VE Analyse Live - Lambda Delay

For discussion of Phil Tobin's Tuner Studio software (Only about the tuning software itself, not about how to tune or firmware features)

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NigeT
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VE Analyse Live - Lambda Delay

Post by NigeT »

Can anyone recommend lambda delay table coordinates (MAP and RPM) suitable for a turbo MX-5 with rev limit at 7000rpm?

I understand that the delay will vary with the speed at which the exhaust gases move through the system and that this will be in some way relative to RPM and pressure (and restrictions) but I don't know what the curve would look like or how TunerStudio fits a curve to the 3 points in each dimension of the table. If it extrapolates linear curves between the points in each dimension then it suggests that the middle coordinate in each dimension needs to identify a knee point.

Additionally has anyone got any lambda delay tables that they care to share? Ideally for an NA8 MX-5 (Miata) with Flyin Miata FM2 manifold, 2.5" turbo elbow and downpipe, GT2560R turbo and the wideband sensor in the boss back just before the catalytic converter.

Many thanks,
Nigel.
Rick Finsta
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Re: VE Analyse Live - Lambda Delay

Post by Rick Finsta »

This is really simple - take your engine to a given speed, let the AFR stabilize, and then induce a transient. Look at the data log and see how long between the commanded PW change and the AFR change. Do this at a few points and then connect the dots.
NigeT
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Re: VE Analyse Live - Lambda Delay

Post by NigeT »

Thanks Rick. My question is more about how to choose the best RPM / MAP points to induce the transients at in order for TunerStudio to generate the best fitting curve (surface really I guess).

Do you find fuel cut transients easiest to read?

Thanks again, Nigel.


Nigel
Rick Finsta
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Re: VE Analyse Live - Lambda Delay

Post by Rick Finsta »

Gotcha. I just adjusted the top and bottom for my engine's operating range and then stuck one in at cruise RPM. I think like 2000RPM, 3700RPM, and 6000RPM is where I ended up but remember you can always change it for each tuning session as you get your VE table dialed using the filters to make sure you're not getting changes outside your focused area.
NigeT
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Re: VE Analyse Live - Lambda Delay

Post by NigeT »

Hey Rick, could you post a log sample or image showing a transient and the points you measure time between. I think I know what I'm doing but it would be nice to be sure. :-)
Rick Finsta
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Re: VE Analyse Live - Lambda Delay

Post by Rick Finsta »

I'm just starting on a fresh tune after a cam swap so it's a great time.

This is just a quick one I grabbed in the driveway. In the first picture you can see the TPS and MAP start to change. I ignore the actual AE trigger event when I'm looking for lean spikes (need more AE) and look only at the event that caused it - throttle opening. Note that cursor is at 603.238 and the RPM is about 1400 and MAP around 54kPa.

Image

Now the second one you can see that when the AFR starts to drop (remember this was a place where I knew I needed more AE so I look for an AFR drop) I am at 3800RPM, 603.742 seconds and MAP is 46kPa.

Image

So in this one example just starting out I'd just go to the halfway points and set the values there. So let's say 2300RPM and 55kPa I'd stick a 400mS number in there. That's about all you can do in the driveway is try to duplicate it at a few different RPM/MAP numbers and see what you get. Honestly you really need to be chassis dyno or road tuning to be able to really get the car from one spot to another in a few different scenarios, but I've found that it is pretty easy to do if you just cruise around a bit without VEAL on and then use Megalogviewer when you get home to find a few different places that span the range you drove in and then enter them into the table and run the analyzer. It's not precise, but I've found after a few drives I start to see patterns and get the numbers dialed. I'd love it if someone else had a more definitive way!

ETA: you have to set the MLV lambda delay by also using filters - you filter out all the points outside of the range you're figured out the delay for and then run the analysis. Eventually you put them into the tables in TS VEAL.
pit_celica
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Re: VE Analyse Live - Lambda Delay

Post by pit_celica »

If you want to induce a transient that does not affect RPM or MAP (like a TPS event), then you may consider the use of a switch to toggle between 2 different VE table. The switched VE table would be richer than the 1st one all over the map (I would say that 25% richer would be a good starting point).

Set the RPM and MAP, toggle the switch 5s ON, then release it to get back to the original VE table. Look at the datalog for the time between the VE (and PW) change and the actual AFR rich transition.

Repeat at different RPM/MAP combination.

Sam
NigeT
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Re: VE Analyse Live - Lambda Delay

Post by NigeT »

Thanks Rick, you are a star. Actually that is pretty much what I have been pulling out of logs - but I've been looking at the change in duty cycle. I think your method is better though - the throttle opening immediately makes the mixture lean then duty increases to address this (even if your AE is working - which mine isn't - it must surely always slightly lag), so then you get the lean spike. So throttle open to start of lean spike should give the delay. I did wonder if throttle lift events could be used, but I imagine that they might have a slightly larger delay anyway.

Thanks Sam too, your suggestion is great - no change in intake air, just fuel change. Should be easier to match the transient leading edge of PW to that of AFR. Nice. I can temporarily re-purpose Nitrous in from switching boost tables to switching VE I guess.
Rick Finsta
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Re: VE Analyse Live - Lambda Delay

Post by Rick Finsta »

I really like the fuel switch idea, too.
thedrew
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Re: VE Analyse Live - Lambda Delay

Post by thedrew »

wouldn't it be cool if MS and TunerStudio could do this automagically? Like have a "analyze" mode and it would do a fuel cut for like 100ms every 10s or something. Then TunerStudio could pick up how long it took to see it in the exhaust stream and fill out the table for you.
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NigeT
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Re: VE Analyse Live - Lambda Delay

Post by NigeT »

That would be very cool, but probably pretty hard to implement. I think it would need to take a load of samples and then extrapolate a table from them - some rpm/map combinations are pretty hard to achieve (at least for me).
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