Deisels And Heat....

Has anyone noticed you lose a staggering amount of performance in the diesels on hot days ?? Last week it was 47degrees C .... The damn XM struggled to pull it's heavy @rse up hills with the air-con running full bore....

It's now a balmy 16degrees C (yes, gone from air-con running 24hours a day to jumpers and heaters on within a few days ).... Well the XM has grown another turbo or two the way it's moves now... Bloody thing is absolutely flying again.... it would nearly as quick as the CX ...... if I unplugged one of the coil packs

Surely it's not just the air-con the dramatically changes it's performance so much ?? My guess is the intercooler gets massively heat soaked and intake temperatures skyrocket ?

seeya,
Shane L.

What's this "hot day" you speak of?

You know .... 47degrees Celsius, blasting northerly horrendously hot winds... many fires ... many people dead from said fires.... thousands of houses burnt.

We have had a lot of hot days recently. 47degrees (in the shade) with blast furnace winds needs to be experienced to be understood

seeya,
Shane L.

Hi Shane.

I'd guess you are certainly right about the intercooler, plus I would imagine the temperatures you're having out there are probably getting to the upper end of whatever the ECU is designed to recognise as an air intake temp. At some point, in excess temperature, the ECU will shut down the air con.
I think it's perfectly true that they all run best on cool, damp days.

Mike.

I've noticed how the SNOW and FREEZING weather makes the LPG sluggish.

Maybe we could swap?

Sorry to hear about the disaster, truly awful.

Steve.

Our hot days are in somewhat of a different league to Shane's.

I don't know how much the aircon knocks the performance on a 2.1 - not even having it on the 2.5, but it must have a small effect.

Is it to do with how much oxygen is in the air at the time? Doesn't colder air tend to be more oxygen rich which a diesel will like more?

Hi Steve.

Fascinating area (my goodness, we're a sad bunch aren't we ?!)

We currently have three LPG trucks around, all on carbs, so no electronics at play -- and the colder ambient temperature doesn't seem to make a haporth of difference.
Does yours have a conventional vapourizer --- if so, you do want to check the coolant flow through it is spot on, because they can ice up in a very short time, especially from a cold start -- possibly accentuated, depending where fitted, by a low ambient temperature. This would certainly impact on performance. Other key and very simple point is to keep the tank well filled. If it's low, it doesn't seem to deliver qiuite as well for sharp acceleration.

Mike.

Er... my droll comment was more because we've had the biggest snowfall in twenty years and some of the lowest temperatures - reports today were that an additional 6,000 people had died this winter compared to last. Combined with a crappy summer I don't recall the last genuinely "hot day".

Let's keep this light hearted, eh?

I think it's to do with expansion isn't it?

Air expands as it heats up, so cold air will expand more than warm air when it ignites in the combustion chamber, resulting in greater compression (more power), hence the reason for the intercooler.......I'm no expert though, so I could be talking b****cks

Hi Mike,

It's causing me some problems at the moment. More details in this thread - http://club-xm.com/forum/index.php?showtopic=4470

Thanks for the tips.

Steve.

Its all to do with air densitity, the colder the air the more oxygen, nitrogen and all the other gasses you have to the cubic foot, that's how the intercooler works by giving you a more dense charge. Heat the air up and not only is there less oxygen but the intercooler becomes less efective in cooling it.

I have always found that my MPG gets dramaticaally worse in cold weather and much better around 25 degrees plus, not that this happens much around Peebleshire. Is this just me or does anyone else have the same experience?
Cheers,
Dod.

The engine should run more efficiently when the air is colder but at the same time it makes the oil thicker both in the engine and gearbox, which could affect the fuel consumption on short journeys.

Even my wife is commenting on the car going a huge amount better.

Possibly all the heat and the XM dragging the trailer back home has decoked it a bit too. I don't trust 4th gear, so used 3rd at 2600-2800rpm all the way home (which is a lot higher than the god awful slugomatic ever allows the motor to rev).

With your LPG, have you filled the tank somewhere different ?? My uncle does LPG conversions on cars for a living. A few years back the fuel companies were messing with the LPG. The propane content apparantly give lines pressure. So if they drop the propane in the mix back a bit, it play havoc on the cars tuning as the line pressure drops.

The converter would turn to a solid lump of ice in minutes if it didn't have a decent flow of coolant through it I wonder if you can use the "cold" produced by the converter to somehow "freeze" the intercooler .... That would considerably improve performance !

seeya,
Shane L.

Hi Shane,

The car's new to me so it's only had a couple of fills since I've bought it. As far as I can tell it's a DIY install of a good kit. It maybe the ECU was never setup correctly after it was fitted.

It's a BIGAS SGIS-N multipoint sequential kit. Following a large amount of searching/reading and a small amount of effort it's now running much better. I closed the plug gaps down by just over 0.2mm to 0.55mm. Setup the vapouriser pressure, installed the config file for the Peugeot 406 2.0 Turbo (RGX engine), altered the injector types to suit, ran the autocalibration and with a slight tweak to the mixture at idle it's much better. At some stage I'm going to get a friend to drive it whilst I tweak it at other rev/load settings.

Interesting thought but providing enough heat when not on full boost could be a problem, a dual stage vapouriser that used the intercooler first as an heatsink might be OK or how about a phase change liquid to air intercooler? It would be easier with a water/air type such as used by the 2.5 TD.

Steve.