TrueStreet

*sigh* I think you're getting worked up too quickly. I didn't say the same amount of molecules. I said pressurized air, as in same volume more molecules than none pressurized air same volume less molecules. I mean the air coming from a turbo is going to be much much hotter than probably the air temps in the engine bay from the short ram, but my point is that when you're compressing the air you're packing more molecules per volume, then if you were just using the engines vacuum. That's usually the whole point of a turbo, forcing more air into the engine to have more oxygen to mix with the fuel. If you're just sucking up hot air in the engine bay I don't see how it's helping.

I only bring this up because
1) you sited an engine that has a compressor on it and
2) Manufacturers usually try to funnel cold air into the intake. If hot air was the best they'd just have the intake hooked up over a shroud over the exhaust manifold like they used to do when starting up a cold engine back in the 70's.

lobuxracer

iTrader: (2)

If the turbo's out of its efficiency island, then its really not pushing more molecules through the system. It's just creating more heat which appears to be more pressure. I've seen it lots with OEM twins on MkIV Supras.

The reason for the Thermactor valves on carbureted engines was to improve fuel atomization on cold engines as quickly as possible, especially when catalytic converters were new and pouring liquid fuel into them caused fires.

Hot air is better under certain conditions. Cold air is better under certain conditions. Neither is universally ideal.

TrueStreet

I think I can agree to that.

06isDriver

AMEN TO THAT!!!

Now will you let me test and design my intake for MAXIMUM POWER at WOT without being Debbie Downer? I'd like to be able to show my results without fear of an intellecutal shakedown.

TrueStreet

why not test it? I mean there may be something else you find while testing, no one should stop you.

06isDriver

Just finished some tests for a k&n style heat shield, so I'll post all the results combined now.

Stock intake: 6 degrees warmer than ambient temps at 60 MPH constant velocity for 10 mins. Hit 97 degrees in simulated traffic stop (idle for 3 minutes) at ambient air temp of 67 degrees F.

Short Ram (no heat shield): 27 degrees warmer than ambient temps at 60 mph constant velocity for 10 mins. Hit 132 degrees in simulated traffic stop (idle for 3 minutes) at ambient air temp of 52 degrees F.

Short Ram (heat shield): 12 degrees warmer than ambient temps at 60 mph constant velocity for 10 mins. Hit 121 degrees in simulated traffic stop (idle for 3 minutes) at ambient air temp of 73 degrees F.

So the data shows that a heat shield will give you SOME benefit but only really while moving. I used a k&n heat shield fitted to the same intake as before. I'll be designing my own now with these dismal numbers.

TrueStreet

nice work.

lobuxracer

iTrader: (2)

Did your data logging allow you to see how quickly each of the setups dropped temperature once the car got moving? It would be interesting to know if, despite being hot at idle, the system lost heat quickly once it got moving.

06isDriver

I dont have any hard rates on temperature drop but I did notice that after the "heat soak" test, the time necessary to drop the intake temp by 1 degree took progressively longer in relation to how hot the temp was at end of heat soak.

lobuxracer

iTrader: (2)

OK, so here's what I'm thinking - hot air at idle makes the engine run more efficiently, cold air at WOT makes more power. If it runs hot at idle, it's not really bad if you can get the temperature to drop quickly once you start moving, so a solution offering both would be ideal.

Infra

iTrader: (1)

Oh man... I'm not trying to pick on you here, but if we're going to start talking about thermodynamics, PLEASE PLEASE use correct terminology. ie, don't confuse temperature with heat!!!

This is not an endothermic effect... it's a pressure drop across a choke (throttle body) that causes the drop in temperature (not heat). Endothermic processes take heat from a system and store it in chemical bonds.

Heat is a measure of entropy, or in other terms, energy.
Temperature is a measure of the average kinetic energy of a given volume's molecules. Heat can not be lost in a closed system.

What TrueStreet said is technically correct, any gas at the same temperature but greater pressure has a greater number of molecules.

Pressure is the force those molecules exert, and as such, is a function of temperature and volume (ideal gas law, PV=nRT where n is the number of molecules and R is a constant).

So, if V, R, and T do not change, then n must increase for P to increase.

lobuxracer

iTrader: (2)

Point taken on the heat and temperature. You're right, I was not being critical.

I had the PVnrT discussion with my Chief Scientist when I ran a gas analysis lab. His argument is it's not possible to keep P or T constant in the real world. If there's a temperature change, there's a pressure change by the very nature of the relationship.

In an engine with forced induction, temperature and pressure both rise when energy is added to the gas by the compressor. Which rises more depends on the efficiency of the pump. This is why compressors are mapped. We need to know where the most efficient range of operation exists and to allow the tuner to take advantage of the compressor's characteristics.

I've seen small turbos produce what appeared to be a lot of pressure, but because they were operating well outside of their efficiency island, they didn't make a lot of power. A larger turbo and the same measured pressure made a lot more power because it's moving more air (your argument about n) and because it's not being heated nearly as much (the energy from the compressor is creating more motion - pressure - than adding heat to the molecules - temperature - because it's in the efficient part of its operation.) So pressurized air doesn't necessarily equate to a larger n. It can, but it can also just be temperature driving the pressure reading, which is why I said pressure by itself doesn't mean anything. You need to know three pieces of PVnrT to know whether there really is more oxygen or not. Luckily, an engine doesn't often vary the volume until we get to the cylinder, so we can say knowing pressure and temperature will get us to n. Which goes all the way back to where are you measuring pressure and are you measuring temperature with pressure? Measuring it at the discharge of the compressor will tell us a lot about the compressor; measuring it at the manifold will tell us a lot about the intake and any heat exchangers in the path. Both will tell us about n so we can figure out mass-flow which is what counts.

06isDriver

I was thinking of designing it so that it would either be hot or cold air depending on if you wanted mpg or more power, but I'm just trying to get it done now.

Theres always room for Version 2...or is it 3,4,5? I dunno, prototyping is a bia.

TrueStreet

should just do it like the old cars then with a shroud over the exhaust that pipes to a butterfly valve into the intake that maybe works like a reverse throttle so that when you press on the throttle the other other valve closes and when you let off it opens.

Infra

iTrader: (1)

I believe the effect you are describing is that the smaller turbo is performing more work on the air, thereby raising it's heat value, rather than compressing it. I can imagine this would happen if the small turbo was spinning too fast to effectively take in enough air, thereby creating more turbulence than compression, leading to an increase in heat in the air. This would cause an increase pressure due to an increase in temperature.

Converse, the larger turbo is effectively compressing the air, and not performing work on it... so you see a rise in temperature due to the increase in pressure.

You'll have to do extensive testing to see any difference with such a small change in intake temperature... and noise in the data would probably hide any real effect.

Also, I believe that when dealing with such low intake temperatures (nothing like Smokey's 700° F) the ECU will probably adjust the volume of air taken in during the intake stroke via VVT-i to reach an ideal value. Your attempt to vary the intake temperature might not have any effect at all at idle due to the generous amount of room the ECU has to work with in terms of actual vs maximum air and fuel volumes. At WOT, when the ideal air temperature is as close to ambient as possible, would only be reached with a heat shield... and unlikely to outperform the stock airbox.