Converting '86 HF (carb) to fed VX (efi). - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 02-13-2008, 01:58 PM   #1
Registered Member
 
Join Date: Sep 2007
Posts: 21
Country: United States
Converting '86 HF (carb) to fed VX (efi).

Well, I've had it with the carb. Fussy and unreliable. Tried a rebuild -- still not acceptable. Going to change out the carb to federal VX efi. If anyone has done a similar conversion, I'd appreciate any advice or warnings.

Thanks!
Colby
__________________

Colby is offline   Reply With Quote
Old 02-13-2008, 02:11 PM   #2
Registered Member
 
GasSavers_Erik's Avatar
 
Join Date: Nov 2006
Posts: 1,027
Country: United States
Are you replacing the whole engine or just trying to put a VX EFI intake on it? If its a CVCC engine you will have to change over the cylinder head as well

This is going to be a big job- wiring harness, ECU, fuel pump etc.

I have had good luck with my 87 1.5 CVCC carb. I rebuilt it myself last year even though it was running fine then. What is the problem with it? Rough idle, poor acceleration, hard starting when hot/cold?

There are tons of vacuum hoses- it could just be a rotten hose somewhere.
__________________

GasSavers_Erik is offline   Reply With Quote
Old 02-13-2008, 02:42 PM   #3
Registered Member
 
Join Date: Sep 2007
Posts: 21
Country: United States
I'm going to go with one more rebuild (since it has a lifetime warranty), and replace all the vacuum lines in case there is a leak or blockage somewhere.

The past carb was dumping too much fuel at low rpm (bad mileage), and the current rebuild bogs hard at anything past 1/3 throttle.

Why would I have to change heads?

I could just fab an intake manifold and mount the injectors in the runners. I know it's a big job but this carb crap is driving me to the breaking point.
Colby is offline   Reply With Quote
Old 02-13-2008, 03:13 PM   #4
Registered Member
 
GasSavers_Erik's Avatar
 
Join Date: Nov 2006
Posts: 1,027
Country: United States
If you have a CVCC engine, the cylinder head is special and actually requires two seperate mixtures a rich and a lean mix in order to work correctly- it would be impossible to get a stock ECU to work with this.

The easiest way to tell if you have a CVCC engine is if you have a 3 barrel carb. The tiny carb barrel feeds the extra rich mix to a tiny pre combustion chamber that the spark plug screws into.

Will the engine rev up OK in neutral? Double check the ignition timing and the vacuum hoses. It could be a bad/clogged accelerator pump or a bad power valve in the carb.
GasSavers_Erik is offline   Reply With Quote
Old 02-13-2008, 03:25 PM   #5
Registered Member
 
Join Date: Sep 2007
Posts: 21
Country: United States
It's an '86 HF with stock D15a2 (plastic valve cover).

CRX HF (USA) D15A2 1.5 8V SOHC 2bbl Carb 1488 58hp@4500rpm 80tq@2500rpm

It is unlikely to be a CVCC.
Colby is offline   Reply With Quote
Old 02-13-2008, 03:51 PM   #6
Registered Member
 
mrmad's Avatar
 
Join Date: Mar 2007
Posts: 386
Country: United States
If you're really serious about this, I'd recommend using megasquirt. I doubt that any existing (stock) Honda ECU would be properly tuned for your HF engine once you have done the conversion. The Megasquit will give you the flexibility to tune the engine once you're done.

Check out this section of the online manual. It goes into detail on how to covert a carburated car to EFI. More work then I would want to do, but if you do, lety us know.

http://www.megamanual.com/v22manual/minj.htm
mrmad is offline   Reply With Quote
Old 02-13-2008, 04:07 PM   #7
Registered Member
 
Join Date: Sep 2007
Posts: 21
Country: United States
Now that I think about it, you're probably right. The main hurdle I'm seeing is the lack of Vtec for the ECU. However, if it's only an output then perhaps it could just be ignored(?). I'll have to research the VX ECU and see what inputs it is expecting.
Colby is offline   Reply With Quote
Old 02-13-2008, 04:31 PM   #8
Registered Member
 
mrmad's Avatar
 
Join Date: Mar 2007
Posts: 386
Country: United States
The VX ECU probably wouldn't work as it changes the entire fuel map and ignition advance when the vtec kicks in the other 8 intake valves. If you want more info, check out pgmfi.org, these people have dedicated their lives to reverse engineering Honda ECUs.
mrmad is offline   Reply With Quote
Old 02-13-2008, 05:18 PM   #9
Registered Member
 
Join Date: Sep 2007
Posts: 21
Country: United States
Yeah, the EFI from the 2nd gen HF would probably be a lot easier. I just wanted to go with the VX for the lean-burn.

Thanks for that link!
Colby is offline   Reply With Quote
Old 02-13-2008, 07:18 PM   #10
Registered Member
 
mrmad's Avatar
 
Join Date: Mar 2007
Posts: 386
Country: United States
The advantage of using the megasquirt is you could program in something similar to a lean burn. The 2nd gen HF ECU is not very easy to rechip so if you were to use one of these, you'd have to hope it would satisfy the ignition and fuel maps for your engine.
__________________

mrmad 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
FOR SALE Modify NGK V-power spark plugs holypaulie For Sale 1 10-25-2007 08:55 PM
Warning to my NJ buddies... unstable bob General Discussion (Off-Topic) 9 09-21-2007 07:46 AM
US Forest chief: Use trees to make ethanol repete86 Automotive News, Articles and Products 3 09-13-2007 06:36 PM
Drove first hybrid-real eye opener tulsa_97sr5 General Fuel Topics 8 07-09-2007 12:51 PM
Google Earth Help GasSavers_DaX General Discussion (Off-Topic) 5 06-21-2006 12:44 PM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 06:42 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.