1.9D N/A under hot conditions

[white exec]

Done enough driving of our 1.9D non-turbo now to realise that engine power drops off noticeably when outside temperature exceeds 29/30°C, and separately from the power sapped by the AC compressor. Have put this down to reduced air density at that temperature.

Oddly, our previous 1.9D — an '89 XUD9, rather than the current '92 XUD9A — didn't suffer from this, even when towing an 860kg caravan across Spain (and across the Picos de Europa) in temps of 40~45C.

The car runs completely without smoke, so could max fuelling just be set a tad low? Pump is Bosch.

[xantia_v6]

If it not smoking at full throttle, then I don't think that the problem is due to a lack of air.
I wonder if the pump might be losing efficiency when the fuel is warm and thinner?

[Jaba]

Try tweaking the fuelling until you get smoke then back it off a bit to prove your theory of underfuelling. If no different then you can always go back to the original setting. What about the altitude on your mountain roads . My BXs are gutless at 1500/2000m at any temperature.

[white exec]

Thanks, John. Will look at the fuelling. Am reading my way through the Bosch VE Pump instruction guide.
Altitude here only 450m above sea level, and lack of oomph can be there even at sea level (10km away).
Ambient air temp seems to be the problem: lots of go at 26-27C or below, but significantly less at 31-32 plus.

Went out this morning at a (very welcome) 22C, and car was decidedly swift (as these things go), as it always is on cool days.
Performance is not changed by the engine getting up to full working temp, so I'm hesitant to put it down to simply a 'hot pump' problem. I think pump temp is always around 60C, but will check that next time it's warmed up.

The other issue I have is idle speed being ok, but dragged down unacceptably by the AC being turned on or running.
The BX diesel appears to lack the "idle up" solenoid which the injection petrols have, and which operates when the compressor switches on. Is the diesel idle speed just supposed to cope? Should the all-mechanical pump not respond to a lowered idle speed?

The lack of power on hot days occurs even when AC is off.

[Jaba]

Idle speed: Just a thought have you checked the anti stall setting? When I had a TD with aircon it coped very well at tickover when the compressor kicked in. The revs drop was noticable but very small. I probably had it set a bit high to cope.

No further ideas about the heat issue I'm afraid.

[white exec]

Great minds... Have just been browsing Haynes, and it's possible the anti-stall hasn't been properly set.
Will also check cold and hot idle settings. At least I have a non-contact tacho now, which makes the job possible.

PS Was the steering wheel ind.canx. detail any use?

[rutter123]

My guess would be if the car left the factory with 70hp ish at best, over 30 odd years its prob lost a few pony's add Yr aircon add Yr outside temp, add the mountain climbs and thinner air, I reckon Yr getting 50/55hp at best, what you need is a TD.

[white exec]

Well, thanks for that! Beg to differ, though...

Our previous 19D NA went from 35k miles to 177k miles with us, and was as spritely the day we hung it up (for the XM) as the day we took it on. It also towed 860kg all over the place, including up Sierras and Alps, without complaint. The fall-off with altitude was quite minor, compared with what's going on now. Ambient touring temps ranged from -10 to +44C, neither of which seriously compromised.

At around 135k miles, I had the head off to replace it (it had gone through two HG's), and found virtually no wear on the bores or valve gear.

The XUD, and probably the less-stressed NA more so, is essentially good - I reckon - for 350k, maybe 500k, miles if properly serviced, looked after, and not over-heated. We ran ours on 20W50 mineral, changed every 6000mi.

These diesels, in any case, are not properly run in and loosened up until they have around 40k miles on the clock, and our Millesime is now showing just 171k km (110k miles), so hardly into wear. Compression is good, starting instant, pulling power no problem - when outside temp allows.

Forget the air-con: the lowered power is a problem even when it's off.
Our altitude shouldn't be a problem (see previous post), and the power issue exists even at sea level, when the temperature climbs.

TD is good, absolutely. We have a DK5ATE 2.5TD here, with enough bhp and massive torque to see off even quite sporty and large-engined stuff. The BX was bought for something else, and it will get sorted.

[white exec]

Anti-stall checked this morning, and found to be miles out, with insertion of a 1mm feeler gauge adding no revs at all.
Cold idle was ok.
Hot idle was ok at 816rpm.
Waxstat and its cable operating properly.
Anti-stall screw wound in (to what looks like an original position, judging by the remains of yellow paint) to give +50rpm (866rpm).
Throttle cable reset, and min/max at pedal = min/max at the throttle lever.

Noticed that the first 20° or so of the main throttle lever rotation produced no increase in engine revs. This 'dead' now eliminated by the anti-stall screw being reset. (Previously, max throttle opening was obtainable.)

Hot idle 816rpm.
When AC is turned on, revs drop to c.776, which seems acceptable, and an improvement.
Will see how things go...
__________

Good few web articles and papers confirm the reduction in output power of diesels when intake air temp rises is more marked with NA engines, and is most noticeable at higher engine revs - just when you're looking for extra power! Effect of altitude below 1000m is limited.
Confirms lengthy experience of diesels running at their best in cool/damp conditions, presumably when oxygen density is higher.

[white exec]

Just found this. It's all here somewhere!
viewtopic.php?p=122012#p122012

Looks as if previous hands might have been adjusting idle speed with the anti-stall screw.
Does look to explain the car's depressed idle speed when extras (like AC) are turned on, and not wanting to crawl easily in slow-moving traffic.

"Why was that post still there, after all those years?"
"Well, you've been a long time coming..."

[white exec]

Quick 8km drive out tonight, and the pump adjustments look to have paid off. Much smoother throttle action when moving away from rest, or coming to a halt.
Thought I'd try the suggested test of a moderate incline, 1st gear, and foot off the accelerator. Car just progressed smoothly up the hill, no stalling or faltering. Gosh.

[Jaba]

Result!
On to the next problem now hehehe

[Tim Leech]

Could you not fit an intercooler?

[white exec]

Tim, I think an intercooler would only be cooled by the same ambient temp air that the NA engine already breathes, and add intake drag, so no gain. Intercoolers only come into their own when bringing down the temp of turbo-compressed (and therefore heated) air.

Adjusting the anti-stall correctly has improved the idle with AC on, and smoothness of pull-away, but still a bit low.
Might try increasing fuelling slightly as an experiment.
Might also add some kind of "idle up" mod (eg a solenoid) to pull fully on the cold-start lever when the compressor comes on. Tried doing this by hand the other day (AC on and a very hot day and engine), and idle came up to a decent figure.

Really should have the injectors serviced/calibrated, as I doubt they've ever been done, although they have had a dose of injector cleaner earlier.

[Tim Leech]

Do you have a short nosed or long nosed bonnet, the short nosed have a small grille above the bumper line which may aid cooling