Discussion and questions related to the course Understanding AFR
Hey guys I’m finding it super hard to relate to your course stand alone ecus I came to the course to learn how to tune my microtech Lt16c an I know you don’t really use them much but the ecus you guys are using have completely different chart setups an I’m really struggling, I have a rb30 turbo on e85 with 1500cc injectors, I have gotten it to run and I have timing set pretty good it’s just the fueling side I’m struggling with for example my load charts says 10”hg and 3.00mS where as yours don’t have that so it kind of hard to understand, I will show you my load charts.
I can get the car to run at the perfect afr using mixTRM mode an turning the whole fuel supply down to -40% but I wanted to do it the proper way an actual turn the injectors down according to rpm not over the whole chart if that makes sense.
I pretty much wanna know when using a microtech what’s the best way to set fuel supply at idle an throughout rev range because currently I can get to idle good but under load it misses an sounds abit rough because its lean.
Your microtech uses millisecond-driven fuel delivery opposed to all modern ecus which have the option to use VE(the numbers that are confusing you), millisecond, MAF, and modeled.
These should help
The microtech is unfortunately quite unique in their approach and hence it can be a little tricky to directly relate to the ECUs in our course. Here's a very rough 'quick start' guide to understanding the fuelling in the normal mode:
The microtech uses an across the board 'injector pulse width vs load model' which is your load table. You're simply defining at each load point what the base injector pulse width will be. Of course this doesn't account for the fact that the engine's VE (airflow into the engine) also changes relative to rpm so there are two correction maps available - WOT and Cruise which allow you to make percentage changes to the base injector pulse width vs engine rpm.
Ideally your overall mixture trim should be 0% and if you need to remove 40% to get the engine to run nicely then you should start by reducing all the zones in your load map which will achieve the same aim. Generally I will run the engine at around 3000-4000 rpm on the dyno in steady state and move through each load point and tune to achieve my desired target. Then you can make adjustments in the cruise and WOT maps to keep your fuelling correct under these conditions. Understand that this is a relatively crude approach to tuning and your results are never going to be absolutely perfect but a microtech can get the job done. Just don't expect factory like cold start, idle control, or driveability.
The first ECU I bought to play with and tune was an LT8 after fiddling with a lot of rotary powered E prod cars using Bergs/Weber IDAs. I always had good luck treating Microtechs like a digital carb if that makes much sense. I guess you could also kind of say that their tuning strategy is analogous to dynamic jet/e-tube sizing or something.
@David, I personally liken tuning a microtech to attempting brain surgery with a meat clever but then that's just me I guess :)
@Andre, I was trying to be diplomatic :P (brain surgery with a broadsword maybe?)
I have got the car running very good and on power- “30psi” it runs perfect and I have lambda at 0.75-0.80 to be safe , but when the car is at 0hg and 2hg its very tricky to get it to run perfect it runs at 1.05 lambda and sometimes leaner I understand why you say Microtechs aren’t the best ecus the functions you have to work with make it very hard to have the perfect lambda thought out the rev range, I have been playing with matrix mode an it looks like I will be able to really fine tune it but will be a lot more work, but at least I can tune throughout the rev range not just the vaccum map
This is why I was referring to it as a digital carb. For me, I tended to hack something together where it ran very well under one condition, but was never quite right on others (power vs light load for example, and as you've found). Are you able to post a screen shot of your fuel tables/trims? Maybe a few more sets of eyes might find a solution or path to a solution.