power gain or weight loss?

[Sparkie]

I have a peculiar query to some of the more technical people on here.

it doesnt really apply to C1J engines though.

ok.... how much power (or power to weight) gain do you get from ditching the AC system in a more modern motor.

only reason i ask, is that i reckon you could re-route the clio 172's air intake to suck through the aircon evaporator, meaning that you'd get an intake charge temp of about 5deg (or less if you make the ac spray more refrigerant into the evaporator)

so the 2nd question is this, how much power would you gain from running an inlet charge temp of 5deg, and would it be more than you would get from ditching the ac system power to weight obviously.

i did think that you could adapt a chargecooler to accept the ac hoses.... R134a changes from a liquid to a gas at -26.6 deg you see, so you'd be basically cooling the chargecooler down to very respectable levels??

[Phoenix Autosport]

the problem with that will be that the aircon system will use more energy than you will gain from cooler charge, best bet for power is to turn off the aircon so you arent using that energy and if you measure the charge temp and its too high look at a larger or better positioned intercooler or adding a charge cooler

[Alastair]

Have you thought about freezing a PWR charge cooler up before rnning up the strip with a co2 extinguisher?

[Alastair]

You could also pack your intercooler with dry ice before a run too, provided it vented off away from your intake? Modern air con is worth 2-4 MPG whatever that works out at in Hp? The pumps are usually quite heavy too mate.

[Sparkie]

i was hoping someone might have some bhp figures at differing ambient temperatures for a N/A car and some bhp figures for a turbo car at differing charge temps rather than people just dismiss the idea.

[Matt Cole]

Charge temps should generally be 35 - 40 deg. Something to do with atomisiation at given temperatures and pressures.

[Scoff]

As matt says, you definately wouldn't want 5°C or anything much cooler than 30°C!

Using it to cool charge in a forced induction engine might make more sense ?

[Sparkie]

id heard it was 39deg C.
scoff, thats why i figured, instead of the R134a refrigerant atomising inside the evaporator, you could have it atomising inside the chargecooler, instead of liquid.
on a hot day inside the cabin, ac can get the air down to 5deg fairly easily. i reckon you could get boosted application down well below 10deg.

did i mention i do automotive aircon at work?

[Scoff]

Aparantly best fuel atomisation happens at 40°C but that doesn't mean that the engine stops responding to denser air when it gets cooler still. Rule of thumb seems to be that 30°C is as cool as you'd want to go.

To get to a geniune 30°C (and not a 30° reported by an ebay special thermistor based ACT gauge!!) with a turbo is hard work !

Generally though, since the target is no lower than 30°, people seem to find suitably efficient ways of doing it without pulling power from the crank. (Good intercooling, serious charge cooling, methanol, etc). It would make for an interesting cost effective solution maybe. Is there any examples of people doing it already ?

[Sparkie]

not as far as i know. ...
it just popped into my head one day.
although its got to have been done by some american before i reckon.
if 30deg is minimum optimum then there would be little point i suppose as it would easily surpass that.

[Alastair]

i was hoping someone might have some bhp figures at differing ambient temperatures for a N/A car and some bhp figures for a turbo car at differing charge temps rather than people just dismiss the idea.

Sparkie, you may be able to quantify it by looking at the power rating of some electric air con pumps.
As for power increase i remember reading that a 10 degree drop is worth about 1 hp on a c1j give or take?

[Andrew Cooke]

you can work it as expansion in air, 30deg C will give about 10% expansion, or 10% power gain or loss depending upon which direction you're going.

A mate of mine was running his inlet through his aircon in a saab turbo about 25 years ago, no idea how well it worked for him.

[Rob@Backyardracing]

fwiw, on our datalogs from the outlaw, our runs earlier in the day showed 40c IAT's
and later in the day we got upto 50c IAT's, with no other changes, the car trapped 136mph on both runs. :crap:

[Sparkie]

fwiw, on our datalogs from the outlaw, our runs earlier in the day showed 40c IAT's
and later in the day we got upto 50c IAT's, with no other changes, the car trapped 136mph on both runs. :crap:

i'll get my coat :crap: