Ok can someone please help me understand the Vararam in particular and to a degree all the other intakes?

I understand the logic of cold air vs hot air....no argument there...but what Iam trying to understand is the air volume going into the TB and thus into the engine.....

Doesn't the mass air flow sensor regulate and tell the computer how much air is entering the engine? Doesn't the computer then compensate for too much air vs too little air? I believe basically when your in the limits the computer takes over and does its job and calculates everything from fuel/air ratio plus all ignition and timing. When you go outside the limits the sensor throws a code saying basically something is wrong and that you have too much or too little air.

How does introducing more air into the system get anywhere? The computer just compensates and counters exactly what you have done.

It recalibrates to put you back into the limits?

So I guess unless you retune your pretty much doing nothing? Please someone chime in....Iam no expert and only using what I know.

The colder denser air vs hot thinner air...yes I could see that leading to hp gains....but more air vs less air....don't see it. Not unless you retune the air to let the computer know that your intention is too raise the amount of air and thus then raise the amount of fuel you want and adjust the ignition as well.

 

More air the better. The MAF just reads how much air is passing through and adds more fuel to compinsate for the air to get a good air fuel ratio. The better your engine breathes the better it will run. its kinda like sucking in air through a straw then trying it with a large hose..

 

Colder denser air is more air.

 

remember the fire triangle?

You need a source of fuel (gasolline)
A Heat source ( spark)
Oxygen

Air contains oxygen, the more oxygen that you put through the engine the more fuel it can combust and the more horsepower it can generate.

more air = more HP
colder air= greater density
greater densitiy = more oxygen per given volume= more horsepower

[ up to thermodynamic limits of the engine configuration]

 

The common misconception about an engine is that it is a fuel device. Not true. An engine is an air pump device. It's entire mission is to get air in, and expell it. The better you make the engine breath (both intake and exhaust), the better it will perform. The computer recalibates to adjust A/F mixture for the higher amount of air. Dense air only help the situation.

Think of it this way, the engine has a fixed amount of displacement. It can only "suck" so much air in at a given revolution. Intakes have a resistance to the "sucking".
Take a glass of your favorite beverage and now try "sucking" through both a regular straw and a coffee stirrer type stray. I bet you get more liquid through one.

That's why all heads, valves, headers, etc. are all optimised for maximum airflow. FI systems do the same thing by forcing the air into the engine. It's all about the amount of air you can put in.

 

Yes to a point. Air is limited by the smallest opening, which is normally the intake valve of the heads. Then IIRC the flow of the air, not so much the amount but the speed the air is going into that small intake port.

Speed of the air flow does have an effect. Ram air is a non issue at the slow speeds a car runs at. For a jet engine that is different. Turbulent air flow is more of a problem and slows down air flow speed. ( long calculations from minimal benefits - so almost a non-issue)

In short, any CAI is just about as good as the next, as long as the air is coming from out side the engine bay.

 

The MAF is calibrated for the stock intake, changing how the air flows(pressure, turbulence etc .... ) with a new air intake will change the MAF's response and you will need to recalibrate the MAF(entering a new response curve in the PCM).

 

This seemed to make the most sense out of everything....I mean I understand guys....but without telling the computer more air is coming in, I doubt that it is going to recalculate all its tables and give more horsepower do to a new or different intake. This is really where I was going with it...Heard too many stories on how the cars woke up or performed so much better with a new intake and couldn't really see how...GM's program will run just as that....within the programs boundaries...in other words....

stock programing = stock hp and torque (to a degree...yes you might get a 5 hp difference)
modified programing with mods = changes and thus different horsepower gains.

I mean you might see a slight variance over the stock #'s but if your really looking to get the most out of any mods..the car really should be re-tuned for those mods....people agree?

Makes common logic sense to me.
It would be like putting a high speed processor in a computer with the wrong operating system on it...sure it might run....but won't be matched or optimized.

 

How exactly do you go about calibrating the response curve? Have you calibrated this parameter yourself? What did you use? Aren't the MAF's in the C5 no more than a hot wire anemometer?

 

With tuning software like HP Tuners and a wide band o2 sensor

Log your commanded air fuel ratio against whats coming out your exhaust and use the % error to recalibrate your MAF curve.

 

I see. So in order to really tune for the effects of ram air, you would need to capture the data while driving. Yes?

 

CAI basics:

First you have to understand how heat works. Heat is measured by the movement of molocules in a given volume of a substance. The hotter something is, the more the molocules move around. Oxygen (O2) molocules follow this principle. O2 in colder air doesn't move around as much and thus has a higher concentration per unit volume than hotter air (say from under the hood)

The optimum combustion is based the amount of O2 getting to the engine (fuel is regulated based on the amount if air coming in)

Most Fuel injected GM vehicles have a temp sensor in the intake in addition to the mass airflow sensor to aid in the calculation of how much fuel to inject for optimum combustion.

This being said, while denser air will give you more powerful combustion, it will require more fuel. It's not a significant amount, but it is somthing measurable. This means that underhood intakes with aftermarket filters may use slightly less fuel than true CAIs. Milage however is somthing that is usually unaffected because the more powerful combustion of a CAI means the engine doesn't have to run as hard to move the car along.

More air (aka high volume intakes) aren't nearly as effective as CAIs because unless you're FI, you're engine can only suck in "x" volume of air per intake stroke. The combustion power is determined by the density of the oxygen molocules in that volume. So the "more air "theory just doesn't float with NA engines.

The idea of aftermarket filters is to reduce ther restriction of cheap paper filters. Most flow bench tests I've seen suggest the filter itself is the most restricting part of an intake system. (there's a thread somwhere here that measured all parts of the intake)

 

Ram air isn't as significant as one might think because any ram air effect is neutralized when the air hits the filter. The barametric pressure behind the filter is roughly the same as with any other intake system. In order for ram ir to have a significant effect, you need to be going 150 mph or faster. If the intake arms had a larger cross sectional area, it might be a different story.

 

I can see some where we could have some confusion in this tread. I hope this will help to clear it up. I am not an expert (nor do I play one on TV). The stock computer can sense the amount of air at any given speed and adjust the amount of fuel (and timing) for maximum power (or close to max) or maximum efficiency (like when not under a load while on the interstate on cruise control). I’m not an expert but I do believe the o2 sensors will calibrate the air/fuel ratio so you can make the most of your new found air flow. The computer will also adjust the timing (advance or retard) for maximum power or efficiency. I know there is much more to the computer/fuel/air/timing/wot etc but I am trying to explain what I have learn simply to help you out. We can get into a whole other subject when talking about the computer control stuff).

So more air in - even without a tune = more HP. Some CAI shown gains of 14 to 18 hp and at speeds COULD be more (but not as much as some manufacturers claim). The ls1 engine (from what I have read on this forum) runs rich anyways so you will not lean out the engine with just simple bolt ons (CAI + catback). Most members will agree that is a waste of money to have a tune on a stock ls1 engine with only a CAI and catback. Most agree to wait until your done with all of your engine mods (headers, heads, cam, no cats etc) before you do a tune. Some members (such as myself) have done a CAI, catback, Predator tune with great results (more power - no codes - no knock). I even check the old plugs to make sure it was not running lean (or rich) and I can monitor with the Predator to see other stats)

I would just do the CAI. You will be happy with the results and have a good starting point for future mods.

Hope this helps to clear it up.

 

This is exactly why I only changed my stock filter element and left it at that, (to AIRAID which is a stronger filter than the K&N in my opinion and not prone to collapsing). I was tired of ridiculous horsepower gains stated by various vendors of aftermarket systems.

 

You're on the right track that simply switching to a vararam or other cai will let you feel a difference most likely without a tune and will be closer to optimized once it is tuned.

 

I would have to disagree to a point. The only mod I did was a
haltech stinger cia. I starting getting 0171 and 0174 lean codes.
I got a tune and haven't had them since.

 

A K&N collapsed? More info please....

 

I have to agree....I would love to hear from a GM Tech or FI mechanic on how the C5 works for its fuel injection, computer, and air mechanics....

We have basically two different opions going on:

1. People that believe the C5 with modifying the intake WILL make more horsepower to a measureable degree on its own without any tuning.

and

2. People like myself that believe the C5 with modifying the intake WILL make more horsepower to a measureable degree BUT will require a tune to really optimize the full potential of the mod being done.

I would love to see if anybody has it a run of a stock C5 with nothing more then an intake change and see what resulted from it. Either 1/4 or a dyno pull. Then a similar situation with someone that had the car tuned?

I just would like to know the facts, just like a lot of you guys. I currently have a modified Z06 box and ram air setup....just like the vararam and honestly I don't feel any difference at all. Its more mental I think.

Jeff

 

Here's an amusing kicker: In Houston and other places where it's always hot, for the first few minutes after starting the car, Underhood temps are actually lower than ambiant air temperatre simply because of the shade of the hood.

A single variable dyno pull would be cool, but unless you own or frequent a tuner shop that really likes you, throwing $$ at a dyno pull isn't likely to happen from a private non-bias individual.