It is currently Tue Nov 21, 2017 10:47 pm




Post new topic Reply to topic  [ 7 posts ] 
 Injector Latency and Dead Time tuning 
Author Message
Race Official
Race Official
User avatar

Joined: Sun Jan 11, 2004 10:38 am
Posts: 2198
Location: Penfield, NY
Post Injector Latency and Dead Time tuning
I am horrible at tuning. I get mental blocks when I don't understand why something works, which keeps me from accepting it as "how it is done".

I have a problem not understanding why an injector manufacturer would publish latency values on an injector, and then I ignore them to invent my own.

The process of dialing in injectors is completely reactionary based on watching fuel trims at idle and cruise. That act alone bothers me. I have been able to dial in my injectors to under a percent of deviation, watching these numbers. I still don't like it. I understand the general premise of how it came to be and why it should theoretically provide close enough measurements.

How would one measure the latency and dead time of an injector in a lab or testing scenario? If there is such a lab, I might send them some injectors, just to help me sleep at night.

Either that or I will setup a lab and offer a mail in service to test the values.

Stephen

_________________
2008 Evolution X GSR
One Lap of America Team Site http://onelap.rochesterdsm.org


Sat Oct 01, 2011 7:00 am
Profile
Wilson Performance
Wilson Performance
User avatar

Joined: Sun Mar 11, 2007 4:20 am
Posts: 542
Location: Rochester / Chili
Post Re: Injector Latency and Dead Time tuning
Can of worms alert....

Who gave you injector latency times with a set of injectors? It's heavily dependent so many things outside of an actual lab measurement. Just because the deadtime inserted into the ecu is correct doesn't mean the ECU can predict the non-linear flow of an injector at low flow rates, varying airflow readings, the slightest offset in your o2 sensor feedback, or any thing mechanically different than perfect.

The problem isn't the injector, i'm sure if you bench tested the response it would be perfect, it's everything else. Your using an o2 sensor as feedback on the accuracy of every control device and moving part in the engine. Which all happens to be interpreted by the ecu which was finely tuned by mitsubishi on a different injector. 1% is pretty damn good.

Work on an aftermarket ECU and injector offsets are about a 10 minute project.

_________________
Image


Mon Oct 03, 2011 9:17 am
Profile
Race Official
Race Official
User avatar

Joined: Sun Jan 11, 2004 10:38 am
Posts: 2198
Location: Penfield, NY
Post Injector Latency and Dead Time tuning
I don't mind a can of worms if it opens legit discussion.

Injector Dynamics publishes their dead times or latency values.

Stephen

_________________
2008 Evolution X GSR
One Lap of America Team Site http://onelap.rochesterdsm.org


Mon Oct 03, 2011 11:33 am
Profile
Race Official
Race Official
User avatar

Joined: Mon Jan 12, 2004 9:27 am
Posts: 1345
Location: Rochester, NY
Post Re: Injector Latency and Dead Time tuning
Here's a good example since I just went through it this morning and last night. The FIC injectors I just installed came with published latencies at certain voltages at certain pressures. Nice info to have but it's only a base line. I ended up a bit away from the published due to actual idle pressures, voltage incrementals, and engine state changes from the stock expectation. Anything that changes the VE of an engine should alter the consumable based on idle airflow and hence the feedback.

Setting idle trims is about a 10-20 minute job. Long term takes a bit longer on an Evo. Once you have the scaling down, you can tweak the maps.

I'm stick dickering with the scaling and latencies at this point but it's minor tweaks.

_________________
"A walking we will go, a walking we will go, hi ho the merry-0, a walking we will go."

- Sean Caron
2006 Graphite Grey Evolution IX


Mon Oct 03, 2011 1:20 pm
Profile
Wilson Performance
Wilson Performance
User avatar

Joined: Sun Mar 11, 2007 4:20 am
Posts: 542
Location: Rochester / Chili
Post Re: Injector Latency and Dead Time tuning
nrvous wrote:
I don't mind a can of worms if it opens legit discussion.

Injector Dynamics publishes their dead times or latency values.

Stephen


Was it Mitsubishi specific? I know he uses a Motec ecu with peak and hold drivers on his test bench, and actually uses gasoline, which is cool. But, If the generic latencies are based off that, its a big wrench in the equation - being that Mitsubishi uses plain old saturated drivers.

_________________
Image


Mon Oct 03, 2011 1:52 pm
Profile
Race Official
Race Official
User avatar

Joined: Sun Jan 11, 2004 10:38 am
Posts: 2198
Location: Penfield, NY
Post Re: Injector Latency and Dead Time tuning
obz wrote:
Was it Mitsubishi specific? I know he uses a Motec ecu with peak and hold drivers on his test bench, and actually uses gasoline, which is cool. But, If the generic latencies are based off that, its a big wrench in the equation - being that Mitsubishi uses plain old saturated drivers.


It is definitely not specific to Mitsubishi. They offer it up in a summary of overall settings. Then the offer application specific, catering to the Ford ECU for downloads.
http://www.injectordynamics.com/ID1000.html

I am too far away from understanding the difference in saturation drivers versus peak hold drivers and how to identify which is applicable. I may not need to understand the details, as long as I can appreciate the recognition of the application.

The latency of the injector should be the latency of the injector. It sounds like it is the equation of how the ECU interpolates that latency that changes from manufacturer to manufacturer.

Stephen

_________________
2008 Evolution X GSR
One Lap of America Team Site http://onelap.rochesterdsm.org


Mon Oct 03, 2011 2:40 pm
Profile
Wilson Performance
Wilson Performance
User avatar

Joined: Sun Mar 11, 2007 4:20 am
Posts: 542
Location: Rochester / Chili
Post Re: Injector Latency and Dead Time tuning
nrvous wrote:
obz wrote:

The latency of the injector should be the latency of the injector.

Stephen



As long as you apply the same amount of energy to the coil, volts &/or Current. You offer the same amount of resistance to the injector opening - fuel pressure, then yeah, sure.

assuming your injector flows the same as the test set....

I agree with your last statement more than anything, in that the control method you are using works, but is part of Mitsubishi's fueling logic and not tailored to aftermarket tuning.

But.... you've only got 2 things, so theres not a whole lot you can do other than play games until the car is happy. which sucks.

More advanced ECU's are using 3-dimensional latency mapping, in that you need a compensation for "deadtime" based on the commanded fuel pulse. They map the 3rd axis as target pulse width to be able to fully map the response of the injector in more that 1 spot on its flow curve.

With ecuflash you're simply guessing and checking the deadtime to fix one or two spots in the fuel map. Just my .02.

_________________
Image


Mon Oct 03, 2011 3:22 pm
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 7 posts ] 


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © phpBB Group.
Designed by Vjacheslav Trushkin for Free Forums/DivisionCore.