Did the flex sensor on the feed line fix the dropping ethanol content?

 

Absolutely solved it. Run up to redline and it didn't blink. Solid 79% ethanol across the board. I missed it the first time around last year, but it definitely should be on the high side as you all recommended

 

Huh, interesting.

 

I suspected it would. My theory is it doesn't read as well when pressure drops and car isn't bypassing most of the fuel

 

Canceled the dyno time slot. Asking instead to just perform leakdown and the rest of the previously requested services

What causes a misfire at only WOT from low rpm? Half throttle is fine.hakf throttle rolling into WOT is fine. It's not always consistent; it was perfect one hot Saturday without a misfire in sight. But that was also the scenario when the ethanol % was dropping changing all the tables as rpm climbed.

Assuming things look OK from leakdown, I'm not quite sure what else to check. I've already tried swapping coil harnesses, mending any dodgy butt connectors, changing plugs, gapping down plugs, cleaning grounds. Short of replacing my entire wiring harness or asking Brain to check the ms3x on his stim for something that only manifests under one specific condition, kinda at a loss.



​​​
​​

 

In my opinion, liquid, pressure, resistance, temperature, and turbulence all factor in to a misfire at that level.
All that liquid fuel quenches the ignition. Too much pressure, increases the resistance across the plug. Too much resistance and the plug won't fire without more voltage. I also am convinced that cold air makes a huge difference in all this. So much going on in that tiny space that turbulence is trying to blow out the flame. Not sure what the answer is. I am gapped at .010" currently.

 

The thing is, he's been over 300kpa for a while now, and we have many logs of this car without misfires on current (my) tune.

Payam,
I'm starting to wonder if we're overwhelming the pump and your fuel pressure nosedives at sudden boost onset? What pump are we working with again?
We've been troubleshooting the ignition system this whole time, but maybe we're just looking in the wrong place. I'll lower boost on next map and let's test this theory

 

I have logs of my car over 30psi too. My misfire is difficult to reproduce off the track. It also doesn't show up at warmer temperatures but then appears when it cools down.

 

And goes away with lower boost? interdassssting


payam, do you have fuel press gauge?

 

I think he has a dw300, just like me.

 

Yep

 

I do have a fuel pressure gauge but it's a bit jumpy mounted right before the fuel rail. It's not wired into the MS as it's part of my innovate gauge and would be an analog out.

I'll be dropping the car off this evening for other service.

And it's been wet all week so no new logs.

I'm using a dw300, - 6AN lines from pump hanger to rail and back, ID1300 and a fuel lab filter

I'll try to look at past fail logs to see where it's commonly dropping out. I think it's around 5200ish

 

Example of the more violent misfire. What causes boost to drop a bit, before the RPM takes a hit? I'm still at 99% throttle at this point






Another example, RPM and MAP drop instantaneously, I react about 1/4 second later and TPS drops

Here is the most recent log. I swapped the ethanol sensor and it's not as bad as it was before, but does present itself around 4500 rpm. Just some see-saw RPM action

 

Each time anything eventful happens it's immediately after hitting peak boost: 31.7 psi, 32.1 psi, 31.6 psi, respectively.

 

can you disabled boost cut and try it? I wonder if the ramp up is so fast that it predicts overboost and cuts before even hitting it.

if this is the problem I'm gonna laugh so hard

 

I will be laughing my *** off, I actually had a similar thought at one point. Looks exactly like boost limit, but mine is set to 330kpa.

 

Boost cut is set to 325kPa, and at least in the scary cut, it hits 318.9kPa max. Is it just too close to it's threshold for it's prediction?


I mean, at this point it's either turn it up or off and #sendit when it's on the dyno and hope it doesn't misfire.

Vlad, does afr looks OK to hope and pray it holds together? I think you mentioned it deviating from target a bit. This still doesn't explain the occasional RPM saw toothing though.


It's thundering, so there won't be any logs before it's in the shops hands. Reschedule dyno will take a couple weeks if they already gave my spot up.

 

I believe I understand that boost cut is predictive and will cut fuel if it looks like you are going to hit the limit even if you don't hit the limit.

 

So the last log taken, WOT3rd_misfire, shows minor bumpy misfire. Not as bad as the violent ones.

I'll get the car back and try again with higher overboost setting or whatever Vlad swings my way. Then rebook when it's all behaving properly.

They are doing a leak down as we speak then some minor welding stuff. Will update as soon as I have leakdown numbers.

 

I looked over his last couple logs, it definitely wasn't cutting due to boost cut, but agreed its really close and if anything might be contributing to issue

*edit:
Use the +2 map and just raise boost cut to like 340-350. Your fuel and timing should not be an issue nor should boost.