What octane to use in '87 CRX HF?
 

On the drive bringing the CRX back, it had some drivability issues. Mainly the lack of power from the fact that the motor could not take any high load (IE, any heavy throttle or hills) with out taxing the motor. Any hard throttle caused it to miss fire, but putting around at low (and I mean low) throttle it was fine, and even revved ok.

This was before I knew it was an HF, and before I knew the HF was a 10:1 compression motor.. :o Now, typically 10:1 must be ran with premium, but surely there's a way for it to run on regular? And would this account for some of the issues above? I've been thinking 2ndary barrel of carb, but if it was running too low of an octane... may have been my issue.

Surely I could just back off timing and run regular?

Surely you could just fix whatever the issue is that's causing it to ping. Probably carbon buildup or something stupid.

The car was designed to run on 87. If it can't, there's something wrong. Your timing is probably somewhat out of spec, especially if the timing belt is worn. You can probably get away without changing the timing belt (I don't agree with change intervals), but the more it stretches, the further out your ignition timing will be (I can't remember which direction it alters the ignition timing, I think advanced.)

Timing belt is being changed this week, just bought it Saturday. Needs a lot of tune up work. Plugs, cap and rotor, timing belt, and a carb rebuild kit.

I wasn't sure if they were intended to run on premium or not, or if the archaic ECU (if any) detected such changes in octane. It's a combination of factors it seems contributing to the poor drivability, I just don't know if this is one of them.

Fuel for the confusion:
http://www.automobilemag.com/green/r...rid_sedan.html

Notes the HF uses premium. I do not have the car with me ATM to check the owner manual either.

Not sure if your gas has ethanol in it or not, but if it does it will do exactly what you are talking about, you can always try premium and see what kind of change it makes, it might cost you $.60 more to fill up but it seems like it might be worth a try.
You should also make sure that the warm air intake is fully intact and working for that will make it run poorly as well.

There's many factors contributing to it's poor performance. I can't find it and I don't have the car with me at the moment to check the owners manual, but does anyone know what octane Honda says to fill the HF with?

texanidiot25 -

I have a 1980's Car and Driver featuring the 1st Gen CRX, but not with me at the moment. I just looked here :

EPA MPG for 1985 Honda Civic Coupe HF

It says regular gasoline. That makes sense to me because I never remember the 91 Octane requirement for the 1st-gen CRX HF.

CarloSW2

texanidiot25 -

This doesn't answer your question, but I think you'll find it interesting :

http://ecomodder.com/forum/member-cf...crx-1stgen.jpg


CarloSW2

Thanks CFG. I knew about the other mechanical changes, but not the alternator switching! I'll have to rig a dummy light manually and see if that holds true.

When I get to the car, I'll toss in a bottle of octane booster for s-n-g's. Among other things, carb rebuild, timing belt, and ignition tune up parts are on the way. Glad I wasn't knocking the motor to hell with regular. It's interesting that Honda used high compression with regular gas. But I'm moving from the V8 world to this Honda, so maybe the smaller/weaker motors don't need high octane as much?

More info about the car: http://ecomodder.com/forum/showthrea...-hf-13053.html

It's a huge issue over whether high compression engines actually need higher octane fuel... if you were just a backyard engine builder, it'll be somewhat difficult for you (as many others - no offense intended) to understand that high initial (static) compression really doesn't mean too much when the engine is running - dynamic compression and mixture velocity/consistency is what's important.

If you're interested in such things, The Old One - Energy Dynamics has an interesting archive of articles and information from Larry Widmer, who's done alot of research and development on the subject. He runs (daily driver) a supercharged 12:1CR (may be slightly higher) B-series Civic on pump gas.

None taken, I love learning. I've always seen things from a performance view, which was when it came to high compression motors, run high octane and advance until it knocks, and go from there. (basically).

Thanks for the link, I'll check it out :thumbup: