Landracing Forum
Tech Information => Technical Discussion => Topic started by: Jonny Hotnuts on September 30, 2008, 10:14:32 PM
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I see some people do ram air into the blower but on the flip side many (bikes for instance) dont use any form ram air.
I could see that you could gain PSI by having ram air but what is the difference between getting a PSI advantage because of ram air vs. turning up the boost psi 1 pound? It would seem to me that the aero advantage by not having a snorkel would outweigh the gain in PSI when you could just jack the boost a bit to start with.
-JH
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You allow the turbo to do less work for the same manifold pressure, and thus get more effeciency. It is especially helpful if the turbo is working at its limits.
For example suppose your turbo is most efficient at a pressure ratio of 2.7:1. The pressure ratio is the ratio of the outlet pressure divided by the inlet pressure.
Lets suppose on a given day absolute air pressure is 12.5 psi. If you run the turbo at its ideal effeciency, you get a max boost of 12.5 x 2.7 = 33.75 psi.
Now you add 1 psi ram boost to that same setup, your inlet pressure is now 13.5 psi, so your max boost becomes 13.5 x 2.7 = 36.45 psi.
You gained 2.7 psi manifold pressure by adding 1 psi of ram boost!
Larry
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Ramair is a hotly debated subject in the hotrod world. Physicists say it cannot have any effect at the speeds cars can move at. The mass of air behind the column of air going into the intake doesn't have enough force to compress air.
However... I'm not convinced. I've seen it work at the drag strip in back-to-back testing at speeds as low as 100mph.
A turbo will generate a partial vacuum in front of it even if there is no intake tube or aircleaner. Perhaps filling that vaccuum is where the gains are at.
Say a turbo inducer is 3.2" ID. It will collapse a 5" ID tube mounted to it. Anything you can do to allow easier airflow in, is going to show in reduced turbo drive pressure, hence less spent gases in the cylinder when the exh valve closes.
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Some bikes do
(http://img.photobucket.com/albums/v378/maj750/DSC02099.jpg)
From air pressure at speed charts (i think posted on Landracing some time ago )i figured the ram effect at ~200mph would just about cancell out the loss of pressure from altitude
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:roll:
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Jonny,
Beware of FOD{Foreign Object Damage} it's Not very wise to leave your Turbo exposed to Unfiltered Air! Specially Bonneville{I have a couple Broken Turbo to prove it}
Yes you might make a few more HP,but having to buy a new one after every Race sucks :oops: !
If anything build a Cooler Box{Fill it with ice" with a screen covering going into it and going out. It will cool the air intake charge {= densir air,}and it will filter out any Big Stuff for even more hp :-o!
Kaz,
F.O.D. stands for "Foreign Object Debris"
Good info about a Water-to-air-intercooler...
FYI: I now run a small "scoop" that is aero and still "forces" incoming air in to the inlet side of the turbo...kinda like Joe Amo did several years ago... :-P
PS. the S in "debris" is silent... :cheers:
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Actually, you're both right:
http://en.wikipedia.org/wiki/F.O.D. (http://en.wikipedia.org/wiki/F.O.D.)
Way back when, "damage" was generally used in Naval aviation.
Mike
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Actually, you're both right:
http://en.wikipedia.org/wiki/F.O.D. (http://en.wikipedia.org/wiki/F.O.D.)
Way back when, "damage" was generally used in Naval aviation.
Mike
Good point Mike!
At least when I spent my time in the USAF we called FOD (Foreign Object Damage).
I think John has too much time on his hands to research these things! :-D
As they say...Ya learn sumthin' new everyday.
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Blah Blah Blah.... :mrgreen:
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Now that we got past the semantics, be aware ice is FOD in a turbo.... :roll:
JNuts, we used our NACA duct to feed a box that held the filter for our turbo intake. I've seen the damage salt can to the compressor wheel. I'd say it helped the HP, but we are still tuning... :| this turbo stuff is new to us.
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I wonder if the drag strip gains at 100 mph arent more from cooler outside air then hot under hood air into the carb rather then the ram effect which cant hurt.? Just a thought.
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Actually, you're both right:
http://en.wikipedia.org/wiki/F.O.D. (http://en.wikipedia.org/wiki/F.O.D.)
Way back when, "damage" was generally used in Naval aviation.
Mike
Good point Mike!
At least when I spent my time in the USAF we called FOD (Foreign Object Damage).
I think John has too much time on his hands to research these things! :-D
As they say...Ya learn sumthin' new everyday.
John,
My Dad spent 45+years in the USAF{23 Year CIVIL SERVICE GS-13 or 14},and was the Head Tech Rep for the F-16'S at Nellis AFB. I think he knows a little more then you,and me put together :roll:! He would always bring me STUFF(FOD} from His Birds. They had a hell of a Time keeping Sand out of the Turbines during Desert Storm{He was the 1st Civilian at Nellis AFB to be sent over}So I'm going by what the Pro said not a unemployed Bum like yourself :wink:! You really need to get out of the House more as your PMS is getting Worse! :-P
Kaz..............
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My point was made... :wink:
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Ramair is a hotly debated subject in the hotrod world. Physicists say it cannot have any effect at the speeds cars can move at. The mass of air behind the column of air going into the intake doesn't have enough force to compress air.
Please refer said "physicists" to me. The math is simple and many pure scientists make incorrect assumptions just like the difference between "traction" and "friction".
The math works out just fine, the question of whether it is worth the additional drag is more of an aerodynamics integration issue. IM<HO, the aerodynamics of 99% of all LSR cars are so bad that ram air snorkels and tunnel rams in use by many yield better ram air and less drag than most of the off-the-wall alternatives I've seen.
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if ya looked at the numbers of records set by those without
air filtration to supercharging devices.........compared to those
with..........the results would be staggering......
resembling very closely those records set by turbocharged v-rods
compared to turbocharged busas.........
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I'm done thanks.
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As usual this has been discussed before
Getting air to Turbo:
http://www.landracing.com/forum/index.php/topic,3689.0.html (http://www.landracing.com/forum/index.php/topic,3689.0.html)
Ramair is a hotly debated subject in the hotrod world. Physicists say it cannot have any effect at the speeds cars can move at. The mass of air behind the column of air going into the intake doesn't have enough force to compress air.
Physicists? Care to quote specific facts? Air is in fact incompressible at LSR speeds. But there is ram air pressure.
Check this out:
http://naca.central.cranfield.ac.uk/reports/1927/naca-report-247.pdf
A report on ram air pressure . . . from 1926!
The formula is mph2*0.0000176
This gives 0.704 psi at 200 mph. Not much, but without it you not only don't have pressure, you have a partial vacuum at the inlet, NA or turbo.
At a standstill the turbo is pulling a vacuum in the area around the inlet. Using a properly designed inlet to take advantage of the ram air effect makes the turbo more efficient.
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At a standstill the turbo is pulling a vacuum in the area around the inlet. Using a properly designed inlet to take advantage of the ram air effect makes the turbo more efficient.
I have no doubt that having ram air into a turbo will make the turbo more efficient. Do you think that this turbo efficiency increase outweighs the aero drag created by having a snorkel?
I see a few cars that have their intake located in the front of the nose and this is were I would put mine IF I could, mine has to be located in the rear 50% and has to be somewhat tall to get any clean air. More often than not I see large (and many times IMO bad aero designed) tunnel rams on the hood.
Just makes me wonder if having increased turbo efficiency is worth it....considering the fact that I see any HP lost because of decreased efficiency could be made up with a pound more PSI.
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Kaz i simply posted that reality speaks for itself............
not sure why you feel compelled to whine about your whoes with the v-rod......
you are on here trying to sway folks to take your advice on ram air with respect
to turbo's.......directly in contrast to the worlds fastest sit on bike guy ...mr noonan......
(and many other worlds fastest vehicles)
i didnt bring up your personal accomplishments..........you have
we are aware of many of your supercharged results from your posting here......the blownup
turbo truck last year, the blownup v-rod, and the partially blown up sti needing piston work....... :-o :roll:
REMEMBER PRACTICE DOES NOT MAKE PERFECT........PERFECT PRACTICE MAKES PERFECT..... :-)
ps no one here said anything about how hard you have worked............not sure why you need
to bring that into this discussion about knowledge..............working harder isnt always working
smarter..........if you want to compare work ethic with regard to bonneville......many of us
could share some fine stories..... :-D
Joe :-)
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As usual this has been discussed before
Getting air to Turbo:
http://www.landracing.com/forum/index.php/topic,3689.0.html (http://www.landracing.com/forum/index.php/topic,3689.0.html)
Ramair is a hotly debated subject in the hotrod world. Physicists say it cannot have any effect at the speeds cars can move at. The mass of air behind the column of air going into the intake doesn't have enough force to compress air.
Physicists? Care to quote specific facts? Air is in fact incompressible at LSR speeds. But there is ram air pressure.
Check this out:
http://naca.central.cranfield.ac.uk/reports/1927/naca-report-247.pdf
A report on ram air pressure . . . from 1926!
The formula is mph2*0.0000176
This gives 0.704 psi at 200 mph. Not much, but without it you not only don't have pressure, you have a partial vacuum at the inlet, NA or turbo.
At a standstill the turbo is pulling a vacuum in the area around the inlet. Using a properly designed inlet to take advantage of the ram air effect makes the turbo more efficient.
Yeah, poor choice of words. I should have said "much effect" instead of "any effect".
It's been a long time since I read anything on ram-air, but IIRC, the gains we see don't line up with the science. That doesn't mean the science is wrong, just that there must be another variable.
Example:
I'm on the dyno earlier this year testing intakes on stock Duramaxes (turbo diesel engine, 2.44" inducer) The hood is open during testing. ~20mph (WAG) air is coming from a fan. Using a Banks intake we did some pulls. It's a ram-air design, and I sealed the intake. When I aimed the airstream towards the inlet, we picked up 8 rwhp over aiming it at the whole front of the truck. No way a small electric fan is measurably pressurizing the intake, and a fan doesn't cool air, in fact, a fan heats the air (electric motor). The result was repeatable and stretched across the RPM band from 2500 to 3500 rpm (our powerband).
Yes, perhaps it's due to the vacuum a charger creates at the inducer (even with an open inlet). But for now, when I'm allowed to use ram-air inlets, I do so. The gains increase at the dragstrip. Most aftermarket intakes for late model GM products do nothing but empty your wallet and make more noise. GM ain't stupid, if they can pickup mileage and power with an intake, they do it, their intakes are very good for OEM. But the aftermarket CAI's that have a true ram-air design will show gains when airflow is present, even at freeway speeds.
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""""I have no doubt that having ram air into a turbo will make the turbo more efficient. Do you think that this turbo efficiency increase outweighs the aero drag created by having a snorkel?""""
I often wounder if there is a lot of drag created by the snorkel, since if it is properly sized and designed, any air it sees at speed is sucked into the engine and not piled up in front of it.
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did anyone see blues post earlier..........?
"""The math works out just fine, the question of whether it is worth the additional drag is more of an aerodynamics integration issue. IM<HO, the aerodynamics of 99% of all LSR cars are so bad that ram air snorkels and tunnel rams in use by many yield better ram air and less drag than most of the off-the-wall alternatives I've seen."""
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Don't know about other folk's engines, but it seems our engine draws air in at over XXXmph if my math is right. I'm at about 140lb/min of air.
So a ram-air inlet would probably improve aero, not hurt it.
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DOH!!
That's not the right number. That was for our point of restriction IIRC. Next time I'm doing math, I'll figure the true MPH at the inlet. But the air is not hitting a "wall", the air is travelling inwards at a good clip.
That's probably the missing variable. In static state, the engine must accelerate the air from 0mph to xxxmph in order to move it. By creating a ram-air inlet, the air gets a head start.
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joea --
I saw blue's reply and understand what he's saying. But -- some LSR classes won't allow you much room to dabble with the aero and the ram air won't hurt the overall that much and may produce a plus.
I very much respect blue's knowledge and experience. But I'm sure he knows the limitations lots of us are under in some of the "traditional" classes.
Stan
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absolutley Stan, i see it as you do.....likely a bigger net positive than
negative for many of us...
Joe :)