Ram air into supercharger/turbo...seen it done buy why?

[Jonny Hotnuts]

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

[hotrod]

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

[McRat]

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.

[maj]

Some bikes do

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

[Super Kaz]

 

[John Noonan]

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 !
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 !

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...

PS. the S in "debris" is silent...

[4-barrel Mike]

Actually, you're both right:

http://en.wikipedia.org/wiki/F.O.D.

Way back when, "damage" was generally used in Naval aviation.

Mike

[hayaboosta]

Actually, you're both right:

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!

As they say...Ya learn sumthin' new everyday.

[John Noonan]

Blah Blah Blah....

[Stainless1]

Now that we got past the semantics, be aware ice is FOD in a turbo.... 

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.

[mtkawboy]

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.

[Super Kaz]

Actually, you're both right:

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!

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 ! 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 ! You really need to get out of the House more as your PMS is getting Worse!
Kaz..............

[John Noonan]

My point was made...

[Blue]

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.

[joea]

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.........