94eg!

iTrader: (2)

***edit (See post on previous page too)

Honestly I'm still worried this is going to create a large vacuum leak when the OBD1 ECU tries to operate the OBD2 solenoid. The 96+ manuals all use the word "duty" when describing the solenoid operation. This makes me think it's more complicated than the simple "Constant ON" you have with the OBD1 solenoid. But I will try it out and let you know.

***EDIT again: Apparently the EVAP solenoid is a source of problems on OBD2a cars that convert to OBD1 ECUs (which is essentially what we're building). The OBD1 ECU opens the EVAP solenoid right after cold-startup (OBD2 does not). Allegedly this causes engine bogging issues.

94 Civic Si

Thanks Mate!

94 Civic Si

I hear you brother, but again, here is the description from the '96 Integra manual:


It sounds like you will beat me to this - out of necessity if you are getting over 100 degrees out there now. We'll see what happens...

94eg!

iTrader: (2)

So the OBD2a Tennex canister arrived today and I can tell you for sure it is identical to the EG canister. When comparing it to my OBD1 Tennex canister it's literally identical right down to the casting marks and text. It's just been modified to remove the diaphragm valve on top.

The only thing you will probably need to do is shave off the two little prongs on the bottom port so your EG's fresh-air hose will slip on. The OBD2a canisters use a snap-on fitting to connect to the fresh air hose.

BTW: it's supposed to be 116* out this Tuesday and Wednesday. 😭

94eg!

iTrader: (2)

Bad news. OBD1 purge valve works the opposite of OBD2 purge valves. OBD1 valve is open without power. OBD2 valve is closed without power. This made the car start up weird and idle like it had a vacuum leak until the engine warmed up. At that point, the ECU shut off power and closed the OBD2 purge valve and no more fumes were pulled into the engine.

- OBD1 ECU provides power to solenoid to keep it closed until the engine warms up.
- OBD2 ECU doesn't turn on the power till after the engine warms up.

This setup doesn't work with an OBD1 ECU. Sorry.

94eg!

iTrader: (2)

I just realized that your system (the way you currently have it hooked up) will NOT be operating correctly either. Using an OBD2 purge valve to operate the OBD1 canister means you are only purging during warm-up (just without the vacuum leak). Once the engine is to temp, the OBD2 valve closes. If you remove the hoses for the purge valve, you can hook the 8mm vacuum port on the manifold directly to the tiny "signal" port on the top of the OBD1 canister. This will give you full-time purging, just like the JDM type-R has (whenever the motor is on, the system is purging).

Use one of your long 8mm purge hoses and connect the 8mm vacuum port on the manifold directly to the tiny port on top of your OBD1 charcoal canister. You can either get a plastic adapter to connect the two hose sizes, or just shove the tiny #7 hose down inside the larger one. If you want a new length of 8mm hose, O'Reilly's sells Gates 27003 fuel hose for $1.49 / foot. This is what I used and it worked perfectly (even with a piece of #7 hose inside it lol).

You will have to leave the purge solenoid plugged into your harness to avoid a check engine light. It just won't be hooked up to anything. Keep in mind this won't pass an inspection, but you can always swap the hoses temporarily if you need one.

94 Civic Si

Jinkees! You pieced together some good info there. I am running two separate hose adapters to connect the solenoid to the tiny port on top of the diaphragm, and then another one to connect the purge port on the can to my throttle body. I will try bypassing the solenoid as you describe above the go from there.

I guess I see why they are powering the solenoid to keep it closed - if something failed it would be better to default open.

The fact that they have this many changes over a few years ('94 to '98) tells me that it is not a slam dunk to deal with the fuel vapors from a gas tank...

How is yours working now? Doing okay on the purge & vapors with +100 degree temps?

94eg!

iTrader: (2)

NO!

In the extreme heat both my CRX and my Civic are having weird issues. I'm probably not going to be driving them very often this summer.

Hopfully getting yours hooked up directly gets the system purging enough to keep fumes out of YOUR cabin.

94 Civic Si

Thanks! I will be able to do some checking on this over the weekend...

Sorry to hear about your issues.

94eg!

iTrader: (2)

You would never guess, but it turns out the EVAP system is the cause of the hesitation I've been experiencing in my 89 CRX for over 15 years! Whenever I drive in the heat (101*+) that car would start bucking around 2k rpm. I've replaced everything on that motor and even completely rebuilt the top-end.

All this work and speculation about the EG's EVAP system got me thinking....what if excess tank pressure was causing this. Sure enough, I loosened my gas cap and drove 20 miles home in 113* weather without a single hiccup! I couldn't believe it. Now I just need to test every component of that car AND the Civic to see if 20+ years of topping off the fuel tank has finally caught up with me. I tell you what...I'll never top off a tank again. From now on I take the pump out once it shuts off the 1st time.

wxman94ej1

I hold a similar belief that strange issues I have with low idle are related somehow to vacuum in the fuel tank. I'm not sure on the CRX but on the 92-95 Civic and 94-01 Integra, there is also another two-way valve with a diaphragm that controls the release of vapors/pressure from the tank to the charcoal canister via the vent hardline under the car and it is actually located on the fuel tank under the car. It's not powered, it's simply some sort of diaphragm. I have a brand new two-way valve sitting in my garage to install to see if this helps with these issues. I also have trouble below 1/2 tank of gas with a longer crank time, and notice that when I remove my fuel cap to re-fuel, there is either a lot of air going in or coming out indicating to me that the pressure inside the fuel tank is not being controlled properly somehow.

Here's the valve I'm talking about from another thread:
https://honda-tech.com/forums/honda-.../#post51284188

94eg!

iTrader: (2)

Yes the CRX EVAP system is identical in operation to the EG. The 2-way valve serves two purposes....

- allow mild pressure of 0.2 to 0.6 in-HG (about 0.1 to 0.3 psi) to build and then vent excess fumes (to the charcoal canister)
- allow mild vacuum 0.4 to 1.4 in-HG (about 0.2 to 0.7 psi) to build and then draw fresh air into the fuel tank (from charcoal canister)

It's also first in line for contamination, should liquid fuel enter the EVAP system.

***edit: The only problem with attempting to test the 2-way valve per the manual, is that you would absolutely NEED a special low-pressure gague to take such measurements. A 3psi gauge is $40 on amazon. And then you also need the hand pump to use it. It's cheaper to simply buy a new valve.

Replacing it on the EG is really easy. It's just hiding behind a plastic cover. The bolt can easily be removed with a small wrench even though it's on the top-side.

94 Civic Si

94 Civic Si

Did you ever try any mild pressure through your replacement valve?

94 Civic Si

I got a second to check on this a little at lunch time, here is what I know:

- engine "cold" (it is 92 degrees here), IGN off, my OBD2 purge solenoid is closed
- engine cold, IGN on, purge solenoid is open
-I will test solenoid function when engine hot and IGN on when I get home from work. If solenoid is closed as we suspect, I will hook it up as you describe below similar to JDM Type-R for the full time purge.

Thanks.

94 Civic Si

When the engine is running at normal operating temp, my OBD2 Evap Purge Solenoid is CLOSED, so it would not supply manifold vacuum to open my OBD1 diaphragm on the charcoal canister.

I routed the manifold vacuum direct to the can's diaphragm, bypassing the solenoid, via the hose adapter, and left the can's Purge line connected to the TB - everything works! No smell, no stumble, no CEL.

Who knew it would be this big of a PITA?!?

TomCat39

Could always use a relay.

OBD1 ECU Powers relay to keep relay open, hot lead to open legs of relay to solenoid. As long as OBD1 ECU provides power, relay does not provide power to solenoid. Once OBD1 cuts power off, relay closes and lets hot lead pass power to the solenoid.

Not sure off the top of my head what relays in the honda are normally closed and switched to open with power to the magnet side. But that's the kind of relay needed to reverse switch your ECU. I am also not sure if the ECU provides enough current for the solenoid to flip a relay.

wxman94ej1

Gah, I am terrible at following up on stuff. Yes, I took the valve out of it's bubble wrap bag and blew into a few of the ports. I was reluctant to do this because I don't want to mess up the diaphragm in there. Based on what I was able to observe, it was difficult to gauge what exactly was going in when I blew into both ports and sucked air out of both ports. I will double check again and write some notes this time so it is actually helpful instead of "yeah I tried but I don't remember"! I'll try and get around to it soon.

94eg!

iTrader: (2)

I just experimented with three of these 2-way valves, and here is my observations.... BTW: It's okay to blow into them...

Blowing out from the tank requires mild pressure. New was smooth, 89 and 94 both made a noise.

sucking into the tank was easy on all 3.

Blowing into the tank was easy on all three.

Sucking out of the tank didn't work on all 3.

One thing I found very interesting was to blow air (with my mouth) into the tank through the 2-way valve. With the gas cap on, you can easily pressurize the tank. Then when you let go, listen to the valve operate as it regulates the air coming back out (beware of harsh fumes).

Also it's interesting how air blows or bubbles out the filler neck if you have the gas cap off.

94 Civic Si

We wrapped things up pretty well on the topic of evap purge and charcoal cans: https://honda-tech.com/forums/honda-...-fuel-3150846/

Now onto the idea of getting an exhaust I like a little bit better. I have an Aero Turbine on there now, but it is a little louder than I prefer...

94eg!

iTrader: (2)

I managed to cobble together a bolt-on OEM Type-R system for my 94 hatchback with b-series.

- Any header with 2.5" collector (I have a PLM Narrow)
- JDM DC2 Type-R 2.5" catalytic converter
- JDM DC2 Type-R B-pipe (96-spec has 2 resonators, 98-spec has 3)
- JDM EK9 muffler

Now I can sneak out of the garage at 5:30am without waking up the wife & kids (and neighbors).

94 Civic Si

This topic came up today - rear mount turbo: https://honda-tech.com/forums/search...rchid=20409258

It might be interesting to have some FI power, but I like having the AC work, plus the PS....

94 Civic Si

eBay?

94eg!

iTrader: (2)

I got the muffler from Lings Honda parts in the UK. Was cheap but Took 4 months to get from Japan to the UK, then 4 days to the US. The B-pipe & cat came from H-motors-online. The header I got on ebay.

tony_2018

rear turbo mount might not work, no room for intercooler piping.

if this were a truck yeah , plenty of room to not worry about damaging the pipes.