Thermodynamically, the turbo is a great idea. You're scavenging thermal energy and converting it into work - great idea for THERMAL efficiency. However that doesn't translate into the efficiency we think of as mileage, since under boost, you waste a ton of gas to get the correct burn characteristics to prevent detonation and detonation is exacerbated by back-pressure. If we were just focused on not wasting energy, it'd be better if the turbine were tuned to run at idle and highway exhaust flow rates. Then it'd actually improve mileage.

Again thermodynamically, the electric blower is NOT more efficient because you're using virgin energy (which itself had to be made inefficiently though some battery charging process... and from a power plant, so on so forth) instead of scavenging what is otherwise waste. However, you are not taking anything away from the engine itself, so even if you're being more wasteful in a sense, the waste isn't coming from your precious engine power so it's more efficient for putting power to the wheels - even moreso than a turbo since turbos feed back pressure into the cylinders, as mentioned. It's like tug of war. With a turbo you're adding 3 guys to the left and 1 guy to the right but with an electric blower you're just adding 3 guys to the left and the 1 guy on the right isn't pulling. He's drinking a beer but getting paid anyway.

 

Look at it this way. Blower takes power to turn. Turbo takes power (consider the back pressure as a force against the engine working easier) and an alternator takes power. So they all are going to take power. However, an electric turbo could be used more on demand. Spool up sooner. You don’t have all the heat under the hood from extra exhaust piping. You don’t have all the extra pipes run. You don’t need a wastegate. Really don’t need a blowoff valve. May not need oil fed to it. The simplicity of it would be worth it in itself. Say you could add an easy 8psi, maybe even 10. Hell that would be like a nitrous shot. Many of us have run nitrous. The nitrous runs out. So would the batteries. However you don’t have to pay 50-60+$$$ to refill and rely on finding a place to fill it. Driving there. Filling. So why are you guys knocking it? If it can be done....why not? Anything is possible.

 

Just a few years ago, if you were told that an electric car would outrun a 9 second car, most people would have scoffed at the idea. The Tesla roadster runs high 8’s and it’ll only get faster. Things are advancing. The experimental battery technology being tested is way better than the lithium we have currently. It recharges very fast and holds more energy. Just wait. This kind of stuff will be a reality.

 

I'm not knocking the idea of it. Just the notion that it's some how less wasteful from an eco perspective. And sort of, to some extent knocking it for taking away the turbine and thus wasting the exhaust energy. My experience with electrical stuff of this nature is limited to what's used in mining and factories for automation for the most part and what I saw and worked with on a electric car project in college. We used a motor from a forklift and started off with something like 40 car batteries to work with until we got a donation of lithium batteries. They did a snowmobile too using a **** ton of dewalt batteries mounted around the tunnel.

But lets say this thing works, we know it can work and make boost with the right motor and controllers and if you got something like a big *** battery out of a tesla or a prius you could carry enough juice to power it for a while. But then we're talking about adding all that weight because from my experience, electric motors, batteries and ought and double ought cable are heavy as hell, like comparable to ICE parts when all added up. So how many pounds of battery are we talking about adding in here? I can't imagine one or two car batteries being enough for anything other than a blip of it...3min-5min?

How much power is lost from the weight added? Is your dude off to the side who is drinking beer instead of pulling against the other three guys actually just a lard *** weighing down the sled? is he any less of a burden than the back pressure? You have to carry those batteries around while the thing is turned off too...

 

If you have a look at the video in the first post, you can see the batteries I'm using for yourself. I would estimate them at about 1 lb each and I'm using 2 just for the hell of it, even though their in parallel. I should get about a minute of solid use from each battery so if I wanted an hour of use, that'd be 60 batteries in parallel. I weigh 120 lbs. I'm a skinny ************ so the extra 60 lbs would essentially be free weight for me lol. But honestly, given that most of us don't drive around at WOT all the time, the 5 batteries I own ought to be enough for my needs between charges.

If you used lead-acid, sure it'd be a ton of extra weight, especially because you'd have to have extra batteries just to get the voltage right but why do that when LiPos are so much lighter and more flexible with voltage and form factor? I can lift the turbo with 1 hand easily so honestly, the whole damn thing including the 8 AWG wire weighs no more than your average procharger for sure.

...yeah 8AWG is just fine. Might lose 2/10ths of a volt maybe and the temperature might rise 5 degrees but the controller is like 12 AWG and it was designed to pass 300 amps. It's fine.

 

Certainly an interesting idea. Looking forward to see how it pans out.

 

28vdc 300amp 6ph stuff for me is all #4 between starter and box, I would look into your wiring sizing choice.

 

I know I'm undersized on the wiring. I mean the charts definitely say so. However there's a nifty calculator I found somewhere that calculates line resistance based on diameter and length and also predicts temperature rise. The charts are really designed for continuous use and so they don't apply to momentary use as much. As long as you don't set fire to the car or lose a ton of voltage, any wire can carry any current in theory. I've found that despite the logic published by IEEE and such, various manufacturers choose different gauge wire for the same application. For example, my motor has thick-*** cable that looks like 00 or bigger but the battery has something that looks like 10AWG even though it's 5000maH and 120C rated and then the mamba controller has the thinnest wire of all and looks like 12AWG. Yet they all seem to work just fine for the <1min tests I put them through. If I put a FLIR on the whole scene I'm sure I'd see heat coming from the thinner sections of wire but my multi-meter gives me good voltage readings and nothing feels hot to the touch so... eh... maybe I can get away with it. For my wiring going to the trunk I have pretty thick wire which I sized more than a year ago and since that's the longest I figure that's what really matters. The thin stuff is only a few inches long.

 

The problem is the added inductance with a thinner gauge wire. It doesn't play nice with large switching currents and leads to suboptimal results.

 

Hmm... I'm going to have to look into that a bit. Thanks for the tip.

 

What about the restriction on the intake when the compressor is not powered? have you thought about a by pass with a valve or something to unblock it when its not in use?

 

Lol, you should check out the video. I go into that in detail. It's not an elegant solution but it should work in principle.

 

That's not a bad off the shelve solution but i would wack one with a hammer a little. But those PVC back flow valves, the hinge on them is kind of small and just plastic it self. That would make me worry if it lets go. A pea size piece of PVC down the throat of a 6.2 probably isn't a great diet for it. The only other things i can think of cost a lot more, like vacuum and boost activated stainless valves a lot of us use. But they're about $125 a pop and you would need 2. Also slower than a flapper. I skipped that whole bit last time because i though a mad max commercial was playing and jumped to far ahead lol.

 

It sounds like you actually know the correct hardware to use in this situation. As you guessed, what I picked is basically house plumbing for water drainage. If you have a suggestion for something that would do a more reliable job I'm happy to take your advice. Those valves you mentioned sound awkward, even if I don't know exactly how they work.

 

https://cdn.shopify.com/s/files/1/09...g?v=1488400775

This is what they look like, they come in every size and the actuators can be vacuum or boost driven (diaphragm and spring inside) But they take about 1sec to fully open or close. There are electric versions too, you might be able to swap the motor out on one of those with a high torque/faster unit as well. They are mostly used as exhaust valve cutouts. I think the ideal unit would be a replica of the PVC one made out of aluminum, but geez that would be a task. You might even be able to take some drive by wire throttle bodies and wire them up to the same switch for the turbo, drive by wire TB's react pretty quick...

 

Always "almost" what you need, eh?

Any of those suggestions would work but all seem to have some sort of trade-off. In my case, I'm trading durability for something that works by itself without any help. In the other case I'd be trading simplicity of design (possible malfunction) for some robustness and no chance of ingesting parts. I'm not sure there's a clear cut winner but I'll have a look at these valves and see if one lends itself to this application. Thanks for bringing it to my attention.

 

How about an enclosed cone filter that's positioned after the merge so that it functions as the air filter for both systems? It could break then and you would still be safe.

https://www.forgemotorsport.co.uk/In...uct--1075.html

This one is for a Golf, but its just the first one I could google. They make just the can part with the filter without the rest of the kit parts.

I built my turbo car from a pile of junk yard trash...i could sit and brain storm this type of **** all day, its my jam.

 

That's a thought. Actually I mulled over something similar except instead of air filter, it was MAF screen. Either way it's an extra piece of insurance that I would probably want to have.

 

Any update?

 

Normally I would have posted progress weeks ago but this whole Covid 19 thing has hampered my schedule. There's fabrication I need to have done outside that is impossible at the moment. I'm working with my mechanics to expedite as much as possible. In the meantime, I'm working mostly on software, which is a bit boring to report on, unless you're interested in that sort of thing. With any luck, I'll be able to post an update before May is out, as I don't think we'll be in lockdown that long... at least I hope we aren't.

On second thought.. I do have a small update. I got rid of the batteries you see in my video and replaced them with 2 x 7S Lipos so my voltage has just jumped from 22.2 to 25.9 nominal. This was prudent to take full advantage of the available headroom my controller has to offer (it suffers damage at 31V and when fully charged a 7S LiPo puts out 29.4V). So in other words, for no penalty, I have an extra 15% or so available power for the blower, which is always a good thing.