What kind are you using? I think centrifugal is the best chance to move enough cfm.

 

the E-RAM! you're awesome dave! someone who finally could end this debate.. if I remember correctly, these electric chargers give a good output only for short bursts.. maybe you should try the leaf blower too! just kidding.. well maybe not:crazyeyes

 

hes using one of those electric thigamajigs.....i think it produces like 2 psi.
i dont think u need to upgrade ur alternator fwiw. the additional load on the alternator will no effects on ur driveline.
im not sure the throttle body will be much benefit in conjunction with this thing. at 2 psi, which isnt much, all the bigger throttle body will do is reduce air velocity. try it without and then with the t/b.
interesting. keep us posted.

 

I can't even believe you guys would seriously consider one of these. Complete waste of money.

 

Dave the TrailBlazer!
You go, (girl)friend!

 

I can't even believe you guys would seriously consider one of these. Complete waste of money.

Hey Rob, thanks for the comment. My finances aren't exactly on a tight budget, and I would never seriously consider buying an Audi either, but that's just me.

 

:up: Dave. It's good to see someone actually testing these types of products. I am tired of seeing the same BS of people swearing by them because of an imaginary seat of the pants feel or dissing them based on pure speculation.

 

Keep the pioneer spirit Dave! :up:

Crazy question... if the load of the alternator is cause for concern, could it be measured on the dyno by doing some runs with all of the electrics going full tilt or putting in a depleted battery?

 

Way to go, Dave. Love your spirit! Look forward to the results.:clap:

 

Hey Rob, thanks for the comment. My finances aren't exactly on a tight budget, and I would never seriously consider buying an Audi either, but that's just me.

What does what my old car have to do with this? I'm just trying to save you the hassle of wasting your money.

 

Dave,

I think it's cool that you're open to trying new things with your car. I'm looking forward to seeing the results you get with the electric supercharger. However, what really gets my attention is the 202 hp NA dyno run. Did I miss your post on that one?

Thanks,
John

 

Dave,

I think it's cool that you're open to trying new things with your car. I'm looking forward to seeing the results you get with the electric supercharger. However, what really gets my attention is the 202 hp NA dyno run. Did I miss your post on that one?

Thanks,
John

That's actually a run I had done last Thursday, ambient was in the 40s which helped...some mods to get there: FF CAI, QuickSilver, Arqray decat, MWR headers, some ECU stuff that I'll be posting about later. 202 is a good number, but for some really impressive NA HP see Frank's (ronin) postings.

 

FAQ

12. Does the e-Ram put a large drain on the alternator?

Answer: No, the max current draw is 60 amps for the e-RAM, and 120 amps for the Super e-RAM. This is as much as a high powered stereo, headlights, electric radiator cooling fan, or the starter motor on your car. Most car batteries with over 200 cold-cranking amps can handle draws of over 100 amps while the engine is running with no problems. We have even tested the e-RAM and Super e-RAM on motorcycle electrical systems with no problems. The e-RAM generates up to 15 hp gain from drawing over 1hp (831watts) directly from the battery. This has been verified on the dyno and with Volt Meters and Amp Meters. Charging systems work base on voltage drop of the battery, so the burden of the current draw really depends on the condition of your battery. Most batteries in good condition see very little voltage drop for short duration current draws of 60 or 120 amps for 10 to 15 seconds (full-throttle operation of e-RAM).

6hp, 5T per the dyno below for whatever engine they tested.

Dyno Chart

Curious about the thingie. Not quite sure I would buy it though.

 

Let's calculate!

What it comes down to - the alternator needs to provide enough power to move enough air to create whatever the claimed pressure differential is at whatever flow rate is being demanded at a particular RPM.

Assuming you want to do this around redline (8000 rpm), then one would need to move at least 1.8l (engine displacement) * 8000 (revs/minute) * 0.5 (number of complete cycles per crank revolution for a 4 cylinder engine) = 7200 liters/minute or about 254 cfm.

To convert this to power required, we need a pressure difference. For the back of this envelope, let's say it's 1psi, and the compressor is 75% efficient thermodynamically (unlikely to be that high, but why not).

Power required = pressure difference * flow rate / efficiency.

HP = CFM * psi / (229 (unit conversion constant) * efficiency) = 254 * 1 / (0.75*229) = 1.47 HP

Now, 1.47 HP = 1096 Watts. Given that we have about 14V electrical systems, that means that a 100% efficient electric motor will suck 78 amps. Given that no electric motor is 100% efficient, it'll really be more if it worked as advertised at 8000 rpm.

(OK , I shoulda looked on the site - they actually claim a 120 amp (~2.2HP) electric motor for 1.7 psi - we're in the ballpark.)

Since the alternator is going to see the demand even with the way they are wiring it up on the website, I'd expect to see some driveline loss in the neighborhood of a HP or two. (The alternator won't supply all the current, but the alternator isn't 100% efficient, either).

Also, this tells me that this motor wouldn't be suitable for a road-race driven car, either (i.e., long periods of WOT will severly drain the battery).

ed

 

What it comes down to - the alternator needs to provide enough power to move enough air to create whatever the claimed pressure differential is at whatever flow rate is being demanded at a particular RPM.

Assuming you want to do this around redline (8000 rpm), then one would need to move at least 1.8l (engine displacement) * 8000 (revs/minute) * 0.5 (number of complete cycles per crank revolution for a 4 cylinder engine) = 7200 liters/minute or about 254 cfm.

To convert this to power required, we need a pressure difference. For the back of this envelope, let's say it's 1psi, and the compressor is 75% efficient thermodynamically (unlikely to be that high, but why not).

Power required = pressure difference * flow rate / efficiency.

HP = CFM * psi / (229 (unit conversion constant) * efficiency) = 254 * 1 / (0.75*229) = 1.47 HP

Now, 1.47 HP = 1096 Watts. Given that we have about 14V electrical systems, that means that a 100% efficient electric motor will suck 78 amps. Given that no electric motor is 100% efficient, it'll really be more if it worked as advertised at 8000 rpm.

(OK , I shoulda looked on the site - they actually claim a 120 amp (~2.2HP) electric motor for 1.7 psi - we're in the ballpark.)

Since the alternator is going to see the demand even with the way they are wiring it up on the website, I'd expect to see some driveline loss in the neighborhood of a HP or two. (The alternator won't supply all the current, but the alternator isn't 100% efficient, either).

Also, this tells me that this motor wouldn't be suitable for a road-race driven car, either (i.e., long periods of WOT will severly drain the battery).

ed

Wow Ed, thanks for the numbers. I knew some of you engineering types would ring in. Agreed, with that draw, extended road racing is not an option - not after that anyway. I think it would also be interesting to dyno with the on-board battery, then try with an external...that should represent the alternator loss? Even if all of this ends up only as a science project, at least I'll have learned along the way. Then again if I can get another 6hp for $600, nothing wrong with that either.

 

I think it would also be interesting to dyno with the on-board battery, then try with an external...that should represent the alternator loss?

The more I think about it, I suspect the difference in repeatability of the dyno test may exceed the extent of the alternator load. But you never know until you try.

 

The more I think about it, I suspect the difference in repeatability of the dyno test may exceed the extent of the alternator load. But you never know until you try.

Probably so. For some reason, I'm always nervous watching my dyno pulls anyway. I've seen those mpegs of straps breaking and cars launching through the side of the building.

 

These things have been proven up and down that they are useless. I cannot cite any sources, but i would do a quick internet search and i am sure you will find alot of information showing that this product does nothing but potentially detract power and add more parts to fail.

If 600 dollars is really nothing, i suggest giving it to someone who can use it, rather than some ebay scammer...

 

Way to trail blaze Dave!!!:up:

Stan and I had a discussion some time ago about the alternator's output during spirited driving. We never got around to testing it.

I would suggest you get a second battery and run the SC off of that first rather than the alternator. See if it makes a difference there. If it does, then you could always hook it up to your system with the second battery in Parallel or just with the current system with a higher output alternator.

 

Dave the TrailBlazer!
You go, (girl)friend!

c'mon man you're an electrical engineer... give better insight then that!

I also side with the "no power will be found" crowd. I have an engineering degree also but I've been proven wrong before. You could buy a decent nitrous setup for $600...

 

c'mon man you're an electrical engineer... give better insight then that!

I also side with the "no power will be found" crowd. I have an engineering degree also but I've been proven wrong before. You could buy a decent nitrous setup for $600...

He already has the nitrous setup.

 

Where is this 202hp n/a dyno graph?

 

dave, have you looked a the thomas knight ones ?

http://www.boosthead.com/home.php

 

c'mon man you're an electrical engineer... give better insight then that!

I would if I had the insight and/or time.
I too I'm interested in "electrical supercharging" but I don't know much about it. It seems that it is in its infancy and that further advances need to be made in materials and efficiency in order to even be comparable to an exhaust driven turbo.
Maybe a combination electric turbo (at low rpm) where the exhaust driven turbo doesn't have enough boost and then it gives way to the exhaust driven turbo for high RPM and boost.
That should give us a nice flat torque curve with no typical turbo ON/OFF response. But, it would also be expensive, unreliable and complicated.

Let's see what Dave sees and we'll know for at least this generation of electric superchargers...

 

dave, have you looked a the thomas knight ones ?

http://www.boosthead.com/home.php

Hey charlie, how's your battle with the flu coming? I've not looked at these yet, but they claim up to 6psi That's pretty bold. Just skimming the site, the price is considerably higher (beyond my beta test limits) and storage batteries are involved. Have you had any experience, or know of someone who has?