Unblocking a HDi exhaust NOW WITH Video!

Post by **citroenxm** » 21 Jun 2011, 23:21

yup, its the x plate in my signiture!

Paul

Deanxm · Post by **Deanxm** » 21 Jun 2011, 23:33

Ive never had the time to read that far down

D

miked · Post by **miked** » 21 Jun 2011, 23:40

** warning, off topic **

I unblocked the cat on the vtr because it had started falling apart inside. The car went alright but it sounded like a bag of nails, it was like loose baffles in a back box if you know what I mean.

So, different symptoms to your problem, but easily fixed with a bit of smashing.

It did actually pass the next MOT. After initialy failing the tester took it for a raz down the bypass, then quickly tesed it and somehow it passed.

About a week later a big white van ran in to the back of it while I was waiting to turn

I've been diesel powered ever since then.

KevMayer · Post by **KevMayer** » 22 Jun 2011, 17:05

There's a lot of smoke in your video and it's black.

Could it be a fueling problem?

If the cat is restricting flow you'd think that the airflow meter would still measure the air entering the engine and tell the ECU how much fuel is needed. So, does it make sence that you've got so much black smoke?

It looks more like a boost leak to me, or a faulty MAF maybe.

Somehow, you're getting too much fuel injected for the air input to the engine.

What would a faulty Lamda probe look like in terms of fuel control?

Does a failed turbo cause black smoke?

A boost leak produces lots of black smoke.

Deanxm · Post by **Deanxm** » 22 Jun 2011, 18:33

KevMayer wrote:There's a lot of smoke in your video and it's black.

Could it be a fueling problem?

If the cat is restricting flow you'd think that the airflow meter would still measure the air entering the engine and tell the ECU how much fuel is needed. So, does it make sence that you've got so much black smoke?

It looks more like a boost leak to me, or a faulty MAF maybe.

Somehow, you're getting too much fuel injected for the air input to the engine.

What would a faulty Lamda probe look like in terms of fuel control?

Does a failed turbo cause black smoke?

A boost leak produces lots of black smoke.

the blocked exhaust will cause the smoke as it restricts air flow, and i dont think dervs use the maf for fueling, i think thats for the egr.
well im fairly sure anyway that a derv uses throttle position to govern fueling and looks at boost pressure to adjust fueling levels, if the exhaust is blocked it may well see boost and throttle input but not enough air will flow to burn it, hence the black smoke and no power.

Im no derv expert though...................

D

Post by **citroenxm** » 22 Jun 2011, 21:09

Hi.

She is DEFENALTY NOT over fuel ing... this IS I promise a blocked exhaust.. becuase when the engine is run with the exhaust disconected, theres NO black smoke, the engine Revs to 5k...

If you listen to the vid the engine is struggleing to 2500k.... so its an air restriction problem due to blocked exhaust... I was after ideas for unblocking it..

Cheers
Paul

DickieG · Post by **DickieG** » 22 Jun 2011, 22:04

Get a de-cat pipe, if necessary get it made up there are loads of companies making de-cat pipes on a one of basis, my previous HDi had one and I'm thinking of getting one for my present one.

Post by **citroenxm** » 22 Jun 2011, 22:07

My current HDi exclusive Richard is de-catted... so that I shall be dooing!

Paul

DickieG · Post by **DickieG** » 22 Jun 2011, 22:23

citroenxm wrote:My current HDi exclusive Richard is de-catted... so that I shall be dooing!

Good move.

HDI Dave · Post by **HDI Dave** » 22 Jun 2011, 22:54

Deanxm wrote:Just being choked to death by the cat blockage, unless the silencers are rotten out and are filled with insulation thats dropped in and blocked the exhaust.
Amazes me how it managed to get so bad, no wonder the turbo was dead, must of cooked it alive.
D

That's exactly what I was thinking..the cat..but didn't mention it because it's an exact symptom of a cat blockage on a petrol car..I know.. I had it!

Surely an exhaust cat is an exhaust cat..petrol or diesel?

dunno meself,just going on my failed cat,(mundano petrol), but any petrol engine forum will tell you that when the cat's nakered - it won't accelerate,(mine wouldn't), and a simple test is to get underneath,shake the cat part, and it will (90% of the time) rattle like a golf ball in a tin can..
..as the porcelain? bit in the middle breaks loose, then it blocks the pipe on applying throttle/forcing gasses through,it sends the loose bally bit inside the cat rearwards, to ultimately block the pipe

oh and yes, a nakered cat pongs also,like rotten eggs, for some strange reason! but that's just my petrol engined cat experience..

Deanxm · Post by **Deanxm** » 22 Jun 2011, 22:59

The other thing is if the cat is poisoned it can overheat and melt which blocks all the little airways, no rattle just jammed up solid but the falling apart thing is rather common so i hear.

Can someone explain how the heck you get a cat to work on a derv in the first place though? i mean does a derv really run hot enough to light the cat up in the first place and when its not surely the particulates are just going to poison the thing so it wont work anyway...................

And another thing, why do fap equiped cars seem to smoke like hell when they are booted, i thought fap was all about reducing particulates?

D

Post by **RichardW** » 23 Jun 2011, 07:56

A diesel cat is not as complex as a petrol one - it's just for reduction of NOx to nitrogen and oxygen. There's no lambda sensors or anything complicated required

unless you've got a FAP

Chris570 · Post by **Chris570** » 23 Jun 2011, 08:12

DickieG wrote:
citroenxm wrote:My current HDi exclusive Richard is de-catted... so that I shall be dooing!
Good move.

i presume the difference is in performance and economy? is it a marked difference?

cheers

Post by **citroenxm** » 23 Jun 2011, 08:14

Helps the flow of air, flow of air - flow of gasses - more air flow more performance or quicker performance..

Paul

Chris570 · Post by **Chris570** » 23 Jun 2011, 08:14

love the quick reply

where would one obtain such a part