electric boost?

[88justin]

anyone thought about these things. www.electricsupercharger.com

[Gojeep]

Mmmmmm, and the world of snake oil might fit the same category.:rolleyes:
Just connect a 12 volt hair dryer to your inlet tube and your away:eek:

[satan]

It's just a Ducted fan and electric motor (from the R/C airplane world) - no necessarily worth the $$ an easy DIY --

I seem to remember a guy strapping a leaf-blower running off of a power inverter onto a ZJ (or WJ) - sounds about as practical to me...

[Drewlee77]

I'm curious if the idea is sound though... could an electric motor effectively provide a small amount of "boost"? I mean, all a turbo is is a ducted fan run by exhaust gases, and a supercharger is just a ducted fan run by a pulley. Why couldn't you run an electric motor? Obviously, you would, in theory, need a heavier duty alternator (in practice you may have enough extra already) to run the motor.. but would the extra drag from the alternator add up to the extra power provided by the boost? Alternators usaully only sap a couple HP anyway...and that is at higher RPMS. So, in theory, couldn't it work?

[satan]

I didn't say that it didn't work -- it does -- used to do it on a vega (give a thought on how long ago) -- for fun, there are similar fans that run MUCH better pressures/deliveries available for gas motors (OK so a little nitro in the oil 2-strokes) -- not so much on-demand as a good time on the 1/4 mile --

There are improvements - but the $ for only WOT gains are not that impressive -

A good "itteration" for this type of fan would be to tune the output area to best accept the volume/flow from the fan (the pressures available are really dependant on the fan not seeing much of a load - good design could build a suitably sized heimholtz chamber after the fan to ensure that the ducted fan was blowing into a reduced pressure area (similarly, proper tuning could apply an increased pressure to the intake)...

The current implementation is kinda - "fit this to what you have" - with a little effort some very specific applications for intakes couldprobably eek-out another 2-3% or more...

[Ecomike]

Has anyone ever tried this or a similar device, If so what were the results?

[mgreen84]

http://www.naxja.org/forum/showthread.php?t=918652&highlight=eram

Read this........

[Stumpalump]

They work great and heres why. If this whole jeepin thing is a hobby and you can gain a smidgon of anything then it was worth it and you had fun. I put MSD and Jacobs ignitions on jeeps, boats and hotrods and they claim on the dyno you only see a tiny gain. OK, but the drivability and throttle response is great and it's worth every penny just for that. I modify my air inlet temperture sensor on every computer car I ever owned. Did it gain a lot of power? No. But I can feel a snapper engine and I have the satisfaction of knowing I improved somthing. Same with adding a K&N or drilling out your air box for more air. Does it help alot? No. But at some RPM ranges you can fell a difference. Same for a throttle body spacer or fancy spark plugs. The may help a tad at a certain load or certain rpm range and you may percieve a difference. All good.
Now lets look at the electric fan/Marine bildge blower/Esupercharger or whatever you want to make it out of. At wide open throttle your engine vacuum will overpower the output of the blower and you will see no gain on a dyno. OK but what about part throttle or when the throttle is close and you first crack the throttle plate open. You will have a jump start of air going into your engin and you may feel a slightly more responsive gas pedal.
So this alone may be worth the time effort and money if you are the type of person that can feel his seat of the pants. Ever notice when hard wheeling the same guys allways seem to break and others never seem to break? Those that don't break may be a little more sensitive to the forces they feel. This is not really good or bad because those that break are somtimes really great drivers. So if you are the type of person that really went wow when you added a K&N,free flowing muffler, throttle body spacer,computer chip or any of the other modifications that don't really do anything then you will be happy with a fan in your intake.
Look at what a winning race team is doing on a weekday night.They are doing stuff like packing front wheel bearings, cleaning almost clean air filters,applying wax to the paint and all the stuff that won't help.Hmmmm.

[coastie124]

There are real electric superchargers out there. (exspensive and don't last very long) These are not them. These are pretty much just blower motors stuck on an intake. Plus if your going to spend $600 on this might as well spend the cash to get the real supercharger kits. I'd love one.

[jeeperjohn]

Dude, a buddy of mine's friend's cousin bought one of these and got 100 extra horsepower. He was so fast they wouldn't let him race "regular" jeeps at the local track. Then he bought the "tornado" and got an extra 30 HP! Since he was on a roll he bought a "top secret" oil additive and got 12 more MPG! And his engine ran 30* cooler!

[coastie124]

There are real electric superchargers out there. (exspensive and don't last very long) These are not them. These are pretty much just blower motors stuck on an intake. Plus if your going to spend $600 on this might as well spend the cash to get the real supercharger kits. I'd love one.

[MudDawg]

The people who are selling these things must also take candy from babies, steal from the collection plate, kick puppies, shove little old ladies, and all of the other sorry, rude, sick things I can think of. The claim that that POS will improve power is a kick in the nutz to anyone with knowledge of how fans work...marketing that thing as something to "boost" air in an engine is rediculous....the blade on that this is a "free air" blade....it will not push more that MAYBE .2 inches of water column....and the CFM can't be over maybe 30 at a very low PD....

Yes there are fans that can or could be used to "boost" an engine, but this ain't one of them....and neither are the ones that use a 3" squirrel cage like a "boat bilge vent blower"....I'm gonna go :puke: now.

[WheelinJR]

useless crap.

[Ecomike]

Here is my thinking on the topic.

First off I see lots of replies, thanks, but I do not see any one that has actually tried this one, perhaps because it looks way overpriced :shiver:to all of us, and I think only one poster that claims he used something like it once and that it worked. I must admit it looks way overpriced. Interesting to note that that sucker pulls 50 something amps and runs at 25,000 something rpm :shocked: (as I recall), which is a bit more than I was thinking of considering, but is considerable!

MudDawg, from the specs I read on it (deep in the web site) this think is very a high rpm turbine, pulling considerable power and as I recall claiming to move something like 600 or 800 cfm at nearly 1 lb of pressure. Now as is typical with silver tounged sales ads that is probably 800 cfm free air, and the flow stops at slightly over 1 lb of back pressure) .

That said there are roughly 2.03" of Hg (column gauge pressure) per PSI, so that would be roughly 4" of (Hg) pressure if their 1 psi claim is accurate.

Now a typical engine at steady state (not accelerating) pulls about 20" of Hg negative pressure (vacuum). Since atmospheric pressure is about 29.9" Hg, that means the air that is reaching and filling the combustion chamber is only about 1/3 of atmospheric pressure or 10" of Hg postitive pressure. If the blower device delivers 4" of Hg pressure increase, taking it from 20" to 16" of Hg vacuum, then the air reaching the combustion chamber would be closer to 50% of atmospheric pressure. That would be a (33/50) * 100%= 66% increase in effective air mass in the combustion chamber. The O2 sensor would compensate with more fuel to maintain the A/F ratio, and thus more power would be delivered.

Now the problem I see is that once you turn on the blower, the O2 sensor compensates, the engine power goes so up some, so the rpm goes up some and the engine draws more air. The question in my mind is does the engine vacuum go back to 20" at the new steady state with the blower on or does it settle at 16" of Hg or somewhwhere in between. If it goes back to 20" then this device would be useless or would be equivalent to just boring out the throttle body and installing more air filter area which uses no elelctrical energy. But turbo charges and superchargers do work, and they work on the same principle, they just have more pressure to deliver the air with, so they deliver more air mass per cubic meter!!!

It does make sense to me that at WOT this device (or one with similar specs, and more reasonably priced) would be equivalent to boring out the throttle body, inceasing the air filter area and essentially reducing the pressure losses through the air intake system, thus allowing a small increase in the air mass flow rate to the engine!

Now I see two different aspects to this. One is if we look at a single cylinder stroke the only way to get more power out of each stroke is to get more air mass (the volume, displacement is constant!) and thus more fuel (O2 sensor becomes our friend) into the cylinder during each stroke. So increasing the intake manifold absolute pressure is needed to do that. Opening the throttle rapidly to WOT during acceleration does a nice job of that until the engine adjusts and catches up and the absolute manifold pressure gets back to equilibrium (20" Hg). A bored throttle body and larger air filter shows some of its impact during the first moments of acceleration, by a allowing a bit more air mass to flow to the cylinders. But as the engine reaches steady state operation (crusing) it has much less effect. Think of it this way, at 30% of WOT with a stock throttle body and air filter, it would operate about the same as say a bored throttle body and larger air filter at 29% of WOT. I can effectively duplicate the bored TB & larger AF by just opening the throttle a bit more. But at WOT, or near it, it would be another story. In that case a larger air filter and bored throttle body during WOT acceleartion would be more effective at increasing instantaneous torque and power, when towing, going up hill, or passing, at max power and low RPMs (i.e. trying to speed up fast, acceleration).

OK, I am running out of steam here, so I will post this and come back and finish my thoughts a little later.

[mgreen84]

They work great and heres why. If this whole jeepin thing is a hobby and you can gain a smidgon of anything then it was worth it and you had fun. I put MSD and Jacobs ignitions on jeeps, boats and hotrods and they claim on the dyno you only see a tiny gain. OK, but the drivability and throttle response is great and it's worth every penny just for that. I modify my air inlet temperture sensor on every computer car I ever owned. Did it gain a lot of power? No. But I can feel a snapper engine and I have the satisfaction of knowing I improved somthing. Same with adding a K&N or drilling out your air box for more air. Does it help alot? No. But at some RPM ranges you can fell a difference. Same for a throttle body spacer or fancy spark plugs. The may help a tad at a certain load or certain rpm range and you may percieve a difference. All good.
Now lets look at the electric fan/Marine bildge blower/Esupercharger or whatever you want to make it out of. At wide open throttle your engine vacuum will overpower the output of the blower and you will see no gain on a dyno. OK but what about part throttle or when the throttle is close and you first crack the throttle plate open. You will have a jump start of air going into your engin and you may feel a slightly more responsive gas pedal.
So this alone may be worth the time effort and money if you are the type of person that can feel his seat of the pants. Ever notice when hard wheeling the same guys allways seem to break and others never seem to break? Those that don't break may be a little more sensitive to the forces they feel. This is not really good or bad because those that break are somtimes really great drivers. So if you are the type of person that really went wow when you added a K&N,free flowing muffler, throttle body spacer,computer chip or any of the other modifications that don't really do anything then you will be happy with a fan in your intake.
Look at what a winning race team is doing on a weekday night.They are doing stuff like packing front wheel bearings, cleaning almost clean air filters,applying wax to the paint and all the stuff that won't help.Hmmmm.

ok, seeing that you seem offended....I don't see spending 3-500 dollars on 2 horses when you could pour in a bottle of Octane Booster and get the same results....I see the intention behind the idea, but for your everyday joe, we're not running the indy 500 with an xj and that 3-500 can be spent better elsewhere. By all means if you think its worth it, go for it...hell give me a call at work I'd be glad to make the sale... as for me I'll keep it logical.

[Ecomike]

Stumpalump,

I am inclined to believe most of what you are saying. I think the problem with many of these devices and mods, including anything that improves air flow, is that they are hard to measure on a dyno perhaps because they have little measurable effect at steady state engine speeds (?) which is partly because nothing is changing (?), but perhaps are more effective for a few seconds during heavy acceleration, i.e. a noticable change in throttle response!

You said "At wide open throttle your engine vacuum will overpower the output of the blower", I am not sure I agree with this, does this not depend on the blowers maximum capacity?

I would agree with this part "but what about part throttle or when the throttle is close and you first crack the throttle plate open. You will have a jump start of air going into your engin and you may feel a slightly more responsive gas pedal."

In my case I am looking for a way to get a few more HP out of my SD22 (Nissan) 2.2 L, 68 HP stock, diesel (Naturally aspirated with a pneumatic governor on the IP) that is my 85 Jeep Cherokee. (No I don't need a stroker, this SD22 is getting a good 34 MPGs stock for me). It is just a little bit light on power going up hill with the A/C on and multiple passengers on board, in other words when heavily loaded I have to drop down to 3rd or 4th gear from 5th gear even at WOT. I know some guys who are trying custom TCs on this engine, but IP control is a bit of an issue still for them. They have determined that the throttle body is a severe restriction even when TC it.


They work great and heres why. If this whole jeepin thing is a hobby and you can gain a smidgon of anything then it was worth it and you had fun. I put MSD and Jacobs ignitions on jeeps, boats and hotrods and they claim on the dyno you only see a tiny gain. OK, but the drivability and throttle response is great and it's worth every penny just for that. I modify my air inlet temperture sensor on every computer car I ever owned. Did it gain a lot of power? No. But I can feel a snapper engine and I have the satisfaction of knowing I improved somthing. Same with adding a K&N or drilling out your air box for more air. Does it help alot? No. But at some RPM ranges you can fell a difference. Same for a throttle body spacer or fancy spark plugs. The may help a tad at a certain load or certain rpm range and you may percieve a difference.
Now lets look at the electric fan/Marine bildge blower/Esupercharger or whatever you want to make it out of. At wide open throttle your engine vacuum will overpower the output of the blower and you will see no gain on a dyno. OK but what about part throttle or when the throttle is close and you first crack the throttle plate open. You will have a jump start of air going into your engin and you may feel a slightly more responsive gas pedal.
So this alone may be worth the time effort and money if you are the type of person that can feel his seat of the pants. Ever notice when hard wheeling the same guys allways seem to break and others never seem to break? Those that don't break may be a little more sensitive to the forces they feel. This is not really good or bad because those that break are somtimes really great drivers. So if you are the type of person that really went wow when you added a K&N,free flowing muffler, throttle body spacer,computer chip or any of the other modifications that don't really do anything then you will be happy with a fan in your intake.
Look at what a winning race team is doing on a weekday night.They are doing stuff like packing front wheel bearings, cleaning almost clean air filters,applying wax to the paint and all the stuff that won't help.Hmmmm.

[Stumpalump]

Stumpalump,

I am inclined to believe most of what you are saying. I think the problem with many of these devices and mods, including anything that improves air flow, is that they are hard to measure on a dyno perhaps because they have little measurable effect at steady state engine speeds (?) which is partly because nothing is changing (?), but perhaps are more effective for a few seconds during heavy acceleration, i.e. a noticable change in throttle response!

You said "At wide open throttle your engine vacuum will overpower the output of the blower", I am not sure I agree with this, does this not depend on the blowers maximum capacity?

I would agree with this part "but what about part throttle or when the throttle is close and you first crack the throttle plate open. You will have a jump start of air going into your engin and you may feel a slightly more responsive gas pedal."

In my case I am looking for a way to get a few more HP out of my SD22 (Nissan) 2.2 L, 68 HP stock, diesel (Naturally aspirated with a pneumatic governor on the IP) that is my 85 Jeep Cherokee. (No I don't need a stroker, this SD22 is getting a good 34 MPGs stock for me). It is just a little bit light on power going up hill with the A/C on and multiple passengers on board, in other words when heavily loaded I have to drop down to 3rd or 4th gear from 5th gear even at WOT. I know some guys who are trying custom TCs on this engine, but IP control is a bit of an issue still for them. They have determined that the throttle body is a severe restriction even when TC it.

I think blowers were first used on diesel engines and they benifit more than a gas engine. A diesel runs wide open all the time and you just add more fuel to go faster. In other words you would see gains on that small diesel that we may not see on our 4.0 gas burners. I googled this about 2 years ago and remember seeing all kinds of interesting stuff available and you can find just the blowers without having to fork over a lot of $. I say that if you are a gear head and are not ready for major complicated mods why not have some fun playing around with it? Go to a truck stop and pick up a gallon of lucas fuel additive for diesels. That stuff is like majic in my chevy diesel truck and my neibors small diesel tractor plus it adds the lubrication back in the fuel that is now refined out of it. Keeps your injector pump and injectors clean,lubed and happy.
Here is another place to steal ideas from and if you search you can find just the fan/blower and rig up somthing cheap. Check the Honda/toyota NOPI type websites because these guys try anything to gain power. or just Google your engine and add "power increase" to your search.
http://www.mimousa.com/home.asp?dir=products&prod=952

[Ecomike]

A diesel runs wide open all the time and you just add more fuel to go faster.

Go to a truck stop and pick up a gallon of lucas fuel additive for diesels. That stuff is like majic in my chevy diesel truck and my neibors small diesel tractor plus it adds the lubrication back in the fuel that is now refined out of it. Keeps your injector pump and injectors clean,lubed and happy.


The Nissan SD22 is an oddball deisel. It is naturally aspirated, with a Bosch Kiki injection pump that has a dual governor on it. One side of the governor is a pnuematic governer that operators on the air pressure differential across the throttle body which controls the fuel injection rate.

I have been using Power Stroke with Slick Deisel with this guy since 2002. This engine loves the cetane boost and it has all the other great snake oil additives in it too, LOL.

I was oringinally thinking of a small centrifugal blower similar to the one on the link you posted. That plastic one and the really poor english with it, and I will say BS description they have turned me off to theirs. I also suspect the turbonator (same people) is BS, but I could be wrong. It might work in front of a mass air flow sensor by pre rotating the air, but I do not have an AF sensor on my Jeeps.

I just spent an hour researching the electric supercharger guys and their patent ( free at www.uspto.gov ) and they do have a real patent (which explains why they charge so much for it). I read all their tech stuff and everthing they say in the tech section actually checks out. I think the only reall issues with these guys is value, but they also have a page where the inventor lists all the other gadgets he bought, installed and their performance (or lack thereof)and their cost, and what prompted him to come up with his electric fan gadget. They have it set up to where it only turns and only pulls power at WOT! They make a sound logical cost comparison of return (HP) for investment ($$$s) comparison to intake manifold, throttle body and exhaust system upgrades that makes sense.

I sent them an email asking them for feedback on the Nissan SD22 (1982) deisel engine application. It will be interesting to see what kind of response I get from them. In reality I would probably select an oem blower/fan myself to play with as I have a lot of industrial fan/blower experience, being an engineer (Chemical/Industrial) myself.

[lawsoncl]

At least the math works for the eram supercharger. Pulling 50 amps is about 3/4HP whcih at 250 cfm is about 1psi of pressure increase. Depending on the engine you could see 5-10 HP from a 1psi boost.

Now for the tiny fake versions that pull 3-4 amps, at 250 cfm you're looking at less than 0.1 psi. You might even be getting less overall HP since you have to create those amps using the altenator.

Personally, I'd rather have a real supercharger and all the low end instant grunt that comes with it.

[coastie124]

Is anyone running a turbo on the SD22?

[MudDawg]

There are no end-on pictures of the "device" ....but if it is built like the "demonstration video" shows it, it is a single fan......and if so, I will stand on my original opinion....and if the tube size is around 3", there is no way the motor has much power....there isn't enough room....and if they have invented a way to create a spatial anomoly that allows 10 pounds in a 5 pound sack....I have a complete set of air pressure and velocity measurement tools....and experience using them....in other words unless I see that thing run on a test bed with my instruments and myself doing the measurement....its pure :bs:

[jeeperjohn]

There are no end-on pictures of the "device" ....but if it is built like the "demonstration video" shows it, it is a single fan......and if so, I will stand on my original opinion....and if the tube size is around 3", there is no way the motor has much power....there isn't enough room....and if they have invented a way to create a spatial anomoly that allows 10 pounds in a 5 pound sack....I have a complete set of air pressure and velocity measurement tools....and experience using them....in other words unless I see that thing run on a test bed with my instruments and myself doing the measurement....its pure :bs:
How much does this thing weigh? add 20 lbs or so and there goes 1HP. And then, if this thing is pulling 50 amps consider the drag on the alternator. Result= no net gain considering you have to spend your time installing this thing. This thing is even worse than the "tornado" because it requires modification to install.

[Ecomike]

Is anyone running a turbo on the SD22?

YESSSSSSS! Some friends of mine at:

http://nissandiesel.dyndns.org/viewtopic.php?t=495

Even has cool eye candy pictures!

[Ecomike]

How much does this thing weigh? add 20 lbs or so and there goes 1HP. And then, if this thing is pulling 50 amps consider the drag on the alternator. Result= no net gain considering you have to spend your time installing this thing. This thing is even worse than the "tornado" because it requires modification to install.
It is designed for operation only at WOT for 5 to 15 seconds only, so it pulls its power from the battery (according to the inventors web site, have you read the tech section of it yet?) and the alternator recharges the battery when it cuts off. It is like turning on the head lights and brakes for a few seconds load wise. You guys should really read their tech section. It is not full of BS, and everything they say in that section is sound hard science. I am an extreemly sceptical degreed Chemical Engineer with several DOE patents myself, and an old fart on top of it, and after reading all the tech section materials deep in there web site I was somewhat impressed.

I still think it is way overpriced, but I am a DIY engineer so I think most stuff is way overpriced anyway (LOL).

On the HP versus size issue, if it ran at 3500 rpm I would agree the diameter is too small, but these guys are cranking this thing up to 25,000 rpm which could pull that much hp (50 amps at 12 volts) in that small a space. It would need to be a precison instrument, extreemly well balanced (which cost a lot more). They list several reasons that it is designed to only run for 5 to 15 seconds at WOT. Overheating of the motor is one. Ineffectivness at other operating conditions is another (they even admit that), but it is designed only to boost peak WOT HP, nothing more. Note that it operates at WOT anywhere from 0 to max highway speed. In other words it claims it can give you a bit more HP from a dead stop at WOT take off, or help in passing.

[MudDawg]

Sorry, but I found a complete lack of substantial hard data. A 25,000 rpm Brush commutated DC motor is not a modern marvel....I built slot car engines in the late 60's that turned more rpm, its a matter of commutator phasing, brush float and the ability to withstand the centrifugal and frictional forces...and my balancing station was a pair of razor blades...I really would like to see a parts diagram to know the mechanical configuration...the fan blade (from what can be seen in one picture) is not even a air foil design, and is straight edged...all bad news for a high rpm blade....i'll bet the thing goes into cavitation at the slightest resistance to air flow....and the design of the housing is very poor as design relates to fluid flow....thats it, i'm done with this one after my parting shot.....PT Barnum was right..."there is a sucker born every minute" and "give "em what they want"....:lecture:

[Ecomike]

Sorry, but I found a complete lack of substantial hard data. A 25,000 rpm Brush commutated DC motor is not a modern marvel....I built slot car engines in the late 60's that turned more rpm, its a matter of commutator phasing, brush float and the ability to withstand the centrifugal and frictional forces...and my balancing station was a pair of razor blades...I really would like to see a parts diagram to know the mechanical configuration...the fan blade (from what can be seen in one picture) is not even a air foil design, and is straight edged...all bad news for a high rpm blade....i'll bet the thing goes into cavitation at the slightest resistance to air flow....and the design of the housing is very poor as design relates to fluid flow....thats it, i'm done with this one after my parting shot.....PT Barnum was right..."there is a sucker born every minute" and "give "em what they want"....:lecture:

The pictures leave a lot to be desired for sure. I am not sure if the picture is showing the fan blades or an intake or exhaust straightener. Agreed 25,000 rpm is not new, my 35 year old dremel tool does 30,000 rpm, but it is not a typical axial fan speed, which was my original point. I am concerned about the housing as well, I suspect there is a ridgid housing inside the housing we are seeing that the fan is enclosed in, assuming these guys are for real. All the other so called, and even real electric supercharger sites and products I have seen appear to all have major design and operating flaws and issues.

[clean96XJ]

well, if this is not actually proof but, it is civic on a dyno with an electric leaf blower addon.

http://thumbs.vidiac.com/ab544e3b-5dff-416d-9cfd-a1ad23ca9564.jpg (http://videos.streetfire.net/video/ab544e3b-5dff-416d-9cfd-a1ad23ca9564.htm)Click here to see Video (http://videos.streetfire.net/video/ab544e3b-5dff-416d-9cfd-a1ad23ca9564.htm)

[coastie124]

well, if this is not actually proof but, it is civic on a dyno with an electric leaf blower addon.

http://thumbs.vidiac.com/ab544e3b-5dff-416d-9cfd-a1ad23ca9564.jpg (http://videos.streetfire.net/video/ab544e3b-5dff-416d-9cfd-a1ad23ca9564.htm)Click here to see Video (http://videos.streetfire.net/video/ab544e3b-5dff-416d-9cfd-a1ad23ca9564.htm)

Interesting.

[Ecomike]

You know with an unlimited 120 volt wall socket power source at hand all we really need is a huge 100 psi hydraulic pump plumbed straight into the intake manifold and we could make the engine generate 900 HP output with say a 1200 hp hydraulic pump feeding the intake :laugh: :rof::D

OK, that was fun!:sunshine:

[lawsoncl]

....i'll bet the thing goes into cavitation at the slightest resistance to air flow....

Air turbines don't cavitation. Propellers cavitate - something I happen to know a lot about and have lots of experience testing.

[lawsoncl]

I can see the 5-15 seconds of intermittent boost being helpful for some racing applications where you're only hitting WOT on the straightaways. For passing power, maybe..

[Ecomike]

I can see the 5-15 seconds of intermittent boost being helpful for some racing applications where you're only hitting WOT on the straightaways. For passing power, maybe..

Agreed. One of the things I found really interesting on their site was the tech analysis and statement they made that a fan like theirs was not benefial at anything other than WOT, because of the throttle plate restriction. They said that at less than WOT, opening up the throttle plate a little more did the same thing as turning on the fan, except that the fan was less efficient than pressing the accelerator! That statement rang true as I was doing somne analysis of the physics involved, and I was having trouble with the throttle plate issue in my analysis until I read that statement which cleared it up for me.

[lawsoncl]

Yeah it doesn't make sense to generate boost while you're still deliberately restricting the engine.

[Motorvated]

throw a leaf blower on the intake HAHA

[dlarrivee]

This is so painful to read...

If electric fans hooked up to your intake actually provided some sort of performance enhancement, don't you think race cars would have them?

There is no way that some little fan is going to create enough boost to actually be worth even installing...

Hey here's an idea, why not just hook up an air compressor to your intake too! I bet that will work really well, until you back out of the driveway and realize it's plugged into the wall.

I really liked the comment about adding octane booster to go faster too... Because you know octane is like nitrous, it adds power, it doesn't protect against detonation or anything...

[Stumpalump]

http://www.micra.org.uk/showthread.php?t=2983

[MudDawg]

Air turbines don't cavitation. Propellers cavitate - something I happen to know a lot about and have lots of experience testing.

A fan and a propeller work on identical principals...the difference is the density of the fluid...air is much less dense than water...it is easier to cavitate air than water....I also am a professional that deals with fluid dynamics.

[Ecomike]

A fan and a propeller work on identical principals...the difference is the density of the fluid...air is much less dense than water...it is easier to cavitate air than water....I also am a professional that deals with fluid dynamics.

Wow, that makes three of us!

I have considerable prior experience with ultrasonic cleaner systems that use cavitation for parts cleaning. Also experience with liquid pumps and pumps systems and their problems with cavitation. Also experience with indstrial fans and blower systems designs. I have heard of parasitic fan/blower speed - frequencies for impellers that must be avoided with variable speed drive systems! I have a text book and conference papers on it here somewhere, but I don't recall if they call it cavitation, or something else, vaguely thinking they called it cavitation, but it is operationally different that caviation in a liquid. It is more related to parasitic frequencies (blade rpm and blower dimensions) that have to do harmonics, tuning, resonate frequencies that need to be avoided in the design of the fan or blower.

Curious as to the details of what you have run into on the gas phase cavitation????? Also wondering if the defination of cavitation is different between the fluid phases. Liquid cavitation is caused by the mechanical collapse of gas bubbles in a liquid. How is it defined in a single phase gas?

[jeeperjohn]

A fan and a propeller work on identical principals...the difference is the density of the fluid...air is much less dense than water...it is easier to cavitate air than water....I also am a professional that deals with fluid dynamics.
O.K. I don't have the experience that you guys have in this area but I have some questions. A propeller moving water cavitates because the reduced pressure of the water causes gas bubbles to expand and displace the water, right? So in an air moving fan, what does "cavitation" refer to? I know that if air flow to an air turbine (I am an A&P IA) is restricted, the air in the turbine drops to a lower pressure and flow stops. The air present in the turbine just starts doing very fast donuts in the housing. Ever wonder why the vaccum cleaner seems to speed up when you cover the intake? The motor actually does speed up because the density of the air in the turbine drops and places less load on the motor.

[lawsoncl]

I'm used to defining cavitation as http://www.answers.com/topic/cavitation. I've never heard it applied to non-liquids.

For JeeperJohn - basically, the local pressure drops below the vapor pressure of the water and the water essentially boils and forms small bubbles. Particulates in the water or other dissolves gases affect cavitation as well. The collapse of the bubbles produces shock and sound wave that can damage props or significantly increase the detectability of a submarine. The size of the bubbles formed and the ambient pressure (eg depth) determine the frequencies of the sound produced. When the bubbles get large enough, but still way too small to see it sounds like sizzling bacon. Get real bad and the bubbles get visible and very audible.


Here's one of our larger test platforms. https://wrc.navair-rdte.navy.mil/warfighter_enc/SUBs/LSV-2.htm

[Ecomike]

O.K. I don't have the experience that you guys have in this area but I have some questions. A propeller moving water cavitates because the reduced pressure of the water causes gas bubbles to expand and displace the water, right?

Yes, partly correct. It causes the bubble to form, and then collapse. The collapse of the bubble is what does the damage. It releases huge amounts of very localized, intense energy.

So in an air moving fan, what does "cavitation" refer to? I know that if air flow to an air turbine (I am an A&P IA) is restricted, the air in the turbine drops to a lower pressure and flow stops. The air present in the turbine just starts doing very fast donuts in the housing. Ever wonder why the vaccum cleaner seems to speed up when you cover the intake? The motor actually does speed up because the density of the air in the turbine drops and places less load on the motor.

I could not find the word cavitation used in my references that I have related to gases in fans and blowers nor in a Google search, but what I was recalling is called the "region of instability" in a fan or blower performance operating or system curve such that if a fan or blower in a duct work system is allowed to reach that area it can result in a cyclic effect called hunting that makes an acoustic noise and can cause a fan or blower to shake itself apart.

Perhaps some in industry have started calling this hunting acoustical noise cavitation as well, but so far I have not found any published references using it that way. What I may be recalling is a lecture where references were made comparing the hunting acoustical damage to caviation in liquids.

Partial Reference: Improving Fan System Performance, US DOE, Energy Efficiency & Renewable Energy, DOE/G0-102003-1294, April 2003

Hopefully MudDog will enlighten us further? :rattle:
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Lawsoncl,

Damn fine links! Most Impressive! Nice reply! I enjoyed reading and refreshing my memory on some of the details. I see now that you already answered jeeperjohn's first question (better than I did).

Ultrasonics was my first encounter with all this back in 70's. They have come a long way since them.

[lawsoncl]

I seem to recall for higher speed air fans that vortex shedding off the blades is the problem. Basically the fan blades are hitting the wakes of the preceding blades and you can get a uncontrolled feedback of the wakes causing blade vibration, exciting stronger wakes, etc.

[Ecomike]

I seem to recall for higher speed air fans that vortex shedding off the blades is the problem. Basically the fan blades are hitting the wakes of the preceding blades and you can get a uncontrolled feedback of the wakes causing blade vibration, exciting stronger wakes, etc.

Didn't the Canadians discover and solve that problem at the Mach 1 air speed with the Avro Arrow back in the 1950's. :D

[MudDawg]

In a liquid pump cavitation is the creation of a vapor bubble...in a fan, the problem is with migration of the vacuum from the back of the blade into the high pressure area in front of the blade...since the ability of the blade to generate pressure is very limited, restriction either up stream or down stream causes the vacuum to migrate. When this happens the fan will not pump....the effect is more pronounced when the inlet side is restricted...and if you look at a very high rpm straight blade fan where the blade tips approach air stall, usually near mach, the shock waves and errant tip votrices cause problems....not confuse the problems with axial fans such as the one in the device discussed....with the operational characteristics of a single inlet impeller such as is used in a turbocharger.

[jeeperjohn]

Yes, partly correct. It causes the bubble to form, and then collapse. The collapse of the bubble is what does the damage. It releases huge amounts of very localized, intense energy.



I could not find the word cavitation used in my references that I have related to gases in fans and blowers nor in a Google search, but what I was recalling is called the "region of instability" in a fan or blower performance operating or system curve such that if a fan or blower in a duct work system is allowed to reach that area it can result in a cyclic effect called hunting that makes an acoustic noise and can cause a fan or blower to shake itself apart.

Perhaps some in industry have started calling this hunting acoustical noise cavitation as well, but so far I have not found any published references using it that way. What I may be recalling is a lecture where references were made comparing the hunting acoustical damage to caviation in liquids.

Partial Reference: Improving Fan System Performance, US DOE, Energy Efficiency & Renewable Energy, DOE/G0-102003-1294, April 2003

Hopefully MudDog will enlighten us further? :rattle:
--------------------------------------
Lawsoncl,

Damn fine links! Most Impressive! Nice reply! I enjoyed reading and refreshing my memory on some of the details. I see now that you already answered jeeperjohn's first question (better than I did).

Ultrasonics was my first encounter with all this back in 70's. They have come a long way since them.

You should hear what a "compressor stall" sounds like in a gas turbine engine. It's like a machine gun firing.