MB-BOB

There has been discussion on this forum occassionally about the sensitivity of the 2.3L and 1.8L engines to changes in Ambient temperature and relative humidity. Has anyone done a hp dyno under optimal weather conditions, followed by one on a hot, humid day, to compare the drop in HP?

ctC230K

not I

Outland

No, but I would expect the heat to reduce the supercharged engine output by about 10% on a hot day. Still faster than a C240, but noticeably subdued.

nukblazi

If you go do four runs in a row you see the same thing. The first run is the highest output, and the numbers decrease with each subsequent run.

It's not the 1.8 and 2.3 I4 motors. It is a property, or attribute of a air-to-air intercooled forced induction car and is well documented and explained on net.

ctC230K

I DO notice a change in power with the Air Con running and a very slight change with the heater fan running. And then you know if the windows are down it's slower cause of bad aerodynamics.

FrankW

hot and humid weather will affect all supercharged or turboed cars.

the C32 also suffers heat soak during hot weather.

MB-BOB

Well understood... not an MB problem. Just wondering if anyone here understands this. I'm not against modding at all. But if it were me, I would want to be sure that after spending $20K on 3hp here, 7hp there, that the enhancements were not more that offset by the whims of the weather.

So... the normally aspirated C240 keeps its 165 HP and torque, while on a hot day a 10% hit on the I4s drops the output from 189-192 to 170-173 (comparing advertised hp, not rwhp). I'm not sure the butt-dyno can tell the diff in 5-7hp.

tommy

But the 240 is a heavier engine, right? That would affect things too. Then, of course, you can't swap out a pulley on the 240 to make more acceptable hp. If you're doing a comparison, choosing the car with more hp AND more tunability seems like a no-brainer. Unless it's for a trouble-prone daughter, when less hp would be an advantage. You'd have to be JLo to have a butt dyno that doesn't feel a 5-7hp difference, no?

Of course, being in a blue state, I don't have to worry about hot temps most of the year, so your main point is n/a. Who would be idiotic enough to live where that's a concern?

mctwin2kman

In any forced induction engine the hotter the intake charge the less power produced. Also the more humid the weather the more power porduced due to the humid air be more dense! Now remember the intercooler will only truly heat soak when you are stopped or moving slowly. Once the car is in motion at a decent speed the IC will cool back off pretty quickly. So full power will be restored. Look at the Lancer Evo and the WRX STi, they have intercooler water sprayers from the factory. You can manually squirt the IC to cool it down before you launch for max power. Of course the higher the boost the more heat soaking affects the power. I have never really noticed a drop in power even on 90+ degree days in the two years of ownership. But I do not launch off the line, I take off slowly then punch it to save tires and clutch!

ctC230K

right, the c240 is heavier AND the engine also makes less power

1Lop2K5C

question, does the stock intercooler setup between the 03-04 vs 05 improved the heat soak situation ? or do they all have the same setup with the M111 and M271.

delbomber

Not trying to be a stickler, but...

I know it is counterintuitive, but humidity and air density are inversely related. Humid air is LESS dense than dry air.

Cheers.

nlpamg

I love how this turned into a C240 bashing session... I have no qualms, carry on!

mctwin2kman

Then it compress's better! I recall somewhere that cold humid air is the best as it will compress better and more efficiently or something!

Not sure now. Been a while since Physics class!

ctC230K

:p

delbomber

Hmm, but humid air also has less O2 to feed the explosion. Oh well, not much anyone can do about it anyway!!

jwithaCLK

All engines will see a reduction in power of 1% for every 10 degrees increase in ambient temp. Whether it's a Civic or an SLR McClaren. 10% means one day is 100 degrees hotter than the other.

Jim Banville

Then what's the point of water injection?

ctC230K

you mean spraying water on the intercooler? it makes it colder....

MB-BOB

Ah yes. I can always rely on my buddy from the "Garden State" (where there are no gardens) to throw out the non stop zingers. According to last years topsy turvy weather charts, last Summer it was hotter in "Joisey" than in Dallas...

Sure the 240 is a bit heavier, but those meaty C7 tires on +2 rims not only provide more unsprung weight, but also more rolling resistance in the I4 cars... wouldn't that make up some of the weight differential? We can discuss the finer points all day. Point was you can always rely on the HP produced by the 240, while it's pretty much a crap shoot depending on the weather sitting behind the supercharged engines.

My troubleprone daughter hasn't totalled a car in 3 years now (fingers crossed). And JLo can sit her butt dyno on my lap anyday. I could imitate the I4 "tractor" hum for her.

Saprissa

That's gotta hurt !!

unless you're into that kinda thing

Outland

No, the C240 loses power as well.

ALL ENGINES loose power on a Hot day. Cooler air is denser than warmer air. Cooler air therefore contains more oxygen, more oxygen means more power. Now, if its hot outside, that slug C240 looses some of its precious little HP sucking in hot air.

On the supercharged engines, or turbos for that matter, the 'kompressor' sqeezes the air, and compressing air causes it to heat. We all know this from high school science class. Typically, forced induction engines will have an "intercooler" that removes the heat, well some of it, from the boosted air stream. The hotter the ambient air, the hotter the boosted air. The same goes for the intercooler. Hot days make it less effective.

Your logic escapes me on selecting cars - you would rather drive a car that is really slow all the time, instead of driving a car that slows down a little on really warm days?

Outland

Water Injection is for ANY engine, not forced induction only. Its used to prevent detonation, or at least reduce the risk of it.

Outland

Not true.

nukblazi

deja vu???