2010 Camaro SS - Whipple 2bar kit - Warm Startup RPM Swing

[10_SS]

So I have the Whipple SC, LS3 all stock except what comes with the whipple kit (injectors, boost a pump, etc). I also have the 2bar OS with ZR1 map sensor..

Everything's great (other than the weak fuel pump that drops pressure during WOT even with the BAP)...

Now I'm just trying to fine tune some things... Noticed my startup while warm is the only thing that needs help.. when cold (coolant temps below say 80F), it startups up great... RPM comes up to around 1900 then falls to around 1100 and is steady and sounds great.

When warm... (like when shutting off to get gas, or even after about 4hrs off on a warmish day...), when I start it, RPMs come up like normal (~1900rpm), but then it sounds like it's lean, and rpm comes down to around 400-500, then back up to ~1100rpm and things are normal.

To me it sounds lean, sometimes when getting gas when I restart after ~5mins... it will pop (sounds like a lean pop after the rpm dip... right when it re-lights and comes back to ~1000rpm).

I've played around with the "Cranking FA Mult Stage 1 vs. Cranking Time" but never seemed to improve... it only got worse so now that table is stock. I've also switched to MAF/MAP mode and no difference compared to running only MAF during startup. I then added ~15% to the VE table in that area but there was no change (so ignore the choppiness in the VE table).

To me, it looks like the Injector pulse width is very low 1 second after warm start and it's causing the problem, since RPM comes back up after the INjector pulse comes back up... any idea how to fix this?

Cold Start (Good): Frame 90, no RPM fluctuation
Warm Start (RPM unstable): From 37633

2B091 Cold Start Smooth.PNG
2B091 Warm Start Dip.PNG

2B091b WHIPPLE_Dynamic Airflow enabled PE Enrich 1500-2000rpm.hpt
2B091 Cold and warm start.hpl

[BMWMD82]

I had a similar issue after my Magnuson Heartbeat TVS2300 install. Mine was more an issue after the car sat, usually with a cold engine -- but it would crank and fire up normally, then bog down below regular idle speed and run rough for a few seconds before returning to normal.

This happened when I was running their supplied tune file. My first thought (like you) was that it was running lean when this happened. After doing a little logging, I found my fuel trims were quite a bit negative at idle. After I got the MAF curve dialed in (fuel trims close to "0"), the problem went away. Seems that it was running rich in open-loop, and that was the cause of my problem. Hopefully yours is something similar.

[10_SS]

When cold mine might be a little rich for a second or two since it sometimes is just a bit choppy like a cam is installed but RPM's are stable, but when warm sounds lean since I get a little pop sometimes (I have straight through JBA catback). Either way thanks for giving me something to look into, never thought of that.

[Kyne]

I've had a similar issue where it would immediately kick into closed loop while it was still in enrichment and lean it out to stoich. Had to delay closed loop to cure that.

[10_SS]

But also seems like whatever the problem is, it's done by 2 seconds.. It's the under 2 second mark.. either way maybe I'll play with the MAF sensor in the startup/idle area's.

[Iam Broke]

Try massaging your Idle startup airflow vs. ERT and ECT table Under the Idle Airflow tab. I cut mine back to reduce the flare up upon start but you can extend it into the runtime longer if you want. If the decay is too fast it may stumble and try to die.

[C5 2000]

Compare your file with stock file and retune. Set desired Throttle Area and Throttle Area Increase Rate back to stock. Also look at the Fuel System ( Fuel Pressure ) in the stock tune and compare.

[10_SS]

Try massaging your Idle startup airflow vs. ERT and ECT table Under the Idle Airflow tab. I cut mine back to reduce the flare up upon start but you can extend it into the runtime longer if you want. If the decay is too fast it may stumble and try to die.

I have modified the "Idle Startup Airflow vs. ERT vs. ECT" quite a bit and went back to stock... it's a bit better when stock... almost like the problem was still there with less flare, but since rpm's were lower, the dip was lower so it was more noticeable. Now noticed the time periods in the other settings settings seem to match the time I notice the dip in rpm 1-2 seconds in... so I would think even if my fueling is off just a bit somewhere, increasing the time should help it start smoother... I never touched those. Thanks Broke! I'll give it a whirl.

[10_SS]

Well I decided my MAF and VE were good, so I found a ZL1 file, coped all of the Startup Airflow settings along with the Timing "Flare Control" settings... and it's very good now.. cold start sounds perfect with a smooth ramp up and back down to a high idle (as expected when cold), and warm is also good, just doesn't ramp back down to idle.. it sorta falls from 1600rpm to 700rpm.. but that's fine since there's no surge/swing... and no pop either.

The ZL1 settings also fix the original high startup flare annoyance that I was trying to reduce and somehow made worse.


WarmStart_ZL1Settings.PNG

[10_SS]

So the fluctuation is 100% gone, however I still hear what sounds like fuel being shut off right after the startup flare (Only when warm)... with a hint of a pop when fuel is turned back on. Look at the graph of the injectors right at the peak of the rpm swing... injectors drop to bare minimum while rpm, airflow, map, throttle etc are increasing, or holding level... so that's what I can hear, is basically fuel cut. So when the injector PW comes back up, from lean, the re-light causing the random backfire. I think after this re-light it may be just a tad rich until closed loop takes over (3-4 seconds), but that's a separate issue.

So after all it is leaning out right after RPM's peak... but it appears to be on purpose... but it's not because of the VE or MAF... there's something else doing it.

Or - could the minimum PW be set too high due to the larger injectors, and it's actually requiring less than 0.8msec during that period.. and because of that it's getting too much fuel... because the PW is sitting no the bottom there...?

Warm_Start_ZL1_INjectors at Minimum.PNG