ACE1252

It's in USB mode. Wifi mode appears to be even slower. This is just looking at the screen updates. I have not logged Wifi to compare timestamps between each PID update.

ACE1252

Here are a couple of threads from the ScanXL forum on the data sample rates.

Max sample rates seen with ScanXL Pro
max sample rates of DASH command and others

It looks like it's as fast as I can get it. For some reason the Autotap interface is around 5-10mS faster, but it's not the end of the world. I just have to log the minimum amount of PIDS that I need. I'm still playing with the ScanXL software and it is really nice. I do think it's worth buying if you need advanced LT1 scanning software. It's a hint slower than Autotap, but much better in the software department. Be sure to get the USB connection for the best possible rates(WiFi OBDLink has USB, but there is a USB only model for less cash). WiFi appeared to be really slow....but I need to log and look at the timestamps to confirm it.

ACE1252

Yeah.... I think I may be finally getting a handle on the Lambda vs AFR stuff. I've been wrestling with how to deal with the hard coded 14.7 in closed loop, vs what we can set in open loop and how that will shape the tune.

Seems that it does not matter. Even though the target AFR maybe 14.7 in the PCM, the O2's are going to auto adjust to whatever the stoich of the fuel in the tank is.....so even though the display target is 14.7....if the fuel is 14.3 or 14.1...that is "real" target. I've got a little more homework to do before I elaborate more....as many have said....tune in Lambda and forget AFR.

GaryDoug

In case this is relevant, I know that GM implemented two methods of requesting and returning the PID's, and that may account for the time differences. The basic one is the mandated OBD2 version where you request just one PID at a time and wait for the response. I have seen an overall time of about 20ms for that mode. The other, which is the one used by the TechII, is to "program" the PCM to send a batch of PIDs, then request that batch. Of course, if you are just doing one PID there is no change, but if you are doing several, they all come back at once and the average time per PID is less. I know that ScanXL uses the slower mandated mode, not sure about Autotap, but if it uses the TechII method, it could be faster per PID.

AdsoYo

Huge thanks to you ACE. This thread helped me dial in my injectors after 24x.

ACE1252

I messaged you back, I'm glad it's helping.

Lord willing, I'll jump back on working with my Z28 on this tune stuff in the near future. Medical issues suck, but they are the priority for the moment.

I own a Tech 1 tool now, so that will help me verify some readings. It most certainly has helped me get the air out of my ABS modulator. Nice to have a good feeling brake pedal again.

Jaxem

Really great stuff in here, hopefully these offsets help tighten up how my LT1 runs, i was curious if you ever figured out your low speed bucking as i'm experiencing the same thing

ACE1252

Not yet. However, I think things are lining up well for me to rent some dyno time this year. I also plan on getting a second wideband to monitor both banks as I do the tuning(might be overkill though).

I've let this issue drag on for years, but it is only at very light tip in, off idle, around 5 mph(much more pronounced when stone cold...ie open loop). Driveability everywhere else is really good.

I plan on tuning what I've got soon as I've got the cash to get the spare set of heads I have ported by Advanced Induction. I want to try and get what I have right, before moving on to another combination.

That way, I can properly tune my new combo.

troutdog311

Thanks for the info. I have been trying for some time to dial in my 0280155811 injectors on a 94 ECM until I gave up. I just started doing some more research a few weeks back and found this thread.
I'm trying to make this short and sweet but I can post the complete offsets if needed. The only info I can find is for the 0280155868 "They say is the same as 811" Injector Offset but is way higher usec than I had originally found awhile back. An example, I had 701 at 12v and going by what someone put on another site the 868 is 1037 at 12v for the LT1 ECM and haven't run it yet. I've been using the stock adders because I couldn't find or understand what to do in that area. I have made a bin file changing the adder using the graph in post #20 which is for the 30# injectors but willing to give it a go.
Not going into the whole thing at the moment but for the last year I have been running OL SD and really like it. The first thing I tried addressing "after the flow rate" 1 year ago was the offset and adder for these 36#s but gave up a long time ago. I did get what I believe to be close offset setting from a friend who uses these tho the adder stayed stock. I did many many hours of tuning OL AFR, PE, VE, Timing and such. I just feel like I'm still having issues with them. Any idea what these 811 Inj should be set as?
Excuse my messy chatter. I'm home sick today and just doing some research. Thanks

ACE1252

The short answer to your question is that if you don't have a datasheet that characterizes the injectors, the only thing you can really do is guess at what settings they need.

That's why I went with Ford injectors. They provide characterization data for them(called "Calibration Summary"). Props to Ford Motorsports for putting that data out with the injectors they sell.