Catch Can on ITBs
 

Morning all. Tried making threads in ClubRoadster since they have an ITB section but they seem dead. This forum and M.net are the only ones still populated, and I don't do social media.

I have a catch can I would like to incorporate with my ITB setup. The setup is from DanST with 45mm ITBs on the stock fuel rail. Under each runner there will be a 1/8th" barb, and those four lines run to a The 3/4-16 side of the vacuum block has an adapter to run anhttps://www.speedmaster79.com/Remote-Idle-Air-Control-Valve-and-Adaptor-Unit and all this is ran by a MS3PNP. The 4th runner has a port for the brake booster. I would like to run a catch can setup or at least something to help the crankcase out. I have seen various ways to do this but when it comes to ITBs there seems to be a bunch of info that clashes. I do know that venting the PCV into the vacuum block will just give a massive vacuum leak. Does having a line from the hot side and cold side of the valve cover to a vented catch can work sufficiently enough without vacuum? I would like some vacuum but it seems like I would have to go separate vacuum pump to get this option to work.

Can you vent it to the exhaust with one of those exhaust scavenge venturi fittings?

https://cimg9.ibsrv.net/gimg/www.mia...5d7c0640d5.jpg

Hmm, I may consider that and somehow incorporate it into the EGR bung. It looks like the plug for a 99-00 is M22x1.5. Would this be too close to the port or does it need to be further downstream? I do have 2 o2 sensor ports pre-cat and one post cat. M18x1.5mm if needed?

I run an OEM PCV valve into the vacuum block. What concern do you have with it being a vacuum leak? The PCV should close near idle and at full throttle. Even if it doesn't you'll be tuning for it and won't cause adverse effects.

Not sure if I can tune out a -8AN vacuum leak? Are you talking about using the stock PCV that is in the cold side of the valve cover? I am under the assumption that the PCV works as a vacuum pulls it open after a certain degree and the highest vacuum is at idle. Not sure how it could not open at idle and full throttle but open during cruise, or maybe how I am thinking is off.

I ordered another fitting to hopefully work, if it doesn't then I am going to grind the threads down and JB weld.

AFAIK the PCV valve does indeed mostly close at idle, but definitely not 100% closed. It's not wide open but you definitely will feel a slight suction out of it. Just my experience and understanding, could be wrong here! I ditched it on my turbo car.

Yes I’m talking about the cold side PCV valve. I’m assuming your vacuum ports are behind the throttles in your ITBs, and in that case it’ll behave as stock. Depending on how you plumb the hot side port then it may or may not be a leak. I left my hot side open to atmosphere with a catch can. As far as tuning the “leak”: you’re on an MS3, and presumably will run AlphaN or ITB Mode. The leak will be accounted for, and the only difficulty would be using the right size vacuum hose for your idle valve to have enough control, if you’re using one. I don’t really see how it would be an issue if you do use a PCV Valve.

what fire said is also my understanding. The idle vacuum should pull the PCV valve nearly closed. If you don’t have enough vacuum at idle then it may not work as expected. This also means that a malfunctioning PCV can cause high idle issues.

You might be overthinking this. Every car with a PCV has a vacuum leak. Just stick the catch can in between the PCV and vacuum block. If you want to do both sides of the valve cover to a vented catch can, do that instead.

Either way, when the engine is making the most amount of crankcase pressure, there is no vacuum available to pull any gases out of the valve cover or PCV, unless you can create a vacuum from an ancillary source. And on an ITB engine, cruising at highway speeds, you barely have any vacuum, or at least that's what my MS3 has been telling me.

And I wouldn't run a brake booster with ITB but if I did I would do it from the vacuum block and not from just one runner, but that's just my opinion.

Thanks for all the info guys, this seems to be the only active forum with a bunch of knowledge on the subject!
I may be overthinking this. Currently I have 2 catch cans available to install, both are single in-single out, and one has a breather filter. The breather filter would be used as both ports having air in (as the only difference between the in/out ports on the catch can is a baffle plate on the in).
I have two vacuum blocks available as well. I have a that I would prefer to use as my has VIBRANT embossed in white lettering and a single large port. My issue is that I would rather run the slim style as I can hook the brake booster to it as well as my https://www.speedmaster79.com/Remote-Idle-Air-Control-Valve-and-Adaptor-Unit, however the slim style has some stupid 3/4-16 UNF fittings on the side and I cannot find a 3/4-16 UNF Male to 5/8-18 Male fitting and I do not want to have a fitting adapted to a fitting adapted to a fitting. This brings me to the VIBRANT block, which has a single 3/8 NPT fitting which I am using for my IAC since I have ordered a 3/8NPT male to 5/8-18 Male adapter. However this leaves me no line for the brake booster, so it will get tied to the 4th runner and use a check valve in the line to the booster like the stock line does.

This is how I would LIKE to have it done:
https://i.ibb.co/jZZy7XD0/Untitled.png

If you don't like the looks of the vibrant block then don't install it where it's visible. No one would ever see my vacuum block as it's installed below the ITB manifold. I'm using a T3 manifold though and it puts the vacuum ports at the bottom of the manifold so that was an easy decision for me. Don't know if the UK manifold is configured like the T3.

The stock system might have the port for the booster on the 4th runner but that is still tied to the intake plenum which is quite a difference in vacuum source. Having just one runner for the brake booster just doesn't seem like it would work well enough consistently. There is just such minimal vacuum on one runner of an ITB engine aside from the fact that you already have a reduced vacuum signal to begin with. I don't think it would work well enough consistently but nothing wrong with trying. .

I am hoping the check valve will hold the highest vacuum pressure in the line for the brake booster, so if there is less vacuum before the check valve it should be fine. Again, I am just winging it right now. Information is few and far between. A lot of the miata ITB pictures I have seen all run this way or right into the vacuum block itself. DanST makes their manifolds with the BB hardline on the 4th runner which I kept. I may need to block it off if I run it to the vacuum block.

My manifold will also have 1/8th barbs put under each runner. With the 4 barbs and the IAC valve setup I am hoping to get decent MAP signal for the MS3 in ITB mode and still have idle control and any voltage spikes/AC etc settled. Don't want to run 1000rpm idle!

I would run the brake booster to your vacuum block personally. Last thing I'd ever want in a car would be inconsistent brake assist...

Hector and I have both been running an ITB car for quite a while, so we’re not guessing when we tell you to run the booster to the vacuum block. I wouldn’t trust running it off only one intake runner. I could send you a picture of how I did mine, but my ITBs have a built in vacuum manifold which is why I chose them. I get plenty of vacuum out of that that I feed a vibrant block from. You can find lots of pictures in my thread too

I can run the booster through the vacuum block, it will take my last port which is no problem. This means I will run both the hotside and coldside valve cover ports to a vented catch can as there will be no suction available. PCV will be deleted. I do not want to run an exhaust scavenge barb as I still have a cat and feel this would put more strain on it than needed.

Thanks guys, and redursidae, I am reading your thread now. Thanks for all the help!

Got the vacuum block set up, I spent WAY too much on getting a fitting that would adapt the block to the IAC.


https://cimg6.ibsrv.net/gimg/www.mia...4b74c1381b.jpg


Left nipple is to MAP
4 lower nipples to each ITB runner
Middle 3/8 goes to PCV, and to IAC
Right goes to Brake Booster

This way the booster sees vacuum as much as possible as it is "isolated" from the IAC somewhat. Now I need to figure out how to make this 4 wire IAC work with the MS3PNP Pro. Any ideas? The stock IAC wiring will not work.

Yeah you went form a PWM idle valve to a stepper valve. Not the easiest route if you have never done it before. Just follow the instructions in the manual for your firmware. It will tell you which outputs you can use and then the hard part of getting it tuned begins.

I went the easy route. I have the factory idle valve I took off a NB TB. JB welded some 3/8 hose barbs to it and called it a day.

Yeah I probably should have gone the easy way. I went this way for the looks, if I were to mount this under the manifold and never see it, I would have done the stock NB. I probably spent...no, I definitely spent more than $100 on fittings just to get it to work. I ended up getting a 3/8npt to -6an with 1/8npt T. Everything worked except the IAC side. It was really something like 5/8-18 or some junk, but no one makes a fitting for what I need, so the -6an got a healthy dosage of JB weld as well. You can't tell by the pictures, but it essentially made the T fitting permanent to the IAC housing adapter. This IAC is from a 1991 GMC Jimmy. I just want a civil 800rpm idle and compensation for electrical and AC load. The RX7 has a 1000 idle but it is with a OER 45 carb, I miss low idle and vowed to not budge on the miata.

Here is the part that shows the IAC for GM, the last one with the square plug:

https://cimg5.ibsrv.net/gimg/www.mia...ccebcc1279.jpg

Looks like I am going to use 30-33, but I am going to send an email to diyautotune to double check this will be correct. This is the output and it is showing additional spark for a v10:

https://cimg2.ibsrv.net/gimg/www.mia...3761cabb45.jpg
This is a MS3PNP Pro for my year but I think this was copy/paste on ampefi.

Double checking with DIYAuto is always a good idea. There are so many manuals floating around it can be quite confusing but honestly I don't think much changed on IAC stepper control outputs over the years.

It's funny how you want 800 rpm idle and I have mine at just over 1000. That has everything to do with engine mounts and a very old car than anything else. Anything below 1000 and the dash rattles drive me crazy. And the idle is 1200 with the AC on and yes I still have AC. I found anything less than 1200 rpm with the AC on doesn't get much cold air at idle on my car. Again, 25 years old and all that.

Best of luck, keep the thread informed with results, and don't forget to run the catch can between PCV and vacuum block.

Just an update, they have responded to my email about using the stepper instead of the stock PWM:

"I generally would not recommend this. On the NB PNPPro, the stepper outputs aren't brought out any external connectors on the PNP ECU, so the only way to access them is directly on the PNPPro module board, so I would advise sticking with the original style PWM idle valve rather than trying to change to a stepper-type."

I would like to use the stock PWM'd valve but it looks ugly when I am putting it on my distro block, which is why I would like to stick with the stepper. I inquired if it was something as simple as soldering wires to available pads in the MS3PNP Pro and running them out of the ECU, which I am comfortable with. I know I could have gone with a regular MS3 Pro but I like the PNP so I can have the option to return to stock if ever needed. I don't want to have to remove the OEM harness, and would rather just solder and run the 4 wires associated with the stepper than rewire the entire car.

you can hide the pwm idle valve like almost anywhere...