Renix Air Intake explained

[steph74]

So as usual, you explain, I learn ;)

My question is more on the benefit of cold air intake. From what I understand, there is an added HP or TQ gain when feeding cold air to the engine.
OK maybe....

So reading more on the airbox I have on my renix, I don;t understand why it has a preheater hose, a heating coil on the manifold and a gate in the intake horn that is closed when the air is less than 13 degre C to allo the optimum temperature for the air to get into the engine.
That sound to me that at some point the engeeners thought that cold air was not so good....


So why is that ? is it only an emission issue, is it to control gas consumption low ? I don't get it...

(the reason I am looking at this is 1/ my preheater hose is ripped and I am wondering if I need to change it again... 2/the system seem not to work and before I start digging to know if it is the temperature sensor or the vacuum activated motor that are faulty, I want to know if it is worth it)



comments and advices welcome ;)

[4.3LXJ]

You are right Steph, cold air does work better. But only up to a point. An issue we have is that the 4.0 is a single nozzle injector motor. At really low temps, you will not get good enough mixing for ............................ you got it, emissions purposes.

[steph74]

So considering that i live in a state were cold is normal, i am better off keeping it that way....
In addition toallow better emission, does it effect gas consumption ? My guess is yes .....

[4.3LXJ]

Probably only until the engine is good and warm

[steph74]

Mmmm so probably not much effect then...

[jeepxj95]

ive alway wondered that samething. my 90 does but the 95 dont

[steph74]

Renix vs HO i am not surprised ....

[LizardRunner]

physics sorta kicks in on the cold air induction theory. What they think is that cold air is denser (very true) so you can pack in more air. The problem with that is, the best burn rate is when you have finely atomized fuel mixed into the air. This is best accomplished with hotter air (physics of vapors is in play). If you want the most power (and there for effenciency) you need the air flow to be able to hold the most fuel vapor, that means warmer air because warmer air holds more vapor than colder air. Cold air causes bigger droplets of fuel, which burn far slower if at all than fully vaporized fuel.

Smokey Yunick built a Fiero GT induction system that allowed the V-6 to get almost 52 mpg, in an era where 20-25 mpg was awesome mileage. He did it with hot air induction using exaust gasses to preheat the intake rails. He also used the radiator to pre-heat the manifold/carberator junction and a turbo to inject the fuel/air mix into the cylinders. By using hot air induction, he got better gas mileage along with almost 40% more horsepower (0 to 60 in under 6 seconds). here's a drawing of the system.
http://farm4.static.flickr.com/3190/2738903116_71abf7785c.jpg

[4.3LXJ]

Chip, that looks a lot like early turbo/carb systems. That is a turbo on there right?

[steph74]

:popcorn:

I feel like I am going to learn something today ;)

I like this forum for the "educated" answers we sometimes get to our simple questions... you just have to ignore the green jeep gang that still have not brought "educated" proofs to what they claim... but that is nother story :boohoo::boohoo: .

(and by educated I mean also a civil discussion...)

[BlueXJ]

Timing also is varied by the computer to match the signal from the MAP sensor. This varies with the temp of the incoming air. Warmer air is what the engine sees and is what the ECU is designed for but the colder temp air is slightly heated to alter the timing when the air is very cold. HTH

[4.3LXJ]

Thanks Steph. I drive a blue Jeep. So I am smarter :D

What Chip said is right. And I remember those builds. Smokey was not the only one to do this kind of thing. Buick used a one barrel carb on an aluminum 215Cu V8. They had rotten luck with seals on the Air Research turbos and Banks had some too. But there is a limit to how much heat you can use. At that limit, you loose energy out of the combustion process itself. I think it has to do with the electron orbits and how the atoms vibrate if I remember correctly. So back to your original question, yes warm air within reason is better for atomization, but you don't want it too hot because you make the combustion process inefficient. That is why they put intercoolers on turbos that run more than half an atmosphere boost.

[steph74]

OK so I was under the impression though that the Renix engine air intake was different than the HO one. From what I read it seems more complicated than just a air filter and a tube ;)

Anybody can confirm that ?

I like the idea of keeping that old girl's engine running good with minimum mods to the engine so i am cool with that. I already confirmed that the little gate closes with the vacuum applied and I just need to find the time to look into the temperature sensor and other components....


Chips the explanation makes total sense to me as well...gas economy vs power.... difficult to have both I guess (difficult, but not impossible ;) )

Blue the MAP sensor is important I knew that lol (always forget about it though ;)) especially when you live at higher elevation so that too makes sense.

[LizardRunner]

Chip, that looks a lot like early turbo/carb systems. That is a turbo on there right?

Yes it is a turbo that has been modified and it has a pressure limiter to keep the "boost" to 15 psi. The "turbo" modified becomes more of a "homoginiser", the idea being to create a homogenous mix of air and fuel. The "optimal" temp range for the preheated fuel/air is 400 to 415 degrees f. On the fiero, smokey was running an internal temp of 2600 deg f. That is the great mystery he took to the grave, how to get above the disasterous 2250 deg f where spontanious detonation occurs. Part of that magic is the reprofiled cam lobes. Now Smokey used 15 psi in his "stock" engine but it was not stock, it had carrillo rods, forged pistons, ceramic coated zero gap rings and that special grind cam. I am working on something we can just bolt onto a genuine stock 4.0 I am getting closer.