No Black Smoke

JohnCKL · Post by **JohnCKL** » 19 Jul 2007, 20:32

Thanks again for everyone's help in getting me this far, I'm pleased to know that I can now safely overtake the local rolling roadblocks. I even outdragged a Fiesta today

Give a new leash of life to our old Xantia TDs, don't it! Only thing is, we've got to rev up the power/turbo, otherwise pottering around slowly is not going making use of the tweaks. Now every so often, I'm tempted to rev faster than the speed limit allows. As for black smoke, it only comes on slightly during the initial driving. After its warmed up, less or no more black smoke for normal driving unless I rev its head off. Maybe more tweaks to come.

MikeT · Post by **MikeT** » 19 Jul 2007, 23:19

citrojim wrote:No.1 Cylinder on all XU(D) engines is totally against standard convention Mike and is nearest the clutch.

I had a 50/50 chance of getting it right first time

A '98 Xantia certainly should have a semi-electronic pump. Does it have a pot with three wires emerging from it on top of the pump Mike? If so then it'll have a needle lift sensor.

Yes, I have a throttle position sensor? - sitting on top a hardened foam type spacer that's seen better days - though the BX manual says this was introduced first for the exhaust gas recirculation, which I also have fitted. The manual goes on to describe the next electronic introduction which I didn't recognise so stopped reading at that point.

Otherwise there is something strange with yours.

You can say that again

This car has not been serviced the Haynes way, I can assure you, some assemblies have not been refitted as a reversal of removal

MikeT · Post by **MikeT** » 20 Jul 2007, 16:42

JohnCKL wrote:Only thing is, we've got to rev up the power/turbo, otherwise pottering around slowly is not going making use of the tweaks.

All other diesel's I've ever driven had good torque from idle but these xantia's (or at least mine) seem sadly lacking. I'll try tuning off-boost next. I also read that nitrous injection practically illiminates turbo-lag as well as giving an initial power boost like - as Citrojim called it - a grenade

Now every so often, I'm tempted to rev faster than the speed limit

I'm always tempted to discover a vehicles limits

As for black smoke, it only comes on slightly during the initial driving. After its warmed up, less or no more black smoke for normal driving unless I rev its head off. Maybe more tweaks to come.

Cold starting requires a rich fuel mixture hence.

It's always been the case that production cars are de-tuned. Mine did not make black smoke at any point before I tweaked the fuel pump.

jeremy · Post by **jeremy** » 20 Jul 2007, 16:56

Diesels don't have a fuel mixture as such. They work on the principal of free air - and the idea is that there is always enough air available for complete combustion - hence the economy,

The speed (and hence power) control is simply by control of the quantity of fuel injected.

Cold start is assisted on mid 90's diesels by advancing the timing by an electrical device. This gives a faster idle as well which was formerly achieved by opening the throttle a little. Advancing reduces smoke which is why it was adopted.

Maximum power is produced just before black smoke is produced ie when all available oxygen has been used.

The chemistry of laughing gas (nitrous oxide) is such that it will release an oxygen molecule which is then available for combustion. It won't burn on its own but could burn some spare fuel - ie excess diesel which would otherwise have produced smoke.

MikeT · Post by **MikeT** » 20 Jul 2007, 17:35

Thanks Jeremy, that's what I meant

I've spent too many years with petrol engines and haven't fully grasped the diesel engine yet.

Was I right in saying more fuel is needed for cold starts, however it is achieved?

Is it wrong to look at the fuel/air ratio as a mixture? I understand the air volume is constant/fixed and that fuel must be increased for more power but is it misleading to call it a rich/optimim/lean mixture?

I am most interested in using N2O in a turbo diesel as it has so many advantages over a petrol engine - especially for a beginner like me

I'm not looking for mad power increases due to the risk of engine damage but I like a bit of surplus power when required.

MikeT · Post by **MikeT** » 20 Jul 2007, 20:22

citrojim wrote:I cannot recall at this point if you have checked for the correct functioning of your Needle Lift Sensor but I'm sure you have. If not disconnect it whilst the engine is running and listen for a change in engine note. If none then that is your problem.

Ok, yes, I do have a lift sensor, it's got a skinny little wire that runs to a connector which I unplugged while the engine was running and it almost stalled. It sounded so bad I thought something was breaking

Did I give the impression my engine was running that rough?

Kowalski · Post by **Kowalski** » 21 Jul 2007, 00:01

jeremy wrote: Maximum power is produced just before black smoke is produced ie when all available oxygen has been used.

Maximum power is produces when all available fuel is used, but diesels tend not to be very good at using all the available oxygen unless you overfuel them, I'm told that maximum power for a diesel is at about 10% overfueling, have a look on Youtube for diesel dragsters......

Xaccers · Post by **Xaccers** » 22 Jul 2007, 07:26

Been discussing nitrox with a guy at work, and also propane.
Tempting..... must resist urge....

Post by **CitroJim** » 22 Jul 2007, 07:48

Xac wrote:Been discussing nitrox with a guy at work, and also propane.
Tempting..... must resist urge....

Propane, now that is seen as a good diesel tuning mod. One company offer a kit commercially as a way of boosting power on a diesel. In fact, a lot of heavy industrial diesels are designed to run on a mix of diesel and LPG.

The propane is injected down the inlet tract using the same technique as used to convert petrol engines to LPG.

Question is, what are the excise duty implications of say, running on Calor Gas? Is that exempted too in line with SVO?

MikeT · Post by **MikeT** » 22 Jul 2007, 20:02

Xac wrote:Been discussing nitrox with a guy at work, and also propane.
Tempting..... must resist urge....

It'll eat away at you, why resist?

But seriously, if you're going to need extra fuelling from propane, you'll be in the engine-at-risk range of increased power (so I've read). The Bosch pump can deliver some excess fuel, which I'm hoping is enough for 30-50BHP increase (max). It may be worth installing a dry N2O system just to eliminate turbo lag alone.

Xaccers · Post by **Xaccers** » 24 Jul 2007, 21:02

citrojim wrote: Question is, what are the excise duty implications of say, running on Calor Gas? Is that exempted too in line with SVO?

Alas no, as a fossil fuel it's not duty free, though lpg has a lower rate.

Oh nearly forgot to mention, leaving the battery disconnected for 5 hours not only has given the car more ooomph but seems to have improved the fuel economy.
Will do a full check once I've been paid next week

So hoping it's more than 33mpgal!

MikeT · Post by **MikeT** » 16 Aug 2007, 14:06

Thought I'd update this thread rather than create a new one....

To recap, I thought the car was underpowered and tried a few fuelling tweaks. I got best results by rotating the cone plunger which seems to offer different fuelling profiles over the entire range, dependant on the position you set it to. But this also created far too much smoke so it's been reduced a little - pity.

However, the "smoke adjuster" (or "off-boost" power) screw doesn't seem to make any difference at all. I've increased it by over 5 turns in total over the last few weeks and it makes no discernable difference to off-boost power nor does it create additional smoke. When the above mentioned cone adjustment created too much smoke I tried decreasing the smoke adjuster to compensate but it didn't reduce the smoke

Does anyone know exactly how this adjustment works and affects the fuelling? Should I just keep increasing the screw until I get smoke or will going too far break something?

http://dodgeram.org/tech/dsl/more_power/Power_ve.htm

Post by **CitroJim** » 16 Aug 2007, 22:22

Mike,

That is interesting

Having a pump in bits, I can see exactly what you're adjusting.

The "Maximum Smoke" (power) screw adjusts by how much the centrifugal governor can move out and therefore adjusts the absolute maximum amount of fuel that can be delivered to the injectors. This is quite a coarse adjustment. The boost sense adjustment does the same thing but the control is much finer and works over the full range of the pump delivery adjustment. In effect it is a second throttle control and actually works on the same lever. This is why the power screw seems to make little difference as it is concerned with the extreme end of the range and the boost sense makes a lot of difference.

Basically, however much you adjust the power screw, you're not going to damage anything, even if you take it right out, you'll just leak diesel! It is the same with the boost sense screw, you won't hurt anything. The only risk is that if you overadjust the power screw, you may cause overspeeding at full throttle off-load which could be a problem at MOT time. You really need to adjust your maximum speed screw to ensure that it won't speed past the redline off-load.

The governor is there to regulate maximum fuel delivery under all conditions and is there for two reasons: Firstly to guard against overspeeding. As the pump speeds up due to increasing engine speed it will naturally deliver more fuel, which in turn will cause more engine speed and more fuel and eventually BANG! The governor stops this happening. Secondly, the governor regulates against excess smoke under heavy load.

The speed of a diesel engine is directly related to how much fuel is injected and under light load this speed can soon rise above danger point unless governed back.

The throttle arm, connected to the pedal, operates an arm via a set of springs that adjusts the pump delivery rate but this arm is also connected to the governor and at all times the governor has overall control so even if you have foot hard down and the governor says enough is enough it takes charge. Even though you're foot hard down the governor actually backs off the throttle for you. You control fuel delivery through springs and the governor does it through a solid rod!

Your pump Mike, must have either no armouring or a different sort to the pump I have in bits. On mine, the power screw is normally hidden and inaccessible behind the armouring

XantiaMan · Post by **XantiaMan** » 19 Aug 2007, 13:11

On my old car, adjusting the boost compensator screw did virtually nothing on its own, it needs to be combined with further tweaks to the cogged wheel inside and the metering pin. Once you've done this you'll find it makes more of a difference especially to smoke.

MikeT · Post by **MikeT** » 21 Aug 2007, 07:17

citrojim wrote:Your pump Mike, must have either no armouring or a different sort to the pump I have in bits. On mine, the power screw is normally hidden and inaccessible behind the armouring

Hi Jim, according to the link given, I meant the smoke adjuster (off-boost, below or at atmospheric manifold pressure) screw, not full power adjustment screw.

The smoke adjuster (torx) screw I'm referring to sits under a cap on top of the diaphragm and is held by a 13mm locknut.

I'm going to take a few steps back to when I had good turbo boost but excessive smoke and take it from there.