Carb Devac a 1985 Honda CRX HF with Cal Emissions & A/C w/o Issues? - Fuelly Forums

Click here to see important news regarding the aCar App

Go Back   Fuelly Forums > Fuel Talk > General Fuel Topics
Search Today's Posts Mark Forums Read Click Here to Login
Reply
 
Thread Tools Display Modes
 
Old 07-25-2018, 08:37 AM   #1
Registered Member
 
Join Date: Feb 2016
Posts: 11
Country: United States
Location: Seattle, WA
Carb Devac a 1985 Honda CRX HF with Cal Emissions & A/C w/o Issues?

Any tips on a Kiehn Carb DeVac for 1985 Honda CRX HF (1.5 liter) with California emissions & air conditioning?

I want to keep the A/C & the 3 barrel carb has been rebuilt with a new insulator plate.

Any way to reduce MPG loss or to improve it with carb devac?

Note: My 1985 CRX HF, even with CA emissions does not have the oxygen sensor & nor does the 1984 CRX, however the 1986 & 1987 CRX's do.

Would I need to retain any of the black boxes for running the A/C w/o any issues? If yes, which black box?

I don't reside in CA, so the CRX HF is exempt.
__________________

ascendedmind is offline   Reply With Quote
Old 07-26-2018, 08:42 PM   #2
Registered Member
 
Join Date: Jul 2018
Posts: 7
Country: United States
A lot of the many vac lines on the 1st Gen CRX/3rd Gen Civic have to do with the EGR valve and other parts of the Federally required emissions control systems. Just so you know, it's a violation of US Federal law to tamper with or remove any factory installed emissions control systems on a vehicle which is driven on any public roads.

As for the AC, there is a idle speed boost system that uses vacuum lines and control valves to bump up the idle speed when the AC is on.You could probably delete it, unless you want a perfect idle speed, while the AC compressor cycles on and off.

In my opinion there's a lot you can do to improve the MPGs, but not much if you want to follow Federal law. The intake manifold is horrible, not sure if trying to port it would be worth the trouble. I especially don't like the idea of coolant heating up parts of the manifold. I'd rather have an electric heating element system to keep the plenum just above the icing temperature. I'm not a fan of catalytic converters or EGR systems either. I think you can get by with a tiny ND alternator from a Yanmar engine. I've used a small lawn mower battery, without a problem.

Upgrade your front end to the '84-'85 JDM pop up headlights or the '86-'87 aerodynamic headlights. Run the '86-'87 HF super lightweight aluminum rims. The '86-'87 49 state HF used a roller cam. The lean burn system in '86-'87 49 state HF uses a 5 wire oxygen sensor, which of course is no longer available from Honda or NGK
__________________

GasSavers_SWFL is offline   Reply With Quote
Old 07-26-2018, 08:58 PM   #3
Registered Member
 
Join Date: Feb 2016
Posts: 11
Country: United States
Location: Seattle, WA
Want to remove unwanted emissions to improve MPG

I'm with you, is there a compatible intake manifold which would work? Do you recommend using the stock rebuilt 3 barrel carburetor? I'm looking for maximum reliability with great MPG. This year CRX HF does not have either an oxygen sensor or catalytic converter.


I have the following rims:

92-95 Honda Civic VX Alloy Wheels/Rims Center Caps 13x5 4x100 45mm offset, 9lbs





What do recommend for the air to fuel ratio after carb devac? Will it require re jetting the 3 barrel carb? Parts are hard to find







Quote:
Originally Posted by GasSavers_SWFL View Post
A lot of the many vac lines on the 1st Gen CRX/3rd Gen Civic have to do with the EGR valve and other parts of the Federally required emissions control systems. Just so you know, it's a violation of US Federal law to tamper with or remove any factory installed emissions control systems on a vehicle which is driven on any public roads.

As for the AC, there is a idle speed boost system that uses vacuum lines and control valves to bump up the idle speed when the AC is on.You could probably delete it, unless you want a perfect idle speed, while the AC compressor cycles on and off.








In my opinion there's a lot you can do to improve the MPGs, but not much if you want to follow Federal law. The intake manifold is horrible, not sure if trying to port it would be worth the trouble. I especially don't like the idea of coolant heating up parts of the manifold. I'd rather have an electric heating element system to keep the plenum just above the icing temperature. I'm not a fan of catalytic converters or EGR systems either. I think you can get by with a tiny ND alternator from a Yanmar engine. I've used a small lawn mower battery, without a problem.

Upgrade your front end to the '84-'85 JDM pop up headlights or the '86-'87 aerodynamic headlights. Run the '86-'87 HF super lightweight aluminum rims. The '86-'87 49 state HF used a roller cam. The lean burn system in '86-'87 49 state HF uses a 5 wire oxygen sensor, which of course is no longer available from Honda or NGK
ascendedmind is offline   Reply With Quote
Old 07-27-2018, 06:46 AM   #4
Registered Member
 
Join Date: Jul 2018
Posts: 7
Country: United States
There is supposedly a JDM CVCC fuel injected engine, EW5 I think, that should have a better manifold. I've never see one, so no idea. I wanted to try to make a manifold by using aluminum tubing, but there's not a lot of room to work with.

There's nothing wrong with the original carb, if it's working OK. Make sure the vacuum secondary is working. The Canadian Civics and maybe others used a manual choke, which would reduce some vacuum lines. I would want the oxygen sensor system, as it helps to lean out the F/A mixture for better fuel mileage. It uses a frequency valve to add extra air past the carburetor to lean the F/A mixture. The wide band 5 wire oxygen sensor in the 49 state HFs does it even better.

Years ago I had an 1987 Cali DX with AC that I added a Cali HF head (no roller cam) and built a trans using an '84-'85 2WD wagon mainshaft (thinner gears and lower ratio 1st and 2nd gears) with a HF .66 5th and a Cali HF finial drive. I had the original DX carb that I rebuilt and a new 1 wire oxygen sensor. I used an OE cat that the brick broke apart and fell out and an EGR valve that I found which was rusted closed. I used an AEM cam gear set for maximum advance. K&N filter. Side exit exhaust with no muffler. I had like 30-40 different distributors from every 1st Gen CRX/3rd Gen Civic version I could find in the wrecking yards. I tried them all and don't remember which one I used. I ran 165 80 13" tires on '86-'87 HF rims. I also had an aftermarket cruise control system. I had an HF front bumper/air dam and a '85 Si rear hatch with the duckbill rear spoiler.

In normal (usual aggressive and high speeds in Cali) freeway driving I would get like 44-45 MPGs without the AC and as low as 40-42 MPGs with AC on. This was driving at 75-85+ MPH, usually with plenty of lane changes. A few times I drove on 55 MPH freeways at a steady 60 MPH with the cruise control on and would get a consistent 63 MPGs. This was with cheap ARCO 10% ethanol fuel. I calculated my MPG with a calculator doing 3/4 tank fill ups, with the CRX pointed downhill and the driver side uphill. I would always top off the tank and usually used only a couple of gas stations. Fuel prices fluctuated a lot back then, so I carried fuel cans and smuggled fuel from other counties and a boarder state. I used Redline oils.

You can't easily rejet these carbs as most of the jets are pressed in. About all you can do is use wire drills to enlarge them or try to drill them out and tap the holes for threaded jets. Not sure how you could read spark plugs on a CVCC engine. Not sure if there's an easy way to do a better tuning job than the Honda engineers did. The idle mixture can be adjusted if you remove the tamper proof plug and cut down a screwdriver. You need a propane cylinder and a tachometer to read while adjusting the mixture. Make sure your float level is correct. I drilled a hole in my air cleaner base, so I didn't have to remove it. Also check that the mechanical and vacuum advance is working on the distributor. Check your valve adjustment and the cylinder compression.

That's cool the VX rims are that light weight. The HF rims are like 13 lbs IIRC. I prefer how the HF rims look.
GasSavers_SWFL is offline   Reply With Quote
Old 07-27-2018, 12:10 PM   #5
Registered Member
 
Join Date: Feb 2016
Posts: 11
Country: United States
Location: Seattle, WA
3 Barrel Carburetor A/F Ratio Tips?

Thank you, I hope you don't mind the questions. I just want to devac the CRX HF w/o any negative issues. I want this to be a reliable daily driver with few mods as possible.



Is it a challenge to tune the Devaced 1985 HF carburetor? Any idea what the stock A/F ratio was for the 1985 Honda CRX HF for maximum MPG?



What kind of garage or shop if any would you definitely recommend using for tuning the Devaced 1985 HF carburetors A/F? This would seem to be a real challenge finding. such..


I'm not mechanically inclined. I referred my mechanic to the devac tutorial on redpepperracing.com



I was told the stock carburetor would never run right on the 1985 CRX HF as a daily commuter as the carb was designed to run with the black vacuum boxes or emissions for correct A/F ratio. I just want to avoid removing the wrong vacuum lines.


Are there simple adjustments you can make on the carburetor using a wideband or A/F meter to fine tune the carburetor, after it's been devaced?
ascendedmind is offline   Reply With Quote
Old 07-28-2018, 12:15 AM   #6
Registered Member
 
Join Date: Jun 2017
Posts: 598
Country: United Kingdom
Location: Kirkcaldy
I am intrigued by this thread. What the hell is a Devac?
__________________
2006 Honda Jazz 1.2i-DSi S Vivid Blue Pearl
JockoT is offline   Reply With Quote
Old 07-28-2018, 12:35 PM   #7
Registered Member
 
Join Date: Feb 2016
Posts: 11
Country: United States
Location: Seattle, WA
Quote:
Originally Posted by JockoT View Post
I am intrigued by this thread. What the hell is a Devac?

Its when virtually all the vacuum lines are removed from the Honda CRX carburetor, regarding this case.
ascendedmind is offline   Reply With Quote
Old 07-28-2018, 03:11 PM   #8
Registered Member
 
Join Date: Jul 2018
Posts: 7
Country: United States
Quote:
Originally Posted by ascendedmind View Post
Thank you, I hope you don't mind the questions. I just want to devac the CRX HF w/o any negative issues. I want this to be a reliable daily driver with few mods as possible.



Is it a challenge to tune the Devaced 1985 HF carburetor? Any idea what the stock A/F ratio was for the 1985 Honda CRX HF for maximum MPG?



What kind of garage or shop if any would you definitely recommend using for tuning the Devaced 1985 HF carburetors A/F? This would seem to be a real challenge finding. such..


I'm not mechanically inclined. I referred my mechanic to the devac tutorial on redpepperracing.com



I was told the stock carburetor would never run right on the 1985 CRX HF as a daily commuter as the carb was designed to run with the black vacuum boxes or emissions for correct A/F ratio. I just want to avoid removing the wrong vacuum lines.


Are there simple adjustments you can make on the carburetor using a wideband or A/F meter to fine tune the carburetor, after it's been devaced?
No problem. It sucks there's nothing much written about these awesome cars, other then how to install 1st Gen Integra stuff for better performance. These fine cars usually didn't get modified for better fuel economy and most knowledge of stuff like that was lost before Al Gore invented the internet.

I don't see why you can't remove most and maybe all the vacuum controls and have a decent running car, as long as you do it properly. Remember that all the CVCC engines are lean burn by design and the factory single row radiators are undersized. I plan to run a full sized radiator that I'm going to convert to double row. It wouldn't be too hard to damage the engine by running it too lean and/or with too much ignition timing. Remember also that most places only sell E10 fuel. In stock form with everything working, these cars are 100% reliable. I put over 300,000 miles on these cars years ago. I did all my own work and even passed the BS Cali emissions tests.

The only tuning you can easily do to these carbs is the idle mixture, which requires a propane cylinder and a tachometer. I think it will be harder to tune your's because you don't have the oxygen sensor system, which automatically adjusts the A/F ratio. Remember that these carbs are really 2 separate carbs built into 1, but linked together. You have a small single barrel carb that feeds the prechambers with a rich A/F mixture. Then you have a 2 barrel vacuum activated carb that feeds a lean A/F mixture to the rest of the cylinders.

Carbs for cars don't put out a static A/F ratio. You have a idle A/F ratio, a low speed or transition A/F ratio and a WOT A/F ratio. In addition, these cars use an acceleration pump called a power valve to prevent stumbling when the gas pedal is mashed down. It dumps a bit of extra fuel.

Pretty much impossible, even if you live in a big city. Almost all the old school mechanics have been replaced by lower skilled "technicians". You'd have to find someone who has done this before and hopefully on his own car as a hobby. Remember what you want to do is illegal in every state.

Those scary black boxes are just containers for the vacuum switches and valves. You might want to keep some of them, especially if you want good driveability.

I'm not sure if using a normal wideband will work for tuning, because of the CVCC.

I'd recommend buying a used factory service manual. Every part of the emissions control system is shown via a detailed schematic drawings. I'll take a look at my Civic manual and give you some tips. Off the top of my head, the EGR should be easy to delete, with no ill effects. I have 2 HFs and plan on deleting as much as possible and see how much it helps.

Why do you want to devac your CRX? Just for looks?
GasSavers_SWFL is offline   Reply With Quote
Old 07-28-2018, 04:34 PM   #9
Registered Member
 
Join Date: Feb 2016
Posts: 11
Country: United States
Location: Seattle, WA
Tutorials for CRX Carb Devac

Here's hard to find info:


Honda CRX Devac Write Up


I Devaced! - General Posts - Red Pepper Racing


Devac Write Up. - Carbs - Red Pepper Racing
__________________________________________________ ____________
Are you aware of any tutorials on on how to use a propane cylinder and a tachometer for tuning this carburetor?



I do have the Honda CRX factory service manual.



Any specific must read pages I must read regarding removing emission controls from my HF with CA emissions? (I want to keep the A/C)


Can an oxygen sensor system be added to my carburetor, to automatically adjusts the A/F ratio?


Why do I want to devac my CRX? I really don't want to, however there are to leaky or broken parts, which are parts for CA emissions & are different from the non-CA emissions CRX's See attahed photos.



Btw, where are you located? I'm located in Seattle-Tacoma area.




Quote:
Originally Posted by GasSavers_SWFL View Post
No problem. It sucks there's nothing much written about these awesome cars, other then how to install 1st Gen Integra stuff for better performance.



These fine cars usually didn't get modified for better fuel economy and most knowledge of stuff like that was lost before Al Gore invented the internet.

I don't see why you can't remove most and maybe all the vacuum controls and have a decent running car, as long as you do it properly. Remember that all the CVCC engines are lean burn by design and the factory single row radiators are undersized. I plan to run a full sized radiator that I'm going to convert to double row. It wouldn't be too hard to damage the engine by running it too lean and/or with too much ignition timing. Remember also that most places only sell E10 fuel. In stock form with everything working, these cars are 100% reliable. I put over 300,000 miles on these cars years ago. I did all my own work and even passed the BS Cali emissions tests.

The only tuning you can easily do to these carbs is the idle mixture, which requires a propane cylinder and a tachometer. I think it will be harder to tune your's because you don't have the oxygen sensor system, which automatically adjusts the A/F ratio. Remember that these carbs are really 2 separate carbs built into 1, but linked together. You have a small single barrel carb that feeds the prechambers with a rich A/F mixture. Then you have a 2 barrel vacuum activated carb that feeds a lean A/F mixture to the rest of the cylinders.

Carbs for cars don't put out a static A/F ratio. You have a idle A/F ratio, a low speed or transition A/F ratio and a WOT A/F ratio. In addition, these cars use an acceleration pump called a power valve to prevent stumbling when the gas pedal is mashed down. It dumps a bit of extra fuel.

Pretty much impossible, even if you live in a big city. Almost all the old school mechanics have been replaced by lower skilled "technicians". You'd have to find someone who has done this before and hopefully on his own car as a hobby. Remember what you want to do is illegal in every state.

Those scary black boxes are just containers for the vacuum switches and valves. You might want to keep some of them, especially if you want good driveability.

I'm not sure if using a normal wideband will work for tuning, because of the CVCC.

I'd recommend buying a used factory service manual. Every part of the emissions control system is shown via a detailed schematic drawings. I'll take a look at my Civic manual and give you some tips. Off the top of my head, the EGR should be easy to delete, with no ill effects. I have 2 HFs and plan on deleting as much as possible and see how much it helps.

Why do you want to devac your CRX? Just for looks?
Attached Thumbnails
Click image for larger version

Name:	Big_1_For_1985_CRX_HF_vacuum_lines_.jpg
Views:	14
Size:	109.8 KB
ID:	2550   Click image for larger version

Name:	Big_2_For_1985_CRX_HF_vacuum_lines_.jpg
Views:	14
Size:	105.3 KB
ID:	2551  
ascendedmind is offline   Reply With Quote
Old 07-28-2018, 06:58 PM   #10
Registered Member
 
Join Date: Jul 2018
Posts: 7
Country: United States
No. I just followed the FSM's procedure. I used a propane torch that I put a rubber hose over the end. I had a timing light with a digital tach on it. The biggest hassle was cutting down a screwdriver to fit between the carb and the firewall. Since I'm going to do all that over again, I might make some videos.

Just the carburetor and emissions control system sections. That will show you what everything does.

The oxygen sensor system doesn't attach directly to the carburetor. It goes on the intake manifold and of course you need the O2 sensor in the exhaust, preferably as close to the factory location. Remember that the oxygen sensor system is very limited in the A/F range it can adjust for. Your carburetor and intake manifold stuff still has to be pretty close to where it's supposed to be.

Depending on how you like to drive, you might want to run a different exhaust manifold or even headers, if you can find them. The Canadian exhaust manifold is a long cast iron tri y set up, which probably flows pretty good.

Why don't you post up a few pics of what's wrong with your vacuum line stuff and your underhood emissions label. I might have some spare parts.

I'm in South West Florida. No emissions testing in WA?
__________________

GasSavers_SWFL is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Fuelly iOS Apps
» Fuelly Android Apps
Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 11:33 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.