Specific CL tweaks when overrun-to-idle situation

Give input on tuning as well as any tips and tricks you may have. Also feel free to share base mapping files for various engine types.
FrankCorrado
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Specific CL tweaks when overrun-to-idle situation

Post by FrankCorrado »

I bet 1 million bucks... no wait.... quids, I bet a million quids Rick will jump on this one. :D loll Which is a good sign!

Since I run DTA I've always had difficulties with CL at the precise moment you press the clutch and let the rpms drop to idle. Which is what we all do at a stop sign, red light, emergency braking, traffic, etc... well not me, I always need to lightly touch the gas pedal so that rpms would smooooothly drop on a pillow, giving, I think, enough time for CL to understand the situation it is in.

Most of the time the CL thinks the engine runs too rich and leans it out a shit load so the rpms drop one shot to 0 and engine dies. See attached pic for example:

Image

Green line vs the White line in 2nd swim lane from the top.
Green is ACTUAL AFR and White is % CL is correcting fuel.
In the top swim lane you see the RPM in Yellow.

So CL was removing fuel by up to 15% (the max I set in CL settings) when the engine did not need it while rpm was dropping. Hence it reached 18AFR and stalled.

Now I don't want anyone to tell me "put value x in cell y and that'll solve it". I know it's not that easy. loll I just want your opinion as which setting(s) could come into play for CL to behave this way. Could it be sample rate? PIDs? Overrun CL settings? TPS CL settings? Others? A combination of many?

Or maybe I just need to finish up my fuel map and cut the max decrease % to 5%, preventing CL from removing too much fuel? Maybe, but should CL react fast enough anyway without stalling? I dunno, just asking...

And FYI Rick, yes I still have CL making, sometimes, "frequency waves-like" adjustments when cruising, you know it bounces up and down from say 14.2 to 15.2, while trying to target 14.7 (but no more than 0.5AFR both ways). So maybe I need a perfect PID in order to not have CL take off 15% when rpms drop to idle... just asking if my thinking is right, here.

tnx
Frank
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Re: Specific CL tweaks when overrun-to-idle situation

Post by VR6Turbo »

Trying increasing the over-run lock time so that's it not trying to mess with the fuelling when you dip the clutch. Might also be worth increasing the "Idle PID delay after over-run" time for the same reason.

Remember also that when you're on throttle zero coming down through the rows, the cells before your idle cell will influence the rpm behaviour. Very low timing means the revs will drop like a brick if the idle valve has a small PWM at that rpm. A decent amount of timing will help prop up the revs and will fall more gracefully. You also need the right amount of fuel in these cells too.

If you can get it behaving nicely in open loop, then it will also behave nicely in Closed loop.

The OE strategy for this scenario is low timing and lots of idle valve PWM and matching fuel. I think you have it the other way round don't you? More timing and less PWM? They also adjust ignition advance as well as the idle motor, so doubles the chances of catching a stall and gives a more stable idle speed.
FrankCorrado
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Re: Specific CL tweaks when overrun-to-idle situation

Post by FrankCorrado »

So it may not be CL related after all. Will have to check with those different values.

Currently I have this:

Image
Image
Image
Image
Image

Now let me analyze this, I'll be back.
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Re: Specific CL tweaks when overrun-to-idle situation

Post by FrankCorrado »

Idle PID delay after over-run time (ISV)

This is at 3sec now and looking at my log in first post, the blue line, I can see the ISV kicked in when the rpm was at 833 and tried to get it out of stalling, but failed cuz the engine was getting leaner and leaner. In fact, I could even reduce it to 2sec as we can see the ISV immediately tried to increase RPMs, therefore if it could come into play 1sec earlier, maybe it would succeed, but I think it's chasing a tail here as we see it's SEEMS to be fuel problem, I don't want to cover that with an ISV, I want to fix the fuel problem.

Over-run lock time (CL)

That has good and bad effects. Yes it may help, but on the other hand it's less efficient when I shift gear and come back on the TPS. In those situations CL waits too long to come back, so my fuelling is not adjusted and the engine feels worse. Also if it waits too long when I come back on TPS after a gear shift it will not record the FC, hence making it more difficult to smooth out in that region. On the other hand, I could say "live with it and go on the dyno to fix it". Yes, I agree. I'll try just increasing that value first.
Thing is, in this situation I screenshoted above, it never went to over-run lock!! Check the purple line, that's TPS. It's never been under 4% and my over-run TPS position 2% as seen in the screenshot. So not sure what to do on this one yet. Need more testing.

Timing

On my timing map, I think the timing is high enough. Let's not forget that the MAP40 column is used when I start up the engine and idle, so the 750 to 1500rpm if I change them it will affect my normal idle timing or my start up timing. I don't think I could increase that much.

Open loop

It behaves good in OL, but not perfect, I know sometimes the rpms drop too much and then catch up, but does not stall. Maybe it needs to be better in OL. But if it does not stall, then CL is doing something to make it stall.

ISV PWM

My idle PWM seems ok to me as the engine idles fine. So if I change the PWM between 750 and 1250, it may screw up my normal idle, wouldn't it?
Don't forget I went the TPS way, I opened up TPS plate so that it could idle fine at normal temps without the help of ISV. If I increase ISV, it will increase my normal idle speed too.

Fuel

Maybe I could increase fuel, look at the MAP40 column between 1250 1500. But if I increase fuel for 750-1000, it will mess my normal idle. So I can only increase 1250-1500 (and lower startup fuel map at the same time, cuz it will hit the 1250rpm row). Not sure increasing only these 2 cells will help, as the problem is also when the rpm is dropping below 1000.
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Re: Specific CL tweaks when overrun-to-idle situation

Post by FrankCorrado »

Ok, here's what I did. Since I was not in an overrun due to bad settings (should have been overrun), CL never stopped working, so I must be carefully in what I adjust at the moment. All of these settings will be tested after March 15 2012, as by law now I cannot drive the car until that time (no winter tyres).

Timing

Sad the ISV settings don't allow timing adjustments based on %PWM, like it does for fuel. So I had to increased the main map 400rpm row (my top row) to 20-deg timing, as I can see on the logs that when the engine stalls, the MAP increases to 100, so I need timing there at 400rpm. I have adjusted the 750rpm row to have a nice interpolation between the 400 and 750 row for when the rpm is between 400 and 750.

Fuel

I have increased fuel a little bit on the 400rpm row from 60MAP to 125MAP. I need to test OL first, cuz like I said CL never went in overrun, so it removed fuel. In normal situation it should have gone to overrun and not remove fuel, if I add too much fuel based on that sole test here I will end up bore washing the engine in OL by too much fuel. :) More tests to come.

CL Settings

I have increased my Overrun TPS Pos from 2 to 5. Manual says 2-3% over idle TPS, my idle TPS is at 2. Using 5 it would have gone in overrun in the test shown above, which it should have.

I have lowered Overrun RPM Turn On from 1500 to 1100, which is 200rpm over idle when CL is in the temps of being turned on. Manual says 200rpm over. This will make it turn on later.
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Re: Specific CL tweaks when overrun-to-idle situation

Post by 86sixsix »

decrease CL freq to 12 unless you've *real* data that says you need it faster.

red-to-lock should be 5% unless you've a reason for it not to be.

lock times are timed from when you come *out* of overrun - not go *in*. increase them both if you have juddery hiccups like as if you've a greasy/oily clutch. they should really be set at however long you ride the clutch and a bit extra but we're evil and we drive on the regular roads so it gets a bit hard, that.

just fill the base-idle grid full of 80's and let your map sensor do the rest dude... (you want it to kinda 'hover' a touch (3-400rpm?) above your desired idle and then the PWM loop for the ISV will slowly pull it down to idle)

offtopic: do you 'map as load' folk not fake vaccuum advance dizzies and have more spark lower down? or is it an exhaust temp thing for the OP?

(edited a few times)
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FrankCorrado
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Re: Specific CL tweaks when overrun-to-idle situation

Post by FrankCorrado »

Excellent, so to whom I need to pay the 1 million quids for my bet? :)

12 was working good and I don't see any reason why I would need 18, so I will decrease it.

The Throttle Red to Lock to 5? I had a reason to have 20, but I now challenge it. When I had my bad cam sensor 5% was not smooth on the engine. Just changing to 20 made it a little better, just a little. Now that I have a more reliable cam sensor (for how long) I will try to use 5 again.

Oh crap yes, come OUT of overrun, no go in. Ok I will have to test that one and increase them if need be. Usually it's better to have same value for both fields, right? I judged that 0.5sec was my clutch ride time (hence the 0.7 as value), but I'll recheck.

For the ISV PWM grid I should put only 80s everywhere? So it drops over idle rpm and then the ISV PID Loop will slowly pull it down? That's a smart idea!
Then I have to adjust my Max PID Adjustment, it's at 7% now. So if I put 80 and it pulls down and locks to 73% but in fact it would need 40, I'd get a high idle. Won't stall though! lolll


I do MAP AS LOAD, yes. Found out it was easier to setup and play with my maps and prevented some rare situations from happening, we discussed with Kev a long time. That's mostly personal choice though, as discussed on the old dead forums.
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Re: Specific CL tweaks when overrun-to-idle situation

Post by 86sixsix »

FrankCorrado wrote:Usually it's better to have same value for both fields, right? I judged that 0.5sec was my clutch ride time (hence the 0.7 as value), but I'll recheck.
opens my map... 1.5 on the both of 'em.
FrankCorrado wrote:For the ISV PWM grid I should put only 80s everywhere? So it drops over idle rpm and then the ISV PID Loop will slowly pull it down? That's a smart idea!
Then I have to adjust my Max PID Adjustment, it's at 7% now. So if I put 80 and it pulls down and locks to 73% but in fact it would need 40, I'd get a high idle. Won't stall though! lolll
yeah dude...stick loads of 80s all over it and then (i guess your valve is similar to the thing i have) have like 50% as the adjustment... so you can go from 80 to 30. it'll probably idle at like a million revs and then slowly drop down... but you can work off that...
FrankCorrado wrote:I do MAP AS LOAD, yes. Found out it was easier to setup and play with my maps and prevented some rare situations from happening, we discussed with Kev a long time. That's mostly personal choice though, as discussed on the old dead forums.
no - i was just wondering. i might only be a ickle baby but i have old fashioned ways haha
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Re: Specific CL tweaks when overrun-to-idle situation

Post by FrankCorrado »

Yeah exactly, 50% is the max. Or maybe after trying I'll see that 70-20 works too, but starting with safer is better. Never thought about that, using ISV to the max and PID Loop to control.
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Re: Specific CL tweaks when overrun-to-idle situation

Post by VR6Turbo »

A PWM table full of 80s will idle at 3000rpm :lol:

A pid loop fast enough to bring that down to ~ 800rpm in a reasonable and unembarrassing time will need a big prop, which will mean nice hunting fun around 1000rpm when dipping the clutch.

The most important thing I found with idle is to have the same number in all the rows. Just lock the valve to a fixed number like those old school bimetallic air bypass valves.

With MAP as load you should get a super stable idle from that.
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