Powerband flat spot - IPW oddity

[Barnes]

So I finally got off my fat ass and installed Hertz's Bucket Spec Evo3-16g. All that is gravy, no leaks blah blah blah. Just creeps a little in the higher gears which is to be expected. So I get things tidied up and have taken it out for a few spins around the back roads while data logging. I find some strange sh*t is happening.

Most of the time when I mash the gas, the car boosts up to 8psi and doesn't seem to be going that fast. Then all-of-a-sudden it'll take off like a bat outta hell as the RPMs get up there. Looking at the data logs I find a strange phenomenon. I smash the gas (100%), air flow increases, but the injector pulse width stays flat. Like.. dead flat, at 12.5ms or something. This it will all-of-a-sudden jump sharply, then continue up at a smooth pace like it should. So I can see that the dead spot I feel while driving is the injectors not opening up. Any ideas what could be causing this?? Although I'm tempted to not even figure it out as a have a round of mods that might make this go away. /ubbthreads/images/graemlins/dunno.gif

Only other thing worth noting is that there is a CEL 44 code, ignition coil. Not sure if there is something wrong, or if it has to do with the COP setup. I haven't searched yet, I will after I post this. Yes, I know, I'm doing this out of order. /ubbthreads/images/graemlins/grin.gif

Car drives relatively normal otherwise, save for some crappy idle. Haven't started trouble shooting this yet, but I'll wait till I recirc my BOV. That is probably causing a bit of it.

Current Mods:
Stock ECU (Caps changed by me already)
Stock Maf (On 3" intake)
190 lph fuel pump
AFPR set at 35psi ( I think)
Coil-On-Plug w/NGK BPR6ES (6 or 7? Whatever the stock temp is, can never keep the numbers straight)
Stock intercooler and piping
Stock BOV (uncrushed) vented to atmosphere ( I know, I'm too lazy to pipe it up until I get the new MAF on /ubbthreads/images/graemlins/tongue.gif)
2.5" Downpipe
3" turbo back
Evo3-16g, ported, Bucket Spec
2g quasi-ported manifold
2g O2 housing, ported

Mods to be installed:
Keydiver ECU
#482 MAF (If I can find the f-ing cable!! /ubbthreads/images/graemlins/mad.gif)
Denso 660's
JonVR4 IC pipes with Evo8/9 intercooler
Dejon style modded BOV (to be purchased)

 

Is the airflow Hz also flatlining at the same place in the logs?

 

[Barnes]

It is increasing, although not rapidly. But right after the injector pulse width jumps up, the airflow increases quickly right after.

 

[Rausch]

I wonder if you're getting a clean, even signal from the CAS...

 

[toybreaker]

Have you logged the tps signal?

 

[Barnes]

Well, the black car is pretty much in storage mod until I fix the rear wheel bearing. It runs well, so I could always borrow parts of it. /ubbthreads/images/graemlins/crazy.gif

 

[Barnes]

Quoting toybreaker:
Have you logged the tps signal?



I wasn't hitting 100% throttle so I adjusted the TPS with the logger in the engine compartment. I moved it through the entire range and it was nice and smooth on the graph. I haven't logged just the TPS signal though. I should try that. Could still be goofing up when it gets to temp.

 

[prove_it]

Does anything else flatline? What do the RPM's on your logger do at that time? What about fuel ratio?

 

[Barnes]

No other flat spots. Just slowish RPM and airflow climb. No idea on AFR. I don't have a wideband. However from my crusty memory I always remembered the o2 voltage going right to the top of the chart. I did notice on the logs that I'll hit the gas, and the o2 will will decline from 1v to something like .7v, then when the car gets past the flat spot it will go right back to the top (~1v a little less of course).

I would have guessed it would jump straight to the top once I mash the gas. I need to get a freakin USB - serial adapter so I can log with my GFs laptop. I have no way of getting files off my circa 1995 laptop logger. /ubbthreads/images/graemlins/uhh.gif

 

[prove_it]

You could have a bad MAF that doesn't read that certain airflow then picks back up. Like you said you got a new one so you can always try switching it and if it goes away great, if not switch it back and try something else. I always recommend switching back if it doesn't work so you don't end up stacking problems on problems and getting buried.

 

[Barnes]

I guess I'm debating between tracking the problem down now, or putting on parts and hoping the problem goes away. /ubbthreads/images/graemlins/confused.gif

 

[prove_it]

Right I feel the same way. I would try swapping the MAF. To me it really sounds like the MAF is not reading correctly. Sometimes to fix a problem it helps to swap known good parts on and see if there is a change. Either way you'll be one step closer to knowing what's wrong. If it doesn't fix it though, swap it back. That's real important.