Lean start, procharged WK2 SRT8 grand cherokee

[spitune]

Currently on the dyno with this one and this is the second time I have run into this with the exact same setup. On initial start the truck will idle rough and is very lean, about 12-14 secs after the fuel trims start ramping in and go to there max. At that point the idle stabilizes and about another 10-12 secs after that the fuel trims go back to normal and the truck runs great. I'm not having any other issues with either truck at all, both run and drive very well and make good power with the D-1. 540rwhp. I have attached a log of the start and one of tunes I am working on. Stock SRT8 Grand Cherokee with D1 Procharger and FIC 775cc injectors.

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catalyst preheating?

[Jay@HAP]

The interesting thing is that before it hits CL it shows the LTFT are -30. Then the STFT start adding what the LTFT was taking out, eventually they both level out and it starts adding a little on the short terms.

The timing also goes negative when the short terms start to go high.

What does it do if you reset the adaptives before you start it?

[Hemituna]

Raise the CL enable temp to 70 deg so you can get the cold start fuel sorted out.
You can lower it again later, thought I often leave CL up near 50 or so to keep it a lil richer till it warms up.

[spitune]

Thanks for the replies. Jay I did try reseting the adaptives before I start with no luck. Hemituna I'll try that, I think I already tried something close to that but I'll give it a shot again.

[spitune]

It's been hard to get this Jeep back as it's my client's daily. I was able to try a few different tunes a couple days ago but I'm still having the same issues. Since this Jeep, I have now done another. Exact same mods, longtubes, injectors, and procharger. No issues at all with latest one. When I compare the tunes they are virtually identical, save for a slight variance on the VE tables. Does anybody have any other thoughts on this one? I have tried the suggestions above with no luck.

[JnJSpdShop]

Dodge Injectors.png

I am working on a 2014 SRT8 with a Procharger D1SC & long tubes but the customer purchased injectors from FID and had some questions about injector scaling that I am trying to wrap my head around. Why does the stock calibration characterize stock injectors all the way down to around a tenth of a millisecond? I would imagine with stock injectors warm closed loop idle is probably around 2 ms. I know with the 630cc/min @ 43.5psi injectors I have it is around 1.3-1.4 ms. Seems like lots of wasted resolution for an area the injector will never see or function at. Would it make more sense to start the table around 0.5ms and have more breakpoints in the 8-12 ms range or doesn't it matter. I know the control will interpolate between values but it my method of thinking make sense or have any benefit?

[akiese]

I'd imagine it's because at low and very low pulsewidths the flow of the injectors are very non linear, above a certain pulsewidth they flow pretty much in a linear shape.

[06300CSRT8]

A lot of people forget to realize that an injector starts to inject fuel at 0.000001 ms. From the moment it is energized until it reaches the commanded pulsewidth it is pissing out fuel. we don't have access to the injector latency, so I cannot say for sure DCX didn't build it into the tune, but the PCM knowing the path from 0.00 to desired pulsewidth will certainly allow for better fuel delivery. I would assume there is a concept of total fuel delivered (which is in the VCM scanner) which would be a calculation using the full pulsewidth path from 0.000 to final desired in an engine crank cycle.

[ElecTech]

. we don't have access to the injector latency,

"Injector latency" would be the "Inj PW Offset" table, in this case. It should be available for all of the Dodge applications. If you are speaking about a short pulse adder, like the GMs have, it's not needed because Dodge uses actual fuel mass values over the full range and not linear approximations.

[06300CSRT8]

No, not what I mean. Offset tables tell you how long the injector needs to fully open by voltage, does not have anything to do with the fuel mass delivered during that delay period. And for sure we only give the ECU 10-15 fuel mass data points, it is still using linear approx. in between those points. The less you give in the lower PW section the more approx. linear calcs it is going to use and the crappier your idle and startups will be.