bosch ve diesel pump adjustments

deian · Unread post by **deian** » 25 Oct 2009, 11:22

myglaren wrote:
citroenxm wrote:
deian wrote:Also think of the 'broad' legal consequences, if someone sees you overtaking another car splurting out loads of black smoke, and you end up having a crash, then eyewitnesses may mention the black smoke and the cops/insurance company will check the car over and may find your tweaking skills on the pump, your insurance may become invalid etc etc (you will stand deep in it)... there may be a big can of worms there, just a warning, nothing to do with me.

Well what about all those DIRTY Ford F@@Kups, which seem to CONSTANLY smoke all the time when they put their foots down, and those horrid 4x4 Disco's with the TDi's Ive never seen anything smke worse, CERTAINLY from a PSA car!! I dont think a car you be passing would even bother about the smoke out the back as all older "mechanical" DERV engines smoke under hard acceleration! EVEN Original VW TDi units....!

Paul
It never fails to amaze me the amount of black smoke that VWs & Audis kick out where mine doesn't. They aren't accelerating any faster either.

All true of course, but I have generated a lot of smoke recently! I will have to show paul sometime, he will love it.

MikeT · Unread post by **MikeT** » 25 Oct 2009, 12:27

May I just clarify and add to what Jim's been telling us about these marvellous pieces of engineering?

The "smoke screw" that sits in the middle of the LDA (the flying saucer or UFO) is a stop screw that pre-sets the boost enrichment pin starting position. It's role is to pre-set where the boost enrichment point starts from (before boost moves the enrichment pin downwards). It has no effect on-boost other than to set the starting point.

Therefore, this meagre screw can be tweaked to provide more or less fuel before boost takes over control. As fuel makes boost, this screw can be used to get the turbo to begin spooling sooner (or later) and only affects very low revs. It is said that screwing this downwards improves intitial response at low revs and accelerating from standstill. I don't know when boost takes over but I would guess this screw is key from idle to about 1250RPM.

I hope to give more detail in my pump rebuild guide as they say, a picture paints a thousand words.

Old-Guy · Unread post by **Old-Guy** » 25 Oct 2009, 14:22

If your diesel Xantia seems down on power, here's a cautionary tale.

I was tempted to go down this route to restore the power on my 1.9TD.

Quite separately, I couldn't find an annoying slight oil weep somewhere in the region of the air pipe joining the inlet manifold. "Aha!" I thought, "Leaking oily air and losing boost pressure. No, that doesn't make sense, it would have to be one helluva leak to make that much difference?" Wiping up the mess yet again, I felt something strange on the underneath of the pipe that connects the air pipe to the LDA on the pump. The little sucker was well-and-truly split!

It being a Sunday, replaced it for the time-being with a length of rubber fuel pipe and took the car for a drive. Complete transformation!

I suspect that it had been split ever since I'd bought the car and been getting gradually worse until no pressure at all was reaching the LDA.

Unread post by **citroenxm** » 25 Oct 2009, 18:55

NOW thats ALSO something I can confirm!

My TD was a little dead, and wouldn't go up a 45 deg gree angle hill (I think it is roughly..) in 3rd at 30mph, it would just diiieeeeee..... however, after cutting the splits off the ends and re fittingthe pipe she'd now PULL up the hill in 3rd from 30mph.. made a big difference..

Paul

MikeT · Unread post by **MikeT** » 26 Oct 2009, 11:52

I've started a guide to stripping this pump and have just covered the very setting you're referring to Dei, if you'd like to take a look. http://www.frenchcarforum.co.uk/forum/v ... hp?t=28590

deian · Unread post by **deian** » 26 Oct 2009, 11:59

That's another fantastic resource. Very interesting stuff, all that from one pump!

MikeT · Unread post by **MikeT** » 26 Oct 2009, 12:06

Anyone's welcome to copy it to their site if they like. Although I can't take credit for the knowledge (it's all out there in cyberspace), I would appreciate acknowledgment of my part in the work.

deian · Unread post by **deian** » 26 Oct 2009, 12:17

Seeing as you know a hell of a lot more than I do... if you get to the limit of fuelling does the engine cut out like it would on a petrol car, i.e bounce off the limiter kind of thing?

I pulled out today and caned it in 1st and I'm sure it bounced off. These 1.9td's can be too quick with the 'wrong' adjustments!

Unread post by **CitroJim** » 26 Oct 2009, 12:49

Not really Dei, there is no rev limiter as such except for the governor saying that's it you're having no more fuel over and above what I'm prepared to give you.

I've seen the effect you describe though and in theory it should not happen as the governor should hold the engine at max. revs and that should be it. This is my take and I'd appreciate your comments on this Mike...

You're accellerating hard and heading for the the red-line. You're into the area of engine running where pumping losses are very high (actually the rev. and power limiting condition for a diesel) and the governor say's that's yer lot. The engine is still speeding and revs past the set rev limit. Fuel is reduced by the governor relative to the needs of the engine at that speed and it stumbles badly due to the aforesaid pumping losses. This reduces it's speed to just below the limit for the maximum delivery of fuel as set by the governor and off it goes again, possibly to repeat the cycle several times and thus feel as if it is bouncing off a limiter.

Tweaking ther pump appears to make the effect more pronounced.

All just a theory mind, I may be talking cobblers.

Pumping losses are high in a diesel because of the very high compression ratio. The engine has to do serious work to compress the charge at high revs and to the engine it looks like friction. A lot of potential power is lost and this determines more the realistic rev limit for the engine rather than any physical limitation. It makes 'em run hot and is another reason there is little point in screaming a diesel to the red-line.

Unread post by **citroenxm** » 26 Oct 2009, 13:05

Have you EVER stopped and thought exactly HOW much compression an XUD does??

The pistons come to the VERY top of the bore, sometimes more often then not prtude a mm or two - ok?

The cylinder is of FLAT design, were the valves are NOT recessed and are level with the bottom of the head..

The HEAD GASKET is the ONLY gap between the piston and valve or head base!!

Ive never measured the depth of a piston when FULLY lowered, about 120mm?? and compresses the drawn in air in that quantity into a space of about 5mm MAX!!! (Im NOT useing quoted Bore and stroke figures by the way)

I think the compression this engine does is ABSOLUTLY amazing!! If no one has done it by the next head off job I do, Ill do some measuring unless someone else already has..

** Sorry Jim, distracting from the Important Fueling issues, but just thought Id put it in..

Paul

Unread post by **CitroJim** » 26 Oct 2009, 13:23

You're right Paul, it is pretty amazing stuff and amazing too how the engine stays in one piece and lasts for ever almost

Having said that, look at the bottom end of an XUD9 and it makes brick outhouses look a tad on the flimsy side.

I think you have also very clearly demonstrated the reason for the high pumping losses

deian · Unread post by **deian** » 26 Oct 2009, 14:24

you both make sense of course, i won't be revving it like that in a hurry, although the typical flat spot that is a characteristic of diesel engines is not there on mine

Unread post by **citroenxm** » 26 Oct 2009, 15:06

Flat spots - eh?? Whats these?? Not heard of those before,

I thought they were a Petrol Specific things when those things, um, I think they call them spark plugs?

are not changed at the right time... or something of the like

Not sure I know what a flat spot is on a DERV.. Dead spot maybee, when the turbo is asleep..

Paul

deian · Unread post by **deian** » 26 Oct 2009, 16:40

The bit after the turbo is on full boost... i.e after about 4500rpm, dead spot, flat spot, whatever. I know you're a big fan of diesels.

MikeT · Unread post by **MikeT** » 26 Oct 2009, 18:37

deian wrote:... if you get to the limit of fuelling does the engine cut out like it would on a petrol car, i.e bounce off the limiter kind of thing?

I pulled out today and caned it in 1st and I'm sure it bounced off. These 1.9td's can be too quick with the 'wrong' adjustments!

That sounds about right Dei - first gear is way too short for "normal" driving, I think it's more aimed at the caravanner than the sports enthusiast

In fact, when it's tuned, you'll find you run out of gears very quickly and realise you're way over the speed limit too

In fact, when the boy racer behind sees you move he, thinks Ah, a race! but by the time he's finished slipping the clutch to catch you, you've de-clutched, the car seemingly brakes and matey behind nearly rear-ends you as his torque curve kicks in - watch their faces in the mirror if you can, it's sort of funny 8)

That's why I'm always on the lookout for an alternative gearing - an auto 1.9TD sounds a likely candidate - shame they're so rare!