Turbo M20 hard stutter under accel

[turbski]

Let me know if I did that correctly? I hate computers!!!!!!

[Digitalwave]

The link is not set to public access.

I echo one of digger's question. Does your tach drop out to 0 when this happens? You can also use the composite tooth logger to see if you're losing crank position sync when this happens. It can be a common problem, since these old CPS and dried up harmonic balancers can cause sync issues.

[turbski]

The link is not set to public access.

I echo one of digger's question. Does your tach drop out to 0 when this happens? You can also use the composite tooth logger to see if you're losing crank position sync when this happens. It can be a common problem, since these old CPS and dried up harmonic balancers can cause sync issues.

Send me your email. I believe you and jaxx helped me load the last log I had trouble with.
there is 0 counts of cps loss in the log. Only 2 hard afr spikes under wot

[varg]

Spark "blowout" is the simplest and most likely cause. Check your plugs, regap them down to 0.020" if needed. At 200kPa you're pushing the limits of what is reliably possible with what I'm assuming is the stock ignition setup. If I'm correct in my assessment of your ignition setup, you'd be well served in doing a wasted spark conversion.

[turbski]

It is set up for wasted spark. But I can re gap the plugs and see if it makes a difference.

[turbski]

https://drive.google.com/file/d/1j2su-JTmMoSOMAaIZ-fGIPGVIgl9CfSM/view?usp=drivesdk

[turbski]

I made it public I think?

[Jaxx_]

It looks like you have MAP decel enrichment taking out 10% of fuel when you have this issue? That's my best guess, anyway. The quickest fix would be to be sure that the MAP dot AE line (pictured below) doesn't go below 0% (e.g., the left-most blue dot on the left graph)

Alternatively, you can move the slider under the two graphs all the way to the right to select TPS dot AE only.

[turbski]

I'm having trouble finding that exact graph. I did find decel fuel cut set to 90% under tps based ae.

[turbski]

And you will have to excuse my ignorance but please explain how this setting has effect on performance? Or what it actually does

[Jaxx_]

My apologies, you're on MS2, my screenshot is from MS3. I think you corrected the right setting.

The idea of acceleration enrichment or decel enleanment is to correct for transients that are too quick to be captured by, for example, the MAP sensor alone. You can think of this as supplementing the base fuel map with additional fuel when moving through the map rather than "steady state." What I understand is really happening is supplementing puddle of fuel on the intake port to reach equilibrium while supplying also enough fuel for the engine to accelerate.

Acceleration enrichment is adding fuel on top of the base fuel map to ensure the engine has enough fuel for acceleration.
Deceleration enleanment is removing fuel from the base table when the engine is decelerating. This is mostly to prevent extra fuel being thrown into the exhaust and aid fuel economy. In some conditions, the accel or decel settings are too aggressive and kick in during regular driving, which can lead to stumbles.

You'll see OEM cars puff a black plume out the exhaust when accelerating hard, often this a side effect of unburned fuel in the exhaust because of the aggressive AE.

Here's a video on tuning AE with megasquirt if you are curious, just to understand a little more of what is happening. (Opposite theory applies for DE, but isn't as critical to a well-driving car)

https://www.youtube.com/watch?v=HSE3CxaWF-I

[digger]

it would be good to see of video of the problem to identify if its a misfire or actual momentary cut-out

[turbski]

My apologies, you're on MS2, my screenshot is from MS3. I think you corrected the right setting.

The idea of acceleration enrichment or decel enleanment is to correct for transients that are too quick to be captured by, for example, the MAP sensor alone. You can think of this as supplementing the base fuel map with additional fuel when moving through the map rather than "steady state." What I understand is really happening is supplementing puddle of fuel on the intake port to reach equilibrium while supplying also enough fuel for the engine to accelerate.

Acceleration enrichment is adding fuel on top of the base fuel map to ensure the engine has enough fuel for acceleration.
Deceleration enleanment is removing fuel from the base table when the engine is decelerating. This is mostly to prevent extra fuel being thrown into the exhaust and aid fuel economy. In some conditions, the accel or decel settings are too aggressive and kick in during regular driving, which can lead to stumbles.

You'll see OEM cars puff a black plume out the exhaust when accelerating hard, often this a side effect of unburned fuel in the exhaust because of the aggressive AE.

Here's a video on tuning AE with megasquirt if you are curious, just to understand a little more of what is happening. (Opposite theory applies for DE, but isn't as critical to a well-driving car)
https://www.youtube.com/watch?v=HSE3CxaWF-I

I will do a bit of homework on this. I want to understand fully what I'm experiencing as to save a motor from scrap. I don't have another 5k to drop on a block and head. I'd rather learn slowly and drive without having to prove anything ..... It's faster than most cars I roll by as it is.

[turbski]

it would be good to see of video of the problem to identify if its a misfire or actual momentary cut-out

I can make that happen. As I said above I don't want to destroy an expensive piece for the sake of proving anything. I might already have a video of the car providing a sample of this in the wife's FB page. I will take a peak.

[turbski]

Changed the plugs out yesterday. Ngk bpr7es. Gapped to .023" made a difference in idle but not much else.
next step is a test light and will probably pull and inspect in tank low pressure pump.