Hey Guys,

So i know most cars will perform worse on hot days. But lately, i've noticed that whenever it's hot i have a serious loss in performance, i can feel how much slower it is as if i'm only on 75% throttle instead of WOT. The difference between when i go to work in the morning when it's cold and in the arvo when it's hot is really shocking. It's like the difference between having an empty car and having 2 people sit in the back.

Is this common to all Magnas, or Ralliarts or is something just up with mine?
Standard intake with the paper filter ATM, if that helps.

All cars do this, air thins out in the heat and the engine loses power, like your engine has shrunk from a 3.5L to a 2L. lol

Especially noticeable on small engines working hard, like a 2L Lancer, cold winter night vs 40 degree day, same trip.

High altitude will do this too, some piston engined planes run superchargers to increase their maximum altitude.

this will explain a bit
http://www.youtube.com/watch?v=Xp-EVOPBhIo

I'm not 100% sure, but the airflow meter in conjunction with the ECU etc should compensate for this to a certain degree by altering timing and air/fuel ratios to suit the hot air which is also probably why the air temperature is monitored by the ECU.
Maybe you have the A/C on in the afternoon when it's hot, but not in the cool morning.

I'm not 100% sure, but the airflow meter in conjunction with the ECU etc should compensate for this to a certain degree by altering timing and air/fuel ratios to suit the hot air which is also probably why the air temperature is monitored by the ECU.
Maybe you have the A/C on in the afternoon when it's hot, but not in the cool morning.

thats exactly what i was thinking. when my aicon is on, it makes a huge difference. the timing shouldnt change. it shouldnt be that much worse. i would be looking into the aircon being on. i cant even notice a diffence in power from one day to the next, let alone that much

What car do you have? Have you had it SKR tuned?
All magna's/verada's have a temp sensor that is de-actervated from factory in the air intake. If you have a SKR tune, he actervates this sensor which allows for better tuning. What it does is retard the timing in hot weather to prevent pinging/pre-detination.
I never really noticed much difference in hot to cold weather other than how hard the a/c compressor works but once you have a tune, and the sensor is engaged then you notice a massive difference. In really hot weather, the car is a lot more sluggish, but in the cold, it runs so much better.

I think you need to burn more oxygen, hot air = less oxygen per cc than cold air, hot humid air has even less.

Living in Qld, we notice it a lot. Especially when we get out and do the Toowoomba run in June, its really cold out their (comparitively), 8 degrees C, 2 years ago, our cars went like stink.

I think you need to burn more oxygen, hot air = less oxygen per cc than cold air, hot humid air has even less.

Living in Qld, we notice it a lot. Especially when we get out and do the Toowoomba run in June, its really cold out their (comparitively), 8 degrees C, 2 years ago, our cars went like stink.

You wouldn't think that would be so - Toowoomba is 592 metres above mean sea level which means the air is at a lower pressure and has less oxygen.....however, seeing as I live in Toowoomba I must agree that the cool air up here does seem to make your car run a bit more sprightly.

What car do you have? Have you had it SKR tuned?
All magna's/verada's have a temp sensor that is de-actervated from factory in the air intake. If you have a SKR tune, he actervates this sensor which allows for better tuning. What it does is retard the timing in hot weather to prevent pinging/pre-detination.
I never really noticed much difference in hot to cold weather other than how hard the a/c compressor works but once you have a tune, and the sensor is engaged then you notice a massive difference. In really hot weather, the car is a lot more sluggish, but in the cold, it runs so much better.

Just to correct a misconception (and being pedantic), the intake air temperature sensor is not deactivated from the factory, as it is used to in conjunction with the output from the MAF to compute the mass of air flowing through the engine.

What is neutralised (not deactivated) is any temperature sensitive ignition timing adjustment. What I've seen in one SKR ROM is timing retard at high intake temperatures (above 38C), used to minimise the risk of knock/detonation from the extra ignition advance applied as part of the tune. While the adjustment could be used to add extra advance at very low temperatures, the sample I have doesn't do this, but better charge density at low temperatures would produce more power anyway.

Another factor in better running at night is the increased humidity along with the lower temperature. I'd have to re-read a couple of books to explain the exact mechanisms though.

Altitude affects engine performance quite significantly. Diesel engine generator sets have to be de-rated for use at higher altitudes (this means that you need an engine with, say, 10% more power to deliver the same electrical output from the generator.

Another effect of altitude is engine pinging. At higher altitudes, you can get away with lower octane fuels because there is less tendency for pre-ignition. Many years ago, I had a Citroen EFI. This was magnificent, but had to run on Super fuel (leaded petrol in those days). Once, I was in an area where I could only get standard grade fuel and it ran fine, despite having 10.5:1 compression ratio. I decided to use standard fuel - until I went down the coast for a day and the engine sounded like a machine gun. Engine performance at sea level is much better, as is for cool or cold air temperatures.

Same effect is noted with gas. Both my vehicles run on LPG and I get much better range from a tankful in Victoria than in Qld, but that could be influenced by the gas supplier as wella s the temperatures.

Aircon is out, i always have it set on Eco between 17.5-20.5, usually 17.5 and i'll just have the fan on 3-5 in warm and 1-3 in cold.

And don't say these things guys, you're giving me even more reason to want to move to Tassie.

With my car (factory ECU afaik) temperature makes no noticeable difference.

If we're talking about a well tuned engine in a Ralliart, could it be that the timing is retarded at high temps as discussed by others, even if it's not an SKR tune?

From my experience with cars, temperature has never made a noticeable impact on power, even when the intake temp was 70 C (heat soak in Sydney traffic) it still drove just fine.
However, altitude certainly has - My N/A cars, driving across the blue mountains, felt gutless, however my 4x4 Diesel Turbo absolutely loved the altitude because the turbo still had to compress the thin air to 12psi, it just had to suck more through the intake to get the same volume.

The thing to remember is that approx an air intake temp change of 3 c = 1hp, so even if it's 20C going to work and 50C coming home, you're only losing 10hp. (all a rule of thumb, long established, but probably not ever scientifically measured.)

So if an extra 30C would only drop 10hp, it sounds to me like other factors are at play.

It couldn't be the engine heat itself, could it?

If we're talking about a well tuned engine in a Ralliart, could it be that the timing is retarded at high temps as discussed by others, even if it's not an SKR tune?

This is quite possible.

Something else I just thought of - as the timing belt nears the end of its life, the stretching of the belt has the effect of retarding camshaft timing. I wasn't aware of any loss of performance with my car until the belt was done, as the deterioration was so gradual; afterwards (until I got used to it) the throttle response was much more sprightly. Have no idea whether this behaviour might have more pronounced effects on a Ralliart.

All belts were done under 10,000kms ago.

If you are having a serious drop in performance could be your coil in your dist, have seen this before, on both Magna's and Falcons, the module gets too hot and starts to drop voltage to the spark plugs