When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I had no idea Megasquirt did this automatically. I always assumed the >100% VE figures were "accurate" once rising fuel pressure was taken into account. I never really thought about it very hard beyond that TBQH.
Sorry if I came across as hostile above at some point, I absolutely did not mean to. I respect you as well and I value your input/experience, even if (especially if?) it conflicts with my own. I'm learning here
If everything is perfectly dialed, then logically, you are right. Empirically, from my experience, all my fuel maps end up with in-boost VE figures north of 100%VE. I set dead times per the manufacturer's suggestions depending on which injectors I'm using, so I would love to know why that is. There's also the oddity of all EV14 injectors seeming to want far more VE than a similarly-sized EV1 or EV6, and I would really love to know why that is as well.
Cool Bro.
I think that the increased VE is a direct result of the improved and more controlled turn on and turn off characteristics of the newer injectors. We aren't losing VE in the dead time, so it has to be made up with true VE, which is where it belongs. The flow rates are much more controlled as well.
it is impossible to get a perfectly accurate fueling equation with the limited number of, and quality of system parameters we have to work with. Making up some of the error in the VE table is to be expected.
Just got home, exhausted, non-stop work and tuning, haven't read through the thread yet (sorry), but here's a screenshot to get started
Take target 10.2 / 11.5 = .87
Take VE 108 * .87 = 94
This is at 180map which is 11 and change PSI. Disregard that it goes way rich up top, we literally just diagnosed a faulty fuel pump and replaced it hence the richness. At idle commanding 101VE it's within 5-7% EGO swing.
I first noticed fairly flat VE tables when Schuyler put in FF640’s or their equivalents. It was even more surprising to me at the time, as he is on a returnless system.
Extrapolating his table to a MAP referenced system could result in a upside down VE table.
However, I’m now on FF with referenced fueling, and I still had idling around 55 at a MAP of about 35, and go above 100 in boost.
I think there is something interesting here.
And yes, the fueling equation includes MAP as a factor.
I revised OP's map per the logs and I guess we will just press on until we figure this out. Will update once we make more progress.
I can certainly have him try a map with incorporate afr disabled, and I realize that it could be contributing to this, but I still find it hard to believe that is able to make the primary VE less at 11.5psi than it is at idle.
I don't think incorporate has anything to do with this. It looks to me like a hardware issue.
Thank you. I agree. But have no idea where to continue looking/testing/checking at this point.
As to the question about fuel pressure: OP tested it with a "fuel pressure tester" from the local auto parts store iirc. it could be off I guess, but it seems to be relatively close with the pressure's he's seeing. Would seeing 65psi fuel pressure at 11.5psi boost point to an overly.........sensitive?.........regulator? or one that's getting overwhelmed? but that still wouldn't explain why he actually needs MORE fuel at idle, where the regulator would be most overwhelmed
Test the voltage at the injector. Dead time is dominant at idle. The input to dead time is voltage. The voltage used in that correction is measured at the ECU. Any difference between the ECU voltage and the injector voltage will introduce error. Dead time is no longer dominant at higher load and rpm, so errors in dead time correction become minimized.
How would I test voltage at the injector? Have key on and shove a probe into the back of the connector? Or key on and unplug the injector and prove the pins that way?
An overwhelmed regulator will manifest as excessively low VE% at idle (regulator is unable to regulate accurately which raises FP at idle, therefore less injector is commanded). This is the opposite issue, no?
How would I test voltage at the injector? Have key on and shove a probe into the back of the connector? Or key on and unplug the injector and prove the pins that way?
you want the car running at idle, then yes, shove into back of connector, or use sharp probe and pierce the wire in the injector harness as clost to the injector as you can. Ideally the black wire is connected to SGND on the MS.
An overwhelmed regulator will manifest as excessively low VE% at idle (regulator is unable to regulate accurately which raises FP at idle, therefore less injector is commanded). This is the opposite issue, no?
Correct. It is opposite
Originally Posted by Ted75zcar
you want the car running at idle, then yes, shove into back of connector, or use sharp probe and pierce the wire in the injector harness as clost to the injector as you can. Ideally the black wire is connected to SGND on the MS.
Id carefully stick into connector. I’d advise against piercing any wires
still. algorithm is the same. MAP plays a big role in the fueling -- so even though at 100kPa we have 96%VE, it's double the PW than at idle with 101%VE.
even since we started using EV14 injectors I've noticed the trend of the fuel tables getting flatter and flatter -- with needing almost 30% more VE at idle in the VE table than with EV6 or EV1 injectors.
still. algorithm is the same. MAP plays a big role in the fueling -- so even though at 100kPa we have 96%VE, it's double the PW than at idle with 101%VE.
I'm not arguing with the math or logic of it, but dozens of other turbo Miata's with ID1000's, ID1300's, FF640's and on and on all completely different from this car.
It’s usually anywhere from 60 to 80 at idle which I am fine with and then well into the hundreds in boost whereas this thing is almost exactly opposite
Originally Posted by DNMakinson
Are you using CL Idle VE and thus the full VE map means nothing at idle?
05-07-2018, 10:33 PM
0
