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Still fighting bouncy WOT values (FINAL)

EfiniX

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Oct 18, 2012
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portland, or
I'm still seeing some bouncy values at WOT. I'm running SD, so I'm not sure what's causal and what's symptomatic. If I had to guess, the bouncing RPM value is causal. In the screenshot below, you can see that Airflow, Fuel Flow, and RPM all track the same bouncy behavior. The end result is bouncy fuel delivery which isn't the greatest thing in the world at WOT.



At the suggestion of someone over at the ECMLink forums (one of the link guys, if I'm not mistaken), I added in airflow smoothing.



Log File

Thoughts? After applying smoothing, things did get much better. The bouncy bits were far more bouncy before...



but my current condition still seems less than ideal.
 
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swe_gvr4_1991

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I bet that RPM bounce can be felt in the car.
What does the log look like if you free rev the car while stationary? Go slowly from low RPM to high RPM. In say 5 seconds time. That way we can see if there is some sort of CAS problem.
 

diambo4life

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Edmond, Oklahoma
Do you feel it? Mine is way jumpier...but it doesn't bother me. I can tell you at WOT it feels very smooth despite what my logs show. I was also under the impression airflow smoothing for SD was not recommended?
 

EfiniX

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portland, or
I could certainly feel it before the smoothing. That was recommended by Dave, one of the software guys at ECMLink. I thought it wasn't recommended either, but here we are.

If this is just the way of the world, I'm good with it. It's not falling on its face, and I'm still tuning out light-knock. Just wanted to see if anyone else had experienced something similar.
 

EfiniX

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Alright, I might be making some progress, assuming I'm looking in the right place. I pulled a log with 3 separate points of interest.

Log

First, WoT in 2nd gear. Felt breakup in the usual place. In the image below, the break-up is occurring pretty much where the bouncing starts on the FuelFlow graphing line to the right of the selection bar. This bounciness mirrors bounciness on the RPM and Airflow lines as well.



Something else worth noting is that my VE is way off. I'm pushing nearly 10.0:1 at WOT under boost, but my target is 11.0:1. In fact, that number hits 9.9:1 at one point on that graph (just after the moment pictured).

Next, I did two runs where I simply rev'ed up to where I see the bounciness normally.





No bouncy on the first high-RPM cruise, but noticeable on the second graph. The thing is I didn't feel any breaking-up on either of these high-RPM runs. Smooth feel and sound.

Am I not feeling the breakup under high-RPM cruise because it's just harder to feel those things when you aren't accelerating, or is this just anecdotal to my issue?

Could I be getting breakup due to a rich condition at WOT? 10.0:1 is certainly rich...

Something else? (CAS/fuel/etc...)

Thanks to all for the input so far.
 
Last edited:

swe_gvr4_1991

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I see two patterns here. One is that the RPM seems to bounce first.
The reason for this can't be many. Faulty CAS, or you're limiting power. In your case the limiting of power comes from the rich condition. When I started writing my SwD code I pushed the AFR as rich as it would go to see if the code was stable at full boost. I experienced what is called rich condition power limiting. This comes from the fact that the fuel is no longer being burnt and starts to acts as a cushion inside the cylinder. Remember fuel cannot burn without oxygen. There are MIT white papers on this strategy to govern power.
Try leaning out to 11.5 or even 12.0 and see if you get a cleaner pull. Remember to take it easy and if you hear knocking, back off the WOT right away.
This way you can get a good picture of what's going on at your 5000-6000+ range.

When you reach the sweet spot where you can go as rich as needed without getting any bounce, this is where your tune should be for your motor.
 
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EfiniX

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I'm on it. Thanks!
 

GSTwithPSI

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I think your real problem is 92 octane. I've found that super low timing values in the high rpm ranges sometimes cause sputtering, and conditions that feel like ignition breakup. You can try adding in some timing and do a pull just to see what happens, but you'll be limited by that piss water you're running. If you're really only seeing 8 degrees of advance at redline, I'd bet that's a large part of your issue.

Can you post up a full log?
 
Last edited:

EfiniX

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portland, or
Full log
Log

Sadly, here in Portland my options are pure gas (1 convenient station, but it's still 92oct), E15 (up to 92), and E85 at one inconvenient station.

Any suggestions on a meth kit?

/ubbthreads/images/graemlins/smile.gif
 

EfiniX

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Let's try this without the URL thingy...

click
 

OldHairyBastard

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To me it looks like either the CAS or you might not have enough fuel in the tank that causes a loss of fuel pressure. Check all your connections and maybe test and or replace your CAS with another unit for testing. Either won't take that long and will tell you right away if it was the CAS so you can continue on to other things.
 

EfiniX

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Thanks. I'm working out my rich WOT at the moment, and if that doesn't help, the CAS seems like a reasonable next step.
 

GSTwithPSI

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You need to make some adjustments to your VE table to get your true AFRs to start lining up with AFRatioEST. So long as those two values aren't tracking dead on, you're going to have an impossible time troubleshooting your rich WOT issue.

Also, what's you base fuel pressure set at? You're still running 950s, correct?

Do you have a recent 3rd gear pull from low RPM to redline I can look at?
 

EfiniX

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portland, or
My initial changes made a big difference. Yay for excel for making things go quicker. No opportunity for a true WoT pull, but I should get one done tomorrow.

37.5 base fuel pressure
FIC 950's
 

EfiniX

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portland, or
Well I finally got some WOT pulls in. Vastly improving results....

The first pull is in 3rd gear. I'm still running rich, but I'm out of the 9.x:1's.

click

The good news is that with the AFR leaned-out, I wasn't feeling the hesitation anymore. I made some VE adjustments and managed a 2nd gear pull (sometimes there's just not enough road). I got a touch of knock, so I backed off, but the AFR's looked even better.

click

At this point, I figure I'm just going to be doing pulls, tweaking VE cells, doing pulls, tweaking timing, doing pulls, etc.... I picked up a boost control solenoid that I hope to get installed and hooked into link. I'm hoping that being able to make more precise boost adjustments helps the process out. I'm sure it can't hurt.

Thanks, all. Looking good!
 
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GSTwithPSI

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Looks pretty good. WB and AFRs are lining up nicely for the most part.


Just looking at the 3rd gear pull:

I'd start pulling fuel from about 5k on. You're around 10.0:1 at redline, which is pretty rich.

Personally, I'd make a manual TPS adjustment. +4 @ 103% means you're off a bit.

Timing is super conservative, but I know you're limited by sh*t fuel. Is that as aggressive as you're able to get without knocking?
 

EfiniX

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portland, or
Yeah, I actually already adjusted the WOT VE cell on the 3rd gear pull to lean out a bit. My target AFR @ WOT is 11.0:1.

I'll check the TPS. Haven't even touched that setting in like a year.

And yeah, gas here is sh*t. I plan on getting the car running with little/no knock, then I'll starting bringing the timing up to where 92oct allows. Conservative timing until then. I'm actually noticing quite an improvement just getting the AFR's right.

I mean of course I am, right? /ubbthreads/images/graemlins/smile.gif

Oh, and follow-up question on AFR's: At what point would you think I should be targeting 11.0:1?

15psi?
17psi?
max (around 23psi at the moment)?

I'm noticing a touch of knock @ around 18.5psi targeting about 12.7:1. Seems a bit lean for that much pressure...
 
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GSTwithPSI

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Quoting EfiniX:
Oh, and follow-up question on AFR's: At what point would you think I should be targeting 11.0:1?

15psi?
17psi?
max (around 23psi at the moment)?



All of the above.
 

EfiniX

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Joined
Oct 18, 2012
Messages
647
Location
portland, or
TL;DR
bouncy RPM values caused primarily by running much too rich at WOT. Fixed with some airflow smoothing and through VE table adjustments.
underperformance fixed by richening spool-up

I figured that I would take a drastic step since much of my tuning was spanning weeks due to small tweaks. Finding a WOT workbook that would automatically adjust VE tables based on logs was helpful, but I was still not seeing what I wanted to see.

well, feeling what I wanted to feel, anyway.

So I took a chance and did something a bit weird. I loaded GSTwithPSI's OLMaxOct table and the last English Racing timing map.

OMG

I don't have any logs at the moment since I've not been doing much driving, but the difference is palpable. I've not been pushed into my seat by this car ever. I've never felt torque steer. And having owned an FD RX7 for a period of time, I do know what those things should feel like. My guess at this point: a combination of the following items...

1. Getting my VE table dialed so that the AFR values actually track correctly. This is probably going to be ongoing, but right now, I'm feeling pretty good about my results.
2. Getting the AFR's right! I was running too lean at moderate to high boost levels. Sure, I'd be at 11.0:1 @ WOT, but ramping up to WOT, I might see as little as 12.8:1 @ 18psi. GSTwithPSI's AFR values really richened things up during spool.

I'm sure there's going to be more tweaks, but my lesson today not to be afraid to make major changes just to see how the car responds. I do believe I would have gotten where I am now eventually, but with the small, incremental adjustments I was making, it could have taken all summer!

Thanks, all.
 
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