jcorenman

Cool, that has to be the ultimate sleeper!

Yep, you can only tune for the environment you've got. But I forget... do you have a Sharktuner yet?

ptuomov

Yes, I'm an early adopter of ST2.

I'm just going to drive it for a while and write down some impressions before even looking at the logs or maps.

ptuomov

Solved the idle problem today with Jim Corenman's help. I had to get a new notebook computer and set it up, which was probably the most time consuming part of the project. Once I got the Sharktuner 2 hooked up, I did some experiments by myself and fixed some basic issues with the idle ignition map. Call this the zeroth step: make sure your idle ignition map is V shaped or U shaped with a downward slope of ignition advance as a function of the rpm in the idle range of rpm. With that fixed, it was time to give Jim a call and screen share to get the JDS idle controller calibrated. The controller is very logical if you've ever used a proportional-integral-derivative/differential PID controller (and it remains logical even if you don't understand it!). The first step was to decide the target idle rpms for different operating conditions and record them in one open-loop map that produces the target rpm value. The second step was to calibrate the open-loop base ISV% for each target rpm at each operating condition. At this point, the car would likely idle correctly without any PID control (or those parameters set to neuter the PID control), just based on the V-shaped idle ignition map and the open-loop idle calibration. This open loop controller provides the feed forward control to the PID controller by varying set point. The third and final step was to ad hoc calibrate the PID controller parameters to known good values and deviate a little from those based on the special circumstances of my car's engine. Thanks, Jim!

Tony

how do you switch between open and closed loop for the tuning...

ptuomov

It's built into the JDS idle controller. Basically, it's always an open-loop map for the target rpm and then an open-loop function and a PID control to control the deviation from the target rpm. You could make the PID control parameters such that the PID controller has very little impact on the ISV % and that would then just be open-loop idle controller.

Tony

i wired a switch in to disable the O2 sensor input when tuning. Just disconects it.

dr bob

I'm not sure I've ever heard of or seen a "partial-integral-differential PID controller". Is there some background available on this?

ptuomov

I mistyped it. I of course meant proportional-integral-differential (or derivative) controller. It's an age old controller that can be implemented in all sorts of digital and analog computers whether mechanical, electronic, hydraulic, etc.

In case someone is interested, here’s where I ended up:

Thom

V or U shaped?
We want an upward slope of timing when engine speeds falls below the target idle speed, but a downward slope when engine speeds shoots over target idle speed.

AFR of 10.95 at idle?

ptuomov

Fiddled with it some more. The prior belief is that if Porsche can get the GT cams to idle at 775rpm, I should be able to get these Elgin 65-6 cams to idle equally well at 800rpm. I think we met that goal:

ptuomov

Yes, downward sloping in the idle rpm “hunting” area and then rapidly upward sloping at higher rpms above the idle hunting area.

A picture is worth a thousand words:





The WBO2 controller is not hooked up, so that’s a default value. The narrow band fluctuates so it’s almost exactly lambda 1 with 93 octane MA E10 pump gas at idle.

Thom

?... I said the opposite - when rpm overshoots the target idle speed we want a downward ignition curve slope above the target idle speed, obviously only active when idle mode is enabled.

ptuomov

Hunting area = 500-1000 rpm.

At high rpms when coasting with the throttle closed you probably want to give it 40-50 degrees of advance? With deceleration fuel cutoff it probably doesn’t matter that much, but for the sake of the principle.

Tony

but them you dont get that nice gurgling pop pop in the exhaust....i left mine on.

ptuomov

Q: How do you merge into 90mph highway traffic when you are initially traveling at 45mph?
A: Slightly sideways.