[Closed] Do Redex type diesel treatments work - smoky diesel

No, it's snake oil.

Most likely you have leaky injectors or seals, nothing will fix that.

They do to a point, but chances are that's not your problem.

Smoke under hard acceleration on a regular basis is most likely because there's too much fuel and not enough air. There are a variety of things that could cause this. In theory, coked up injectors could stop the fuel from atomising correctly, which would mean it doesn't burn very well hence smoke, but I don't think that's much of a problem with a modern ( > 2000) car that's been driven normally.

or you just have a dpf\cat thats getting full of soot and gets cleaned out with a foot full of throttle. perfectly normal in an older car. Redex won't make a jot of difference, just give it an italian tune up before the mot

Yep as above, depends on what the problem is. I think for your situation some more investigation is needed.

Used in the correct situation, yes they do work and some are better than others I've had good results with Wynn's products before.

Stick to the recommended dose. Don't try and make it more concentrated than it should be thinking it'll get to work quicker.

Little and often is better, hence why usually it's recommended to just use premium fuel rather than additives. Its essential the same thing but the fuel company have mixed it together for you.

just give it an italian tune up before the mot

In case you don't know what that is. Bring the vehicle slowly up to temperature by driving normally for a bit. Then once up to temperature give it some beans for a bit.

I like to use a mix of motorway and windy A roads. On the motorway do 60-70 but in one gear down from the highest to keep the revs higher up the rev range, somewhere in the middle not bouncing off the limiter. Same sort of thing (one -two gears down form normal) on the windy A road but as you have corners to navigate you slow down and speed up and use more of the rev range (on motorway you are keeping a constant speed).

or you just have a dpf\cat thats getting full of soot and gets cleaned out with a foot full of throttle.

That's not how they work (as I understand it, anyway). They don't fill up like a hoover bag and then flooring it empties the bag. They get cleaned out by heating themselves up to burn the soot off. That happens in one of three ways: The exhaust gas simply gets hot enough on its own, if you drive fast for a sustained period; the engine tweaks the settings to make the exhaust gas hotter for a time anyway; or it injects extra fuel into the exhaust which reacts with a catalyst in the DPF and makes it extra-hot. The key points are that all these things take some time to happen, and they cause the soot to burn off into CO2 (and a tiny bit of ash) so you won't see it coming out of the exhaust. For that matter, if the OP is seeing any smoke at all he hasn't got a DPF.

If you have problems that cause excessive smoking and you do have a DPF, you won't see the smoke, but it'll fill up your DPF quickly and you'll get an error light. A bad garage will say 'oh your DPF is blocked' and either clean or replace it, when technically it's working and something else has failed. IF you don't fix whatever it is upstream that's causing the smoke, it'll keep smoking and fill up the DPF again.

just give it an italian tune up before the mot

This can clear out coke caused by driving it slowly on really short trips all the time, but if that's not your problem it won't help at all.

Work out what the issue is first.

I have had a 'proper' turbo clean at our garage for a sticking acuator/vanes. This though involves actual hands on cleaning of parts and running cleaning agents through things. It worked well - we went from a somewhat hesitant turbo to full force. This when we first bough the Volvo and I think previous owner had done a few too many gentle trips.

A neighbour also had a 'Terraclean' of DPF done from same garage - DPF off, sent to proper company who basically jetwash the crap out of it, clean up the water before it is dumped in the drains, and send back shiny DPF good for another many thousands of miles.

I have used 'posh' diesel on our old Touran and Galaxy - a couple of tanks prior to MOT as they both started getting a bit claggy old diesel at 160k+ miles. The Volvo was fine and still showed low emissions.

Some cars (such as mine) tell you not to use the posh diesel as it interferes with its own DPF management. I know, I was surprised too, but it's in the handbook.

For that matter, if the OP is seeing any smoke at all he hasn’t got a DPF.

Disagree, my C8 is smoky, mostly because of injector seal leaks, possibly a turbo leak as well.

This can clear out coke caused by driving it slowly on really short trips all the time, but if that’s not your problem it won’t help at all.

From experience it doesn't, if the vanes are crudded up then the only option is manual cleaning with oven cleaner or similar.

Almost exclusively use supermarket diesel and never failed emissions.

or you just have a dpf\cat thats getting full of soot and gets cleaned out with a foot full of throttle. perfectly normal in an older car. Redex won’t make a jot of difference, just give it an italian tune up before the mot

The whole 'Italian tune up' thing is the equivalently of fixing your telly by giving it an authoritative slap. Its not the 1970s.

In many cases a car will abort the DPF regen at high revs or heavy load. If you suspect the DPF is clogged then driving at high revs probably leave it its more clogged. Seeing smoke isnt what a regen looks like.  For the DPF to do its job just drive normally. They are designed to work when the car is being driven normally.

if the vanes are crudded up

Yes, that is a bugger for short trip gently driven cars, but I'd expect the car to go into limp mode if it cannot generate the required amount of boost. Unless it's a really old car. I had a 1992 VW TD (not even TDI) that was all mechanical - that would never have known if the turbo vanes were sticking. If it had turbo vanes, which it didn't, it only had a wastegate.

If you suspect the DPF is clogged then driving at high revs probably leave it its more clogged

I'm the go to guy at work for being able mysteriously unclog our hateful Astra pool car. I redline it constantly in 2nd or 3rd on a motorway jaunt. The limiting factor is the engine screaming over the radio. It either clears it or it'll do everyone a favour and blow up.

For the DPF to do its job just drive normally. They are designed to work when the car is being driven normally.

I can confirm this, I monitor my DPF with an app, during a regen, the DPF full % drops at the quickest rate when I’m at the lights, heavy throttle it hardly drops at all.

I had a petrol Hyundai Trajet a few years ago, failed the MOT on emissions, a bottle of Redex and an Italian tune up and it passed the retest.
Could have been the stuff, could have been the high temps but I think the stuff probably worked as most of my driving is infrequent long trips rather than lots of short ones.
I've given subsequent vehicles a bottle of it once or twice a year since

The whole ‘Italian tune up’ thing is the equivalently of fixing your telly by giving it an authoritative slap. Its not the 1970s.

I'm sorry but no.

That's probably the worst analogy I've ever heard.

Yes, that is a bugger for short trip gently driven cars, but I’d expect the car to go into limp mode if it cannot generate the required amount of boost.

Oh yeah, it will do that but just driving it hard will do nothing to help unless you catch it early on.

Diesel engines can get coke deposits built up on various internal bits for a few reasons. If for example there's a problem with fuelling then it might get smokey, and that can get sooty oily crud on the bits after the combustion like the exhaust valves or the turbo vanes. The oily nature of the fuel can end up depositing a sort of varnish on the injectors and their nozzles. And exhaust gas recirculation is a common problem, where it pipes some exhuast gas back into the intake to reduce the amount of oxygen and lower the combustion temperature to reduce emissions. Of course, these things can all be interlinked - if your injectors aren't spraying nicely due to the varnish deposits you might get big droplets which don't burn all the way and become soot particles, these end up in the exhaust which gets piped back into the intake and they get deposited in the EGR pipe or the valve that controls it etc. Poor quality fuel can make more smoke which makes more coke deposits which make it smokier and so on.

An italian tune-up, in theory, gets everything hot enough to burn all the crud off. But it takes more than just flooring it onto a motorway a few times, because the exhaust gas and combustion temperatures are only high for a short time. You can make it hot by driving in a low gear at high revs for a while. But ideally you want to be towing a caravan up a big mountain or be on the Autobahn.

Driving for a long time allows everything to get hot ish but the time you spent at the high ish temperatures might be enough to clear everything out. When I got the Passat I did a run down the motorway to Farnborough every week. My first trip recorded 48mpg, after a few months it was 55mpg. So clearly something was being improved, and I never did anything other than set the cruise to 70mpg and keep it going for 2hrs.

But ultimately, if it's clogging, it's clogging for a reason, and whilst you might be able to clear it out it's going to clog again unless you fix whatever the root cause is.

I’m sorry but no.

That’s probably the worst analogy I’ve ever heard.

It's reasonably true though. Most folk doing it have no ****ing clue what it is they are actually doing by doing it or if it's what's actually needed.

But they once saw Geoff down the road doing it.

In much the same way as folk try to repair pulsing brakes by braking hard a few times.....

I confess I'm a bit puzzled by all this "get it hot" advice. Once the engine's fully warmed up will it actually get significantly hotter if you cane it? My car will get up to 87c and stay within a few degrees of that. The only time I've seen it get hotter was when I was in slow moving traffic and the radiator fan was broken, I think it was up over 100c that time but not much more. If you've a healthy cooling system the airflow at 60-70 mph will be quite enough to keep it at its normal operating temperature even if you do drop it a gear or 2.

After treatment additives can work if used sensibly, problem is most people just dump them in and cause more issues. About 95% of a bottle of redex will be a carrier solvent, probably quite a bit heavier than the diesel itself, chuck too much in and it will have the opposite effect of cleaning. If you've been using a decent fuel already then don't bother, move onto non fuel related issues..

Most things have already been said, possibly lack of fuel pressure due to seals, gasket, crack in engine. Could be fuel pump, filter inlet manifold gunking. EGR valve is a good one, could simply be sticking, it's amazing how clogged they can get on run arounds

Ref Italian tune, no.. Regens will happen within a relatively defined set of parameters, heat is one, but engine load is the other. Meet the right conditions and it will always regen (it uses fuel to do this), unless a major issue or sensor failure (monitors pressure) .. Stop it half way through and that fuel ends up in the sump, it eventually gases off again assuming a longish drive, but lots of cold runs and you'll find premature engine wear through oil dilution ..

Edit to add... Lubricant blow by could happen (as opposed to the other way), if the ring packs are damaged, you can end up burning your crankcase lube. No real easy way of checking that without removal though..

Check the car forums (of your car) for similar occurances.

@johnners

I confess I’m a bit puzzled by all this “get it hot” advice. Once the engine’s fully warmed up will it actually get significantly hotter if you cane it? My car will get up to 87c and stay within a few degrees of that.

That's just the coolant, that can sit anywhere between about 60 and 125 without causing any damage to the engine. Most temperature gauges in cars have a massive amount of filtering on them as well, as in city driving the temperature will vary quite a lot. Customers get twitchy when their temperature gauge jumps from 75 to 100 then back down again!
Exhaust gases can be anywhere from 300ish up to 800ish depending on load, engine speed and exactly what type of engine it is.

What mert said. Exhaust gas temperatures vary a lot and go up and down almost instantly with load. The DPF is right next to the engine so when you are accelerating hard it's basically being blasted with blue flames.

I confess I’m a bit puzzled by all this “get it hot” advice. Once the engine’s fully warmed up will it actually get significantly hotter if you cane it?

In normal usage, exhaust gas temps before and after your SCR will vary from 200c to 400c under load. On a regen, it can go up to over 600c

TBH those videos you see on YouTube of high performance engines with red and white hot exhaust manifolds and turbo housings aren't actually a huge distance away from what you'll have in a modern turbo charged engine when towing up a long incline.

That’s just the coolant, that can sit anywhere between about 60 and 125 without causing any damage to the engine. Most temperature gauges in cars have a massive amount of filtering on them as well, as in city driving the temperature will vary quite a lot

My car doesn't have a temperature gauge, it sits within a couple of degrees of 87c as reported via the OBD which suggests to me that the engine temperature is remaining stable. I can see that the exhaust temperature will vary with gas flow but combustion temperature in the cylinder will be pretty constant and the cooling system seems well able to keep the temperature stable across the rev range.

No one’s asked what car yet? It might not even have a DPF and might just be an older slightly smoky diesel 🙂

My last L200, bought new in 2005 did right from the off and never got worse. My new one, a 2017 does nuffin even when you boot it at night with someone elses light following you. Mind you the recirc gubbins needs cleaning out every service and seems to stick a couple hundred on the service cost

My car doesn’t have a temperature gauge, it sits within a couple of degrees of 87c as reported via the OBD which suggests to me that the engine temperature is remaining stable.

The coolant is. But the other bits of the engine vary. The cat and the DPF will be hotter, the temperature in the cylinder varies and the oil temperature will also be different depending on what's going on. It's not 87C inside the cylinder, is it? When it's full of burning fuel.

My car doesn’t have a temperature gauge, it sits within a couple of degrees of 87c as reported via the OBD which suggests to me that the engine temperature is remaining stable.

Or at least that you do a very similar sort of drive cycle with very similar loads whenever you check the temperature. Also depends which signal you are reading, there are several, some are useful for engine diagnostics and calibration etc, some aren't.
In cars with temp gauges they filter and (effectively) lie to customers, so anything from about 75 to 105 will show as "normal", i.e. somewhere in the high 80's. This data is often taken from somewhere in the radiator loop.
With CANalyzer i can get the raw data from several temperature sensors and see the variation in real time.

I can see that the exhaust temperature will vary with gas flow but combustion temperature in the cylinder will be pretty constant and the cooling system seems well able to keep the temperature stable across the rev range.

The temperature at the flame front is fairly constant, will vary slightly due to air/fuel mix, fuel type/quality and boost pressure. Actual bulk combustion chamber temp varies a lot more, all the things that impact flame front temp plus engine speed, load and a lot more.

This was just before a regen finished

@colp can you plot a graph of temps during normal driving? Correlate with road speed and throttle position? 🙂

It’s not 87C inside the cylinder, is it? When it’s full of burning fuel

I know that coolant temperature is only a proxy for the overall engine temperature. I'm sure you can manage to be less patronising, give it a try maybe?

Or at least that you do a very similar sort of drive cycle with very similar loads whenever you check the temperature

Well, I guess that much is generally true, I'm a pretty sedate driver and I've not consciously tried to get it hot, though I've usually got my phone in a cradle with a temp display on any significant journey so it's not just an occasional sample -I'm not a fan of having no temperature gauge, even if it would only lie to me! All the same, even a long drag up Porlock Hill didn't see it above 90 and that's a decent workout for a 2 litre diesel.

I know that coolant temperature is only a proxy for the overall engine temperature. I’m sure you can manage to be less patronising, give it a try maybe?

Sorry. I was trying to illustrate that the average temperature of the engine block doesn't really give you the whole story or really anything relevant to the original question, in my view.

even a long drag up Porlock Hill didn’t see it above 90 and that’s a decent workout for a 2 litre diesel.

TBH, it isn't really. The cooling system will eat that alive. It's sized for driving up an Alp in 40 degree heat with 5 up and 5 suitcases, or a trailer/caravan (or both).
Porlock is about a mile long, done and dusted in around 2-3 minutes.

And again, depending where the coolant temperature is measured it can either be a terrible proxy, or just a not very good one.

@colp can you plot a graph of temps during normal driving? Correlate with road speed and throttle position

I reckon so, I’ll have a look later

The cooling system will eat that alive.

Right but we are interested in the exhaust gas temps at the DPF and turbo.

Right but we are interested in the exhaust gas temps at the DPF and turbo.

Yes, i know, just pointing out that in anything remotely modern with a modicum of grunt the fact that the bulk coolant is only up a couple of degrees doesn't say anything about how hot anything else is.

I mean, the accepted "italian tune up" process probably wouldn't show up on bulk coolant temp either, except, ironically enough, on the sort of car that would actually benefit from an ITU.

Here’s a short run home with a stop off at the shops then onto the motorway. I put my foot down a bit to create a bit more variation on the graphs.

Cool, so it's hovering around 150C in town, takes a while to get warm (which surprises me given where it's measuring) and about 300 on the motorway. And it falls quickly after you stop booting it.

Exactly. It can hit 500 if I floor it for a while. Noticed last time I was on an autobahn

If anyone is interested the app is Car Scanner, the adapter I’m using is a UniCarScan UCSI-2000/2100 Bluetooth

You need a good quality adapter (cheap EBay ones are no good)

Having skimmed the thread no-one has suggested checking the state of the air filter.

Air filter is upstream of the MAF so that should compensate for poor airflow by decreasing fuel. A bad MAF can cause slight smoking though.

We don't know what teh OP's diesel is, how old it is or the type of injection fitted, so we have no idea if there's any air flow/pressure sensor to compensate for altitude or a dirty air filter.

Stop talking sense.

Next thing you'll be looking for fuel trims...

It's an old sprinter if I remember rightly so the second poster probably nailed the ops issue on leaky injectors especially if worse when cold.

FWIW, I had a live feed pre-turbo EGT in an old TD truck of mine. The engine was the veritable VW AAZ Td. it had some* pump tuning and extra boost and the EGT was what I 'tuned' it by. Basically, Anything above 700 degrees was in danger of starting to melt the pistons.

a steady 50mph on the flat saw EGTs around 200, and could easily hit 650 in 2-3 seconds if you booted it. It would then drop to 300 in just 2-3 seconds once off throttle. temps really do rise and fall that quick.

Proper gauges (real time) are often called 'worry gauges' for a reason!

*lots

Proper gauges (real time) are often called ‘worry gauges’ for a reason

Yep. An oil pressure gauge also adds a whole new level of worry.

I'm sure an actual mechanic who works on modern cars will put me right but the oil takes longer to reach temperature than the coolant. Roughly twice the time in the cars I've had oil temperature gauges in. I think it was a bit quicker in my current car as it's turbocharged, but the gauge is disconnected due to leakage.

So think about that before the Italian tuneup.

Depends if you have a sandwich plate as factory fit.....

But yeah, if you're gonna thrash it let it warm up first

Depends if you have a sandwich plate as factory fit

I've noticed little difference between a 'sandwich plate' and external oil cooler, on the same engine.
Oil temp always lags, wether that's an issue with modern oils/engines or not I don't know. I'd imagine not