RomRaider

I'm seeing up to a full second in some cases between what the ECU says it's doing and the reading from the LC-1, i.e. stays rich long after you're at no throttle. So if you have a peak in your MAF scale, you see a bump in the AFR, but you have no idea at what MAFv it happened at. This makes it very hard to tune the MAF scale.

How much is physical latency and how much digital?

I have not seen this delay myself - mine is almost instant with the LC1 in the downpipe immediately after the turbo.

Where is your LC-1 located?

right past the turbo, Cobb DP.

I've been disappointed with datalogging in general, just too much noise and skew, but I figured with the higher sample rate of the LC-1 this has wouldn't be so bad, but since it's a seperate source the problem seems to be magnified, I assume the issue is still in the ECU.

I'm thinking perhaps I should insert a large rich spike into the MAF scale, so I can use this to synchronize the two logs, like a clapper at the begging of filming. However could still have very bad jitter.

*edit* well now that I think about it, it doesn't really make sense for the LC-1 to report rich a second after we're off the throttle and not be the LC-1's fault, right?

Post a log of what you're seeing. If you try to only like a couple parameters with the RR logger, you'll get a higher sample rate. Try one with only like RPM, Throttle, and LC-1 AFR.

I'll try this later. It would be nice if logging didn't compromise to the device with the lowest sample rate (SSM).

I have my LC-1 located farther downstream near my rear 02 sensor and I notice its a little slow to respond when I get off the throttle. I'm hoping that when I'm on the throttle and things are most important, the speed of the exhaust is higher and there is less of an offset between cylinders and downpipe.

I don't see much of a delay.

nice... where is your sensor located?

Looks like almost 500msec.

The bung on a Cobb cat'd DP.



Looks like ~200ms to me.


Part throttle data with Front O2 included.



How are you trying to scale your MAF?

AFR interpolation on your spreadsheet + LC1.

What firmware are you running?

If you are referring to the LC-1 firmware, I am using the 'older' version that shipped with it more than a year ago. The new firmware is only supposed to speed up the warm-up phase, I think.

A comment about MAF scaling...I have seen some strange AFR behavior at part-throttle where I would see a "bump" in the AFR but it shifts relative to MAFv as I increase the throttle. I think it has something to do with resonance in the intake system.

I have my wideband pretty far back. The delay is high at idle, moderate when cruising, but very low when flowing a lot of air.

Ok, after further examination I see what's going on, should have been obvious. The latency is highly variable.

I put a marker in my MAF scale at 3.83 volts, 7% rich. At this flow it's about 200ms behind, but as the throttle closes the latency rises. Anyone know or calculate the relationship between flow and latency? Using this to correct the data is necessary to properly tuning the MAF scale, at least without thousands of iterations.

not sure i understand the issue?

at part throttle you should be using the front o2 sensor. it is upstream and easy to log.

at full throttle you should be using your wideband. latency is not constant (as you've discovered) but at the maf rates you're seeing it's a couple of hundred ms max.

you should not be attempting to tune fueling and/or maf at all during throttle transitions.