High load/boost hesitation and wet plugs....?

[RixR32]

Hey fellas,

I've recently developed the dreaded high boost/high load hesitation.
First off it's erratic, sometimes (but rarely)not doing it at all.
Only happens above about .7 bar (running 1 bar without resitrictor. NO boost controller)
Boost gauge fluctuates while doing it (Nismo gauge)

The other funny thing I noticed is that my car has been sitting for 8 days in my garage. I went out today to change out the plugs and all 6 plugs were wet. Bottom of the threaded area and the tips...

Should they be wet after sitting over a week??

Wonder if it's related cause it does run rich, but no worse then any others I've seen, and it starts and gramma-drives just fine. Idles at a rock-solid 950 rpm. Throttle response off-idle is great also with no stumbles.

I've replaced the following:

Plugs NGK's at 0.8
new coilpacks
new coilpack harness
new CAS and set timing to 20 BTDC @ 950 rpm @ operating temp
New Tomei fuel pump
Checked endlessly for boost leaks (found and fixed a couple small ones but no change)
New Maf's and connectors
New TPS and set to .48v at idle, is 5v at WOT
Checked the rubber piping after Mafs, no leaks but pipes are pretty "squishy?"

I have 2 new O2 sensors I haven't installed yet, not sure if they'll help.

Only thing I can think is injectors. No external leaks I can find though..

Any ideas??


Rick

[Skym]

Bigger lph fuelpump should raise fuel pressure slightly and engine runs richer at mid to high rpm (into 10's) where injectors are open more (gets worse on knock fuel map, might be into 9's). The fix is to retune ECU to close injectors, fix knock problem (sounds like it's switching to knock fuel map, etc which runs it richer at high rpm). A way to stop spark plugs fouling is to run a hotter heatrange spark plug (factory plug).

[RixR32]

Wow, thanks Skym.
You're like a mind reader. I put new heat range 6 plugs back in her yesterday, and no more hesitation.
It does bang, pop, and fart on deceleration a LOT more than it used to now, like continually until I'm back on the throttle.
No black smoke or anything to indicate it's TOO rich, but I feel it should have more power for what it's got...
Guess it's time for a tune, and a good wideband.

550 cc injectors good to get me to a safe, solid 425 WHP? Already got steel wheeled rebuilt stockers and supporting mods.

Rick

[RixR32]

Just an update, new 02 sensors helped as well, popping and backfiring is mostly gone.
Injectors and dyno tune can wait until winter now so I can at least drive this damn thing!!


Sent from my SGH-T769 using Tapatalk 4 Beta

[Skym]

You're welcome. It's common knowledge (spark plug manufacturer recommends it) to change spark plug heat range when running engine richer or leaner. Also not the first time I have seen this problem on a RB engine and changing sparkplug heat range (to stock which was used when engine was running richer, into 10's at factory) helped to solve problem.

When engine is running rich it fouls the o2 sensors and they become lazy, hence o2 sensors make ECU make engine stay rich longer which adds to the problem and get popping from exhaust (flames from exhaust if have no cat). Unplugging old o2 sensors would have stopped it. I would have waited until fixed tune problem, as new o2 sensors are just going to foul again. I ran my cars engine without o2 sensor, but have to check A/F ratio on dyno or via wideband afterwards to make sure engine is not running too lean and o2 sensors + ECU are adjusting to it.

With injectors, use this calculator -

http://www.deatschwerks.com/resources/fuel-calculators/fuel-injector-calculator

You'll find that you'll run out of fuel with 550cc injectors when want to crank the boost up. What you want is under 80% duty with injectors for 100% reliability (supposedly to prevent injectors overheating, failing on racetrack). They say 90% in link.