Straight thru exhaust & DOE?

Bearcat

looking at a TD5 defender and you can hear the whistle of the turbo at idle. Obviously owner removed Cat, i just had a fleeting look at machine. I know cat is removed as I did the same on a previous passenger version of a TD5 and it was too young for nct's etc.........will jeep have hassle in DOE? It's a 99 TD5.;)

101sean

No you won't have any hassle. Mine has no cat or middle box (yours will never have had a cat) and goes through NCT no problem. I know of another Td5 with no silencers at all.

scudster

Sean, you are quite correct here. Its not really the same as an emmissions test for a petrol car. My diesel car has the cat removed and I've never had a problem putting it through the NCT.

101sean

Yes, they are tested on smoke opacity (or something like that) so dumping the cat and egr makes no difference. Suspect it will get more difficult to do on the latest vehicles with everything monitored by ECUs :rolleyes:

I think the OP is more concerned about noise, I know the NCT is looking more closely at this but it's mostly sporty cars they are aiming at (to curtail the scourge of "boy racers" if you believe sensationalist articles in local rags and vote seeking local councillors )

I don't know whether DOE testers look at noise levels to the same extent, maybe Slidey could comment if he's lurking

Slidey

LGV testers manual wrote:

Assess the effectiveness of the silencer in reducing, as far as is reasonable, the noise caused by the exhaust
from the engine

You may be failed if it was very loud, never failed one for that yet. I suppose it may depend on the tester on the day I would be of the opinion you should be ok.

There will be no effect on the emissions part of the test, as Sean said, it is based on the clarity of the smoke. Any turbo vehicle reg prior to July 08 has a fairly high tolerance and it if is any way right will pass..


Testers manual here, changes due in the very near future though.

101sean

Thanks for that Slidey.

The turbo does most of the silencing, with no middle box mine isn't loud, just a pleasant bit of turbo whistle, no boxes is even better

Downside is noise internally, gets a bit boomy under hard acceleration around 50-60 but you get used to it.

One of the common American military vehicles you find at shows here and the UK is the M35 Reo 5 ton truck which has the exhaust stack coming straight off the turbo with no silencer, they are nicknamed Whistling Billys for obvious reasons

Slidey

Go to Youtube and do a search for Scania V8 sidepipes.

They are all the rage with the magpie truckers. They are noisy on tickover but on a big pull they must bust yer head. Most have them on a toggle switch and can put the exhaust through the silencer though

101sean

Just watched a couple with the volume cranked up

I'll admit to having a recording of the V8 exhaust on my 101 as the message tone on my phone

Slidey

101sean wrote: »

I'll admit to having a recording of the V8 exhaust on my 101 as the message tone on my phone

Better than the tractor trying to start on me old mans phone!

_Conrad_

I've had an old 2.8 trooper pass the doe with a straight pipe, and two diesel cars that passed the nct, a straight diesel one with middle box out, and a turbdiesel one with no silencers at all, just 100% straight through pipe. It does depend who you'd get though i suppose, but the NCT guys in particular are looking out for loud petrol exhausts.

The long suffering family landcruiser sounds like it has a straight pipe even though it's got a full exhaust system. Middle box was replaced with a non toyota part (but supposedly standard spec) and there's now a serious grunt and whilstle of fit. No bad thing though IMO as the sound of the old 1KZTE 3 litre is lovely

gofaster_s13

Slidey wrote: »

You may be failed if it was very loud, never failed one for that yet. I suppose it may depend on the tester on the day I would be of the opinion you should be ok.

There will be no effect on the emissions part of the test, as Sean said, it is based on the clarity of the smoke. Any turbo vehicle reg prior to July 08 has a fairly high tolerance and it if is any way right will pass..


Testers manual here, changes due in the very near future though.

The new manual is coming out in the early new year and exhaust noise is supposed to a fail item and is to be tested to the same criteria as the NCT.

101sean

..which from what I've read elsewhere is down to the discretion of the tester. The dB meter is only wielded if the tester thinks a vehicle is too loud, not for every vehicle.

Even so, I reckon most turbo diesels in 4x4s would still pass.

landydef

ive no cat or centre box on my td5 90 and ive never had a problem doing the doe test with it and the noise is class!
although if you find the whistle is a bit excessive it might be worth checking around the exhaust manifold for soot marks, mine has warped more than once shearing the bolts with it and its a pain in the arse to drill out!

101sean

mine has warped more than once

Do you do a lot of hard towing or got a radical re-map? Usual way of warping a manifold, cure is to grind out or slit the webs between the branches.

OldGuysRule

101sean or landydef, I have a 01td5 disco, is there much real benefit of removing the cat? Have read of it on other forums and have seen the straight through / bypass pipes advertised

101sean

There's a small benefit but if you combine it with EGR removal and an ITG filter it makes a bigger difference as the turbo spools up quicker.

The cat is in the front downpipe, the middle box is an ordinary silencer so if you want to have a straight through system you have to replace both.

Replacing a cat is expensive if it goes, a downpipe with a plain flexi joint is less than 1/3 the price. The cat is not required for DOE/NCT test.

OldGuysRule

Cheers, I blanked the EGR some time ago. Would probably keep the silencer though

101sean

Did you just blank it at the manifold or remove the entire EGR valve? If the valve is in place it's still obstructing the airflow.

OldGuysRule

Only blanked it (well got someone to do it), I must look into getting the kit removed fully

Mycroft H

OldGuysRule wrote: »

101sean or landydef, I have a 01td5 disco, is there much real benefit of removing the cat? Have read of it on other forums and have seen the straight through / bypass pipes advertised

Get an egr bypass valve if you do. There relatively inexpensive