So, when I bought my car, it had a Jun fiberglass hood with the central vent enlarged to something like two square feet.

It occurred to me after I replaced it with this Scoot-style (probably a knockoff?) carbon hood that they probably did that for a good reason.
Namely, it allowed the rather large v-mount intercooler to work better. I pulled the wire mesh off the vent and added a water sprayer using my stock windshield washer, and that seemed to make a bit of a difference in the temperature of the intercooler.

Should I go ahead and just double the size of my central hood vent?
I would love to just have an RE-A-style six-vent hood and go back to an aftermarket bumper (I destroyed mine), but I don't see the need to spend the money.
The only reason I can think of not to enlarge the hole too much is to protect the alternator from water. I wouldn't make it that big. Just maybe double the current size, so as to avoid weakening the hood.

Thoughts?

 

Also, the mini vent in the back probably isn't doing much, is it? That's probably a high pressure zone, so making it bigger might actually force air in, rather than pull air out.

The air intake vent probably isn't doing much, since that's a low pressure zone.

 

air in is not necessarily bad if there’s an appropriate place for it to get out
.

 

Maybe, except I a worry that the hot air from the central vent is what would get pushed inside.

With my old bumper, the intercooler would be cool to the touch after track runs even with the smallish hood vent. It was only after I went back to my modified stock bumper that it started to get hot. I think.

 

I'd definitely be tempted to double the size that vent over the IC.

 

The M2 prototype thing back in the day, Mazda here altered the original aluminium pressings from that with RS500 Sierra ducts on the outboard trailing edges, which you assume wasn't purely for appearance. Rather than guess what's happening, a few strategically placed wool tuffs might enlighten?

 

Which M2 prototype? The RX-7 basically has the same vents as the SP.

When I broached the subject of expanding the vent with my shop, he was convinced that it wouldn't increase airflow without doing a but of extra work on the hood due to turbulence. I am not entirely convinced.

 

Looking it up - it's the 1020. The bonnet off that was used on the SP, with the additional vents added locally. With a quick search here's one from yahoo several years back that was going for an insane price and an SP fibreglass replica that maybe has poor panel gaps https://www.ebay.com.au/itm/233769690191

There's plenty of broad brush hypotheses in the car game regarding air. The general rule of thumb about high pressure at the base of a windscreen stopping air evacuating the engine bay I've noticed isn't always true........maybe suffer a drag penalty though! Short of 1 lap time attack nutbag budgets, a few cents on a ball of wool might be the best us plebs can do.

and SP

 

you won't be able to tell without testing it

 

I wish I had access to a 3D scanner and CFD software… I don’t want to have to uncut the hood!

I figure it would ultimately flow more, but not proportionately more.