911rudy

If you go to www.electricsupercharger.com you will see a small inline electric supercharger the spools up in 1/10 of a second to 25,000 rpm and can produce up to one bar of boost. It seems like this unit could be used in conjunction with the turbo on the 930 to reduce turbo lag. It could be regulated to diminish its boost as the turbo incresaed its boost. It is only $300 and fits between the air filter and the intake. I have e-mailed the company and asked if they have ever used this blower for such a purpose. I will let you all know when I hear from them. What do you guys think?
Rudy

jhunt@huntinter

You are wasting your time.

slownrusty

Garbage in....garbage out..

Lag....with the new family of turbos available...there is virtually a seamless transition between on and off boost. What turbo are you running.

I see VERY minimal lag on my car, these cars like to breathe too..so having a free flow exhaust \ header combo is VERY optimal.

Yasin

JBH

This is why you took physics in HS. It takes hp to compress a gas. Now, what do you think is the hp rating of that electric motor and how much air do you think it will move at 1 bar?

911rudy

Sorry,
I left the decimal point out. It should be .1 bar not 1 bar. I have a K27 HF and get full boost at about 2500 rpm. I figured if I could drop it by 500 rpm for $300 it would be worth it. I also have headers and a B&B IC. These people also use the blower for raceing brake coolers. I used to fly Airbus 310 and they did the same thing and you could see the temps drop right before your eyes.
If you go to their web site they have some interesting data concerning air scoops and compares them to their blower. I think it said that at 180 mph a hood scoop creates .86/lb psi. If you could get 1 psi while stopped it would seem to be a positive. They also mention HP cost of mechanical blowers at 10 to 20 hp for small blowers. They are producing 15 psi however. This motor draws 58 - 74 amps depending on power and work only on WOT. I've never experienced off idle turbo power in any car with out lag and probably never will because of the cost of a twin, but if I can get any help for a reasonable $ I will try it. If I have any luck I will pass it on.
Rudy

Geoffrey

Don't forget that after .1bar the unit becomes a restriction in the inlet stream which will cost you...

nathanUK '81 930 G50

Would be great if someone tried it.
Would have to dyno before and after though
I would want it on all the time though not just at wide open throttle.

How many engine rpm is needed for the hfs turbo to make 0.1 bar without this electric blower ?

JBH

Ahhh...that decimal point makes a big difference, but I think Geoffrey's point is still an issue.

By knowing the displacement of your engine and the rpm, you can calculate the volume of air you have to move through your engine - a four stroke engine takes in air in every two revolutions. At 2500rpm with no boost, it is something like 88 cuft/min for a 3.3L engine. One bar boost doubles that number and going to 5000 rpm doubles it again. So you can see it won't take long before that in-line device becomes a restrictor.

911rudy

I just got an e-mail from the Eram techie and here is what he said. First, it cannot be a restriction in the intake system since it flows more cubic feet/min than the 3.3 at full throttle needs and when it is not operating it is over three inches in diameter and is an axial flow fan which is the same as a one stage jet engine fan. The blower produces 800 cfm. Since there are no stators to increase pressure there is no drag. Second, There would be a reduction of about 300 rpm to reach full boost on the 3.3. Since it only operates at WOT it would spool up in 1/10 of a second and raise pressure in the lower rpm range but would do no good at full turbo boost. This reduction in turbo lag is caused by a more rapid build up of exhaust gas produced by the denser air charge at WOT. I have offered to install one on my 930 if I can return it if there is not turbo lag reduction. I will let you know his answer. If it works it is one cheap way to drop 300 rpm to full boost.
Rudy

jhunt@huntinter

have you searched this forum for past eram threads? This topic has come up before... and discussed at length.

nathanUK '81 930 G50

One thing is for sure, I would want this fan fitted BEFORE the air filter, just in case it came apart. I wouldn't want my turbo, IC or engine chewing up this electric fan.

911rudy

jhunt,
Thanks for the idea to search the forum. There is a great debate on the subject on the 928 forum. Their problem besides predjudice and bad data is that they are trying to get rear wheel HP from the device. All I want is to drop spool up time or rpm. The science is sound and if you don't believe me go to the 928 forum and click on the leafblower vidieo! I think its on the 8th or 9th page. One source of debate is the electrical requirements and the drain on the battery. Remember that the Eram is only used at WOT and not very often. Even though it uses up to 60 amps, it does so only for a few seconds and then the rest of the time the battery can recharged eg; idle, etc.
You have to read these letters to see how angry some people become just over an idea!
Rudy

mark kibort

yes it does. the HP rating of the eRAM electric motor is in the neighborhood of 1hp. (850watts input) we are talking only .068bar change in pressure. (ie 1psi)

Also, the eRAM pumps out more than 800cfm as Rudy has mentioned, and when not engergized, as it only runs by design at WOT, can still flow as much as a 3" straight pipe! (measured at SEMA on a flow bench) however, that point is moot , due to the only time that the eRAM could be a restriction would be at WOT, yet it flows near 2 X the flow as a 5 liter engine would at 6000rpm. this is where the pressure comes from .

We have also done extensive testing on air boxes, measureing and confirming expected ram pressures and vacuum under WOT. generally, we see .7-.8 psi vacuum in an air box, behind the air filter. RAM pressure calcualtes almost exactly to .08psi at 80mph and .36psi at 160mph. we measure close to .1psi at 100mph+ . With the eRAM engaged, any vacuum is relieved to the level of a positive 1psi net change. this is 6% and thats what the product does.

Now, as far as reducing turbo lag. Hmmmm, well, if you burn 6% more air and fuel at the lower RPMs, there will be that extra mass flow to spool up the turbo. dont know if will be a noticable difference.

Just thought i would chime in, hope you guys dont mind

MK

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mark kibort

Yes, one bar boost generally is equivilant to doubling your displacement, so as far as a restriction, sure once you get the boost high enough to equal the flow rates of a 6-7 liter engine, sure, i could be a restriction, but even then, probably not. remember that the impeller is driven by an electric motor and has a pretty high rotor blade pitch. the faster air moves through it, the less the angle of attack of the air relative to the blade pitch. what this means is that the fan can then speed up with the same input power, as long as the electric motor timing can handle the increased rpms. (which it generally can)

the device (the eRAM) is designed for about 300hp flywheel and less. thats the bottom line. very easy to check too. we use a Sunx pressure sensor which measures down to resolutions of .01psi and within 1/1000 of a second. (very accurate.) we can attach to any air box, and see what your pressure drop is. generally, the eRAM can relieve some of this vacuum , and that results in small gains.

MK

Sameer

Interesting but what are the disadvantages of this setup?