CFD/CAD/Thread

[SchmidtMotorWorks]

Those box cross rams work really well on the 426 hemi. If he sized it correctly for the planned 500" engine and rpm range it could work really well.

He knows a bit about building high performance engines, so I suspect he did his homework.

These?

Hemi parts intakes 012.JPG

[bob460]

Those box cross rams work really well on the 426 hemi. If he sized it correctly for the planned 500" engine and rpm range it could work really well.

He knows a bit about building high performance engines, so I suspect he did his homework.

True, But you never really know untill you hit the dyno!!

[JC565Ford]

These?

Hemi parts intakes 012.JPG

The one I was thinking about have the carbs more side to side. I don't know how much work they take to make run, but I've read that they are pretty good parts for the engine.

[SchmidtMotorWorks]

The one I was thinking about have the carbs more side to side. I don't know how much work they take to make run, but I've read that they are pretty good parts for the engine.

A cross ram manifold like that has some built-in disadvantages:

The runner openings are usually boxed in on 3 sides so the wave pulses are diminished.
The air trajectory reverses direction with small turn radius so fuel suspension is diminished, puddling is a problem.
Plenums have too much width to height ratio
Too much sharp corners in plenum

I have friend that had one on a 426 Hemi, it loaded up terribly after letting off the throttle as one would expect with a plenum with dead air space.
In street racing his 2-plane 2x4 manifold was much better because he could feather the throttle...the cross ram would load up take a second to clean out.

[tjs44]

Jon,how come our intake works so good on the street and races well?Tom

[Erland Cox]

I have run a Max Wedge cross ram on a 446 without any problems.
On the street with a .690" lift roller cam.

Erland

[SchmidtMotorWorks]

Jon,how come our intake works so good on the street and races well?Tom

There is a lot of upside potential if a new design were made that incorporated what we have learned in the past 50 years.
It wouldn't have the hood clearance that your manifold does though.

[juuhanaa]

This head had a 50º seat and 92% throat. I will add more as the thread goes.

Im assuming that the material behind the valve is minimal, and the hood clearance is already near perfection considering the other class rules.



-juhana

[JC565Ford]

A cross ram manifold like that has some built-in disadvantages:

The runner openings are usually boxed in on 3 sides so the wave pulses are diminished.
The air trajectory reverses direction with small turn radius so fuel suspension is diminished, puddling is a problem.
Plenums have too much width to height ratio
Too much sharp corners in plenum

I have friend that had one on a 426 Hemi, it loaded up terribly after letting off the throttle as one would expect with a plenum with dead air space.
In street racing his 2-plane 2x4 manifold was much better because he could feather the throttle...the cross ram would load up take a second to clean out.

Over the years I've run into a couple people who loved theirs. It was my understanding (I could be wrong) that those manifolds ran well in the NHRA classes. Maybe someone knows better ?

Also, the manifold that was posted for the 500 in engine is an EFI manifold. That would eliminate quite a few of the issues you stated.

[SchmidtMotorWorks]

Over the years I've run into a couple people who loved theirs. It was my understanding (I could be wrong) that those manifolds ran well in the NHRA classes. Maybe someone knows better ?

Also, the manifold that was posted for the 500 in engine is an EFI manifold. That would eliminate quite a few of the issues you stated.

Good compared to what? There is good reason that OEMs don't make manifolds like that anymore.

Regarding issues mitigated by EFI

The runner openings are usually boxed in on 3 sides so the wave pulses are diminished.
-Not mitigated

The air trajectory reverses direction with small turn radius so fuel suspension is diminished, puddling is a problem.
-Not mitigated when the injectors are positioned in an area with much velocity and there are also areas of low velocity and horizontal floors near the runner entrances

Plenums have too much width to height ratio
-Not mitigated

Too much sharp corners in plenum
-Not mitigated


There is good reason that OEMs have converged on manifolds that look like this:
This manifold probably has more R&D invested in than all cast aluminum cross-ram man-folds ever made combined.
This series of manifold performed as well as any tunnel ram and fit under the hood of a Mustang.
And they sell them for about $400.

coyote.jpg

[JC565Ford]

Good compared to what? There is good reason that OEMs don't make manifolds like that anymore.

Regarding issues mitigated by EFI

You can try to convince the guys who posted above that theirs don't work near as well as they think they do.

[SchmidtMotorWorks]

You can try to convince the guys who posted above that theirs don't work near as well as they think they do.

"Well" compared to what?

The characteristics of an optimised manifold are well established.

Tuned length
Tuned cross section/taper
Round rather than rectangular cross-section to the extent possible
Uniform bell mouth opening around full perimeter
Minimal low velocity volumes with fuel
Uniform distance from runner openings to plenum walls
Minimal reversals in flow
Minimal horizontal surfaces in plenum with fuel

[JC565Ford]

"Well" compared to what?

The characteristics of an optimised manifold are well established.

Tuned length
Tuned cross section/taper
Round rather than rectangular cross-section to the extent possible
Uniform bell mouth opening around full perimeter
Minimal low velocity volumes with fuel
Uniform distance from runner openings to plenum walls
Minimal reversals in flow
Minimal horizontal surfaces in plenum with fuel

You need not convenience me that something more modern can be made better. You probably don't even need to convince the guys running them that something could be made better. I'm sure they would agree. You made a post above stating how bad they were and un-tunable. There are guys running them ( two posting here) that have a different experience with theirs. Maybe they are wrong and you are correct about what they have experienced ?

[digger]

That coyote design looks like packaging was the main concern. There’s never been anything OEM that couldn’t be improved upon by skewing the priorities to be bias more towards performance

[pcnsd]

That coyote design looks like packaging was the main concern. There’s never been anything OEM that couldn’t be improved upon by skewing the priorities to be bias more towards performance

I'm not so certain that performance was not a high priority in that design.
1. Moving the plenum under the runners allows longer runners to target an RPM between PHP and PT with a lower a wave number for the expected tuning range.
2. Reduces the turn radius into the plenum which reduces frictional flow loses by reducing the higher velocity inherent in tighter radii.
3. It still fits under the hood!

When I see enlightened designs... I always wonder why it wasn't thought of before. My impression of disc brakes and planetary gear reduction too.