so I'm tuning an f20b in a 4g prelude and all is going great, until I enable vtec and start tuning the high cam tables. after 5500 it starts leaning out more and more as rpms climb. I never let it get past 14.0 at first. started adding fuel to the high cam tables, but it makes zero effect. dumped a mass amount of fuel into the high cam tables, and revved it out, it reached 15's and was still climbing but I let off. went through everything in the car to try and figure out what's going on. fuel pressure good, injectors nowhere near maxed out and all spec out perfectly, all grounds are good, everything vtec related is operating correctly including the h22 vtec valve body with pressure switch showing pressure in vtec.

out of curiosity I decided to dump fuel into the low cam map. BINGO! vtec richens up. no clue why, but when in vtec the ecu is still reading the low cam maps and totally ignoring the high cam maps. datalog shows it's switching to high cam just fine though, and vtec is obviously working.

went through the entire car all over again and verified there are no wiring errors or any mechanical issues anywhere whatsoever. originally had 340cc prelude injectors, also tried dsm bluetops. also tried 2 different known good ecu's, a p06 and a pr4 both of which are converted properly to vtec, both of which have operated perfectly on other vtec motors. started with the ostrich all along, also tried 3 different chips, 2 different laptops with 2 different versions of crome pro both of which are known to work perfectly fine, 2 different resistor boxes, and at least 5 different maps using custom scalars and original p30 scalars. also tried disabling multiple vtec options, still no change. nothing I tried would allow it to actually read the high cam tables while in vtec.

I'm totally stumped. I remember back in the day seeing other people have this issue, but cant seem to find anything at all about it now.

any ideas? (and dont say "go neptune or hondata". I know that might solve it, but I want to figure this issue out for future reference)

 

What does the ECT sensor log do when VTEC crossover hits?

 

stays steady at 175-177 from what I recall by memory. are you thinking something might be happening with ect dropping to below the vtec threshold for temp?

 

I doubt Vtec is actually mechanically engaging, which is the only time I've come across this. Other than using QD2 with the P72 base, but we did move to the gold rom for a reason.
If you can confirm that Vtec is actually engaging with proper oil pressure and live tracing doesn't switch to the high cam, it's most likely your datalog protocol. Search the opensource files for the other version of QD2.
If that doesn't work, uninstall Crome and reinstall. Make sure to backup your license.
If that doesn't work, disable the Vtec VSS/VTP/ECT check, and make sure your high/low load engagement value is the same.
If you bridged the VTP to VTS or grounded the VTP, make sure you did it correctly or the ECU will think the circuit is off.

 

vtec is definitely engaging mechanically, and staying engaged. it has a cai, and is very audible when engaged vs disengaged, as well as the power difference easily felt. I also disconnected the vtp and grounded it and disabled the pressure check and speed check and revved it in neutral while ohm'ing the pressure switch, and it has continuity from idle up to vtec engagement setting then becomes open at any rpm above vtec engagement set point. so its definitely functioning mechanically and holding pressure just fine.
the datalog was switching as normal between low cam and high cam, as well as recording afr into their expected cells of low and high cam. its just refusing to actually read the high cam tables for some reason: still using low cam fuel table values, even though datalog is switching to high cam just fine and vtec is functioning properly physically.
the high and low engagement settings are the same. and the load thresholds are untouched; still original p30 settings.

 

this is why I;m stumped. everything about the car itsself checks out perfect. and I tried multiple: resistor boxes, injectors, laptops, chips, ostrich, maps, and settings. zero change, still reads low cam values while in high cam physically, even though datalog trace is switching to high cam.

 

Yes - but basing my guess out of trusting your previous diagnosing.

But in my experience, while not as extensive as VegasInvasion's, the only time I have had this happen was when VTEC wasn't mechanically activating. You would be surprised how intake pitches change even without VTEC engagement.

 

no i know. i did tune the low cam all the way to redline though before enabling vtec to tune high cam, and there was a significant sound difference between the two
and just to make absolutely sure, I did go through the actual process of testing to make sure it really was physically engaging vtec, and holding it.

I'll double check ect's to make sure that isnt it though, that actually didnt even cross my mind, so thank you. by any chance, do you know what the oem ect is for vtec operation in a p30 code base?

 

If memory serves me correctly it is 149* F for VTEC operation on a stock ROM. I could be wrong though... so take it for what it's worth.

 

ok thank you. I'll probably be back with the car this coming weekend so I'll definitely keep an eye out for ect upon switchover

 

Don't ground the VTP. Really not sure why people do that.
Splice the D6 VTP wire with the A4 VTS wire. Create a new rom, DON'T disable VTP.
If it throws a VTP code, then disable it.

 

turns out it was crome. which I still can't explain considering I tried multiple different laptops. I ended up scanning the customer's chip from a previous h23v build that was known to work then, and used that as a base for this f20b and everything worked perfectly normal. *shrug*

 

lol doesn't surprise me at all.