I've searched high and low ALL OVER the internet and can't, for the life of me,
find ANY definitive answers to this question:

What (SPECIFICALLY) are the differences between the F23a1 and the F23a4 Intake Manifolds?



And please don't tell me what you THINK they are or MIGHT be. Just stick to the FACTS... Please
Thanks in advance...

 

F23 a1:
The intake system was simplified in shape to reduce induction resistance and noise. A larger twin-chambered air box designed to dampen resonant intake tract noise replaces the previous Accord's smaller, single-chamber damper. The new box is 10.7 liters in capacity, compared to the older unit's 8.2 liters. The larger box also elimi-nates the need for a second resonant-frequency damper and an additional side branchThe 2.3-liter Accord 4-cylinder engine intake manifold has been redesigned to add more power and lower emissions. The individual cast-aluminum runners have revised dimensions to better take advantage of the different air-flow characteristics of the 2.3-liter engine. A larger plenum chamber reduces induction noise and the incorporation of EGR (Exhaust Gas Recirculation) ports into the plenum, upstream of the throttle plates, eliminates the need for a separate fitting and port in each intake runner.
F23a4:
This engine was used in the 1998-2002 Honda Accord ULEV models. It is substantially similar to the F23A1, but features ULEV certification with a slight reduction of power: 148 hp (108 kW) with a maximum torque of 150 lb·ft (203 Nm). This engine has a different exhaust manifold, a more restrictive intake manifold and cylinder head, and a 32-bit ECU which uses an AFR (Air Fuel Ratio) oxygen sensor when compared to the F23A1

got this off wiki

So really the difference is a more restrictive intake manifold

 

@GWAR

First let me say thank you for the reply. I appreciate that. I have read that same wiki on the F-series motors and maybe I should've been more specific with my original question because that's EXACTLY what I've been trying to figure out: How, exactly, is it "more restrictive"? Is it the airbox or is it the actual plenums (upper/lower)? If it is the upper/lower plenums are they overall the same size and just cast different internally? In which case they could be bored out to be the same size as the F23A1's? Or is the whole thing smaller, hence more restrictive? Is there anyone who might know how many cubic liters (or however they measure it?) of air each one can take in respectively? Maybe that's the question I should be asking? I've just heard so much about doing this swap onto other F-series motors but the F23a1 manifold isn't always the easiest to find at my local pick-n-pull. BUT there are quite a few F23a4's and that's why I've been so pressed to find out the actual difference. At any rate bro THANK YOU again for your reply because so far, you sir ARE the ONE and ONLY

 

I have seen both at the salvage yard I work at. Everything about the f24a4 parts are physically smaller. So F23A4 is junk for parts, except a block. The intake and exhaust manifolds are very small In comparison to F23A1.

The F23A1 has a very simple 2 piece intake manifold. It reminds me of a d16y8 manifold but bolted together in 2 parts.

On a side note the 1998 odyssey has an F23A6 which has the good intake, its the same as F23A1.