Hot day under load performance

[matt_91]

So I just got back from a 3 day trip from Melbourne to Queensland return to pick up a car and tow it back. All up, we were a bit of over 4 tonne on the return trip.

Car did great, didn't think we'd be doing 110+ on the return (loaded) trip but the nav did really well.

Coming back into Melbourne we got onto the Hume around Seymour which gets a bit hilly in places. It was also 38 degrees up there.

My question is basically this, does anyone know if these things detune themselves as things warm up, because it started to feel quite sluggish even on the flats once we were in those conditions where earlier in the day when it was sitting on about 30 degrees we were overtaking people on the Newell with ease.

If the temp gauge ever moved from normal it was too small a movement to notice, but just thought things may have been getting a bit above normal so it started retarding itself a bit.

 

[Black_Outlaw]

If it's programmed anything like a petrol engine, as soon as the IAT (Intake Air Temps) rise it starts pulling timing and as a result power is compromised..

Id say with the hot air and a heat soaked Intercooler it would have pulled quite a bit of timing out..

However, I am sure someone more inept at Electronically Controlled Diesel Injection systems would be able to confirm that..

 

[d22dave]

The cooler the air is the denser it is, so a bit better bang. But I wouldn't think you would really notice a difference, but you where obviously pulling a big load. Also the higher the altitude on hills the thinner the air = less dense. That's my theory for the day

 

[Rumpig]

Yeah, the hotter it gets the less fuel it gives. They measure air temp, coolant temp and fuel temp for a reason. For something like 5 degrees rise in air temp you lose 1% in horsepower.

 

[camo.b]

Mine is a totally diffrent car at 10° amazing.. then 30 its fine but pushing 40° its a slug.like d22dave said its all about the denseity of the air and at 38°your just not getting enough cool and oxygen rich air

 

[matt_91]

Thanks all. I'm aware of changes in air density, I guess I just wouldn't have expected it too make such a noticeable difference. After 3200km with that thing on the back and taking it off yesterday afternoon I'd forgotten how quick this thing can be!

 

[Old.Tony]

I've found my car is quite sensitive to heat, although she's pulled 1.8T at 130km/h in 45C heat!

Hot air is less dense and hot air impedes the efficiency of the intercooler (which makes the problem worse).