WAI vs Ram Air Intake --- at speed...
 

I think that a Ram air intake would be BETTER (even though obviously at outside air temps) than a WAI at speed.

Why? Because the extra pressure would decrease losses in the intake manifold.

Kind of like this,
http://tbn2.google.com/images?q=tbn:...ar%2Bturbo.jpg
and pointing STRAIGHT into the air intake through one of these air filters
http://tbn3.google.com/images?q=tbn:.../BEP-12110.jpg <-pretend its an air filter I couldnt find pictures of closed inline air filters

and STRAIGHT into the throttle valve...


I know, very theoretical to have everything STRAIGHT... but such is the case in my 350z...

??

There are formulas online for figuring the efficacy of ram air.

And this: http://ecomodder.com/forum/showthrea...take-3394.html

And google "autospeed ram air" cuz they've done lots of piddling around with it.

In general, anything that increases the amount of oxygen going through the engine also increases the amount of gas burned since the engine controller adds gas in proportion to the amount of oxygen it detects in the system. WAI reduces the amount of fuel burn by reducing the density of the air entering the engine and reduced air density contains a reduced amount of oxygen in it, producing a FE improving effect identical to that of driving at an higher altitude. A ram air intake increases the air pressure and density of the intake air, acting as a sort of mild super/turbocharger (without the engine load of the latter), and so would increase the fuel burn.

When hypermiling you spend most of your time at low throttle settings where the throttle plate is mostly closed and is by far the biggest intake restriction.
Compared to the throttle plate, other parts of the intake air path contribute little to the intake manifold losses when running at low throttle settings.

Ram air is definitely the way to go for FE. The more air you can stuff into the intake without consuming extra energy, the less work your engine will have to do breath in. Its pretty simple. Also the colder the air the better. Check out all the autospeed articles on the subject. This has been proven over and over again.

EDIT:
I'll cut and paste the articles here from the dead thread for easy access.


HAPPY READING
Eliminating Negative Boost - Part 1
http://www.autospeed.com/cms/A_0629/article.html
Eliminating Negative Boost - Part 2
http://www.autospeed.com/cms/A_0637/article.html
Eliminating Negative Boost - Part 3
http://www.autospeed.com/cms/A_0646/article.html
Eliminating Negative Boost - Part 4
http://www.autospeed.com/cms/A_0652/article.html
Eliminating Negative Boost - Part 5
http://www.autospeed.com/cms/A_0663/article.html

Negative Boost Revisited, Part 1
http://www.autospeed.com/cms/A_107824/article.html
Negative Boost Revisited, Part 2
http://www.autospeed.com/cms/A_107825/article.html
Negative Boost Revisited, Part 3
http://www.autospeed.com/cms/A_107826/article.html
Negative Boost Revisited, Part 4
http://www.autospeed.com/cms/A_107827/article.html
Negative Boost Revisited, Part 5
http://www.autospeed.com/cms/A_107828/article.html

Doing the Impossible
http://www.autospeed.com/A_109877/cms/article.html

Modifying the VL Turbo Intake
http://www.autospeed.com/cms/A_0779/article.html

Into the Intake - Part 1
http://www.autospeed.com/cms/A_1361/article.html

We Have a Record!
http://autospeed.com/cms/article.html?&A=109217[/QUOTE]

Ram Air Project
http://www.karlsnet.com/mopar/ramair.shtml

I sense a contradiction. ???
FE not power.

^I know, because the air is less warm it would be lower FE.

BUT because it lowers the pumping losses it would raise FE (and more than the cold air takes away) yielding a net increase in FE.

?

Now, here's a question:

What if you warmed up a ram air intake? Could you warm up a ram air intake? You get warm dense air with more pressure?

Or is it simpler to just modify the throttle plate?

There are some good points here. I've got some reading to do on autospeed.

That is where I was going with this. IF ram air helps, and WAI helps, then why not both?

Maybe construct a ram air of metal pipe and run the coolant hoses around it to heat it.

Now my question is, how much positive PSI acts on a car's front bumper at 60-65mph? Anybody know?

Ram air is not matter of PSI. The goal is to reduce the pressure loss that happens inside in the intake ahead of the throttle plate due to its geometry to zero. If you wanted warm RAM air you can just setup a very large intake behind the radiator. But you would be wasting your time.

Don't know the answer but I have been tempted to get hold of an airspeed indicator from an airplane or even a magnahelic for live pressure instrumentation while driving. Accounting for airspeed would be a cool part of information gathering.

Here's where a biker did some airspeed vs. psi tests with stock and opened ram air intakes.

Gutted vs. Non-gutted air intake: Test results inside : Honda CBR 600RR Sportbike Forum : 600RR.Net

But these guys are going after increased power, which doesn't automatically equate to increased FE unless all of your driving is pulse and glide.

Geez Louise, ram air and fe? :rolleyes:

THINK about it: for ANY desired power setting and rpm the operator regulates that with the throttle. Say you had 20 psi ahead of the throttle- the operator would simply close the throttle more and the action behind the throttle plate would be THE SAME. Yes, the intake tract, valves, pistons, exhaust... all subject to the SAME vacuum and "work" at less than WOT.

Autospeed claims a bit of improved tip-in throttle response and not a whole lot else. Good on them, that seems sensible.

tjts1
I'm still reading ....but, the biggest flaw I see in your reasoning is this: All of these tests were for pure power gain and positive FE ended up being a residual effect. This means that it isn't actually relevant to FE from this forums perspective. They are getting horrible FE during these tests (relative to this site) because that is not what they were going for and the modification made them less terrible just by coincidence. The evidence you state (in the other dead thread. Sorry for thread jumping) with 3 cars modified shows improvements is also irrelevant because they don't look like economy minded cars in the first place (2 volvos and a BMW). Less horrible mileage is a good thing for a sports car and a heavy car but not good enough for the other end of the spectrum.

(Thread jumping again) You also stated that a car will burn the same amount of fuel at 30K feet. Not true. That is why airliners fly way up there. Less dense air, less fuel used and less resistance in that thin air.
At least consider that the WAI thought supported here has validity. The test results I've seen support it. I'm still open minded though. Got lots more reading to do.

Edit:
After doing more reading I have realized tjts1 has had this argument before and already made up his mind.
I find Franks and basjoos wisdom to be right to the point.

Anything you do to reduce restriction in the intake duct just means that economy could improve when the throttle is wide open. So, if you have the kind of gearing that lets you drive with your foot mashing the gas pedal much of the time, then go for it.

Whats wrong with that? Fuel economy and power aren't always an either or prospect. A lot of modifications you can do to improve power also improve fuel economy. Higher compression ratio, weight reduction, fuel injection etc can all work for FE and HP. I removed the power steering on my bmw and picked up 8hp at 6500rpm and 2mpg at 65mph at the same time. Whats wrong with that? Check out the archive on autospeed. Specifically the Turbo Prius project. Again, fuel economy and peak power can go hand in hand. You just have to be intelligent in the way you approach a problem.
http://autospeed.com/cms/A_2664/article.html
Excuse me? Why do you think I come to this forum in the first place? I put a lot of effort into my bmw 318i to install a taller differential, modern 3rd gen injectors, removed PS, removed mechanical fan, reduced weight, installed a forward facing intake in an effort to improve the drivability, acceleration and fuel economy of my car. The bmw consistently average 30+mpg at every fill up with an all time best of 38mg and I still find time to win autoX events in my class. As for the Volvos, you must have missed this thread.
http://ecomodder.com/forum/showthrea...nder-4093.html
I think you need to make an effort to read more carefully. I said:
Increasing altitude won't magically make the internal combustion engine any more efficient. It'll still take the same amount of fuel and air to make 100hp at sea level as it does at 30k feet. Its the reduced air resistance acting against the body of a moving vehicle that improved fuel economy. So you only need 70hp at 30k vs 100hp at sea level to move the same vehicle at the same speed. Thats where you improve FE comes from. Reduced load.
Yes you're right. I have made up my mind. I worked and experimented on cars for years. I have tested and retested ideas that work (ram air) and don't work (WAI). I keep very close track of my fuel economy and I make every effort to improve the FE of my cars. My latest project is to swap a 5 speed manual into my new automatic Mercedes 190e.
http://img.photobucket.com/albums/v2...g?t=1244858503
The fact that I also enjoy power is another matter. If you think it somehow disqualifies my knowledge or the information on autospeed for that matter, I feel sorry for you.
:thumbup:
Justin

Whoa Dude!!! I guess you showed me.

I should have sought your advice before I bought the Geo Metro. I could be rockin' to work on my daily 100 mile commute in a V8 monster. AND be getting incredible mileage.
What was I thinking.:confused:

At least the owl is alert.

At 60 MPH the gain is about 0.5%.
At 100 MPH the ram air effect is about 0.177 PSI under ideal conditions.

If you want to work it all out for you situation the formula is:
Ad x V squared / 4287
Where: Ad = Atmospheric density. At sea level = 0.076lbs/cu ft.
V = MPH

In practical terms you would need to travelling well in excess of 200 MPH to get 1 psi gain.

Pete.

The issue with WAI. . .is it just forces you to drive more economically.

A Prius can be driven and get mid teen mpg. With its limiter hardware it also tips the driver's habits towards eco friendly driving(fuel economy data, atkinson engine, and so forth).

If you put a rather strong spring on the back of your gas pedal. . .you would get alot better FE too. Not because the spring is magic. . .but because you subconsciously aren't going to push it down as far. . .because its hard and we're lazy(or at least I am ^_^).

Yes the throttle plate is obviously the biggest restriction to most cars most of the time. . . but its alot like running two pumps in series. The first pump is a bit more powerful(the ram scoop) and the second one still turns(because you are still powering it) but its under much lower load. So it requires less effort to turn over the second pump(the cylinders on the intake stroke) if you are pushing the fluid right up to it.

Yes you are likely to lose FE with a ram air intake because you have more available power so at any given depression of the accelerator(gas pedal, right pedal whatever) you are going to use a little more fuel. If you just now got into the car and are very ecominded and self-conscious about it. . .you can get better FE. If you've been driving it. . .well you are used to pushing the pedal down to X to achieve Y speed. Now you push the pedal down X and you achieve Y+Z speed where Z is the extra power to acquired from the slightly larger amount of fuel and air at pedal position X.

Its rather obviously true. If we consider the simplest available system(sort of ^_^) Diesels. . .what do diesels do to get awesome FE. Cram a ton of cold air into the cylinder. . .but they don't usually have throttles. The effect of adding a scoop to a gasser would probably be dwarfed by the effect of adding a scoop to a diesel(if it didn't have a turbo. . .lol).

"The first pump is a bit more powerful(the ram scoop) and the second one still turns(because you are still powering it) but its under much lower load."

nope

alright fine,

[edit] with the throttle plate restricting the flow rates of the what I called "smaller" pump(which is more powerful compared side by side without throttle to the scoop) the ram scoop produces a greater flow[/edit]

That better?

The Ram scoop is flowing more air(at speed) than the engine does after being restricted by the throttle.

?

nope.

ok now i'm repeating myself, but i'll re-phrase to see if that helps:

say you have a 100hp engine. to go at x steady speed requires 14hp. to go at that steady speed we need to suffocate that 100hp down to 14hp.

agreed???

so the psi or lack of it matters not. if you have more psi ahead of the throttle SOMETHING must be done so that no more than 14hp is produced and that something is throttling back until all the conditions in the intake after the throttle are AS THEY WERE BEFORE.

now if you are at or very near WOT and are accelerating or going top speed, if the ram works you may see something. but we are talking fe driving.

I agree Frank, Totally agree.

Point is instead of choking out some of the torque as pumping losses we use it to propel so we go x+1 speed. So we get there slightly faster(we didn't use anymore fuel just used less fuel to rotate the pistons around and therefore more fuel went to the road) which means the engine doesn't run quite as long.

This is really interesting because I have somewhat of a "ram air" set up taking in air from directly behind the grill. I think that FrankLee and Unchosen both have their points here. To maintain a given speed with a ram air set up you would just let up on the throttle slightly; however, if we added in the variable "traffic conditions," which sometimes require more acceleration than we'd like for FE, a ram air set up would allow you to open the throttle less for a given acceleration.

ok i see where you are coming from.

but when the o2 sensor fixes the ratio are you sure we didn't use more fuel?

Its hard to say Frank,

The problem with getting a little boost in speed out of the same amount of fuel(less pumping energy) you create a little more air in the intake(ram scoop) and then burn a little more fuel.

In Turbine engines you get runaway caused by the increased intake speed increases combustion energy increases compression, increases combustion. . .and so on and it. In a turbine driven engine its a big deal. . .reciprocating. . .not so much because there is only so much pumping loss to overcome.

Its going to be a small improvement with a ram scoop, but there theoretically is an advantage so long as you don't lay into the throttle too hard with the added power. That said. . .it is a real improvement opposed to a "restricter plate" WAI.

And no the air density influencing the engine has nothing to do with why the run at altitude. Its a calculus maximization problem. The higher you go the crappier your turbojet engines work, but you get ALOT less air density. They go to 30+ thousand feet because at that altitude the radial compressor at the front of the turbojets can still supply enough compressed air(If theoretically they could run the engines at sea level and the aircraft at 30K feet they would) to make the turbines push enough.

If you think I'm wrong. . .ramjets are turbojets which let the compressor "runaway" and compress the air to the limits of the housing. Then it has a giant scoop to force feed air into the engine. They are actually more efficient than regular jets.

The only problem is. . .you have to piggyback them up to mach 1.5 or so and then drop and engage them. It costs a ton of fuel to launch and so its not viable but a WAI and less air in the engine blah blah blah. . .its a restricter plate, look it up under NASCAR.

Interesting, operating principal. Seems like there would be a centrifugal stress issue with these.


For the sake of staying on track, I haven't picked though this entire thread but, we do know that open loop engages at X throttle position on MOST management systems, regardless of manifold pressure. With that, it is possible to achieve a higher MAP at <X throttle position. Due to the choked gas flow (among other working factors); the mass air flow of the intake manifold is higher with the slightly pressurized environment pre-throttle plate at <X tps in turn producing more hp in closed loop than the manufacturer intended for it to.

Obviously, this would eventually get dangerous or inefficient if the engine were to see these higher pre throttle plate pressures as it would be too lean to produce power efficiently and safely.

If you are force inducing air into the engine the MAP vacuum will be less at any given throttle position. I think thats what you are saying. . .?

Also the 02 would throw a CEL and kick out the MAP readings if it got too lean. the EGT would probably also chime in. That situation it would go limp and run rich.

Although. . .the MAP is going to try and run around 14.7 in open or closed. . .you just won't be getting feedback from the O2 and the EGT won't factor in as much to the fuel injection. Open or closed the MAP is going to keep it from getting too lean unless you tamper with the wiring or the ECU(insert resistors or change the fuel-air map.)

If you force air in the engine, absolute pressure in the manifold will increase with increased pre throttle body pressure (throttle position being equal).

Higher pressures before the throttle plate have negligible effect on fueling in open loop ( or closed loop) unless you exceed the highest mapped pressure, the ecu will still be reading from the same section of the map tables regardless of how much air you cram in the intake tube. No correction beyond normal fluctuations would be required by the ecu.

Closed loop, different story. I think you are referring to a 350Z? WOT operation will never be 14.7, but between high 13's to high 12's. As far as most management systems go, closed loop is only triggered by throttle position, but I imagine some are pressure and/or rpm. There normally is no correction for open loop other than referencing manifold pressure and rpm, everything else is simply a multiplier of sorts, coolant temp, intake air temp, ect.

Granted, all this is in reference to a manifold pressure density type system, mass airflow system is a bit different

I must be falling behind, there is a system out now that has a correction based on egt's? Wonder how they pulled that one off...

The only difference in open and closed loop is. . .the ECU gets data from one location or multiple. Open it gets data only from the MAP(MAF) and then plugs the data in and recovers how much fuel is needed. In open mode its more conservative and adds a little more fuel than it needs(I'm not talking 350z) to make sure it stays outside of lean. In closed it does what I just said and then the ECU takes data from O2 sensors(and nowadays alot more) and tries to get closer to what its mapped for. Eco cars are going to try to get right at 14.7 whereas sportier cars are going to hover around in the rich region and just have a tighter AFR band.

As far as the topic at hand is interested though a RAM air could theoretically improve FE, but I can't say for certain because I haven't tried it myself. I can't recall which user it was that has done it, but I believe them. WAI like I said is just a big restricter plate that pushes your driving tendencies towards ecohabits(unless you have lean burn and it has a required minimum AIT, then its a restricter and a system hack).

why don't we all just get a diesel so we don't have to worry about throttle plates? :D

I have a new idea... In all new cars, take a coil spring from a truck, and use it for the gas pedal spring. Americans are lazy, and would rather work less and drive slower than push the pedal with lots of might to go 75mph. Seems like a crazy, might work plan to me :thumbup:

I think the point being discussed is that WAI's suck, it's basically reducing your WOT HP potential of your engine.
If you have a ram air setup, it's irrelevant because the throttle body will just be open a little less to provide X-HP worth of air to cruise the car down the road.
Btw 14.7:1, while being the "optimal" fuel number, isn't always so.
When I had my ECU chipped and tuned for my Civic, we were running a wideband and got the cruise AFR to 16.0:1 before it started to lean pulse. That's 8.8% better efficiency right there, and I saw an increase in cruise mpg of 2-3 MPG.
Now if I had a crappy WAI I'm sure I would have ran into detonation before that point and would be running a more 14.7ish AFR...