Throttle crack / Tip-in Rich Lean Spike tuning help

[h4x0r]

Hi guys. I need help with a condition i believed is known as Throttle crack or Tip in. Basically when the car is cruising at low speed with a closed throttle and i press the accelerator pedal a little the engine will gasp/surge a bit.

I'm running 11p with a 424 on a 304 V8
Siemens 60lb injectors
Turbo and turbo cam

I have tuned the VE first by steadily cruising around and it seems bang on 14.7 most of the time. Now im playing around with Transient stuff like accelerator enrichment.

If you look at this log you can see i'm cruising and AFR is bang on 14.7 until I crack the throttle open a little and you can see the car spikes rich to 13.7 and then leans out to a little over 15:1. The engine responds with a sudden hesitation:

throttle_crack_tip_in_rich_lean_spike.png (39.01 KiB) Viewed 1521 times

What do I need to look at? I've been playing around and not really getting anywhere

Is this an AE (acceleration enrichment) vs rpm table?
VE is still out?
Tip in Spark?
IAC throttle crack?

Quick Video clip of this engine dash log (0.25 speed): https://imgur.com/a/X7GDv9m

[immortality]

Have you tried reducing the AE Decay factor a bit?

[vlad01]

You can also look at manifold fuel. Looks like the Man fuel vs the AE are out slightly in opposite directions? The rich spike is more than likely manifold fuel being pulled in, and once that runs out the AE is all that doing the work.

I can't recall exactly, but Man fuel might have other factors linked to it including AE itself. I haven't touched that setting in years other than seeing what it did.

[Deuce]

Hi guys. I need help with a condition i believed is known as Throttle crack or Tip in. Basically when the car is cruising at low speed with a closed throttle and i press the accelerator pedal a little the engine will gasp/surge a bit.

I'm running 11p with a 424 on a 304 V8
Siemens 60lb injectors
Turbo and turbo cam

I have tuned the VE first by steadily cruising around and it seems bang on 14.7 most of the time. Now im playing around with Transient stuff like accelerator enrichment.

If you look at this log you can see i'm cruising and AFR is bang on 14.7 until I crack the throttle open a little and you can see the car spikes rich to 13.7 and then leans out to a little over 15:1. The engine responds with a sudden hesitation:

throttle_crack_tip_in_rich_lean_spike.png

What do I need to look at? I've been playing around and not really getting anywhere

Is this an AE (acceleration enrichment) vs rpm table?
VE is still out?
Tip in Spark?
IAC throttle crack?

Quick Video clip of this engine dash log (0.25 speed): https://imgur.com/a/X7GDv9m

Yeah I'm pretty sure I had similar until I edited the decay to remove the lean spot, and adjusted the AE to reduce the richness spike.

[h4x0r]

Updating my progress with trying to solve this as its been a struggle

I believe the downward spike is caused by AE (accelerator enrichment) and from all my logs this appears to richen the car for only 1/4 of a second.

ae-fuel-decay-factor.PNG (16.28 KiB) Viewed 296 times

I've reduced my AE Fuel Decay factor(% ref period) vs coolant temp from the factory of 95 down to as much as 50 and it really doesn't delay it that much

ae-gain-vs-delta-manifold-fuel.PNG (14.74 KiB) Viewed 296 times

I experimented with the manifold fuel. The factory 11p is 0.28. I reduced it to 0.1 and I could see a minor lean effect. Then I increased it to 0.5 and did see a minor rich effect. Its window of influence seems to be very broad and not really specific to this problem.

I also increased the overall amount of AE fuel by increasing the values in the table: AE Temperature factor vs Coolant Temp but again I think the AE window is too small literally less than half a second to solve this.

I think my approach to tuning VE was wrong. I'm road logging wide band data. I would go on long drives to get a lot of data and simply just save the averaged VE to all cells. This averaged data seems way too lean for load conditions (low rpm) so I decided to cherry pick data from the logs where the car was under load and the accelerator pedal was steady state. The results were now VE cells with much richer fuel. Especially where I circled in the VE table. This seems to be the area where the car was under more load from low rpm low speed driving

The richer VE cells now makes the car much crispier and snappier when gently accelerating.

The only other strategy I can think of is it make AE come on with less pedal sensitivity and keep increasing the decay delay but I really think this is just a VE problem.

Does this sound like the right approach?

[hjtrbo]

I think my approach to tuning VE was wrong. I'm road logging wide band data. I would go on long drives to get a lot of data and simply just save the averaged VE to all cells. This averaged data seems way too lean for load conditions (low rpm) so I decided to cherry pick data from the logs where the car was under load and the accelerator pedal was steady state. The results were now VE cells with much richer fuel. Especially where I circled in the VE table. This seems to be the area where the car was under more load from low rpm low speed driving

I don't know anything about the ECU you're tuning.
Generally you would use fuel trims over a wideband. Wideband would only come into play when you're into open loop power enrichment. The log data needs to be filtered (e.g. using MegaLogHD) to exclude abrupt throttle movements and when fuel cut-off is active etc.

[h4x0r]

I don't know anything about the ECU you're tuning.
Generally you would use fuel trims over a wideband. Wideband would only come into play when you're into open loop power enrichment. The log data needs to be filtered (e.g. using MegaLogHD) to exclude abrupt throttle movements and when fuel cut-off is active etc.

Thanks this is the guidance I was looking for. I downloaded MegaLogViewer HD as its compatible with tuner pro. You just need to export the log file to csv. It was easy to use following this video:



MegaLogViewer HD trial is limited to 400 data points but it was enough to show me that VE was too lean in my old logs and my cherry picked data to calculate VE was way better. It also confirmed my thoughts that road tuning using a wideband means I need to be be far more selective with my log data and only use data points where the TPS & RPM is in a steady state and the car is under load. I did read an old post from VL400 that using hills is great for this. I'll Ignore everything else such as pulling off the pedal, coasting, rolling downhill etc that data was causing my VE calculations to be too lean.

I'm confident I can keep using the calculated VE table in TunerPro with the cherry picked data now.