delkat

iTrader: (2)

I'm running E85 on DW1300s, BBX, Kelford Bs, built shortblock and all boltons. When cruising in any gear under light or no load I can feel the car surging like someone's pulling lightly on the e-brake. When I feel the surge and look at the AFRs they are going very lean (19-21) for a second or two and then rich (11-12) for a second and then back to stoic. This pattern sporadically repeats every 5-7 seconds. Under full throttle the AFR's are stable but the car seems inconsistent in how it pulls.

In my attempts to understand how to adjust the LTFT Idle and Cruise I've come up with the following:

Latency describes the time it takes for an injector to turn completely on at different voltage levels. As you increase latency you increase IPW since the ECU will compensate for a longer delay to get the injector turned on. Changes in latency change all the IPW by fixed amounts (in milliseconds) regardless of RPM, therefore the affect IPW at idle approximately twice that at cruise. So if you increase latency you will increase the idle fuel trim twice as much as you will increase the cruise fuel trim. Scaling can be used to change the global fueling and affects IPW by percentage so the idle and cruise fuel trims should be about the same change by percentage. If you increase scaling the ECU thinks you are using bigger injectors and therefore decreases IPW’s to compensate and vice versa. If your Fuel Trims are positive the ECU sees that over the long term (LTFTs are adjusted every 4 minutes) the ECU is having to add more fuel to keep things at Stoic and vice versa.

Example: LTFT Idle = -4.01, LTFT Cruise = +11.34. The ECU is compensating to reduce the idle fueling and increase cruise fueling. If we decrease latencies we will decrease the idle trim more than the cruise. Say we make a change and we get Idle = +5 and Cruise +15 then we decrease scaling (adding to IPW) to increase global fueling. Then it drops trims to Idle = -3 and Cruise = +7. Then we reduce latency more and get +3 and +10, then repeat scaling and get -1 and +6. Repeat process again.

In my unsuccessful attempts at finding the correct numbers, this is what I've seen:

Baseline - 4.008,3.192,2.592,2.112,1.800,1.656,1.392 – Scaling 713 LTFT Idle -4, Cruise +11.5
Tune 1 – 3.696,2.904,2.208,1.896,1.656,1.392,1.104 – Scaling 680 LTFT Idle +2.14, Cruise +12.5
Tune 2 – 3.696,2.904,2.208,1.896,1.656,1.392,1.104 – Scaling 592 LTFT Idle -9.3, Cruise +10.3
Baseline - LTFT Idle -9.7, Cruise +10.4


I first lowered the latencys with Tune 1 and got the results I expected; both trims went positive with idle increasing more than cruise (assumption since cruse maxes out at +12.5).

For Tune 2 I kept everything the same except I lowered scaling to increase global fueling. The results were not what I was expecting and the car ran very rough. Attached is a log where I watched the Idle trim change from +0.5 to -4.5 in a few seconds while the car was idling. After a couple more hours the trims ended up at -9.7, +10.4.

I then loaded the original baseline map back in and now the car is still surging (AFR's oscillating as described above), pulling inconsistently and the trims are even whackier. It looks like I'm way too low on the scaling compared to some of the other setups I've seen posted. I'll try some of these setups soon.

Has anyone else experienced this lean surging/oscillation during closed loop cruise? This issue was evident in all 3 of the tunes I tried. I also have a huge hesitation (power drop out) for a split second as the car transitions from vacuum to boost. It feels like a broken accelerator pump on a 4 barrel Holley.

criptballer

iTrader: (3)

wow, 2 days ago no topics on dw1300s. Now, a few. interesting.

is your maf tuned?

GL man, seriously.