N/A irons - Engine rebuild
 

I'm in the middle of building a 2nd gen 13B engine.

The irons I have specced out as questionable. For an N/A build, are S4 or S5 irons preferable? Or are there another set of irons that I don't know about that would be best for this application?

(Edit) I have no hesitation on spending the cash on, for instance, 13BRE irons.

for a normal street n/a build use 6 port irons and get your 6 port system working like it was designed to work. then you will have the broadest powerband, especially if you have s5 VDI. The intake system on the s5 is a great design. The aux ports change "valve timing" and "valve lift" while the VDI system effectively changes runner length. Why do you think Honda copied the s5 n/a on the NSX and Integra GS-R?

I'm going to give a bit more detail now that I have a firmer picture of what costs what.

I am rebuilding a 13B. I may or may not go turbo with it in the future, I am not sure yet. However, I would definitely like to build towards that and have no hesitation whatsoever in picking up a set of 13BRE irons.

Current plan: S4 N/A irons, FD Housings, S4 N/A rotating assembly

However, speccing out the S4 N/A irons reflects a very questionable quality to them - I'll have exact measurements today.

Based on prices, it is -far- cheaper for me to pick up some very low mileage 13BRE irons then have my current irons lapped or refinished.

This leads to the natural extension - "But what about picking up N/A irons?". Problem with that is I see very few for sale of the quality I would want. I'm obviously not interested in 100k+ N/A irons that spec questionably (Like my current ones!) if I am willing to purchase low-mileage 13BRE irons. Obviously, new irons from Mazda are...prohibitive.

So, basically what I'm getting at in this long post is - Will 13BRE irons make for a shitty N/A build compared to S4 or S5 irons? Are there high-quality S4 or S5 N/A irons available someplace that I overlooked that are not ridiculously overpriced? If I stick with N/A irons, would S4 or S5 be superior for these purposes?

(Edit) I'm aware of the 6-port differences. Cliffnotes:
Are there high-quality S4 or S5 N/A irons available? Not 100k+ blown engine ones - I've only managed to find very mediocre ones for sale at prices less than than 13BRE plates I have a line on.
If I stick with N/A irons, is S4 or S5 better?

keep in mind the intake is different on the RE vs the FC engines, so you a) cant mix them and B) need the RE or FD intake to actually use em.

I have no qualms in purchasing an intake, J9.

However, I just got very bad news. The center iron is completely unusable, I didn't bother speccing any irons beyond that - if one is unusable, the rest are garbage IMO.

What else is not interchangeable from FC to RE irons?

Dude they're completely different engines optimized for completely different uses... the RE is not designed for an n/a application. Yeah it's got bigger runners and throttlebody etc but what's the point on a non turbo, you might get 5 hp or something peak with a loss of low end. You will need RE manifolds, throttlebody, TPS, all sorts of shit. For hardly any benefit. And the throttlebody is on the wrong side for an n/a, so that's even more hassle for hardly any benefit.

Just keep looking for a 6 port. I know they're hard to find because there are no JDM ones available, but keep looking. Call around to a few shops. Find a low mileage block and rebuild that. N/A irons are engineered properly for a normal 90% street n/a application (duh). They're completely different than turbo irons and manifolds, and for a good reason.