Differences between CRX HF with/without FFS

[Scott Williams]

I posted on ecomodder with this, and no one responded, so I'm trying here. I was looking on fueleconomy.gov at the 1987 Honda HF and noticed there are two versions. One being FFS and one without that designation. I read that FFS is like a feedback system on the carb that meters the fuel like later fuel injection. But what I wonder is why there were two versions in most every year of the CRX? Do they follow a California/49state difference like my Honda VX? And finally, how do you recognize the difference if you are shopping for a CRX? On the fueleconomy.gov, I see the FFS is much higher in MPG.

Thanks

[GasSavers_Erik]

Both models on fuel economy.gov are FFS (fuel feedback system)- it is likely just an omission. To my knowledge, all 1.5 liter carbed honda civics and crx's (84-87) use a controlled intake manifold vacuum bleed to lean out the mix when the oxygen sensor is showing a rich condition.

The 87 civic with 1.3 liter had no oxygen sensor and thus no FFS.

There was a california version and a 49 state version of the 87 CRX HF. Both versions had a slightly different emission control system and I know that the 49 state version has a shift indicator light. Similar to the 92-95 Civic VX, the non- cal HF's got better mpg than the california HF's. In addition to the non- cal and cal models, there also is a high altitude model. My CRX HF happens to be a high altitude model (which has a slightly lower geared trans and a different carb). I drove it home when I bought it but it needs a rebuild so I have no mpg data.

If you read the emissions sticker under the hood carefully, you can tell what model the car is (49 state, high altitude or California). Mine states that it is a high altitude model.

If you are thinking about getting one- be aware of the hard to find 5 wire oxygen sensor in the 87 CRX HF and that there are literally 50+ vacuum hoses, any of which might be cracked, thus throwing off the idle or affecting drivability.

HF features that improve mpg- To reduce friction, the carbed HF's have only one compression ring and are bad about getting the oil control rings caked with soot and stuck and burning lots of oil under load as they get older. They also have a slightly higher compression ratio than the non-HF engines and only 1 full sized intake valve instead of two. Besides having rocker arms with rollers that contacted the camshaft another fuel saving feature of the 87 HF was the alternator cutout control module which turned the alternator field on and off as needed just enough to maintain battery voltage.

Of course, all of the 84-87 civics and crx's had the CVCC cylinder heads/carbs which featured a tiny intake valve that fed a small amount of rich mixture to a small precumbustion chamber surrounding the spark plug and then a different set of intake runners supplied a lean mixture to the main area of the cylinder. You can see pics of an 8 valve 1.3 liter CVCC head if you view my 87 civic.

As you can probably tell, I am quite a fan of these cars... nuf said...

[GasSavers_BEEF]

I don't think I can add much to this conversation.

I did find several places that show FFS as "feedback fuel system" it also talks of fuel injection which I think is not the case here.

just a guess but did it maybe have some sort of primative feedback that would adjust the carb? maybe some sort of mechanical equivalent to the o2 feedback?

I've never heard of this. there are several honda guys around here and maybe one of them would chime in.

***edit***

yea, what he said above

[Scott Williams]

Thanks for the great info Erik.

[spotaneagle]

If you are thinking about getting one- be aware of the hard to find 5 wire oxygen sensor in the 87 CRX HF and that there are literally 50+ vacuum hoses, any of which might be cracked, thus throwing off the idle or affecting drivability.

omg too many!