I was wondering if someone could take a look at my AFR table that I'm going to be using with the autotune feature of megatune. It is my best guess from experience and what I've gathered off various forums.

My car is a 87 TII with a streetport, 89 rotors, 3" turbo back exhaust, no cats, stock turbo, front mount intercooler, 1000cc secondary injectors, an adjustable FPR, K&N air filter, and the air flow meter has been removed. I'm only running about 10-12 psi in boost, so the values in the table above that are for boost spikes.

I've been using a megasquirt version 2 board with the 29t extra code and megatune 2.25. I've been using fuel only and have gotten tuned sorta close using the datalogs.

Any input is welcomed.

JC

 

I am no expert but your #'s seem alittle high, I try to keep mine from 0-10 psi I have it set to 11.5 then 11.0 at 15+. This has worked well for me so far.

 

DO NOT use autotune, or run closed loop on boost.

The MS closed-loop algorithm causes slight oscillations (and doesn't react very quickly) in the AFR when it's active. This means if you're tuning close to the edge, it might go a little lean, and cross that edge. Personally I wouldn't trust ANY standalone EMS to do closed-loop on boost.

Instead I recommend starting out really rich on those parts of the table, and hand-leaning them out as you need to. Run open-loop above 100 kPa as well.

Ken

 

Ok, how about using the VE analyze function in Mega log viewer 2.52?

 

You'll have to read the docs on that. I'm not sure if it works without closed-loop. IE I think it uses the EGO correction % to calculate the new VE amounts.

 

VE analyze uses EGO correction %, which is locked at 100% in open loop. I'd recommend going through the datalog, and hand-tweaking the high load points based on WB AFR.

 

Alright, it seems the safest and best way to tune the upper reaches of the VE table is the way I have been doing it (scanning datalogs and making tweaks). Does my AFR table at least look like good targets to aim for???

I know that the O2 readinds lag the actual conditions that the engine was at to produce the O2 reading. Does anybody have an idea of what that lag is? I'm using a techedge wide band sensor.



Thanks,

JC

 

generally you can tell this by looking at your datalog.

blip the throttle, then look in the datalog and see how long it takes AFR to change after you blip.

For most of the engine's I've worked with, it's about 200-300 ms.

 

Those targets look safe.... although maybe a little rich up top for best power... depends on your ignition timing too though along with many other factors.

 

I don't think that's the case. It does its own analysis of actual AFR vs target, factoring in delay in AFR measurement, hit count, proximity to bin points, etc. You can even change the AFR target an reanalyze to get different results. I've had good luck getting an approximate map while running open loop.

 

hrmm, I'll have to ask Phil next time I talk to him (the guy that wrote it)....

Or see if he makes source-code available.

I think if you're running closed loop he definitely uses the EGO %... otherwise he wouldn't be able to calculate a proper value.

 

You are correct, I spoke too soon. The earlier auto-tune, or VE table modification applications were EGO% limited, but it looks like Phil has raised the bar. That MegaLogViewer is a truly amazing piece of work! For those interested in the details, his algorithm is detailed here:

http://www.ideasandsolutions.biz/Meg...eAnalysis.html

 

After looking at the formula, it uses GEGO and AFR at the same time. If GEGO is 100%, it'll still make a change based on just AFR.

 

that seems pretty scary to me.
I like setting it well rich, and backing it off as i brake against the accell to bring boost up or hold rpm steady. best when you have a good driver, leaving you to tune..

i wouldn't trust going into uncharted high load areas without having eased into it and be ready to crank up the fuel or back off the accell quickly.

sorry if misinterpretated... it's just soo easy for a unknown car to step out, or turbo to quickly spool or likewise...

 

sorry to steal a thread.

but since its talking about this matter...here is the problem im having with this window.

my AFR target for VE table 1 shows up in volts im not to sure on how to change it to (AFR)
so reight now its
AFR Targets for VE table 1 (Volts) ive tried resetting it to default but nothing can make it go to the AFR settings

any help guys?
thanks

 

A bit old, but for anything under about 75 kPa I try to run approx 16-16.2 AFR since this seems to give the best efficiency (except at idle, where I cant seem to get it stable at any leaner than 13:1). right around 100 kPa I aim for 13-13.5 AFR, up to 12 AFR at 140 kPa and down to 10.5-11 above there. I think this is a bit conservative in boost, but I havent gotten to a dyno to tune it more safely.

 

no topless , i need help on setting up the window from VOLTS to AFR .

i found a link of what i have the same problem with and tried cutting and pasteing the ini file but the computer cant understand it. so im not sure how to set this up here is the link i mentioned.

http://www.msefi.com/viewtopic.php?f=24&t=30610

 

Sorry, I havent encountered that problem, im not sure how to resolve that... a suggestion would be to make sure that you're using one of the preset volts to AFR conversions in the configurator. That thread you linked to seems to be about the gauge displayed on the main page of megatune, not the AFR table anyway.

I just read the first bunch of posts and replied to what seemed to be the topic of the thread