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teknicalissue
10+ Year Contributor
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- Oct 18, 2010
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Front Royal,
Virginia
Sorry I've been away guys! Work has got me pretty busy! That and for some reason.. I'm not getting emails on new posts for this thread..
This has me thinking.. would the 35lb/min be different closer to the TB than further away? I'm trying to justify the 35 lb/min. On top of that.. How do multiple turbo's work as far as CFM work? wouldn't compressing already compressed air create more heat? would having a natural 14b turbo and an electric 20g turbo produce combined amounts of CFM? there has to be a gotcha when involving multiple turbo's correct? I'm leaning towards a positive gotcha, but I've been wrong before
I'm going to have to think of a cooling solution for the air coming out of the electric turbo.. thinking about this though; the air isn't passing through an exhaust... hmmm.... Sounds to me that cooling the air coming out is the best way of maintaining efficiency/higher cfm.
what would you recommend? Should we stick with the gears? or go with the belt system and give it a try. I'm actually in the process of printing out the belt drive transmission system:
agreed; I think at this point; the limitation is batteries. we could increase the amp hours by grabbing another set of batteries but then that would be subject those willing to pay to play. I wish there were better batteries
Will be looking in to a DIY Peltier junction intercooler.. Sounds like something that could help; specially if the e-turbo is mounted close to the manifold.
yes. But to add to this which is why I'm not a big LiPo guy; they are also fairly dangerous if not charged right or punctured. This would make me afraid to wreck my car.
Keep in mind that when I say a 20G, I'm talking about a 20G compressor and wheel; I'm creating my own CHRA from scratch which will support the belt driven system.
Awesome Math is awesome. I guess it's fair to say that batteries are the biggest hindrance to electrical components. Either go with a weaker motor which won't give power or go with less time on a more powerful motor... Also; I did research on multiple motors and I came up with them not being able to work nicely together. Essentially; each motor would be on their own ESC and have their own timing. At most, a 20% increase in wattage was recorded for two of the same 5kw motors (spoke to the company about this). Something in the timing with the motors eventually ends up with one motor dragging the other one at certain points of a burst.
I'll look in to those; I'm hoping price isn't a problem honestly. I think I'm okay with the electrical motor being $600. I wouldn't be able to justify batteries for that price unless I know this thing will be a beast.
I've been doing some thinking and I think we need to reflect about the goals and purpose of the e-charger.
The way I envision this project is to provide boost at the lower end of the spectrum until a larger turbo can pick up the slack (if the larger turbo is there. If it's not; I expect PSI to drop off as the RPM's increase). The e-charger should provide boost between 1k - 4.5k on the RPM band and shouldn't be expected to sustain boost at above those RPMS.
So in essence; I think we've (and by we've I mean I) gradually changed our vision for this E-charger to provide maximum boost throughout the powerband and completely forgot that this is supposed to act like a supercharger/nitrous shot combination hybrid thing where it only provides incredible amounts of power below half of the available power band for a larger turbo to pick up.
Is this true? and if so; would any of the calculations (CFM/HP) change considering that our goal is not max boost till redline? Does this change the scope of the project and what motors/batteries be required for the project?
I was reading over some notes and realized that my goals/purpose for this project changed So I wanted to know if I've just been out of the loop for a while or do we need to rethink and make changes to some of the stuff we've decided. To make things simple; this is what I've jotted down as far as equipment is concerned:
- Belt driven system for more reliability and maintainability
- 25.5KW motor for HP needed to maintain boost at certain CFM's
- Batteries powerful enough to work with 25.5KW motor @ 300A drain.
-20G compressor cover
-20G compressor wheel 6 blade billet
- ESC powerful enough to power 25.5KW motor
This is what I have on my list as far as hardware. Is this overkill as far as meeting the original goal of providing large amounts of boost in the lower end of the power band?
On a side note; This doesn't mean I will avoid thinking about direct drive applications, full power band e-chargers, cvt e-charger, and E-Assist solutions. I just would love to finish the original goal first
Hmm.. you're right. It adds complexity but for something this powerful.. It's definitely needed. On top of that; I can create software that will give people control of how much Approximate PSI they want the electrical motor to generate at a given RPM. taping in to the RPM wire shouldn't be that hard right? If I remember correctly; It pulsates to give the rpm.You may be going for a little overkill here.
While that motor will provide the power at 7000 RPM engine speed, it will definitely have to be throttled back at anything less than around 6000 RPM. You may hit 50 psi at low engine RPM if the compressor wheel doesn't choke first. You'll have to do this with programing as there is no wastegate to control boost. You'll need an RPM sensor, not just a TPS.
At 45 lb/min, you're right on the 60% compressor efficiency line. Allowing for the heat of compression:
45 lb/min @ 2:1 PR @ 60% eff = 50.16 HP
35 lb/min @ 1.75:1 PR @ 60% eff = 30.8 HP
1.75 PR = 12 psi
25.5 KW X .9 eff / 746 =30.76 HP
The motor RPM will probably drop until the motor HP equals the required HP.
This has me thinking.. would the 35lb/min be different closer to the TB than further away? I'm trying to justify the 35 lb/min. On top of that.. How do multiple turbo's work as far as CFM work? wouldn't compressing already compressed air create more heat? would having a natural 14b turbo and an electric 20g turbo produce combined amounts of CFM? there has to be a gotcha when involving multiple turbo's correct? I'm leaning towards a positive gotcha, but I've been wrong before
I'm going to have to think of a cooling solution for the air coming out of the electric turbo.. thinking about this though; the air isn't passing through an exhaust... hmmm.... Sounds to me that cooling the air coming out is the best way of maintaining efficiency/higher cfm.
I can't see a 9mm wide belt being able to transmit 30 HP. Belts, in general, do not like high RPM.
what would you recommend? Should we stick with the gears? or go with the belt system and give it a try. I'm actually in the process of printing out the belt drive transmission system:
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Electric motors are not rated in amp/hrs, batteries are. That motor will be pulling 300 amps constantly...but you're right, the batteries will last 1 minute @ 60C discharge rate. At a max 15C recharge rate, it will take 4 hours to recharge. Not very practical.
Jim
agreed; I think at this point; the limitation is batteries. we could increase the amp hours by grabbing another set of batteries but then that would be subject those willing to pay to play. I wish there were better batteries
Ok don't shred me on this one is hypothetical and I'll research it later on but what about just using 4 or 5 agm batteries, hooked up in series for amp boosting, then use a high powered voltage amp? In that book I have they used 5 lead acid batteries in the trunk to power a electric supercharger and a Peltier junction intercooler, which the junction also required significant power.
Will be looking in to a DIY Peltier junction intercooler.. Sounds like something that could help; specially if the e-turbo is mounted close to the manifold.
Li-pos are more efficient and lighter and can discharge enough but they are expensive so AGM might be something to at least consider, but I think I've heard about that too somewhere.
yes. But to add to this which is why I'm not a big LiPo guy; they are also fairly dangerous if not charged right or punctured. This would make me afraid to wreck my car.
Exactly, cost being the issue as it seems like the motor will cost a good amount on its own. And each person can upgrade to any type they want. One more thing is maybe you should consider how you'll package the charger and intercooler, piping, room for cooling ducts, and lubrication supply demands. A 20g is designed to work on pressurized oil, this can help dampen harmonic vibrations. Not sure if a self contained system would work right, but maybe that was just for the gears. One good thing is the heavy turbine wheel won't be slowing the spool down anymore, and that's probably gonna help the required horsepower to drive just the compressor wheel, right? Or is that already taken into account?
Keep in mind that when I say a 20G, I'm talking about a 20G compressor and wheel; I'm creating my own CHRA from scratch which will support the belt driven system.
Lead acid batteries may not be the best solution. You would need 7 batteries wired in series to reach 85 volts.
The amp/hour ratings of almost all auto batteries are rated at a 20 hour discharge rate. The higher the discharge rate, the lower the amp/hour rate becomes. This is known as Peukert's Law.
http://all-about-lead-acid-batterie...amentals/peukerts-law-and-exponent-explained/
Most auto batteries are rated between 80 and 100 amp/hours. At a 300 amp discharge rate, you would drain those 7 batteries in minutes.
k = Peukerts exponent
k = 1.3 - 1.6 for lead acid
k = 1.2 - 1.3 for AGM
k = 1.09 for lithium ion
At 300 amps discharge rate:
100 amp/hour battery = 5.86 minutes @ 1.3k
100 amp/hour battery = 3.89 minutes @ 1.4k
My Advance Auto "Silver" battery is rated at 85 amp/hours.
85 amp/hours = 4.7 minutes @ 1.3k
85 amp/hours = 3.1 minutes @ 1.4k
An Odyssey PC680 battery is rated at 16 amp/hours.
16 amp/hours = 32.44 seconds @ 1.3k
With the batteries wired in series, the voltage goes up but the amp/hour rating remains the same.
The batteries must be wired in parallel to charge them off the stock alternator. The stock alternator is rated at 75 amps. This 75 amps divided between 7 batteries will take approx. 10 hours to recharge the batteries.
Jim
Awesome Math is awesome. I guess it's fair to say that batteries are the biggest hindrance to electrical components. Either go with a weaker motor which won't give power or go with less time on a more powerful motor... Also; I did research on multiple motors and I came up with them not being able to work nicely together. Essentially; each motor would be on their own ESC and have their own timing. At most, a 20% increase in wattage was recorded for two of the same 5kw motors (spoke to the company about this). Something in the timing with the motors eventually ends up with one motor dragging the other one at certain points of a burst.
I think hat is a tad to long. So Lithium Ion or polymer or maybe Lithium Iron phosphate?
I'll look in to those; I'm hoping price isn't a problem honestly. I think I'm okay with the electrical motor being $600. I wouldn't be able to justify batteries for that price unless I know this thing will be a beast.
I've been doing some thinking and I think we need to reflect about the goals and purpose of the e-charger.
The way I envision this project is to provide boost at the lower end of the spectrum until a larger turbo can pick up the slack (if the larger turbo is there. If it's not; I expect PSI to drop off as the RPM's increase). The e-charger should provide boost between 1k - 4.5k on the RPM band and shouldn't be expected to sustain boost at above those RPMS.
So in essence; I think we've (and by we've I mean I) gradually changed our vision for this E-charger to provide maximum boost throughout the powerband and completely forgot that this is supposed to act like a supercharger/nitrous shot combination hybrid thing where it only provides incredible amounts of power below half of the available power band for a larger turbo to pick up.
Is this true? and if so; would any of the calculations (CFM/HP) change considering that our goal is not max boost till redline? Does this change the scope of the project and what motors/batteries be required for the project?
I was reading over some notes and realized that my goals/purpose for this project changed So I wanted to know if I've just been out of the loop for a while or do we need to rethink and make changes to some of the stuff we've decided. To make things simple; this is what I've jotted down as far as equipment is concerned:
- Belt driven system for more reliability and maintainability
- 25.5KW motor for HP needed to maintain boost at certain CFM's
- Batteries powerful enough to work with 25.5KW motor @ 300A drain.
-20G compressor cover
-20G compressor wheel 6 blade billet
- ESC powerful enough to power 25.5KW motor
This is what I have on my list as far as hardware. Is this overkill as far as meeting the original goal of providing large amounts of boost in the lower end of the power band?
On a side note; This doesn't mean I will avoid thinking about direct drive applications, full power band e-chargers, cvt e-charger, and E-Assist solutions. I just would love to finish the original goal first