No Black Smoke

MikeT · Unread post by **MikeT** » 22 Aug 2007, 11:50

I'm answering my own questions here as I slowly begin to realise how this mechanical marvel works.

The so-called smoke adjuster screw only affects the fuelling below or at atmospheric manifold pressure. Screwing it in or out alters the height of the eccentric cone (up=less, down=more fuel) but once turbo boost is applied, the daiphragm and eccentric cone is no longer connected or affected by the smoke screw.

Rotating the eccentric cone (requires removal of the diaphragm) changes the fuelling profile (mild to aggressive) over the entire range (on and off boost) which may explain why I'm seeing little difference adjusting the smoke screw.

The spring tension adjustment controls how much pressure is required to push the eccentric cone downwards (more fuel) in relation to the amount of turbo boost applied. Seems this and the diaphragm adjustment affects the same fuelling range but in a different way? I can't quite grasp the difference - does anyone know?

The protected max power screw, as Jim tells us, regulates the maximum amount of fuel that can be delivered at full power. I'm inclined to leave this adjustment alone for now until I've found the ideal settings for all the other adjustments first.

I'm thinking I should find the best power profile on the eccentric cone then maybe tweak the spring to control the smoke? Or should it be the other way round?

Unread post by **CitroJim** » 22 Aug 2007, 12:32

Excellent work Mike

The cone adjustment may be accessible without removing the diaphragm. There is an aluminium plug in the vicinity which you may be able to remove to rotate the adjuster. I'm guessing here though and when I'm home and looking at a dismantled pump I'll confirm.

When I have a few moments spare (I'm incredibly busy at the moment

) I'll pop some pictures of the pump up on here, both external and internal views.

Unread post by **CitroJim** » 22 Aug 2007, 17:18

Mike,

I've just had a look at the pump to see if there is a way to get at the cogged wheel below the diaphragm.

Yes there is

If you remove the vent plug just below the boost sense pipe spigot and just above the fuel return line, this exposes the cogged wheel which can be turned using a small, clean screwdriver. It is a bout half an inch in and you'll need a mirror on a stick to see what you're up to.

The vent plug is covered by a rubber cap with a tail on it which looks like it is an unused electrical connection. Pull this cap off and undo the plug using a 17mm socket. The plug is, in fact, the lower diaphragm vent which I suspect is an atmospheric pressure corrector and prevents the lower chamber pressurising under boost and upsetting calibration.

You should be able to do this with the pump in-situ. Easier than removing the diaphragm (and cleaner too

)

MikeT · Unread post by **MikeT** » 23 Aug 2007, 13:11

Hi Jim,

I'm now proficient at getting at the smoke screw, diaphragm and spring tensioner all in under 40seconds

I didn't stop to think about cleanliness

but judging by the carbon(?) on the eccentric cone and the grease around it I'm throwing caution to the wind and keeping fingers crossed. After all, as you say, that chamber is pretty much open to anything due to the equaliser air vent.

Yesterday I rotated the cone about 20 degrees for more fuelling and it's made a noticeable difference as well as a bit more smoke. She pulls quite well from under 3Krpm to well over 4Krpm so I'm back on track now and looking to get even more power out of her and then I'll look at smoke reduction.

While you're pondering the internals of the pump Jim, could you do me a big favour please? As you may recall, I showed interest in N2O injection and hope to get my hands on a kit next week.

I've read the fuel pump is capable of supplying all the additional fuel needed for up to appx 70bhp N2O boost (I'll be intially starting with a 10-20bhp jet). I would love to increase the fuelling on-the-fly, as and when needed, which doesn't seem possible, does it?

Anyone got any ideas?

Unread post by **CitroJim** » 23 Aug 2007, 15:38

Hi Mike,

Generally, you must be scrupulously (sp?) clean, almost clinical, when inside a diesel pump. They're real precision engineering and a bit of dirt in them can wreak havoc.

Now, the top of the boost sense diaphragm will be horribly oily and mucky from engine inlet tract fumes but below the diaphragm and around the cogged wheel it should be spotlessly clean and maybe just damp with diesel.

If you have oily dirt below the diaphragm you may have a split in it and this will really upset your on-boost fuelling. I noticed that the diaphragm is stuck to the lower chamber of the UFO housing to ensure a good seal so I've not disturbed it. I guess you've had your diaphragm out a few times now so a replacement may be a good idea especially as the cog ccan be adjusted without disturbing the diaphragm.

I'm soon to look into getting hold of some pump spares to do up Ian's so I'll look into the cost/supply of replacement diaphragms if you wish.

On the subject of NOS Injection Mike, I know of no way of upping the fuel delivery on the fly unfortunately. It really needs to be controlled electrically to coincide with the NOS injection. I could see a way to do this by electrically pulling the boost diaphragm down further but this would need rather major and radical mods to the pump. Alternatively, replacement of the maximum power screw (the one hidden behind the armour) with a solenoid operated plunger may do the job. Lots of experimentation needed Mike. It could be fun.

MikeT · Unread post by **MikeT** » 23 Aug 2007, 17:47

Jim, I understand the cleanliness aspect but if there's an open vent which will blow out as well as suck in, surely it can't be that critical around this cone but better to be safe than sorry I know.

The housing around the top part, under the diaphragm, is very clean for sure but there is some black (carbon?) deposits around the eccentric cone and has been greased where it slides through a nylon collar. The collar itself is pretty greasey with black deposits too.

The way the car is pulling now I doubt the diaphragm is split, it's pretty thick and tough but I'll examine it next time it's out. I'd give it good clean if I knew where I'm supposed to re-grease it. My diaphragm was actually wedged into the upper cover before I removed it but it easily peeled away and I make sure it's well seated on replacement.

RE N2O: I like the idea of the solenoid maximum fuel screw!

MikeT · Unread post by **MikeT** » 27 Aug 2007, 19:58

I have discovered I get best power with the eccentric cone rotated to it's most aggressive profile and although there's some smoke, it didn't seem any more offensive than other diesels I saw today (in bright sunshine - may be a different story at night)

I can now just about outrun a peugot 306 1.4

The cone spindle is now clean and the diaphragm has no splits so I'm happy there. What would you tweak next? I'm considering the spring tension or the max fuel screw which I've yet to find.