I'm sure a few of you know of the scoop. I've posted about it a few times. My car has a stock bottom end with Skunk II stage one cams. When they were first installed the car ran fine, not the best AF possible, but I had it plenty safe for an all motor honda. Timing belt slipped a while back, had the head revalved and resurfaced, and added Portflow inners. Ever since then the car hasn't been right. Makes good compression numbers (230 on all four cylinders), but it has a massive lean spike when the VTEC timing maps engage and was in general leaner across the board except toward redline. I dialed in as much fuel as my FPR and VAFC could muster without taxing the fuel system too hard and the spike was still very much on the lean side.

My next step was to install bigger injectors, but I would like to find out what the problem actually is, not just bandaid it. Could the machine shop have shaved too much material when the cleaned up my head? Do the symptoms I describe go along with higher compression?

Car throws no codes (except for me not having a cat), so apparently all sensors are functioning.

 

what injectors are you running?

 

Stock 240's. Thinking of getting Prelude 290's.

It's just odd. You can tell the car is flipping out about something at 5,700rpm and the ECU takes to about 7,000rpms before things start getting back under control.

Oh and when I mean a spike I mean a SPIKE. As in off the chart past 18:1 AF before I started adding fuel.

 

To me, that sounds more like an electrical problem than an airflow problem. I can't imagine higher-compression or increased airflow producing a pronounced "spike" such as the one you're describing. Just out of curiosity, have you tried dynoing it without the V-AFC attached, using only the FPR to add fuel?

 

wow. 18 is pretty up there. are you sure the O2 sensore is functioning ok on the dyno? have you brought the car to different dynos to test?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">To me, that sounds more like an electrical problem than an airflow problem. I can't imagine higher-compression or increased airflow producing a pronounced "spike" such as the one you're describing. Just out of curiosity, have you tried dynoing it without the V-AFC attached, using only the FPR to add fuel?</TD></TR></TABLE>

That is something I might try. Although my VAFC connections are soldered and the car was doing fine before, who knows. I wonder if I can just unhook the connector to the VAFC or will I need a new wiring harness now?

Edit: I'm stupid. I'll need a new wiring harness because with the connector unhooked my ECU won't be picking up anything...I think.

 

Installed the new distributor coil today, but I'm scared to take it up to high rpm in fear of it not being the fix and my plugs getting beat up again.

 

ActiveAero,
About 6 months ago I got my head revalved and they took 20 Thou off the head... My car hasnt been the same since either. Something is definately not right with mine. I know this doesnt help, but just wanting to let you know I'm in the same boat.

Ryan

 

.....sounds like you need bigger injectors.

310's should work good for you, I'd think. You can tune with the vafc that way.

Also, it's real easy to tell if the crossover on the vafc is the culprit. Lower or raise it by ~500 rpms and you'll see what the lean spike follows.

Also, the vtec unmt function could help you. Try +20 from lo to hi.

Brock, you know where to find me if you need anything else.

-hth