Did I read this wrong then?

Kizzeh said:

Did I read this wrong then?

Click to expand...

WOW - no you didn't.

There was a lot of debate about this amendment at the time and the announcements for it talked only of DPF's. Clearly it's been amended to cover catalysts too.

My apologies - I stand corrected...

Yeah but you can knock the guts out of a cat and refit or even if you wanted to weld the casing around a decat pipe.

it only came in last year and I was not aware until talking to the man that knows everything there is to know about landrovers and I still think it is only for cars registered from last year onwards because he said my car a 2006 hse td4 auto could have a de cat pipe on.

teddywood1 said:

it only came in last year and I was not aware until talking to the man that knows everything there is to know about landrovers and I still think it is only for cars registered from last year onwards because he said my car a 2006 hse td4 auto could have a de cat pipe on.

Click to expand...

Sadly I don't think that is the case - I thought it was but I'm eating humble pie. If you refer to section 7.1 of the MOT testers manual (amended Feb 2014) which you can find here :

MOT Documentation Contents Page

All compression ignition vehicles will now be failed for missing catalytic converters and particulate filters where one was fitted as standard. There is no stipulation as to the year of the vehicle.

As ZDomZ pointed out the tester has now way of knowing if the guts have been removed from either, and there seems to be no method advised in the testers manual of ascertaining if one was fitted by the manufacturer in the first place (which makes the testers job unreasonably difficult in my view).

I remember discussing this and reading about it earlier in the year and at that point the focus was DPF's - Cats were not mentioned. Clearly some officials have decided that they should - even though it has no bearing on whether the vehicle is roadworthy. The catalysts fitted to diesel engines work differently to those on petrol engines and don't reduce as many pollutants.

What's the betting that next they will be targeting EGR removal?

Yeah well egr removal will just become egr blanking plug insertion!