There have been a few posts lately regarding how air temperature affects performance.

I read somewher once (stuffed if I can remember where) about the direct correlation between air temp and power ie if an engine produces 100Kw at an air temp 30 degrees it will output morekW at 20 degrees.

Does anyone know more about this?

yup because cold air is denser and packs more oxygen content. that's why turbo/superchargers work very badly in hot weather because they are just sucking in hot air and that's no good both in terms of engine temperature and the surplus oxygen that is needed. i believe strongly that the power and torque figures quoted by manufacturers are tested during optimal conditions for the car.

Yeah what gauss said, hot temperatures don't make a big difference to performance on NA cars, not when compared to forced induction cars, be reading guass's post you can figure out why.

Which makes me wonder how booyas car only ran a 15.8 even in hot weather? He does have a claimed 250 horses at the wheels which really makes me wonder how he could only just break 16 sconds :-k . Not saying this to have a go at you booya but it just doesnt make sense, your 250 horsies is from a naturally aspirated engine, temperature isnt going to affect performance that much.

Yeah, I hear what your saying but fuel ie petrol, can only burn as fast as oxygen is supplied to it. As an extreme example of this, petrol will not burn in a vacuum. A fire will burn more intensely if you supply more air/oxygen. Oxygen is the catalyst. Colder air, as you rightly pointed out is denser and provides more oxygen. Therefore if you supply colder air, petrol will combust quicker.

My question should have been "for every degree drop in temperature, what is the corresponding increase in power.


Hmmmm.......my brain hurts

the ralliart magna pulls abt 240 horses at the fly. with a rough 20% loss of power for fwd, that's 192 horses at the front hoops. saying this, i must add that even with the ralliart magna, there is still loads of space for improvement to the engine. with the ralliart variant, i believe the most significant mods would be the more aggressive ecu configuration and revised cams. so it's not totally unbelieveable that booya is pulling signifcantly more than the ralliart but i must say there must be some very aggressive mods, prob to the point that the car is a drag to drive in day-to-day situations.

Booya did run a 15.094, on his last run.

And my NA car always runs better at night in the cold, but I do have a pod filter.

Yeah, I hear what your saying but fuel ie petrol, can only burn as fast as oxygen is supplied to it. As an extreme example of this, petrol will not burn in a vacuum. A fire will burn more intensely if you supply more air/oxygen. Oxygen is the catalyst. Colder air, as you rightly pointed out is denser and provides more oxygen. Therefore if you supply colder air, petrol will combust quicker.

My question should have been "for every degree drop in temperature, what is the corresponding increase in power.


Hmmmm.......my brain hurts

the manufacturers might have the answers you want. but like the guy said, cold air ain't gonna do much for a naturally-aspirated engine. it runs smoother and is bit more responsive, that's abt it.

so like you said. colder intake air = leaner and quicker combustion = more response and better fuel economy

there's not going to be much of a significant power increase, if any (for NA).

So what if you increase the fuel supply and the oxygen density?? ie colder air??

Colder air always gives my car more power.. even with my old Laser. It's pretty easy to spot the difference between 35 degrees and 15 degrees.

Yeah what gauss said, hot temperatures don't make a big difference to performance on NA cars, not when compared to forced induction cars, be reading guass's post you can figure out why.

Which makes me wonder how booyas car only ran a 15.8 even in hot weather? He does have a claimed 250 horses at the wheels which really makes me wonder how he could only just break 16 sconds :-k . Not saying this to have a go at you booya but it just doesnt make sense, your 250 horsies is from a naturally aspirated engine, temperature isnt going to affect performance that much.

the compression ratio of this N/A vehicle in question (which is at 13.1:1) need more cold air then your average turbo! :shock:

the engine needs to pack more (rather than less with a turbo) into the cylinders.

the most evident evidence is a 8degree drop yelded a 1.06 i think faster 1/4 time. slash another 10 degrees, .8second faster ET? then another 10 degrees agian (so its now a 10degree night) and im sure this thing would hammer harder then a mildly worked turbo.

my N/A engine is pretty demanding mate! :lol:

Oxygen is the catalyst.

Actually oxygen is not the catalyst; it is one of the required components for combustion and what comes out of your exhaust is carbon dioxide, carbon monoxide, and water. A catalyst is something that speeds up a chemical reaction but doesn't affect the amount of reactants or products.

I couldn't really think of anything that could act as a catalyst for combustion though...

[quote:08fcd30475="ReallyArt"]Oxygen is the catalyst.

I couldn't really think of anything that could act as a catalyst for combustion though...[/quote:08fcd30475]

You could try aluminium powder or other ones but hey youv'e gotta inject it and then not blow your motor. You are all talking about some very minor changes in power from Cold air.

Talk to a guy who runs a dyno and he wil explain it all to you. eg why does the graphs slope become less then top out? Cause the engine is pumping more fuel than air in - why - to cool it down and make sure that the thing doesn't burn rings - what does this do - reduces overall power and torque but protects the engine - what do I do then - change gear find the optimum rev range for power and stay there.

Why don't you really ask what is the perfect stoiciometric ratio. Even harder to explain but that is what your fuel map is trying to do. But the factory wants to protect its equipment so it gives you a conservative one that can run from -20degC in the blue mountains to +50degC in Booya's home turf. So if you drive in a certain area get your fuel map - mapped to that temp range instantly more power. Just don't push it where it doesn't belong or you'll be pushing it home.

Hmm... Read my other post in Mods to understand why this doesn't make sense.

Here we go again. I guess there is only one method to find the truth: one of us goes to dyno hoping to get large variations in ambient temps and does several runs - but who has the day to spend and the money to fork out to do this? Thought so. So until something more "scientific" like this is done, we can only speculate on this matter. Unless somebody provides a mathematical formula to prove it any which way. But to do so, manufacturer's ECU info would need to be included etc. Again, quite difficult. Not impossible, but difficult. Any volunteers?

Anyway - temp does make a big difference.
Pods sucking hot engine bay air are not good idea - cos they get hot air straight from the radiator. Only if one can provide fresh outside air to a pod, it is worth it.
In turbo, intake air temp gives some 0.5 kW per degree difference in power. NA engines obviously are not that sensitive. Make your own conclusion from that.
On "ass feel" I can say that from 20 to 40 deg temp, cruising around town there is much less power available - I'm guessing some 10-15 kW.
Many other drivers tell the same. But as I said before - let's not write this in to a bible and wait til somebody does such dyno test as I mentioned above and get this thing cleared. Maybe we should do a collection for some of the Melbourne guys - their weather changes 10 times in one day - that would be sufficient research ground.... ;)

Q: In what ways, and how do you increase the compression of your Engine Booya?

Is it through all the mods you've put in, that the compression automatically increases it self or is there something straight forward that you can just adjust to increase your compression? is it to do with timing or A/F ratios? What's a safe compression for un strengthened 6G72?

Compression is upped by either higher compression pistons, stroking, or gaskets which are thinner (I dont like that idea myself). Or a combination of any of these methods.

high compression pistons

booo ya you should slap the new RPW Single turbo on ya car n slamm the massavely powerfull engine with cold air...
You wil have to drive at night tho..
you could call it
gold night blaster...
or night gold blaster

Just for reference, I remember reading in a Wheels magazine review comparing the HSV VY S2 clubbie to the Ford FPV GT. The HSV is rated at 285kW and the FPV at 290kW, but what they pointed out was that HSV and FPV use different "standards" for measuring engine output.

Like, Standard A says you will measure at 20deg with 20% humidity, and Standard B says 25deg with 40% humidity or whatever (I made those up, btw).. the end result was that the HSV's 285kW was actually understated compared to FPV's measurement which explained why the Holden performed better in a straight line.

food for thought.

Just to throw some more into this discussion.

Formula 1 cars (NA 3.0l V10), now I can't remember the figures, but they get far less horsepower out of races in the hot areas than they do from the cold races.

Not sure of the science behind it, but always feel the difference when it is really hot and really cold.

Like I said before...cold air is more dense, which aids combustion.

[hair splitting mode]

It doesn't just aid combustion, in facilitates combustion.

[/hair splitting mode]

Denser air means more oxygen per unit of volume, meaning more of the fuel can burn.

I'm no engineer but I wouldn't be surprised to find that in really hot air you actually have some fuel mixture left over that doesn't get burnt, which would obviously lead to a power reduction.

Any chemists/physicists want to suggest why a denser air mixture, results in higher pressure during compression might lead to a more violent explosion, also?

The same principle applies to a decent set of extractors and a high flowing exhaust system.. the more of the post-combustion mixture you can get out of the cylinders, the more room there is for fresh combustion to occur.

disclaimer: I am not a scientist 8)

be picky...
You know what I meant. :roll:

I'll remember my dictionary next time I post.

like I said, hair splitting mode.. tongue in cheek. carn dude, lighten up :D

Just trying to give more information for people who might not get it.

Soz man..I forgot the :lol: !!!
That was my bad!
:lol:

Cold air will without a doubt enable teh vehicle to produce more horsepower.

Magnas are responsive to this via the air flow meter which not only reads teh volume of air but has a barometric pressure sensor as well as an air tempature sensor which adjusts the fuel curve to compesnate for air tempature.

N/A cars are not as sensitive as turbo cars for tempature but it does make large changes to teh cars driveability.

The hotter teh air - the less oxygen you can burn and the car tends to run richer. This is compensated via the air tempature reading and o2 sensor control which compensates but of course power does drop.

Last thing clarify for me please - what is the average tempature in the NT which is to my understanding mostly desert? If it is running an average tempature higher than ourselves, then I would have thought Booya's car would not have been affected as much in the hotter tempatures at the drags?

my car was tuned in adelaide the day before the drags during the morning/evening when it was around 20degress outside.

my car at home sits in the garage during the day. i dont use my car as a 'daily driver'...
its a night rider :badgrin: :badgrin:

It's not all desert, but it is bloody hot up here most of the time!

At least in Alice the temperature drops off at night. :cry:

Actually I was asking a legitimate question out of curiosity no other reason.

Is it actually like an average of 30 degrees during the day and then 10 degrees at night?

Large variations in tempatures like that do actually create havoc when tuning cars as it is very hard to get the car tuned properly until you have a good go at checking it at all the varied tempatures.

I have to admit most of our hard core tuning is done at night time in Perth usually around 7.00 onwards to get the colder air and tune it for when it requries the maximun amount of fuel.

This is always a better way as it measn that if its hot then the car will only run richer, not leaner if it is dramatically colder than the time of tuning.

Would this do?

http://www.bom.gov.au/climate/averages/tables/cw_015590.shtml




Actually I was asking a legitimate question out of curiosity no other reason.

In Darwin it'd be average 33 odd during the day all year round. At night 20 - 25 in the wet.. 15 - 25 in the morning.. and all round night time of 10 - 15 in the dry. When it rains the temperature plummets and because it's pretty much always hot here, when the temp drops it really FEELS like it's dropped.

It also depends what you mean by Darwin.. cause the real Darwin is say only 10 - 15 Km big.. but people from Darwin can live 75 odd Km out.. and the temperature can vary quite a bit in this distance :)

[quote:98efe0e003]At night 20 - 25 in the wet.. 15 - 25 in the morning..[/quote:98efe0e003]

You live down at Howard Springs or something, don't you? ;)

You'd be lucky to crack 25 at all during the wet season, unless it has rained all night and is overcast in the morning.

The coldest temperature on record in Darwin is about 12.5 deg C at 3am.

eheh.. I was being very general.. probably a bit too much :)

I live in Palmerston.

dont forget the HUMIDITY.........

People say they feel their cars are different on cold days/mornings etc. I notice no real difference any day. On wet days, it is harder to get traction, but that's just the wet road, not more HP from my mini beastie. :roll: