Roadkill boost caboose got me thinking...

I just watched the latest episode of roadkill (Click here if you've somehow managed to miss it) and it was fun, yet overwhelmingly impractical. any power it would ad would be negated my having to tow around a second engine on a trailer. It made great TV, but that was about it.

This got me thinking. Is there a point where this actually balances out and makes sense? Like a trunk mounted Suzuki G10 diving a 8-71 off the crank.

I have no intention of actually building this, I just wanted to throw the idea out here and see what happens. Sort of like yelling fire in a crowded theatre...

Well, they also wasted a ton of power capacity. I bet the throttle was just cracked on the caboose to achieve the desired rpm.

If you designed a motor whose sole purpose was to spin the supercharger, yes you could get away with a much much smaller and lighter motor.

I want to know why this hasn't been done with a big electric motor driving a compressor. Run an extra battery, and use a full throttle switch to control the when the motor comes on.

Come to think of it, that might fit in my challenge budget....

I built a Monster Truck in the late 80s. I used a VW engine to run the powersteering. I have always been a cheerleader for having a separate powerplant do the odd jobs to keep full power to the wheels

There was a dragster built back in the 1950s that had a separate engine mounted on the back (if I remember correctly it was a military surplus Evinrude outboard motor) used to run a supercharger,

There's no free power, but some power is cheaper than others. It's going to take a certain amount of horsepower to propel any direct-drive power adder, like a supercharger. Whether it comes as parasitic drag from the primary engine or from a secondary power source, you still have to spend the same amount of power to spin it.

That said, the idea of being able to very specifically package a particular arrangement has its advantages. A primary engine that sits low in the chassis with a low hood line and low cg, fed by a supercharger powered by an electric motor or a small two-stroke piston engine also placed low in the chassis is intriguing.

But, if you're going to go to the complexity of having an electrically-driven blower, why not just skip a step and have the electric motor help the primary drivetrain directly?

From a junkyard build perspective, though, it's clever. There's no reason to drive the blower with a 350, though. What's a snail blower like that need for power to operate? 35-40hp? Throw a Briggs and Stratton on there and head for the horizon.

JG Pasterjak wrote: But, if you're going to go to the complexity of having an electrically-driven blower, why not just skip a step and have the electric motor help the primary drivetrain directly?

Except the power adder lets you add more fuel, which is the whole reason you put a power adder on any motor. The supercharger has a parasitic loss of 35-40 HP sure, but it allows you to add 100 HP of fuel, meaning your engine nets a higher power output. If the supercharger used 35 hp and only gave 35 back (no net improvement) no one would use them.

I think a Aixro XR50 rotary engine driving a vortec supercharger would be pretty feasible. It also puts you deep into the territory of netting more power than you would gain by direct coupling the power unit to the main engine. 10lb boost on a V8 > 50hp of tiny Wankel + V8 (echoing Robbie here)
At that size and weight it's pretty feasible to stuff it in the trunk or juts hang it off the front bumper.

MulletTruck wrote: I built a Monster Truck in the late 80s. I used a VW engine to run the powersteering. I have always been a cheerleader for having a separate powerplant do the odd jobs to keep full power to the wheels

Yeah, we're gonna need to know a LOT more about this. You can't just drop "I built a monster truck" and not give details...or pics.

(edit)

Was this it?

http://monsterphoto.iwarp.com/goldust.htm

Also with a seperate power source driving the supercharger it could be at peak boost all the time, no lag.

It balances out when half of your supercharger is a jet engine.

ProDarwin wrote: It balances out when half of your supercharger is a jet engine.

Dammit, you beat me to it.

I still say the Turbonique Drag Axle needs to make a return

What you Guy's miss is the REAL amount of HP it takes to make Boost with a crank driven Supercharger,On An Engine making 800 with a GMC 6 or 8 71 it takes 400 to drive it thats why a turbo on the same engine will make closer to 1200,ya just have to wait for it.

Hmm... Airplane APU feeding the bleed air output into the engine intake? Some of them can feed 150 lb/min of air or better at 40 psi If I don't suck at numbers, we're talking about enough air to support north of 1000hp. With no boost lag This would be somewhere in the realm of "really loud, burns a lot of fuel, but goes stupid fast"

And the alternator, power steering and other accessories could be run off the APU as well, keeping them at constant RPM (and if you gear them correctly, they can stay at a pretty ideal RPM without worrying about over-spinning them).

ProDarwin wrote: It balances out when half of your supercharger is a jet engine.

I read an article a few days ago on how jet / turbine engines work. I read the first few posts here and thought "I'll float the idea of using a small turbine engine to spin a compressor" assuming that a bunch of automotive psychos didnt try it 50 years ago. Those old timers crack me up. Cars had bad brakes, bad steering, terrible tires, and they all thought "This needs a lot more power!"

Well it was RoadKill, Most racing Prohibits secondary power plants wether for suction(Jim Hall, Chapperal) Vacuum Vette's or pressure. And you are right about the need for speed.My 53 studebaker was plenty Fast,But took BOTH Feet on the Brake to Stop

The OP's idea sort of reminds me of the Bloodhound SSC Land Speed Record car that used a Cosworth F1 engine to drive the fuel pump for the jet engine.

Given the advancements in small scale RC plane turbines I've been eyeballing an exceedingly compact self-driven turbo setup.

45lbs of thrust and weighs 3.3lbs http://www.dreamworksrc.com/catalog/Merlin-M200Xbl

GTXVette wrote: What you Guy's miss is the REAL amount of HP it takes to make Boost with a crank driven Supercharger,On An Engine making 800 with a GMC 6 or 8 71 it takes 400 to drive it thats why a turbo on the same engine will make closer to 1200,ya just have to wait for it.

The math is wrong on this one. By that rational a Top Fuel hemi would take 5,000hp to spin it. It doesn't.

Adrian_Thompson wrote: The OP's idea sort of reminds me of the Bloodhound SSC Land Speed Record car that used a Cosworth F1 engine to drive the fuel pump for the jet engine.

That's very surprising because the jet engine they're using probably came out of a fighter jet, and the fighter doesn't need an F1 engine to run the fuel pump. Just a one-horsepower fuel pump can move a LOT of fuel, and one horsepower is only 750W or so. I haven't read up on the Bloodhound but there must be something else going on.

[edit] Okay, now I understand. From the Wiki "...A third engine, a Jaguar supercharged V-8, will be used as an auxiliary power unit and to drive the oxidizer pump for the rocket..." Yeah, driving an oxidizer pump would take hundreds of hp. You may proceed.

Appleseed wrote:

GTXVette wrote: What you Guy's miss is the REAL amount of HP it takes to make Boost with a crank driven Supercharger,On An Engine making 800 with a GMC 6 or 8 71 it takes 400 to drive it thats why a turbo on the same engine will make closer to 1200,ya just have to wait for it.

The math is wrong on this one. By that rational a Top Fuel hemi would take 5,000hp to spin it. It doesn't.

I was thinking that too. I think the decided figure for a Top Fuel Blower is around 1000hp. And those are moving massive amounts of air and fuel at a near solid state, as the engine operates at near-hydrostatic lockup.

In reply to kb58:

Yeah, slightly incorrect memory on my part. I remember reading it when Bloodhound first kicked off which has to be 6 or 7 years ago now. I then google image searched 'Bloodhound SSC Cosworth' for the pic I posted.

Hey guys.......

http://www.phantomsuperchargers.com/

rslifkin wrote: Hmm... Airplane APU feeding the bleed air output into the engine intake? Some of them can feed 150 lb/min of air or better at 40 psi If I don't suck at numbers, we're talking about enough air to support north of 1000hp. With no boost lag This would be somewhere in the realm of "really loud, burns a lot of fuel, but goes stupid fast"

It's been done, there's an open-wheel hillclimb car that works like this. Can't find videos of it now...

Compressed-air supercharging is also a real thing that works. You literally just pre-charge tanks with a berkton of pressurized air and then blast it into the engine with some sort of fuel enrichment. Mickey Thompson even experimented with it back in '71

In reply to NickD:

Didn't the last F-150 lightning also have this? It was good for a 50 shot or something similar?