How to find your injector dead time - Page 3 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


ECUs and Tuning Discuss Engine Management, Tuning, & Programming

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 06-09-2011, 10:50 AM   #41
Elite Member
iTrader: (1)
 
Join Date: Jun 2006
Location: Warrington/Birmingham
Posts: 2,658
Total Cats: 39
Default

Quote:
Originally Posted by Braineack View Post
here's the thing, all the deadtime code does is add that value to the end of your calculated pulsewitdh. if the code calculated 1.7ms and you have a deadtime of .8ms, it will fuel 2.5ms total.

Just pick a number and go with it. Tune the voltage correction curve to mirror that of the published rates and be done with it.
The problem with that is with large injectors and very small PW at idle, and small changes in temp and voltage mean your AFR's are way off.

See Jasons 1st post in this thread for why they're important.

I disagree totally with guessing the deadtime. getting it correct is key in achieving a consistent setup specifically at idle.
richyvrlimited is offline   Reply With Quote
Old 06-09-2011, 11:05 AM   #42
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,847
Total Cats: 1,788
Default

I didnt say guess, he has published rates.
Braineack is offline   Reply With Quote
Old 06-09-2011, 11:41 AM   #43
Elite Member
iTrader: (1)
 
Join Date: Jun 2006
Location: Warrington/Birmingham
Posts: 2,658
Total Cats: 39
Default

Quote:
Originally Posted by Braineack View Post
I didnt say guess, he has published rates.
"Just pick a number and go with it"

Aka guess :P
richyvrlimited is offline   Reply With Quote
Old 06-09-2011, 12:38 PM   #44
Elite Member
iTrader: (11)
 
Join Date: Feb 2009
Posts: 2,982
Total Cats: 10
Default

now ladies......
miatauser884 is offline   Reply With Quote
Old 06-09-2011, 02:20 PM   #45
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 407
Default

Quote:
Originally Posted by Braineack View Post
here's the thing, all the deadtime code does is add that value to the end of your calculated pulsewitdh. if the code calculated 1.7ms and you have a deadtime of .8ms, it will fuel 2.5ms total.
technically it's subtracted from the necessary pulsewidth...

if the ECU calculates you need 1.7ms, it will inject .9ms and let the dead time take care of itself. the injector will then be open for a total of 1.7ms.
y8s is offline   Reply With Quote
Old 06-09-2011, 06:12 PM   #46
Junior Member
 
Join Date: Jun 2007
Posts: 411
Total Cats: 0
Default

Quote:
Originally Posted by richyvrlimited View Post
"Just pick a number and go with it"

Aka guess :P
Well in fairness, he was referring to the previous post where there was a choice between 2 dead times for the RX-8 injectors

Back to the RX-8 injector- how do we get the battery correction curve right if there are no published rates?

Last edited by Greg G; 06-09-2011 at 07:07 PM.
Greg G is offline   Reply With Quote
Old 06-10-2011, 04:56 PM   #47
Senior Member
iTrader: (8)
 
Join Date: Jun 2010
Location: Navarre, FL
Posts: 1,127
Total Cats: 39
Default

I'm running 550cc RX7s, but didn't see any specific info on them, so I tested my own. Looks pretty close to Brain's (RX7 460s), but again, there's 2 different slopes so I'm not sure what to set. Depending on values I'm looking at, I can see anywhere between 1.0ms to 1.6ms.

To relate this to real world tests on my car...until today I have ran a dead time of 1.0. I needed values in the 60s in my VE table to get a 14.7 idle...always seemed high to me. Today, when changing dead time to 1.5ms, VE values in the 30s gives me the same idle. I'm thinking I ought to just keep my 1.5ms setting, but not sure...what do you all think?

Another question I have is.... the "open time" setting under "injector characteristics" in MS2- is that asking for the dead time at a certain voltage? Because the parameter after "open time" is the battery correction in ms/v. I understand that the dead time will change with voltage and that's the value we use to define the 'slope'...but what voltage is going to be referencing that from? 13.2V seems to be some sort of common value?

Name:  RX7550CC_DeadTime.png
Views: 335
Size:  17.7 KB

Last edited by aaronc7; 06-10-2011 at 07:26 PM.
aaronc7 is offline   Reply With Quote
Old 06-10-2011, 07:31 PM   #48
Senior Member
iTrader: (8)
 
Join Date: Jun 2010
Location: Navarre, FL
Posts: 1,127
Total Cats: 39
Default

just 'figured out ' that it does indeed reference that value @ 13.2V... (MS2)

http://msextra.com/forums/viewtopic....oltage#p285337

so, assuming I'm going to with 1.5ms dead time at idle @ 14 volts batt voltage, and .2ms/V slope in MS.... I should set about 1.3 in the "open time" field, correct?

Name:  TSInjectorChar.png
Views: 335
Size:  33.8 KB

edit: i got it backwards....probably a setting of 1.6ms and .1ms/v would get me 1.5ms dead time at 14V. is this the idea?

Last edited by aaronc7; 06-10-2011 at 09:39 PM.
aaronc7 is offline   Reply With Quote
Old 06-12-2011, 09:46 PM   #49
Elite Member
iTrader: (11)
 
Join Date: Feb 2009
Posts: 2,982
Total Cats: 10
Default

That injector may not have a .2 ms/V correction. For instance, my RC750 is .13 from 12 to 15V from 11v to 12v it's .16ms/V I'm using the .13 ms/V because it is in my useful range.
miatauser884 is offline   Reply With Quote
Old 06-13-2011, 12:30 AM   #50
Senior Member
iTrader: (8)
 
Join Date: Jun 2010
Location: Navarre, FL
Posts: 1,127
Total Cats: 39
Default

DIYPNP has a base map for a car with 460cc RX7 injectors... they used 1.2V and .1mv/S.

I ended up just going with those setting and moving on- close enough
aaronc7 is offline   Reply With Quote
Old 07-19-2011, 11:52 PM   #51
Junior Member
iTrader: (4)
 
Join Date: May 2009
Location: Athens GA
Posts: 434
Total Cats: 3
Default

Here is the plot for my RX8 Yellow injectors.

Measured dead time is 0.75ms.

redrider706 is offline   Reply With Quote
Old 07-20-2011, 03:07 AM   #52
Elite Member
Thread Starter
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

your data is too messy
JasonC SBB is offline   Reply With Quote
Old 07-20-2011, 12:32 PM   #53
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 407
Default

what's it mean if my AFR goes to 17:1 when my voltage drops from 14.2 to 12.5?
y8s is offline   Reply With Quote
Old 07-20-2011, 12:35 PM   #54
Elite Member
Thread Starter
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

voltage compensation is wrong. Does it to do instatnly then recover?
Sounds like more deadtime needs to be added for 12.5V.
JasonC SBB is offline   Reply With Quote
Old 09-25-2011, 12:01 AM   #55
Elite Member
iTrader: (11)
 
Join Date: Feb 2009
Posts: 2,982
Total Cats: 10
Default

I thought I would share some more of my data. I am using the published injector data, but never went back and collected any experimental data to compare. Here it is. The first graph is a large dataset. The calculated deadtime is very close to the theoretical for the battery voltage in which the data was collected. However ther is a very tight group of points that a y intercept of 1.1 fits rather nicely.

The lower graph has the excel calculated y intercept,a nd then a couple that I selected just to see how they fit. During the data collection the battery voltage held steady at 14.2V with the injector deadtime set to .734ms at 13.2v. Publish data would suggest a deadtime of .604 at 14.2V

Please post your opinions about what you see.

Should be using published data or experimental data?

miatauser884 is offline   Reply With Quote
Old 09-26-2011, 03:48 PM   #56
Elite Member
Thread Starter
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

Quote:
Originally Posted by djp0623 View Post

Eyeballing the *upper* graph above shows 3 major trendlines. You can't just take a single trendline from the above. You have to find out what is making the trendline change - e.g. did battery voltage change due to fans turning on, or was part of it after a hot restart, etc.

Having 3 different distinct trendlines is different than getting a single trace with a curve in it. In the latter case, you look at the trendline where accurate afr control is most critical - idle at min RPM with min loading (no fans, no ac, charged battery), in the region of about 15:1 afr.

How did you vary the AFR to generate the dataset in the upper plot?
JasonC SBB is offline   Reply With Quote
Old 09-26-2011, 07:17 PM   #57
Elite Member
iTrader: (11)
 
Join Date: Feb 2009
Posts: 2,982
Total Cats: 10
Default

Quote:
Originally Posted by JasonC SBB View Post
Eyeballing the *upper* graph above shows 3 major trendlines. You can't just take a single trendline from the above. You have to find out what is making the trendline change - e.g. did battery voltage change due to fans turning on, or was part of it after a hot restart, etc.

Having 3 different distinct trendlines is different than getting a single trace with a curve in it. In the latter case, you look at the trendline where accurate afr control is most critical - idle at min RPM with min loading (no fans, no ac, charged battery), in the region of about 15:1 afr.

How did you vary the AFR to generate the dataset in the upper plot?
The afr in the top graph ranges from 13.6-14.2 iirc. I believe the afr change is due to the change in AIT. What is a sufficient number of datapoints to plot. Obviously 60s as opposed to 10min of points will remove most affect of IAT change. I'll play with it again after I make some ecu changes.
miatauser884 is offline   Reply With Quote
Old 09-26-2011, 11:34 PM   #58
Elite Member
Thread Starter
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

How did you force the afr to change?
Is the plot of MAP/AFR?

I took a few minutes of logs where I raised and lowered inj dead-time.
JasonC SBB is offline   Reply With Quote
Old 09-27-2011, 12:06 AM   #59
Elite Member
iTrader: (11)
 
Join Date: Feb 2009
Posts: 2,982
Total Cats: 10
Default

I did take a log where I adjusted the pulsewidths, but I don't believe this this data was taken from that log. Adjusting the pulsewidth resulted in an idle of 17:1. I didn't think this was possible.

It's a graph of pw vs map/afr

I wonder if I used a log where I was adjusting the injection timing table. I'll take another one when I get my computer sorted.
miatauser884 is offline   Reply With Quote
Old 09-30-2011, 03:18 PM   #60
Elite Member
iTrader: (2)
 
triple88a's Avatar
 
Join Date: Apr 2006
Location: Chicago, IL
Posts: 9,131
Total Cats: 598
Default

Btw guys the dead times should not have a linear value...
triple88a is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Turbo 1995 Miata Low mileage Clean Tekel Cars for sale/trade 29 02-05-2016 05:16 PM
Miata Newbie hdizzle Meet and Greet 8 09-21-2015 11:08 AM
Interpreting Deatchwerks Dead Times from Battery Wizard compuw22c MEGAsquirt 0 09-14-2015 07:08 PM
VE values too low? compuw22c MEGAsquirt 4 09-12-2015 08:42 PM
First to get it out of the way main Meet and Greet 1 09-05-2015 01:39 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 03:46 AM.