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

[doviatt]

Originally Posted by basslover911

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?

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.

[basjoos]

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.

[Frank Lee]

Geez Louise, ram air and fe?

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.

[doviatt]

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.

[Bicycle Bob]

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.

[tjts1]

Originally Posted by doviatt

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.

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

Originally Posted by doviatt

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.

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

Originally Posted by doviatt

(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.

I think you need to make an effort to read more carefully. I said:

Originally Posted by tjts1

The engine will still breath the same ammount of air and have the same intake if you increase air pressure, reduce throttle angle and maintain the same load. Take the engine up to 30k feet where it can only produce 30% as much power at WOT and it will still consume the same amount of fuel at the same load.

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.

Originally Posted by doviatt

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.

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.

Justin

[doviatt]

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.

[tjts1]

[Frank Lee]

At least the owl is alert.

[Peter7307]

Originally Posted by basslover911

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

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.