[QUOTE=usaf8ret;14881007]Yes that is part of it, but fuel is also a part of the equation. but like I said, go out and research the details. lots of info resources online that discuss engine Volumetric Efficiency and Delphi EFI in very complete detail. It's a bit OT to continue in more detail here.

 

[QUOTE=LA_Dog;14881046] I don't think you have a clear idea of what's happening with the VE's, what they represent, how they affect target AFR's, and how the closed loop system uses them to reach a target AFR. How many bikes have you tuned? Think about it for a minute. I install a stage 1 air filter and exhaust. What happens? Airflow through the engine increases, right. So what do I need to do? I need to reflect that increase in airflow via a VE number to achieve a target AFR. Doesn't the system need to know how much AIR is flowing through system? Doesn't it then add a certain amount of fuel to avhieve whatever my desired target AFR is? Every book I've read tells me that VE's are a representation of AIRFLOW through the engine. Fueling, as you put it, happens afterwards.

 

Going to add a little here. There really isn't a closed loop. Its a nickname given to the range of narrow band sensors. Lambda .977 to 1.0 or 14.34 to 14.68 afr, are the sensor's range. Maybe a little more. Wide band sensors will cover a larger range, and work just fine. Narrow band sensors were adapted to keep the EPA happy. So really anything with sensors could be considered "closed loop" from the carb days, lol! As far as ve goes I think it has to do more with cylinder fill. Yes there is more air flowing through the motor, but there is no real way for the system to measure it. There are sensors, how accurate they are is up for debate. It is an estimate based on what the engineers have programmed in. So when you change the charge dilution tables the ve tables change without ever changing the flow characteristics of the engine. it all calculations / math formulas.

 

Closed loop refers to the control strategy in that there is feed back to the system (O2s) that figure into fueling equation. That corresponds to a narrow band for "narrow band" O2 sensors. Outside that band, the closed loop ability is turned off because of the limitation of the sensors.

Volumetric efficiency is the percentage of actual cylinder volume that the engine can fill the cylinder at particular RPM/MAP or TPS. Auto tune calculates the VE. Pretty sure it backs it out of the fueling equation (uses the same equation, but solves for VE instead of injector pulse). So or VEs after auto tune are calculated. The VE table gets used to calculate the fueling requirements along with other input, like IAT, MAP, ET, and a bunch of other stuff I'm sure.

The CDE is supposed to be the percentage of pressure (MAP), that isn't from fresh air, but due to burnt gases getting into the intake tract (can overlap), but without really knowing how much it really is, we can use it to flatten our VE maps to lessen the differences between cells, so interpolations are more accurate to the actual need. It changes the culling calc, and if auto tuned after changing CDE it will change the VE tables.

Don't ask me how to do that, I'm still learning myself. I'm not a professional tuner (but have been a mechanical engineer for nearly 30 years, and a gear head for nearly 40. I just know enough to make myself a danger).

 

I like to think of VE as the last big fudge factor to get the AFR to hit the Target AFR. "Closed loop" is a constantly changing fudge factor to the VE to help the motor better stay on target.

We can get more technical if you guys really want. Here is something I wrote to help people get their head around basic EFI tuning.

http://www.nbs-stl.com/tuning/BasicTuning101.pdf

Andy

 

thanks for posting that Andy- this brought something to mind, over the years you've posted a lot of good info links, charts to spark tables, etc at the ntbs-stl.com website- but none of them work anymore. any chance you'll get that fixed? shame to have all that good info lost-

 

I have a new domain now. If you copy the old links and then change the nCs-stl to nBs-stl most of the old links will work. Yep, one letter changed in the link....

Andy

 

[QUOTE=usaf8ret;14881104]Respectfully, I think you have a handle on only a very narrow slice of the overall tuning picture and what the VE tables represent in the tune as a whole. You're not incorrect, but you're not completely correct either. Start with Andy's pdf above and have a run through it. All of this will make more sense once you grasp how the EFI components, tables, etc relate to each other in the tune.

This is also a very decent guide and read on the entire HD Delphi system and each of the components: http://files.meetup.com/19315510/EFI%20Basics.pdf

 

Thanks Andy- you are one of the few treasure troves of tuning info out there. just a thought, if you put an index directory up with everything under one parent folder, and grant read access + directory browsing to that folder path, then anyone can browse the entire file collection including sub folders under it. something like nbs-stl.com/tuningstuff/

 

Funny that Harley used an old version of Megasquirt / Tuner Studio to generate some of the screen shots in their Bosch document. Go figure...

LA Dog, have you seen http://www.nbs-stl.com/tuning/

Andy