Lude Generation

While I was working on both cars over the weekend, I noticed differences in the vacuum hoses and on the inlet manifold.

Pics below (UKDM first, equivalent JDM after)










Annoyingly, neither the Honda manual or supplements for the 4th gen actually show the H22 inlet manifold So working off the H23 manifold in the main manual, it seems that my JDM is missing the "Air Boost Valve".

This is mounted on the front of the manifold on the right hand (timing belt) side, just to the left of the bypass valve actuator under the throttle cable. You can see it in pic 3, but on pic 4 there's a blanking plate instead. The blanking plate looks OEM style rather than a bodge up afterwards (it's cast) so I'm wondering if this is the way JDM 4th gens are meant to be?

As a result, the vacuum hoses are also different. There's 2 main changes that I'm interested in.

It's a bit difficult to describe, but on the UKDM there's a hose runs from the top of the inlet plenum (at the entrance to the throttle body) across the top of the manifold and then down to the "Air Boost Valve". You can see this in its entirety in pic 3. This pipe is not there on the JDM and the hole in the plenum is plugged.

The second change is around the routing of the breather hose that runs up from the intake resonator valve (I think? - it's the breather hose that runs along the plenum and disappears under the air box). You can see this hose clipped to the side of the plenum in pics 1 and 2 (clearest in pic 1).
On the UKDM, this runs straight up into the back of the throttle body at the top (pic 1). On the JDM, it goes into a T-piece under the plenum, and then 1 bit of this goes to the charcoal canister and the other bit goes up to the back of the throttle body at the top (pic 2).


Why am I bothered?
Partly curiosity, but mainly because the JDM has this problem where the idle drops too low on lift off, so before I go messing about any further on it, I want to know what is 'right' on these vacuum hoses.
If the UKDM is right, then I'll put the JDM back correctly before I go any further.

I'm sure the UKDM is 100% kosher (it runs fun and this car had pretty much fsh from Honda and hadn't been messed with like the JDM) but I don't know if JDM's are meant to be different in this regard - there are some other things that are meant to be different after all, like relocation of the fuel cut-off switch etc.


So what would be helpful please, is if JDM vtec 4th gen'ers could either;
Put up equivalent pics from their cars
Or
If you can't do pics but understand what the heck I'm going on about above confirm if it's like the first or second of each photo above please?

THANKS VERY MUCH!


(Also interested if anyone has any views why it would be different?)

never had a ukdm so cant really help with the difference's but heres a few pics of my jdm before i removed the engine last year, hopefully you can see what you need from them , if you cant let me know and ill take a few more as im not working till later on.

Great start, thanks for replying and taking the pics. The red pipes makes it really easy to see, too

There's no resonator pipe on yours, I'm guessing you've removed the resonator? Can you remember did it plug into where you have that white in-line connector? If so, that seems to match my jdm exactly.

Cheers

These pictures I took for someone else a couple of years ago.
I don't know whether they will help you at all but worth a try.

The symbols on each hose indicate where each end plugs into.

@wurlycorner, I've just been out and tried to replicate your photos on my BB4 for you:





Hope that helps

Guys that's fantastic, really thanks very much all have been very helpful +rep and much love all round

Ok, everything so far seems to confirm that the "Air Boost Valve" is a UKDM only thing so that shouldn't have anything to do with my idle problem (I now NEED to know what the hell that valve does though!!! Anyone know?)

@Pushki and @jjmartin349571could you please just check and answer one question for me, to complete the survey?
Pushki; the hose you have marked with the red flower, does that have a T-Piece in it with the extra hose from the 'T' going off along the inlet plenum towards the air-box?

JJ; I've copied one of your pics and drawn on it (please don't sue me for copyright )

can you please just check, does the hose I've highlighted red go down to a T-piece before it goes into the charcoal canister and does the extra hose off the T-piece go off towards the air box? (or have you removed the resonator and put a straight join in this hose to replace the 'T' at some point?)

You can see it in pic 3, but on pic 4 there's a blanking plate instead. The blanking plate looks OEM style rather than a bodge up afterwards (it's cast) so I'm wondering if this is the way JDM 4th gens are meant to be?

Yes all JDM vtecs (H22A1) all have the cast blanking plate

There's no resonator pipe on yours, I'm guessing you've removed the resonator? Can you remember did it plug into where you have that white in-line connector? If so, that seems to match my jdm exactly.

Yes white in line valve plugged into the air vaccum box thingy - if your removing the resonator you will need to plug that line before or after the white in line valve.

Think I've found a drawing that shows that hose and the 'T' piece;


But then it's missing off this one (should be on the hose highlighted red);


Can't find any damn reference to what the "Air Boost Valve" does in the manual, but it's clearly shown on page 9-2, it's clearly there on my UKDM and clearly isn't there on the JDM (not in the supplements either btw, as far as I can find)

vanzep wrote: Yes all JDM vtecs (H22A1) all have the cast blanking plate

vanzep wrote: Yes white in line valve plugged into the air vaccum box thingy - if your removing the resonator you will need to plug that line before or after the white in line valve.

Thanks Vanzep, so my JDM is plumbed in right. That's knocked one thing off the list then.

But there's definitely a discrepancy in the manual about the plumbing and about this extra valve on UKDM's (and presumably all H23's)?

yeah as far as i know this is a bit of a grey area - and no one really knows what that extra valve on the ukdm is for