The XUD9TE engine and its power characteristics

XantiaMan · Post by **XantiaMan** » 05 Oct 2007, 20:47

I've been getting used to my Xantia and the way it drives and was wondering if my car is typical of how these engines perform.

I have tweaked the fuelling slightly, half a turn on the boost compensator and turned the starwheel just over a quarter, plus turned the diaprahgm from 2 to 3 o clock.

I am used to driving a Perkins Prima, a unit renowned for its perky performance so switching from DI non-intercooled to IDI intercooled will inevitably mean some difference in the way they perform.

I found the DI Prima would respond from virtually idle speed, picking up very quickly, peak torque was 2500rpm according to the book although peak of 116lb ft (standard! mine was tweaked so closer to 130lb ft if not more) is reached much lower than the XUD although the peak is higher.

I've played with the fuelling, but cannot get this same 'response', in fact its flat below 1500rpm, you can then hear and feel the engine spooling up quite quickly and then it pulls strongly from about 2200rpm to 4400rpm, power drops sharply over 4400rpm, i never take it to the redline because its wasting time.

It does seem to rev quite well in the lower gears, the Xantia is quite a heavy car aswell so maybe i am expecting more!

I will upload 2 short video clips shortly, one 25-70mph and one 0-60 ish to show you what it goes like, and if this compares well with your cars.

Gareth

XantiaMan · Post by **XantiaMan** » 05 Oct 2007, 20:59

25-70

http://s3.photobucket.com/albums/y97/MG ... deo027.flv

0-60

http://s3.photobucket.com/albums/y97/MG ... deo028.flv

Post by **CitroJim** » 05 Oct 2007, 21:07

Hi Gareth,

My experience of the TD is that it is pretty flat below 1500rpm.

I find that it does not come on-song until about 1800rpm, hits peak torque at about 2300rpm and stays good until about 4000rpm and then falls a bit flat after that. The low-speed grunt is very poor by expected diesel standards although once it is up on boost it'll pull out tree-stumps.

The turbo spins in a bit late really for a diesel. What you are experiencing is normal.

The 1.9D (Normally Aspirated) is very much different. It has grunt aplenty from idle although it runs out of breath really badly at about 3500rpm and then promptly falls on its face.

When I drive my TD (rarely these days) the lack of low-down grunt after my Activa always catches me out very badly to the extent I can make it kangaroo-hop. The Activa CT engine is a strange petrol engine that has diesel-like grunt from idle right up to the red-line though.

MikeT · Post by **MikeT** » 05 Oct 2007, 22:31

It seems more rapid than mine, does yours have a cat' fitted? I don't think I get such an agressive acceleration as it comes on-boost and definately not as much from 3.8krpm

Post by **Peter.N.** » 05 Oct 2007, 22:40

I always thought all XUD engines were the same, but apparantly not. My wife had BX TZD estate and it went like a train and pulled smartly from anything over 2,000 rpm the acceleration was better than my XM! She now has a 1.9 td ZX estate, smaller car, bigger engine and it drives like a petrol engine with no real pull until about 2,500 rpm - very dissapointing.

Xaccers · Post by **Xaccers** » 05 Oct 2007, 22:43

Different gearboxes?

XantiaMan · Post by **XantiaMan** » 05 Oct 2007, 22:57

MikeT wrote:It seems more rapid than mine, does yours have a cat' fitted? I don't think I get such an agressive acceleration as it comes on-boost and definately not as much from 3.8krpm

Nope no cat, its a 97 model so things like gearbox ratios should be the same. I have disconnected the EGR aswell, and its running on a veggie mix, only about 25% at the moment though.

MikeT · Post by **MikeT** » 05 Oct 2007, 23:14

What's the bhp rating of yours, mine is 92 partly due to the cat'? Do you know which turbo you have fitted? Obviously you have a bosch pump, is it purely mechanical or do you have the throttle position sensor etc?

Mandrake · Post by **Mandrake** » 05 Oct 2007, 23:24

citrojim wrote:My experience of the TD is that it is pretty flat below 1500rpm.

I find that it does not come on-song until about 1800rpm, hits peak torque at about 2300rpm and stays good until about 4000rpm and then falls a bit flat after that. The low-speed grunt is very poor by expected diesel standards although once it is up on boost it'll pull out tree-stumps.

The turbo spins in a bit late really for a diesel. What you are experiencing is normal.

I'd have to second that too - my mum has a 1993 1.9TD, and the performance is, well, underwhelming in my opinion.

Yes it is quite zippy between 2500 and 4000 rpm, but below 2500 its pretty flat, with no boost, and wont pull usefully below 2000 at all. Also above 4000 rpm it runs out of steam quickly.

Comare that to my 2.0i 8 valve petrol which is almost opposite - strong pulling below 2500 rpm right down to about 1800rpm, (will happily chug up hills with little throttle at 1800rpm in 3rd doing 50Km/hr even though its an auto) a bit flat in the 2500-4000 range, and quite zippy from 4000-6000.

The 1.9TD definately doesn't have the "expected" diesel characteristic of strong low rpm pulling - and anyone expecting that will come away disapointed...

(Then again, it IS only 90bhp after all, in a 1300Kg car)

The subjective driving experience for me in a 1.9TD is "wow what a narrow power band" and lots of gear changing required...(in contrast to the very wide useful power band of the petrol)

Regards,
Simon

Post by **Peter.N.** » 06 Oct 2007, 08:51

I think that all diesels except the very new ones are flat below 1,500 rpm or even 2,000. The maximum torque occurs at about 2k as does maximum turbo boost although the 2.1 starts to go at around 1,800 and the torque is already pretty good without the turbo.

xac - possibly the gearbox is different but that shouldnt alter the revs that max torque comes up at - very strange.

XantiaMan · Post by **XantiaMan** » 06 Oct 2007, 08:54

MikeT wrote:What's the bhp rating of yours, mine is 92 partly due to the cat'? Do you know which turbo you have fitted? Obviously you have a bosch pump, is it purely mechanical or do you have the throttle position sensor etc?

I think originally they were rated at 92 PS?, this must have lowered with a cat but im lucky i dont have one, i've no idea what turbo i have, got a feeling its a Garret though but wont know until i've tweaked the boost a little, this will compensate for wear over the years rather than anything else.

My Bosch pump is what i would call mechanical, it has a TPS but then so did my Montego.

I think the 'throttle' linkage is also to blame with its damper and plastic bits, which appears to slow down movement at the lower end, the Perkins pump had a direct cable and metal linkage, its something i may look into.

Yes it is quite zippy between 2500 and 4000 rpm, but below 2500 its pretty flat, with no boost, and wont pull usefully below 2000 at all. Also above 4000 rpm it runs out of steam quickly.

I wouldnt say mine is as bad as that, from 1500rpm it will pull and obviously without a VNT boost wont be produced that early anyway, compare to a VW PD which produces maximum torque around 1500 when ours are just getting going!

It's definatly an old school unit, in a 306 or ZX, impressive because it produces a decent amount of mid range and in a lighter car, this makes a difference, the Xantia is a bloody heavy car too, appearances are deceptive.

The best thing about it though is how smooth the engine actually is once going.

XantiaMan · Post by **XantiaMan** » 06 Oct 2007, 10:35

Just removed the throttle damper and tightened up the cable so there was less slack, i now have a pedal that is as light as a petrol and response is better too. It really does pick up well from 1500rpm with decent boost @1800rpm until it reaches peak torque, stays flat and then power drops off at 4400rpm ish.

MikeT · Post by **MikeT** » 06 Oct 2007, 10:55

With the pump tweaks, are you producing excessive smoke at any point? If not, you could probably get a bit more power out of it. Did you look at the diaphragm profile to see if you were rotating it in the right direction and to the best position? The tip that rides on the cone to control the fuelling ends up marking the cone so you see exactly how far it rides up which can also be tweaked.

I really need to dispose of my cat!

XantiaMan · Post by **XantiaMan** » 06 Oct 2007, 11:38

MikeT wrote:With the pump tweaks, are you producing excessive smoke at any point? If not, you could probably get a bit more power out of it. Did you look at the diaphragm profile to see if you were rotating it in the right direction and to the best position? The tip that rides on the cone to control the fuelling ends up marking the cone so you see exactly how far it rides up which can also be tweaked.

I really need to dispose of my cat!

The smoke adjustment is only half a turn clockwise from standard, i've never found it to make much difference apart from produce excess smoke off boost.

The diaphragm and plunger has a small dint punched into the metal part, on mine this was at the 2 o clock position, i moved this to 3 o clock as you can see the wear point and gives a more aggressive profile.

The starwheel i turn clockwise and i find this gives the most gains, i read someone that it should be turned anti clockwise? I think this is wrong, i did clockwise on the Montego, i scribe a mark on the body and the wheel so i know where i've moved it to, the mark was at 12 o clock and the wheel now points to 3-4 o clock.

It smokes on boost yes,but there is no smoke without fire! It doesnt smoke more than say, a TDCI Mondeo flat out, but its not what i would call excessive.

I dont think there is any more power to be gained from it, adding more fuel is going to be a waste and produce just more smoke, i need to get more air in there aka more boost! Boost pressure always drops with age, 2psi is normal on most cars so i will compensate for this wear when the car is on a ramp at work because i dont fancy crawling on my back!

I dont want to make it a 130bhp smoker, i would be happy if it made a good 180lb ft and was reliable, with good bhp and good economy, i love an engine that is responsive to the pedal and with the tweaking i've done, its 10x better than when i first got it.

MikeT · Post by **MikeT** » 06 Oct 2007, 12:22

I have the semi-auto pump too, TPS with electronic advance control - not sure how much this affects power and if it can be improved.

The "smoke screw" is indeed a stop screw regulating off-boost fuelling and like you, I found it does little more than create excessive off-boost smoke though my car was so down on power it did make an appreciable difference to low revs driving, just not enough IMO.

The punch mark on the diaphragm is supposed to be indicative of the mildest profile I think, but in reality they vary wildly. Best to use it as a personal reference only.

The star wheel controls the spring tension acting against the plunger. I can't recall which direction lessens or strengthens it but the results are obvious - less tension allows the plunger more travel per given boost pressure.

You may have also noticed a nylon washer that seats inside the spring area? This is the plunger maximum depth stop. Some report great gains (presumably at higher revs) can be had by skimming it.

As you say, there's no smoke without fire and too much is just a waste so there has to be a balance. I prefer less smoke so am happy to have less power - for now. Mine certainly smokes less than many 4x4's and transits I've seen so I'm probably quite conservative in that respect. I'm wondering how inefficient my injectors are at 122K miles as I'm sure that must be having a detrimental effect on power and economy also.