poor mans turbo

[amctmg]

Would it be possible to take a weed whacker motor and mount it to a air pump or some junkyard turbo, Hook it up somehow and have any kind of useable boost

any thoughts?

[IIx 03 EP xII]

one thought came to my mind: GHETTTOOOO!!!! but hey, to each his own i guess??!!

[esmith13]

you need more than an air pump. you need an air machine that is capable of compressing air into pressurized quantities. Anything that dosen't compress air is no different than a ram air intake would be in reality. The air must have a higher pressure that the ambient air pressure or it's not forced induction.

And why would you use a weed wacker motor to run it? Think about a supercharger... it's an air compressor that's spun by the car's motor... If by some miricle you did a DIY setup - you should still drive it by the car motor belt. Why add another independant motor??

Oh, and it would be a poor man's Supercharger not a turbo. A turbo always works off of the exhaust flow for power...

Eric

[ep_nezay]

LoL, only if the weed wacker can force the air pump to give lbs. P er S quared I inch of air.

[ApexinSi]

buy a generic turbo.. eagle talon even

[specialblend154]

wow... i cant believe i clicked on this thread

[smilla0]

The weed whacker motor will work as long as the motor puts out 15+ horsepower. That's a big whacker! With only 1-2 hp, it would produce less than 1 psi of boost at mid and high RPMs. With about 15hp-20hp, it will produce boost on the order of a JRSC. This does have several advantages as that 15+ hp will not be drained from the main engine. Even a turbo causes substantial restriction on the exhaust. As long as you crank up the blower motor ahead of time, you'll have instanteous boost. I'm not sure if this would be emissions legal or not. You could always pull the blower motor out of there if you go for inspection.

Here's an idea: Buy a simple D series motor (80 some hp should be plenty, don't feel like doing the calculations right now). Put that engine in the trunk and attach a monster centrifugal compressor to the main crank. Keep the AC compressor on, and put the AC evaporator in the output of the centrifugal to act as a super intercooler. Then you'll really be able to crank up the boost and keep a high compression ratio! I'd expect 800hp easy. Hell, you can use the secondary motor's electrical generator and accessories, and you can remove those from your main engine to reduce that parasitic drag and inertia as well! The only problem now is that you'll have an awful lot of weight in the rear end and you'll get no traction in the front wheels. :Sigh: Perhaps a two motor Si would work better. I'd love to see that!

But if you really want to save money, sell your Si and buy an 80's mustang or monte carlo and mod that instead. Modding the Si is expensive and there's few ways around it short of nitrous. Believe me, I've wracked my brain trying to find ways to do it, and I'm sure thousands of others have tried, too. Maybe you could try the above idea in a mustang, because the weight in the rear would actually help traction in that case. The low end torque would be phenomenal :D

BTW, you could use an air pump like an Eaton blower, but a centrifugal is better because it will produce the same boost pressure regardless of the main engine's crank speed, as long as the blower motor's speed remains constant. You'd need a speed governor for this, because as the main engine starts sucking in more air, it will cause a greater load on the blower motor because it has to compress more air, and it will want to slow down. Plus centrifugals flow much more air than Eaton blowers.

Hey, it's a fun thought experiment :)

[amctmg]

Well I bought a turbo at the salvage yard. Its off of an audi or vw and I want to hook it up and I have a plan but I need to know what rpm I am aiming for to get boost out of it. I will probably use either a electric motor or nitro motor from an r/c car to spin it. Maybe even a car starter motor.

[smilla0]

The RPM depends on the size of the compressor impeller and the geometry of the impeller and the amount of boost. For 1 psi of boost on a small OEM turbo as in a Volkswagen 1.8T figure around 20-40,000 RPM. For 6 psi figure around 75,000 RPM. These numbers are from a Garrett T3. I don't know what VW uses. An old V8 starter motor could give you some decent power, but the starter motor will have to be greatly overdriven by a factor of 20 or more. If you reduce the number of windings in the motor, you can reduce the back EMF in the motor and increase it's operating speeds, but you'll probably still need to overdrive it. Driving it with a higher voltage will help too, such as using two 12V batteries in series. You'd be better off finding a centrifugal supercharger that already has an overdrive mechanism built in. You might be able to trade the turbo for a used centrifugal at a swap meet.

[amctmg]

I don't know about anyone else but I think there is alot of potential there If done right. I will be working on this till I get it.


Has anyone ever seen that roots type blower with 3 starter motors on it? I think they wanted like 2 grand for it I can't remember where I saw it at.

[smilla0]

It could definitely work, and I'd love to see it if you get it working. But I think you'll find a lot of unforeseen obstacles along the way. I had considered this idea for a while, but when I realized that it would be way easier and cheaper to do a supercharger or turbo, I gave up on it. The electric supercharger definitely does have it's perks like the potential for instant off idle boost, low parasitic loss during boost, and greater emissions legality. However, the difficulties and expense of implementing it will make it impractical.

Ok, here comes the depressing part:

To get decent boost, you'll need at least a 15hp electric motor. Finding a 12V DC motor of this size is not easy. You could buy one for like $2000-$4000 maybe. A 15hp motor produces 11.25 kW of power. Assuming it's 60% efficient on average, it will require 18.75 kW of electricity. From a 12V DC source, that's 1562 amps. A typical car battery can supply around 200 amps continuously. Maybe a really good one will supply 800 amps, so you'll need 2-8 lead-acid batteries to power this thing. That will add anywhere from 60-300 lbs to your vehicle weight, and probably in the rear. You might as well just use another engine. And under that kind of abuse, you'll probably be replacing them every few months. And all this for the boost from a $2800 JRSC.

Even if you can get it built and powered, you still need to control it. You'll need a foot switch on the gas pedal or a tap into the throttle position sensor. In order to maintain a constant boost, you'll need a servo controller for the motor. You won't find a commercial off the shelf unit to do everything you need, so you'd have to build it custom using something like a PIC microcontroller. But that microcontroller won't be able to control the motor directly. In order to control the power to the motor, you'd want to use a method called "pulse width modulation". Instead of using a potentiometer like in a volume control, you have something switch the motor on and off really fast. If you want 50% power, you switch it on 50% and off 50%. If you want 25% power, you switch it on 25% and off 75%.

To switch 1500 amps on and off you'll need a really huge relay (or a bunch of relays in parallel). The relay itself will probably require about 10-15 amps. Just to control this relay, you'll need yet another large relay which will probably be activated by around 1/4 amp. This is still too much for the microcontroller to control so you'll need to use a power transistor to activate the smaller relay used the milliamps produced by the outputs of the microcontroller. You'll also have to install an encoder on the shaft of the motor so the microcontroller can measure it's speed and adjust the PWM to speed it up and slow it down. Hope you sharpened up on your control theory :)

Note also that the average alternator pumps out about 60 amps max. So for each 14 second 1/4 sprint, you'll need to wait about 700 seconds (about 11.5 minutes) for it to recharge batteries (and that assumes the recharge/discharge cycle is 100% efficient, which it's most certainly not).

And god help you if you actually try cranking up the boost to make like 400-500 hp. You'll need like a 60 hp motor, have to control like 6000 amps, and wait an hour between sprints. You could have a bottle of nitrous shipped faster than that.

Not to be mean, but by the time you're finished, you could just as well have converted your Si to RWD, and put a quad turbo 500 ci big block in it. You'll run 6's all day long without having to wait. All of the sudden, that doesn't sound like such a bad idea...

Sorry if I crushed your dreams :) I just didn't want you to spend weeks and lots of money working on this only to hit a dead end. It's a novel idea, but the details make it unworthwhile. Whenever I come up with a crazy idea like this, I do one of these analyses and it soon becomes obvious why it's rarely, if ever, done.

[Speck]

Originally posted by specialblend154
wow... i cant believe i clicked on this thread

ROFLMAO!!! This is going in my sig!!!

-=speck=-

[crazyDC5]

Thomas knight turbos has figured out the electric motor problems. This seems to be a nice system for the money. It works for 15 sec. bursts like nitrous. thomas knight turbos :D

[amctmg]

Yeah thats the one I saw but I don't think you need 3 motors to run a turbo but it does need to spin fast

[smilla0]

Nice find! It seems to work a lot like I predicted. 15 kW power for a JRSC type system. He recommends 4 or more batteries, and claims 10-20 minute charging cycles with a high power aftermarket alternator. But that web site is full of BS. As I expected, without a motor controller, the boost is really high down low when the flow rate is low, and the boost is lower up high when the flow rate is higher.

The FAQ is peppered with BS, though. For instance, the alternator will be maxed out trying to recharge the batteries, and this will cause a modest parasitic load. A high power alternator like he recommends will cause an even greater load.

$2000 isn't a lot for a eaton blower and 3 electric motors, but when you factor in all the batteries you'll need and other fittings and such, I bet it will start to add up. Here's the address:

http://www.boosthead.com/

My god, it gets even funnier when you really read his website. When you add up other required components not included in the kit, he says it totals $3500, which is using mostly used parts. Plus he says that jury rigging this system is easier than installing a bolt on turbo or supercharger system. The guy could have made a better and cheaper system using a centrifugal with a more constant boost level, even without a motor controller.

You could use a single 6 hp motor with any of these systems, but as soon as the engine speed starts increasing, the blower will require more power to keep up, and the electric motor will get bogged down and the boost will drop. That's partly why if you read this guy's site he says it produces much more boost at lower RPMs.