School Me: WAI vs CAI

[Joeggernaut]

Stoich, is a ratio of fuel to oxygen that will allow fuel to ignite; now when it comes to modern engine controls; it depends on engine coolent temp, intake temp, map/maf, tps and o2.


Partially correct: It is ratio of fuel to air. Air consists of oxygen yes, but also carbon and hydrogen. Air is not the same as pure oxygen. Read about open and closed loop for how an engine matches stoich or whatever AFR ratio it is targeting.


most cold air intakes do not go down past the engine(because lower means water getting sucked up/hydrolocking/getting sued). "cold air" is subjective.

Wrong: Actually they do, people put sleeves over them to prevent hydrolock. You might be thinking of a SRI short ram intake which is different from a CAI.



most engines from the 80 and earlier had some variation of this, to help with cold start issues(too much oxygen to fuel). Still questioning why they got away from thermac's for fuel injection.

True


the only maf i've seen that interferes with airflow is the spoon type that ford used in the late 80's/early 90's

MAF systems use the same sensors to calculate air flow as the map does, just uses a different way to determine fuel; it's also an indirect method.



Wrong: All maf sensors are in direct line of air flow and do cause interference. The air has to move through and around the maf sensor inside the air intake. There is a slight decrease in efficiency because of this but is more accurate for the ECU as real-time data is calculated instead of in direct like a map setup. A Map sensor measures manifold air pressure and not air flow. They are two different setups but do share some of the same sensors but they are different.



nope, the camshaft profile is when it open's and how long it stays open per cycle.
LIFT is how far the valve opens and closes

Wrong: camshaft profile controls how far the valve opens and closes, same thing as lift, not duration. It only hits the lobe once, for it to stay on the lobe the camshaft must be advance or retard which is what camshaft phasing is.


Camshaft phasing is the change of camshaft timing in relation to it's static position; does not change duration


Wrong: What do you think camshaft phasing does then? You just said it yourself it changes timing which is the definition of duration. You are getting your definitions confused between phasing and profile.


might want to read this

AutoZine Technical School

Cool article, but I already knew what it does/is. It might be helpful to other readers who want to see visuals.


nope; duration doesn't change, phasing a cam changes when it opens and closes(eg crankshaft rotates 720 for every 360 of the camshaft; phasing means a camshaft the opens at 208 normally would move 10 or more degrees +/- so 208 could end up phased at 198 or 218 depending on the computer)

Wrong: Once again you are contradicting yourself by saying duration doesn't change. Phasing a cam means the cam is able to maintain that lobe profile longer or shorter which is the definition of duration/timing.


Do you have any input/idea off a WAI on new techonlogies as the thread was intended?

[baldlobo]

air defined

Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases

love to know where the hydrogen is?

sri is a version of a "cold air" intake; and is what is most commonly refered to as a cold air intake; when in actuallity it sucks in ambient engine compartment air like the factory one.

Wrong: camshaft profile controls how far the valve opens and closes, same thing as lift, not duration. It only hits the lobe once, for it to stay on the lobe the camshaft must be advance or retard which is what camshaft phasing is.

i could be "wrong" here but i and everyone else defines "profile" as the curve that extends outward from the base circle, but in order to do that it controls more then just lift.
it also controls when it opens and closes which is duration.

where as cam phasing it the changing of when it happens in a 360 degrees of turn of the camshaft. case in point my previous example.

besides if "a follower" were to hit a cam it would bounce, not ride on it


ps. you already knew that yet you said it was cam-less; quite to the conterairy it has a cam it changes valve lift, not the "profile" as you like to call it

pss. we can continue this if you like; i think you don't know your definitions.

[Joeggernaut]

love to know where the hydrogen is?

It is called water vapor and it is always present in the atmosphere. The meteorologist like to call it "humidity". H2O.


sri is a version of a "cold air" intake; and is what is most commonly refered to as a cold air intake; when in actuallity it sucks in ambient engine compartment air like the factory one.

Exactly glad we agree on something. It is often easy to add dryer duct work to a SRI to get the effect of a wai



i could be "wrong" here but i and everyone else defines "profile" as the curve that extends outward from the base circle, but in order to do that it controls more then just lift.
it also controls when it opens and closes which is duration.


where as cam phasing it the changing of when it happens in a 360 degrees of turn of the camshaft. case in point my previous example.

We are just getting hung up on the details. It doesn't have anything to do with this thread. This is correct in what I/you were trying to explain.



Anyways I feel a wai intake advantage of throttle losses is negated with new valvetronic/valvematic/vel systems. A CAI is now more beneficial in terms of efficiency and power but only on these types of applications.

[Daox]

Its really going to differ from engine to engine. I suggest testing a few different intake configurations to see what really works for your engine.

[serialk11r]

If the engine comes from the factory with a low threshold for detonation (i.e. high compression ratio in most cases) then you should really think twice about WAI. Not only is there a possible large drop in performance, but your efficiency could go down.

Higher intake temperature = higher charge temperature. While this helps the flame speed, it also reduces the heat ratio of the charge and thus reduces the power extracted on the expansion stroke (as a proportion). It also puts more stress on the various engine components from higher pressure, aka more friction.

WAI is a very crude method of improving fuel economy, as it exploits a fundamental "design flaw" of most engines in a way that has negative effects on some aspects of efficiency.

With Valvetronic/etc. WAI is probably a bad idea because down to maybe 40% VE those engines should be running more efficient at less VE, and especially if they have high compression ratio such as the Nissan VQ37VHR engines.

[ChazInMT]

Originally Posted by Joeggernaut

With infinite cam profiles the cam profile is optimized to virtually eliminate pumping losses. Since it is 99% optimized the need for a wai is basically negated besides the slight minimal increase in flame speed (DI helps with this more). A cai though is still beneficial. Thoughts on this?

Uh, ya lost me here.

I was under the impression that we had a throttle body which limited the amount air which would be let into the intake manifold, thus, a manifold vacuum, the amount of energy required to pull the air past the throttle plate is where the loss occurred. It takes power to draw in the air, the power comes from the engines, thus a loss. You can't tell me it is an effortless process to draw air across the throttle plate.

Your love affair with valve management systems is misplaced in my estimation, you have seriously confused 2 different processes going on in the engine.

Also, you claim hydrogen is present in the air due to the humidity that is "Always there". Here in the north, when temps drop low to freezing, there is very little to no water vapor in the air, at its most it's 4% with 2% being common on warm summer days most places. Understand however, this vapor does NOT contribute elemental hydrogen to the combustion equation since it is already attached to oxygen thus being water. It will be a factor on a small scale in its ability to remove heat & such, but the effect is tiny, and unless you're running a top fuel dragster, really isn't worth discussing.

Anyone else wanna talk these points through?

[Joeggernaut]

Originally Posted by ChazInMT

Uh, ya lost me here.

I was under the impression that we had a throttle body which limited the amount air which would be let into the intake manifold, thus, a manifold vacuum, the amount of energy required to pull the air past the throttle plate is where the loss occurred. It takes power to draw in the air, the power comes from the engines, thus a loss. You can't tell me it is an effortless process to draw air across the throttle plate.

Your love affair with valve management systems is misplaced in my estimation, you have seriously confused 2 different processes going on in the engine.

Also, you claim hydrogen is present in the air due to the humidity that is "Always there". Here in the north, when temps drop low to freezing, there is very little to no water vapor in the air, at its most it's 4% with 2% being common on warm summer days most places. Understand however, this vapor does NOT contribute elemental hydrogen to the combustion equation since it is already attached to oxygen thus being water. It will be a factor on a small scale in its ability to remove heat & such, but the effect is tiny, and unless you're running a top fuel dragster, really isn't worth discussing.

Anyone else wanna talk these points through?

Older cars do have a throttle plate but these cars with these new infinite variable valve technologies are able to omit the throttle plate completely. Now when a driver pushes the accelerator the ECU tells the valves what to do and controls air flow this way. The air flow is control actually by the engine valves and not a throttle plate (talk about no control over engine input, the ECU is doing everything these days for the driver). There is no longer the restriction of a throttle plate which accounts for almost all of the throttle losses in a typical engine due to back pressure.

So maybe you are thinking there is still some throttle loss due to valves being closed when air is trying to enter the engine, but the ECU can time the valves precisely to open at the exact moment to minimize this effect. There might be a 1-2% of blockage which is why I say it is 99% efficient in eliminating throttle losses. Toyota seems to have the best design in terms of simplicity and weight of the system.

Here is a direct quote from an article someone posted, you can find this same information on other sites also:
"Moreover, car makers can make use of CVVL to regulate engine output, thus eliminate the need of throttle butterfly and reduce so called “pumping loss”"


You are correct about humidity but there is a small factor involved but not worth really mentioning on passenger cars but he asked so I provided.

[ChazInMT]

So I was under the impression you were stating that a lot of cars driving on the road now all have CVVL systems in place which eliminate the throttle. This I contend is not quite the case, but it may not be long in coming.

I have to admit, I had a whole paragraph written up which was going to blast this whole CVVL as dreamland non-sense. Then, to make sure there wasn't really something to it, I Googled it. OK, I was really ignorant regarding these valve control methods. I have a VTEC Honda that I knew did some flibbity flu thing with the valves, but had no idea other car companies had gotten so far ahead.

I have revised the previous paragraph needless to say, since I'da looked quite troggish posting it.

OK, so I've read through some articles (find below) and educated myself on CVVL. I see it is mentioned that there is potential to eliminate the throttle, but, I don't see where anyone has done so completely yet.

I think that car makers want to get a few gazzilion miles under their belts running a CVVL with conventional throttle before they jump in whole hog on letting the CVVL thing take the entire load. I see BMW has a throttle for start up and backup to a Valvetronic failure (limp home), but does indeed open the throttle fully when the engine operates normally.

The main take away I'm getting from all this is that by closing the inlet valve before the piston reaches BDC (er... Bottom Dead Center) you can control the "charge" that way and thus eliminate pumping loss. It appears a small amount of "loss" is good in that it creates a healthy swirl to promote better combustion which off sets the loss and then some.

Interesting stuff, here, here, here, and here.
Notice - the red "here" is a big file if you have slow internet.

Thanks for bringing all this up. I learned a lot. It's one of the things I love about this Ecomodder family, it really gives us the opportunity to explore all things automotive keeping our minds sharp and growing.

[LeanBurn]

SRI = short ram intake. Sometimes set up like a warm air intake. Its not a cold air intake at all but intakes air usually from directly beside the engine the shortest path. Not sure where the "RAM" part comes into play, probably more marketing than anything else. I have tested these and temperature variations fluctuate wildly as at rest it sucks up hot air radiating from the engine and radiator, then as one gets to speed it begins to fall.

CAI = cold air intake...obviously already covered. The object is not to intake air from air supply down lower than the engine, or any other altitude relation to the engine. It is intended to draw air temps as close to ambient air found outside the engine bay as possible. Often this means putting the intake end as far away from the engine as possible and where a filter will fit if an entire replacement set up is used. Consequently this often means putting the intake opening/filter behind the front bumper under the headlamp. temperature variations are minimal nearly constant as far as the intake tube/tract is heated by surrounding air. CAI Hydro-lock concerns are only realized when idiots roll through water that is deep enough to immerse the intake filter element and it sucks it up like a straw. For the rest of those that avoid water that is 12 inches deep or more as pure common sense, it is never an issue.

Interesting to know that there are quite a few CAI from factory, My 1997 Suburban has one, there are even some ram cold air intakes (which puts the cold air intake directly in the airflow like those found on the new Insight.

Some cars it makes little to no difference with regards to fuel economy whether CAI or WAI (SRI). There is some difference in power in some engines...which has been covered.

[Joeggernaut]

Originally Posted by ChazInMT

So I was under the impression you were stating that a lot of cars driving on the road now all have CVVL systems in place which eliminate the throttle. This I contend is not quite the case, but it may not be long in coming.

I have to admit, I had a whole paragraph written up which was going to blast this whole CVVL as dreamland non-sense. Then, to make sure there wasn't really something to it, I Googled it. OK, I was really ignorant regarding these valve control methods. I have a VTEC Honda that I knew did some flibbity flu thing with the valves, but had no idea other car companies had gotten so far ahead.

I have revised the previous paragraph needless to say, since I'da looked quite troggish posting it.

OK, so I've read through some articles (find below) and educated myself on CVVL. I see it is mentioned that there is potential to eliminate the throttle, but, I don't see where anyone has done so completely yet.

I think that car makers want to get a few gazzilion miles under their belts running a CVVL with conventional throttle before they jump in whole hog on letting the CVVL thing take the entire load. I see BMW has a throttle for start up and backup to a Valvetronic failure (limp home), but does indeed open the throttle fully when the engine operates normally.

The main take away I'm getting from all this is that by closing the inlet valve before the piston reaches BDC (er... Bottom Dead Center) you can control the "charge" that way and thus eliminate pumping loss. It appears a small amount of "loss" is good in that it creates a healthy swirl to promote better combustion which off sets the loss and then some.

Interesting stuff, here, here, here, and here.
Notice - the red "here" is a big file if you have slow internet.

Thanks for bringing all this up. I learned a lot. It's one of the things I love about this Ecomodder family, it really gives us the opportunity to explore all things automotive keeping our minds sharp and growing.

Thank for you for the added information and insight. My main purpose of this thread was to provide some education but also to spark ideas or new theories on how new intake designs differ in terms of efficiency on new technologies. I already know how wai/cai/sri work on regular old MFI but I was curious how they work on these new valvetrains and intake systems and if their affect still holds true.

My personal opinion is that WAI is no longer an mpg booster since the main reason it increased efficiency was that it was "tricking" the ecu to open the throttle plate more but now that throttle plates are a secondary/backup systems wai only has negative effects now. CAI and SRI are still effective keeping in mind same size and length of intake tubes whether if it is a sri, cai, or wai.

Just for clarifcation when I say WAI I mean HAI as some kind of duct/piping that is drawing in warm/hot temps from the engine bay into the air intake. I think of a SRI is just a short length tube with a filter and that is all. A wai is a sri or cai + tubing to the exhaust hot/warm air.