300, manifold design, force feeding ????

[Thad]

This posting is in answer to some questions in a PM about intake manifold design and turbocharging or supercharging the 300. Also the differtence between the two different efi manifold, truck vs van.
Placed it here so all with experience and better knowledge could get involved. SO JUMP IN with your two bits.

In a blown engine, turbocharged or supercharged, because of pressurised forced flow equal length runners are not as critical as in a normal aspired engine. Port flow is still just as important, pocket porting clean ports and bigger valves are a benefit.
A good home made intake for a blower or turbo would be the lower half of the efi manifold with a plemun box in place of the top half. For a turbo the pressurised air tube could come up from the turbo below on the exhaust manifold between runners number 3 and 4. For a supercharger mounted on the passenger side of the block, the pressured air would be ducted over the valve cover to the plenum.

Couple of observations:
In a draw through turbo system there is a certain amount of temperature drop inlet air when the fuel is gasoline. This would not be the case with propane unless in liquid state when injected.
In performance engines, turbo work best in shorter stroke engines that wind up and the turbo can "get on boost". Boost does not come in on the bottom end as you desire.
A supercharger starts building boost as soon as it starts turning, from the bottom. A displacement type (ie Eaton) comes on faster than a centrifugal (ie Paxton). Bunches of Eaton type on eBay. Centrifuges too for that matter.
Centrifs would probably be easier to mount and make a drive system for, but the extra effort for the displacement type would be worth it.

Sorry not knowleggeable about the difference between the truck efi manifold vs the van manifold.

 

[Anonymous]

I would think that the stock EFI upper plenum would flow enough air for the lower to flow. i think the restriction would not be in the upper, but the lower, if at all.

The most restriction i believe would be in the throttle body itself, as the two 1.5 inch holes could cause a problem when you really need/want the air. Even though its turbo charged, if the engine RPM (more air consumption) exceeds the intake manifolds flow limit, the air consumption would be too great and the flow restriction would effectively be at the throttle body.

I do believe that there is not a difference between the manifolds on the truck or van as the 300 is a long skinny motor and width is usually the problem with fitting engines in the van bodies. I know that the Diesels are espcially crammed and modified with different parts to get to fit becasue of witdth, but height doesnt seem to be a very big problem.

 

[Thad]

On the two efi manifolds I have cut up, the runners in the top and lower section have the same ID 1.675" constant diameter. Being port injected manifold is designed for dry flow.

The plenum chamber was internally divided giving the effect of two three cylinder engines.There was a balancing port between the two.

As far as restriction in manifold no problem because we are dealing with to different flow regimes, vacuum versus pressurised. More can be pushed through than sucked through.

The reason for using only the bottom half in a turbo or super charged system is because the long total length runners are not needed and are no benefit, there is no resonate ram effect under pressure. The lower half is all that is needed.

 

[82F100]

I have a ? does anybody know if all the ford throttle position sensor hookups are the same? For a turbo what about a plenum box with maybe a 70mm throttle bodie and egr plate from a V-8 mounted to the efi lower?I would think that something like this would be easier to set up for a turbo application.

 

[Thad]

TPS on 300 efi and Mustang Cobra efi have the same plug and mounting screw position.

Throttle butterfly needs to be draw through. Pressurized there is sealing problems and a definite possibility of the throttle plate jamming.

 

[82F100]

Ok....but all throttle bodies i have seen with turbos have been mounted to the intake and not infront of the turbn the most supercharchers roots and eaton style the throttle bodie is infront of the pwer adder except the paxtons and vortech's.

 

[Thad]

On mechanical superchargers, Rootes, Eaton, PSI usually the throttle body is on the inlet side of the blower. The placement of the TB is pretty much dictated by design . The fuel supplier can be carbs on inlet or fuel injection. The injector can be on the inlet side below the TB or port injection or both.

Centrifugal blowers, both mechanical driven (ie Paxton) or turbo driven are more flexible in layout. Form fits function, limited by packaging space or design output. Systems can be as simple as a carb pressurised in box or carb draw through on inlet of blower. Strictly a matter of packaging.
EFI can be TBI in front of blower with no intercooler. Or TB in front of blower through intercooler with port injection. Or TB behind blower and so on----.
The type, design and complexity of the EFI system dictates the placement of the components. Each design has pluses and minuses.

A large consideration is what it is to be done. A simple design for a simple street application or a full boogie blow their mind max warp speed unit.

 

[Anonymous]

Do you think using the stock upper plenum would result in comparable performance than a different upper of the same basic packaging and throttle body inlet?

Reason for asking is: Is it worth it to replace the stock plenum with another not designed for an NA engine just to get the same performance, with a forced type of induction.

Because something could very easily be adapted to the lower plenum with a little fab and a throttle body with a TPS...

I can imagine there will be more restriction on the stock plenum because of the divider and extra length the air needs to flow, but is it substantial enough that if the upper was eliminated, it would increase power...for a street type of engine...

Is it worth the time and money for what you get out of it?

 

[Anonymous]

To elaborate on Thad's statement regarding flow rate and being under vacuum versus pressure:

Volume flow rate has no dependance on how the flow is generated-> it's just velocity * cross sectional area.

What's important here is Mass flow rate which involves another variable density. So, assuming ideal gas, PV/RT = density. More pressure yields a greater density and hence more mass flow, yet opening up the cross sectional are will improve mass flow.

 

[Thad]

Eme---

Under boost the "ram effect" that runner length imparts is no longer present. So long runners are no longer needed, in fact under boost the longer the runner the greater the resistance to flow. A plenum box on top of the efi lower would be a good set up for a boosted 300 engine.

Using the lower with a fabricated plenum for carb(s) would probably be as good as any aftermarket manifold available. Good smooth, equal length runners. Using only the lower would change the rpm where the "ram" effect occurs to a higher rpm. But the runners are longer than most aftrermarket manifold so the modified efi lower would have the "ram" occurring at a lower rpm than the aftermarket manifolds.

 

[Anonymous]

Yeeah..i totally see where youre coming from Thad...the plenum box may have more of an effect that what there seems to be when it comes to the ram effect.

Too bad the stock upper intake is conveniently pointed towards my intercooler outlet.

 

[Thad]

Got a pic or two? Maybe we could draw something up.


Questions:
Intercooler out let points from driver side to passenger side?
How close to middle of engine?
Could you plumb a alum tube from intercooler outlet across the top of the valve cover to a plenum fabbed on top of the lower half of the efi manifold?