458 Speciale Spec Challenge Grill for F355 ?

Gorgeous

 

The Challenge grill should have been constructed from the same material as the f40/f50/458 from the start. My guess is that if produced it would become a popular look.

 

Take my money!

 

I will be building something similar to the Barchetta for a 348 race car. If Ferrari had used round taillights these would have been the right parts for when the car was built. If anyone has a source for the correct mesh.. Please share.
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I'm sure the design of the 458 grill was to increase the porosity if the grill over the older small hole design for functional purposes

The hole pattern of the 355 grill reduces the effective opening of the covering to 25% of its original size.

If you remove the grill, there are 6 square openings in the body approx 5x5 inches or 25 square inches.

By putting the challenge grill over those openings you are effectively reducing those openings to 25% of original or to approx 6 sq inches or a 2.5x2.5 inch hole.

The grill design on the newer cars is much more porous and allows more air flow through the grill.

 

Bob, air will flow thru the enitre perforated area of the grill even though the entry of air is coming thru the 3 squares you reference.

 

There are 6 squares in the body. They are the first line of resistance to any air flow and limit it. Beyond them the grill then covers them with a barrier that only allows 25% of their original lumen to be functional. The size of the squares is effectively reduced as I outlined above.

The newer style grills appear more porous because they are more porous by design

 

That is not true Bob.

 

It is absolutlely a fact.

 

Close off all those openings but one and air will still flow the entire perforaded area of the grill. Thank you.

 

Ok Dave. I'll prove the reduction in air flow to you. Stay tunef

 

Bob, heat escapes via convection and also air flow. Regardless of you or I believe, the fact is the OEM Challenge grill does provide a benefit. How much is really immaterial to the discussion.

 

This is a statement of fact. I didn't say anything other than that.

 

Bob, the rear panel (behind the grill) does not sit directly against the grill - there is an air space between the rear panel and the grill. Once the air enters that air space, it will flow out every place it can and will not be limited to the square areas.

Thank you.

 

That has no relationship to what I said. The only air that is allowed into that space is the air that was allowed via the six squares. The volume of air that can escape through the challenge grill is limited to the volume of air that is allowed to flow through the squares.

Simply put. If 3 cubic feet/minute of air is allowed into that space, 3 cubic feet of air per minute will not be allowed through the challenge grill. The volume and flow rate through the grill will be on the order of 25% of what it was through the squares. It is physics.

Watch the video:

https://www.youtube.com/watch?v=u3XxLoXCn4M

 

Your neglecting the vacuum draw thru the perforated areas of the grill...

 

I commented on this thread in discussion of the new grill designs and that they are more porous and allow greater air flow through them than the older designs as in the 355

My comment if you look back was that the design was most likely not of an esthetic nature but of a functional one as I bet that newer design allows 50% air flow as opposed to 25% on the OEM 355 grills.

To your point, if I put a vacuum on the other side of the tell tales in that vid and it becomes effective in increasing flow , the same proportional reductions in flow will occur when first the squares are introduced and secondly the screen.

It also doesn't matter if I hold the screen up against the squares directly or a foot away. The telltales will droop the same amount. It doesn't matter if there is a space between the body and the grill. The airflow reduction occurs as a result of the two barriers.

 

Looking at the size of the square holes in the inner rear panel, I can't see that they're going to make a critical difference to the heat extraction process (and let's not forget that the car vents heat from the engine cover ans well as the rear grill).

Standard road cars seem to run fine with a solid outer panel between the rear lights, and challenge cars seem to run fine with the standard grill - even the full blown race versions!

(surely if it heat extraction was so critical then Ferrari would have fitted a modified inner panel with a single, large rectangular opening rather than the standard panel with six holes, and they would have fitted larger vents on the engine lid on the race versions? [or even extraction fans?] ).

 

I concur and had made that point on another thread as well.

IMO if you like the look of the challenge grill then go for it. If you are expecting it to make a real difference in heat removal, as you can see from that video, it is very restrictive and you are better off having no grill then and just the squares.

 

I will tell you that when I first installed the Challenge grill, I was not sure I could tell the different in heat. But as time went on, there is definably a noticeable difference.

 

I agree with the premise that larger opens in the grill would allow more air to escape, and might look pretty cool as a bonus! Neat idea.

 

While I don't know the numbers Bob Claims he is more right than wrong. The gist of what he says small hole flow less than big holes is sound. Any restriction upstream effects the flow out. So he is right again. Functionality of the challenge grill was always suspect. Ferrari designed the 355 perfectly with no challenge grill. The car does not need this claimed functionality. Vaccum at the tail is a red herring. Any vaccum would effect large pores as small pores just like the pressure that wants to drive the flow from engine bay to outside. it is sucking on a big straw vs. a small straw. Bob is right it is the pore size. Some call it "functional" I call if "drag" as in aerodynamic drag. It does not make the car faster and might make it slower. Racing is a compromise. If the C cars needed to be cooler, seeing action the streetcars did not, then C grill is what is needed even at the expense of added drag. Lay people like the C grill because it is pretty not because it is functional.