2457 Engine Setup

quote:

Originally posted by Husker:
This doesn't look very efficient to me. Can someone explain the theory behind this setup.

A supercharger can be set up to either blow through a carburetor or suck through it.

In the case of sucking through it, the carb would be on the intake side of the supercharger and would blow into the intake manifold.

The Paxton superchargers used on the Shelby GT350's blow through the carb. In order to do that you need to put the carb into an airtight box (like this set up) and blow into the box.

The problem with that is you have limitations as to how much you can pressurize the carb.

First off the floats need to be solid so they don't get crushed under the pressure, second, the fuel pressure needs to be higher then the boost of the supercharger.



My Audi TT is pressurizing the induction to a top of 27 psi. That's a lot of boost. I've seen a sb Chevy at 3 atmospheres which is roughly 36 psi. My Audi has 40psi of fuel pressure which is about normal for a fuel injected car anyway.

I don't think that I could make a carb withstand that kind of boost though and certainly just with those hose ports going through that air box, it isn't going to be tight enough to hold the boost.

That kind of boost is very hard on the driveline as well. It hits it like a hammer. A 250 or 300 hp hammer. That tends to snap forged steel components in half, but I digress.

I don't understand what is going on with this Pantera since it only needs one turbo and certainly it isn't running 75psi of boost. That ain't happening.

Plus even if it does, that air box will blow up. Kabluie! Bam!.

It would also snap the block in half with one throttle blip.

Anyway, it would be better to suck through the carb. Much better. Much safer too and it only needs one turbo.

...oh, you need a computer to handle the ignition advance with this setup, and it isn't simple because it needs to know what to do when the engine is not under boost and when it is AND how much.

I would have used a Paxton cast air box and stayed away from the Home Depot diamond plate top but that's just my taste.

This whole car looks half-baked.

Check out the pix on the ProvaMo site, with a roof scoop that is not connected to anything (or so it appears).


But I may be wrong.... There could be a lot of engineering behind this whole configuration that is not obvious to the casual observer....

Rocky

Here's another "Positive Blow" turbo setup. This one looks to be a little cleaner construction.... S/N 2467.

the ProvoMo translation says the twin turbo was installed when new (early 70's ?).

Seeing that pic reminded me of the reams of turbo data I had from the late 60's technology

Well, Porsche is one I can think of that went to a two turbo set up on their race cars.

The reason that they did that was they were looking to reduce the time it takes for the driver to hit the throttle and the turbos respond, i.e., reduce the "turbo lag".

They went to two smaller turbos rather then one larger one. How much advantage that gives, I can't say but in a street car, driveability is an important consideration.

The first set up has a blow through carb in the box and the second is fuel injected with a throttle body and plenum sitting on top a tunnel ram base. The biggest issue with both....neither one is intercooled. It depends what the static CR is but without intercooling or some other means of detonation control such as water/methanol injection, I bet neither of those systems can safely run more than 1/2 ATM of boost. It also assumes the turbos are sized to spool within an rpm range reasonable for how the engines are cammed.

Back in the 70s and early 80s, set ups like that showed up now and then because making 450-500hp was a bigger deal but today a 500hp naturally aspirated street engine is common place so why bother with all the additional overhead, complexity, and weight? I have an acquaintance with such a set up and he has a box full of bent rods for his trouble. Today TT V8 street set ups are routinely North of 800HP (some well North) and they are a blast in a straight axle straight line car but using it in a Pantera? Maybe an unlimited open road race car but other than that I'd take a nice running NA engine.

Best,
Kelly

quote:

Originally posted by Panterror:
The first set up has a blow through carb in the box and the second is fuel injected with a throttle body and plenum sitting on top a tunnel ram base. The biggest issue with both....neither one is intercooled. It depends what the static CR is but without intercooling or some other means of detonation control such as water/methanol injection, I bet neither of those systems can safely run more than 1/2 ATM of boost. It also assumes the turbos are sized to spool within an rpm range reasonable for how the engines are cammed.

Back in the 70s and early 80s, set ups like that showed up now and then because making 450-500hp was a bigger deal but today a 500hp naturally aspirated street engine is common place so why bother with all the additional overhead, complexity, and weight? I have an acquaintance with such a set up and he has a box full of bent rods for his trouble. Today TT V8 street set ups are routinely North of 800HP (some well North) and they are a blast in a straight axle straight line car but using it in a Pantera? Maybe an unlimited open road race car but other than that I'd take a nice running NA engine.

Best,
Kelly

Yes, it's ancient technology. It's a 6 to 10 psi boost system with much the same results as a Paxton supercharger would deliver.

Neither make much sense unless they both were some kind of a high school auto shop project.

Plus, think of all of the heat sitting right there under the rear deck sheet metal.

Doing this the right way, presuming that "you had to have a dual turbo" setup to begin with, doesn't work well with the Pantera chassis and body restrictions.`

The advantage that I can think of though in both cases, is that this is all a bolt on system and they both can be unbolted and returned to stock.

This reminds me of the Barney Miller episode in which the NRC is called into a case where a Columbia Grad student has built a "nuclear device" but without the plutonium.

After being declared as completely functional but just missing that material he is asked by the re-patriated ex-Nazi representing the NRC what he thought his grade would be?

He replies, "a C+, you have to see what the guys who get the A's and B's are doing!"